Program plan for the Brayton Isotope Power System. Phase I. Design, fabrication and test of the Brayton Isotope Power System

International Nuclear Information System (INIS)

1975-01-01

Phase I of an overall program for the development of a 500 to 2000 W(e) (EOM), 7-y life, power system for space vehicles is discussed. The system uses a closed Brayton dynamic system to convert energy from an isotope heat source at a net efficiency greater than 25 percent. This first phase, a 35-month effort, is for the conceptual design of a 1300 W(e), 450 lb flight system and the design, fabrication, and test of a ground demonstration system. The flight system will use, for the baseline design, two of the multihundred-watt (MHW) heat sources being developed. The Ground Demonstration System will simulate, as closely as possible, the Brayton Isotope Power Flight System and will utilize components and technology being developed for the Mini-Brayton rotating unit, recuperator and heat source assembly, respectively. The Ground Demonstration System includes a performance test and a 1000-h endurance test

Potential application of Rankine and He-Brayton cycles to sodium fast reactors

International Nuclear Information System (INIS)

Perez-Pichel, G.D.; Linares, J.I.; Herranz, L.E.; Moratilla, B.Y.

2011-01-01

Highlights: → This paper has been focused on thermal efficiency of several Rankine and Brayton cycles for SFR. → A sub-critical Rankine configuration could reach a thermal efficiency higher than 43%. → It could be increased to almost 45% using super-critical configurations. → Brayton cycles thermal performance can be enhanced by adding a super-critical organic fluid Rankine cycle. → The moderate coolant temperature at the reactor makes Brayton configurations have poorer. - Abstract: Traditionally all the demos and/or prototypes of the sodium fast reactor (SFR) technology with power output, have used a steam sub-critical Rankine cycle. Sustainability requirement of Gen. IV reactors recommends exploring alternate power cycle configurations capable of reaching high thermal efficiency. By adopting the anticipated working parameters of next SFRs, this paper investigates the potential of some Rankine and He-Brayton layouts to reach thermal efficiencies as high as feasible, so that they could become alternates for SFR reactor balance of plant. The assessment has encompassed from sub-critical to super-critical Rankine cycles and combined cycles based on He-Brayton gas cycles of different complexity coupled to Organic Rankine Cycles. The sub-critical Rankine configuration reached at thermal efficiency higher than 43%, which has been shown to be a superior performance than any of the He-Brayton configurations analyzed. By adopting a super-critical Rankine arrangement, thermal efficiency would increase less than 1.5%. In short, according to the present study a sub-critical layout seems to be the most promising configuration for all those upcoming prototypes to be operated in the short term (10-15 years). The potential of super-critical CO 2 -Brayton cycles should be explored for future SFRs to be deployed in a longer run.

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

International Nuclear Information System (INIS)

Wang Hao; Liu Sanqiu

2008-01-01

An irreversible cycle model of magnetic Brayton refrigerators is established, in which the thermal resistance and irreversibility in the two adiabatic processes are taken into account. Expressions for several important performance parameters, such as the coefficient of performance, cooling rate and power input are derived. Moreover, the optimal performance parameters are obtained at the maximum coefficient of performance. The optimization region (or criteria) for an irreversible magnetic Brayton refrigerator is obtained. The results obtained here have general significance and will be helpful to understand deeply the performance of a magnetic Brayton refrigeration cycle

On the reversed Brayton cycle with high speed machinery

Energy Technology Data Exchange (ETDEWEB)

Backman, J.

1996-12-31

This work was carried out in the laboratory of Fluid Dynamics, at Lappeenranta University of Technology during the years 1991-1996. The research was a part of larger high speed technology development research. First, there was the idea of making high speed machinery applications with the Brayton cycle. There was a clear need to deepen the knowledge of the cycle itself and to make a new approach in the field of the research. Also, the removal of water from the humid air seemed very interesting. The goal of this work was to study methods of designing high speed machinery for the reversed Brayton cycle, from theoretical principles to practical applications. 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. A new calculation method for the Brayton cycle is developed. 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. Also, the influence of calculating the process with actual, achievable process equipment efficiencies is essential for the development of future machinery. The above theoretical calculations are confirmed with two different laboratory prototypes. (53 refs.)

On the reversed Brayton cycle with high speed machinery

Energy Technology Data Exchange (ETDEWEB)

Backman, J

1997-12-31

This work was carried out in the laboratory of Fluid Dynamics, at Lappeenranta University of Technology during the years 1991-1996. The research was a part of larger high speed technology development research. First, there was the idea of making high speed machinery applications with the Brayton cycle. There was a clear need to deepen the knowledge of the cycle itself and to make a new approach in the field of the research. Also, the removal of water from the humid air seemed very interesting. The goal of this work was to study methods of designing high speed machinery for the reversed Brayton cycle, from theoretical principles to practical applications. 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. A new calculation method for the Brayton cycle is developed. 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. Also, the influence of calculating the process with actual, achievable process equipment efficiencies is essential for the development of future machinery. The above theoretical calculations are confirmed with two different laboratory prototypes. (53 refs.)

Study of various Brayton cycle designs for small modular sodium-cooled fast reactor

International Nuclear Information System (INIS)

Ahn, Yoonhan; Lee, Jeong Ik

2014-01-01

Highlights: • Application of closed Brayton cycle for small and medium sized SFRs is reviewed. • S-CO 2 , helium and nitrogen cycle designs for small modular SFR applications are analyzed and compared in terms of cycle efficiency, component performance and physical size. • Several new layouts for each Brayton cycle are suggested to simplify the turbomachinery designs. • S-CO 2 cycle design shows the best efficiency and compact size compared to other Brayton cycles. - Abstract: Many previous sodium cooled fast reactors (SFRs) adopted steam Rankine cycle as the power conversion system. However, the concern of sodium water reaction has been one of the major design issues of a SFR system. As an alternative to the steam Rankine cycle, several closed Brayton cycles including supercritical CO 2 cycle, helium cycle and nitrogen cycle have been suggested recently. In this paper, these alternative gas Brayton cycles will be compared to each other in terms of cycle performance and physical size for small modular SFR application. Several new layouts are suggested for each fluid while considering the turbomachinery design and the total system volume

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.

Supercritical Carbon Dioxide Brayton Cycle Energy Conversion System

International Nuclear Information System (INIS)

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

2007-12-01

This report contains the description of the S-CO 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 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 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 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 2 boundary failure event, a computer was developed to simulate the complex thermodynamic behaviors coupled with the chemical reaction between liquid sodium and CO 2 gas. The long term behavior of a Na/CO 2 boundary failure event and its consequences which lead to a system pressure transient were evaluated

Potential impacts of Brayton and Stirling cycle engines

Science.gov (United States)

Heft, R. C.

1980-01-01

Two engine technologies (Brayton cycle and Stirling cycle) are examined for their potential economic impact and fuel utilization. An economic analysis of the expected response of buyers to the attributes of the alternative engines was performed. Hedonic coefficients for vehicle fuel efficiency, performance and size were estimated for domestic cars based upon historical data. The marketplace value of the fuel efficiency enhancement provided by Brayton or Stirling engines was estimated. Under the assumptions of 10 years for plant conversions and 1990 and 1995 as the introduction data for turbine and Stirling engines respectively, the comparative fuel savings and present value of the future savings in fuel costs were estimated.

Closed Brayton cycle power conversion systems for nuclear reactors :

Energy Technology Data Exchange (ETDEWEB)

Wright, Steven A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lipinski, Ronald J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Vernon, Milton E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sanchez, Travis [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

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

Combined Brayton-JT cycles with refrigerants for natural gas liquefaction

Science.gov (United States)

Chang, Ho-Myung; Park, Jae Hoon; Lee, Sanggyu; Choe, Kun Hyung

2012-06-01

Thermodynamic cycles for natural gas liquefaction with single-component refrigerants are investigated under a governmental project in Korea, aiming at new processes to meet the requirements on high efficiency, large capacity, and simple equipment. Based upon the optimization theory recently published by the present authors, it is proposed to replace the methane-JT cycle in conventional cascade process with a nitrogen-Brayton cycle. A variety of systems to combine nitrogen-Brayton, ethane-JT and propane-JT cycles are simulated with Aspen HYSYS and quantitatively compared in terms of thermodynamic efficiency, flow rate of refrigerants, and estimated size of heat exchangers. A specific Brayton-JT cycle is suggested with detailed thermodynamic data for further process development. The suggested cycle is expected to be more efficient and simpler than the existing cascade process, while still taking advantage of easy and robust operation with single-component refrigerants.

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

El conocimiento del ciclo del agua en el segundo ciclo de Educación Primaria

Directory of Open Access Journals (Sweden)

María Guerrero Valle

2017-07-01

Full Text Available El agua tiene una gran importancia e influencia en nuestras vidas y en nuestro planeta. En este trabajo se presenta una investigación sobre el conocimiento sobre el ciclo del agua en el segundo ciclo de la Educación Primaria. Para el estudio, se ha realizado en dos centros de Primaria un cuestionario sobre lluvia que recoge los conceptos claves para una comprensión básica del mecanismo de la lluvia como del ciclo del agua, junto con un dibujo sobre la lluvia. La investigación pone de manifiesto que el grado de conocimiento sobre el ciclo del agua de los estudiantes es alto, pero se trata de un conocimiento incompleto y, en algunas ocasiones, erróneo. Después de reflexionar sobre los resultados obtenidos, se propone la implicación educativa necesaria para mejorar dichos resultados.

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

International Nuclear Information System (INIS)

Bernardos, Eva; López, Ignacio; Rodríguez, Javier; Abánades, Alberto

2013-01-01

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

Buffer thermal energy storage for a solar Brayton engine

Science.gov (United States)

Strumpf, H. J.; Barr, K. P.

1981-01-01

A study has been completed on the application of latent-heat buffer thermal energy storage to a point-focusing solar receiver equipped with an air Brayton engine. To aid in the study, a computer program was written for complete transient/stead-state Brayton cycle performance. The results indicated that thermal storage can afford a significant decrease in the number of engine shutdowns as compared to operating without thermal storage. However, the number of shutdowns does not continuously decrease as the storage material weight increases. In fact, there appears to be an optimum weight for minimizing the number of shutdowns.

Nuclear Bi-Brayton system for aircraft propulsion

International Nuclear Information System (INIS)

Pierce, B.L.

1979-01-01

Recent studies have shown the desirability of new system concept for nuclear aircraft propulsion utilizing the Bi-Brayton system concept, permits coupling of a gas cooled reactor to the power transmission and conversion system in a manner such as to fulfill the safety criteria while eliminating the need for a high temperature intermediate heat exchanger or shaft penetrations of the containment vessel. This system has been shown to minimize the component development required and to allow reduction in total propulsion system weight. This paper presents a description of the system concept and the results of the definition and evaluation studies to date. Parametric and reference system definition studies have been performed. The closed-cycle Bi-Brayton system and component configurations and weight estimates have been derived. Parametric evaluation and cycle variation studies have been performed and interpreted. 7 refs

Brayton-Cycle Power-Conversion Unit Tested With Ion Thruster

Science.gov (United States)

Hervol, David S.

2005-01-01

Nuclear electric propulsion has been identified as an enabling technology for future NASA space science missions, such as the Jupiter Icy Moons Orbiter (JIMO) now under study. An important element of the nuclear electric propulsion spacecraft is the power conversion system, which converts the reactor heat to electrical power for use by the ion propulsion system and other spacecraft loads. The electrical integration of the power converter and ion thruster represents a key technical challenge in making nuclear electric propulsion technology possible. This technical hurdle was addressed extensively on December 1, 2003, when a closed- Brayton-cycle power-conversion unit was tested with a gridded ion thruster at the NASA Glenn Research Center. The test demonstrated end-to-end power throughput and marked the first-ever coupling of a Brayton turbo alternator and a gridded ion thruster, both of which are candidates for use on JIMO-type missions. The testing was conducted at Glenn's Vacuum Facility 6, where the Brayton unit was installed in the 3-m-diameter vacuum test port and the ion thruster was installed in the 7.6-m-diameter main chamber.

Las entidades financieras a lo largo del ciclo de negocios: ¿Es el ciclo financiero sensible al ciclo de negocios?

OpenAIRE

Fernando Arias Rodríguez; Celina Gaitán Maldonado; Johanna López Velandia

2014-01-01

A partir de estados financieros de bancos y entidades asociadas se propone una cronología del ciclo financiero para Colombia, desde 1990 hasta mediados del año 2013, y se evalúa su interacción con el ciclo de negocios propuesto por Alfonso et al. (2012). Se usan dos acercamientos: el primero basado en reglas (Bry y Boschan, (1971) e Índices de Difusión) y el segundo fundamentado en la información contenida en los datos (Novelty Detection). Se encuentra evidencia que apoya la idea de una sincr...

Effects of hysteresis and Brayton cycle constraints on magnetocaloric refrigerant performance

Science.gov (United States)

Brown, T. D.; Buffington, T.; Shamberger, P. J.

2018-05-01

Despite promising proofs of concept, system-level implementation of magnetic refrigeration has been critically limited by history-dependent refrigerant losses that interact with governing thermodynamic cycles to adversely impact refrigeration performance. Future development demands a more detailed understanding of how hysteresis limits performance, and of how different types of cycles can mitigate these limitations, but without the extreme cost of experimental realization. Here, the utility of Brayton cycles for magnetic refrigeration is investigated via direct simulation, using a combined thermodynamic-hysteresis modeling framework to compute the path-dependent magnetization and entropy of a model alloy for a variety of feasible Brayton cycles between 0-1.5 T and 0-5 T. By simultaneously varying the model alloy's hysteresis properties and applying extensions of the thermodynamic laws to non-equilibrium systems, heat transfers and efficiencies are quantified throughout the space of hystereses and Brayton cycles and then compared with a previous investigation using Ericsson cycles. It is found that (1) hysteresis losses remain a critical obstacle to magnetic refrigeration implementation, with efficiencies >80% in the model system requiring hysteresis refrigerant transformation temperatures at the relevant fields; (3) for a given hysteresis and field constraint, Brayton and Ericsson-type cycles generate similar efficiencies; for a given temperature span, Ericsson cycles lift more heat per cycle, with the difference decreasing with the refrigerant heat capacity outside the phase transformation region.

Power conversion systems based on Brayton cycles for fusion reactors

International Nuclear Information System (INIS)

Linares, J.I.; Herranz, L.E.; Moratilla, B.Y.; Serrano, I.P.

2011-01-01

This paper investigates Brayton power cycles for fusion reactors. Two working fluids have been explored: helium in classical configurations and CO 2 in recompression layouts (Feher cycle). Typical recuperator arrangements in both cycles have been strongly constrained by low temperature of some of the energy thermal sources from the reactor. This limitation has been overcome in two ways: with a combined architecture and with dual cycles. Combined architecture couples the Brayton cycle with a Rankine one capable of taking advantage of the thermal energy content of the working fluid after exiting the turbine stage (iso-butane and steam fitted best the conditions of the He and CO 2 cycles, respectively). Dual cycles set a specific Rankine cycle to exploit the lowest quality thermal energy source, allowing usual recuperator arrangements in the Brayton cycle. The results of the analyses indicate that dual cycles could reach thermal efficiencies around 42.8% when using helium, whereas thermal performance might be even better (46.7%), if a combined CO 2 -H 2 O cycle was set.

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

International Nuclear Information System (INIS)

Halimi, Burhanuddin; Suh, Kune Y.

2012-01-01

Highlights: ► Computational analysis of S-CO 2 Brayton cycle power conversion system. ► Validation of numerical model with literature data. ► Recompression S-CO 2 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-CO 2 ) 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-CO 2 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.

Dry Air Cooler Modeling for Supercritical Carbon Dioxide Brayton Cycle Analysis

Energy Technology Data Exchange (ETDEWEB)

Moisseytsev, A. [Argonne National Lab. (ANL), Argonne, IL (United States); Sienicki, J. J. [Argonne National Lab. (ANL), Argonne, IL (United States); Lv, Q. [Argonne National Lab. (ANL), Argonne, IL (United States)

2016-07-28

Modeling for commercially available and cost effective dry air coolers such as those manufactured by Harsco Industries has been implemented in the Argonne National Laboratory Plant Dynamics Code for system level dynamic analysis of supercritical carbon dioxide (sCO₂) Brayton cycles. The modeling can now be utilized to optimize and simulate sCO₂ Brayton cycles with dry air cooling whereby heat is rejected directly to the atmospheric heat sink without the need for cooling towers that require makeup water for evaporative losses. It has sometimes been stated that a benefit of the sCO₂ Brayton cycle is that it enables dry air cooling implying that the Rankine steam cycle does not. A preliminary and simple examination of a Rankine superheated steam cycle and an air-cooled condenser indicates that dry air cooling can be utilized with both cycles provided that the cycle conditions are selected appropriately

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

International Nuclear Information System (INIS)

M Postlehwait; P DiLorenzo; S Belanger; J Ashcroft

2005-01-01

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

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.

Rankine-Brayton engine powered solar thermal aircraft

Science.gov (United States)

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.

Rankline-Brayton engine powered solar thermal aircraft

Science.gov (United States)

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.

Inserción de prótesis metálicas autoexpandibles totalmente recubiertas en patología biliar benigna

Directory of Open Access Journals (Sweden)

Mariana Omodeo

Full Text Available RESUMEN Introducción: las enfermedades biliares benignas se han tratado, tradicionalmente, mediante la colocación de prótesis plásticas. Sin embargo, en la actualidad, las prótesis metálicas autoexpandibles totalmente recubiertas están ganando aceptación para el tratamiento de dichas patologías. Objetivo: evaluar la eficacia y las complicaciones de la inserción endoscópica temporal de prótesis metálicas totalmente recubiertas para el tratamiento de patologías biliares benignas. Materiales y métodos: estudio retrospectivo y observacional realizado a partir de una base de datos prospectiva en un centro de tercer nivel entre marzo de 2012 y mayo de 2016. Se incluyeron pacientes a los que se les colocó una prótesis metálica totalmente recubierta por patología benigna de la vía biliar. Se documentaron las indicaciones, las tasas de resolución, las de éxito técnico y los eventos adversos. Resultados: se incluyeron 31 pacientes a los que se insertaron 34 prótesis. Las indicaciones fueron las siguientes: 8 (25% estenosis biliares poscolecistectomía, 11 (31% coledocolitiasis de gran tamaño o múltiple, 3 (8,3% fístulas biliares, 2 (6% estenosis postrasplante hepático, 3 (8,3% estenosis papilares, 2 (6% perforaciones y 2 (6% sangrados. La tasa de éxito global de resolución de la patológica fue del 88%: 87,5% (7/8 en estenosis poscolecistectomía, 73% (8/11 en litiasis gigante, y 100% en el resto de las indicaciones. Se retiraron mediante endoscopia 33 de las 34 tras un promedio de 133 días (rango 10-180 días. No se registraron complicaciones. Conclusión: las prótesis metálicas autoexpandibles totalmente recubiertas son una alternativa efectiva y segura en la resolución de patologías biliares benignas.

Corrosion of Structural Materials for Advanced Supercritical Carbon- Dioxide Brayton Cycle

Energy Technology Data Exchange (ETDEWEB)

Sridharan, Kumar [Univ. of Wisconsin, Madison, WI (United States)

2017-05-13

The supercritical carbon-dioxide (referred to as SC-CO₂ hereon) Brayton cycle is being considered for power conversion systems for a number of nuclear reactor concepts, including the sodium fast reactor (SFR), fluoride saltcooled high temperature reactor (FHR), and high temperature gas reactor (HTGR), and several types of small modular reactors (SMR). The SC-CO₂ direct cycle gas fast reactor has also been recently proposed. The SC-CO₂ Brayton cycle (discussed in Chapter 1) provides higher efficiencies compared to the Rankine steam cycle due to less compression work stemming from higher SC-CO₂ densities, and allows for smaller components size, fewer components, and simpler cycle layout. For example, in the case of a SFR using a SC-CO₂ Brayton cycle instead of a steam cycle would also eliminate the possibility of sodium-water interactions. The SC-CO₂ cycle has a higher efficiency than the helium Brayton cycle, with the additional advantage of being able to operate at lower temperatures and higher pressures. In general, the SC-CO₂ Brayton cycle is well-suited for any type of nuclear reactor (including SMR) with core outlet temperature above ~ 500°C in either direct or indirect versions. In all the above applications, materials corrosion in high temperature SC-CO₂ is an important consideration, given their expected lifetimes of 20 years or longer. Our discussions with National Laboratories and private industry early on in this project indicated materials corrosion to be one of the significant gaps in the implementation of SC-CO₂ Brayton cycle. Corrosion can lead to a loss of effective load-bearing wall thickness of a component and can potentially lead to the generation of oxide particulate debris which can lead to three-body wear in turbomachinery components. Another environmental degradation effect that is rather unique to CO₂ environment is the possibility

Performance evaluation and parametric choice criteria of a Brayton pumped thermal electricity storage system

International Nuclear Information System (INIS)

Guo, Juncheng; Cai, Ling; Chen, Jincan; Zhou, Yinghui

2016-01-01

A more realistic thermodynamic model of the pumped thermal electricity storage (PTES) system consisting of a Brayton cycle and a reverse Brayton cycle is proposed, where the internal and external irreversible losses are took into account and several important controlling parameters, e.g., the pressure ratio and heat flows of the two isobaric processes in the Brayton cycle, are introduced. Analytic expressions for the round trip efficiency and power output of the PTES system are derived. The general performance characteristics of the PTES system are revealed. The optimal relationship between the round trip efficiency and the power output is obtained. The influences of some important controlling parameters on the performance characteristics of the PTES system are discussed and the optimally operating regions of these parameters are determined. - Highlights: • A cycle model of the Brayton pumped thermal electricity storage system is proposed. • Internal and external irreversible losses are considered. • Maximum power output and efficiency of the system are calculated. • Optimum performance characteristics of the system are revealed. • Rational ranges of key controlling parameters are determined.

Experimental Results From a 2kW Brayton Power Conversion Unit

Science.gov (United States)

Hervol, David; Mason, Lee; Birchenough, Arthur

2003-01-01

This paper presents experimental test results from operation of a 2 kWe Brayton power conversion unit. The Brayton converter was developed for a solar dynamic power system flight experiment planned for the Mir Space Station in 1997. The flight experiment was cancelled, but the converter was tested at Glenn Research Center as part of the Solar Dynamic Ground Test Demonstration system which included a solar concentrator, heat receiver, and space radiator. In preparation for the current testing, the heat receiver was removed and replaced with an electrical resistance heater, simulating the thermal input of a steady-state nuclear source. The converter was operated over a full range of thermal input power levels and rotor speeds to generate an overall performance map. The converter unit will serve as the centerpiece of a Nuclear Electric Propulsion Testbed at Glenn. Future potential uses for the Testbed include high voltage electrical controller development, integrated electric thruster testing and advanced radiator demonstration testing to help guide high power Brayton technology development for Nuclear Electric Propulsion (NEP).

Task Order 20: Supercritical Carbon Dioxide Brayton Cycle Energy Conversion Study

Energy Technology Data Exchange (ETDEWEB)

Murray, Paul [AREVA Federal Services, LLC, Charlotte, NC (United States); Lindsay, Edward [AREVA Federal Services, LLC, Charlotte, NC (United States); McDowell, Michael [AREVA Federal Services, LLC, Charlotte, NC (United States); Huang, Megan [AREVA Federal Services, LLC, Charlotte, NC (United States)

2015-04-23

AREVA Inc. developed this study for the US Department of Energy (DOE) office of Nuclear Energy (NE) in accordance with Task Order 20 Statement of Work (SOW) covering research and development activities for the Supercritical Carbon Dioxide (sCO2) Brayton Cycle energy conversion. The study addresses the conversion of sCO2 heat energy to electrical output by use of a Brayton Cycle system and focuses on the potential of a net efficiency increase via cycle recuperation and recompression stages. The study also addresses issues and study needed to advance development and implementation of a 10 MWe sCO2 demonstration project.

Preliminary design of S-CO{sub 2} Brayton cycle for APR-1400 with power generation and desalination process

Energy Technology Data Exchange (ETDEWEB)

Bae, Seong Jun; Lee, Won Woong; Jeong, Yong Hoon; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of); Yoon, Ho Joon [KUSTAR, Abu Dhabi (United Arab Emirates)

2015-10-15

This study was conducted to explore the capabilities of the S-CO{sub 2} Brayton cycle for a cogeneration system for APR-1400 application. Three concepts of the S-CO{sub 2} simple recuperated co-generation cycle were designed. A supercritical CO{sub 2} (S-CO{sub 2}) Brayton cycle is recently receiving significant attention as a promising power conversion system in wide range of energy applications due to its high efficiency and compact footprint. The main reason why the S-CO{sub 2} Brayton cycle has these advantages is that the compressor operates near the critical point of CO{sub 2} (30.98 .deg. C, 7.38MPa) to reduce the compression work significantly compared to the other Brayton cycles. In this study, the concept of replacing the entire steam cycle of APR-1400 with the S-CO{sub 2} Brayton cycle is evaluated. The power generation purpose S-CO{sub 2} Brayton cycles are redesigned to generate power and provide heat to the desalination system at the same time. The performance of these newly suggested cycles are evaluated in this paper. The target was to deliver 147MW heat to the desalination process. The thermal efficiencies of the three concepts are not significantly different, but the 3{sup rd} concept is relatively simpler than other cycles because only an additional heat exchanger is required. Although the 2{sup nd} concept is relatively complicated in comparison to other concepts, the temperatures at the inlet and outlet of the DHX are higher than that of the others. As shown in the results, the S-CO{sub 2} Brayton cycles are not easy to outperform the steam cycle with very simple layout and general design points under APR-1400 operating condition. However, this study shows that the S-CO{sub 2} Brayton cycles can be designed as a co-generation cycle while producing the target desalination heat with a simple configuration. In addition, it was also found that the S-CO{sub 2} Brayton cycle can achieve higher cycle thermal efficiency than the steam power cycle under

Thermodynamic Analysis of an Irreversible Maisotsenko Reciprocating Brayton Cycle

Directory of Open Access Journals (Sweden)

Fuli Zhu

2018-03-01

Full Text Available An irreversible Maisotsenko reciprocating Brayton cycle (MRBC model is established using the finite time thermodynamic (FTT theory and taking the heat transfer loss (HTL, piston friction loss (PFL, and internal irreversible losses (IILs into consideration in this paper. A calculation flowchart of the power output (P and efficiency (η of the cycle is provided, and the effects of the mass flow rate (MFR of the injection of water to the cycle and some other design parameters on the performance of cycle are analyzed by detailed numerical examples. Furthermore, the superiority of irreversible MRBC is verified as the cycle and is compared with the traditional irreversible reciprocating Brayton cycle (RBC. The results can provide certain theoretical guiding significance for the optimal design of practical Maisotsenko reciprocating gas turbine plants.

Enhancing power cycle efficiency for a supercritical Brayton cycle power system using tunable supercritical gas mixtures

Science.gov (United States)

Wright, Steven A.; Pickard, Paul S.; Vernon, Milton E.; Radel, Ross F.

2017-08-29

Various technologies pertaining to tuning composition of a fluid mixture in a supercritical Brayton cycle power generation system are described herein. Compounds, such as Alkanes, are selectively added or removed from an operating fluid of the supercritical Brayton cycle power generation system to cause the critical temperature of the fluid to move up or down, depending upon environmental conditions. As efficiency of the supercritical Brayton cycle power generation system is substantially optimized when heat is rejected near the critical temperature of the fluid, dynamically modifying the critical temperature of the fluid based upon sensed environmental conditions improves efficiency of such a system.

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

International Nuclear Information System (INIS)

Kim, T. W.; Kim, N. H.; Suh, K. Y.

2007-01-01

Supercritical carbon dioxide (SCO 2 ) 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 SCO 2 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 SCO 2 Brayton cycle needing less room relative to the Rankine steam cycle because of its smaller components. The SCO 2 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 SCO 2 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 SCO 2 going out from the low temperature recuperator. Development of Modular Optimized Brayton Integral System (MOBIS) is being devised as the SCO 2 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 SCO 2 turbine. Liquid-metal Energy Exchanger Integral System (LEXIS) serves to couple BORIS and MOBIS. LEXIS comprises Physical Aspect Thermal Operation System (PATOS) for SCO 2 thermal hydraulic characteristics, Shell-and-tube Overall Layout Optimization Study (SOLOS) for shell-and-tube heat exchanger, Printed

Brayton Isotope Power System (BIPS) facility specification

International Nuclear Information System (INIS)

1976-01-01

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

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.

Test Results from a Direct Drive Gas Reactor Simulator Coupled to a Brayton Power Conversion Unit

Science.gov (United States)

Hervol, David S.; Briggs, Maxwell H.; Owen, Albert K.; Bragg-Sitton, Shannon M.; Godfroy, Thomas J.

2010-01-01

Component level testing of power conversion units proposed for use in fission surface power systems has typically been done using relatively simple electric heaters for thermal input. These heaters do not adequately represent the geometry or response of proposed reactors. As testing of fission surface power systems transitions from the component level to the system level it becomes necessary to more accurately replicate these reactors using reactor simulators. The Direct Drive Gas-Brayton Power Conversion Unit test activity at the NASA Glenn Research Center integrates a reactor simulator with an existing Brayton test rig. The response of the reactor simulator to a change in Brayton shaft speed is shown as well as the response of the Brayton to an insertion of reactivity, corresponding to a drum reconfiguration. The lessons learned from these tests can be used to improve the design of future reactor simulators which can be used in system level fission surface power tests.

Supercritical CO2 Brayton Cycle Energy Conversion System Coupled with SFR

International Nuclear Information System (INIS)

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

2008-12-01

This report contains the description of the S-CO 2 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-CO 2 Brayton cycle energy conversion system was constructed for the KALIMER-600. Computer codes were developed to analysis for the S-CO 2 turbomachinery. Based on the design codes, the design parameters were prepared to configure the KALIMER-600 S-CO 2 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-CO 2 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 CO 2 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-CO 2 boundary failure event, a computer was developed to simulate the complex thermodynamic behaviors coupled with the chemical reaction between liquid sodium and CO 2 gas. The long term behavior of a Na-CO 2 boundary failure event and its consequences which lead to a system pressure transient were evaluated

Brayton Cycle Numerical Modeling using the RELAP5-3D code, version 4.3.4

Energy Technology Data Exchange (ETDEWEB)

Longhini, Eduardo P.; Lobo, Paulo D.C.; Guimarães, Lamartine N.F.; Filho, Francisco A.B.; Ribeiro, Guilherme B., E-mail: edu_longhini@yahoo.com.br [Instituto de Estudos Avançados (IEAv), São José dos Campos, SP (Brazil). Divisão de Energia Nuclear

2017-07-01

This work contributes to enable and develop technologies to mount fast micro reactors, to generate heat and electric energy, for the purpose to warm and to supply electrically spacecraft equipment and, also, the production of nuclear space propulsion effect. So, for this purpose, the Brayton Cycle demonstrates to be an optimum approach for space nuclear power. The Brayton thermal cycle gas has as characteristic to be a closed cycle, with two adiabatic processes and two isobaric processes. The components performing the cycle's processes are compressor, turbine, heat source, cold source and recuperator. Therefore, the working fluid's mass flow runs the thermal cycle that converts thermal energy into electrical energy, able to use in spaces and land devices. The objective is numerically to model the Brayton thermal cycle gas on nominal operation with one turbomachine composed for a radial-inflow compressor and turbine of a 40.8 kWe Brayton Rotating Unit (BRU). The Brayton cycle numerical modeling is being performed with the program RELAP5-3D, version 4.3.4. The nominal operation uses as working fluid a mixture 40 g/mole He-Xe with a flow rate of 1.85 kg/s, shaft rotational speed of 45 krpm, compressor and turbine inlet temperature of 400 K and 1149 K, respectively, and compressor exit pressure 0.931 MPa. Then, the aim is to get physical corresponding data to operate each cycle component and the general cycle on this nominal operation. (author)

Brayton Cycle Numerical Modeling using the RELAP5-3D code, version 4.3.4

International Nuclear Information System (INIS)

Longhini, Eduardo P.; Lobo, Paulo D.C.; Guimarães, Lamartine N.F.; Filho, Francisco A.B.; Ribeiro, Guilherme B.

2017-01-01

This work contributes to enable and develop technologies to mount fast micro reactors, to generate heat and electric energy, for the purpose to warm and to supply electrically spacecraft equipment and, also, the production of nuclear space propulsion effect. So, for this purpose, the Brayton Cycle demonstrates to be an optimum approach for space nuclear power. The Brayton thermal cycle gas has as characteristic to be a closed cycle, with two adiabatic processes and two isobaric processes. The components performing the cycle's processes are compressor, turbine, heat source, cold source and recuperator. Therefore, the working fluid's mass flow runs the thermal cycle that converts thermal energy into electrical energy, able to use in spaces and land devices. The objective is numerically to model the Brayton thermal cycle gas on nominal operation with one turbomachine composed for a radial-inflow compressor and turbine of a 40.8 kWe Brayton Rotating Unit (BRU). The Brayton cycle numerical modeling is being performed with the program RELAP5-3D, version 4.3.4. The nominal operation uses as working fluid a mixture 40 g/mole He-Xe with a flow rate of 1.85 kg/s, shaft rotational speed of 45 krpm, compressor and turbine inlet temperature of 400 K and 1149 K, respectively, and compressor exit pressure 0.931 MPa. Then, the aim is to get physical corresponding data to operate each cycle component and the general cycle on this nominal operation. (author)

Brayton Power Conversion Unit Tested: Provides a Path to Future High-Power Electric Propulsion Missions

Science.gov (United States)

Mason, Lee S.

2003-01-01

Closed-Brayton-cycle conversion technology has been identified as an excellent candidate for nuclear electric propulsion (NEP) power conversion systems. Advantages include high efficiency, long life, and high power density for power levels from about 10 kWe to 1 MWe, and beyond. An additional benefit for Brayton is the potential for the alternator to deliver very high voltage as required by the electric thrusters, minimizing the mass and power losses associated with the power management and distribution (PMAD). To accelerate Brayton technology development for NEP, the NASA Glenn Research Center is developing a low-power NEP power systems testbed that utilizes an existing 2- kWe Brayton power conversion unit (PCU) from previous solar dynamic technology efforts. The PCU includes a turboalternator, a recuperator, and a gas cooler connected by gas ducts. The rotating assembly is supported by gas foil bearings and consists of a turbine, a compressor, a thrust rotor, and an alternator on a single shaft. The alternator produces alternating-current power that is rectified to 120-V direct-current power by the PMAD unit. The NEP power systems testbed will be utilized to conduct future investigations of operational control methods, high-voltage PMAD, electric thruster interactions, and advanced heat rejection techniques. The PCU was tested in Glenn s Vacuum Facility 6. The Brayton PCU was modified from its original solar dynamic configuration by the removal of the heat receiver and retrofitting of the electrical resistance gas heater to simulate the thermal input of a steady-state nuclear source. Then, the Brayton PCU was installed in the 3-m test port of Vacuum Facility 6, as shown. A series of tests were performed between June and August of 2002 that resulted in a total PCU operational time of about 24 hr. An initial test sequence on June 17 determined that the reconfigured unit was fully operational. Ensuing tests provided the operational data needed to characterize PCU

Buffer thermal energy storage for an air Brayton solar engine

Science.gov (United States)

Strumpf, H. J.; Barr, K. P.

1981-01-01

The application of latent-heat buffer thermal energy storage to a point-focusing solar receiver equipped with an air Brayton engine was studied. To demonstrate the effect of buffer thermal energy storage on engine operation, a computer program was written which models the recuperator, receiver, and thermal storage device as finite-element thermal masses. Actual operating or predicted performance data are used for all components, including the rotating equipment. Based on insolation input and a specified control scheme, the program predicts the Brayton engine operation, including flows, temperatures, and pressures for the various components, along with the engine output power. An economic parametric study indicates that the economic viability of buffer thermal energy storage is largely a function of the achievable engine life.

Brayton cycle space power systems

International Nuclear Information System (INIS)

Pietsch, A.; Trimble, S.W.; Harper, A.D.

1985-01-01

The latest accomplishments in the design and development of the Brayton Isotope Power System (BIPS) for space applications are described, together with a reexamination of the design/cost tradeoffs with respect to current economic parameters and technology status. The results of tests performed on a ground test version of the flight configuration, the workhorse loop, were used to confirm the performance projections made for the flight system. The results of cost-model analysis indicate that the use of the highest attainable power conversion system efficiency will yield the most cost-effective systems. 13 references

Performance analysis of different working gases for concentrated solar gas engines: Stirling & Brayton

International Nuclear Information System (INIS)

Sharaf Eldean, Mohamed A.; Rafi, Khwaja M.; Soliman, A.M.

2017-01-01

Highlights: • Different working gases are used to power on Concentrated Solar Gas Engines. • Gases are used to increase the system efficiency. • Specific heat capacity is considered a vital role for the comparison. • Brayton engine resulted higher design limits. • CO 2 is favorable as a working gas more than C 2 H 2 . - Abstract: This article presents a performance study of using different working fluids (gases) to power on Concentrated Solar Gas Engine (CSGE-Stirling and/or Brayton). Different working gases such as Monatomic (five types), Diatomic (three types) and Polyatomic (four types) are used in this investigation. The survey purported to increase the solar gas engine efficiency hence; decreasing the price of the output power. The effect of using different working gases is noticed on the engine volume, dish area, total plant area, efficiency, compression and pressure ratios thence; the Total Plant Cost (TPC, $). The results reveal that the top cycle temperature effect is reflected on the cycle by increasing the total plant efficiency (2–10%) for Brayton operational case and 5–25% for Stirling operational case. Moreover; Brayton engine resulted higher design limits against the Stirling related to total plant area, m 2 and TPC, $ while generating 1–100 MW e as an economic case study plant. C 2 H 2 achieved remarkable results however, CO 2 is considered for both cycles operation putting in consideration the gas flammability and safety issues.

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.

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.

Digital computer study of nuclear reactor thermal transients during startup of 60-kWe Brayton power conversion system

Science.gov (United States)

Jefferies, K. S.; Tew, R. C.

1974-01-01

A digital computer study was made of reactor thermal transients during startup of the Brayton power conversion loop of a 60-kWe reactor Brayton power system. A startup procedure requiring the least Brayton system complication was tried first; this procedure caused violations of design limits on key reactor variables. Several modifications of this procedure were then found which caused no design limit violations. These modifications involved: (1) using a slower rate of increase in gas flow; (2) increasing the initial reactor power level to make the reactor respond faster; and (3) appropriate reactor control drum manipulation during the startup transient.

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

International Nuclear Information System (INIS)

Seo, Seok Bin; Seo, Han; Bang, In Cheol

2014-01-01

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 CO 2 (S-CO 2 ). However, S-CO 2 still has potential for reaction with sodium. CO 2 -sodium reaction produces solid product, which has possibility to have an auto ignition reaction around 600 .deg. C. Thus, instead of S-CO 2 , 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

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

International Nuclear Information System (INIS)

Ashe, T.L.; Baggenstoss, W.G.; Bons, R.

1990-01-01

Extra-terrestrial exploration and development missions of the next century will require reliable, low-mass power generation modules of 100 kW e 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

Improvement of supercritical CO2 Brayton cycle using binary gas mixture

International Nuclear Information System (INIS)

Jeong, Woo Seok

2011-02-01

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-CO 2 cycle) as a working fluid can be an alternative approach. The S-CO 2 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 CO 2 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 CO 2 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 CO 2 . The direction and range of the CO 2 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: CO 2 was mixed with N 2 , O 2 , He, Ar and Xe. To evaluate the effect of shifting the critical point and changes in the properties of the S-CO 2 Brayton cycle, a supercritical Brayton cycle analysis code connected with the REFPROP program from the NIST was developed. The developed code is for evaluating

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

International Nuclear Information System (INIS)

Zhang, Yu; Li, Qiang; Wu, Jihao; Li, Qing; Lu, Wenhai; Xiong, Lianyou; Liu, Liqiang; Xu, Xiangdong; Sun, Lijia; Sun, Yu; Xie, Xiujuan; Wang, Bingming; Qiu, Yinan; Zhang, Peng

2015-01-01

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

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

International Nuclear Information System (INIS)

Miller, L.G.

1976-01-01

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)

Cascaded recompression closed brayton cycle system

Energy Technology Data Exchange (ETDEWEB)

Pasch, James J.

2018-01-02

The present disclosure is directed to a cascaded recompression closed Brayton cycle (CRCBC) system and method of operation thereof, where the CRCBC system includes a compressor for compressing the system fluid, a separator for generating fluid feed streams for each of the system's turbines, and separate segments of a heater that heat the fluid feed streams to different feed temperatures for the system's turbines. Fluid exiting each turbine is used to preheat the fluid to the turbine. In an embodiment, the amount of heat extracted is determined by operational costs.

Cascaded recompression closed brayton cycle system

Science.gov (United States)

Pasch, James J.

2018-01-02

The present disclosure is directed to a cascaded recompression closed Brayton cycle (CRCBC) system and method of operation thereof, where the CRCBC system includes a compressor for compressing the system fluid, a separator for generating fluid feed streams for each of the system's turbines, and separate segments of a heater that heat the fluid feed streams to different feed temperatures for the system's turbines. Fluid exiting each turbine is used to preheat the fluid to the turbine. In an embodiment, the amount of heat extracted is determined by operational costs.

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.

Impact of closed Brayton cycle test results on gas cooled reactor operation and safety

International Nuclear Information System (INIS)

Wright, St.A.; Pickard, P.S.

2007-01-01

This report summarizes the measurements and model predictions for a series of tests supported by the U.S. Department of Energy that were performed using the recently constructed Sandia Brayton Loop (SBL-30). From the test results we have developed steady-state power operating curves, controls methodologies, and transient data for normal and off-normal behavior, such as loss of load events, and for decay heat removal conditions after shutdown. These tests and models show that because the turbomachinery operates off of the temperature difference (between the heat source and the heat sink), that the turbomachinery can continue to operate (off of sensible heat) for long periods of time without auxiliary power. For our test hardware, operations up to one hour have been observed. This effect can provide significant operations and safety benefits for nuclear reactors that are coupled to a Brayton cycles because the operating turbomachinery continues to provide cooling to the reactor. These capabilities mean that the decay-heat removal can be accommodated by properly managing the electrical power produced by the generator/alternator. In some conditions, it may even be possible to produce sufficient power to continue operating auxiliary systems including the waste heat circulatory system. In addition, the Brayton plant impacts the consequences of off-normal and accident events including loss of load and loss of on-site power. We have observed that for a loss of load or a loss of on-site power event, with a reactor scram, the transient consists initially of a turbomachinery speed increase to a new stable operating point. Because the turbomachinery is still spinning, the reactor is still being cooled provided the ultimate heat sink remains available. These highly desirable operational characteristics were observed in the Sandia Brayton loop. This type of behavior is also predicted by our models. Ultimately, these results provide the designers the opportunity to design gas

High exergetic modified Brayton cycle with thermoelectric energy conversion

International Nuclear Information System (INIS)

Yazawa, Kazuaki; Fisher, Timothy S.; Groll, Eckhard A.; Shakouri, Ali

2017-01-01

Highlights: • Modified Brayton cycle with thermoelectric generators. • 1 kW power output scale hybrid gas turbine for residential applications. • Low profile TEGs are embedded in combustor/recuperator/heat-exchangers. • Analytical primary energy efficiency achieves more than 40%. - Abstract: A novel concept using thermoelectric direct power generators (TEGs) integrated into a 1 kW scale miniature Brayton cycle is investigated based on an analytical study. The work considers a residential scale application aiming to achieve 40% primary energy efficiency in contrast to the state-of-the-art miniature gas turbine alone, which can only achieve <16%. A topping cycle TEG for a hot gas temperature at 1600–1700 °C is embedded in the combustor scale of a kitchen stove. This TEG converts a fraction of the heat into electricity, while all the remaining thermal energy proceeds to the Brayton cycle. Turbine-inlet gas temperature regulates to 800–1100 °C by optimizing the air mixture. A second TEG is built in the recuperator; hence, the associated temperature is similar to that of a vehicle exhaust. A third TEG is used for waste heat recovery from flue gas, and then the downstream heat flow is used by a combined-heat-power system. By taking advantage of low-profile modules, the TEG embedded heat exchanges can be compact and low-cost at 0.2–0.3 $/W. The figure-of-merit of the thermoelectric materials considers ZT 1.0–1.8. Assuming that all advanced components are utilized, the primary energy efficiency predicts 42% with power output 720 W from the alternator and 325 W from the TEGs out of 0.456 g/s of a pipeline natural gas input.

New exergy analysis of a regenerative closed Brayton cycle

International Nuclear Information System (INIS)

Naserian, Mohammad Mahdi; Farahat, Said; Sarhaddi, Faramarz

2017-01-01

Highlights: • The maximum power is studied relating to time and size constraints variations. • The influence of time and size constraints on exergy destruction are investigated. • The definitions of heat exergy, and second law efficiency are modified. - Abstract: In this study, the optimal performance of a regenerative closed Brayton cycle is sought through power maximization. Optimization is performed on the output power as the objective function using genetic algorithm. In order to take into account the time and the size constraints in current problem, the dimensionless mass-flow parameter is used. The influence of the unavoidable exergy destruction due to finite-time constraint is taken into account by developing the definition of heat exergy. Finally, the improved definitions are proposed for heat exergy, and the second law efficiency. Moreover, the new definitions will be compared with the conventional ones. For example, at a specified dimensionless mass-flow parameter, exergy overestimation in conventional definition, causes about 31% lower estimation of the second law efficiency. These results could be expected to be utilized in future solar thermal Brayton cycle assessment and optimization.

FY-05 Second Quarter Report On Development of a Supercritical Carbon Dioxide Brayton Cycle: Improving PBR Efficiency and Testing Material Compatibility

International Nuclear Information System (INIS)

Chang Oh

2005-01-01

The objective of this research is to improve a helium Brayton cycle and to develop a supercritical carbon dioxide Brayton cycle for the Pebble Bed Reactor (PBR) that can also be applied to the Fast Gas-Cooled Reactor (FGR) and the Very-High-Temperature Gas-Cooled Reactor (VHTR). The proposed supercritical carbon dioxide Brayton cycle will be used to improve the PBR, FGR, and VHTR net plant efficiency. Another objective of this research is to test materials to be used in the power conversion side at supercritical carbon dioxide conditions. Generally, the optimized Brayton cycle and balance of plant (BOP) to be developed from this study can be applied to Generation-IV reactor concepts. Particularly, we are interested in VHTR because it has a good chance of being built in the near future

Study of reactor Brayton power systems for nuclear electric spacecraft

Science.gov (United States)

1979-01-01

The feasibility of using Brayton power systems for nuclear electric spacecraft was investigated. The primary performance parameters of systems mass and radiator area were determined for systems from 100 to 1000 kW sub e. Mathematical models of all system components were used to determine masses and volumes. Two completely independent systems provide propulsion power so that no single-point failure can jeopardize a mission. The waste heat radiators utilize armored heat pipes to limit meteorite puncture. The armor thickness was statistically determined to achieve the required probability of survival. A 400 kW sub e reference system received primary attention as required by the contract. The components of this system were defined and a conceptual layout was developed with encouraging results. An arrangement with redundant Brayton power systems having a 1500 K (2240 F) turbine inlet temperature was shown to be compatible with the dimensions of the space shuttle orbiter payload bay.

Small particle bed reactors: Sensitivity to Brayton cycle parameters

Science.gov (United States)

Coiner, John R.; Short, Barry J.

Relatively simple particle bed reactor (PBR) algorithms were developed for optimizing low power closed Brayton cycle (CBC) systems. These algorithms allow the system designer to understand the relationship among key system parameters as well as the sensitivity of the PBR size and mass (a major system component) to variations in these parameters. Thus, system optimization can be achieved.

Performance analysis of Brayton cycle system for space power reactor

International Nuclear Information System (INIS)

Li Zhi; Yang Xiaoyong; Zhao Gang; Wang Jie; Zhang Zuoyi

2017-01-01

The closed Brayton cycle system now is the potential choice as the power conversion system for High Temperature Gas-cooled Reactors because of its high energy conversion efficiency and compact configuration. The helium is the best working fluid for the system for its chemical stability and small neutron absorption cross section. However, the Helium has small mole mass and big specific volume, which would lead to larger pipes and heat exchanger. What's more, the big compressor enthalpy rise of helium would also lead to an unacceptably large number of compressor's stage. For space use, it's more important to satisfy the limit of the system's volume and mass, instead of the requirement of the system's thermal capacity. So Noble-Gas binary mixture of helium and xenon is presented as the working fluid for space Brayton cycle. This paper makes a mathematical model for space Brayton cycle system by Fortran language, then analyzes the binary mixture of helium and xenon's properties and effects on power conversion units of the space power reactor, which would be helpful to understand and design the space power reactor. The results show that xenon would lead to a worse system's thermodynamic property, the cycle's efficiency and specific power decrease as xenon's mole fraction increasing. On the other hand, proper amount of xenon would decrease the enthalpy changes in turbomachines, which would be good for turbomachines' design. Another optimization method – the specific power optimization is also proposed to make a comparison. (author)

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

A comparison of radioisotope Brayton and Stirling system for lunar surface mobile power

International Nuclear Information System (INIS)

Harty, R.B.

1991-01-01

A study was performed by the Rocketdyne Division of Rockwell 2.5-kWe modular dynamic isotope power system (DIPS) using a Stirling power conversion system. The results of this study were compared with similar results performed under the DIPS program using a Brayton power conversion system. The study indicated that the Stirling power module has 20% lower mass and 40% lower radiator area than the Brayton module. However, the study also revealed that because the Stirling power module requires a complex heat pipe arrangment to transport heat from the isotope to the Stirling heater head and a pumped NaK heat rejection loop, the Stirling module is much more difficult to integrate with the isotope heat source and heat rejection system

Garrett solar Brayton engine/generator status

Science.gov (United States)

Anson, B.

1982-07-01

The solar advanced gas turbine (SAGT-1) is being developed by the Garrett Turbine Engine Company, for use in a Brayton cycle power conversion module. The engine is derived from the advanced gas turbine (AGT101) now being developd by Garrett and Ford Motor Company for automotive use. The SAGT Program is presently funded for the design, fabrication and test of one engine at Garrett's Phoenix facility. The engine when mated with a solar receiver is called a power conversion module (PCU). The PCU is scheduled to be tested on JPL's test bed concentrator under a follow on phase of the program. Approximately 20 kw of electrical power will be generated.

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.

Heat exchanger design for hot air ericsson-brayton piston engine

Science.gov (United States)

Ďurčanský, P.; Lenhard, R.; Jandačka, J.

2014-03-01

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.

Exergoeconomic multi objective optimization and sensitivity analysis of a regenerative Brayton cycle

International Nuclear Information System (INIS)

Naserian, Mohammad Mahdi; Farahat, Said; Sarhaddi, Faramarz

2016-01-01

Highlights: • Finite time exergoeconomic multi objective optimization of a Brayton cycle. • Comparing the exergoeconomic and the ecological function optimization results. • Inserting the cost of fluid streams concept into finite-time thermodynamics. • Exergoeconomic sensitivity analysis of a regenerative Brayton cycle. • Suggesting the cycle performance curve drawing and utilization. - Abstract: In this study, the optimal performance of a regenerative Brayton cycle is sought through power maximization and then exergoeconomic optimization using finite-time thermodynamic concept and finite-size components. 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 used deploying time variations. The decision variables for the optimum state (of multi objective exergoeconomic optimization) are compared to the maximum power state. One can see that the multi objective exergoeconomic optimization results in a better performance than that obtained with the maximum power state. The results demonstrate that system performance at optimum point of multi objective optimization yields 71% of the maximum power, but only with exergy destruction as 24% of the amount that is produced at the maximum power state and 67% lower total cost rate than that of the maximum power state. In order to assess the impact of the variation of the decision variables on the objective functions, sensitivity analysis is conducted. Finally, the cycle performance curve drawing according to exergoeconomic multi objective optimization results and its utilization, are suggested.

Design and analysis of Helium Brayton cycle for energy conversion system of RGTT200K

International Nuclear Information System (INIS)

Ignatius Djoko Irianto

2016-01-01

The helium Brayton cycle for the design of cogeneration energy conversion system for RGTT200K have been analyzed to obtain the higher thermal efficiency and energy utilization factor. The aim of this research is to analyze the potential of the helium Brayton cycle to be implemented in the design of cogeneration energy conversion system of RGTT200K. Three configuration models of cogeneration energy conversion systems have been investigated. In the first configuration model, an intermediate heat exchanger (IHX) is installed in series with the gas turbine, while in the second configuration model, IHX and gas turbines are installed in parallel. The third configuration model is similar to the first configuration, but with two compressors. Performance analysis of Brayton cycle used for cogeneration energy conversion system of RGTT200K has been done by simulating and calculating using CHEMCAD code. The simulation result shows that the three configuration models of cogeneration energy conversion system give the temperature of thermal energy in the secondary side of IHX more than 800 °C at the reactor coolant mass flow rate of 145 kg/s. Nevertheless, the performance parameters, which include thermal efficiency and energy utilization factor (EUF), are different for each configuration model. By comparing the performance parameter in the three configurations of helium Brayton cycle for cogeneration energy conversion systems RGTT200K, it is found that the energy conversion system with a first configuration has the highest thermal efficiency and energy utilization factor (EUF). Thermal efficiency and energy utilization factor for the first configuration of the reactor coolant mass flow rate of 145 kg/s are 35.82 % and 80.63 %. (author)

Development of a 77K Reverse-Brayton Cryocooler with Multiple Coldheads, Phase I

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...

NERI Quarterly Progress Report -- April 1 - June 30, 2005 -- Development of a Supercritical Carbon Dioxide Brayton Cycle: Improving PBR Efficiency and Testing Material Compatibility

International Nuclear Information System (INIS)

Chang Oh

2005-01-01

The objective of this research is to improve a helium Brayton cycle and to develop a supercritical carbon dioxide Brayton cycle for the Pebble Bed Reactor (PBR) that can also be applied to the Fast Gas-Cooled Reactor (FGR) and the Very-High-Temperature Gas-Cooled Reactor (VHTR). The proposed supercritical carbon dioxide Brayton cycle will be used to improve the PBR, FGR, and VHTR net plant efficiency. Another objective of this research is to test materials to be used in the power conversion side at supercritical carbon dioxide conditions. Generally, the optimized Brayton cycle and balance of plant (BOP) to be developed from this study can be applied to Generation-IV reactor concepts. Particularly, we are interested in VHTR because it has a good chance of being built in the near future

Brayton dynamic isotope power systems update

International Nuclear Information System (INIS)

Davis, K.A.; Pietsch, A.; Casagrande, R.D.

1986-01-01

Brayton dynamic power systems are uniquely suited for space applications. They are compact and highly efficient, offer inherent reliability due to only one moving part, and utilize a single phase and inert working fluid. Additional features include gas bearings, constant speed, and operation at essentially constant temperature. The design, utilizing an inert gas working fluid and gas bearing, is unaffected by zero gravity and can be easily started and restarted in space at low temperatures. This paper describes the salient features of the BIPS as a Dynamic Isotope Power System (DIPS), summarizes the development work to date, establishes the maturity of the design, provides an update on materials technology, and reviews systems integration considerations

A Comparison of Coolant Options for Brayton Power Conversion Heat Rejection Systems

International Nuclear Information System (INIS)

Siamidis, John; Mason, Lee

2006-01-01

This paper describes potential heat rejection design concepts for Brayton power conversion systems. Brayton conversion systems are currently under study by NASA for Nuclear Electric Propulsion (NEP) and surface power applications. The Brayton Heat Rejection Subsystem (HRS) must dissipate waste heat generated by the power conversion system due to inefficiencies in the thermal-to-electric conversion process. Sodium potassium (NaK) and H2O are two coolant working fluids that have been investigated in the design of a pumped loop and heat pipe space HRS. In general NaK systems are high temperature (300 to 1000 K) low pressure systems, and H2O systems are low temperature (300 to 600 K) high pressure systems. NaK is an alkali metal with health and safety hazards that require special handling procedures. On the other hand, H2O is a common fluid, with no health hazards and no special handling procedures. This paper compares NaK and H2O for the HRS pumped loop coolant working fluid. A detailed excel analytical model, HRS O pt, was developed to evaluate the various HRS design parameters. It is capable of analyzing NaK or H2O coolant, parallel or series flow configurations, and numerous combinations of other key parameters (heat pipe spacing, diameter and radial flux, radiator facesheet thickness, fluid duct system pressure drop, system rejected power, etc.) of the HRS. This paper compares NaK against water for the HRS coolant working fluid with respect to the relative mass, performance, design and implementation issues between the two fluids

Computational program to design heat pumps by compression (ciclo 1.0); Programa computacional para diseno de bombas de calor por compresion (ciclo 1.0)

Energy Technology Data Exchange (ETDEWEB)

De Alba Rosano, Mauricio [CIE, UNAM, Temixco, Morelos (Mexico)

2000-07-01

A new computational program has been developed in order to design single stage compression heat pumps. This software, named CICLO 1.0 allows the design of water-water, water-air, air-water and air-air heat pumps, for industrial and residential applications. CICLO 1.0 simulates three types of compressors: reciprocating, screw and scroll. Also has a data base created with REFPROP software which includes eleven refrigerants. The condenser and evaporator simulation includes global conductance (UA) determination, and when one or both are shell and tube's type, this software shows the even number of tube passes by shell. The software determines the best compressor and refrigerant setup taking the COP as a parameter; in order to obtain this, is necessary to know the inlet/outlet conditions of the fluid to be heated, the inlet conditions of the fluid that gives heat, and the electric motor efficiency that drives the compressor. The afforded results by CICLO 1.0 are: operation conditions from compression cycle, that means, pressures and temperatures at the inlet/outlet from every heat pump component are determined: as well as refrigerant mass flux, COP, power required by compressor, volumetric and isentropic efficiencies, heat exchangers global conductance and more data. CICLO 1.0 has been executed with heat pump data that nowadays are operating, and the results from the simulation have been very similar each other with data reported from operational facilities. [Spanish] Se ha desarrollado un nuevo programa computacional para el diseno de bombas de calor por compresion de vapor de una sola etapa. Este programa, CICLO 1.0, permite el diseno de bombas de calor de tipo: agua-agua, agua-aire, aire-agua y aire-aire, que se utilicen para aplicaciones industriales, de servicios y residenciales. CICLO 1.0 simula tres tipos de compresores: reciprocante, de tornillo y scroll: cuenta con una base de datos de refrigerantes creada con el programa REFPROP la cual incluye once

Development of the System Dynamics Code using Homogeneous Equilibrium Model for S-CO{sub 2} Brayton cycle Transient Analyses

Energy Technology Data Exchange (ETDEWEB)

Bae, Seong Jun; Lee, Won Woong; Oh, Bongseong; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2016-10-15

The features of the S-CO{sub 2} Brayton cycle come from a small compressing work by designing the compressor inlet close the critical point of CO{sub 2}. This means the system condition can be operating under two-phase or sub-critical phase during transient situations such as changes of cooling system performance, load variations, etc. Since there is no operating MW scale S-CO{sub 2} Brayton cycle system in the world yet, using an analytical code is the only way to predict the system behavior and develop operating strategies of the S-CO{sub 2} Brayton cycles. Therefore, the development of a credible system code is an important part for the practical S-CO{sub 2} system research. The current status of the developed system analysis code for S-CO{sub 2} Brayton cycle transient analyses in KAIST and verification results are presented in this paper. To avoid errors related with convergences of the code during the phase changing flow calculation in GAMMA+ code, the authors have developed a system analysis code using Homogeneous Equilibrium Model (HEM) for the S-CO{sub 2} Brayton cycle transient analysis. The backbone of the in-house code is the GAMMA+1.0 code, but treating the quality of fluid by tracking system enthalpy gradient every time step. Thus, the code adopts pressure and enthalpy as the independent scalar variables to track the system enthalpy for updating the quality of the system every time step. The heat conduction solving method, heat transfer correlation and frictional losses on the pipe are referred from the GAMMA+ code.

Projeto de EDFAs com controle automatico de ganho totalmente optico para aplicações em redes WDM

OpenAIRE

Julio Cesar Rodrigues Fernandes de Oliveira

2004-01-01

Resumo: A variação na potência da entrada em amplificadores ópticos a fibra dopada com Érbio (EDFAs) induz alterações em seu ganho. No caso de sistemas ou redes WDM onde o número de canais acoplados ao amplificador varia, o ganho torna-se dependente do número de canais que estão sendo transmitidos, especialmente se o amplificador opera saturado. Este trabalho apresenta o desenvolvimento e a avaliação experimental de uma técnica de controle de ganho totalmente óptica para EDFAs. Esta técnica d...

Research on the Development of the Supercritical CO{sub 2} Dual Brayton Cycle

Energy Technology Data Exchange (ETDEWEB)

Baik, Young-Jin; Na, Sun Ik; Cho, Junhyun; Shin, Hyung-Ki; Lee, Gilbong [Korea Institute of Energy Research (KIER), Daejeon (Korea, Republic of)

2016-10-15

Because of the growing interest in supercritical carbon dioxide power cycle technology owing to its potential enhancement in compactness and efficiency, supercritical carbon dioxide cycles have been studied in the fields of nuclear power, concentrated solar power (CSP), and fossil fuel power generation. This study introduces the current status of the research project on the supercritical carbon dioxide power cycle by Korea Institute of Energy Research (KIER). During the first phase of the project, the un-recuperated supercritical Brayton cycle test loop was built and tested. In phase two, researchers are designing and building a supercritical carbon dioxide dual Brayton cycle, which utilizes two turbines and two recuperators. Under the simulation condition considered in this study, it was confirmed that the design parameter has an optimal value for maximizing the net power in the supercritical carbon dioxide dual cycle.

Brayton rotating units for space reactor power systems

Energy Technology Data Exchange (ETDEWEB)

Gallo, Bruno M.; El-Genk, Mohamed S. [Institute for Space and Nuclear Power Studies and Chemical and Nuclear Engineering Dept., The Univ. of New Mexico, Albuquerque, NM 87131 (United States)

2009-09-15

Designs and analyses models of centrifugal-flow compressor and radial-inflow turbine of 40.8kW{sub e} Brayton Rotating Units (BRUs) are developed for 15 and 40 g/mole He-Xe working fluids. Also presented are the performance results of a space power system with segmented, gas cooled fission reactor heat source and three Closed Brayton Cycle loops, each with a separate BRU. The calculated performance parameters of the BRUs and the reactor power system are for shaft rotational speed of 30-55 krpm, reactor thermal power of 120-471kW{sub th}, and turbine inlet temperature of 900-1149 K. With 40 g/mole He-Xe, a power system peak thermal efficiency of 26% is achieved at rotation speed of 45 krpm, compressor and turbine inlet temperatures of 400 and 1149 K and 0.93 MPa at exit of the compressor. The corresponding system electric power is 122.4kW{sub e}, working fluid flow rate is 1.85 kg/s and the pressure ratio and polytropic efficiency are 1.5% and 86.3% for the compressor and 1.42% and 94.1% for the turbine. For the same nominal electrical power of 122.4kW{sub e}, decreasing the molecular weight of the working fluid (15 g/mole) decreases its flow rate to 1.03 kg/s and increases the system pressure to 1.2 MPa. (author)

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.

Dynamic simulation of 10 kW Brayton cryocooler for HTS cable

International Nuclear Information System (INIS)

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

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.

Brayton-Cycle Baseload Power Tower CSP System

Energy Technology Data Exchange (ETDEWEB)

Anderson, Bruce [Wilson Solarpower Corporation, Boston, MA (United States)

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.

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

SP-100/Brayton power system concepts

International Nuclear Information System (INIS)

Owen, D.F.

1989-01-01

Use of closed Brayton cycle (CBC) power conversion technology has been investigated for use with SP-100 reactors for space power systems. The CBC power conversion technology is being developed by Rockwell International under the Dynamic Isotype Power System (DIPS) and Space Station Freedom solar dynamic power system programs to provide highly efficient power conversion with radioisotype and solar collector heat sources. Characteristics including mass, radiator area, thermal power, and operating temperatures for systems utilizing SP-100 reactor and CBC power conversion technology were determined for systems in the 10-to 100-kWe power range. Possible SP-100 reactor/CBC power system configurations are presented. Advantages of CBC power conversion technology with regard to reactor thermal power, operating temperature, and development status are discussed

Potential advantages of coupling supercritical CO2 Brayton cycle to water cooled small and medium size reactor

International Nuclear Information System (INIS)

Yoon, Ho Joon; Ahn, Yoonhan; Lee, Jeong Ik; Addad, Yacine

2012-01-01

Highlights: ► S-CO 2 cycle as candidate for SMS. ► MATLAB code used for S-CO 2 cycle analysis. ► Pressure ratio and split ratio comparison analyzed. - Abstract: The supercritical carbon dioxide (S-CO 2 ) Brayton cycle is being considered as a favorable candidate for the next generation nuclear reactors power conversion systems. Major benefits of the S-CO 2 Brayton cycle compared to other Brayton cycles are: (1) high thermal efficiency in relatively low turbine inlet temperature, (2) compactness of the turbomachineries and heat exchangers and (3) simpler cycle layout at an equivalent or superior thermal efficiency. However, these benefits can be still utilized even in the water-cooled reactor technologies under special circumstances. A small and medium size water-cooled nuclear reactor (SMR) has been gaining interest due to its wide range of application such as electricity generation, seawater desalination, district heating and propulsion. Another key advantage of a SMR is that it can be transported from one place to another mostly by maritime transport due to its small size, and sometimes even through a railway system. Therefore, the combination of a S-CO 2 Brayton cycle with a SMR can reinforce any advantages coming from its small size if the S-CO 2 Brayton cycle has much smaller size components, and simpler cycle layout compared to the currently considered steam Rankine cycle. In this paper, SMART (System-integrated Modular Advanced ReacTor), a 330 MW th integral reactor developed by KAERI (Korea Atomic Energy Institute) for multipurpose utilization, is considered as a potential candidate for applying the S-CO 2 Brayton cycle and advantages and disadvantages of the proposed system will be discussed in detail. In consideration of SMART condition, the turbine inlet pressure and size of heat exchangers are analyzed by using in-house code developed by KAIST–Khalifa University joint research team. According to the cycle evaluation, the maximum cycle efficiency

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

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.

The feasibility study on supercritical methane Recuperated Brayton Cycle for waste heat recovery

KAUST Repository

Dyuisenakhmetov, Aibolat

2017-05-01

Recuperated Brayton Cycle (RBC) has attracted the attention of research scientists not only as a possible replacement for the steam cycle at nuclear power plants but also as an efficient bottoming cycle for waste heat recovery and for concentrated solar power. RBC’s compactness and the ease at which it can be integrated into existent power plants for waste heat recovery require few modifications. Methane, carbon dioxide and trifluoromethane are analyzed as possible working fluids. This work shows that it is possible to achieve higher efficiencies using methane under some operating conditions. However, as it turns out, the performance of Recuperated Brayton Cycle should be evaluated based on net output work. When the performance is assessed on the net output work criteria carbon dioxide still proves to be superior to other gases. This work also suggests that piston engines as compressors and expanders may be used instead of rotating turbines since reciprocating pistons have higher isentropic efficiencies.

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     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.

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.

Loop containment (joint integrity) assessment Brayton Isotope Power System flight system

International Nuclear Information System (INIS)

1976-01-01

The Brayton Isotope Power System (BIPS) contains a large number of joints. Since the failure of a joint would result in loss of the working fluid and consequential failure of the BIPS, the integrity of the joints is of paramount importance. The reliability of the ERDA BIPS loop containment (joint integrity) is evaluated. The conceptual flight system as presently configured is depicted. A brief description of the flight system is given

Ciclos de desenvolvimento humano e formação de educadores

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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.

Performance Optimization of a Solar-Driven Multi-Step Irreversible Brayton Cycle Based on a Multi-Objective Genetic Algorithm

Directory of Open Access Journals (Sweden)

Ahmadi Mohammad Hosein

2016-01-01

Full Text Available An applicable approach for a multi-step regenerative irreversible Brayton cycle on the basis of thermodynamics and optimization of thermal efficiency and normalized output power is presented in this work. In the present study, thermodynamic analysis and a NSGA II algorithm are coupled to determine the optimum values of thermal efficiency and normalized power output for a Brayton cycle system. Moreover, three well-known decision-making methods are employed to indicate definite answers from the outputs gained from the aforementioned approach. Finally, with the aim of error analysis, the values of the average and maximum error of the results are also calculated.

Numerical Comparison of NASA's Dual Brayton Power Generation System Performance Using CO2 or N2 as the Working Fluid

Science.gov (United States)

Ownens, Albert K.; Lavelle, Thomas M.; Hervol, David S.

2010-01-01

A Dual Brayton Power Conversion System (DBPCS) has been tested at the NASA Glenn Research Center using Nitrogen (N2) as the working fluid. This system uses two closed Brayton cycle systems that share a common heat source and working fluid but are otherwise independent. This system has been modeled using the Numerical Propulsion System Simulation (NPSS) environment. This paper presents the results of a numerical study that investigated system performance changes resulting when the working fluid is changed from gaseous (N2) to gaseous carbon dioxide (CO2).

Preliminary Design of S-CO2 Brayton Cycle for KAIST Micro Modular Reactor

International Nuclear Information System (INIS)

Kim, Seong Gu; Kim, Min Gil; Bae, Seong Jun; Lee, Jeong Ik

2013-01-01

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 2 Brayton cycle (S-CO 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 2 coolant, authors selected a simple recuperated S-CO 2 Brayton cycle as a power conversion system for KAIST MMR. The size of components of the S-CO 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

Brayton Point coal conversion project (NEPCO)

Energy Technology Data Exchange (ETDEWEB)

Sullivan, W.F. Jr.

1982-05-01

The New England Power Company (NEPCO) recently converted Brayton Point Power Station Units 1, 2, and 3 from oil to coal. The coal conversion project is the largest coal conversion project in the nation to date. Stone and Webster Engineering Corporation (SWEC) was hired as the engineer/constructor for the project. Units 1 and 2 are 250-MW Combustion Engineering boilers, and Unit 3 is a 650-MW Babcock and Wilcox boiler. All three units were originally designed to burn pulverized coal but were converted to oil during the years of low oil prices. Studies performed by NEPCO and SWEC indicated that the areas discussed in the following paragraphs required upgrading before the units could efficiently burn coal and meet Federal and State environmental requirements. All units have been converted and are operating. This paper discusses design modifications required to burn coal, startup, and initial operating problems, and solutions.

Gestión documental sonora: el ciclo de vida digital en los archivos sonoros

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Perla Olivia Rodríguez Reséndiz

2017-10-01

Full Text Available La preservación de soportes sonoros analógicos (discos, casetes, cintas de carrete abierto, entre otros, se cimienta en etapas y procesos documentales que se llevan a cabo desde que se incorpora el material en el archivo hasta que es consultado. Los procesos documentales pueden ordenarse en etapas documentales que forman el ciclo de vida. Las etapas documentales empleadas en el archivo analógico quedaron en desuso ante el crecimiento de colecciones digitales. Frente a tal situación, resulta relevante revisar los procesos y determinar las etapas a través de las cuales transita un documento digital sonoro durante el ciclo de vida digital. El artículo que se presenta tiene como objetivos identificar y exponer los principales procesos que forman parte del ciclo de vida digital en la preservación digital de archivos sonoros. Para ello, se analiza literatura científica relacionada con los procesos documentales y el ciclo de vida de los archivos sonoros; además, se examinan algunos de los más relevantes y recientes planes de preservación digital de archivos sonoros formulados en bibliotecas y archivos de alcance nacional. Con ello, se exponen conceptos que definen las etapas y los procesos documentales que se llevan a cabo en un archivo analógico y se presentan los modelos de ciclo de vida digital que incluyen materiales sonoros. Como resultado se expone la identificación y descripción de los principales procesos señalados en los modelos de ciclo de vida digital; además, se propone una ordenación de las principales etapas del ciclo de vida en la preservación digital.

System safety program plan for the Isotope Brayton Ground Demonstration System (phase I)

International Nuclear Information System (INIS)

1976-01-01

The safety engineering effort to be undertaken in achieving an acceptable level of safety in the Brayton Isotope Power System (BIPS) development program is discussed. The safety organizational relationships, the methods to be used, the tasks to be completed, and the documentation to be published are described. The plan will be updated periodically as the need arises

Inteligencia emocional y autoconcepto en los estudiantes de primer ciclo

OpenAIRE

Castillo Canales, Braulio

2017-01-01

En nuestra investigación se tuvo como problema: ¿Qué relación existe entre inteligencia emocional y autoconcepto en los estudiantes de primer ciclo de Administración en Turismo y Hotelería de la Universidad César Vallejo, Lima 2015-II? Además el objetivo fue: Determinar la relación entre inteligencia emocional y autoconcepto en los estudiantes de primer ciclo de Administración en Turismo y Hotelería de la Universidad César Vallejo, Lima 2015-II. El tipo de estudio fue básica...

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

International Nuclear Information System (INIS)

1976-01-01

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

El ciclo político - económico en Colombia, 1925-1999

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Mauricio López González, , Christian Fresard Briones

2002-07-01

Full Text Available La teoría de los ciclos político-económicos ha mostrado su capacidad de explicar los ciclos económicos originados por las autoridades económicas de acuerdo con intereses políticos, electorales o ideológicos. Este artículo realiza una revisión de la evidencia empírica de esta teoría en Colombia entre 1925 y 1998. Los resultados obtenidos muestran que en el país se han presentado tanto ciclos de tipo oportunista como partidista, ampliando los resultados obtenidos en estudios anteriores. En consecuencia, se concluye que en Colombia las autoridades económicas han manejado las variables económicas con el fin de conseguir resultados políticos favorables en las elecciones.

Preliminary design study of an alternate heat source assembly for a Brayton isotope power system

Science.gov (United States)

Strumpf, H. J.

1978-01-01

Results are presented for a study of the preliminary design of an alternate heat source assembly (HSA) intended for use in the Brayton isotope power system (BIPS). The BIPS converts thermal energy emitted by a radioactive heat source into electrical energy by means of a closed Brayton cycle. A heat source heat exchanger configuration was selected and optimized. The design consists of a 10 turn helically wound Hastelloy X tube. Thermal analyses were performed for various operating conditions to ensure that post impact containment shell (PICS) temperatures remain within specified limits. These limits are essentially satisfied for all modes of operation except for the emergency cooling system for which the PICS temperatures are too high. Neon was found to be the best choice for a fill gas for auxiliary cooling system operation. Low cycle fatigue life, natural frequency, and dynamic loading requirements can be met with minor modifications to the existing HSA.

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

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María Giomar Nates Parra

1989-01-01

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.

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

International Nuclear Information System (INIS)

Serrano, I.P.; Linares, J.I.; Cantizano, A.; Moratilla, B.Y.

2014-01-01

Highlights: •We propose an enhanced power conversion system layout for a Model C fusion reactor. •Proposed layout is based on a modified recompression supercritical CO 2 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 TECNO F US 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 CO 2 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 CO 2 Brayton cycles

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%.

Optimization of a regenerative Brayton cycle by maximization of a newly defined second law efficiency

NARCIS (Netherlands)

Haseli, Y.

2013-01-01

The idea is to find out whether 2nd law efficiency optimization may be a suitable trade-off between maximum work output and maximum 1st law efficiency designs for a regenerative gas turbine engine operating on the basis of an open Brayton cycle. The primary emphasis is placed on analyzing the ideal

Experimental Investigations from the Operation of a 2 Kw Brayton Power Conversion Unit and a Xenon Ion Thruster

Science.gov (United States)

Mason, Lee; Birchenough, Arthur; Pinero, Luis

2004-01-01

A 2 kW Brayton Power Conversion Unit (PCU) and a xenon ion thruster were integrated with a Power Management and Distribution (PMAD) system as part of a Nuclear Electric Propulsion (NEP) Testbed at NASA's Glenn Research Center. Brayton converters and ion thrusters are potential candidates for use on future high power NEP missions such as the proposed Jupiter Icy Moons Orbiter (JIMO). The use of existing lower power test hardware provided a cost-effective means to investigate the critical electrical interface between the power conversion system and ion propulsion system. The testing successfully demonstrated compatible electrical operations between the converter and the thruster, including end-to-end electric power throughput, high efficiency AC to DC conversion, and thruster recycle fault protection. The details of this demonstration are reported herein.

Comparison between reverse Brayton and Kapitza based LNG boil-off gas reliquefaction system using exergy analysis

Science.gov (United States)

Kochunni, Sarun Kumar; Chowdhury, Kanchan

2017-02-01

LNG boil-off gas (BOG) reliquefaction systems in LNG carrier ships uses refrigeration devices which are based on reverse Brayton, Claude, Kapitza (modified Claude) or Cascade cycles. Some of these refrigeration devices use nitrogen as the refrigerants and hence nitrogen storage vessels or nitrogen generators needs to be installed in LNG carrier ships which consume space and add weight to the carrier. In the present work, a new configuration based on Kapitza liquefaction cycle which uses BOG itself as working fluid is proposed and has been compared with Reverse Brayton Cycle (RBC) on sizes of heat exchangers and compressor operating parameters. Exergy analysis is done after simulating at steady state with Aspen Hysys 8.6® and the comparison between RBC and Kapitza may help designers to choose reliquefaction system with appropriate process parameters and sizes of equipment. With comparable exergetic efficiency as that of an RBC, a Kaptiza system needs only BOG compressor without any need of nitrogen gas.

Mission environments for the Isotope Brayton Flight System (preliminary)

International Nuclear Information System (INIS)

1975-01-01

The mission environments for the Isotope Brayton Flight Systems (IBFS) are summarized. These are based on (1) those environments established for the MHW-RTG system in the LES 8/9 and Mariner J/S and (2) engineering projections of those likely to exit for the IBFS. The pre-launch environments address transportation, storage, handling and assembly (to spacecraft) and checkout, field transportation, and launch site operations. Launch environments address the Titan IIIC and Shuttle launch vehicles. Operational mission environments address normal space temperature and meteoroide environments. Special environments that may be applicable to DOD missions are not included. Accident environments address explosion and fire for the Titan IIIC and the Shuttle, reentry, earth impact and post impact

¿Sincronizaron México y Estados Unidos sus ciclos económicos con el TLCAN?

Directory of Open Access Journals (Sweden)

Domingo Rodríguez Benavides

2015-01-01

Full Text Available En este trabajo investigamos, a través de un modelo estructural de series de tiempo múltiple, con una especificación generalizada de ciclo estocástico, si los ciclos económicos del PIB de México muestran una mayor sincronización con los ciclos del PIB de Estados Unidos a partir de la entrada en vigor del Tratado de Libre Comercio de América del Norte (TLCAN, con respecto al periodo previo. Con tal fin, probamos la hipótesis nula de un ci - clo común, como es definida en los modelos estructurales como el empleado por Carvalho, Harvey y Trimbur (2007, contra la hipótesis de un ciclo similar entre ambas economías. La existencia de un ciclo económico común entre dos economías implica que uno de ellos es proporcional al otro (Harvey 2002. Los resultados muestran que antes de la entrada en vigor del TLCAN (1960:1-1994:4 ninguna de las dos economías posee un ciclo econó - mico común. Al contrario, a partir de la firma del TLCAN (1995:1-2012:4, no es posible rechazar la hipótesis de la existencia de un ciclo económico común entre ambas economías, lo cual interpretamos como una mayor sincronización de sus productos. Observamos, sin embargo que, con respecto al periodo previo, la sincronización cíclica ocurre en un periodo de lento crecimiento donde los flujos comerciales del TLCAN con Estados Unidos decli - nan relativamente desde el año 2000. Ello cuestiona el fundamento de la sincronización, explicada en México por la apertura comercial del TLCAN. Derechos Reservados©2015 Universidad Nacional Autónoma de México, Facultad de Contaduría y Administración. Este es un artículo de acceso abierto distribuido bajo los términos de la Licencia Creative Commons CC BY-NC-ND 4.0.

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...

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...

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

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

1998-12-31

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.

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.

Enhanced arrangement for recuperators in supercritical CO{sub 2} Brayton power cycle for energy conversion in fusion reactors

Energy Technology Data Exchange (ETDEWEB)

Serrano, I.P.; Linares, J.I., E-mail: linares@dim.icai.upcomillas.es; Cantizano, A.; Moratilla, B.Y.

2014-10-15

Highlights: •We propose an enhanced power conversion system layout for a Model C fusion reactor. •Proposed layout is based on a modified recompression supercritical CO{sub 2} 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 TECNO{sub F}US 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 CO{sub 2} 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 CO{sub 2} Brayton cycles.

Optimization of airfoil-type PCHE for the recuperator of small scale brayton cycle by cost-based objective function

International Nuclear Information System (INIS)

Kwon, Jin Gyu; Kim, Tae Ho; Park, Hyun Sun; Cha, Jae Eun; Kim, Moo Hwan

2016-01-01

Highlights: • Suggest the Nusselt number and Fanning friction factor correlation for airfoil-type PCHE. • Show that cost-based optimization is available to airfoil-type PCHE. • Suggest the recuperator design for SCIEL test loop at KAERI by cost-based objective function with correlations from numerical analysis. - Abstract: Supercritical carbon dioxide (SCO_2) Brayton cycle gives high efficiency of power cycle with small size. Printed circuit heat exchangers (PCHE) are proper selection for the Brayton cycle because their operability at high temperature and high pressure with small size. Airfoil fin PCHE was suggested by Kim et al. (2008b), it can provide high heat transfer-like zigzag channel PCHE with low pressure drop-like straight channel PCHE. Optimization of the airfoil fin PCHE was not performed like the zigzag channel PCHE. For optimization of the airfoil fin PCHE, the operating condition of the recuperator of SCO_2 Integral Experiment Loop (SCIEL) Brayton cycle test loop at Korea Atomic Energy Research Institute (KAERI) was used. We performed CFD analysis for various airfoil fin configurations using ANSYS CFX 15.0, and made correlations for predicting the Nusselt number and the Fanning friction factor. The recuperator was designed by the simple energy balance code with our correlations. Using the cost-based objective function with production cost and operation cost from size and pressure drop of the recuperator, we evaluated airfoil fin configuration by using total cost and suggested the optimization configuration of the airfoil fin PCHE.

Optimization of airfoil-type PCHE for the recuperator of small scale brayton cycle by cost-based objective function

Energy Technology Data Exchange (ETDEWEB)

Kwon, Jin Gyu [Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Kim, Tae Ho [Department of Mechanical Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Park, Hyun Sun, E-mail: hejsunny@postech.ac.kr [Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Cha, Jae Eun [Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Kim, Moo Hwan [Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Korea Institute of Nuclear Safety, Daejeon 305-338 (Korea, Republic of)

2016-03-15

Highlights: • Suggest the Nusselt number and Fanning friction factor correlation for airfoil-type PCHE. • Show that cost-based optimization is available to airfoil-type PCHE. • Suggest the recuperator design for SCIEL test loop at KAERI by cost-based objective function with correlations from numerical analysis. - Abstract: Supercritical carbon dioxide (SCO{sub 2}) Brayton cycle gives high efficiency of power cycle with small size. Printed circuit heat exchangers (PCHE) are proper selection for the Brayton cycle because their operability at high temperature and high pressure with small size. Airfoil fin PCHE was suggested by Kim et al. (2008b), it can provide high heat transfer-like zigzag channel PCHE with low pressure drop-like straight channel PCHE. Optimization of the airfoil fin PCHE was not performed like the zigzag channel PCHE. For optimization of the airfoil fin PCHE, the operating condition of the recuperator of SCO{sub 2} Integral Experiment Loop (SCIEL) Brayton cycle test loop at Korea Atomic Energy Research Institute (KAERI) was used. We performed CFD analysis for various airfoil fin configurations using ANSYS CFX 15.0, and made correlations for predicting the Nusselt number and the Fanning friction factor. The recuperator was designed by the simple energy balance code with our correlations. Using the cost-based objective function with production cost and operation cost from size and pressure drop of the recuperator, we evaluated airfoil fin configuration by using total cost and suggested the optimization configuration of the airfoil fin PCHE.

Ciclo largo y sistema financiero: Crisis, contracción del crédito y ganancia

Directory of Open Access Journals (Sweden)

Teresa Aguirre

2017-09-01

Full Text Available Los ciclos económicos y el sistema financiero se relacionan de diferentes maneras, una de las más destacas que han analizado la relación entre el ciclo económico y finanzas, ha sido el estudio de las ondas largas o ciclos Kondratieff. Otra forma de análisis ha sido a través del ciclo monetario que conduce a las crisis financieras (Minsky y Kindleberger entre los más conocidos y finalmente una manera distinta ha sido el estudio de las particularidades de cada ciclo de auge-frenesí financiero y declive. Este trabajo propone un breve recuento de cómo se ha analizado la relación: capital productivo y financiero en las ondas largas, a través del planteamiento de tres de tres autores que han marcado hitos en el análisis: Nikolai Kondratieff, Ernest Mandel y Carlota Pérez. Nuestro objetivo es indagar sobre una pregunta central que se hace de manera reiterada: ¿por qué a pesar de la revolución científico-técnica basada en la informática, con el desarrollo de la robótica, cibernética, biotecnología y nanotecnología, no se ha logrado una etapa de crecimiento sólida y sostenida que dé lugar a una etapa expansiva.

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.

Experimental Investigation from the Operation of a 2 kW Brayton Power Conversion Unit and a Xenon Ion Thruster

Science.gov (United States)

Hervol, David; Mason, Lee; Birchenough, Art; Pinero, Luis

2004-01-01

A 2kW Brayton Power Conversion Unit (PCU) and a xenon ion thruster were integrated with a Power Management and Distribution (PMAD) system as part of a Nuclear Electric Propulsion (NEP) Testbed at NASA's Glenn Research Center. Brayton Converters and ion thrusters are potential candidates for use on future high power NEP mission such as the proposed Jupiter Icy Moons Orbiter (JIMO). The use of a existing lower power test hardware provided a cost effective means to investigate the critical electrical interface between the power conversion system and the propulsion system. The testing successfully demonstrated compatible electrical operations between the converter and the thruster, including end-to-end electric power throughput, high efficiency AC to DC conversion, and thruster recycle fault protection. The details of this demonstration are reported herein.

Subperíodos fenológicos e ciclo da soja conforme grupos de maturidade e datas de semeadura

Directory of Open Access Journals (Sweden)

Roberto Trentin

2013-07-01

Full Text Available O objetivo deste trabalho foi estimar a duração dos subperíodos fenológicos e do ciclo de desenvolvimento da soja, de acordo com grupos de maturidade e datas de semeadura, e determinar as funções de distribuição de probabilidades que melhor caracterizam a distribuição destes dados. Foram avaliadas as funções exponencial, gama, lognormal, normal e Weibull, tendo-se verificado a de melhor ajuste aos dados de desenvolvimento simulado da cultura, de acordo com dados meteorológicos diários coletados de outubro de 1968 a julho de 2012, na estação climatológica principal de Santa Maria, RS. A simulação do desenvolvimento da cultura foi feita para diferentes datas de semeadura, com os grupos de maturidade (GM: 5.9-6.8, ciclo precoce/semiprecoce; 6.9-7.3, ciclo médio; e 7.4-8.0, ciclo semitardio/tardio. A função lognormal é a que melhor se ajusta à duração dos subperíodos e do ciclo da soja. Esta duração varia conforme a data de semeadura, com ciclo maior nas semeaduras antecipadas (outubro e menor nas tardias (dezembro.

Design and fabrication of the Mini-Brayton Recuperator (MBR)

Science.gov (United States)

Killackey, J. J.; Graves, R.; Mosinskis, G.

1978-01-01

Development of a recuperator for a 2.0 kW closed Brayton space power system is described. The plate-fin heat exchanger is fabricated entirely from Hastelloy X and is designed for 10 years continuous operation at 1000 K (1300 F) with a Xenon-helium working fluid. Special design provisions assure uniform flow distribution, crucial for meeting 0.975 temperature effectiveness. Low-cycle fatigue, resulting from repeated startup and shutdown cycles, was identified as the most critical structural design problem. It is predicted that the unit has a minimum fatigue life of 220 cycles. This is in excess of the BIPS requirement of 100 cycles. Heat transfer performance and thermal cycle testing with air, using a prototype unit, verified that all design objectives can be met.

Advanced Rankine and Brayton cycle power systems: Materials needs and opportunities

Science.gov (United States)

Grisaffe, S. J.; Guentert, D. C.

1974-01-01

Conceptual advanced potassium Rankine and closed Brayton power conversion cycles offer the potential for improved efficiency over steam systems through higher operating temperatures. However, for utility service of at least 100,000 hours, materials technology advances will be needed for such high temperature systems. Improved alloys and surface protection must be developed and demonstrated to resist coal combustion gases as well as potassium corrosion or helium surface degradation at high temperatures. Extensions in fabrication technology are necessary to produce large components of high temperature alloys. Long time property data must be obtained under environments of interest to assure high component reliability.

Advanced Rankine and Brayton cycle power systems - Materials needs and opportunities

Science.gov (United States)

Grisaffe, S. J.; Guentert, D. C.

1974-01-01

Conceptual advanced potassium Rankine and closed Brayton power conversion cycles offer the potential for improved efficiency over steam systems through higher operating temperatures. However, for utility service of at least 100,000 hours, materials technology advances will be needed for such high temperature systems. Improved alloys and surface protection must be developed and demonstrated to resist coal combustion gases as well as potassium corrosion or helium surface degradation at high temperatures. Extensions in fabrication technology are necessary to produce large components of high temperature alloys. Long-time property data must be obtained under environments of interest to assure high component reliability.

Study of reverse Brayton cryocooler with Helium-Neon mixture for HTS cable

Science.gov (United States)

Dhillon, A. K.; Ghosh, P.

2017-12-01

As observed in the earlier studies, helium is more efficient than neon as a refrigerant in a reverse Brayton cryocooler (RBC) from the thermodynamic point of view. However, the lower molecular weight of helium leads to higher refrigerant inventory as compared to neon. Thus, helium is suitable to realize the high thermodynamic efficiency of RBC whereas neon is appropriate for the compactness of the RBC. A binary mixture of helium and neon can be used to achieve high thermodynamic efficiency in the compact reverse Brayton cycle (RBC) based cryocooler. In this paper, an attempt has been made to analyze the thermodynamic performance of the RBC with a binary mixture of helium and neon as the working fluid to provide 1 kW cooling load for high temperature superconductor (HTS) power cables working with a temperature range of 50 K to 70 K. The basic RBC is simulated using Aspen HYSYS V8.6®, a commercial process simulator. Sizing of each component based on the optimized process parameters for each refrigerant is performed based on a computer code developed using Engineering Equation Solver (EES-V9.1). The recommendation is provided for the optimum mixture composition of the refrigerant based on the trade-off factors like thermodynamic efficiency such as the exergy efficiency and equipment considerations. The outcome of this study may be useful for recommending a suitable refrigerant for the RBC operating at a temperature level of 50 K to 70 K.

Extension of the supercritical carbon dioxide Brayton cycle for application to the Very High Temperature Reactor

International Nuclear Information System (INIS)

Moisseytsev, A.; Sienicki, J. J.

2010-01-01

An investigation has been carried out of the feasibility of applying the supercritical carbon dioxide (S-CO 2 ) Brayton cycle to the Very High Temperature Reactor (VHTR). Direct application of the standard S-CO 2 recompression cycle to the VHTR was found to be challenging because of the mismatch in the inherent temperature drops across the He and CO 2 sides of the reactor heat exchanger resulting in a relatively low cycle efficiency of 45 % compared to 48 % for a direct helium cycle. Two approaches consisting of either a cascaded cycle arrangement with three separate cascaded S-CO 2 cycles or, alternately, operation of a single S-CO 2 cycle with the minimum pressure below the critical pressure and the minimum temperature above the critical temperature have been identified and shown to successfully enable the S-CO 2 Brayton cycle to be adapted to the VHTR such that the benefits of the higher S-CO 2 cycle efficiency can be realized. For both approaches, S-CO 2 cycle efficiencies in excess of 49 % are calculated. (authors)

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...

Thermoeconomic Analysis and Optimization of a New Combined Supercritical Carbon Dioxide Recompression Brayton/Kalina Cycle

Directory of Open Access Journals (Sweden)

S. Mohammad S. Mahmoudi

2016-10-01

Full Text Available A new combined supercritical CO2 recompression Brayton/Kalina cycle (SCRB/KC is proposed. In the proposed system, waste heat from a supercritical CO2 recompression Brayton cycle (SCRBC is recovered by a Kalina cycle (KC to generate additional electrical power. The performances of the two cycles are simulated and compared using mass, energy and exergy balances of the overall systems and their components. Using the SPECO (Specific Exergy Costing approach and employing selected cost balance equations for the components of each system, the total product unit costs of the cycles are obtained. Parametric studies are performed to investigate the effects on the SCRB/KC and SCRBC thermodynamic and thermoeconomic performances of key decision parameters. In addition, considering the exergy efficiency and total product unit cost as criteria, optimization is performed for the SCRBC and SCRB/KC using Engineering Equation Solver software. The results indicate that the maximum exergy efficiency of the SCRB/KC is higher than that of the SCRBC by up to 10%, and that the minimum total product unit cost of the SCRB/KC is lower than that of the SCRBC by up to 4.9%.

A four-year investigation of Brayton cycle systems for future french space power applications

International Nuclear Information System (INIS)

Tilliette, Z.P.; Proust, E.; Carre, F.

1988-01-01

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: the matching of the power system to the available radiator dimensions up to 200 kWe, the direct or indirect waste heat transfer to the radiator, the use of a recuperator, the recent work on moderate (25 kWe) power levels, the simulation studies related to various operating conditions and the 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. As far as a gas-cooled reactor, direct cycle system is concerned, the relevance to the reactor technology and the concept for moderator thermal conditioning, is particularly addressed

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

International Nuclear Information System (INIS)

Le Roux, W.G.; Bello-Ochende, T.; Meyer, J.P.

2014-01-01

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

Potential improvements of supercritical recompression CO2 Brayton cycle by mixing other gases for power conversion system of a SFR

International Nuclear Information System (INIS)

Jeong, Woo Seok; Lee, Jeong Ik; Jeong, Yong Hoon

2011-01-01

Highlights: → S-CO 2 cycle could be enhanced by shifting the critical point of working fluids using gas mixture. → In-house cycle code was developed to analyze supercritical Brayton cycles with gas mixture. → Gas mixture candidates were selected through a screening process: CO 2 mixing with N 2 , O 2 , He, and Ar. → CO 2 -He binary mixture shows the highest cycle efficiency increase. → Lowering the critical temperature and critical pressure of the coolant has a positive effect on the total cycle efficiency. - Abstract: 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 subjected to a possible sodium-water reaction. To prevent any hazards from sodium-water reaction, a SFR with the Brayton cycle using Supercritical Carbon dioxide (S-CO 2 ) as the working fluid can be an alternative approach to improve the current SFR design. However, the S-CO 2 Brayton cycle is more sensitive to the critical point of working fluids than other Brayton cycles. This is because compressor work is significantly decreased slightly above the critical point due to high density of CO 2 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 CO 2 critical point. In other words, 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 can increase the efficiency. Therefore, changing the critical point of CO 2 can result in an improvement of the total cycle efficiency with the same cycle layout. A small amount of other gases can be added in order to change the critical point of CO 2 . The direction and range of the critical point variation of CO 2 depends on the mixed component and its amount. Several gases that show chemical stability with

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

Reguladores del Ciclo Celular y el Cáncer

Directory of Open Access Journals (Sweden)

Oscar Oliveros Garay

1997-01-01

Full Text Available La detención del ciclo celular normal comienza a ser entendida a través de la identificación y caracterización de los genes inhibidores de CDKs, cuyos productos se insertan dentro de las vías en las cuales están presentes las proteínas supresoras tumorales p53 y pRB.

An evaluation of thermodynamic solar plants with cylindrical parabolic collectors and air turbine engines with open Joule–Brayton cycle

International Nuclear Information System (INIS)

Ferraro, Vittorio; Marinelli, Valerio

2012-01-01

A performance analysis of innovative solar plants operating with cylindrical parabolic collectors and atmospheric air as heat transfer fluid in an open Joule–Brayton cycle, with and without intercooling and regeneration, is presented. The analysis was made for two operating modes of the plants: with variable air flow rate and constant inlet temperature to the turbine and with constant flow rate and variable inlet temperature to the turbine. The obtained results show a good performance of this type of solar plant, in spite of its simplicity; it seems able to compete well with other more complex plants operating with different heat transfer fluids. -- Highlights: ► Innovative CPS solar plants, operating with air in open Joule–Brayton cycle, are proposed. ► They are attractive for their simplicity and present interesting values of global efficiency. ► They seem able to compete well with other more complex solar plants.

Comparative thermodynamic performance of some Rankine/Brayton cycle configurations for a low-temperature energy application

Science.gov (United States)

Lansing, F. L.

1977-01-01

Various configurations combining solar-Rankine and fuel-Brayton cycles were analyzed in order to find the arrangement which has the highest thermal efficiency and the smallest fuel share. A numerical example is given to evaluate both the thermodynamic performance and the economic feasibility of each configuration. The solar-assisted regenerative Rankine cycle was found to be leading the candidates from both points of energy utilization and fuel conservation.

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

Science.gov (United States)

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.

The maximum power condition of the brayton cycle with heat exchange processes

International Nuclear Information System (INIS)

Jung, Pyung Suk; Cha, Jin Girl; Ro, Sung Tack

1985-01-01

The ideal brayton cycle has been analyzed with the heat exchange processes between the working fluid and the heat source and the sink while their heat capacity rates are constant. The power of the cycle can be expressed in terms of a temperature of the cycle and the heat capacity rate of the working fluid. There exists an optimum power condition where the heat capacity rate of the working fluid has a value between those of the heat source and the heat sink, and the cycle efficiency is determined by the inlet temperatures of the heat source and the sink. (Author)

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.

A organização do ensino fundamental em ciclos: algumas questões

Directory of Open Access Journals (Sweden)

Ocimar Munhoz Alavarse

2009-01-01

Full Text Available En el artículo son problematizados algunos de los aspectos relacionados a la organización de la educación básica en ciclos, partiéndose de iniciativas en materia de educación de redes públicas y de la literatura sobre el tema. La implantación de los ciclos, con diferencias de diversos órdenes, se ha intensificado con la Ley de Directrices y Bases de 1996 y se presenta como una alternativa a la organización de la enseñanza por grados y al fracaso escolar, especialmente por cuenta de las altas tasas de reprobación (repetición y del bajo rendimiento académico de los estudiantes brasileños, y también es acompañada por una fuerte resistencia y controversia. Desde la perspectiva de la democratización de la escuela, se enfoca los retos de la igualdad de resultados, como la profundización de la igualdad de oportunidades, lo que incluye la tensión sobre los años de estudio y la repetición de grado como expediente pedagógico, con énfasis en las metas educativas y las implicaciones pedagógicas que los ciclos impondrían. Sin embargo, si los ciclos no pueden ser asociados a la disminución de la calidad de la educación, se considera que, a pesar de su enorme potencial democrático, todavía no fueron alcanzados los objetivos propuestos con su adopción.

Counter flow induced draft cooling tower option for supercritical carbon dioxide Brayton cycle

Energy Technology Data Exchange (ETDEWEB)

Pidaparti, Sandeep R., E-mail: sandeep.pidaparti@gmail.com [Georgia Institute of Technology, George W. Woodruff School of Mechanical Engineering, Atlanta, GA 30332 (United States); Moisseytsev, Anton; Sienicki, James J. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Ranjan, Devesh, E-mail: devesh.ranjan@me.gatech.edu [Georgia Institute of Technology, George W. Woodruff School of Mechanical Engineering, Atlanta, GA 30332 (United States)

2015-12-15

Highlights: • A code was developed to investigate the various aspects of using cooling tower for S-CO{sub 2} Brayton cycles. • Cooling tower option to reject heat is quantitatively compared to the direct water cooling and dry air cooling options. • Optimum water conditions resulting in minimal plant capital cost per unit power consumption are calculated. - Abstract: A simplified qualitative analysis was performed to investigate the possibility of using counter flow induced draft cooling tower option to reject heat from the supercritical carbon dioxide Brayton cycle for advanced fast reactor (AFR)-100 and advanced burner reactor (ABR)-1000 plants. A code was developed to estimate the tower dimensions, power and water consumption, and to perform economic analysis. The code developed was verified against a vendor provided quotation and is used to understand the effect of ambient air and water conditions on the design of cooling tower. The calculations indicated that there exists optimum water conditions for given ambient air conditions which will result in minimum power consumption, thereby increasing the cycle efficiency. A cost-based optimization technique is used to estimate the optimum water conditions which will improve the overall plant economics. A comparison of different cooling options for the S-CO{sub 2} cycle indicated that the cooling tower option is a much more practical and economical option compared to the dry air cooling or direct water cooling options.

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.

Adaptability of Brayton cycle conversion systems to fast, epithermal and thermal spectrum space nuclear reactors

International Nuclear Information System (INIS)

Tilliette, Z.P.

1988-01-01

The two French Government Agencies C.N.E.S. (Centre National d'Etudes Spatiales) and C.E.A. (Commissariat a l'Energie Atomique) are carrying out joint preliminary studies on space nuclear power systems for future ARIANE 5 launch vehicle applications. The Brayton cycle is the reference conversion system, whether the heat source is a liquid metal-cooled (NaK, Na or Li) reactor or a gas-cooled direct cycle concept. The search for an adequate utilization of this energy conversion means has prompted additional evaluations featuring the definition of satisfactory cycle conditions for these various kinds of reactor concepts. In addition to firstly studied fast and epithermal spectrum ones, thermal spectrum reactors can offer an opportunity of bringing out some distinctive features of the Brayton cycle, in particular for the temperature conditioning of the efficient metal hydrides (ZrH, Li/sub 7/H) moderators. One of the purposes of the paper is to confirm the potential of long lifetime ZrH moderated reactors associated with a gas cycle and to assess the thermodynamical consequences for both Nak(Na)-cooled or gas-cooled nuclear heat sources. This investigation is complemented by the definition of appropriate reactor arrangements which could be presented on a further occasion

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.

CICLO ECONÓMICO Y MORA LEGAL EN EL SISTEMA FINANCIERO COSTARRICENSE

Directory of Open Access Journals (Sweden)

Marlon Yong Chacón

2013-12-01

Full Text Available 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 actividad económica y con el ciclo real y financiero y que, aun cuando el efecto de la reciente crisis fue similar en bancos estatales y privados, estos últimos adoptan más rápido medidas que reducen la mora contable.

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

International Nuclear Information System (INIS)

Epiney, A.; Mikityuk, K.; Chawla, R.; Alpy, N.; Haubensack, D.; Malo, J.Y.

2009-01-01

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)

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

International Nuclear Information System (INIS)

Rovira, Antonio; Muñoz-Antón, Javier; Montes, María José; Martínez-Val, José María

2013-01-01

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/c p 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/c p factor measured at the ideal gas condition should be as low as possible

Determinantes de las dotaciones para los deterioros de las inversiones crediticias: ciclo contable, ciclo económico, morosidad

OpenAIRE

Climent Serrano, Salvador

2015-01-01

Este trabajo estudia los determinantes de las dotaciones para provisiones del deterioro de créditos en las entidades de crédito españolas desde 1983 al segundo trimestre de 2013. Como determinantes resultan significativos, además de la morosidad, las provisiones genéricas, el margen de interés, la estacionalidad centrada en el cuarto trimestre y los periodos de crisis. Al ser un periodo extenso en el que la economía ha tenido hasta cuatro ciclos, se estudian cómo actúan los ...

A 4 K tactical cryocooler using reverse-Brayton machines

Science.gov (United States)

Zagarola, M.; Cragin, K.; McCormick, J.; Hill, R.

2017-12-01

Superconducting electronics and spectral-spatial holography have the potential to revolutionize digital communications, but must operate at cryogenic temperatures, near 4 K. Liquid helium is undesirable for military missions due to logistics and scarcity, and commercial low temperature cryocoolers are unable to meet size, weight, power, and environmental requirements for many missions. To address this need, Creare is developing a reverse turbo-Brayton cryocooler that provides refrigeration at 4.2 K and rejects heat at 77 K to an upper-stage cryocooler or through boil-off of liquid nitrogen. The cooling system is predicted to reduce size, weight, and input power by at least an order of magnitude as compared to the current state-of-the-art 4.2 K cryocooler. For systems utilizing nitrogen boil-off, the boil-off rate is reasonable. This paper reviews the design of the cryocooler, the key components, and component test results.

Multi-objective thermodynamic optimization of an irreversible regenerative Brayton cycle using evolutionary algorithm and decision making

OpenAIRE

Rajesh Kumar; S.C. Kaushik; Raj Kumar; Ranjana Hans

2016-01-01

Brayton heat engine model is developed in MATLAB simulink environment and thermodynamic optimization based on finite time thermodynamic analysis along with multiple criteria is implemented. The proposed work investigates optimal values of various decision variables that simultaneously optimize power output, thermal efficiency and ecological function using evolutionary algorithm based on NSGA-II. Pareto optimal frontier between triple and dual objectives is obtained and best optimal value is s...

Integration between direct steam generation in linear solar collectors and supercritical carbon dioxide Brayton power cycles

OpenAIRE

Coco Enríquez, Luis; Muñoz Antón, Javier; Martínez-Val Peñalosa, José María

2015-01-01

Direct Steam Generation in Parabolic Troughs or Linear Fresnel solar collectors is a technology under development since beginning of nineties (1990's) for replacing thermal oils and molten salts as heat transfer fluids in concentrated solar power plants, avoiding environmental impacts. In parallel to the direct steam generation technology development, supercritical Carbon Dioxide Brayton power cycles are maturing as an alternative to traditional Rankine cycles for increasing net plant efficie...

Concept Design for a High Temperature Helium Brayton Cycle with Interstage Heating and Cooling

Energy Technology Data Exchange (ETDEWEB)

Wright, Steven A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Vernon, Milton E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Pickard, Paul S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2013-12-01

The primary metric for the viability of these next generation nuclear power plants will be the cost of generated electricity. One important component in achieving these objectives is the development of power conversion technologies that maximize the electrical power output of these advanced reactors for a given thermal power. More efficient power conversion systems can directly reduce the cost of nuclear generated electricity and therefore advanced power conversion cycle research is an important area of investigation for the Generation IV Program. Brayton cycles using inert or other gas working fluids, have the potential to take advantage of the higher outlet temperature range of Generation IV systems and allow substantial increases in nuclear power conversion efficiency, and potentially reductions in power conversion system capital costs compared to the steam Rankine cycle used in current light water reactors. For the Very High Temperature Reactor (VHTR), Helium Brayton cycles which can operate in the 900 to 950 C range have been the focus of power conversion research. Previous Generation IV studies examined several options for He Brayton cycles that could increase efficiency with acceptable capital cost implications. At these high outlet temperatures, Interstage Heating and Cooling (IHC) was shown to provide significant efficiency improvement (a few to 12%) but required increased system complexity and therefore had potential for increased costs. These scoping studies identified the potential for increased efficiency, but a more detailed analysis of the turbomachinery and heat exchanger sizes and costs was needed to determine whether this approach could be cost effective. The purpose of this study is to examine the turbomachinery and heat exchanger implications of interstage heating and cooling configurations. In general, this analysis illustrates that these engineering considerations introduce new constraints to the design of IHC systems that may require

Thermodynamic analysis and optimization of a Closed Regenerative Brayton Cycle for nuclear space power systems

International Nuclear Information System (INIS)

Ribeiro, Guilherme B.; Braz Filho, Francisco A.; Guimarães, Lamartine N.F.

2015-01-01

Nuclear power systems turned to space electric propulsion differ strongly from usual ground-based power systems regarding the importance of overall size and mass. For propulsion power systems, size and mass are essential drivers that should be minimized during conception processes. Considering this aspect, this paper aims the development of a design-based model of a Closed Regenerative Brayton Cycle that applies the thermal conductance of the main components in order to predict the energy conversion performance, allowing its use as a preliminary tool for heat exchanger and radiator panel sizing. The centrifugal-flow turbine and compressor characterizations were achieved using algebraic equations from literature data. A binary mixture of Helium–Xenon with molecular weight of 40 g/mole is applied and the impact of the components sizing in the energy efficiency is evaluated in this paper, including the radiator panel area. Moreover, an optimization analysis based on the final mass of heat the exchangers is performed. - Highlights: • A design-based model of a Closed Brayton Cycle is proposed for nuclear space needs. • Turbomachinery efficiency presented a strong influence on the system efficiency. • Radiator area presented the highest potential to increase the system efficiency. • There is maximum system efficiency for each total mass of heat exchangers. • Size or efficiency optimization was performed by changing heat exchanger proportion.

Method for controlling start-up and steady state performance of a closed split flow recompression brayton cycle

Science.gov (United States)

Pasch, James Jay

2017-02-07

A method of resolving a balanced condition that generates control parameters for start-up and steady state operating points and various component and cycle performances for a closed split flow recompression cycle system. The method provides for improved control of a Brayton cycle thermal to electrical power conversion system. The method may also be used for system design, operational simulation and/or parameter prediction.

Ciclos climáticos e causas naturais das mudanças do clima

Directory of Open Access Journals (Sweden)

Marcos José de Oliveira

2018-01-01

Full Text Available A periódica mudança climática na Terra pode ser explicada por um número reduzido de fatores terrestres e astronômicos. Nas escalas anual/diária, o clima obedece aos movimentos de translação e de rotação. Ciclos climáticos de períodos médios (décadas/séculos/milênios relacionam-se a mudanças na radiação solar, provocadas pela influência de grandes planetas do Sistema Solar. As oscilações oceânicas (ordem decadal são possivelmente causadas por influências planetárias e lunares. Ciclos climáticos longos (dezenas a centenas de milhares de anos são causados por variações nos parâmetros da órbita da Terra (excentricidade, obliquidade e precessão. Eventos de impacto de grandes corpos no planeta e extinções em massa de espécies advêm de superciclos (dezenas de milhões de anos provocados pela oscilação vertical do Sistema Solar em relação ao plano galáctico. Tectonismo, vulcanismo e a evolução de supercontinentes exibem superciclos (centenas de milhões de anos induzidos pelo deslocamento do Sistema Solar ao redor do centro da Via Láctea e pela variação de raios cósmicos. Fatores astronômicos permeiam praticamente todas as ordens dos ciclos climáticos e atuam direta ou indiretamente nos processos bio-geo-oceânico-atmosféricos. Conclui-se que o clima na Terra é caracterizado por ciclos controlados astronomicamente pela Lua, o Sol, os planetas, o Sistema Solar e, até mesmo, a Galáxia.

Computer simulation of transitional process to the final stable Brayton cycle in magnetic refrigeration

International Nuclear Information System (INIS)

Numasawa, T.; Hashimoto, T.

1981-01-01

The final working cycle in the magnetic refrigeration largely depends on the heat transfer coefficient β in the system, the parameter γ of the heat inflow from the outer system to this cycle and the period tau of the cycle. Therefore, so as to make clear this dependence, the time variation of the Brayton cycle with β, γ and tau has been investigated. In the present paper the transitional process of this cycle and the dependence of the final cooling temperature of the heat load on β, γ and tau have all been shown. (orig.)

Las estrategias en el aprendizaje de las artes visuales en los estudiantes del I ciclo

OpenAIRE

De La Cruz Ormeño, Jhonny Robert

2017-01-01

El presente trabajo de investigación, tuvo como problema general: ¿Cuál es la relación entre las estrategias en el aprendizaje de las artes visuales en los estudiantes del I ciclo del Institución de Educación Superior Tecnológico Publico “Julio César Tello” Villa el Salvador 2016?. Además el objetivo general fue determinar la relación entre las estrategias y el aprendizaje de las artes visuales, de igual forma la muestra estuvo integrada por 100 estudiantes del I ciclo del Inst...

Brayton Isotope Power System, Design Integrity Checklist (BIPS-DIC)

Energy Technology Data Exchange (ETDEWEB)

Miller, L.G.

1976-06-10

A preliminary Failure Modes, Effects and Criticality Analysis (FMECA) for the BIPS Flight System (FS) was published as AiResearch Report 76-311709 dated January 12, 1976. The FMECA presented a thorough review of the conceptual BIPS FS to identify areas of concern and activities necessary to avoid premature failures. In order to assure that the actions recommended by the FMECA are effected in both the FS and the Ground Demonstration System (GDS), a checklist (the BIPS-DIC) was prepared for the probability of occurrence of those failure modes that rated highest in criticality ranking. This checklist was circulated as an attachment to AiResearch Coordination Memo No. BIPS-GDS-A0106 dated January 23, 1976. The Brayton Isotope Power System-Design Integrity Checklist (BIPS-DIC) has been revised and is presented. Additional entries have been added that reference failure modes determined to rank highest in criticality ranking. The checklist will be updated periodically.

Steady-state temperature distribution within a Brayton rotating unit operating in a power conversion system using helium-xenon gas

Science.gov (United States)

Johnsen, R. L.; Namkoong, D.; Edkin, R. A.

1971-01-01

The Brayton rotating unit (BRU), consisting of a turbine, an alternator, and a compressor, was tested as part of a Brayton cycle power conversion system over a side range of steady state operating conditions. The working fluid in the system was a mixture of helium-xenon gases. Turbine inlet temperature was varied from 1200 to 1600 F, compressor inlet temperature from 60 to 120 F, compressor discharge pressure from 20 to 45 psia, rotative speed from 32 400 to 39 600 rpm, and alternator liquid-coolant flow rate from 0.01 to 0.27 pound per second. Test results indicated that the BRU internal temperatures were highly sensitive to alternator coolant flow below the design value of 0.12 pound per second but much less so at higher values. The armature winding temperature was not influenced significantly by turbine inlet temperature, but was sensitive, up to 20 F per kVA alternator output, to varying alternator output. When only the rotational speed was changed (+ or - 10% of rated value), the BRU internal temperatures varied directly with the speed.

Advanced heat pump for the recovery of volatile organic compounds. Phase 1, Conceptual design of an advanced Brayton cycle heat pump for the recovery of volatile organic compounds: Final report

Energy Technology Data Exchange (ETDEWEB)

1992-03-01

Emissions of Volatile Organic Compounds (VOC) from stationary industrial and commercial sources represent a substantial portion of the total US VOC emissions. The ``Toxic-Release Inventory`` of The US Environmental Protection Agency estimates this to be at about 3 billion pounds per year (1987 estimates). The majority of these VOC emissions are from coating processes, cleaning processes, polymer production, fuel production and distribution, foam blowing,refrigerant production, and wood products production. The US Department of Energy`s (DOE) interest in the recovery of VOC stems from the energy embodied in the recovered solvents and the energy required to dispose of them in an environmentally acceptable manner. This Phase I report documents 3M`s work in close working relationship with its subcontractor Nuclear Consulting Services (Nucon) for the preliminary conceptual design of an advanced Brayton cycle heat pump for the recovery of VOC. Nucon designed Brayton cycle heat pump for the recovery of methyl ethyl ketone and toluene from coating operations at 3M Weatherford, OK, was used as a base line for the work under cooperative agreement between 3M and ODE. See appendix A and reference (4) by Kovach of Nucon. This cooperative agreement report evaluates and compares an advanced Brayton cycle heat pump for solvent recovery with other competing technologies for solvent recovery and reuse. This advanced Brayton cycle heat pump is simple (very few components), highly reliable (off the shelf components), energy efficient and economically priced.

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)

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

International Nuclear Information System (INIS)

Ribeiro, Guilherme B.; Guimaraes, Lamartine N.F.; Braz Filho, Francisco A.

2015-01-01

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)

Study on the coupling performance of a turboexpander compressor applied in cryogenic reverse Brayton air refrigerator

International Nuclear Information System (INIS)

Yang, Shanju; Chen, Shuangtao; Chen, Xingya; Zhang, Xingqun; Hou, Yu

2016-01-01

Highlights: • Numerical simulations on expansion and compression processes were carried out. • A coupling model was built based on analysis and simulation and verified by test. • Relations and interactions among coupling parameters were quantitatively described. • When T_0_C = 0.39 MPa, the cooling capacity of refrigerator reached 221 W at 129.6 K. - Abstract: A small cryogenic reverse Brayton air refrigerator with turboexpander compressor (TEC) is presented in this study. Because of stable process, simple matching between expander and brake blower, and easy regulation, a turboexpander with brake blower is usually used in small reverse Brayton refrigerator. However, a turboexpander with brake blower just consumes and wastes the output energy during the enthalpy drop. In contrast, the output energy of TEC is absorbed by its coupled compressor for recycling. Thus when employing a TEC, the reverse Brayton refrigerator will achieve lower refrigeration temperature, larger cooling capacity and more effective energy use. TEC overall performance, which has an important impact on the refrigerator thermal performance, is mainly determined by the coupling between expander and compressor. In a TEC, the compressor and expander should seek balance among energy, rotating speed, mass flow rate and pressure, though restricted by individual working characteristics. The coupling relations among compressor efficiency, expander efficiency, compressor pressure ratio and expander expansion ratio are quite complex. In this study, theoretical coupling analysis between expander and compressor was conducted. The aerodynamic performances of compressor and expander were calculated using CFX simulation with SST model. The performance curves of compressor and expander were obtained through simulation results, which were validated by experimental data. Based on the coupling analysis and numerical simulations, the automatic coupling model between compression process and expansion process

Estudio termodinámico de una planta de ciclo combinado con turbina de gas y pre-diseño del HRSG

OpenAIRE

Martín Díaz, Carlos Daniel

2015-01-01

Dentro del gran alcance que se puede dar a los estudios de plantas de ciclos combinados, el presente estudio se centra en analizar un ciclo combinado convencional con turbina de gas, y en condiciones de diseño. En concreto, se trata de realizar un análisis termodinámico de un ciclo combinado en configuración monoeje 1x1 con recalentamiento y tres niveles de presión, con turbina de gas refrigerada por sistema vapor-aire y posteriormente un análisis de transferencia de calor en los intercamb...

Promising designs of compact heat exchangers for modular HTRs using the Brayton cycle

International Nuclear Information System (INIS)

Pra, Franck; Tochon, Patrice; Mauget, Christian; Fokkens, Jan; Willemsen, Sander

2008-01-01

The presented study was carried out within the Work Package 2 'Recuperator' of the High Temperature Reactor-E European program. High Temperature gas cooled Reactor concepts with a direct cycle have become potentially interesting for the future. Theoretically, these concepts provide higher efficiency than a classical steam cycle. Within the Brayton cycle the helium/helium recuperator, required to achieve the high efficiency, has to work under very harsh conditions (temperature, pressure, and pressure difference between circuits). Within the project the most promising technologies for the compact recuperator were investigated. First, the requirements for the recuperator to operate under the direct Brayton cycle have been defined. Based on these requirements the various potential technologies available on the market have been investigated. Two particular technologies (HEATRIC Printed Circuit Heat Exchanger, NORDON plate fin concept) have been selected as most promising. For the former, a precise description has been given and a mock-up has been fabricated and tested in the Claire loop at CEA. In the Claire loop the Printed Circuit Heat Exchanger mock-up has been subjected to thermal shocks, which are considered to be representative for a recuperator. Prior to the experimental testing coupled Computational Fluid Dynamic (CFD) and Finite Element analyses have been performed to give insight into the thermal and mechanical behaviour of the mock-ups during the thermal shock. Based on these results the experimental measuring program has been optimized. Upon completion of the tests the experimental and numerical results have been compared. Based on the results from the investigation performed recommendations are given for the full-size recuperator using the selected technologies

Validation of the CATHARE2 code against experimental data from Brayton-cycle plants

International Nuclear Information System (INIS)

Bentivoglio, Fabrice; Tauveron, Nicolas; Geffraye, Genevieve; Gentner, Herve

2008-01-01

In recent years the Commissariat a l'Energie Atomique (CEA) has commissioned a wide range of feasibility studies of future-advanced nuclear reactors, in particular gas-cooled reactors (GCR). The thermohydraulic behaviour of these systems is a key issue for, among other things, the design of the core, the assessment of thermal stresses, and the design of decay heat removal systems. These studies therefore require efficient and reliable simulation tools capable of modelling the whole reactor, including the core, the core vessel, piping, heat exchangers and turbo-machinery. CATHARE2 is a thermal-hydraulic 1D reference safety code developed and extensively validated for the French pressurized water reactors. It has been recently adapted to deal also with gas-cooled reactor applications. In order to validate CATHARE2 for these new applications, CEA has initiated an ambitious long-term experimental program. The foreseen experimental facilities range from small-scale loops for physical correlations, to component technology and system demonstration loops. In the short-term perspective, CATHARE2 is being validated against existing experimental data. And in particular from the German power plants Oberhausen I and II. These facilities have both been operated by the German utility Energie Versorgung Oberhausen (E.V.O.) and their power conversion systems resemble to the high-temperature reactor concepts: Oberhausen I is a 13.75-MWe Brayton-cycle air turbine plant, and Oberhausen II is a 50-MWe Brayton-cycle helium turbine plant. The paper presents these two plants, the adopted CATHARE2 modelling and a comparison between experimental data and code results for both steady state and transient cases

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

International Nuclear Information System (INIS)

Chang H. Oh

2006-01-01

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 state-of-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

Regenerator optimization of a Closed Brayton Cycle via entropy generation minimization

International Nuclear Information System (INIS)

Araújo, Élvis Falcão de; Ribeiro, Guilherme Borges; Guimarães, Lamartine N. F.

2017-01-01

This paper aims the numerical study of the heat transfer and fluid flow of a Closed Brayton Cycle (CBC) regenerator that is part of TERRA microreactor. This regenerator consists in a cross flow heat exchanger, where heat transfer occurs between internal fluid flow in radial tubes and external fluid flow passing perpendicularly to the tubes, which are disposed in a symmetrical cylindrical set where the number of tubes in the axial and radial directions can vary. In the simulations, mass flow inlet is varied for a fixed geometry. The fluid flow solution is provided by a commercial CFD solver and the entropy generation number calculation is later computed for optimization purposes. As a result, the entropy minimization method provides the regenerator configuration that enables the highest energy conversion efficiency. (author)

Design and fabrication of gas bearings for Brayton cycle rotating unit

Science.gov (United States)

Frost, A.; Tessarzik, J. M.; Arwas, E. B.; Waldron, W. D. (Editor)

1973-01-01

Analysis, design, and testing of two types of pivoted pad journal bearings and a spiral-grooved thrust bearing suitable for direct installation into the NASA 2 to 15 KW Brayton Cycle Rotating Unit (BRU) have been accomplished. Both types of tilting pad bearing assemblies are of the preloaded type, consisting of three pads with one pad flexibly mounted. One type utilizes a non-conforming pivot, while the other replaces the conventional spherical pivot with a cruciform flexible member. The thrust bearing is flexure mounted to accommodate static machine mislinement. Test results indicate that both types of journal bearings should satisfy the requirements imposed by the BRU. Hydrostatic tests of the spiral-grooved thrust bearing showed it to be free of pneumatic hammer with as many as 24 orifices over the BRU pressure and load range.

Regenerator optimization of a Closed Brayton Cycle via entropy generation minimization

Energy Technology Data Exchange (ETDEWEB)

Araújo, Élvis Falcão de; Ribeiro, Guilherme Borges; Guimarães, Lamartine N. F., E-mail: falcao@ieav.cta.br, E-mail: gbribeiro@ieav.cta.br, E-mail: guimarae@ieav.cta.br [Instituto de Estudos Avançacados (IEAv), São José dos Campos, SP (Brazil). Div. de Energia Nuclear

2017-07-01

This paper aims the numerical study of the heat transfer and fluid flow of a Closed Brayton Cycle (CBC) regenerator that is part of TERRA microreactor. This regenerator consists in a cross flow heat exchanger, where heat transfer occurs between internal fluid flow in radial tubes and external fluid flow passing perpendicularly to the tubes, which are disposed in a symmetrical cylindrical set where the number of tubes in the axial and radial directions can vary. In the simulations, mass flow inlet is varied for a fixed geometry. The fluid flow solution is provided by a commercial CFD solver and the entropy generation number calculation is later computed for optimization purposes. As a result, the entropy minimization method provides the regenerator configuration that enables the highest energy conversion efficiency. (author)

Potential performance improvement using a reacting gas (nitrogin tetroxide) as the working fluid in a closed Brayton cycle

Science.gov (United States)

Stochl, R. J.

1979-01-01

The results of an analysis to estimate the performance that could be obtained by using a chemically reacting gas (nitrogen tetroxide) as the working fluid in a closed Brayton cycle are presented. Compared with data for helium as the working fluid, these results indicate efficiency improvements from 4 to 90 percent, depending on turbine inlet temperature, pressures, and gas residence time in heat transfer equipment.

Ocorrência e comportamento ambiental de resíduos de antibióticos de uso veterinário

OpenAIRE

Rafael Marques Pereira Leal

2012-01-01

Muitos antibióticos de uso veterinário não são totalmente metabolizados no organismo animal, ocasionando a presença de resíduos destes compostos em várias matrizes ambientais, tais como estercos animais, solos e sedimentos fluviais. A ocorrência destes resíduos no ambiente pode favorecer a resistência de microrganismos aos agentes antibióticos, ocasionar problemas de ordem toxicológica em determinados organismos e, além disso, interferir nos ciclos biogeoquímicos mediados por microrganismos. ...

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

Directory of Open Access Journals (Sweden)

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

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.

Síntesis del estado del conocimiento del ciclo de carbono en ecosistemas boscosos de los Estados Unidos

Science.gov (United States)

Michael G. Ryan; Mark E. Harmon; Richard A. Birdsey; Christian P. Giardina; Linda S. Heath; Richard A. Houghton; Robert B. Jackson; Duncan C. McKinley; James F. Morrison; Brian C. Murray; Diane E. Pataki; Kenneth E. Skog

2010-01-01

Los bosques juegan un papel central en el ciclo de carbono de los Estados Unidos y global. El secuestro de carbono de los bosques de los Estados Unidos, a través de su crecimiento y la cosecha de productos madereros, compensa en la actualidad entre un 12 y un 19% de las emisiones de carbono asociadas al uso de combustible fósil de dicho país. El ciclo natural de un...

Environmental analysis of natural gas life cycle; Analisi ambientale del ciclo di vita del gas naturale

Energy Technology Data Exchange (ETDEWEB)

Riva, A.; D' Angelosante, S.; Trebeschi, C. [Snam SpA, Rome (Italy)

2000-12-01

Life Cycle Assessment is a method aimed at identifying the environmental effects connected with a given product, process or activity during its whole life cycle. The evaluation of published studies and the application of the method to electricity production with fossil fuels, by using data from published databases and data collected by the gas industry, demonstrate the importance and difficulties to have reliable and updated data required for a significant life cycle assessment. The results show that the environmental advantages of natural gas over the other fossil fuels in the final use stage increase still further if the whole life cycle of the fuels, from production to final consumption, is taken into account. [Italian] L'analisi del ciclo di vita e' una metodologia che consente di identificare gli effetti ambientali associati ad un prodotto, processo o attivita' lungo il loro ciclo di vita. La valutazione di studi pubblicati e l'applicazione della metodologia alla produzione di energia elettrica da combustibili fossili, utilizzando dati provenienti da banche dati di letteratura e raccolti dall'industria del gas, dimostrano l'importanza e la difficolta' di avere a disposizione dati affidabili ed aggiornati, necessari per un'analisi significativa del ciclo di vita. I risultati mostrano che i vantaggi ambientali del gas naturale rispetto agli altri combustibili fossili nella fase di utilizzo finale, aumentano ulteriormente se si considera l'intero ciclo di vita dei diversi combustibili, dalla produzione al consumo finale.

Transient Model of a 10 MW Supercritical CO{sub 2} Brayton Cycle for Light Water Reactors by using MARS Code

Energy Technology Data Exchange (ETDEWEB)

Park, Joo-Hyun; Park, Hyun Sun; Kim, Moo Hwan [POSTECH, Pohang (Korea, Republic of); Bae, Sung Won; Cha, Jae-Eun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

In this study, recuperation cycle was chosen as a reference loop design and the MARS code was chosen as the transient cycle analysis code. Cycle design condition is focus on operation point of the light-water reactor. Development of a transient model was performed for 10MW-electron SCO{sub 2} coupled with light water reactors. In order to perform transient analysis, cycle transient model was developed and steady-state run was performed and presented in the paper. In this study, the transient model of SCO{sub 2} recuperation Brayton cycle was developed and implemented in MARS to study the steady-state simulation. We performed nodalization of the transient model using MARS code and obtained steady-state results. This study is shown that the supercritical CO{sub 2} Brayton cycle can be used as a power conversion system for light water reactors. Future work will include transient analysis such as partial road operation, power swing, start-up, and shutdown. Cycle control strategy will be considered for various control method.

Ciclo de vida de Pellaea ternifolia (Cav. Link subsp. ternifolia (Pteridaceae-Polypodiidae

Directory of Open Access Journals (Sweden)

Jorge Huerta-Zavala

2015-08-01

Full Text Available Se describe el ciclo de vida dePellaea ternifolia(Cav. Link subsp.ternifolia. Los especímenes fueron recolectados en un bosque dePinusperturbado en San Miguel de los Alcanfores, municipio de Tlaxco, Tlaxcala, México. Las esporas fueron sembradas en vasos de unicel de 262 ml con cerámica (barro molido, piedra de río, tela de mosquitero y tres soportes de cultivo (tierra, maquique y musgo, todo previamente esterilizado y cerrado con plástico y alambre de cobre. El ciclo fue isospórico con desarrollo del protalo tipoAdiantum. En la fase cordada se apreciaron gametófitos con anteridios y arquegonio en una proporción cercana al 70% y el otro 30% fueron gametófitos apogámicos. Los esporófitos jóvenes se obtuvieron a partir de los 63 días.

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

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...

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.

El ciclo menstrual en el siglo XXI. Entre el mercado, la ecología y el poder femenino

Directory of Open Access Journals (Sweden)

Karina Felitti

Full Text Available Resumen: Este artículo analiza las concepciones relativas al género, la sexualidad, la salud, la espiritualidad/religiosidad, la política, el medio ambiente y el empoderamiento femenino, presentes en el mercado de productos "alternativos" que atienden y celebran el ciclo menstrual en la Argentina contemporánea. Se trata de un estudio cualitativo basado en el análisis de páginas web, blogs y perfiles de Facebook de mujeres que fabrican, comercializan y/o difunden toallas de tela y copas de silicona; la observación participante en talleres sobre el ciclo y entrevistas personales con sus organizadoras. El estudio visibiliza la emergencia y difusión de visiones que celebran el ciclo menstrual, considerándolo una fuente de identidad y empoderamiento femenino, y las tensiones que se dan con otros enfoques que cuestionan estas premisas.

Sensibilidade as catecolaminas dos atrios direitos das ratas : influencia das fases do ciclo estral e do "stress"

OpenAIRE

Monica Luiza Viegas Rodrigues

1993-01-01

Resumo: Os objetivos deste trabalho foram: analisar a sensibilidade ao efeito cronotrópico da isoprenalina, noradrenalina e adrenalina de átrios direitos isolados de ratas normais, em cada uma das fases do ciclo estral, ou após 50 minutos de natação, durante o estro ou o diestro; correlacionar as alterações de sensibilidade com as fases do ciclo estral e/ou com os níveis plasmáticos de corticosterona. Utilizamos ratas adultas, Wistar, normais, sedentárias, ou imediatamente após 50 min de nata...

Ciclo Hápticos: Para Quinteto de Sopros

Directory of Open Access Journals (Sweden)

Jorge Luiz de Lima Santos

2016-06-01

Full Text Available Memorial e partitura de Ciclo Hápticos, escrita em 2014 para quinteto de sopros. O memorial descreve brevemente as ferramentas metodológicas empregadas para o planejamento e criação da obra. De um lado, para produção do material melódico-harmônico foi empregado o Sistema-Gr de composição musical, desenvolvido por Carlos Almada (2014. Do outro lado, para organização formal, utilizamos o software Partitions - que faz parte do conjunto de programas do Parsemat, elaborado por Pauxy Gentil-Nunes (2009 – o qual informa o conjunto total de possibilidades de partições de um dado número.

Thermo-economic performance of HTGR Brayton power cycles

International Nuclear Information System (INIS)

Linares, J. L.; Herranz, L. E.; Moratilla, B. Y.; Fernandez-Perez, A.

2008-01-01

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)

Relación de tipo y ciclo vital familiar con la presencia de problemas psicosomáticos en un consultorio docente de medicina familiar

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Maria Cuba-Fuentes

2014-04-01

Full Text Available Objetivos: Determinar la relación entre el tipo de familia y el ciclo vital familiar con el desarrollo de problemas psicosomáticos en pacientes que acudieron al consultorio de medicina familiar. Material y métodos: Estudio observacional de corte transversal, en el que se revisaron las historias clínicas de un consultorio docente de medicina familiar y se buscó asociación entre el tipo de familia y ciclo vital familiar con el desarrollo de problemas psicosomáticos. Resultados: Se encontró un mayor porcentaje de familias nucleares según el tipo familiar y en plataforma de despegue según el ciclo vital familiar, se encontró en un 41% del total de la muestra con al menos un problema psicosomático en la historia clínica. No se encontró asociación entre el tipo de familia y el ciclo vital familiar con el desarrollo de problemas psicosomáticos. Conclusiones: El desarrollo de problemas psicosomáticos en un consultorio docente de medicina familiar no está asociado con el tipo de familia ni con el ciclo vital familiar.

Ciclo estral: fisiología básica y estrategias para mejorar la detección de celos

OpenAIRE

Guáqueta, Humberto

2010-01-01

El entendimiento de los factores que regulan el ciclo estral de la vaca es un componente esencial del manejo reproductivo en las fincas ganaderas. El incremento en la utilización de mano de obra calificada y especialistas en reproducción, así como la implementación de programas de inseminación artificial, sincronización del ciclo estral y transferencia de embriones han venido acentuando esta necesidad. La alta incidencia de actividad de monta durante la noche y los cortos periodos de dura...

ASERRÍN DE PINO COMO SUSTRATO HIDROPÓNICO. I: VARIACIÓN EN CARACTERÍSTICAS FÍSICAS DURANTE CINCO CICLOS DE CULTIVO

Directory of Open Access Journals (Sweden)

Joel Pineda-Pineda

2012-01-01

tratamiento de 100 % aserrín. Estos tratamientos se evaluaron durante cinco ciclos continuos de cultivo con jitomate (30 meses. Al sustrato original y al final de cada ciclo se midieron porosidad total, volumen de partículas, capacidad de retención de humedad, capacidad de aireación y densidad aparente. Se encontró poca variación en la densidad aparente, pero la porosidad, la retención de humedad y la capacidad de aireación disminuyeron gradualmente durante los cinco ciclos de cultivo con jitomate. La capacidad de aireación fue la característica física que presentó mayor variación, mostrando valores por debajo del adecuado después de 24 meses de cultivo.

Abordagens comparativas de ciclos e de potenciais da termodinâmica: escolha racional ou pragmática?

OpenAIRE

Jojomar Lucena da Silva

2015-01-01

Talvez mais que a própria Mecânica, a Termodinâmica possui em seu interior uma grande diversidade de teorias, que se distinguem por motivos vários. Um modo de identificá-las é analisar como se organizam, reflexo da metodologia empregada ao construí-las. Em particular, a organização que Carnot, Thomson e Clausius conferiram à ciência do calor é do tipo sintética, baseada no poder heurístico de ciclos termodinâmicos. Por isso, tal formalismo é chamado de termodinâmica de ciclos. Por outro lado,...

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...

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.

Juros reais e ciclos reais brasileiros

Directory of Open Access Journals (Sweden)

Kanczuk Fabio

2002-01-01

Full Text Available Este artigo apresenta um modelo de equilíbrio geral dinâmico, construído para estudar a relação quantitativa entre flutuações nas taxas de juros reais e os ciclos reais da economia brasileira. Quando as firmas estão sujeitas a restrições de capital de giro, o modelo é consistente com as volatilidades cíclicas dos componentes das contas nacionais e com a natureza contracíclica dos juros reais. Simulações com regras de Taylor alternativas indicam como as estimações econométricas da curva IS dinâmica estão sujeitas à crítica de Lucas. O artigo apresenta sugestões de como o modelo de metas inflacionárias atualmente utilizado pelo Bacen deveria ser modificado para incorporar os resultados encontrados.

The closed Brayton cycle: An energy conversion system for near-term military space missions

Science.gov (United States)

Davis, Keith A.

The Particle Bed Reactor (PBR)-closed Brayton cycle (CBC) provides a 5 to 30 kWe class nuclear power system for surveillance and communication missions during the 1990s and will scale to 100 kWe and beyond for other space missions. The PBR-CBC is technically feasible and within the existing state of the art. The PBR-CBC system is flexible, scaleable, and offers development economy. The ability to operate over a wide power range promotes commonality between missions with similar but not identical power spectra. The PBR-CBC system mass is very competitive with rival nuclear dynamic and static power conversion and systems. The PBR-CBC provides growth potential for the future with even lower specific masses.

MECANISMOS DE MODULACION DE LA EXPRESION DEL FACTOR DE TRANSCRIPCION RUNX2 DURANTE EL CICLO CELULAR DE PREOSTEOBLASTOS

OpenAIRE

VARELA FIGUEROA, NELSON MIGUEL

2010-01-01

Runx2 regula el compromiso de linaje, la proliferación y la diferenciación de las células osteoprogenitoras. La regulación de los niveles de este factor de transcrpción, durante el ciclo celular de preosteoblastos, es considerada como uno de los aspectos críticos que modulan su función. Los antecedentes sugieren una estrecha relación entre el ciclo celular y la expresión del gen Runx2, pero existen varias interrogantes sobre los mecanismos y procesos que regulan las oscilacione...

EFEITO DE INTERMEDIÁRIOS DO CICLO DE KREBS SOBRE ALTERAÇÕES OXIDATIVAS INDUZIDAS POR DIFERENTES AGENTES OXIDANTES

OpenAIRE

Robson Luiz Puntel

2006-01-01

Dados recentes na literatura têm relatado que alguns intermediários do ciclo de Krebs podem agir como potentes antioxidantes, tanto in vitro, quanto in vivo, em diversos sistemas pró-oxidantes. Porém, o(s) mecanismo(s) através dos qual(is) os intermediários do ciclo de Krebs exercem suas atividades antioxidantes não são completamente entendidas. Considerando a escassez de dados in vitro na literatura a respeito do efeito desses intermediários durante situações de estresse oxidativo, o present...

Revisitando a teoria do ciclo do produto Revisiting the product cycle theory

Directory of Open Access Journals (Sweden)

Eneuton Pessoa

2007-08-01

Full Text Available Este artigo busca refletir sobre uma questão-chave que perpassa grande parte da literatura crítica à teoria do ciclo do produto: o que foi superado e o que permanece vivo nessa teoria. Após sistematizar o mecanismo básico do ciclo do produto, discutem-se algumas principais insuficiências apontadas e/ou sugeridas pela literatura. Argumenta-se que, se não mais se sustenta a hipótese de que a dinâmica das inovações e dos investimentos diretos externos responde à cronologia do ciclo de vida do produto, por outro lado, a hipótese de que as vantagens comparativas possuem um caráter dinâmico, cuja natureza e importância relativa se modificam ao longo do tempo, em resposta a mudanças nos condicionantes da produção, e conforme o estágio de desenvolvimento e complexidade do produto, permanece viva e mais atual do que nunca.This article aims to think about a key-question that involves the majority of the critic literature in respect to the product-cycle theory. What is over and what remains alive in this theory? After systematizing the basic mechanism of the product-cycle theory, it discusses some of its main insufficiencies, how it is appointed or suggested by the literature. Summarily, we argue that, if it is over the hypothesis which argues that the dynamics of innovations, and the foreign direct investments depends on the product life cycle chronology, on the other side, it remains alive and does up-to-date the hypothesis which argues that the comparative advantages have a dynamic character, which nature and relative account is modified along time in response to changes in the production conditions, in accordance to the product evolution and its complexity.

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.

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.

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.

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

International Nuclear Information System (INIS)

RA Wolf

2006-01-01

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

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.

Supercritical CO2 Brayton cycle compression and control near the critical point

International Nuclear Information System (INIS)

Wright, S. A.; Fuller, R.; Noall, J.; Radel, R.; Vernon, M. E.; Pickard, P. S.

2008-01-01

This report describes the supercritical compression and control issues, the analysis, and the measured test results of a small-scale supercritical CO 2 (S-CO 2 ) compression test-loop. The test loop was developed by Sandia and is described in a companion paper in this conference. The results of these experiments will for the first time evaluate and experimentally demonstrate supercritical compression and the required compressor inlet control approaches on an appropriate scale in a series of test loops at Sandia National Laboratories. The Sandia effort is focused on the main compressor of a supercritical Brayton loop while a separate DOE Gen lV program focus is on studying similar behavior in re-compression Brayton cycles that have dual compressors. One of the main goals of this program is to develop and demonstrate the ability to design, operate, and control the supercritical compression process near the critical point due to highly non-linear behavior near this point. This Sandia supercritical test-loop uses a 50 kW radial compressor to pump supercritical CO 2 (S-CO 2 ) through an orifice and through a water-cooled gas-chiller. At the design point the compressor flow rate is 3.5 kg/s, the inlet pressure is 7, 690 kPa, the pressure ratio is 1.8, the inlet temperature is 305 K, and the shaft speed is 75, 000 rpm. The purpose of the loop is to study the compression and control issues near the critical point. To study compression we intend to compare the design code predictions for efficiency and change in enthalpy (or pressure ratio / head) of the radial compressor with the measured results from actual tests. In the tests the inlet flow, temperature, and pressure, will be varied around the critical point of CO 2 (Tc=304.2 K, and Pc=7.377 MPa). To study control, the test loop will use a variety of methods including inventory control, shaft speed control, and cooling water flow rate, and cooling water temperature control methods to set the compressor inlet temperature

Corpos e ciclos da vida sanumá-yanomami

Directory of Open Access Journals (Sweden)

Sílvia Guimarães

2010-12-01

Full Text Available Esta etnografia sobre os Sanumá, subgrupo yanomami do alto rio Auaris, estado de Roraima, explora aspectos centrais de sua vasta e complexa cosmologia. Discute a noção de corpo e os ciclos de vida onde estados especiais devem ser observados no processo de construção da pessoa.This ethnography focuses on the Sanumá, a Yanomami subgroup located on the upper Auaris River, in the northernmost state of Roraima in Brazil. It explores central aspects of their vast and complex cosmology by discussing the concept of body and life cycles where special states related with the construction of the person must be observed.

Caracterização dos parâmetros de recozimento de aços totalmente processados para fins elétricos

OpenAIRE

Gebler, Sérgio Roberto

2000-01-01

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. A busca mundial pela redução do consumo de energia tem incitado os fabricantes de motores elétricos a procurar alternativas para aumentar o rendimento de seus produtos. Dentre as diversas variáveis que estão envolvidas no processo produtivo, merece destaque a influência exercida pelos parâmetros do ciclo de tratamento térmico a que são submetidos os aços utilizados na fabricação de rotores e estatores. A d...

Effect of geometrical shape of the working substance Gadolinium on the performance of a regenerative magnetic Brayton refrigeration cycle

International Nuclear Information System (INIS)

Diguet, Gildas; Lin, Guoxing; Chen, Jincan

2013-01-01

Based on Mean Field Theory (MFT), the entropy of magnetic material Gadolinium (Gd), which is a function of the local magnetic field and temperature, is calculated and analyzed. This local magnetic field is the sum of the applied field H 0 plus the exchange field H W =λM and the demagnetizing field H d =−NM, where the demagnetizing factor N depends on the shape of magnetic materials. Hereby, the impacts of the demagnetizing factor N on the magnetic entropy, magnetic entropy change and main thermodynamics performance of a regenerative magnetic Brayton refrigeration cycle using Gd as the working substance are investigated and evaluated in detail. The results obtained underline the importance of the shape of the working substance used in magnetic refrigerators for room-temperature application; elongated materials provide better thermodynamics performance such as higher COP and net heat absorption. It is pointed out that for low external fields, the magnetic refrigerator ceased to be functional if flat materials were used. - Highlights: ► Gd entropy is calculated as a function of temperature and internal magnetic field. ► Magnetic Brayton cycle properties generally depend on the demagnetizing factor. ► Redundant heat transfer is highly sensitive to the demagnetizing factor. ► The net cooling quantity is highly sensitive to the demagnetizing factor. ► Coefficient of performance is dependant to the magnetic material shape.

Thermal performance analysis of Brayton cycle with waste heat recovery boiler for diesel engines of offshore oil production facilities

International Nuclear Information System (INIS)

Liu, Xianglong; Gong, Guangcai; Wu, Yi; Li, Hangxin

2016-01-01

Highlights: • Comparison of Brayton cycle with WHRB adopted in diesel engines with and without fans by thermal performance. • Waste heat recovery technology for FPSO. • The thermoeconomic analysis for the heat recovery for FPSO. - Abstract: This paper presents the theoretical analysis and on-site testing on the thermal performance of the waste heat recovery system for offshore oil production facilities, including the components of diesel engines, thermal boilers and waste heat boilers. We use the ideal air standard Brayton cycle to analyse the thermal performance. In comparison with the traditional design, the fans at the engine outlet of the waste heat recovery boiler is removed due to the limited space of the offshore platform. The cases with fan and without fan are compared in terms of thermal dynamics performance, energy efficiency and thermo-economic index of the system. The results show that the application of the WHRB increases the energy efficiency of the whole system, but increases the flow resistance in the duct. It is proved that as the waste heat recovery boiler takes the place of the thermal boiler, the energy efficiency of whole system without fan is slightly reduced but heat recovery efficiency is improved. This research provides an important guidance to improve the waste heat recovery for offshore oil production facilities.

Efecto de extractos de la esponja calcarea Leucetta aff. floridana sobre el ciclo de líneas celulares leucemoides

OpenAIRE

Diana Margarita Márquez Fernández; Mariano Eliecer Acosta Lobo; María Elena Márquez Fernández; Alejandro Martínez Martínez; Edna Judith Márquez Fernández; Mauricio Camargo Guerrero

2012-01-01

Introducción: la esponja Leucetta aff. floridana produce compuestos con actividad antiproliferativa diferencial en células tumorales de pulmón y mama, la cual no ha sido explorada en otras líneas tumorales y se desconoce si su potencial antiproliferativo está relacionado con la progresión de células a través del ciclo celular. Objetivo: evaluar el potencial antiproliferativo, anticlonogénico y el efecto sobre el ciclo celular de los extractos hexánico y metanólico de la esponja Leucetta aff. ...

Moeda, crédito e ciclos econômicos em Marshall

Directory of Open Access Journals (Sweden)

Sérgio Fornazier Meyrelles Filho

2016-03-01

Full Text Available Resumo Este artigo tem por objetivo examinar os elementos centrais da análise de Alfred Marshall sobre as flutuações cíclicas, contemplando o papel da especulação e do crédito nesse contexto. A primeira seção contém breve introdução ao assunto. A seguir, tratam-se das contribuições de Marshall sobre os determinantes das taxas de juros normal e de mercado, bem como a sua reformulação da Teoria Quantitativa da Moeda. Após, apresenta-se a sua explicação dos ciclos econômicos, na qual se articulam em uma mesma estrutura os elementos teóricos expostos nas seções anteriores. Ao final, uma comparação da teoria monetária de Marshall com as contribuições de Irving Fisher e Knut Wicksell é realizada, destacando-se os pontos de contato, bem como de distanciamento, entre esses proeminentes teóricos neoclássicos dos fenômenos monetários. Elabora-se ainda uma versão dinâmica formal do modelo marshalliano dos ciclos, incluída em apêndice.

Início da tuberização, duração do ciclo vegetativo e tolerância ao calor em genótipos de batata

Directory of Open Access Journals (Sweden)

Danilo Hottis Lyra

2015-07-01

Full Text Available Resumo: O objetivo deste trabalho foi avaliar a relação do tempo para o início da tuberização e da duração do ciclo vegetativo com a tolerância ao calor em batata. Grupos de clones com diferentes tempos para o início de tuberização e durações do ciclo vegetativo foram definidos e avaliados em dois ambientes, e seus índices morfofisiológicos foram estimados em condições de estresse de calor. A amplitude para o início da tuberização foi de 31,8 dias e para a duração do ciclo vegetativo de 30,3 dias. Os grupos de clones formados apresentaram os seguintes parâmetros: tuberização precoce e ciclo vegetativo curto, tuberização precoce e ciclo longo (PL, tuberização tardia e ciclo curto e tuberização tardia e ciclo longo. Em condições de estresse de calor, a produção de tubérculos graúdos do grupo PL apresentou média superior à dos demais grupos. Seis clones (IRF 10-24, IRF 7-61, IRF 2-71, IRF 2-14, IRF 6-104 e IRF 10-44 e três testemunhas ('Markies', CBM 16-16 e CBM 9-10 foram considerados tolerantes ao estresse de calor (média diária de 21,2ºC e responderam favoravelmente ao ambiente com temperaturas amenas (média diária de 19,0ºC. A partição de matéria seca para os tubérculos foi mais rápida nos clones do grupo PL. Os clones de tuberização precoce e ciclo vegetativo longo apresentaram maior tolerância ao calor, com maior produção de tubérculos do que os demais grupos.

Equilíbrio e ciclos Equilibrium and cycles

Directory of Open Access Journals (Sweden)

Matheus Albergaria de Magalhães

2005-12-01

Full Text Available A agenda de pesquisa relacionada a modelos de ciclos reais de negócios (Real-Business-Cycle models - RBC apresentou um crescimento exponencial desde seu surgimento, no início da década de 1980. Os modelos iniciais do gênero partiam de economias simplificadas, sem imperfeições, buscando explicar as oscilações de curto prazo da economia (ciclos a partir de um arcabouço de equilíbrio geral walrasiano. Atualmente, modelos RBC são amplamente usados na macroeconomia, com uma ênfase especial na análise dos aspectos quantitativos das flutuações econômicas. O objetivo do presente artigo é, portanto, realizar uma resenha da primeira fase da agenda RBC. Apesar dos diversos resultados controversos obtidos, é provável que a principal contribuição dessa agenda seja de cunho metodológico, uma vez que a pesquisa daí advinda afetou profundamente as formas de modelagem macroeconômica vigentes hoje em dia.The research agenda related to Real-Business-Cycle models (RBC has shown a remarkable growth since its beginning, in the eighties. The first models of this kind departed from simple economies without imperfections and tried to explain short-run macroeconomic movements (cycles from Walrasian general-equilibrium settings. Nowadays, RBC models are widely used in Macroeconomics, with a special emphasis on the quantitative aspects of economic fluctuations. The main goal of this paper is to provide a survey of the first stage of the RBC research agenda, since there is not a systematic survey of this literature available in Portuguese. Although there are several controversial results related to RBC models, its main contribution seems to be methodological, since these models had a profound impact on current macroeconomic modeling.

Principios termodinámicos de la refrigeración magnética

OpenAIRE

JOHN HOYOS; FARID CHEJNE; CÉSAR CHAVES; JUAN VELÁSQUEZ; ALAN HILL

2006-01-01

La Refrigeración magnética es una de las tecnologías con mayor potencial comercial debido a sus ventajas ambientales y energéticas frente a los sistemas convencionales. Este artículo presenta los aspectos termodinámicos más importantes del efecto magnetocalórico, fundamental en el estudio de las transformaciones magnéticas y el desarrollo de la refrigeración magnética. También se explican los ciclos magnéticos de Carnot, Brayton y de Regeneración Magnética Activa aplicados a la refrigeración ...

Un modelo postkeynesiano simple de inestabilidad financiera y ciclos

OpenAIRE

Óscar de Juan Asenjo; Josep González Calvet

2003-01-01

En este trabajo se examina la interacción entre el sector real de la economía (representado por la tasa de crecimiento) y el sector financiero (representado por la tasa de interés). Se utiliza el modelo depredador-presa propuesto en 1926 por los científicos naturales Lotka y Volterra, que fue aplicado por primera vez al ámbito económico por Goodwin en 1967. A diferencia de los modelos convencionales del ciclo económico, cuyo punto de partida son las perturbaciones exógenas sobre la economía r...

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

International Nuclear Information System (INIS)

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 (sCO 2 ) 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 sCO 2 Brayton cycles, can be assessed as a retrofit measure for present light water reactors. Transient simulations are hereby of great importance. The heat removal system has to be modeled explicitly to account for the interaction between the system and the behavior of the plant during different accident conditions. As a first step, transport and thermodynamic fluid properties of supercritical carbon dioxide have been implemented in ATHLET to allow for the simulation of the new working fluid. Additionally, a heat transfer correlation has been selected to represent the specific heat transfer of supercritical carbon dioxide. For the calculation of pressure losses due to wall friction, an approach for turbulent single phase flow has been adopted that is already implemented in ATHLET. In a second step, a component model for radial compressors has been implemented in the system code. Furthermore, the available model for axial turbines has been adapted to simulate the transient behavior of radial turbines. All extensions have been validated against experimental data. In order to simulate the interaction between the self-propelling heat removal system and a generic boiling water reactor, the components of the sCO 2 Brayton cycle have been dimensioned with first principles. An available input deck of a generic BWR has then been extended by the residual heat removal system. The modeled application has shown that the extended version of ATHLET is suitable to simulate sCO 2 Brayton cycles and to evaluate the introduced heat removal system

Combined cycles, impacts of technological requirements; Ciclos combinados, impactos de requerimientos tecnologicos

Energy Technology Data Exchange (ETDEWEB)

Gonzalez Santalo, Jose Miguel [Instituto de Investigaciones Electricas, Temixco, Morelos (Mexico)

1999-07-01

The fundamental growth of the Mexican electrical sector for the next ten years is planned on base of the installation of 20 thousand Mw plants of combined cycle. This article presents an analysis of the impact of these power stations finding out that the power stations of combined cycle are at the moment cheaper - from 600 to 700 dollars by installed kW- than the alternative coal options or fuel oil, that are in the range of 900 to 1200 dollars per kW, in addition to which the time required for their construction is shorter. [Spanish] El crecimiento fundamental del sector electrico mexicano para los proximos diez anos esta planeado con base en la instalacion de 20 mil Mw de plantas de ciclo combinado. Este articulo presenta un analisis del impacto de dichas centrales encontrando que las centrales de ciclo combinado actualmente resultan mas baratas - de 600 a 700 dolares por kW instalado - que las opciones alternativas de carbon o combustoleo que estan en el rango de 900 a 1200 dolares por kW, ademas de que los tiempos requeridos para su construccion son menores.

Ciclo del carbono y clima: la perspectiva geológica

OpenAIRE

Martín Chivelet, Javier

2010-01-01

El ciclo del carbono aglutina los almacenes de ese elemento en el sistema Tierra (litosfera, hidrosfera, biosfera, atmósfera y rizosfera) y los flujos que se producen entre ellos. Las capacidades de esos almacenes y las tasas de intercambio entre ellos son extraordinariamente diversas por lo que, según la escala temporal considerada, encontraremos diferentes “ciclos” del carbono. A escalas temporales de millones de años, los flujos son lentos y se producen entre la litosfera y el “sistema de ...

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.

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.

1988-11-01

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.

Conceptual design study of closed Brayton cycle gas turbines for fusion power generation

International Nuclear Information System (INIS)

Kuo, S.C.

1976-01-01

A conceptual design study is presented of closed Brayton cycle gas turbine power conversion systems suitable for integration with advanced-concept Tokamak fusion reactors (such as UWMAK-III) for efficient power generation without requiring cooling water supply for waste heat rejection. A baseline cycle configuration was selected and parametric performance analyses were made. Based on the results of the parametric analysis and trade-off and interface considerations, the reference design conditions for the baseline cycle were selected. Conceptual designs were made of the major helium gas turbine power system components including a 585-MWe single-shaft turbomachine, (three needed), regenerator, precooler, intercooler, and the piping system connecting them. Structural configuration and significant physical dimensions for major components are illustrated, and a brief discussion on major advantages, power control and crucial technologies for the helium gas turbine power system are presented

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. 

Relação Hipsométrica para Pinus taeda L. em Diferentes Fases do Ciclo de Corte

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Marcos Felipe Nicoletti

Full Text Available RESUMO O objetivo deste estudo foi avaliar as diferentes etapas do ciclo de corte, buscando uma relação hipsométrica adequada para estimar alturas dessas diferentes fases em um reflorestamento de Pinus taeda. Foram realizados cinco tratamentos, sendo o quinto a junção dos dados pertencentes aos demais tratamentos (modelo reduzido. A amostragem seguiu o método de área fixa, no qual o tamanho das parcelas e o número de árvores dominantes diferenciaram-se nos ciclos de corte. Definiu-se a localização das parcelas através de amostragem aleatória simples (oito parcelas por ciclo de corte. Foram determinadas as estatísticas de ajustes, coeficiente de determinação ajustado, erro-padrão e análise de resíduos. Efetuou-se o teste de identidade de Graybill para verificação da necessidade da utilização de diferentes modelos para distintas classes de idade. Os resultados comprovaram que existem diferenças significativas entre adotar-se um modelo específico para cada fase e utilizar um único melhor modelo para o povoamento total.

ANÁLISE DOS CICLOS DE PRECIPITAÇÃO NA REGIÃO DE BOA VISTA - RR NOS ANOS DE 1910 A 2014

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Danielle Alves Silva

2015-12-01

Full Text Available Este estudo buscou relacionar e identificar a influência dos fenômenos ENOS nos índices de precipitação da série histórica (1910 a 2014 da estação pluviométrica de Boa Vista, Capital do Estado de Roraima, Brasil. Os procedimentos metodológicos compreenderam: a análises estatísticas dos dados diários, mensais e anuais para definição da série pluviométrica identificação de diferentes ciclos pluviométricos; b identificação e confrontação dos dados pluviométricos com os períodos de vigência dos fenômenos ENOS (El Niño e La Niña a fim de identificar relações destes com anomalias observadas na série histórica. A análise da série histórica permitiu a identificação de quatro ciclos pluviométricos, representados por dois ciclos secos e outros dois úmidos. Os eventos ENOS (El Niño e La Niña apresentaram grande compatibilidade com as variações pluviométricas da série. Os resultados apontam para a necessidade do estado e da sociedade civil se organizar aos efeitos dos ciclos de El Niño, em especial a retração do volume superficial de água disponível, estações secas mais fortes e ampliação de eventos de queimadas e, no caso dos ciclos de  La Niña, recorrência de cheias e eventos associados.

A organização escolar em ciclos e a questão da igualdade substantiva

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Marília Gouvea de Miranda

2009-01-01

Full Text Available El artículo discute algunos fundamentos de las propuestas de la organización escolar en ciclos y sus implicaciones, a partir de la comprensión de que la propuesta de ciclos necesita agregar un nuevo sentido de escuela al criterio de no reprobación, para afirmar su distinción delante de las propuestas de progresión continuada. Se pregunta: si la escuela debe cambiar, ¿cuáles son los principios que orientan este cambio en la perspectiva de la escuela de ciclos? El entendimiento es el de que el debate sobre estas políticas ni siempre presentan claramente al conjunto de principios que las fundamenta. Se propone, así, una discusión inicial acerca de la pertinencia de aludirse a la psicología como su principal referencia, pasando la cuestión considerada más determinante, que es la comprensión de los sentidos atribuidos a la educación escolar contemporánea, en la que se insiere el embate entre el discurso liberal de la igualdad, con sus variantes actuales en defensa de las diferencias, y el principio de la igualdad sustantiva. Se aborda la tendencia a la redefinición o hasta la supresión del principio de igualdad, lo que se expresa, predominantemente, (1 por la proposición de un "liberalismo igualitario", que tiende a sustituir igualdad por equidad, y (2 por la defensa de un principio de la diversidad como crítica al precepto de la igualdad. En contraposición a estas perspectivas, se destaca la igualdad sustantiva (Mészáros como un principio orientador general en el enfrentamiento de las desigualdades sociales. El artículo indica, así, la importancia de investigar como las propuestas de los ciclos se sitúan en relación a este embate.

Ciclo do Marketing Digital: tática e estratégia Blended

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Felipe Chibás Ortiz

2013-07-01

Full Text Available Este artigo discute sob o prisma relacional e processual a utilização da metodologia do Decálogo Digital, também conhecida como Ciclo do Marketing Digital elaborada pelo autor. No presente trabalho se justifica a necessidade de um sistema metodológico de trabalho prático e eficaz para a realização das campanhas de marketing que utilizam fundamentalmente os veículos disponíveis na Internet. Se fala das origens da pressente proposta fazendo um breve comparativo com os sistemas dos 4 Ps e os 8 Ps, Se apresentam algumas das diferenças das campanhas de marketing utilizando veículos presenciais e as que focam mais a utilização de mídias digitais,  se relacionam estes conteúdos com conceitos essenciais como os de estratégia, comunicação integrada, teoria dos inputs, throughputs e outputs, integração das mídias, marketing digital e responsável e gestão de redes virtuais. A seguir se define o Ciclo ou Decálogo do Marketing Digital e se explicam as etapas de trabalho com o sistema do Decálogo Digital responsável e se faz uma avaliação de suas possibilidades de aplicação na atualidade. Utilizou-se o método qualitativo, a revisão bibliográfica e o analise de documentos impressos e web, assim como as entrevistas em profundidade. O objetivo principal do presente trabalho é apresentar a proposta metodológica do Decálogo do Marketing Digital, também conhecida como Ciclo do Marketing Digital, mostrando as vantagens da utilização deste sistema de trabalho de caráter estratégico-operacional, para o profissional da comunicação.

Características vegetativas e seus efeitos sobre a produção de bananeira em três ciclos

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Lauro Saraiva Lessa

2012-12-01

Full Text Available A produtividade em bananeira é um caráter complexo que resulta da associação de diferentes fatores, influenciados pelo ambiente. Este trabalho teve por objetivo estudar os efeitos diretos e indiretos de características vegetativas sobre a produção de bananeira em três ciclos. O trabalho foi conduzido no campo experimental da Embrapa Acre, em Rio Branco, Acre, entre os anos de 2003 e 2006. Foram avaliados 13 genótipos de bananeira (Preciosa, Japira, Pacovan-Ken, Pacovan, BRS Platina, Prata-Anã, ST12-31, Nanicão, Grande Naine, Calipso, Ambrosia, Bucaneiro e FHIA-02, no espaçamento de 3 m x 2 m, no esquema de blocos ao acaso, com cinco repetições. Determinaram-se a altura de plantas, diâmetro do pseudocaule, número de folhas na floração e na colheita, peso do cacho e número de pencas no cacho. Realizou-se a análise de variância para cada ciclo e estimaram-se os coeficientes de correlação fenotípicos e os coeficientes de trilha. Adotou-se como variável básica o peso do cacho, e as demais, como variáveis explicativas. O estudo dos efeitos diretos e indiretos evidenciou que o caráter produção é bastante influenciado pelo ambiente no primeiro ciclo, e, nos ciclos seguintes, a produção é muito influenciada pelas características vegetativas, principalmente número de folhas na colheita.

Mecanismos do ciclo sono-vigília Sleep-wake cycle mechanisms

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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.

A treatment of thermal efficiency improvement in the Brayton cycle

International Nuclear Information System (INIS)

Fujii, Terushige; Akagawa, Koji; Nakanishi, Shigeyasu; Inoue, Kiyoshi; Ishigai, Seikan.

1982-01-01

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, NH 3 , SO 2 , CO 2 and H 2 O were examined as perfect gas and real gas. The advantage of CO 2 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.)

Preliminary closed Brayton cycle study for a space reactor application

International Nuclear Information System (INIS)

Guimaraes, Lamartine Nogueira Frutuoso; Carvalho, Ricardo Pinto de; Camillo, Giannino Ponchio

2007-01-01

The Nuclear Energy Division (ENU) of the Institute for Advanced Studies (IEAv) has started a preliminary design study for a Closed Brayton Cycle Loop (CBCL) aimed at a space reactor application. The main objectives of the study are to establish a starting concept for the CBCL components specifications, and to develop a demonstrative simulator of CBCL in nominal operation conditions. The ENU/IEAv preliminary design study is developing the CBCL around the NOELLE 60290 turbo machine. The actual nuclear reactor study is being conducted independently. Because of that, a conventional heat source is being used for the CBCL, in this preliminary design phase. This paper describes the steady state simulator of the CBCL operating with NOELLE 60290 turbo machine. In principle, several gases are being considered as working fluid, as for instance: air, helium, nitrogen, CO2 and gas mixtures such as helium and xenon. At this moment the simulator is running with Helium as the working fluid. Simplified models of heat and mass transfer are being developed to simulate thermal components. Future efforts will focus on keeping track of the modifications being implemented at the NOELLE 60290 turbo machine in order to build the CBCL. (author)

Preliminary closed Brayton cycle study for a space reactor application

Energy Technology Data Exchange (ETDEWEB)

Guimaraes, Lamartine Nogueira Frutuoso; Carvalho, Ricardo Pinto de [Institute for Advanced Studies, Sao Jose dos Campos, SP (Brazil)]. E-mail: guimarae@ieav.cta.br; Camillo, Giannino Ponchio [Instituto Tecnologico de Aeronautica (ITA), Sao Jose dos Campos, SP (Brazil)]. E-mail: gianninocamillo@gmail.com

2007-07-01

The Nuclear Energy Division (ENU) of the Institute for Advanced Studies (IEAv) has started a preliminary design study for a Closed Brayton Cycle Loop (CBCL) aimed at a space reactor application. The main objectives of the study are to establish a starting concept for the CBCL components specifications, and to develop a demonstrative simulator of CBCL in nominal operation conditions. The ENU/IEAv preliminary design study is developing the CBCL around the NOELLE 60290 turbo machine. The actual nuclear reactor study is being conducted independently. Because of that, a conventional heat source is being used for the CBCL, in this preliminary design phase. This paper describes the steady state simulator of the CBCL operating with NOELLE 60290 turbo machine. In principle, several gases are being considered as working fluid, as for instance: air, helium, nitrogen, CO2 and gas mixtures such as helium and xenon. At this moment the simulator is running with Helium as the working fluid. Simplified models of heat and mass transfer are being developed to simulate thermal components. Future efforts will focus on keeping track of the modifications being implemented at the NOELLE 60290 turbo machine in order to build the CBCL. (author)

Una revisión crítica de las técnicas de filtrado para la teoría de los ciclos económicos reales

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Lopera Sierra John Fernando

2010-12-01

Full Text Available Este artículo presenta una revisión de diferentes investigaciones con respecto a dos elementos básicos de la teoría de los ciclos económicos reales: los factores que determinan los ciclos económicos y las técnicas de filtrado (estadísticas o económicas que permiten estimarlos. El trabajo concluye, al igual que otros estudios, que cuando se utilizan diferentes técnicas de filtrado es posible encontrar distintos hechos estilizados, lo cual condiciona las interpretaciones sobre los factores que determinan los ciclos.

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

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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

Desempenho anaeróbico lático e aeróbico de mulheres com ciclo menstruai ovulatório

OpenAIRE

Ribeiro, Cléo Pereira

2013-01-01

Este trabalho analisou o comportamento das potências anaeróbica lática e aeróbica durante as fases folicular e lútea do ciclo menstruai. O exercício físico induz respostas semelhantes entre os sexos. Entretanto, a mulher sofre flutuações significativas nos caminhos fisiológicos, uma vez que seus hormônios não são secretados continua­mente durante o mês. Esse padrão rítmico é conhecido por ciclo feminino ou menstruai: este apresenta duas fases - folicular e lútea. Alguns autores afirmam que du...

ARQUITECTURA DE LA RED VIRTUAL DE APRENDIZAJE PARA EL CICLO BÁSICO (FACES-UC

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Neyda Ibañez

2011-11-01

Full Text Available La sociedad del siglo XXI demanda una universidad adaptada a la nueva realidad que ofrece el desarrollo de la comunicación basada en la tecnología digital computarizada. En virtud de ello, la investigación tuvo como objetivo el diseñar la red virtual de aprendizaje para facilitadores y estudiantes del Ciclo Básico de la Facultad de Ciencias Económicas y Sociales de la Universidad de Carabobo (FaCES-UC, siendo este uno de los objetivos del proyecto LOCTI titulado Formación, capacitación y fortalecimiento a facilitadores del Ciclo Básico y de las Escuelas de FaCES-UC, en el manejo de entornos virtuales como herramientas de aprendizaje. Metodológicamente, el estudio se ubicó en el paradigma positivista de tipo descriptivo, con una población de 72 profesores, calculándose una muestra de 237 estudiantes, con muestreo aleatorio simple, utilizando la técnica de observación directa y aplicando como instrumento el cuestionario simple con 27 preguntas cerradas y dicotómicas. Los resultados arrojaron que más del 95 por ciento de los estudiantes y más del 37 por ciento de los profesores aportaron al diseño de la red virtual de aprendizaje. Se concluye la arquitectura del sitio Web a través de la clasificación de tres criterios que persiguen brindar a la comunidad tanto interna como externa a la Universidad de Carabobo, un portal que ofrezca y difunda información y servicios del Ciclo Básico de FaCES-UC y de sus diversas Cátedras que lo conforman.

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

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

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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

Brayton cycle for internal combustion engine exhaust gas waste heat recovery

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J Galindo

2015-06-01

Full Text Available An average passenger car engine effectively uses about one-third of the fuel combustion energy, while the two-thirds are wasted through exhaust gases and engine cooling. It is of great interest to automotive industry to recover some of this wasted energy, thus increasing the engine efficiency and lowering fuel consumption and contamination. Waste heat recovery for internal combustion engine exhaust gases using Brayton cycle machine was investigated. The principle problems of application of such a system in a passenger car were considered: compressor and expander machine selection, machine size for packaging under the hood, efficiency of the cycle, and improvement of engine efficiency. Important parameters of machines design have been determined and analyzed. An average 2-L turbocharged gasoline engine’s New European Driving Cycle points were taken as inlet points for waste heat recovery system. It is theoretically estimated that the recuperated power of 1515 W can be achieved along with 5.7% improvement in engine efficiency, at the point where engine power is 26550 W.

Ciclos biogeoquímicos como subsídio para a sustentabilidade do sistema agroindustrial da cana-de açúcar

OpenAIRE

Barbosa, Valmir [UNESP

2007-01-01

O crescimento da cultura da cana-de-açúcar, frente à demanda global por energia renovável, provoca preocupações quanto à sua sustentabilidade. Nesse contexto, o objetivo deste trabalho é oferecer uma visão sistêmica do processo agroindustrial da cana-de-açúcar, do ponto de vista dos ciclos biogeoquímicos com a reciclagem de resíduos e efluentes. Para o desenvolvimento do trabalho foram elaborados modelos conceituais e numéricos, apresentando conceitos de ruptura e regeneração de ciclos, suste...

El papel de los ciclos biogeoquímicos en el estudio de los problemas ambientales en Educación Secundaria

OpenAIRE

Esteve, Patricia; Jaén, Mercedes

2013-01-01

En el estudio de la dinámica de los ecosistemas tiene un papel predominante el conocimiento de los ciclos biogeoquímicos. En este trabajo se ha realizado un análisis de estos contenidos desde criterios disciplinares y didácticos, incluidos los libros de texto, que ha conducido a una serie de consideraciones para su enseñanza. Como síntesis de los aspectos anteriormente citados, se han identificado algunas cuestiones clave sobre los ciclos biogeoquímicos, que se deberían considerar al planific...

ESTIMATIVA DA FASE DO CICLO ESTRAL POR CITOLOGIA VAGINAL EM CADELAS (Canis familiaris, LINNAEUS, 1758) DA REGIÃO DE ITUVERAVA-SP

OpenAIRE

Ferreira da Costa, Elaine Cristina; Fafram; Léga, Elzylene; Fafram; Neves, Letícia; Fafram

2009-01-01

O ciclo estral da cadela se divide em fases sucessivas e individualizadas, sendo elas: proestro, estro, metaestro e diestro, seguido de anestro. Estas fases podem ser diferenciadas por exames hormonais ou citológicos, o que permite estimar o período de fertilidade, distúrbios do ciclo estral e inatividade sexual. Desta forma, o presente trabalho teve o intuito de realizar exames citológicos vaginais em cadelas e identificar seus escores reprodutivos. Para tanto, foram realizados exames em 91 ...

ESTUDIO DEL BULLYING EN EL CICLO SUPERIOR DE PRIMARIA

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Rosario Ruiz Arroyo

2015-01-01

Full Text Available Nuestra investigación trata el fenómeno del bullying en el ciclo superior de primaria. Para llevarla a cabo, hemos elaborado un cuestionario ad hoc a partir de una revisión bibliográfica de diferentes investigaciones en las que se han utilizado varios instrumentos, pruebas, cuestionarios... Este instrumento nos ha servido para analizar diferentes temas: la percepción que tienen los niños de ciclo superior sobre el bullying, en qué escenarios del centro escolar se producen más estos comportamientos, los diferentes tipos de bullying (físico, verbal y exclusión social y cuáles se producen más a menudo y analizar las respuestas que nos dan los alumnos en función del género y del curso (5.º y 6.º. Los resultados que hemos obtenido muestran, entre otras cosas: que en los niños se da más el bullying físico, mientras que en las niñas predomina el de tipo verbal y exclusión social; que la única diferencia según el curso es que en 6.º curso se da más exclusión social que en 5.º curso; y que donde se producen más conductas de bullying es en el patio, seguido del aula cuando no se encuentra el docente. Finalmente, partiendo de los resultados obtenidos, hemos elaborado unas propuestas de actuación psicopedagógicas para mejorar la convivencia en la escuela y otros espacios educativos.

Validação de procedimentos operacionais padrão no cuidado de enfermagem de pacientes com cateter totalmente implantado

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Rita Paiva Pereira Honório

2011-10-01

Full Text Available Os protocolos de assistência são recursos tecnológicos importantes na prática de saúde e devem ser validados, para adquirirem credibilidade científica na prática profissional. O objetivo desta pesquisa foi validar os itens de proposta de procedimentos operacionais padrão (POPs quanto à punção, heparinização e curativo do cateter totalmente implantado, por meio da análise de conceito proposta por Hoskins. O estudo se deu em duas etapas. Na primeira, elaborou-se um formulário para validação dos POPs. Na segunda, avaliou-se o conteúdo dos POPs por peritos. As sugestões versaram sobre reformulação da redação; acréscimo de ações, tornando-o mais claro e abrangente; a ordem dos passos dos procedimentos; e o material para a adequação do instrumento. Constatou-se a necessidade de outros estudos que direcionem os profissionais, principalmente, quanto à heparinização dos cateteres e à troca do primeiro curativo após punção, no sentido de uniformizar condutas embasadas em evidências científicas seguras.

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

International Nuclear Information System (INIS)

Le Roux, W.G.; Bello-Ochende, T.; Meyer, J.P.

2011-01-01

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.

Energy and exergy analysis of a closed Brayton cycle-based combined cycle for solar power tower plants

International Nuclear Information System (INIS)

Zare, V.; Hasanzadeh, M.

2016-01-01

Highlights: • A novel combined cycle is proposed for solar power tower plants. • The effects of solar subsystem and power cycle parameters are examined. • The proposed combined cycle yields exergy efficiencies of higher than 70%. • For the overall power plant exergy efficiencies of higher than 30% is achievable. - Abstract: Concentrating Solar Power (CSP) technology offers an interesting potential for future power generation and research on CSP systems of all types, particularly those with central receiver system (CRS) has been attracting a lot of attention recently. Today, these power plants cannot compete with the conventional power generation systems in terms of Levelized Cost of Electricity (LCOE) and if a competitive LCOE is to be reached, employing an efficient thermodynamic power cycle is deemed essential. In the present work, a novel combined cycle is proposed for power generation from solar power towers. The proposed system consists of a closed Brayton cycle, which uses helium as the working fluid, and two organic Rankine cycles which are employed to recover the waste heat of the Brayton cycle. The system is thermodynamically assessed from both the first and second law viewpoints. A parametric study is conducted to examine the effects of key operating parameters (including solar subsystem and power cycle parameters) on the overall power plant performance. The results indicate that exergy efficiencies of higher than 30% are achieved for the overall power plant. Also, according to the results, the power cycle proposed in this work has a better performance than the other investigated Rankine and supercritical CO_2 systems operating under similar conditions, for these types of solar power plants.

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

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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.

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

International Nuclear Information System (INIS)

1976-01-01

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

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

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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

Ciclo de produção e demanda térmica de clones da videira 'Concord' sobre diferentes porta-enxertos

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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.

Crescimento vegetativo da bananeira Nanica em dois ciclos sucessivos em função da aplicação de biofertilizantes líquidos

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Aldair Souza Medeiros

2014-06-01

Full Text Available Objetivou-se com essa pesquisa estudar os efeitos de biofertilizantes no crescimento vegetativo da bananeira Nanica, em dois ciclos sucessivos, no semiárido paraibano.O experimento foi conduzido, em condições de campo, no Campus IV, da Universidade Estadual da Paraíba. O solo da área experimental é classificado como Neossolo Flúvico de textura arenosa não apresentando problemas de acidez e alcalinidade. O delineamento experimental adotado foi o de blocos casualizados, com 50 tratamentos, no esquema fatorial 5 x 10, com quatro repetições, totalizando 200 parcelas experimentais (1 planta ou touceira/parcela. Os resultados obtidos na pesquisa mostram que o crescimento da bananeira Nanica (1° ciclo não foi afetado pelos tipos de biofertilizantes aplicados; os valores de diâmetro do pseudocaule, área foliar unitária e área folia da planta da bananeira Nanica (1° ciclo aumentaram com o incremento das doses de biofertilizante até os limites ótimos de 1,56; 1,63; e 1,54 L/aplicação, respectivamente, proporcionando valores ótimos dessas variáveis, havendo reduções a partir desses patamares; o crescimento da bananeira Nanica (2° ciclo não foi afetado pelas doses de biofertilizantes aplicados; o biofertilizante B5, que contém o maior número de ingredientes na sua composição, se sobressaiu, de forma significativa, sobre os demais tipos, proporcionando maiores altura da planta e área foliar da planta da bananeira Nanica (2° ciclo.

A bordo do “Tapete Voador”: Histórias e Aprendizagem no 1º Ciclo do Ensino Básico

OpenAIRE

Francisco, Inês

2014-01-01

O presente relatório científico surgiu no âmbito da Prática do Ensino Supervisionada (PES), no âmbito do Mestrado em Educação Pré-escolar e Ensino do 1º Ciclo do E. Básico na Escola Superior de Educadores de Infância Maria Ulrich. Este visa refletir o percurso da prática pedagógica e o que foi observado durante a mesma, numa turma de 1º e 2º ano do 1º Ciclo do Ensino Básico (CEB), mas também descrever o estudo realizado para responder a problemática que emergiu naquele contexto...

O CICLO DAS ÁGUAS DE MOACYR SCLIAR À LUZ DA HERMENÊUTICA SIMBÓLICA O CICLO DAS ÁGUAS BY MOACYR SCLIAR IN THE LIGHT OF SYMBOLIC HERMENEUTICS

Directory of Open Access Journals (Sweden)

Suzana Yolanda Lenhardt Machado Cánovas

2011-02-01

Full Text Available Este trabalho tem como objetivo estudar as imagens da água na narrativa O ciclo das águas, de Moacyr Scliar. Buscamos comprovar que o texto apresenta componentes míticos análogos aos das sociedades primitivas e arcaicas, ainda que pertença a um contexto realista. Isso permite que o aproximemos de poemas e relatos antigos. Mas como a obra de Scliar pertence a um mundo desprovido de significação religiosa, é frequente a desconstrução dos mitos, fato que é responsável pela natureza parodística do texto. Utilizamos concepções de Mircea Eliade, Northrop Frye e José Lorite Mena.This article aims at studying the cyclical images of water in the novel O ciclo das Águas, by Moacyr Scliar. We intend to prove that, even though the work belongs to a realistic context, it presents mythical components similar to primitive and archaic societies, which allows us to approach the novel to poems and ancient reports. However, as the novel by Scliar belongs to a world without religious meaning, it is frequent to observe the deconstruction of myths, which is responsible for the parody intrinsic to the text.

CICLO ESTRAL: FISIOLOGÍA BÁSICA Y ESTRATEGIAS PARA MEJORAR LA DETECCIÓN DE CELOS

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H Guáqueta

2009-01-01

Full Text Available El entendimiento de los factores que regulan el ciclo estral de la vaca es un componente esencial del manejo reproductivo en las fincas ganaderas. El incremento en la utilización de mano de obra calificada y especialistas en reproducción, así como la implementación de programas de inseminación artificial, sincronización del ciclo estral y transferencia de embriones han venido acentuando esta necesidad. La alta incidencia de actividad de monta durante la noche y los cortos periodos de duración del estro hacen de la detección de celos una tarea nada fácil, lo que parcialmente explicaría por qué la detección de calores es, después de la mastitis, la problemática número uno en muchas ganaderías y por qué la subfertilidad de las hembras se constituye en una de las principales razones de descarte del hato.

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

Energy Technology Data Exchange (ETDEWEB)

Venker, Jeanne

2015-03-31

The objective of the current work was to develop a model that is able to describe the transient behavior of supercritical carbon dioxide (sCO{sub 2}) 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 sCO{sub 2} Brayton cycles, can be assessed as a retrofit measure for present light water reactors. Transient simulations are hereby of great importance. The heat removal system has to be modeled explicitly to account for the interaction between the system and the behavior of the plant during different accident conditions. As a first step, transport and thermodynamic fluid properties of supercritical carbon dioxide have been implemented in ATHLET to allow for the simulation of the new working fluid. Additionally, a heat transfer correlation has been selected to represent the specific heat transfer of supercritical carbon dioxide. For the calculation of pressure losses due to wall friction, an approach for turbulent single phase flow has been adopted that is already implemented in ATHLET. In a second step, a component model for radial compressors has been implemented in the system code. Furthermore, the available model for axial turbines has been adapted to simulate the transient behavior of radial turbines. All extensions have been validated against experimental data. In order to simulate the interaction between the self-propelling heat removal system and a generic boiling water reactor, the components of the sCO{sub 2} Brayton cycle have been dimensioned with first principles. An available input deck of a generic BWR has then been extended by the residual heat removal system. The modeled application has shown that the extended version of ATHLET is suitable to simulate sCO{sub 2} Brayton cycles and to evaluate the introduced

El juego y la matemática. Juegos de matemáticas para el alumnado del primer ciclo de E. Primaria.

OpenAIRE

Sánchez Esteban, Nerea

2013-01-01

Este trabajo tiene como finalidad desarrollar una metodología que ayude a mejorar la adquisición de los conceptos que se estudian en el primer ciclo de Educación Primaria en el área de matemáticas, añadiendo una motivación al alumnado para que cuando se tenga que enfrentar a esta materia tenga una actitud positiva. Para conseguir esto he seleccionado una serie de juegos matemáticos enfocados a aprender de una manera diferente los contenidos que se tiene que trabajar en el citado primer ciclo....

La teoría del ciclo económico de Friedrich von Hayek: causas monetarias, efectos reales

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Gómez Betancourt Rebeca

2008-08-01

Full Text Available Este artículo propone una lectura simultánea de dos textos: La Teoría monetaria y el ciclo económico (1929 y Precios y producción (1931, con el objetivo de presentar la teoría de los ciclos económicos del joven Hayek, como un conjunto teórico congruente. Ambos textos poseen una unidad temática complementaria, que representa el pensamiento del joven Hayek. Este artículo, subraya la distinción entre el rol que juegan los factores reales y los monetarios en la coherencia de su teoría. Aunque Hayek demuestre que el dinero no es neutro, ya que existe una variación de la estructura de los precios relativos, su propósito era probar su neutralidad.

Development of a Performance Analysis Code for the Off-design conditions of a S-CO2 Brayton Cycle Energy Conversion System

International Nuclear Information System (INIS)

Yoo, Yong-Hwan; Cha, Jae-Eun; Lee, Tae-Ho; Eoh, Jae-Hyuk; Kim, Seong-O

2008-01-01

For the development of a supercritical carbon dioxide (S-CO2) Brayton cycle energy conversion system coupled to KALIMER-600, a thermal balance has been established on 100% power operating conditions including all the reactor system models such as a primary heat transport system (PHTS), an intermediate heat transport system (IHTS), and an energy conversion system. The S-CO2 Brayton cycle energy conversion system consists of a sodium-CO2 heat exchanger (Hx), turbine, high temperature recuperate (HTR), low temperature recuperate (LTR), precooler, compressor no.1, and compressor no.2. Two compressors were employed to avoid a sharp change of the physical properties near their critical point with a corresponding pressure. The component locations and their operating conditions are illustrated. Energy balance of the power conversion system in KALIMER-600 was designed with the full power condition of each component. Therefore, to predict the off-design conditions and to evaluate each component, an off-design performance analysis code should be accomplished. An off-design performance analysis could be classified into overall system control logic and local system control logic. The former means that mass flow rate and power are controlled by valves, and the latter implies that a bypass or inventory control is an admitted system balance. The ultimate goal of this study is development of the overall system control logic

An improved model to evaluate thermodynamic solar plants with cylindrical parabolic collectors and air turbine engines in open Joule–Brayton cycle

International Nuclear Information System (INIS)

Ferraro, Vittorio; Imineo, Francesco; Marinelli, Valerio

2013-01-01

An improved model to analyze the performance of solar plants operating with cylindrical parabolic collectors and atmospheric air as heat transfer fluid in an open Joule–Brayton cycle is presented. In the new model, the effect of the incident angle modifier is included, to take into account the variation of the optical efficiency with the incidence angle of the irradiance, and the effect of the reheating of the fluid also has been studied. The analysis was made for two operating modes of the plants: with variable air flow rate and constant inlet temperature to the turbine and with constant flow rate and variable inlet temperature to the turbine, with and without reheating of the fluid in the solar field. When reheating is used, the efficiency of the plant is increased. The obtained results show a good performance of this type of solar plant, in spite of its simplicity; it is able to compete well with other more complex plants operating with different heat transfer fluids. - Highlights: ► An improved model to calculate an innovative CPS solar plant is presented. ► The plant works with air in an open Joule–Brayton cycle. ► The reheating of the air increases the thermodynamic efficiency. ► The plant is very simple and competes well with other more complex solar plants

Corticosteróide Antenatal: Ciclo Único versus Múltiplo - Comparação de Resultados Antenatal Corticosteroids: Single versus Multiple Courses - Comparison of the Results

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Joice Fabiola Meneguel

2002-09-01

Full Text Available Objetivo: avaliar se ciclos múltiplos de corticosteróide antenatal (CEA são mais efetivos, em relação ao ciclo único, na redução da morbimortalidade de prematuros. Métodos: estudo retrospectivo envolvendo 184 neonatos com idade gestacional inferior a 34 semanas, nascidos em hospital de nível terciário de São Paulo no período de janeiro de 1988 a dezembro de 1998. Os pacientes foram divididos conforme o tratamento em: ciclo único (n=135: se a gestante recebeu um ciclo completo do CEA (2 doses de betametasona ou 4 doses de dexametasona, entre 24 horas e 7 dias do parto e ciclos múltiplos (n=49: se a gestante foi tratada com dois ou mais ciclos completos. Foram comparados entre os dois grupos do estudo: síndrome do desconforto respiratório (SDR, mortalidade intra-hospitalar e morbidade neonatal combinada (ocorrência de um ou mais: SDR, hemorragia periintraventricular, displasia broncopulmonar, enterocolite necrosante, sepse ou óbito intra-hospitalar. Os dados maternos e neonatais foram comparados pelo teste t de Student ou Mann-Whitney para as variáveis numéricas e pelo chi² ou exato de Fisher, com cálculo das "odds ratio" e seu intervalo de confiança, para as variáveis categóricas. Resultados: não foi demonstrada diferença significante na evolução dos neonatos do grupo ciclo único em relação ao múltiplo quanto à ocorrência de SDR (ciclo único: 22% e ciclo múltiplo: 18%, mortalidade intra-hospitalar (único 18% e múltiplo 12% e morbidade neonatal combinada (único 62% e múltiplo 63%. Conclusões: o uso de ciclos múltiplos de CEA não diminuiu a morbimortalidade de prematuros. Esse estudo reforça a recomendação atual da utilização de ciclo único de corticosteróide para a maturação fetal em gestantes em trabalho de parto prematuro.Purpose: to evaluate if multiple courses of antenatal corticosteroids are more effective than single ones to reduce morbidity and mortality of preterm infants. Methods

Universal Expression of Efficiency at Maximum Power: A Quantum-Mechanical Brayton Engine Working with a Single Particle Confined in a Power-Law Trap

International Nuclear Information System (INIS)

Ye Zhuo-Lin; Li Wei-Sheng; Lai Yi-Ming; He Ji-Zhou; Wang Jian-Hui

2015-01-01

We propose a quantum-mechanical Brayton engine model that works between two superposed states, employing a single particle confined in an arbitrary power-law trap as the working substance. Applying the superposition principle, we obtain the explicit expressions of the power and efficiency, and find that the efficiency at maximum power is bounded from above by the function: η_+ = θ/(θ + 1), with θ being a potential-dependent exponent. (paper)

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

International Nuclear Information System (INIS)

Joyner, Claude Russell II; 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 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

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

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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

Vygotsky: uma base teórica para a proposta do ensino por meio de ciclos

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Tarcísio Renan Peireira Sousa Resende

2017-10-01

Full Text Available Há muito tempo, o modelo de escola organizada por ciclo tem sido palco de discussões na comunidade educacional brasileira. Observa-se que existe alguma resistência da parte dos docentes, bem como uma visão distorcida da essência da referida proposta. Nesse sentido, este estudo objetivou analisar as concepções e as bases da escola ciclada, relacionando-as à teoria sociointeracionista de Vygotsky. Trata-se de uma pesquisa descritivo-exploratória, alicerçada em pesquisa bibliográfico-documental. Foram utilizados, como autores basilares, Vygotsky (2015, 2013, 1998, Rego (2009, Mainardes (2009, além dos documentos oficiais de Mato Grosso (2010 e do Brasil (1996. A formação em ciclos implica à escola considerar o indivíduo como um ser histórico-social, levando em conta o ambiente no qual está inserido e, assim, desenvolver, no ambiente escolar, práticas pedagógicas que ampliem e desenvolvam as capacidades que ainda requerem ser apropriadas e compreendidas, a partir da interação social de cada sujeito. Conclui-se que a proposta das escolas organizadas em ciclos está sedimentada na teoria sociointeracionista de Vygotsky, todavia, alguns fatores são limitantes, dentre eles, a falta de formação suficiente dos professores, para executar a proposta.  Acredita-se que, se esta abordagem for bem trabalhada, será possível ter uma escola mais inclusiva, que tenha proximidade com a comunidade, na qual está inserida, que promova maior aproximação do aluno com o conhecimento científico, bem como o possibilite avançar no processo sócio-histórico de humanização, criando possibilidades para que seja um sujeito capaz de contribuir para uma transformação social. Palavras-chave: Sociointeracionismo. Vygotsky. Organização da escola em ciclos. Vygotsky: a theoretical basis for the proposal of teaching through cycles  ABSTRACT  For a long time, the school model organized by cycle has been the scene of discussions in the Brazilian

Potential Improvements of Supercritical Recompression CO2 Brayton Cycle Coupled with KALIMER-600 by Modifying Critical Point of CO2

International Nuclear Information System (INIS)

Jeong, Woo Seok; Lee, Jeong Ik; Jeong, Yong Hoon; No, Hee Cheon

2010-01-01

Most of the existing designs of a Sodium cooled Fast Reactor (SFR) have a Rankine cycle as an electric power generation cycle. This has the risk of a sodium water reaction. To prevent any hazards from a sodium water reaction, an indirect Brayton cycle using Supercritical Carbon dioxide (S-CO 2 ) as the working fluids for a SFR is an alternative approach to improve the current SFR design. The supercritical Brayton cycle is defined as a cycle with operating conditions above the critical point and the main compressor inlet condition located slightly above the critical point of working fluid. This is because the main advantage of the cycle comes from significantly decreased compressor work just above the critical point due to high density near boundary between supercritical state and subcritical state. For this reason, the minimum temperature and pressure of cycle are just above the CO 2 critical point. In other words, the critical point acts as a limitation of the lowest operating condition of the cycle. In general, lowering the minimum temperature of a thermodynamic cycle can increase the efficiency and the minimum temperature can be decreased by shifting the critical point of CO 2 as mixed with other gases. In this paper, potential enhancement of S-CO 2 cycle coupled with KALIMER-600, which has been developed at KAERI, was investigated using a developed cycle code with a gas mixture property program

Relação dos atributos da contabilidade gerencial com os estágios do ciclo de vida organizacional

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Ilse Maria Beuren

2015-07-01

Full Text Available O estudo objetiva verificar se há relação entre o uso dos atributos da contabilidade gerencial e os estágios do ciclo de vida organizacional. Os atributos da contabilidade gerencial foram baseados no estudo de Moores e Yuen (2001 e os estágios do ciclo de vida organizacional na proposição de Lester, Parnell e Carraher (2003. A população da pesquisa compreendeu as 264 empresas do segmento industrial de máquinas, aparelhos e materiais elétricos listadas na Secretaria da Fazenda do Estado de Santa Catarina, Brasil, e a amostra constituiu-se dos 40 gestores que responderam o questionário. O uso dos atributos da contabilidade gerencial nos respectivos estágios do ciclo de vida organizacional foi evidenciado pela análise descritiva das respostas e o agrupamento das variáveis por meio das respectivas correlações pela aplicação da Análise das Componentes Principais. Os resultados mostram que os atributos da contabilidade gerencial, nos aspectos de seleção e de apresentação das informações, são mais utilizados nas empresas que se encontram nos estágios de crescimento e rejuvenescimento do que nas classificadas nos estágios de nascimento e declínio. Conclui-se que há relação entre o uso dos atributos da contabilidade gerencial e a evolução nos estágios do ciclo de vida das empresas pesquisadas, o que coaduna com os resultados de pesquisas que também adotaram as proposições dos autores que consubstanciaram este estudo.

Utilización de compost agotado de champiñón como capa de coberturas en nuevos ciclos de producción.

OpenAIRE

PARDO-GIMÉNEZ, A.; ZIED, D. C.; PARDO-GONZÁLEZ, J. E.

2011-01-01

El objetivo de este trabajo fue evaluar el comportamiento agronómico de seis mezclas de cobertura, elaboradas a partir de sustrato postcultivo del champiñón Agaricus bisporus, en nuevos ciclos de cultivo. Los resultados obtenidos mostraron la viabilidad de la reintroducción del sustrato en nuevos ciclos de cultivo, ya sea como material de base único, si se somete a un proceso de lavado para eliminar sales solubles, o bien mezclado con otros materiales de baja conductividad, como es el caso de...

Thermal performance of Brayton power cycles. A study based on high-temperature gas-cooled reactors

International Nuclear Information System (INIS)

Herranz, Luis E.; Linares, Jose I.; Moratilla, Beatriz Y.

2005-01-01

Power cycles optimization has become an essential ingredient to achieve sustainability and improve economic competitiveness of forthcoming Generation IV designs. This paper investigates performance of several configurations of direct helium Brayton cycles. An optimum layout is proposed based on multiple intercooled compression stages and in-between turbines reheating: C(IC) 2 HTRTX. Under the hypotheses and approximations made, a 59% is estimated and it increases even further (67%) when the foreseen technological development is considered. A sensitive analysis identified key components and variables for cycle performance. Particular attention is paid to the effect of the extracted gas mass fraction for reheating. It is shown that the C(IC) 2 HTRTX cycle provides a feasible and simple way to operate the power plant the load-follow mode with a very little loss of efficiency. (author)

Cycle Design of Reverse Brayton Cryocooler for HTS Cable Cooling Using Exergy Analysis

Science.gov (United States)

Gupta, Sudeep Kumar; Ghosh, Parthasarathi

2017-02-01

The reliability and price of cryogenic refrigeration play an important role in the successful commercialization of High Temperature Superconducting (HTS) cables. For cooling HTS cable, sub-cooled liquid nitrogen (LN2) circulation system is used. One of the options to maintain LN2 in its sub-cooled state is by providing refrigeration with the help of Reverse Brayton Cryo-cooler (RBC). The refrigeration requirement is 10 kW for continuously sub-cooling LN2 from 72 K to 65 K for cooling 1 km length of HTS cable [1]. In this paper, a parametric evaluation of RBC for sub-cooling LN2 has been performed using helium as a process fluid. Exergy approach has been adopted for this analysis. A commercial process simulator, Aspen HYSYS® V8.6 has been used for this purpose. The critical components have been identified and their exergy destruction and exergy efficiency have been obtained for a given heat load condition.

Crescimento e produção de primeiro ciclo da bananeira 'Prata Anã' (AAB em sete espaçamentos

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PEREIRA MARLON CRISTIAN TOLEDO

2000-01-01

Full Text Available Este estudo teve por objetivo verificar o comportamento da bananeira (Musa spp. 'Prata Anã' no primeiro ciclo de produção na localidade de Jaíba, MG, submetida a sete espaçamentos, com irrigação. Os tratamentos foram: triângulo: 2,7 m x 3,2 m (1.157 covas/ha e 2,9 m x 3,4 m (1.014 covas/ha; fileira dupla em triângulo: 4,5 m x 2,0 m x 3,0 m (1.026 covas/ha e 4,5 m x 2,0 m x 2,0 m (1.538 covas/ha; fileira dupla em retângulo: 4,5 m x 2,0 m x 3,5 m (879 covas/ha; e retângulo: 4,0 m x 2,0 m (1.250 covas/ha e 3,0 m x 2,0 m (1.666 covas/ha. Os sistemas de espaçamento e as densidades populacionais testados não alteraram as taxas de crescimento das plantas nem suas características na época da colheita. Entretanto, as bananeiras plantadas em maiores densidades apresentaram maior produtividade, atingindo até 29,1 t/ha. As plantas apresentaram, em média, ciclo do plantio à colheita de 411 dias, ciclo do florescimento à colheita de 141 dias, e cachos com 17,7 kg, 9,1 pencas e 134 frutos. Para o primeiro ciclo de produção, o espaçamento mais apropriado foi de 3,0 m x 2,0 m, em retângulo, para a região de Jaíba.

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...

Caracterização pós-colheita de frutos de bananeira 'BRS Platina' de primeiro ciclo, sob regulação do déficit de irrigação

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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.

Ciclos clássicos num ambiente de racionalidade limitada

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Jaylson Jair da Silveira

2003-12-01

Full Text Available O presente trabalho toma como ponto de partida o modelo macrodinâmico de Richard M. Goodwin, apresentado no clássico artigo “A Growth Cycle” (1967. Neste modelo a interação entre distribuição de renda e acumulação de capital gera um ciclo de crescimento que oscila em torno de uma trajetória de crescimento equilibrado. O objetivo do presente trabalho é investigar a possibilidade de existência de ciclos goodwinianos com heterogeneidade de salários e de taxas de lucro. Essa análise é realizada considerando o processo de concorrência entre trabalhadores num ambiente de racionalidade limitada. Para formalizar o processo de concorrência entre trabalhadores foram utilizados dois recursos: (i a “alegoria das ilhas”, que tem sido amplamente adotada na macroeconomia moderna, a fim de apreender situações de informação imperfeita; e (ii os instrumentos analíticos desenvolvidos pela teoria dos jogos evolucionários aplicada a ambientes sociais. O modelo construído combina o modelo de Goodwin com uma formalização estilizada do fluxo de trabalho como um processo de imitação num ambiente de racionalidade limitada (dinâmica de replicação num contexto social. Neste modelo demonstra-se a possibilidade de o sistema econômico não convergir para um estado de equilíbrio de longo prazo e a possibilidade do sistema econômico convergir para um ciclo goodwiniano caracterizado por heterogeneidade de salários e de taxas de lucro.This paper starts from the macrodynamical model developed by Richard M. Goodwin, which was first shown in the seminal paper “A Growth Cycle” (Goodwin, 1967. In this model it was described an interaction between income-distribution and capital accumulation that generates a growth cycle swinging along a balanced growth path. The objective of this work is to investigate the possibility of existence of goodwinian cycles with heterogeneity in wage and in profit rates. This task is carried out considering the

Inter-relações entre os ciclos de transmissão do Trypanosoma cruzi no município de Bambuí, Minas Gerais, Brasil

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Fernandes Alexandre José

1994-01-01

Full Text Available Neste trabalho apresentamos um estudo das inter-relações recentes entre os ciclos de transmissão silvestre e doméstico do T. cruzi no município de Bambuí, Minas Gerais, Brasil. No final da década de 1930, o Panstrongylus megistus era encontrado em 75% das casas. Subseqüentemente, o Triatoma infestans tornou-se a espécie predominante, sendo encontrada em 20% das residências urbanas e em mais de 60% das periurbanas. Com as intensas campanhas de borrifação desenvolvidas entre 1956 e 1969, o T. infestans foi erradicado do município, e a transmissão da doença de Chagas ao homem, interrompida, com aparecimento de P. megistus em residências rurais. Amostras de T. cruzi isoladas via xenodiagnóstico e hemocultura de 43 gambás (Didelphis albiventris capturados em ambiente peridomiciliar e silvestre foram caracterizadas isoenzimaticamente e, independentemente da via de isolamento, apresentaram perfil de zimodema Z1. Por meio do Programa de Vigilância Epidemiológica da doença de Chagas, no período de agosto de 1986 a dezembro de 1988, 154 exemplares de P. megistus foram capturados pela população no peridomicílio e intradomicílio rural, estando 9,8% infectados pelo T. cruzi. Na caracterização isoenzimática de 13 amostras de T. cruzi isoladas desses triatomíneos, seis pertenciam ao zimodema Z1 (ciclo de transmissão silvestre, e sete ao Z2 (ciclo de transmissão doméstico. A captura de exemplares de P. megistus no intradomicílio, naturalmente infectados com parasitas de ambos os ciclos, indica a superposição dos ciclos de transmissão da doença de Chagas no município de Bambuí. Outra evidência da inter-relação dos ciclos pôde ser observada no isolamento de T. cruzi Z2 de um gato e a participação do cão como reservatório de T. cruzi Z1. A presença do P. megistus no peridomicílio representa importante elo entre o ambiente silvestre e o intradomicílio, servindo como veiculador do T. cruzi Z1 e na manutenção de

Preliminary Failure Modes, Effects and Criticality Analysis (FMECA) of the Brayton Isotope Power System (BIPS) Ground Demonstration System. Report 76-311965

International Nuclear Information System (INIS)

Miller, L.G.

1976-01-01

A Failure Modes, Effects and Criticality Analysis (FMECA) has been made of the Brayton Isotope Power System Ground Demonstration System (BIPS-GDS). Details of the analysis are discussed. The BIPS Flight System was recently analyzed in an AIRPHX report. Since the results of the Flight System FMECA are directly applicable to the BIPS to be tested in the GDS mode, the contents of the earlier FMECA have not been repeated in this current analysis. The BIPS-FS FMECA has been reviewed and determined to be essentially current

Diseño e Implementación de Sistemas de Control de Nivel para Cinco Tanques de Bombeo de Hidrocarburos con Sensoramiento tipo Radar en la Estación Shushufindi - EP PETROECUADOR

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Hernán Montenegro

2012-11-01

Full Text Available El presente artículo fue desarrollado para su implementación en fases según el Ciclo de Deming, desarrollando un sistema de control de nivel on-off con histéresis en los tanques de almacenamiento de hidrocarburos en la Estación Cabecera Shushufindi del Poliducto Shushufindi-Quito de EP Petroecuador, teniendo como base de pruebas la Estación Osayacu del mismo poliducto. Ademas se diseño un sistema totalmente automatizado mediante un control PID como una posible solución al proceso paulatino de modernización de la planta, junto con una propuesta de interfaz humano-maquina (HMI siguiendo normas ergonómicas de diseño internacional.

Optimization of advanced high-temperature Brayton cycles with multiple reheat stages

International Nuclear Information System (INIS)

Haihua Zhao; Per F Peterson

2005-01-01

Full text of publication follows: This paper presents an overview and a few point designs for multiple-reheat Brayton cycle power conversion systems using high temperature molten salts (or liquid metals). All designs are derived from the General Atomics GT-MHR power conversion unit (PCU). The GT-MHR PCU is currently the only closed helium cycle system that has undergone detailed engineering design analysis, and that has turbomachinery which is sufficiently large to extrapolate to a >1000 MW(e) multiple reheat gas cycle power conversion system. Analysis shows that, with relatively small engineering modifications, multiple GT-MHR PCU's can be connected together to create a power conversion system in the >1000 MW(e) class. The resulting power conversion system is quite compact, and results in what is likely the minimum gas duct volume possible for a multiple-reheat system. To realize this, compact offset fin plate type liquid-to-gas heat exchangers (power densities from 10 to 120 MW/m 3 ) are needed. Both metal and non-metal heat exchangers are being investigated for high-temperature, gas-cooled reactors for temperatures to 1000 deg. C. Recent high temperature heat exchanger studies for nuclear hydrogen production has suggested that carbon-coated composite materials such as liquid silicon infiltrated chopped fiber carbon-carbon preformed material potentially could be used to fabricate plate fin heat exchangers with reasonable price. Different fluids such as helium, nitrogen and helium mixture, and supercritical CO 2 are compared for these multiple reheat Brayton cycles. Nitrogen and helium mixture cycle need about 40% more total PCU volume than helium cycle while keeping the same net cycle efficiency. Supercritical CO 2 needs very high pressure to optimize. Due to relatively detailed design for components such as heat exchangers, turbomachinery, and duct system, relatively accurate total pressure loss can be obtained, which results in more credible net efficiency

Evolução tectonomagmática da Zona de Ossa-Morena durante o ciclo Varisco: Estará o ciclo de J. Tuzo Wilson completo?

OpenAIRE

Pedro, Jorge; Moita, Patricia; Araújo, Alexandre; Fonseca, Paulo; Munhá, José

2006-01-01

A evolução tectonomagmática varisca da Zona de Ossa-Morena mostra evidências claras dos estádios iniciais (“rifting”) e finais (colisionais) de um ciclo de Wilson, estando o estádio intermédio de magmatismo oceânico, em bacias com margens passivas, representado pelas Sequências Ofiolíticas Internas. As variações no tempo das características geológicas/geoquímicas do magmatismo no ramo SW da Cadeia Varisca Ibérica, são consistentes com as variações expectáveis durante a evolução típica de um c...

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.

El ciclo del potasio en dehesas de Quercus rotundifolia y Quercus pyrenaica

OpenAIRE

Escudero Berián, Alfonso; García Criado, Balbino; Alonso Peloche, Herminio

1985-01-01

Hemos estudiado el ciclo del potasio en dehesas de Quercus rotundifolia Lam. y Quercus pyrenaica Willd. de la provincia de Salamanca. El potasio es el elemento que se transfiere en mayores proporciones a través de frutos y de material herbáceo, que son materias altamente digestibles. Por ello, su transferencia al subsistema herbívoro es mayor que para los restantes nutrientes. El potasio es también el macronutriente más intensamente extraído de los tejidos vegetables por el ...

Análisis de Ciclo de Vida (ACV) del proceso siderúrgico

OpenAIRE

Cadavid Marín, Gabriel Hernando

2014-01-01

Esta contribución muestra los resultados de una investigación realizada para comparar los impactos ambientales causados por los procesos siderúrgicos para producir acero, a partir de mineral de hierro y acero reciclado, mediante la aplicación del Análisis de Ciclo de Vida (ACV). En el análisis del inventario se utilizan datos secundarios de la industria siderúrgica colombiana publicados en trabajos anteriores. Los resultados obtenidos, para el año 2011, por cada kilogramo de acero pro...

GESTIÓN DE RESIDUOS SÓLIDOS EN CADENAS DE SUMINISTRO DE CICLO CERRADO DESDE LA PERSPECTIVA DE LA INVESTIGACIÓN DE OPERACIONES

OpenAIRE

Peña-Montoya, Claudia Cecilia; Osorio-Gómez, Juan Carlos; Vidal-Holguín, Carlos Julio; Torres-Lozada, Patricia; Marmolejo-Rebellón, Luis Fernando

2015-01-01

La integración de los flujos reversos y directos en la cadena de suministro, trae beneficios al reducir costos y evitar el daño ambiental porque se recupera valor de los residuos sólidos; esta integración se conoce como la cadena de suministro de ciclo cerrado. La mayoría de experiencias que relacionan cadena de suministro de ciclo cerrado y decisiones de gestión de residuos sólidos, provienen de países desarrollados con estrictas regulaciones ambientales y usan técnicas de invetigación de op...

Reynolds stress scaling in pipe flow turbulence-first results from CICLoPE.

Science.gov (United States)

Örlü, R; Fiorini, T; Segalini, A; Bellani, G; Talamelli, A; Alfredsson, P H

2017-03-13

This paper reports the first turbulence measurements performed in the Long Pipe Facility at the Center for International Cooperation in Long Pipe Experiments (CICLoPE). In particular, the Reynolds stress components obtained from a number of straight and boundary-layer-type single-wire and X-wire probes up to a friction Reynolds number of 3.8×10 4 are reported. In agreement with turbulent boundary-layer experiments as well as with results from the Superpipe, the present measurements show a clear logarithmic region in the streamwise variance profile, with a Townsend-Perry constant of A 2 ≈1.26. The wall-normal variance profile exhibits a Reynolds-number-independent plateau, while the spanwise component was found to obey a logarithmic scaling over a much wider wall-normal distance than the other two components, with a slope that is nearly half of that of the Townsend-Perry constant, i.e. A 2,w ≈A 2 /2. The present results therefore provide strong support for the scaling of the Reynolds stress tensor based on the attached-eddy hypothesis. Intriguingly, the wall-normal and spanwise components exhibit higher amplitudes than in previous studies, and therefore call for follow-up studies in CICLoPE, as well as other large-scale facilities.This article is part of the themed issue 'Toward the development of high-fidelity models of wall turbulence at large Reynolds number'. © 2017 The Author(s).

AMONIO-OXIDASAS BACTERIANAS Y ARQUEALES INVOLUCRADAS EN EL CICLO DEL NITRÓGENO

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Sergio Andrade Ochoa

2015-07-01

Full Text Available La nitrificación, la oxidación microbiana de amoníaco a nitrato, juega un papel crítico en el ciclo global del nitrógeno. Se ha considerado a dos grupos distintos de bacterias capaces de oxidar el amoníaco (AOB como las responsables de llevar a cabo el primer paso de la nitrificación; en esos dos grupos se encuentran las Beta-proteobacterias, que incluyen a los géneros Nitrosomonas y Nitrosospira, y las Gamma-proteobacterias, que engloban al género Nitrosococcus. Sin embargo, se ha demostrado la existencia de arqueas oxidantes de amoníaco (AOA y su contribución al ciclo del nitrógeno, siendo Nitrosopumilus maritimus la más estudiada en este proceso. La dinámica entre estos dos sistemas de oxidantes de amoníaco es compleja y los estudios se han enfocado a distintos hábitats, se ha propuesto que las contribuciones relativas de las comunidades AOA y AOB dependen de propiedades fisicoquímicas del ambiente, que afectan su abundancia y diversidad; esto dificulta establecer con exactitud el nicho ecológico en el que se desempeña cada comunidad. El objetivo de esta revisión es discutir la evidencia científica que facilite el entendimiento del papel que desempeñan los microorganismos oxidantes del amoníaco.

Overview of CNES-CEA joint programme on space nuclear Brayton systems

International Nuclear Information System (INIS)

Carre, F.; Proust, E.; Chaudourne, S.; Keirle, P.; Tilliette, Z.; Vrillon, B.

1990-01-01

In 1982, a cooperative programme on space nuclear power systems was initiated between the French Centre National d'Etudes Spatiales (CNES) and the Commissariat a l'Energie Atomique (CEA), to assess the feasibility, lead time, cost, competitiveness and development prospects for space nuclear power systems (SPS) in the 20 to 200 kWe range. The present three-year study phase is primarily oriented toward the assessment of various reactor candidate technologies and system design options for nuclear SPS in the 20 kWe class, which corresponds to the expected power needs of the first European space missions, anticipated to begin in 2005. This paper presents an overview of the present programme phase, with emphasis on design studies of three reference design concepts for 20 kWe turboelectric nuclear power systems selected so as to cover a wide range of reactor temperatures and corresponding technologies. The systems differ mainly in their nuclear reactors which are: the Liquid Metal Fast Breeder derivative or UO 2 /Na/Stainless steel -650 0 C; the High Temperature Gas-cooled derivative or UO 2 /direct cycle/super alloys - 850 0 C; and the UN/Li/MoRe alloy - 1120 0 C. All three systems use a Brayton cycle with recuperation for power conversion. (author)

Precios y Salarios Reales en Chile durante el Ciclo Salitrero, 1880-1930

OpenAIRE

Matus González, Mario

2009-01-01

DE LA TESIS:Las pésimas condiciones de vida de los trabajadores urbanos chilenos a inicios del siglo XX -especialmente aquellas referidas al ámbito de la habitación y situación sanitaria- han llevado a que la historiografía dedicada al Ciclo Salitrero de Chile (1880-1930), cultivada tanto por especialistas chilenos como extranjeros, haya tendido a señalar que estas circunstancias fueron ocasionadas por una caída constante y generalizada en el valor de los salarios reales de los trabajadores c...

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...

UN CICLO CERRADO: EL PATRIMONIO NOBILIARIO CONSTRUIDO EN LA CIUDAD DE MURCIA

Directory of Open Access Journals (Sweden)

Francisco Calvo García-Tornel

2011-01-01

Full Text Available 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.

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

International Nuclear Information System (INIS)

Carre, F.; Proust, E.; Chaudourne, S.; Keirle, P.; Tilliette, Z.; Vrillon, B.

1989-01-01

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

Sistema de simulación de escenarios de ciclos avanzados de combustible nuclear en transición = Simulation system for advanced fuel cycle transition scenarios

OpenAIRE

Merino Rodríguez, Iván

2015-01-01

El estudio de los ciclos del combustible nuclear requieren de herramientas computacionales o "códigos" versátiles para dar respuestas al problema multicriterio de evaluar los actuales ciclos o las capacidades de las diferentes estrategias y escenarios con potencial de desarrollo en a nivel nacional, regional o mundial. Por otra parte, la introducción de nuevas tecnologías para reactores y procesos industriales hace que los códigos existentes requieran nuevas capacidades para evaluar la transi...

Ciclo de vida de Triatoma dimidiata Latreille, 1811 (Hemiptera, Reduviidae) en condiciones de laboratorio: producción de ninfas para ensayos biológicos

OpenAIRE

Marlene Reyes; Víctor Manuel Angulo

2009-01-01

Introducción. A pesar de la importancia de Triatoma dimidiata como vector de la enfermedad de Chagas, poco se conoce de su ciclo biológico y de la producción eficiente de insectos disponibles para ensayos biológicos. Objetivo. Determinar las características del ciclo de vida en el laboratorio y establecer las condiciones del estado nutricional para la producción eficiente de ninfas de V estadio para ensayos biológicos. Materiales y métodos. Se determinaron los tiempos de desarrollo de l...

A introdução da matemática moderna no Ciclo Preparatório do Ensino Secundário em Portugal

OpenAIRE

Bento, Marta Alexandra Marques

2012-01-01

Dissertação para obtenção do Grau de Mestre em Ensino da Matemática Com o presente estudo pretende-se estudar a introdução do programa de Matemática Moderna no contexto da criação do novo Ciclo Preparatório do Ensino Secundário, através da visão do Inspetor Joaquim Simões Redinha, sendo por isso necessário reunir e digitalizar documentação relativa aos primeiros anos do referido ciclo e obter notas sobre o percurso profissional e perspetivas do supramencionado inspetor. Pretende-se aind...

Seminario Políticas Públicas y Gestión Estatal | Tema 2: Ciclo y agenda de las políticas públicas

OpenAIRE

Pagani, María Laura

2017-01-01

Presentación general del ciclo de política pública y las diferentes etapas. Sus limitaciones como recurso de análisis de las PP. Agenda Social y Agenda Política: los procesos de construcción de la Agenda política, diseño. Definición de política pública. Presentación general del ciclo de política pública y las diferentes etapas. Sus limitaciones como recurso de análisis de las PP. La formación de la agenda y la definición de problema público. Las diferentes agendas: la agenda ciudadana, públic...

Ciclos reais brasileiros em dois setores

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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.

CICLO DE VIDA DO GOL VW: UMA ANÁLISE DAS UNIDADES VENDIDAS NO MERCADO BRASILEIRO ENTRE OS ANOS 1987 E 2010

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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.

Optimizing an advanced hybrid of solar-assisted supercritical CO2 Brayton cycle: A vital transition for low-carbon power generation industry

International Nuclear Information System (INIS)

Milani, Dia; Luu, Minh Tri; McNaughton, Robbie; Abbas, Ali

2017-01-01

Highlights: • The layout of 14 demonstrative supercritical CO 2 closed Brayton cycles are analysed. • The key parameters of the “combined” cycle are sensitized and optimized. • The effect of thermal efficiency vs HX area on techno-economic nexus is highlighted. • The design of a matching solar heliostat field in direct configuration is revealed. • The water demand for hybrid vs water-only cooling scenarios are assessed. - Abstract: Current worldwide infrastructure of electrical power generation would mostly continue to rely on fossil-fuel but require a modest transition for the ultimate goal of decarbonizing power generation industry. By relying on those already established and carefully managed centrepiece power plants (PPs), we aim at filling the deficits of the current electrical networks with smaller, cleaner, and also more efficient PPs. In this context, we present a unique model for a small-scale decentralized solar-assisted supercritical CO 2 closed Brayton cycle (sCO 2 -CBC). Our model is based on the optimized values of three key performance indicators (KPIs); thermal efficiency, concentrated solar power (CSP) compatibility, and water demand for cooling. For a case-study of 10 MW e CSP-assisted sCO 2 -CBC power plant, our dynamic model shows a 52.7% thermal efficiency and 25.9% solar penetration and up to 80% of water saving in heat-rejection units. These KPIs show significant promise of the solar-assisted supercritical CO 2 power cycle for an imperative transformation in the power industry towards future sustainable electricity generation.

Relação entre data de admissão hospitalar e período do ciclo menstrual de mulheres com diagnóstico de esquizofrenia

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Bassit Débora P

2000-01-01

Full Text Available INTRODUÇÃO: Existem diferenças no curso da esquizofrenia entre homens e mulheres, sendo que nessas o início é mais tardio e o prognóstico melhor. Uma possível explicação para esse achado é a presença de estradiol, que pode agir como fator protetor. Essa possibilidade é reforçada por alguns fatores, como piora dos sintomas no período puerperal e perimenstrual, quando os níveis de estradiol estão mais baixos. MÉTODOS: Foram entrevistadas 39 pacientes com esquizofrenia admitidas consecutivamente para internação por exacerbação do quadro psicótico. As pacientes apresentavam ciclo menstrual regular e tinham idade média de 34,2 anos. Os sintomas esquizofrênicos foram medidos com a escala BPRS. O dia do ciclo em que elas se encontravam foi determinado na entrevista de admissão ou durante o período de internação, com a verificação de ocorrência de sangramento menstrual. As pacientes foram divididas em três grupos, de acordo com o período do ciclo menstrual no qual se encontravam no dia da internação. Foi feita comparação da distribuição observada com a distribuição esperada se não houvesse diferença no número de mulheres entre os três grupos. RESULTADOS: Foi observado que a maioria das pacientes estava no início ou no fim do ciclo menstrual quando foram internadas (qui-quadrado=6,02, p= 0,049. CONCLUSÕES: Existe uma relação entre internação em hospital psiquiátrico e período do ciclo menstrual no qual pacientes esquizofrênicas se encontram.

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

International Nuclear Information System (INIS)

Linares, José Ignacio; Herranz, Luis Enrique; Fernández, Iván; Cantizano, Alexis; Moratilla, Beatriz Yolanda

2015-01-01

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 CO 2 Brayton power cycles (S-CO 2 ) 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-CO 2 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 CO 2 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

Supercritical CO2 Brayton power cycles for DEMO (demonstration power plant) fusion reactor based on dual coolant lithium lead blanket

International Nuclear Information System (INIS)

Linares, José Ignacio; Cantizano, Alexis; Moratilla, Beatriz Yolanda; Martín-Palacios, Víctor; Batet, Lluis

2016-01-01

This paper presents an exploratory analysis of the suitability of supercritical CO 2 Brayton power cycles as alternative energy conversion systems for a future fusion reactor based on a DCLL (dual coolant lithium-lead) blanket, as prescribed by EUROfusion. The main issue dealt is the optimization of the integration of the different thermal sources with the power cycle in order to achieve the highest electricity production. The analysis includes the assessment of the pumping consumption in the heating and cooling loops, taking into account additional considerations as control issues and integration of thermal energy storage systems. An exergy analysis has been performed in order to understand the behavior of each layout. Up to ten scenarios have been analyzed assessing different locations for thermal sources heat exchangers. Neglecting the worst four scenarios, it is observed less than 2% of variation among the other six ones. One of the best six scenarios clearly stands out over the others due to the location of the thermal sources in a unique island, being this scenario compatible with the control criteria. In this proposal 34.6% of electric efficiency (before the self-consumptions of the reactor but including pumping consumptions and generator efficiency) is achieved. - Highlights: • Supercritical CO 2 Brayton cycles have been proposed for BoP of DCLL fusion reactor. • Integration of different available thermal sources has been analyzed considering ten scenarios. • Neglecting the four worst scenarios the electricity production varies less than 2%. • Control and energy storage integration issues have been considered in the analysis. • Discarding the vacuum vessel and joining the other sources in an island is proposed.

Thermodynamic analysis and preliminary design of closed Brayton cycle using nitrogen as working fluid and coupled to small modular Sodium-cooled fast reactor (SM-SFR)

International Nuclear Information System (INIS)

Olumayegun, Olumide; Wang, Meihong; Kelsall, Greg

2017-01-01

Highlights: • Nitrogen closed Brayton cycle for small modular sodium-cooled fast reactor studied. • Thermodynamic modelling and analysis of closed Brayton cycle performed. • Two-shaft configuration proposed and performance compared to single shaft. • Preliminary design of heat exchangers and turbomachinery carried out. - Abstract: Sodium-cooled fast reactor (SFR) is considered the most promising of the Generation IV reactors for their near-term demonstration of power generation. Small modular SFRs (SM-SFRs) have less investment risk, can be deployed more quickly, are easier to operate and are more flexible in comparison to large nuclear reactor. Currently, SFRs use the proven Rankine steam cycle as the power conversion system. However, a key challenge is to prevent dangerous sodium-water reaction that could happen in SFR coupled to steam cycle. Nitrogen gas is inert and does not react with sodium. Hence, intercooled closed Brayton cycle (CBC) using nitrogen as working fluid and with a single shaft configuration has been one common power conversion system option for possible near-term demonstration of SFR. In this work, a new two shaft nitrogen CBC with parallel turbines was proposed to further simplify the design of the turbomachinery and reduce turbomachinery size without compromising the cycle efficiency. Furthermore, thermodynamic performance analysis and preliminary design of components were carried out in comparison with a reference single shaft nitrogen cycle. Mathematical models in Matlab were developed for steady state thermodynamic analysis of the cycles and for preliminary design of the heat exchangers, turbines and compressors. Studies were performed to investigate the impact of the recuperator minimum terminal temperature difference (TTD) on the overall cycle efficiency and recuperator size. The effect of turbomachinery efficiencies on the overall cycle efficiency was examined. The results showed that the cycle efficiency of the proposed

Metabolismo del Ejercicio; Propuesta didáctica para la enseñanza-aprendizaje de la glucólisis y el ciclo de Krebs

OpenAIRE

Ávila Jiménez, Andrés Alberto

2012-01-01

Este trabajo presenta una propuesta didáctica para la enseñanza aprendizaje de la Glucólisis y el Ciclo de Krebs del curso de bioquímica dirigido a estudiantes de primer semestre de la carrera de Cinética Humana y Fisioterapia de la Institución Universitaria Iberoamericana, mediante el diseño de una Unidad Didáctica, abordada desde el estudio de la Glucólisis y el Ciclo de Krebs y sus correlación con la fisiología del deporte y el metabolismo del ejercicio, esta diseñada desde el modelo de re...

Contabilidad de Costos I. - Problemas sobre el Ciclo de la Contabilidad de Costo, a través del estado de costos de producción y ventas

OpenAIRE

Morillo Moreno, Marysela C.

2008-01-01

ÍNDICE Introducción Problemas sobre terminología básica Problemas básicos sobre el Ciclo de la Contabilidad de Costos Problemas sobre contabilización de las actividades relacionadas con los materiales Problemas sobre la contabilización de las actividades relacionadas con la mano de obra Problemas sobre la contabilización de las actividades relacionadas con los costos indirectos de fabricación Problemas sobre el Ciclo de la Contabilida...

La industria del vidrio y el medio ambiente: oportunidad y enfoque del Análisis del Ciclo de Vida

Directory of Open Access Journals (Sweden)

Mari, A.

2002-08-01

Full Text Available The advances in the knowledge of the interaction of human activities with the environment has enabled us to study systematically the available information and to develop assessment systems that permit to have reliable, useful and intercomparable results. A very useful tool for such scope is the Life Cycle Assessment (LCA, which permits to follow stepwise all the interactions involved in a given manufacturing process, from extraction of natural resources up to the end of the useful life of the product and its return to environment. The ordered accumulation of information permits to deep into the so-called Minerals-Material Cycle (MMC, which describes the results of the superposition of anthropic and natural cycles. In the present work the application of LCA to the case of glass products manufacture is examined, in particular to glass containers, using the ISO Standards 14040 to 49. The opportunities and challenges that these procedures involve for the glass industries are also examinated.

El avance en el conocimiento de la interacción de la actividad humana con el medio ambiente ha permitido sistematizar la información al respecto y desarrollar sistemas de evaluación de los resultados de dicha interacción que puedan brindar resultados confiables, útiles y comparables entre sí. Una herramienta sumamente eficaz en este sentido es el denominado Análisis del Ciclo de Vida (ACV , que permite seguir paso por paso todos los procesos interactivos involucrados en una determinada producción, desde la extracción de los recursos naturales - renovables o no renovables - hasta el fin de la vida útil del producto y su vuelta al medio ambiente. La acumulación ordenada de este conocimiento permite profundizar en el estudio del denominado Ciclo Minerales-Materiales (CMM, que describe los resultados de la superposición de los ciclos antrópicos con los ciclos naturales. En el presente trabajo se examina la aplicación del ACV al caso de la

Estudo do ciclo do azoto : Uma Aplicação para o ensino

OpenAIRE

Militão, Cristina Maria Teixeira

2004-01-01

O ciclo do azoto desempenha um papel fundamental na manutenção do equilíbrio da biosfera. O azoto molecular é o gás mais abundante na atmosfera terrestre, porém, as formas combinadas de azoto são relativamente escassas no solo e na água. O azoto é um constituinte importante de proteínas, ácidos nucleicos e coenzimas. Poucos seres vivos, no entanto, podem usar o azoto atmosférico directamente como fonte de azoto. Assim, a disponibilidade dos compostos azotados nos ecossistemas está largamente ...

Calidad total en un modelo integrado de proceso software y ciclo de vida

OpenAIRE

Mon, Alicia; Garzás, Javier

2009-01-01

La modelización del Proceso Software constituye un marco de referencia para la organización de las actividades que involucran todas las etapas del desarrollo. La representación del ciclo de vida define los estados por los que pasa un producto software y la representación del proceso software define el conjunto de actividades esenciales no ordenadas en el tiempo que requiere el desarrollo de software. En el presente artículo se exponen los avances de una investigación que propone una modeli...

Ciclo estral del ratón hembra intacto y ovariectomizado

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Joel Ramírez Emiliano

2012-03-01

Full Text Available The vaginal epithelial changes document reproductive cycles and provide an index of the functional status of the hypothalamic-pituitary-ovarian axis. However, it is necessary to understand the vaginal cytology relationship. In our work we study the vaginal epithelium of intact and ovariectomized female mice. We analyzed young, middle aged and aged vaginal cytology and compared them with an ovariectomized group. The results show that female young intact mice manifest a four days estrous cycle phases: estrous, metaestrous, diestrous and proestrous. In contrast, female middle aged and aged mice showed the persistence of diestrous phase. Ovariectomized mice showed a similar cytology than the middle aged and aged intact ones. In conclusion, the vaginal cytology evaluates the reproductive axis integrity and reflects the circulating sexual hormones levels action and/or modification, which could produce transient changes in behavior.Los cambios del epitelio vaginal documenta los ciclos reproductivos, el estado funcional del eje hipotálamo-hipófisis-ovario asociados con cambios en la conducta. Sin embargo, es necesario conocer más sobre la relación citológica vaginal. En este trabajo se estudiaron las diferencias del epitelio vaginal de ratones hembra intactas y ovariectomizadas. Se analizó la citología vaginal de ratones hembra jóvenes, maduras y ancianas, y se comparó con un grupo ovariectomizado. Los resultados muestran que los ratones hembra intactas jóvenes presentaron las cuatro etapas del ciclo estral: estro, metaestro, diestro y proestro. En contraste, las hembras maduras y ancianas presentaron la fase de diestro persistente. Los ratones ovariectomizados presentaron una citología similar a la de los ratones intactos maduros y ancianos. En conclusión, la citología vaginal evalúa la integridad del eje reproductivo y refleja la acción y/o modificación de los niveles de las hormonas sexuales circulantes (los cuales pueden afectar la

Avaliação de probiótico na alimentação de poedeiras comerciais no segundo ciclo de postura

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R.V. Nunes

2013-02-01

Full Text Available Avaliou-se o efeito da inclusão de probiótico sobre o desempenho e a qualidade dos ovos de poedeiras semipesadas no segundo ciclo de postura. Foram utilizadas 450 aves com 69 semanas de idade, distribuídas aleatoriamente em um delineamento inteiramente ao acaso, em cinco tratamentos, seis repetições e 15 aves por unidade experimental. A ração experimental foi à base de milho e farelo de soja e suplementada com probiótico composto por Lactobacillus acidophilus, Streptococcus faecium e Bifidobacterium bifidum. O experimento teve a duração de 16 semanas e foi dividido em quatro períodos de 28 dias cada, nos quais as aves receberam cinco rações experimentais contendo diferentes porcentagens de inclusão de probiótico, 0; 0,05; 0,10; 0,15 e 0,20%. Não foi observado efeito (P>0,05 da inclusão de probiótico sobre o desempenho e a qualidade dos ovos de galinhas poedeiras no segundo ciclo de postura. A inclusão de 0,10% de probiótico influenciou negativamente a gravidade específica dos ovos. A utilização de probiótico para galinhas no segundo ciclo de postura não interfere na produção e na qualidade dos ovos.

Exploración y explotación de los recursos de red y ciclo de vida

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Angeles Gallego

2016-06-01

Full Text Available La gestión de los recursos de red, entendidos como aquellos que son propiedad de los socios de una empresa y a los que accede a través de sus relaciones, es una cuestión básica en el desarrollo de alianzas y acuerdos. El tipo de recursos de red que serán necesarios para la empresa puede estar condicionado por el momento del ciclo de vida en que se encuentre y de si tiene una actitud de exploración o de explotación en el diseño y gestión de sus estrategias de cooperación. Se plantea una nueva consideración del ciclo de vida como un continuo entre empresas jóvenes y empresas consolidadas. Este trabajo analiza estas relaciones en el sector de las aerolíneas a nivel global. Los resultados muestran que las empresas consolidadas siguen simultáneamente un comportamiento de exploración y de explotación y que cuando se dan estos últimos se buscan recursos básicamente ligados al conocimiento y a la tecnología

Histología del ovario y ciclo reproductivo de Columbina picui (Temminck, 1813 (Aves: Columbidae en Córdoba, Argentina

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Elsa Inés Altamirano

2011-07-01

Full Text Available Con la finalidad de caracterizar el ciclo reproductivo anual de Columbina picui se realizó el análisis estructural y cuantitativo de los ovarios de ejemplares adultos recolectados entre los años 2005—2006 en la Sierra de Macha (Totoral, Córdoba, Argentina. Durante la fase de recrudescencia gonadal (junio a marzo, se determinaron tres valores máximos; el primero en junio, resultado de la ovipostura de las hembras subadultas (plumaje de adultos y vestigios de la Bursa de Fabricius; los restantes valores se registraron uno en septiembre y el otro en enero correspondiendo al de las hembras adultas. La regresión ovárica se inició a partir de la incubación de los huevos y el reposo gonadal de la mayoría de las aves entre abril y mayo. Se identificaron dos tipos atresia folicular: a no bursting, la pared folicular se mantiene intacta, comprende a la lipoidal (ovocitos primordiales y a la lipoglandular (folículos previtelogénicos y vitelogénicos pequeños, ambos procesos se visualizaron durante todo el ciclo reproductivo y b bursting las paredes foliculares se rompen, afecta a los folículos vitelo- génicos menores de 800 μm y sólo fue detectada posterior a la ovipostura. El ciclo reproductivo de C. picui se caracterizo por alta frecuencia de hembras con capacidad de reproducirse durante la mayor parte del año y la prolongada fase de recrudescencia gonadal.

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.

Thermodynamic analyses and optimization of a recompression N2O Brayton power cycle

International Nuclear Information System (INIS)

Sarkar, Jahar

2010-01-01

Thermodynamic analyses and simultaneous optimizations of cycle pressure ratio and flow split fraction to get maximum efficiency of N 2 O recompression Brayton cycle have been performed to study the effects of various operating conditions and component performances. The energetic as well as exergetic performance comparison with its counterpart recompression CO 2 cycle is presented as well. Optimization shows that the optimum minimum cycle pressure is close to pseudo-critical pressure for supercritical cycle, whereas saturation pressure corresponding to minimum cycle temperature for condensation cycle. Results show that the maximum thermal efficiency increases with decrease in minimum cycle temperature and increase in both maximum cycle pressure and temperature. Influence of turbine performance on cycle efficiency is more compared to that of compressors, HTR (high temperature recuperator) and LTR (low temperature recuperator). Comparison shows that N 2 O gives better thermal efficiency (maximum deviation of 1.2%) as well as second law efficiency compared to CO 2 for studied operating conditions. Component wise irreversibility distribution shows the similar trends for both working fluids. Present study reveals that N 2 O is a potential option for the recompression power cycle.

Ciclo diário e semidiário de precipitação na costa norte do Brasil Diurnal and semidiurnal rainfall cycle over north coastland of Brazil

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Cláudio Moisés Santos Silva

2013-03-01

Full Text Available Estudou-se o ciclo diário e o ciclo semidiário da precipitação na região costeira do Norte do Brasil. Usou-se 13 anos de dados ininterruptos de precipitação estimados através do algoritmo 3B42_V6 do projeto TRMM. Os ciclos foram analisados por quadrimestres. Para obter informações sobre amplitude, fase e fração de variância de cada ciclo, utilizou-se a análise harmônica do ciclo composto no período de 24 horas para cada quadrimestre. Regiões mais próximas da costa apresentaram ciclos modulados por mecanismos oceânicos e, portanto, tendem a apresentar o máximo de precipitação no início da manhã e a noite. Regiões mais afastadas da costa apresentaram máximos às 2100 UTC (17:00 HL em função dos mecanismos de convecção local. A região Nordeste do Pará apresentou as maiores amplitudes de precipitação. Durante o quadrimestre de janeiro a abril observou-se as maiores taxas de precipitação. Não há variações sazonais significativas na fase dos ciclos. Os dois harmônicos correspondem a cerca de 80% do total da variância diária dos dados. No final, algumas sugestões de trabalhos futuros e aplicabilidade dos dados do 3B42_V6 são discutidas.The diurnal and semidiurnal rainfall cycles observed over the Brazilian North coastland were studied. A 13 years rainfall dataset derived by the 3B42_V6 algorithm was used. To obtain the amplitude, phase, and variance of each cycle the harmonic analysis was applied to the mean rainfall of 24 hours. Coastlands areas showed cycles modulated by oceanic mechanisms, thus the maximum rainfall was observed at early-morning and nighttime. Inland regions exhibited maximum rainfall at 2100 UTC (17:00 LST due the local convection mechanism. The highest amplitude of precipitation was observed over the Northeast of the Pará State. The highest rainfall rates were observed during January to April period. The phase of each cycle do not presented significant seasonal variation. The diurnal

Evolution and comparison of speed, cycle frequency, cycle length and cycle index on 200-m test in young paddlers Evolución y comparación de la velocidad, frecuencia, longitud e índice de ciclo sobre 200 m en palistas infantiles de diferentes modalidades

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V. Ferrer

2010-09-01

Full Text Available

Speed evolution, cycle frequency, cycle length and cycle index were analysed during a 200-m maximal test, in young paddlers (23 kayak men, 22 kayak women and 20 canoe men; 13^-14 years-old. Recordings were taken from a boat following each test and switched from analogue to digital format to measure the variables cited above. Evolution was similar in three categories. The speed and cycle index decreased through the test after the first 50 m, while the cycle length was stable. The cycle frequency had a progressive decrease along the distance. Men kayak got higher values in all the variables than women kayak and canoeist, but only were significantly higher in speed and cycle index. Lower values of cycle length and cycle frequency were obtained from canoe men and kayak women, respectively.
Key Words: speed, cycle frequency, cycle length, cycle index, paddlers.

Avaliação térmica e reológica do ciclo de cura do pré-impregnado de carbono/epóxi

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Costa Michelle L.

2003-01-01

Full Text Available Parâmetros cinéticos e reológicos relacionados com o ciclo de cura de um sistema de pré-impregnado de resina epóxi (F584/fibra de carbono (prepreg foram determinados pelo uso de análises térmicas (DSC e DMA e reológicas. Os parâmetros determinados foram utilizados para avaliar o ciclo de cura hoje utilizado industrialmente no processamento de compósitos poliméricos pelo uso do prepreg em estudo.Baseando-se nos resultados das análises térmicas realizadas foi constatado para o sistema estudado que a cinética de cura é de ordem n = 1,3 e que a razão de aquecimento mais apropriada na obtenção de compósito polimérico é de 2,5 °C/min, pois esta razão de aquecimento proporciona um ciclo de cura a temperaturas mais baixas, quando comparada às demais razões estudadas, 5 e 10°C/min, favorecendo uma cura mais homogênea e melhor controlada.

Ciclos históricos da violência na América Latina

OpenAIRE

Fandino Marino, Juan Mario

2004-01-01

O trabalho aborda a questão da violência na América Latina dentro de uma perspectiva histórica ampla. Analisa como o ciclo atual orienta-se para a superação democrática da violência, mas a economia de entorpecentes ameaça desvirtuá-lo pela contaminação do tecido moral em construção pelo crime. Palavras-chave: violência; política e instituições; América Latina. This essay addresses the question of violence in Latin America from a broad historical viewpoint. It analyzes how the existing cycl...

Propuesta de Ciclo de Vida y Mapa de Actividades para Proyectos de Explotación de Información

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Hernán Arboleya

2013-03-01

Full Text Available La Explotación de la Información es una sub-disciplina informática que le aporta herramientas a la Inteligencia del Negocio [18] para poder transformar la información en conocimiento [15] que sirva de base para llevar a cabo la toma de decisiones dentro de las organizaciones. Dado que este tipo de proyectos se diferencian a los proyectos convencionales de construcción de software y que la metodologías existente para Proyectos de Explotación de Información no contemplan ni tiene en cuenta los riesgos que dentro de los mismos pueden ocurrir, en esta investigación se propone el diseño de un Modelo de Ciclo de Vida especifico que tenga un análisis de los riesgos. Posteriormente se plantea la construcción de un Mapa de Actividades teniendo en cuenta el Modelo de Ciclo de Vida desarrollado y los procesos del Modelo de Procesos seleccionado.

Influência do período de quiescência dos ovos sobre o ciclo de vida de Aedes aegypti (Linnaeus, 1762 (Diptera, Culicidae em condições de laboratório

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Silva Heloisa Helena Garcia da

1999-01-01

Full Text Available Estudou-se a influência do período de quiescência dos ovos no ciclo de vida de Aedes aegypti (Linnaeus, 1762 (Diptera, Culicidae em condições de laboratório, na busca de informações que possam melhorar o direcionamento das ações de controle, pois sabe-se que o ovo é a forma mais resistente do ciclo biológico, possibilitando ao mosquito ampla sobrevida, devido à resistência às adversidades climáticas. Os experimentos foram realizados numa câmara biológica, mantida à temperatura de 28 ± 1oC, com umidade relativa de 80 ± 5% e fotofase de 12 horas. Apresentam-se os dados da influência de diferentes períodos de quiescência sobre a eclosão das larvas, desenvolvimento larval e pupal, ciclo evolutivo. Verificou-se o efeito altamente significativo do período de quiescência na eclosão das larvas. O período de quiescência não influenciou nas durações dos períodos de incubação, larval e pupal. Constatou-se que ovos de um mesmo período de quiescência apresentaram períodos de incubação estatisticamente diferentes entre si. As larvas eclodiam em grupos, definidos pela incubação, e este efeito de grupo foi significativo na duração do ciclo. Pode-se afirmar que, em 99,8% dos ciclos, a variação foi determinada pela incubação.

Multi-objective thermodynamic optimization of an irreversible regenerative Brayton cycle using evolutionary algorithm and decision making

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Rajesh Kumar

2016-06-01

Full Text Available Brayton heat engine model is developed in MATLAB simulink environment and thermodynamic optimization based on finite time thermodynamic analysis along with multiple criteria is implemented. The proposed work investigates optimal values of various decision variables that simultaneously optimize power output, thermal efficiency and ecological function using evolutionary algorithm based on NSGA-II. Pareto optimal frontier between triple and dual objectives is obtained and best optimal value is selected using Fuzzy, TOPSIS, LINMAP and Shannon’s entropy decision making methods. Triple objective evolutionary approach applied to the proposed model gives power output, thermal efficiency, ecological function as (53.89 kW, 0.1611, −142 kW which are 29.78%, 25.86% and 21.13% lower in comparison with reversible system. Furthermore, the present study reflects the effect of various heat capacitance rates and component efficiencies on triple objectives in graphical custom. Finally, with the aim of error investigation, average and maximum errors of obtained results are computed.

Investigação de perdas devido ao trabalho inacabado e o seu impacto no tempo de ciclo dos processos construtivos

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Paulo Ricardo Ramos Santos

Full Text Available Resumo As perdas na construção civil constituem um entrave à melhoria da produtividade. Dentre os diversos tipos de perdas, o making-do se destaca por representar uma fonte de outras perdas. Fireman et al. (2013, ao estudarem o making-do, concluíram que ele pode ser desencadeado por um tipo de perda geral, denominada de trabalho inacabado. O objetivo do presente trabalho foi investigar a ocorrência do trabalho inacabado nos processos construtivos e o seu impacto no tempo de ciclo dos serviços. A pesquisa foi de um levantamento de campo em cinco canteiros, envolvendo observação direta. Utilizou-se como ferramentas de pesquisa: formulário, questionários e checklist, adaptados da literatura para identificação e classificação do trabalho inacabado, bem como aferição do seu impacto no tempo de ciclo. Houve também entrevistas não estruturadas com os gerentes de obras, mestres e encarregados. Os resultados mostraram que as falhas no sequenciamento das tarefas associadas com falhas na gestão da qualidade serviram de desencadeadores para o trabalho inacabado. Notou-se que os canteiros que apresentaram planos de curto prazo formalizados atenuaram os impactos desse tipo de perda. Na maioria das obras o tempo de ciclo previsto não foi cumprido, observando-se que aquelas que tinham equipe administrativa mais encorpada obtiveram acréscimo de tempo menor.

HERRAMIENTAS PARA LA GESTIÓN DE PROCESOS DE NEGOCIO Y SU RELACIÓN CON EL CICLO DE VIDA DE LOS PROCESOS DE NEGOCIO: UNA REVISIÓN DE LITERATURA

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Ernesto A. Galvis-Lista

2014-01-01

Full Text Available Este artículo presenta una revisión sobre la oferta de herramientas de tecnología de información, TI, para la gestión de procesos de negocio (Business Process Management - BPM. Para esto, se desarrolla una conceptualización de las etapas del ciclo de vida de los procesos de negocio y se realiza una descripción de las herramientas de TI desde una perspectiva funcional. Luego, se realiza un mapeo para ubicar las herramientas de TI en cada una de las fases del ciclo de vida. Este trabajo se constituye en una referencia para los profesionales que desarrollan iniciativas de BPM, así como para investigadores, profesores y estudiantes interesados en el tema. La principal contribución del trabajo es la conceptualización de las etapas del ciclo de vida de BPM y la identificación de herramientas de TI que soportan cada una de estas.

Modeling and sizing of the heat exchangers of a new supercritical CO2 Brayton power cycle for energy conversion for fusion reactors

International Nuclear Information System (INIS)

Serrano, I.P.; Cantizano, A.; Linares, J.I.; Moratilla, B.Y.

2014-01-01

Highlights: •We propose a procedure to model the heat exchangers of a S-CO2 Brayton power cycle. •Discretization in sub-heat exchangers is performed due to complex behavior of CO 2 . •Different correlations have been tested, verifying them with CFD when necessary. •Obtained sizes are agree with usual values of printed circuit heat exchangers. -- Abstract: TECNO F US is a research program financed by the Spanish Government to develop technologies related to a dual-coolant (He/Pb–Li) breeding blanket design concept including the auxiliary systems for a future power reactor (DEMO). One of the main issues of this program is the optimization of heat recovery from the reactor and its conversion into electrical power. This paper is focused on the methodology employed for the design and sizing of all the heat exchangers of the supercritical CO 2 Brayton power cycle (S-CO2) proposed by the authors. Due to the large pressure difference between the fluids, and also to their compactness, Printed Circuit Heat Exchangers (PCHE) are suggested in literature for these type of cycles. Because of the complex behavior of CO 2 , their design is performed by a numerical discretization into sub-heat exchangers, thus a higher precision is reached when the thermal properties of the fluids vary along the heat exchanger. Different empirical correlations for the pressure drop and the Nusselt number have been coupled and assessed. The design of the precooler (PC) and the low temperature recuperator (LTR) is also verified by simulations using CFD because of the near-critical behavior of CO 2 . The size of all of the heat exchangers of the cycle have been assessed

Relatório do Mestrado em Ensino da Fisica e de Quimica no 3º Ciclo do Ensino Básico

OpenAIRE

Carvalho, Paulo Jorge de Oliveira

2014-01-01

Relatório de estágio do Mestrado em Ensino de Física e de Química no 3.º ciclo do Ensino Básico e no Ensino Secundário apresentado à Faculdade de Ciências e Tecnologia da Universidade de Coimbra

Gestão da informação em saneamento básico no Estado do Pará sob o enfoque do ciclo informacional

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Marise Teles Condurú

Full Text Available RESUMO Estudo da gestão da informação por meio da análise do ciclo informacional de saneamento básico no Estado do Pará, como subsídio para implantação e/ou fortalecimento de sistemas de informações em saneamento básico nos municípios paraenses. Metodologicamente, a pesquisa foi desenvolvida sob o enfoque do Ciclo de Transferência de Informação de Lancaster. Foram aplicados questionários para coleta e análise qualitativa dos dados obtidos em órgãos estaduais que desenvolvem ações no setor de Saneamento Básico. A ausência de sistema estadual e municipal de informação em saneamento básico no Estado demonstra a deficiência do ciclo de comunicação e informação do setor. Na pesquisa, foi verificada a falta de registros sistemáticos, de integração, de compartilhamento e de disponibilização da informação produzida. Evidenciou-se, assim, a necessidade de implantação de sistema de informação local como instrumento da política estadual de saneamento básico, visando ao conhecimento informacional do setor e à maior participação dos municípios paraenses no sistema nacional de informação. Para isso, foi proposto o Ciclo Informacional do Saneamento Básico do Pará, o qual contribuirá para a reestruturação da dimensão informacional necessária à elaboração de diagnóstico, ao planejamento e à tomada de decisão no setor.

Entomología forense: el ciclo de vida de la mosca verde Phaenicia eximia (Wiedemann (Diptera: Calliphoridae, como herramienta para estimar el intervalo post-mortem

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Enio B. Cano

2017-03-01

Full Text Available Se estudió el ciclo de vida de la mosca verde Phaenicia eximia (Wiedemann en condiciones controladas de laboratorio a 26 o C, con una humedad relativa de 75% y un período de iluminación de 12 h de luz y 12 h de oscuridad. El tiempo promedio de desarrollo estimado desde la oviposición hasta la salida de los adultos fue de 306 h (una media de casi 13 días. Bajo estas condiciones de temperatura y humedad, los huevos duran cerca de 19 h (0.8 días, las larvas duran unas 170 h (7.1 días y las pupas unas 116 h (4.8 días. En los meses secos y fríos de noviembre y diciembre en condiciones naturales, el ciclo de vida empírico fue de 25 días, implicando que las bajas temperaturas ralentizan el crecimiento y las altas lo aceleran. Se discute acerca de la importancia del ciclo de vida en la estimación del intervalo post-mortem en casos de muertes violentas en Guatemala.

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

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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

Tratamiento de la psicomotricidad en el segundo ciclo de la educación infantil

OpenAIRE

Lasaga Rodríguez, María José; Campos Mesa, María del Carmen; Ries, Francis

2013-01-01

Con nuestra investigación pretendemos conocer el tratamiento que recibe la psicomotricidad en el segundo ciclo de la Educación Infantil, desde la opinión de los maestros que se encuentran desarrollando esta profesión. Para ello hemos pasado un cuestionario desde el año 2005 al 2011 a una muestra de 76 sujetos. Tras los resultados obtenidos podemos concluir que los maestros que imparten docencia en el grado de Educación Infantil consideran importante el trabajo de psicomotricidad en sus clase...

Influencia del ciclo lunar en la captura de langosta espinosa Panulirus argus (Decapoda: Palinuridae en el Golfo de Batabanó, Cuba

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Alexander Lopeztegui

2011-03-01

Full Text Available Muchos procesos biológicos tales como los comportamientos reproductivos y migratorios se han asociado con los ciclos de la luna. Con el objetivo de determinar la relación entre las capturas de langosta espinosa Panulirus argus (Decapoda: Palinuridae y el ciclo lunar, en la zona del Golfo de Batabanó, se correlacionaron los niveles de iluminación nocturna del ciclo lunar (INT con la captura diaria por barco (CDB durante siete meses lunares correspondientes al período de pesca del 2002. Los datos de captura provinieron de las tres empresas pesqueras que realizan su actividad en la zona del Golfo de Batabanó. La relación entre el ciclo lunar y las capturas de langostas fue examinada mediante varios procedimientos estadísticos. Los primeros gráficos realizados, cualitativos, mostraron que no existe relación entre las tasas de captura y el ciclo lunar. Los coeficientes de Spearman calculados, modularmente menores que 0.1 en todos los casos, demostraron cuantitativamente que no existe correlación entre las mencionadas variables. La prueba de Kruskal-Wallis detectó diferencias sólo en una de las tres áreas estudiadas. Las correlaciones cruzadas no detectaron significación en ninguna de las zonas, con coeficientes de correlación cruzada modularmente inferiores a 0.1. A diferencia de lo reportado por otros autores, las capturas de P. argus y el ciclo lunar no presentan correlación significativa en el Golfo de Batabanó.Influence of lunar cycle on catches of spiny lobster Panulirus argus (Decapoda: Palinuridae in the Gulf of Batabanó, Cuba. Many biological processes such as reproductive and migratory behaviours have been associated with moon cycles. In this study, the nocturnal light levels associated with lunar cycle (INT were correlated with daily catch rate of lobster P. argus, during seven lunar months of 2002 fishing period, to determine a possible relationship between these variables. The lobster catches were obtained from three

Thermodynamics Properties of Binary Gas Mixtures for Brayton Space Nuclear Power System

International Nuclear Information System (INIS)

You Ersheng; Shi Lei; Zhang Zuoyi

2014-01-01

Space nuclear power system with closed Brayton cycle has the potential advantages of high cycle efficiency. It can be achieved to limit the specific mass of the system with a competitive design scheme, so as to strengthen the advantage of the nuclear energy applying in space propulsion and electric generating compared to solar or chemical propellant. Whereby, the thermodynamic properties of working fluids have a significant influence on the performance of the plant. Therefore, two binary mixtures helium-nitrogen and helium-carbon dioxide are introduced to analysis the variation in the transport and heat transfer capacity of working fluids. Based on the parameters of pure gases, the heat transfer coefficient, pressure losses and aerodynamic loading are calculated as a function of mole fraction at the temperature of 400 K and 1200 K, as well as the typical operating pressure of 2 MPa. Results indicated that the mixture of helium-carbon dioxide with a mole fraction of 0.4 is a more attractive choice for the high heat transfer coefficient, low aerodynamic loading and acceptable pressure losses in contrast to helium-nitrogen and other mixing ratios of helium-carbon dioxide. Its heat transfer coefficient is almost 20% more than that of pure helium and the normalized aerodynamic loading is less than 34% at 1200 K. However; the pressure losses are a little higher with ~3.5 times those of pure helium. (author)

Profesoras en el tercer ciclo universitario y en los postgrados sobre EEMM

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Isabel de Torres Ramírez

2006-12-01

Full Text Available En este artículo se analiza la presencia de las mujeres en la universidad española, dentro de la enseñanza y la investigación llevada a cabo en el tercer ciclo de los estudios universitarios y en los programas de postgrado que se llevan a cabo dentro del área de conocimiento Estudios de las Mujeres. El objetivo concreto que se persigue es estudiar la presencia de profesoras en los programas de doctorado, en la dirección y en los tribunales de tesis y también en los másters, programas expertos/as y de especialistas vigentes durante el curso 2005-2006.

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

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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

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.

Emulsiones tipo crema preparadas a base de leche de soja 3: Efecto de ciclos de temperatura

Directory of Open Access Journals (Sweden)

Wagner, Jorge R.

2005-09-01

Full Text Available In this work, the effect of temperature cycling on emulsions formulated with reconstituted soy milk, sunflower oil and high melting point milk fat was analysed. The emulsions were prepared at 60 ºC , stored at 4 ºC (3 h, warmed at 40 ºC or 50 ºC (30 min and afterwards recooled at 4 ºC (2h. Although solid fat content of emulsions did not raised after tempering at 40 ºC , increase of G' and G'' was observed only in those formulated with 40 % lipid phase. This phenomenon was attributed to droplet aggregation due to partial melting, recrystallization and reordering of fat crystals in oil droplets. The main droplet destabilization mechanism was the partial coalescence; it was corroborated by nuclear magnetic resonance, differential scanning calorimetry and droplet size distribution studies. On the other hand, the consistency of 20 % of lipid phase emulsion did not increased. Low droplet concentration disfavoured the partial coalescence of droplets. Similar assays on cream at 40 ºC and cream-like soy milk emulsions at 50 ºC , did not show rheological modifications, due to almost total melting of milk fat during tempering.En este trabajo se analizó el efecto de ciclos calentamiento-enfriamiento sobre cremas preparadas a 60 ºC con leche de soja en polvo reconstituida, aceite de girasol y grasa láctea y almacenadas posteriormente a 4 °C durante 3 horas. Los ciclos consistieron en un calentamiento a 40 °C o 50 °C (30 min seguido de un re-enfriamiento a 4 °C (2 horas. En los ensayos realizados sobre cremas formuladas con 40% de fase lipídica se observó un aumento de los valores de G' y G'' después del ciclo 40 °C- 4 °C , a pesar de no haberse observado un aumento en el contenido de grasa sólida. Estos resultados se atribuyen a la formación de agregados de gotas inducida por la fusión parcial, reordenamiento y recristalización de la grasa láctea en las gotas. Estudios de resonancia magnética nuclear de

Identificação de pontos de controle no ciclo de desenvolvimento de produto por meio de modelagem conceitual e mapeamento da informação

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Leonardo Geraldo de Oliveira Gomes

2014-06-01

Full Text Available A complexidade do sistema produtivo e o conteúdo da informação relacionada a ele são os principais elementos deste trabalho. Traz como fio condutor a tentativa do melhor entendimento desta complexidade e da possibilidade do mapeamento e da representação da informação circulante em um sistema para a otimização de seu gerenciamento. O estudo ganha relevância ao se aproximar das atuais discussões e atitudes emergentes no tocante à sustentabilidade, principalmente nas áreas de desenvolvimento de produtos eco-orientados e no gerenciamento dos ciclos de vida. A proposta fundamenta-se na busca pela forma de representar a complexidade envolvida nos sistemas associados ao desenvolvimento do produto, de maneira a possibilitar a otimização da observação e do controle ao longo do seu ciclo de vida. Esta representação, necessariamente de alto nível, deve apresentar diagramas completos com possibilidades de evolução em detrimento das representações gráficas de baixa complexidade comumente utilizados, caracterizadas pelo reducionismo representativo. Procura-se o controle, o mais fino possível, da cadeia produtiva, objetivando maior organização, produtividade e conhecimento detalhado sobre um produto. O mapeamento da complexidade e a identificação dos pontos de controle propiciam um entendimento otimizado do ciclo de vida. Uma possibilidade de tratar a representação deste ciclo de maneira sistêmica, sem o perigo de uma redução em nível crítico da complexidade, está no uso da modelagem conceitual.

La teoría del consumo y de los ciclos en Thorstein Veblen

OpenAIRE

Morero, Hernan; Figueras, Alberto Jose

2015-01-01

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. Thorstein Veblen (1857-1929) is one of the founders of American institutiona...

La escritura como práctica situada en el primer ciclo: promoción de procesos cognitivos y metacognitivos

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OLGA YAMIRA PEÑA GALEANO

2016-01-01

Full Text Available Este trabajo tiene como objetivo presentar resultados de la investigación titulada “El modelo metasociocognitivo. Una alternativa para situar la escritura en contexto” que está fundamentada en la perspectiva sociocultural, el modelo metasociocognitivo y la noción de cognición situada. A nivel metodológico, se aborda el diseño de Investigación Acción, por lo cual se acude a la observación participante, encuestas, entrevistas y registros de clase. En este sentido, se parte del análisis del rastreo de trabajos investigativos, acorde con tres categorías: la escritura en el ciclo uno, los procesos cognitivos y los procesos metacognitivos. Luego se presentan los resultados, organizados en seis hechos, que se derivan del análisis de los procesos de enseñanza y aprendizaje en la producción escrita de los niños en el primer ciclo: estudiantes de grado primero y segundo de básica primaria. Finalmente, se exponen las conclusiones en el ámbito pedagógico, disciplinar e investigativo.

Ciclo político presupuestal y gobiernos con y sin mayoría en México, 1994 y 2006

Directory of Open Access Journals (Sweden)

Marlen R. Reyes-Hernández

2013-01-01

Full Text Available En este documento se analiza el gasto público federal ejercido antes y después de las elecciones presidenciales de 1994 y 2006 en México, para identificar la existencia de un ciclo político presupuestal (cpp. Se extienden los estudios previos al incorporar los efectos de la existencia o no de mayoría del partido del presidente en la Cámara de Diputados en la determinación del presupuesto de egresos. Específicamente, se examinan las reasignaciones que la Cámara de Diputados ha realizado al proyecto de presupuesto enviado por el Ejecutivo federal, así como la presencia de ciclos presupuestales en el gasto propuesto y ejercido por el Ejecutivo y aprobado por la misma Cámara. Se encontró que en un gobierno con mayoría, la composición de la Cámara de Diputados facilita la configuración de un cpp, en tanto que uno sin mayoría no puede evitarlo plenamente.

Definición de un ciclo de movimiento básico para camiones diesel. // Definition of a basic driving cycle for diesel trucks.

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V. Millo Carmenate

2004-05-01

Full Text Available Se define un ciclo básico de movimiento, cuya modelación matemática posibilite la determinación de indicadoresdinámicos básicos y de consumo de combustible para poder comparar vehículos con iguales fines pero con diferenteprocedencia, marca o parámetros constructivos, bajo similares condiciones a los fines de la selección.Palabras claves: Dinámica de vehículos, selección, ciclos de viaje._____________________________________________________________________________Abstract.A basic driving cycle is defined, whose mathematical modeling enable the determination of basic dynamic indicators andfuel consumption in order to compare vehicles with the same purpose but with different origin, brands or constructiveparameters, under similar operating conditions for the selection.Key words: Vehicle dynamics, selection, driving cycle.

Prática de ensino supervisionada em educação pré-escolar e ensino do 1.º ciclo do ensino básico

OpenAIRE

Batista, Sofia Adelaide Pinheiro Miranda

2012-01-01

O presente relatório assenta na descrição dos estágios realizados em educação pré-escolar e 1º Ciclo do Ensino Básico entre fevereiro e junho de 2011 e, outubro e fevereiro de 2012, respetivamente. No âmbito da educação pré-escolar, aceitamos como referenciais pedagógicos o modelo curricular HighScope e as Orientações Curriculares para Educação Pré-escolar. Para o 1º Ciclo do Ensino Básico utilizamos, sempre que foi possível, uma pedagogia de participação, não seguindo um modelo concreto. Tod...

Relación entre las estrategias de aprendizaje y el rendimiento académico de los estudiantes de 1er. y 3er. ciclo de estudios de la Universidad Científica del Perú matriculados en el semestre 2016-I

OpenAIRE

Vildósola Ampuero, Gabriela Petronila

2017-01-01

Establece la relación que existe entre las estrategias de aprendizaje y el rendimiento académico de los estudiantes del 1er. y 3er. ciclo de estudios de la Universidad Científica del Perú (UCP), matriculados en el semestre 2,016-I. La investigación es de tipo descriptiva correlacional. Utiliza una muestra de 238 estudiantes del 1er ciclo y 174 estudiantes del 3er ciclo. Utiliza como herramienta un inventario de cotejo de información de estrategias de aprendizajes que consta de 33 preguntas qu...

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...

Práticas de leitura no 1.º ciclo do ensino básico

OpenAIRE

Mesquita, Elza

2007-01-01

A presente comunicação pretende reflectir sobre o desenvolvimento de alguns projectos que os alunos da formação inicial têm vindo a implementar em contexto de 1.º Ciclo do Ensino Básico. Portanto, o que vos apresento, constitui-se num conjunto de experiências onde se promoveram atitudes investigativas face às práticas, relativamente à leitura e, sobretudo, no que diz respeito à exploração de técnicas de leitura e métodos de escrita criativa em turmas do 3.º e 4.º anos. Nos cont...

Um método de inventário do ciclo de processo de manufatura

OpenAIRE

Rossato, Ivete de Fatima

2002-01-01

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia de Produção. A crescente preocupação com os impactos ambientais gerados pelo fornecimento de bens e serviços tem despertado na sociedade um interesse pelo desenvolvimento de novas ferramentas e métodos que auxiliem na compreensão, controle e redução desses impactos. Este trabalho apresenta uma proposta de um método para realizar o inventário do ciclo de vida de um proces...

A implementação dos ciclos de formação em Porto Alegre: para além de uma discussão do espaço-tempo escolar

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Andréa Rosana Fetzner

2009-01-01

Full Text Available El artículo propone una reflexión sobre las condiciones en que los ciclos de formación se llevaron a cabo en la red municipal de educación en Porto Alegre. Se sitúan las relaciones entre la sociedad y la cultura escolar, presentando la génesis del concepto de ciclos, con referencia a los estudios de Vygotsky y Wallon; se retoman algunas propuestas educacionales consideradas inéditas viables en la educación brasileña, tales como la Escuela Primaria Integral y la educación popular; y, al final, se presentan algunas situaciones específicas de Porto Alegre en relación con otras propuestas de ciclos contemporáneos. El concepto de cultura escolar se centra en el análisis de las prácticas e indica la transición de procesos escolares conservadores hacia procesos democratizantes.

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

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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.

Método para quantificação do consumo energético no ciclo de vida de equipamentos hidrossanitários

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Andreza Kalbusch

Full Text Available A escolha entre diferentes materiais, produtos ou sistemas empregados na construção civil pode levar em consideração diferentes critérios, sejam estes econômicos, sociais, culturais e ambientais. No caso de equipamentos hidrossanitários, a avaliação econômica e do consumo de recursos, tais como a água, são os critérios mais comumente empregados. O presente artigo objetiva a proposição de um método para quantificação do consumo energético de equipamentos hidrossanitários com base no conceito de Análise do Ciclo de Vida. Essa quantificação permite a comparação entre o desempenho de diferentes equipamentos hidrossanitários com base no dispêndio energético total. No presente artigo o método proposto é aplicado em um estudo de caso analisando dois modelos de torneira (convencional e com fechamento hidromecânico. O consumo energético total no ciclo de vida das torneiras convencional e economizadora de água utilizadas no estudo foi de respectivamente, 151,66 MJ e 127,58 MJ. A etapa de uso das torneiras apresentou peso preponderante nos resultados, com participação de 64,6% para a torneira convencional e 56,5% para a torneira com fechamento hidromecânico. O método proposto se mostrou adequado para quantificação do consumo energético no ciclo de vida e posterior escolha entre diferentes equipamentos hidrossanitários que exerçam a mesma função.

Ciclo vital de Pegoscapus aff. silvestrii (Hymenoptera:Agaonidae, polinizador de Ficus andicola (Moraceae

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Sergio Jansen G.

2006-07-01

de sexo en las poblaciones de avispas que emergen de los frutos de cada especie de Ficus. A pesar de esto, son pocos los estudios que tratan la biología básica de las avispas, especialmente para el Neotrópico. El presente trabajo describe el ciclo vital de la avispa agaónida Pegoscapus aff. silvestrii, polinizadora de Ficus andicola, a partir de un seguimiento intensivo a los frutos de un árbol. La especie tiene cinco estadíos larvales que juntos abarcaron 80 días desde la postura, con presencia de aparato bucal en los últimos dos. A éstos les sigue una pupa del tipo exarata y finalmente el adulto.

CARACTERIZAÇÃO DA ATIVIDADE PRÓ-OXIDANTE DE DIFERENTES AGENTES E ESTUDO DO POTENCIAL ANTIOXIDANTE DE INTERMEDIÁRIOS DO CICLO DE KREBS SOBRE ALTERAÇÕES OXIDATIVAS INDUZIDAS IN VITRO

OpenAIRE

Robson Luiz Puntel

2008-01-01

Dados prévios da literatura têm mostrado que alguns intermediários do ciclo de Krebs podem agir como antioxidantes em diversos modelos, tanto in vitro, quanto in vivo. Porém, o(s) mecanismo(s) através dos qual(is) esses intermediários exercem suas atividades antioxidantes não são completamente entendidas. Considerando a escassez de dados na literatura a respeito do efeito dos intermediários do ciclo de Krebs durante situações de estresse oxidativo, o presente trabalho teve por objetivo determ...

Ciclos de vida comparados de Aedes aegypti (Diptera, Culicidae do semiárido da Paraíba

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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.

Modeling and sizing of the heat exchangers of a new supercritical CO{sub 2} Brayton power cycle for energy conversion for fusion reactors

Energy Technology Data Exchange (ETDEWEB)

Serrano, I.P.; Cantizano, A.; Linares, J.I., E-mail: linares@upcomillas.es; Moratilla, B.Y.

2014-10-15

Highlights: •We propose a procedure to model the heat exchangers of a S-CO2 Brayton power cycle. •Discretization in sub-heat exchangers is performed due to complex behavior of CO{sub 2}. •Different correlations have been tested, verifying them with CFD when necessary. •Obtained sizes are agree with usual values of printed circuit heat exchangers. -- Abstract: TECNO{sub F}US is a research program financed by the Spanish Government to develop technologies related to a dual-coolant (He/Pb–Li) breeding blanket design concept including the auxiliary systems for a future power reactor (DEMO). One of the main issues of this program is the optimization of heat recovery from the reactor and its conversion into electrical power. This paper is focused on the methodology employed for the design and sizing of all the heat exchangers of the supercritical CO{sub 2} Brayton power cycle (S-CO2) proposed by the authors. Due to the large pressure difference between the fluids, and also to their compactness, Printed Circuit Heat Exchangers (PCHE) are suggested in literature for these type of cycles. Because of the complex behavior of CO{sub 2}, their design is performed by a numerical discretization into sub-heat exchangers, thus a higher precision is reached when the thermal properties of the fluids vary along the heat exchanger. Different empirical correlations for the pressure drop and the Nusselt number have been coupled and assessed. The design of the precooler (PC) and the low temperature recuperator (LTR) is also verified by simulations using CFD because of the near-critical behavior of CO{sub 2}. The size of all of the heat exchangers of the cycle have been assessed.

IMPACT World+: Una nueva metodología global y regionalizada de Análisis del Impacto de Ciclo de Vida

DEFF Research Database (Denmark)

Bulle, C.; Jolliet, O.; Humbert, S.

La mayoría de los impactos ambientales modelados en el análisis del impacto del ciclo de vida (AICV) son regionales o locales. Sin embargo, las metodologías de AICV actuales ofrecen factores de caracterización genéricos, representando las condiciones medias de un área específica (país o continente...

La desintegración familiar y el rendimiento académico de los estudiantes del V Ciclo de la Red 01 Sol Mar y Arena, UGEL 04-Comas, 2012

OpenAIRE

Mancisidor Pasco, Freedy Edulfo

2013-01-01

La presente investigación trató sobre la relación entre la desintegración familiar y el rendimiento académico en el área de comunicación integral en los estudiantes del V ciclo Red Nº 01 “Sol, Mar y Arena”-UGEL 04-Comas, El objetivo general fue establecer la relación entre la desintegración familiar y el rendimiento académico. El diseño de investigación es no experimental, transeccional y correlacional; la muestra estuvo conformada por 288 estudiantes del V, ciclo a quien...

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

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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.

A Conceptual Study of Using an Isothermal Compressor on a Supercritical CO_2 Brayton Cycle for SMART Application

International Nuclear Information System (INIS)

Heo, Jin Young; Lee, Jeong Ik; Ahn, Yoonhan

2016-01-01

To maximize the benefits of modularization, the supercritical CO_2 (S-CO_2) power cycle can replace the conventional steam Rankine cycle to increase the cycle efficiency and reduce its system size. Previous works have been conducted to evaluate potential advantages of applying the S-CO_2 cycle to SMRs, specifically to SMART (System-integrated Modular Advanced Reactor) which is an integral SMR developed by KAERI (Korea Atomic Energy Institute). One of the optimized S-CO_2 cycle layouts is the recompressing Brayton cycle. This paper attempts to improve the cycle layout by replacing the conventional compressor with an isothermal compressor, of which its potential in the S-CO_2 power cycle is conceptually being evaluated. The SMR applications, for which SMART reactor has been represented, can take advantage of the currently developing S-CO_2 cycle greatly by the reduction of size. By introducing the isothermal compressor, the cycle layout considered in has been further improved by increasing the cycle net efficiency by around 0.5%

La generación de empleo por maquiladoras en México y los ciclos económicos de Estados Unidos 1978-1985

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Jesús H. Amozurrutia C.

1988-01-01

Full Text Available 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, estableciendo los criterios correspondientes. Los ciclos del empleo en la industria maquiladora mexicana se relacionan positivamente con el índice de producción industrial estadounidense. Entre sus conclusiones destaca que el tipo de cambio no resultó ser un factor que hubiera alentado la generación de empleos por parte de las maquiladoras.

Cost Analysis of an Air Brayton Receiver for a Solar Thermal Electric Power System in Selected Annual Production Volumes

Science.gov (United States)

1981-01-01

Pioneer Engineering and Manufacturing Company estimated the cost of manufacturing and Air Brayton Receiver for a Solar Thermal Electric Power System as designed by the AiResearch Division of the Garrett Corporation. Production costs were estimated at annual volumes of 100; 1,000; 5,000; 10,000; 50,000; 100,000 and 1,000,000 units. These costs included direct labor, direct material and manufacturing burden. A make or buy analysis was made of each part of each volume. At high volumes special fabrication concepts were used to reduce operation cycle times. All costs were estimated at an assumed 100% plant capacity. Economic feasibility determined the level of production at which special concepts were to be introduced. Estimated costs were based on the economics of the last half of 1980. Tooling and capital equipment costs were estimated for ach volume. Infrastructure and personnel requirements were also estimated.

La crisis del ciclo neoliberal en los países de la región andina

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Eudis F. Fermín T.

2010-01-01

Full Text Available En el artículo se estudia la crisis del ciclo neoliberal en los países de la Región Andina en el contexto delos cambios políticos latinoamericanos. Es una investigación documental-analítica, fundamentada en una revisión bibliográfica y en la clasificación del material para el procesamiento de los datos recolectados, la interpretación de esos datos parte de la categoría crisis del ciclo neoliberal. El neoliberalismo reduce las funciones de los Estados andinos a las áreas medulares: educación, salud y seguridad ciudadana, privatiza las empresas estatales y los servicios públicos, donde la ¿razón del mercado¿ priva la relación Sociedad-Estado, con consecuencias nefastas para la población, originando en el tiempo el surgimiento democrático de gobiernos anti-neoliberales. Se concluye que en los albores del siglo XXI el neoliberalismo entra en crisis, cuando el mercado manifiesta su incapacidad de contrarrestar los altos índices de pobreza y el deterioro de las condiciones vida de los ¿pueblos¿, los gobiernos andinos de izquierda introducen cambios en los sistemas políticos, redimensionando las políticas de ajuste macro-económico y rechazan los acuerdos bilaterales y multilaterales promotores de libre mercado en el seno del sistema institucional de integración andina.

DEZ PRINCÍPIOS PARA REPENSAR O MALL OU A MANUTENÇÃO DO CICLO DO LUCRO?

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Fernando Garrefa

2011-07-01

Full Text Available O presente artigo faz parte de uma pesquisa ainda em andamento, tomada a partir da conclusão de tese de doutorado intitulada: Shopping centers: de centro de abastecimento a produto de consumo (GARREFA, 2007. Na tese, identificou-se o encurtamento do ciclo de vida dos shopping centers e seu enquadramento a uma condição de semelhante à dispensada aos produtos de consumo, a efemeridade e a descartabilidade. Com o intuito de dar segmento às constatações elaboradas na tese, busca-se analisar os desdobramentos atuais desse fenômeno, concentrando-se no modelo que tem sido difundido com intensidade nos Estados Unidos e ainda timidamente no Brasil: os shopping centers com os corredores de compra descobertos, apelidados de open-air mall. Este modelo foi definido após conferência do Urban Land Institute intitulado: Dez princípios para repensar o mall cuja publicação gerou uma cartilha de princípios visando uma melhor relação entre shopping centers e a cidade. A primeira vista, o open-air mall parece mais atento às peculiaridades das cidades estabelecendo com elas uma sinergia positiva. No entanto, um olhar mais atento mostra que se configuram acima de tudo mais uma tentativa de manutenção do ciclo do lucro, um modismo que tende a ser descartado com mais rapidez que seus predecessores legando grandes impactos às cidades.

Contributo das ilustrações para a construção das representações de género na criança do 1º ciclo

OpenAIRE

Grilo , Raquel Filipa Lopes

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. O presente relatório de Estágio foi elaborado para a conclusão do Mestrado em Educação Pré-Escolar e Ensino do 1º Ciclo do Ensino Básico, da Escola Superior de Educação de Castelo Branco. A prática supervisionada teve uma duração de catorze semanas...

Resultados das técnicas de reprodução assistida em mulheres doadoras de oócitos no ciclo de tratamento Outcome of assisted reproductive technologies in women with oocyte donation in the treatment cycle

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Edvaldo Cavalcante

2005-11-01

Full Text Available OBJETIVO: comparar os resultados de ciclos de reprodução assistida em mulheres doadoras de oócitos no ciclo de tratamento com o de mulheres não doadoras. MÉTODOS: foram avaliadas, retrospectivamente, as taxas de gravidez, implantação e abortamento de 50 pacientes que doaram oócitos durante o ciclo de reprodução assistida (grupo de doadoras e de 50 pacientes que não doaram oócitos (grupo de não-doadoras, em clínica privada de reprodução assistida em São Paulo, entre os anos de 2001 e 2003. Os critérios de inclusão no estudo foram os seguintes: idade menor que 35 anos; ciclos menstruais regulares; dosagem basal de FSH0,05. CONCLUSÃO: em pacientes que recuperam mais de seis oócitos, a doação de oócitos no ciclo de tratamento não prejudica os resultados dos ciclos de reprodução assistida e não eleva as taxas de abortamento.PURPOSE: to compare the outcome of treatment in patients undergoing assisted reproductive technology (ART cycles who donated eggs during their own ART treatment with the outcome of patients undergoing ART without egg donation. METHODS: we studied retrospectively the pregnancy and implantation rates of 50 patients who donated eggs during the course of their ART treatment (donor group, and the pregnancy and implantation rates of 50 patients who underwent ART cycles and kept all their eggs (non-donor group. between the years 2001-2003. The inclusion criteria used were as follows: age 0.05. CONCLUSION: this study suggests that in patients who produce more than 6 oocytes, egg donation in the treatment cycle does not influence adversely the outcome of ART cycles and does not increase the miscarriage rate.

Composição físico-química de uvas para vinho fino em ciclos de verão e inverno

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Renata Vieira da Mota

2010-12-01

Full Text Available Este trabalho teve como objetivo avaliar o potencial de maturação das cultivares Pinot Noir, Tempranillo, Merlot, Cabernet Sauvignon, Syrah, Chardonnay e Sauvignon Blanc submetidas ao regime de dupla poda, em Cordislândia, região cafeeira do sul de Minas Gerais. As plantas foram submetidas a dois ciclos de produção, um de primavera-verão, compreendido entre agosto e janeiro, e outro ciclo de outono-inverno, entre janeiro e julho. Como parâmetros de qualidade, foram avaliados os diâmetros transversal e longitudinal da baga, acidez, ácidos tartárico e málico, pH, sólidos solúveis, antocianinas, fenólicos totais e os teores de glicose, frutose e sacarose. Todas as variedades apresentaram maiores teores de pH, sólidos solúveis, açúcares, antocianinas e fenólicos totais, e redução nos diâmetros transversal e longitudinal na safra de inverno. A cultivar Syrah destacou-se das demais no conteúdo de antocianinas e fenólicos totais tanto no verão quanto no inverno, entretanto apresentou o menor conteúdo de açúcares. A alteração do ciclo de produção da videira através da técnica da dupla poda para colheita, no período de inverno, na região cafeeira de Minas Gerais, favorece a maturação dos frutos e melhora consideravelmente a qualidade das uvas para vinificação.

Vestibular characterization in the menstrual cycle Caracterização vestibular no ciclo menstrual

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Cintia Ishii

2009-06-01

Full Text Available Hormonal disorders in the menstrual cycle can affect labyrinthine fluid homeostasis, causing balance and hearing dysfunctions. STUDY DESIGN: Clinical prospective. AIM: compare the results from vestibular tests in young women, in the premenstrual and postmenstrual periods. MATERIALS AND METHODS: twenty women were selected with ages ranging from 18 to 35 years, who were not using any kind of contraceptive method for at least six months, and without vestibular or hearing complaints. The test was carried out in each subject before and after the menstrual period, respecting the limit of ten days before or after menstruation. RESULTS: there was a statistically significant difference in the menstrual cycle phases only in the following vestibular tests: calibration, saccadic movements, PRPD and caloric-induced nystagmus. We also noticed that age; a regular menstrual cycle; hearing loss or dizziness cases in the family; and premenstrual symptoms such as tinnitus, headache, sleep disorders, anxiety, nausea and hyperacusis can interfere in the vestibular test. CONCLUSION: there are differences in the vestibular tests of healthy women when comparing their pre and postmenstrual periods.As alterações hormonais do ciclo menstrual podem comprometer a homeostase dos fluidos labirínticos, gerando alterações no equilíbrio e na audição. FORMA DO ESTUDO: Clínico prospectivo. OBJETIVO: Comparar os resultados dos testes do exame vestibular em mulheres jovens, nos períodos pré e pós-menstrual. MATERIAL E MÉTODO: Foram selecionadas vinte mulheres, entre dezoito e trinta e cinco anos, que não fizessem uso de qualquer tipo de anticoncepcional, com audição normal e sem queixas vestibulares. O exame vestibular foi realizado em cada participante no período pré e no período pós-menstrual, em ordem aleatória, e respeitando o limite de até dez dias antes do início da menstruação e até dez dias após o início da menstruação. RESULTADO: Foi observada

Fisiología reproductiva y control de los ciclos estrales en la gata doméstica

OpenAIRE

Giménez, F.; Stornelli, María Cecilia; Savignone, César A.; Tittarelli, Claudia Marcela; Sota, Rodolfo Luzbel de la; Stornelli, María Alejandra

2006-01-01

La gata doméstica es poliéstrica estacional, con ovulación inducida por el coito. Sin embargo, la ovulación espontánea puede ocurrir en algunas hembras. El celo ocurre con un intervalo de 14 a 19 días en aquellas gatas expuestas a un fotoperíodo largo (14 horas luz diarias). El ciclo estral felino se divide en cuatro períodos: proestro, estro, interestro y anestro. Cada etapa presenta ciertas particularidades que diferencian una de otra. Existen diferentes métodos para prevenir tanto la ocurr...

Biología y ciclo reproductivo de Apanteles gelechiidivoris (Hymenoptera: Braconidae, parasitoide de Tuta absoluta (Lepidoptera: Gelechiidae

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Bajonero Johanna

2008-12-01

Full Text Available

Apanteles gelechiidivoris es un parasitoide de larvas de Tuta absoluta (Lepidoptera: Gelechiidae, una plaga importante de cultivos como el tomate y la papa. El uso de este insecto para el control biológico no se ha implementado eficientemente debido a la falta de conocimiento de la biología, específicamente del ciclo de vida y el efecto de factores externos, como la temperatura, en su capacidad parasítica. Se evaluó el desarrollo y la capacidad reproductiva de A. gelechiidivoris en cuatro condiciones térmicas: 14, 20, 26 y 32 °C. En la evaluación del desarrollo se realizó una descripción del ciclo, se determinó la duración total de este, se estimaron los umbrales térmicos para cada estadio utilizando el modelo de Lactin y se hallaron los grados día. En la evaluación de la capacidad reproductiva se variaron las densidades del hospedero ofrecidas a una pareja recién emergida de la avispa de 5 hasta 160 y se contó el número de adultos emergidos con los cuales se evaluó longevidad y fecundidad. Adicionalmente se ajustó un modelo de respuesta funcional. La duración del ciclo de vida para las temperaturas evaluadas fue de 39 días en 14 °C, 34 en 20 °C, 19 en 26 °C y 17 en 32 °C. La longevidad fue de 7,5 (14 °C, 7 (20 °C, 5 (26 °C y 2,4 (32 °C días. La temperatura a la cual se pueden optimizar los parámetros reproductivos de esta avispa se encuentra entre 20 y 26 °C.

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.

El proceso de formación profesional del médico general integral en el ciclo de especialización

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José Enrique Vázquez Sarandeses

2015-01-01

Full Text Available Se exponen algunos aspectos relacionados con la formación profesional del médico general integral en el ciclo de especialización y se enfatiza en lo importante que resulta comprender e interpretar este proceso, para lograr un especialista con un alto nivel de preparación, y capaz de cumplir con su encargo social

A expressão e educação dramática : uma área transversal no pré-escolar e no 1º ciclo do ensino básico

OpenAIRE

Pereira, Marisa

2015-01-01

Relatório final apresentado para a obtenção do grau de mestre em Educação pré-escolar e 1º ciclo do ensino básico. No seguimento de uma síntese da prática pedagógica realizada nos contextos de jardim-de-infância, de escola de 1º ciclo e de creche, respetivamente, reflito sobre as dificuldades encontradas, sobre as potencialidades detetadas e aspetos a melhorar. Também fundamento algumas das minhas aprendizagens e pontos de vista. No segundo capítulo, pretendo mostrar, com os documentos ...

Combined cycle simulator with gas turbine and steam turbine with one vaporization stage; Simulador de ciclo combinado con turbina de gas y de vapor con un nivel de vaporizacion

Energy Technology Data Exchange (ETDEWEB)

Del Valle Cardenas, B.; Lugo Leyte, R. [Universidad Autonoma Metropolitana, Depto de Ingenieria de Procesos e Hidraulica, Mexico, D. F. (Mexico); Toledo Velazquez, Miguel; Tolentino Eslava, G. [Seccion de Estudios de Posgrado e Investigacion, Laboratorio de Ingenieria Termica e Hidraulica Aplicada, ESIME-IPN-COFFA, Mexico, D. F. (Mexico)

1998-12-31

This paper shows the thermal analysis of a combined cycle with gas and steam turbines with one vaporization stage. The analysis is performed through a computer program, which allows the simulation of cycles with different operational conditions, obtaining this way a series of results that permits to know the way these cycles behave in effecting temperature and pressure changes; besides of being an excellent tool in thermodynamics for the user. The simulators were performed in Borland C++ and Builder C++ Versions 4.5 and 2.0 respectively, creating in this way a friendly ambient for the user. This tool offers the opportunity to all its users the ability to simulate combined cycles in a fast and easy way in order to obtain a wider understanding of its thermodynamic behavior. [Espanol] En el presente trabajo se muestra el analisis termico de un ciclo combinado con turbinas de gas y de vapor con un nivel de vaporizacion. El analisis se realiza a traves de un programa de computo, el cual permite simular los ciclos con diferentes condiciones de operacion, obteniendo con esto una serie de resultados que permiten conocer la forma en que trabajan estos ciclos al realizar cambios en temperaturas y presiones; ademas de que es una excelente herramienta para el usuario en termodinamica. Los simuladores fueron realizados en Borland C++ y Builder C++ Versiones 4.5 y 2.0 respectivamente, creandose asi un ambiente amigable para el usuario. Esta herramienta brinda la oportunidad a todos los usuarios de poder simular ciclos combinados de una manera rapida y sencilla con el fin de obtener una comprension mas amplia de su comportamiento termodinamico.

Combined cycle simulator with gas turbine and steam turbine with one vaporization stage; Simulador de ciclo combinado con turbina de gas y de vapor con un nivel de vaporizacion

Energy Technology Data Exchange (ETDEWEB)

Del Valle Cardenas, B; Lugo Leyte, R [Universidad Autonoma Metropolitana, Depto de Ingenieria de Procesos e Hidraulica, Mexico, D. F. (Mexico); Toledo Velazquez, Miguel; Tolentino Eslava, G [Seccion de Estudios de Posgrado e Investigacion, Laboratorio de Ingenieria Termica e Hidraulica Aplicada, ESIME-IPN-COFFA, Mexico, D. F. (Mexico)

1999-12-31

This paper shows the thermal analysis of a combined cycle with gas and steam turbines with one vaporization stage. The analysis is performed through a computer program, which allows the simulation of cycles with different operational conditions, obtaining this way a series of results that permits to know the way these cycles behave in effecting temperature and pressure changes; besides of being an excellent tool in thermodynamics for the user. The simulators were performed in Borland C++ and Builder C++ Versions 4.5 and 2.0 respectively, creating in this way a friendly ambient for the user. This tool offers the opportunity to all its users the ability to simulate combined cycles in a fast and easy way in order to obtain a wider understanding of its thermodynamic behavior. [Espanol] En el presente trabajo se muestra el analisis termico de un ciclo combinado con turbinas de gas y de vapor con un nivel de vaporizacion. El analisis se realiza a traves de un programa de computo, el cual permite simular los ciclos con diferentes condiciones de operacion, obteniendo con esto una serie de resultados que permiten conocer la forma en que trabajan estos ciclos al realizar cambios en temperaturas y presiones; ademas de que es una excelente herramienta para el usuario en termodinamica. Los simuladores fueron realizados en Borland C++ y Builder C++ Versiones 4.5 y 2.0 respectivamente, creandose asi un ambiente amigable para el usuario. Esta herramienta brinda la oportunidad a todos los usuarios de poder simular ciclos combinados de una manera rapida y sencilla con el fin de obtener una comprension mas amplia de su comportamiento termodinamico.

Performance of supercritical Brayton cycle using CO2-based binary mixture at varying critical points for SFR applications

International Nuclear Information System (INIS)

Jeong, Woo Seok; Jeong, Yong Hoon

2013-01-01

Highlights: • Supercritical CO 2 -based gas mixture Brayton cycles were investigated for a SFR. • The critical point of CO 2 is the lowest cycle operating limit of the S-CO 2 cycles. • Mixing additives with CO 2 changes the CO 2 critical point. • CO 2 –Xe and CO 2 –Kr cycles achieve higher cycle efficiencies than the S-CO 2 cycles. • CO 2 –H 2 S and CO 2 –cyclohexane cycles perform better at higher heat sink temperatures. -- Abstract: The supercritical carbon dioxide Brayton cycle (S-CO 2 cycle) has attracted much attention as an alternative to the Rankine cycle for sodium-cooled fast reactors (SFRs). The higher cycle efficiency of the S-CO 2 cycle results from the considerably decreased compressor work because the compressor behaves as a pump in the proximity of the CO 2 vapor–liquid critical point. In order to fully utilize this feature, the main compressor inlet condition should be controlled to be close to the critical point of CO 2 . This indicates that the critical point of CO 2 is a constraint on the minimum cycle condition for S-CO 2 cycles. Modifying the CO 2 critical point by mixing additive gases could be considered as a method of enhancing the performance and broadening the applicability of the S-CO 2 cycle. Due to the drastic fluctuations of the thermo-physical properties of fluids near the critical point, an in-house cycle analysis code using the NIST REFPROP database was implemented. Several gases were selected as potential additives considering their thermal stability and chemical interaction with sodium in the temperature range of interest and the availability of the mixture property database: xenon, krypton, hydrogen sulfide, and cyclohexane. The performances of the optimized CO 2 -containing binary mixture cycles with simple recuperated and recompression layouts were compared with the reference S-CO 2 , CO 2 –Ar, CO 2 –N 2 , and CO 2 –O 2 cycles. For the decreased critical temperatures, the CO 2 –Xe and CO 2 �

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

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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.

Aporte a la caracterización etnográfica de los procesos de salud-enfermedad en las primeras etapas del ciclo vital, en comunidades Mbya-Guaraní de Misiones, República Argentina

OpenAIRE

Remorini, Carolina

2009-01-01

En este trabajo de tesis presentamos los resultados de una investigación etnográfica centrada en la descripción y análisis de las representaciones y prácticas acerca de las primeras etapas del ciclo vital en dos comunidades Mbya-Guarani de la provincia de Misiones, Argentina. El propósito central de este estudio fue la caracterización de las primeras etapas del ciclo de vida desde la perspectiva Mbya: en este contexto, se buscó identificar y analizar los factores y procesos sociocul...

CFD aided approach to design printed circuit heat exchangers for supercritical CO2 Brayton cycle application

International Nuclear Information System (INIS)

Kim, Seong Gu; Lee, Youho; Ahn, Yoonhan; Lee, Jeong Ik

2016-01-01

Highlights: • CFD analyses were performed to find performance of PCHE for supercritical CO 2 power cycle. • CFD results were obtained beyond the limits of existing correlations. • Designs of different PCHEs with different correlations were compared. • A new CFD-aided correlation covering a wider Reynolds number range was proposed. - Abstract: While most conventional PCHE designs for working fluid of supercritical CO 2 require an extension of valid Reynolds number limits of experimentally obtained correlations, Computational Fluid Dynamics (CFD) code ANSYS CFX was used to explore validity of existing correlations beyond their tested Reynolds number ranges. For heat transfer coefficient correlations, an appropriate piece-wising with Ishizuka’s and Hesselgreaves’s correlation is found to enable an extension of Reynolds numbers. For friction factors, no single existing correlation is found to capture different temperature and angular dependencies for a wide Reynolds number range. Based on the comparison of CFD results with the experimentally obtained correlations, a new CFD-aided correlation covering an extended range of Reynolds number 2000–58,000 for Nusselt number and friction factor is proposed to facilitate PCHE designs for the supercritical CO 2 Brayton cycle application.

Qualidade ambiental em solo com diferentes ciclos de cultivo do meloeiro irrigado Environmental quality in soil with different growing season cultivated w ith muskmelon irrigated

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Celsemy Eleutério Maia

2013-04-01

Full Text Available O solo é um importante componente do ecossistema terrestre, porque preserva reservas de nutrientes e dá suporte a processos biológicos. Para a preservação desse recurso, é necessário em primeiro lugar saber as condições e os processos que acontecem no solo, obtidos por meio de índices que determinam a sua qualidade. O objetivo deste trabalho foi avaliar a qualidade ambiental em Latossolo Vermelho cultivado com diferentes ciclos da cultura do melão. Foram coletadas amostras de solos de nove áreas com diferentes ciclos de cultivo e comparados com as da mata nativa. Concluiu-se que a qualidade ambiental diminuiu com os ciclos de cultivo, quando comparada com a área de referência de mata nativa.Soil is an important component of terrestrial ecosystems because it preserves nutrient reserves, supports many biological. To preserve this resource and its functions, it is necessary first of all to know the conditions and the processes occurring in it, for example, through the determination of soil quality. The aim of this study was to evaluate the environmental quality in Oxisol cultivated with different growing season of muskmelon. Were collected soil samples from nine areas with different growing season and compared with the native forest. It was concluded that environmental quality decreased with crop cycles when compared with the reference area of native forest.

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

Energy Technology Data Exchange (ETDEWEB)

Le Roux, W.G.; Bello-Ochende, T.; Meyer, J.P. [Department of Mechanical and Aeronautical Engineering, University of Pretoria, (South Africa)

2011-07-01

The energy of the sun can be transformed into mechanical power through the use of concentrated solar power systems. The use of the Brayton cycle with recuperator has significant advantages but also raises issues such as pressure loss and low net power output which are mainly due to irreversibilities of heat transfer and fluid friction. The aim of this study is to optimize the system to generate maximum net power output. Thermodynamic and dynamic trajectory optimizations were performed on a dish concentrator and an off-the-shelf micro-turbine and the effects of wind, solar irradiance and other environmental conditions and constraints on the power output were analyzed. Results showed that the maximum power output is increased when wind decreases and irradiance increases; solar irradiance was found to have a more significant impact than wind. This study highlighted the factors which impact the power generation of concentrated solar power systems so that designers can take them into account.

Testando a hipótese de ciclos eleitorais racionais nas eleições dos municípios paulistas

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Sergio Naruhiko Sakurai

2005-06-01

Full Text Available O objetivo deste artigo é, seguindo o raciocínio presente em Rogoff & Sibert (1988 e em Rogoff (1990, procurar evidências de ciclos orçamentários racionais nos municípios paulistas, entre os anos de 1989 a 2001, por meio de econometria de dados em painel e de modelos de variável dependente binária (probit e logit. Os resultados apresentam evidências de impulsos positivos em anos eleitorais na despesa orçamentária das unidades selecionadas, e embora o resultado obtido para 2000 seja diferente dos obtidos para 1992 e 1996, em ne-nhum dos casos são obtidas evidências de racionalidade dos eleitores, nos moldes previstos pela teoria dos ciclos eleitorais racionais.The purpose of this paper is, considering the theoretical approach proposed by Rogoff & Si-bert (1988 and Rogoff (1990, to attempt to find out evidences of rational budget cycles in São Paulo state municipalities, between 1989 and 2001, by using panel data and binary dependent variable (probit and logit econometric models. Evidences of positive expenditure impulses in electoral years were found for those unities and, although the results for 2000 are different from the results obtained for 1992 and 1996, there is no acceptance of the hypothesis of voters' rationality in the way predicted by the rational opportunistic cycle theory.

A inserção do discurso narrativo no ciclo informacional e seu impacto na aprendizagem organizacional

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Valério Brusamolin

2015-09-01

Full Text Available A presente pesquisa investiga o impacto que a inserção dos discursos narrativos no ciclo informacional proporciona na cultura de aprendizagem de uma organização. São identificados os usos de narrativas na gestão de projetos mediante pesquisa bibliográfica, que também apresenta os principais construtos da pesquisa. Verifica-se que a narrativa é uma prática de gestão do conhecimento utilizada com frequência no ambiente organizacional pelos gerentes, e também um tipo de discurso que pode ser analisado para a identificação de ideologias e estrutura de poder presentes na organização. Entretanto perdem-se valiosas oportunidades de aprendizado devido à ausência de registro das narrativas ou discursos narrativos, deixando de atender às necessidades de informação de histórias dos gerentes, lacuna que a proposta de pesquisa explorou mediante o experimento de um processo de gestão informacional para discursos, realizado no Instituto Brasileiro de Informação em Ciência e Tecnologia (IBICT. Conclui-se que as variações observadas nos aspectos de cultura de aprendizagem foram suficientes para validar, com o teste de postos com sinais de Wilcoxon, a hipótese da pesquisa, de que a inserção das narrativas no ciclo informacional de uma organização favorece o aprendizado organizacional.

EFEITOS DO CROMO HEXAVALENTE SOBRE O CRESCIMENTO DE RAÍZES E CICLO CELULAR NO MERISTEMA DA PONTA DA RAIZ DE Allium cepa

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Mary Helen Pestana da Costa

2016-09-01

Full Text Available O Cromo hexavalente [Cr (VI] é classificado pela Agência Internacional de Pesquisa sobre Câncer (IARC como cancerígeno para os seres humanos. A principal fonte de contaminação ambiental pelo cromo em ecossistemas aquáticos está relacionada com a aplicação industrial deste metal. No presente estudo, foram avaliados os efeitos citotóxicos e genotóxicos do Cr (VI no ciclo celular de células do meristema da raiz de Allium cepa. O teste foi usado para avaliar efeitos do cromo na germinação de sementes, alongamento das raízes, índice mitótico e indução de micronúcleos e anomalias do ciclo mitótico. Sementes de A. cepa foram germinadas em cinco diferentes condições: (1 controle negativo, água destilada; (2 grupo T1, tratado com dicromato de potássio a 6 mg.L-1; (3 grupo T2, tratado com dicromato de potássio a 12 mg.L-1; (4 grupo T3, tratado com dicromato de potássio a 24 mg.L-1; (5 controle positivo, tratado com NMU (N-nitroso-N-metilureia a 0,125 mg.L-1. As análises estatísticas efetuadas foram ANOVA e coeficiente de correlação de Pearson. Mesmo sem afetar o índice de germinação de sementes e o alongamento das raízes, os resultados demonstraram efeitos citotóxicos sobre o índice mitótico, bem como efeitos genotóxicos do cromo hexavalente. Palavras-chave: Cromo, Allium cepa, ciclo celular, citotoxicidade, genotoxicidade.

Evaluación ambiental basado en el análisisdel ciclo de vida (ACV) en la fase de construcción de una edificación en cataluña

OpenAIRE

Ortiz, O.; Pasqualino, J.; Castells, F.

2010-01-01

Mediante la aplicación de la metodología del Análisis del Ciclo de Vida es posible evaluar el impacto ambiental dela fase de construcción a partir de los materiales de construcción, transporte, energía, y la gestión de residuos. Por lo tanto, un caso de estudio de una construcción en Cataluña ha sido aplicado. Toda la masa de materiales usados durante el ciclo de vida de la fase de construcción fue determinado en 1.88E+03 kg/m2 del cual la estructura representa el 41%, cimientos 25% y cerrami...

Identified corrosion and erosion mechanisms in SCO2 Brayton Cycles.

Energy Technology Data Exchange (ETDEWEB)

Fleming, Darryn D.; Kruizenga, Alan Michael

2014-06-01

Supercritical Carbon Dioxide (S-CO2) is an efficient and flexible working fluid for power production. Research to interface S-CO2 systems with nuclear, thermal solar, and fossil energy sources is currently underway. To proceed, we must address concerns regarding compatibility of materials, at high temperature, and compatibility between significantly different heat transfer fluids. Dry, pure S-CO2 is thought to be relatively inert [1], while the addition of ppm levels of water and oxygen result in formation of a protective chromia layer and iron oxide [2]. Thin oxides are favorable as diffusion barriers, and for their minimal impact on heat transfer. While S-CO2 is typically understood to be the secondary fluid, many varieties of primary fluids exist for nuclear applications. Molten salts, for use in the Molten Salt Reactor concept, are given as an example to contrast the materials requirements of primary and secondary fluids. Thin chromia layers are soluble in molten salt systems (nitrate, chloride, and fluoride based salts) [3-8], making materials selection for heat exchangers a precarious balancing act between high temperature oxidation (S-CO2) and metal dissolution (salt side of heat exchanger). Because concerns have been raised regarding component lifetimes, S-CO2 work has begun to characterize starting materials and to establish a baseline by analysis of 1) as-received stainless steel piping, and 2) piping exposed to S-CO2 under typical operating conditions with Sandia National Laboratories Brayton systems. A second issue discovered by SNL involves substantial erosion in the turbine blade and inlet nozzle. It is believed that this is caused by small particulates that originate from different materials around the loop that are entrained by the S-CO2 to the nozzle, where they impact the inlet nozzle vanes, causing erosion. We believe that, in some way, this is linked to the purity of the S-CO2, the corrosion contaminants, and the metal particulates that

O ciclo dos imóveis e o crescimento econômico nos Estados Unidos 2002-2008 The housing cycle and U.S. economic growth: 2002-2008

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Rafael Fagundes Cagnin

2009-01-01

Full Text Available A partir dos anos 1980, as finanças americanas passaram por profundas transformações reforçando o papel dos mercados de capitais na gestão da riqueza e do crédito nos Estados Unidos. Nessa nova estrutura financeira, as decisões de gasto das famílias e das empresas sofrem influências importantes dos ciclos de preço de seus ativos, dando origem a ciclos econômicos finance-led. O artigo discute os dois últimos ciclos econômicos dos Estados Unidos, período em que a valorização dos imóveis residenciais substituiu o papel desempenhado pela valorização da riqueza no estímulo ao consumo e ao investimento agregados.Since the 1980's and from then on, the American finances had passed through deep changes that reinforced the role of the capital markets in the wealth and credit management in the U. S. In this new finance structure the household and corporation's decision expenses suffered important influence of theirs assets price cycles, resulting in economic cycles finance-led. The article assesses the last two economic cycles in the United States, in which period the value of the residential property replaced the role previously fulfilled by the shareholder value to stimulate the aggregates expenditure and investment.

El monitoreo pedagógico en el desempeño docente, ciclo II, UGEL 01- 2014

OpenAIRE

Soria Vásquez, Eugenia Magna

2015-01-01

La presente investigación titulada “El monitoreo pedagógico en el desempeño docente, ciclo II, UGEL 01 - 2014”, tuvo como objetivo determinar la relación de causa-efecto entre el monitoreo pedagógico y el desempeño docente y responder a la problemática de las instituciones educativas de la Red 1 0 de Villa María del Triunfo. La investigación obedece a un tipo aplicada, diseño pre experimental, longitudinal, de método hipotético deductivo; y se utilizó una ficha de observació...

Reacções de Ciclo-Adição na Síntese de Novos Heterociclos Funcionalizados

OpenAIRE

Lopes, Susana Margarida Martins

2012-01-01

Tese de doutoramento em Química, na especialidade de Síntese Orgânica O trabalho apresentado nesta dissertação teve como objectivo principal a síntese de novos compostos heterocíclicos funcionalizados via reacções de cicloadição. Este objectivo foi alcançado através do estudo de reacções de ciclo-adição 1,3- dipolar de alenoatos, na qual estes podem funcionar como percusores de dipolos e como dipolarófilos. Uma outra vertente estudada foi a reacção de hetero-Diels-Alder de n...

Simulador interativo de estabilidade de usinas termelÃtricas de ciclo combinado para projetos, pesquisa e treinamento

OpenAIRE

Gabriel Josà Alves dos Santos

2012-01-01

Neste trabalho foi desenvolvido o estudo e as aplicaÃÃes das condiÃÃes de estabilidade na operaÃÃo do sistema elÃtrico de potÃncia incorporado em um simulador interativo de usinas termelÃtricas de ciclo combinado, que permita melhorar os processos de treinamento e, consequentemente, o nÃvel de qualidade dos futuros operadores e mantenedores de usinas termelÃtricas, bem como manter atualizados os atuais operadores. Um pequeno conjunto de definiÃÃes e conceitos das Ãreas de âestabilidade, confi...

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...

Ciclo de vida organizacional pautado no modelo de Lester, Parnell e Carraher (2003 e na lógica fuzzy: classificação de empresas de um segmento industrial de Santa Catarina

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Ilse Maria Beuren

2012-06-01

Full Text Available Neste estudo, objetiva-se identificar os estágios do ciclo de vida organizacional pautados no modelo de Lester, Parnell e Carraher (2003 das empresas do segmento industrial de máquinas, aparelhos e materiais elétricos do estado de Santa Catarina. Pesquisa descritiva, com abordagem quantitativa, foi realizada por meio de levantamento com aplicação de questionário aos gestores das empresas. A população constituiu-se das 264 empresas desse segmento econômico, listadas na Secretaria da Fazenda do Estado de Santa Catarina, e a amostra não aleatória das 40 empresas que responderam a pesquisa. As variáveis de identificação dos estágios de ciclo de vida utilizadas no questionário foram extraídas de Lester, Parnell e Carraher (2003. Os dados da pesquisa foram submetidos à técnica estatística denominada lógica fuzzy. Os resultados da pesquisa demonstraram que 57,5% das empresas foram classificadas no estágio do nascimento, 15% do, 7,5% da Maturidade, 10% do rejuvenescimento e 10% do declínio. Concluiu-se que determinados estágios do ciclo de vida organizacional estão próximos uns dos outros e que não se pode perceber claramente uma progressão determinista nas fases do ciclo de vida, como uma sequência única, definitiva e irreversível, no sentido tradicional biológico.

POLÍTICA FISCAL EM PERSPECTIVA: O CICLO DE 16 ANOS (1999-2014

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Sérgio Wulff Gobetti

2015-12-01

Full Text Available RESUMO Este artigo oferece uma contribuição para o debate sobre as mudanças no regime fiscal brasileiro, caracterizando melhor o ciclo de contração e expansão da política fiscal entre 1999 e 2014. Em primeiro lugar, analisa estatísticas inéditas do resultado primário acima da linha que incorporam a esfera regional de governo. Isto permite compreender melhor a recente fase expansionista da política fiscal brasileira (2010-2014, identificando não só seus determinantes em termos de receitas e despesas, mas também o componente derivado dos governos estaduais e municipais. Adicionalmente, emprega diversos indicadores para caracterizar melhor esta fase expansionista em comparação com períodos anteriores. Por fim, analisa a sustentabilidade da trajetória da despesa pública em diferentes cenários.

Relación de tesis doctorales y trabajos de investigación de tercer ciclo y de máster (TIT. Curso 2009/2010

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Cuadernos de Arte

2011-01-01

Full Text Available Relación de tesis doctorales y trabajos de investigación de tercer ciclo y de máster (TIT, defendidos en el departamento de Historia del Arte y Música de la Universidad de Granada, durante el curso académico 2009/2010

CAMBIOS COMPOSICIONALES Y MICROBIOLÓGICOS ASOCIADOS A CICLOS SUCESIVOS DE DESHIDRATACIÓN OSMÓTICA DE TOMATE DE ÁRBOL COMPOSITIONAL AND MICROBIOLOGICAL CHANGES ASSOCIATED WITH SUCCESSIVE OSMODEHYDRATION CYCLES OF TREE TOMATO

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CRISTIAN CAMILO VILLA

2009-06-01

Full Text Available La Deshidratación Osmótica (DO es uno de los procesos más interesantes de aplicar en la industria alimentaria porque que permite la conservación de los productos, al disminuir su actividad de agua, usando la fuerza osmótica de una solución de azúcar, sal u otros materiales. La aplicación de esta técnica a frutas de origen tropical ricas en aromas exóticos como el tomate de árbol (Cyphomandra betacea (Cav Sendth, muestra tener gran potencial; sin embargo, se ha visto limitada por el problema económico y ambiental que representa el manejo de grandes volúmenes de la solución osmodeshidratante. En este artículo se establece la posibilidad de reutilizar la Solución Osmótica (SO, en el proceso de DO de cubos deformados de tomate de árbol durante 240 minutos, en una SO de 65°Brix y con una relación solución:fruta de 5:1. En cada ciclo de DO se renovaron los frutos y se reutilizó la SO sin reconcentrar, filtrando cada 4 ciclos. Se analizaron la pérdida de peso y humedad, la ganancia de °Brix, y la disminución de a w, de los frutos en cada ciclo de DO. Se realizaron recuentos microorganismos mesófilos aerobios, hongos y levaduras a la SO luego da cada ciclo de DO impar. Se encontró que la SO mantiene un carácter deshidratante similar al del primer ciclo de DO durante 7 ciclos sucesivos del proceso y es estable microbiológicamente hasta el noveno ciclo de DO.Osmotic Dehydration (OD is one of the most interesting processes to be applied in the food industry because it allows the preservation of products, by reducing their water activity, using the osmotic pressure of a concentrated solution of sugar, salt or other materials. The application of this technique to tropical fruits rich in exotic flavors such as tree tomato (Cyphomandra betacea (Cav Sendth, have shown great potential, but has been constrained by the economic and environmental problem that represents the management large volumes of the osmotic solution. This article

Análisis de ciclo de vida de una nueva solución arquitectónica que mejora el rendimiento térmico de la envolvente del edificio: Fachada Natural Aljibe

OpenAIRE

Carabaño, R.; Bedoya, C.; Ruiz, D.

2014-01-01

El objetivo de este trabajo, que supone la mejora del rendimiento térmico de la envolvente del edificio, es dar a conocer los impactos ambientales asociados a una nueva solución de fachada vegetada mediante la metodología de Análisis de Ciclo de Vida con límites del sistema de la cuna a la tumba. El análisis pretende también generar información relevante de ciclo de vida como material de partida para la redacción de una futura Declaración Ambiental de Producto. La etapa de fabricación de los ...

Os ciclos escolares: elementos de uma trajetória School cycles: elements of a trajectory

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Elba Siqueira de Sá Barretto

1999-11-01

Full Text Available Este artigo se propõe a evidenciar algumas características presentes em muitos dos ensaios de implantação dos ciclos escolares no país, bem como as justificativas para a sua adoção. Assim o faz por entender que o domínio das representações e da cultura, bem como o das fundamentações teóricas e das razões políticas que compõem as justificativas é um dos mais significativos na constituição das múltiplas determinações das reformas educacionais. São revisitados alguns textos antológicos da História da Educação Brasileira que situam a discussão em décadas passadas, bem como registradas iniciativas de adoção dos ciclos em diferentes períodos e em espaços diversos, recuperando-se inclusive dados de pesquisa sobre as propostas curriculares dos estados e de alguns municípios, vigentes entre 1985 e 1995.This article proposes to show some of the characteristics present in many of the attempts to implant school cycles in the country, as well as the justification for their adoption. It states that dominion of representation of culture, as well as of the theoretical fundamentals and political logic that comprise the justifications are the most significant points among the multiple determinants of educational reform. Some basic texts in the history of Brazilian education, which locate the discussion in the past decades, are reviewed along with recorded initiatives in adopting the cycles during different periods and in diverse locations. Data from research on curriculum proposals in some of the states and cities, in effect between 1985 and 1995 is reviewed and recovered.

CICLO DE VIDA: JUEGO EDUCATIVO MOVIL “EDUCAMOVIL”

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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.

Entropy, exergy, and cost analyses of solar driven cogeneration systems using supercritical CO_2 Brayton cycles and MEE-TVC desalination system

International Nuclear Information System (INIS)

Kouta, Amine; Al-Sulaiman, Fahad; Atif, Maimoon; Marshad, Saud Bin

2016-01-01

Highlights: • The entropy, exergy, and cost analyses for two solar cogeneration configurations are conducted. • The recompression cogeneration cycle achieves lower LCOE as compared to the regeneration cogeneration cycle. • The solar tower is the largest contributor to entropy generation in both configurations reaching almost 80%. • The specific entropy generation in the MEE-TVC decreases with decreasing the fraction. - Abstract: In this study, performance and cost analyses are conducted for a solar power tower integrated with supercritical CO_2 (sCO_2) Brayton cycles for power production and a multiple effect evaporation with a thermal vapor compression (MEE-TVC) desalination system for water production. The study is performed for two configurations based on two different supercritical cycles: the regeneration and recompression sCO_2 Brayton cycles. A two-tank molten salt storage is utilized to ensure a uniform operation throughout the day. From the entropy analysis, it was shown that the solar tower is the largest contributor to entropy generation in both configurations, reaching almost 80% from the total entropy generation, followed by the MEE-TVC desalination system, and the sCO_2 power cycle. The entropy generation in the two-tank thermal storage is negligible, around 0.3% from the total generation. In the MEE-TVC system the highest contributing component is the steam jet ejector, which is varying between 50% and 60% for different number of effects. The specific entropy generation in the MEE-TVC decreases as the fraction of the input heat to the desalination system decreases; while the specific entropy generation of the sCO_2 cycle remains constant. The cost analysis performed for different regions in Saudi Arabia and the findings reveal that the regions characterized by the highest average solar irradiation throughout the year have the lowest LCOE and LCOW values. The region achieving the lowest cost is Yanbu, followed by Khabt Al-Ghusn in the second

Incorporación de la asignatura de tercer ciclo "Técnicas y métodos de investigación jurídica comparada" al campus virtual

OpenAIRE

Palomino Lozano, Rafael

2005-01-01

Mediante la herramienta informática «Campus Virtual» se dinamiza una asignatura de tercer ciclo que tiene por objeto analizar la metodología de trabajo y el desarrollo de estrategias en la investigación jurídica.

Efeito genotóxico e antiproliferativo de Mikania cordifolia (L. F. Willd. (Asteraceae sobre o ciclo celular de Allium cepa L.

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M.G. Dias

2014-06-01

Full Text Available As plantas com potencial medicinal têm sido muito utilizadas para o tratamento de doenças no Brasil. O objetivo deste estudo foi avaliar o efeito genotóxico e antiproliferativo de infusões de Mikania cordifolia (L.F. Willd. sobre o ciclo celular de Allium cepa L. Foram coletadas duas populações no município de Santa Maria, Rio Grande do Sul, e, para cada uma, foram preparados dois tratamentos em duas concentrações: 4g/500mL e 16g/500mL, além de um controle positivo composto por 10% de glifosato em 90% água, um herbicida amplamente utilizado com conhecido potencial genotóxico, e de um controle negativo composto por água destilada. Após período de 24 horas, as radículas foram coletadas das infusões, fixadas em etanol-ácido acético (3:1 por 24 horas e estocadas em etanol 70%. Foram analisadas células em todas as fases do ciclo celular de A. cepa, totalizando 2500, para cada grupo de bulbos. Os índices mitóticos (IM foram calculados e submetidos à análise estatística pelo teste χ² a 5%. Os resultados mostraram que, em ambas as populações de M. cordifolia, houve redução do IM de todos os tratamentos em relação ao controle negativo. Em ambas as populações, obteve-se aumento nos valores dos índices mitóticos em função do aumento da concentração da infusão. Ocorreram aberrações cromossômicas em ambas as populações estudadas. Concluiu-se que as infusões de M. cordifolia, nas concentrações estudadas, possuem efeito antiproliferativo e mutagênico sobre o ciclo celular de A. cepa.

Multimodal evoked potentials and the ovarian cycle in young ovulating women Potenciais evocados nas diferentes fases do ciclo menstrual da mulher

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LUIZ ANTONIO DE LIMA RESENDE

2000-06-01

Full Text Available There is controversy over how hormonal conditions influence cerebral physiology. We studied pattern-shift visual evoked potentials (PS-VEP, brain stem auditory evoked potentials (BAEP and short-latency somatosensory evoked potentials (SSEV in 20 female volunteers at different phases of the menstrual cycle (estrogen phase, ovulatory day and progesterone phase. Statistical analysis showed decreased latencies for P100 (PS-VEP, N19 and P22 (SSEV waves in the progesterone phase compared with the estrogen phase. There was no significant difference between the estrogen and the ovulation day values. Comparing the three above stages, there were no significant differences in the brainstem auditory evoked potentials. The reduction of the latencies of the potentials generated in multisynaptic circuits provides the first consistent neurophysiological basis for a tentative comprehension of human pre-menstrual syndrome.Há controvérsias sobre como variações hormonais do ciclo menstrual da mulher influenciam a neurofisiologia cerebral. Estudamos potenciais evocados de curta latência, visuais, auditivos e sômato-sensoriais, em 20 mulheres voluntárias normais, nas diferentes fases do ciclo menstrual (fase estrogênica, fase ovulatória, fase progestacional. Comparação entre fase estrogênica e ovulatória mostrou resultados similares. Ondas I, III, V dos potenciais evocados auditivos não apresentaram diferenças estatisticamente significativas entre as três fases do ciclo. Análise estatística dos resultados mostrou diminuição significativa das latências das ondas P100, N19 e P22 obtidas na fase progestacional, comparadas com aquelas obtidas na fase estrogênica. Como estas ondas são geradas em circuitos multissinápticos, tal redução de latências, na fase progestacional, fornece a primeira base neurofisiológica consistente para tentativa de compreensão da síndrome pré-menstrual da mulher.

Avaliação da tolerabilidade e do controle de ciclo de dois contraceptivos orais de baixa dose: estudo comparativo aberto Assessment of the tolerability and cycle control of two low-dose oral contraceptives: an open-label study

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Edmund C. Baracat

1998-06-01

Full Text Available Realizou-se um estudo aberto comparativo em nove centros brasileiros para avaliar a tolerabilidade e o controle de ciclo obtido com o uso de dois contraceptivos orais de baixa dose contendo 20 mg etinilestradiol/75 mg gestodeno e 20 mg etinilestradiol/150 mg desogestrel, durante seis ciclos de tratamento. Foram selecionadas 167 mulheres saudáveis com vida sexual ativa (77 no grupo do gestodeno e 90 no grupo do desogestrel, das quais 138 completaram os seis ciclos de tratamento. Em um subgrupo de novas usuárias realizou-se também perfil lipídico e hemostático. Foram avaliados 867 ciclos no total. Ocorreu sangramento irregular em 4,6% dos ciclos com gestodeno e em 8,1% com desogestrel. A tolerabilidade a ambas preparações foi boa, mas houve significativamente mais náusea no grupo do desogestrel. O controle de ciclo foi bom com os dois contraceptivos, sendo que houve freqüência significativamente menor de sangramento irregular no grupo do gestodeno quando se leva em conta que todos os ciclos foram considerados. Não houve alterações clinicamente significativas no perfil hemostático. O perfil lipídico mostrou tendência a tornar-se mais favorável após seis ciclos de tratamento com as duas preparações. Não ocorreu alteração no peso médio das mulheres no grupo do gestodeno; no grupo do desogestrel houve aumento significativo no peso médio de aproximadamente 1 kg após seis meses de tratamento. A adesão ao tratamento foi boa com as duas preparações. Os resultados deste estudo mostram que preparações contendo baixa dose de gestodeno ou desogestrel associados a 20 mg de etinilestradiol são contraceptivos bem tolerados que permitem bom controle de ciclo, sem efeitos colaterais significantes.An open-label comparative study was conducted in nine centers in Brazil to evaluate the tolerability and cycle control of two low-dose oral contraceptives containing 20 mg ethynylestradiol/75 mg gestodene and 20 mg ethynylestradiol/150 mg

La expresión corporal en el curriculum: una propuesta integradora desde la formación del profesorado hasta el primer ciclo de la Enseñanza Primaria

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Deisy Margarita Pérez Pérez

2007-12-01

Full Text Available Esta propuesta tiene el propósito de solucionar el problema científico identificado: “La Expresión Corporal no está declarada explícitamente, como “elemento integrador” en el currículum de Educación Física vigente para el primer Ciclo de la enseñanza primaria en Cuba, de igual modo, tampoco se declara como contenido curricular en el plan de estudio para la formación del profesional de la Cultura Física y el Deporte”. La metodología utilizada para solucionar nuestro problema científico se basa en la revisión de documentos, aplicación de un cuestionario a los profesores de Educación Física del I Ciclo y, partiendo de estos resultados, una entrevista grupal a parte de esta muestra. El resultado principal en el orden teórico- conceptual será la propuesta de una asignatura para la formación del profesional y otra propuesta didáctica de Expresión Corporal para elaborar Unidades Didácticas de Expresión Corporal desde la Educación Física del I Ciclo. A su vez, también se introducen otros conceptos didácticos y técnico-metodológicos, vinculados al proceso de aprendizaje corporal en la edad escolar temprana (I Ciclo. Desde el punto de vista didáctico se dan indicaciones para el aprendizaje de la Expresión Corporal con un carácter globalizado en el grado, es decir, que la Expresión Corporal se vinculará con otras materias adyacentes tales como la Educación Musical, Desarrollo Sensorial, Desarrollo del Lenguaje, etc. En particular propondrá otras formas de expresión con el cuerpo, contenidos no declarados en el currículo vigente de Educación Física.

Histología del ciclo reproductor de hembras del pejelagarto Atractosteus tropicus (Lepisosteiformes: Lepisosteidae enTabasco, México

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Otilio Méndez-Marin

2012-12-01

Full Text Available En el sureste de México A. tropicus es una especie de gran importancia ecológica, económica, cultural y para acuicultura, sin embargo, sus poblaciones silvestres han disminuido a causa de diversas actividades antropogénicas, por lo que se caracterizó el ciclo reproductor de A. tropicus, a partir de los cambios en los elementos germinales y somáticos durante la ovogénesis y la estructura de toda la gónada, información valiosa para el mejor manejo y aprovechamiento de la especie. Mensualmente se capturaron con redes de arrastres, seis hembras sexualmente maduras (N=72, durante un ciclo anual (octubre 2003-septiembre 2004, en poblaciones silvestres de la laguna de Pomposu del municipio de Jalpa de Méndez; Tabasco, México. Las hembras fueron sacrificadas por decapitación y los ovarios se procesaron por métodos histológicos convencionales, se determinó el diámetro entre 10-20 ovocitos en los diferentes estadios de desarrollo al azar. Se determinó mensualmente el índice gonadosomático (IGS, volumen gonadal (gV y el diámetro del folículo (fD. Además, se identificaron ocho estadios de desarrollo de la ovogénesis: I: cromatina nucléolo, II: perinucléolo temprano, III: perinucléolo avanzado, IV: alvéolos corticales, V: vitelogénesis temprana, VI: vitelogénesis media, VII: vitelogénesis avanzada, VIII: maduración final. El ciclo reproductor la constituye cuatro clases: I.-Proliferativa, II.-Maduración inicial, III.-Maduración tardía, IV.-Regresión-proliferación. El análisis de la información obtenida de los valores encontrados del IGS, gV, fD, estadios de la ovogénesis y clases reproductivas, indican que en diciembre se reinicia el crecimiento de los folículos (previtelogenesis, de mar-zo-julio se presenta la captación del vitelo (vitelogenesis y en agosto-noviembre se presenta la máxima actividad reproductora, al contrastar este patrón con los factores ambientales (temperatura, precipitación se sugiere que estos

Modelo LUDO: el gobierno abierto desde la perspectiva del ciclo de las políticas públicas

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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

Advances in defining a closed brayton conversion system for future ARIANE 5 space nuclear power applications

International Nuclear Information System (INIS)

Tilliette, Z.P.

1986-06-01

The present European ARIANE space program will expand into the large ARIANE 5 launch vehicle from 1995. It is assumed that important associated missions would require the generation of 200 kWe or more in space during several years at the very beginning of the next century. It is the reason why, in 1983, the French C.N.E.S. (Centre National d'Etudes Spatiales) and C.E.A. (Commissariat a l'Energie Atomique) have initiated preliminary studies of a space nuclear power system. The currently selected conversion system is a closed Brayton cycle. Reasons for this choice are given: high efficiency of a dynamic system; monophasic, inert working fluid; extensive turbomachinery experience, etc... A key aspect of the project is the adaptation to the heat rejection conditions, namely to the radiator geometry which depends upon the dimensions of the ARIANE 5 spacecraft. In addition to usual concepts already studied for space applications, another cycle arrangement is being investigated which could offer satisfactory compromises among many considerations, increase the efficiency of the system and make it more attractive as far as the specific mass (kg/kWe), the specific radiator area (m 2 /kWe) and various technological aspects are concerned. Comparative details are presented

Performance analysis for an irreversible variable temperature heat reservoir closed intercooled regenerated Brayton cycle

International Nuclear Information System (INIS)

Wang Wenhua; Chen Lingen; Sun Fengrui; Wu Chih

2003-01-01

In this paper, the theory of finite time thermodynamics is used in the performance analysis of an irreversible closed intercooled regenerated Brayton cycle coupled to variable temperature heat reservoirs. The analytical formulae for dimensionless power and efficiency, as functions of the total pressure ratio, the intercooling pressure ratio, the component (regenerator, intercooler, hot and cold side heat exchangers) effectivenesses, the compressor and turbine efficiencies and the thermal capacity rates of the working fluid and the heat reservoirs, the pressure recovery coefficients, the heat reservoir inlet temperature ratio, and the cooling fluid in the intercooler and the cold side heat reservoir inlet temperature ratio, are derived. The intercooling pressure ratio is optimized for optimal power and optimal efficiency, respectively. The effects of component (regenerator, intercooler and hot and cold side heat exchangers) effectivenesses, the compressor and turbine efficiencies, the pressure recovery coefficients, the heat reservoir inlet temperature ratio and the cooling fluid in the intercooler and the cold side heat reservoir inlet temperature ratio on optimal power and its corresponding intercooling pressure ratio, as well as optimal efficiency and its corresponding intercooling pressure ratio are analyzed by detailed numerical examples. When the heat transfers between the working fluid and the heat reservoirs are executed ideally, the pressure drop losses are small enough to be neglected and the thermal capacity rates of the heat reservoirs are infinite, the results of this paper replicate those obtained in recent literature

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...

Perfil hormonal de Progesterona durante o ciclo Estral em novilhas Nelore confinadas com Diferentes Ondas de Crescimento Folicular Plasma Progesterone Level during the Estrous Cycle in Nelore Heifers Confined with Two, Three and Four Waves of Follicular Growth

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Luciene Lomas Santiago

2001-12-01

Full Text Available Efetuaram-se coletas diárias de sangue, de 16 novilhas Nelore confinadas, para análise de progesterona plasmática pelo método de radioimunoensaio (RIA. Os dias analisados para progesterona foram o dia zero (estro e a cada três dias até o dia -1 e o dia zero. Os animais foram divididos em dois grupos: 1 com ciclo estral de 21 dias aproximadamente (novilhas que apresentaram duas e três ondas de crescimento folicular e 2 com ciclo estral superior a 25 dias (novilhas com quatro ondas de crescimento folicular. As concentrações médias de progesterona plasmática dos animais durante o ciclo estral diferiram entre os dois grupos, sendo superiores (4,27 ng/mL para os ciclos de maior duração. A concentração média de progesterona no ciclo de aproximadamente 21 dias foi de 2,54 ng/mL. Os resultados sugerem que as novilhas que apresentam maior duração do ciclo estral necessitam de tempo adicional para que seus folículos cheguem ao estádio pré-ovulatório, havendo, dessa maneira, prolongamento e aumento da secreção de progesterona.Blood were collected daily from 16 Nelore heifers confined, for radioimmunoassay (RIA.analyses of progesterone The plasma progesterone assay were at day zero (estrus and at each three days until the -1 and the day zero.again The animals were divided in two groups: 1 with regular estrous cycle of 21 days (heifers with two and three follicular growth waves and 2 with prolonged estrous cycle, greater than 25 days (heifers with four follicular growth waves. The mean plasma progesterone level from the animals during the estrous cycle differed between the two groups, being greater (4,27 ng/mL for the extended cycles.(above 25 days; 4,27 ng/mL than for the regular estrous cycle (21 days; 2,54 ng/mL. Results suggest that those heifers which showed an extended estrous cycles, needs an additional time for the follicles to each the pre-ovulatory stadium, resulting in prolonged and increased progesterone secretion.

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

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Jorge A. Barquero B.

2004-01-01

Full Text Available El propósito de este estudio fue el de explorar las condiciones de 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, mediante la utilización de 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.

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...

Enseñanza y aprendizaje de la en el 2º ciclo de Educación Infantil

OpenAIRE

Redondo Villahoz, María

2017-01-01

Este trabajo Fin de Grado aborda la importancia de la lectura y la escritura en el segundo ciclo de la Educación Infantil, así como, la revisión de diferentes teorías acerca de la lectura y la escritura, y los modelos de enseñanza y aprendizaje de la lectoescritura en esta etapa. Del mismo modo, consta de una propuesta didáctica basada en una serie de actividades para el trabajo de la lectoescritura. Para finalizar, se aportan unas conclusiones acerca de la teoría expuesta. Grado en Edu...

Recursos para la estimulación del lenguaje en el segundo ciclo de educación infantil

OpenAIRE

Escudero Zarzuelo, Marta

2017-01-01

Con este Trabajo Fin de Grado me gustaría destacar la importancia de la estimulación del lenguaje oral en Educación Infantil, en especial, en el Segundo Ciclo, puesto que he realizado el periodo del Prácticum II con alumnos de 4 años. El valor educativo de la comunicación oral queda recogido en los distintos apartados de la fundamentación teórica, así como en la justificación de este trabajo. Asimismo, presentaré una serie de actividades para favorecer tanto la comunicación oral como la co...

Análisis exergético de una planta de cogeneración operando bajo ciclo combinado

OpenAIRE

Hernán Darío Patiño Duque; Bryan Dario Rosero Coral

2017-01-01

En la actualidad, hay diversas formas para generar energía eléctrica, una de ellas consiste en aprovechar la cantidad de energía liberada al quemar un combustible y efectuar una serie de procesos de conversión de energía mediante un ciclo termodinámico. Para hacer estos procesos más eficientes, existen herramientas que permiten analizar en qué equipos de la planta se está desaprovechando energía, una de estas técnicas es el análisis exergético, que consiste en la aplicación simultanea de la p...

Inventário de ciclo de vida da manufatura de seringas odontológicas Life cycle inventory of dental syringes

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Biagio F. Giannetti

2008-01-01

Full Text Available Uma das formas mais integradas, completas e eficazes para a gestão ambiental de atividades produtivas é baseada no ciclo de vida do produto, sendo a Avaliação do Ciclo de Vida sua principal ferramenta. O produto avaliado é a seringa odontológica tipo Carpule. O objetivo é a realização do Inventário de Ciclo de Vida (ICV simplificado da fabricação de seringas odontológicas tipo Carpule, visando quantificar o uso de energia elétrica e a emissão de resíduos sólidos desde a mineração até o descarte do produto. A estrutura metodológica está baseada nas normas da série NBR ISO 14.040 e ISO 14.040. As fronteiras do estudo incluem as etapas de mineração, beneficiamento e manufatura; a produção do polietileno que compõe o tubete e a embalagem da agulha; a produção do aço, utilizado na fabricação da agulha, e o uso do conjunto pelos dentistas. A unidade funcional utilizada é 10(6 (um milhão de anestesias aplicadas. Na avaliação de melhorias, as soluções propostas permitem reduzir o consumo de energia elétrica em aproximadamente 20% na etapa de manufatura. A quantidade de resíduos sólidos pode ser reduzida de 40% na etapa de manufatura, o que corresponde a aproximadamente 6,50% do total de resíduos sólidos no ciclo de vida da seringa odontológica.Among the methods proposed to environmental management of productive activities, Life Cycle Assessment is one of the most integrated, complete and efficacious. The product assessed is the dental carpule syringe. The aim of this work is to to perform a Streamlined Life Cycle Inventory (LCI to quantify the electric energy consumption and the solid waste release from dental carpule syringes manufacture. The methodological structure is based on NBR ISO 14.040 and ISO 14.040 series. The LCI covers the syringe life cycle from mining to disposal. The limits of the system include the stages of copper and zinc mining and ore beneficiation; the production of polyethylene used for

Un modulador del ciclo visual como potencial tratamiento farmacológico de la DMAE seca y el Stargardt

OpenAIRE

Martín Nieto, José

2010-01-01

Un medicamento oral para la forma seca de la degeneración macular asociada a la edad (DMAE) ha entrado en la fase II de ensayos clínicos tras mostrar resultados positivos en cuanto a seguridad y eficacia en estudios previos preclínicos realizados en animales y en la fase I de ensayos en personas. Desarrollado por la compañía Acucela, el ACU-4429 es un compuesto no retinoide que actúa inhibiendo la regeneración de los pigmentos visuales y, con ello, ralentizando el ciclo visual y reduciendo la...

Nuevos Patrones de Reconocimiento Visual en el Ciclo Cardiaco New Patterns of Visual Recognize in the Cardiac Cycle

OpenAIRE

Estela Audelo; Fernando Beristain; Carlos Vázquez

2007-01-01

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 cic...

Relación del Ciclo de Vida Organizacional con la Planificación: Un Estudio con Empresas Prestadoras de Servicios Contables del Estado de Santa Catarina

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Dinorá Baldo de Faveri

2014-01-01

Full Text Available El estudio objetiva identificar la relación de las diferentes etapas del ciclo de vida organizacional con el proceso de planificación de las empresas prestadoras de servicios contables del Estado de Santa Catarina. Pesquisa descriptiva con abordaje cuantitativo fue realizada por medio de pesquisa de estudio en una muestra por accesibilidad en 116 empresas. Para tanto, se utilizó del modelo de Miller y Friesen (1984 para identificar las etapas de ciclo de vida y del instrumento de Frezatti, Relvas, Nascimento, Junqueira y Souza (2010 para mensurar el nivel de utilización de los artefactos de la planificación. La planificación fue analizada en sus tres modalidades: Planificación Estratégica, Presupuesto y Control Presupuestario. Para el análisis de los datos, se hizo uso del análisis discriminante y de correlaciones. Los resultados del estudio mostraron que las empresas prestadoras de servicios contables están clasificadas en distintas etapas de ciclo de vida organizacional, con predominancia en el nacimiento y en el rejuvenecimiento. Solamente la mitad de las empresas analizadas se hace uso del presupuesto, incluso siendo dirigidas por personas del área y que conocen la importancia de este instrumento. Se observó asimismo que existe una correlación negativa entre las etapas de nacimiento y declive y la utilización de los artefactos de planificación y una correlación positiva entre las etapas de crecimiento, madurez y rejuvenecimiento, convergiendo con los resultados de Miller y Friesen (1984.

A Conceptual Study of Using an Isothermal Compressor on a Supercritical CO{sub 2} Brayton Cycle for SMART Application

Energy Technology Data Exchange (ETDEWEB)

Heo, Jin Young; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of); Ahn, Yoonhan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

To maximize the benefits of modularization, the supercritical CO{sub 2} (S-CO{sub 2}) power cycle can replace the conventional steam Rankine cycle to increase the cycle efficiency and reduce its system size. Previous works have been conducted to evaluate potential advantages of applying the S-CO{sub 2} cycle to SMRs, specifically to SMART (System-integrated Modular Advanced Reactor) which is an integral SMR developed by KAERI (Korea Atomic Energy Institute). One of the optimized S-CO{sub 2} cycle layouts is the recompressing Brayton cycle. This paper attempts to improve the cycle layout by replacing the conventional compressor with an isothermal compressor, of which its potential in the S-CO{sub 2} power cycle is conceptually being evaluated. The SMR applications, for which SMART reactor has been represented, can take advantage of the currently developing S-CO{sub 2} cycle greatly by the reduction of size. By introducing the isothermal compressor, the cycle layout considered in has been further improved by increasing the cycle net efficiency by around 0.5%.

Custo de ciclo econômico no Brasil em um modelo com restrição a crédito

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Bárbara Vasconcelos Boa Vista da Cunha

2004-06-01

Full Text Available O estudo do impacto de ciclo econômico no bem-estar dos indivíduos de uma economia é um assunto de grande importância teórica. Ao considerarmos a economia brasileira, em que grande maioria dos indivíduos não dispõe de mecanismos de crédito, ele torna-se ainda mais relevante. Se os agentes não são capazes de suavizar consumo segundo a hipótese da renda permanente de Friedman, é de se esperar que estes sofram impactos ainda maiores diante de flutuações na renda. Utilizamos o modelo proposto por Imrohoroglu (1989 para os dados da economia brasileira a fim de mensurar a perda de bem-estar causada por um ciclo econômico. A partir de resultados que mostram o significativo custo dos ciclos econômicos, propomos a introdução do governo no modelo. Agindo no sentido de completar mercados, o governo se mostrou eficiente. Apesar de simples, nosso experimento mostrou a importância de investigarmos a ação governamental como opção para a elevação do bem-estar em economias restritas ao crédito ao longo de flutuações econômicas.This article studies the welfare cost of business cycles fluctuation in Brazil. We use a model, due to Imrohoroglu (1989, in which agents are ex-post heterogeneous with respect to employment and cannot smooth perfectly consumption as they are credit restricted. This is highly relevant as the evidence is that at least 75% of Brazilian population has no access to credit markets so that their consumption path tend to be highly sensitive to economic variability. Our simulations show that in fact welfare losses due to output fluctuations are significant in Brazil and much higher than the losses found for the US economy. We introduce in the model public policies that tend to complete markets and act as an (imperfect insurance. With a very simple tax and transfer mechanism we show that the government can increase considerably welfare.

ESTRATEGIAS LÚDICAS PARA LA INICIACIÓN DE LA LECTO ESCRITURA EN LOS ALUMNOS DEL III CICLO DE EDUCACIÓN PRIMARIA DE LA INSTITUCIÓN EDUCATIVA N° 32418 VISCAS DISTRITO DE SINGA-HUAMALIES-HUÁNUCO, 2013

OpenAIRE

Santillan Jesus, Ines Ena

2017-01-01

El presente trabajo de investigación titulado: ESTRATEGIAS LÚDICAS PARA LA INICIACIÓN DE LA LECTO ESCRITURA EN LOS ALUMNOS DEL III CICLO DE EDUCACIÓN PRIMARIA DE LA INSTITUCIÓN EDUCATIVA N° 32418 VISCAS DISTRITO DE SINGA-HUAMALIES-HUANUCO 2013, tuvo como objetivo principal; Demostrar las influencias de las estrategias lúdicas en la iniciación de la lectoescritura en los niños y niñas del III ciclo de educación primaria de la Institución Educativa N° 32418 Viscas del distrito de Singa, provinc...

Ciclo térmico para la obtención de una ferrita de Ni-Zn: (II Influencia de la etapa de enfriamiento

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Barba, A.

2008-04-01

Full Text Available Ceramic bodies formed from (Cu0.12Ni0.23Zn0.65Fe2O4 ferrite powders stand out as electromagnetic radiation absorbers among Cu-doped Ni-Zn ferrites, preventing interference between electronic devices. In a preliminary study, a methodology was established for designing the sintering stage of a thermal cycle, which allows the foregoing ceramic bodies to be obtained with the appropriate microstructure (high relative density and little grain growth to provide them with good electromagnetic properties. The present study examines the cooling stage (i.e. the stage following the sintering stage of that thermal cycle and the influence of the cooling rate on fired relative density, average grain size, and grain size distribution, varying the sintering time of the thermal cycle used.

Las piezas cerámicas obtenidas a partir de polvos de ferritas de composición (Cu0.12Ni0.23Zn0.65Fe2O4 destacan como absorbentes de radiación electromagnética entre las ferritas de Ni-Zn dopadas con Cu, impidiendo interferencias entre dispositivos electrónicos. En un trabajo previo se estableció la metodología para diseñar la etapa de sinterización de un ciclo térmico que permite obtener las piezas cerámicas mencionadas con una microestructura adecuada (elevada densidad relativa y escaso crecimiento de grano para que presenten unas buenas propiedades electromagnéticas. En este trabajo se ha estudiado la etapa de enfriamiento del mismo ciclo térmico (etapa siguiente a la de sinterización, determinando la influencia que ejerce la velocidad de enfriamiento sobre la densidad relativa en cocido, el tamaño medio de grano y la distribución de tamaños de grano, variando el tiempo de sinterización del ciclo térmico empleado.

Herramientas computacionales de identificación y suavizado de ciclos de movimiento de autobuses en conducción urbana

OpenAIRE

Ruiz Porro, Jorge

2017-01-01

Este Trabajo Fin de Máster se encuentra enmarcado dentro de otro de mayor envergadura denominado proyecto CÍCLOPE que está siendo desarrollado por profesionales del Instituto de Investigación del Automóvil (INSIA) y profesores de la ETSII como los tutores de este trabajo. El proyecto CÍCLOPE tiene como objetivo fundamental el desarrollo de un sistema que permita generar patrones de conducción a partir de ciclos optimizados con los que se puedan reducir los niveles de emisiones contaminantes y...

Comportamento visual do ciclo PDCA : uma proposta de modelo de visualização do perfil e estratégia do gestor de pequena e média empresa de móveis

OpenAIRE

Staszczak, Luiz Simão

2012-01-01

A presente pesquisa apresenta um modelo teórico para visualização espacial do ciclo PDCA para qualquer organização, e é advinda da implantação deste método no nível empresarial e discute mudança no comportamento e na análise do ciclo PDCA, partindo da visão planificada para a visualização tridimensional. Aqui se utiliza a representação paramétrica, da identificação do estilo cognitivo e da estratégia do gestor para construir modelos conceituais a serem comparados no mundo real a p...

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

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Webster, Jacqueline

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, a = 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

Franco Modigliani e la teoria del ciclo vitale del consumo

Directory of Open Access Journals (Sweden)

Angus Deaton

2005-06-01

Full Text Available Nei primi anni ’50, Franco Modigliani e il suo studente Richard Brumberg elaborarono una teoria della spesa fondata sull’idea che gli individui effettuano scelte intelligenti su quanto desiderano spendere a ogni età, con il solo limite delle risorse disponibili nel corso della loro vita. Attraverso l’accumulo e il decumulo delle attività, chi lavora può provvedere alla propriapensione e, più in generale, può adattare i propri modelli di consumo alle esigenze che sipresentano alle diverse età, indipendentemente dal reddito disponibile in ogni momento della suavita. Questa semplice teoria conduce a previsioni rilevanti e non scontate per l’economia nel suo complesso, ad esempio che il risparmio nazionale dipende dal tasso di crescita del reddito nazionale e non dal suo livello, e che esiste una semplice relazione tra il livello della ricchezza nelsistema economico e la lunghezza del periodo trascorso in pensione. Tali previsioni, non verificabili negli anni ’50, hanno trovato considerevole sostegno empirico in successivi lavori di Modigliani e di altri ricercatori. Sebbene nel corso degli anni la teoria del consumo abbia subitonumerosi attacchi, i più recenti dei quali mossi da una coalizione di psicologi ed economisti,l’ipotesi del ciclo vitale rimane una parte essenziale del pensiero degli economisti.

Manuais escolares de matemática para o Ciclo Preparatório do Ensino Técnico

OpenAIRE

Sousa, Isabel Moz de

2012-01-01

Dissertação para obtenção do Grau de Mestre em Ensino de Matemática O objetivo desta tese de mestrado consiste em contribuir para uma análise do desenvolvimento do ensino da matemática nos cursos técnicos (industriais e comerciais) durante o período compreendido entre a publicação da Lei de Bases do Ensino Técnico (em 1947) e a criação do Ciclo Preparatório do Ensino Secundário (1968). A análise irá incidir sobre o estudo de um capítulo (frações) dos manuais escolares destinados aos alu...

La percepción de sentido de la vida en el ciclo vital: una perspectiva temporal

OpenAIRE

Thiago Antonio Avellar de Aquino; Valdiney Veloso Gouveia; Eliseudo Salvino Gomes; Lorena Bandeira da Silva

2017-01-01

El objetivo de este estudio ha sido conocer en qué medida la percepción ontológica del tiempo y la sensación de presencia y búsqueda de sentido cambian según el ciclo de la vida. Participaron 766 voluntarios, la mayoría mujeres (59%), agrupados en los siguientes rangos: Juventud (N = 350; 18 a 24 años, M = 20.8, DT = 1.84), Joven Adulto (N = 195; 25 a 34 años, M = 28.3, DT = 2.66), Adulto (N = 110; 35 a 59 años, M = 45.8, DT = 7.16) y Tercera Edad (N = 111; 60 a 87 años, M = 65.6, DT = 4.81)....

Transferências voluntárias e ciclo político-orçamentário no federalismo fiscal brasileiro

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Ivan F. S. Ferreira

2007-09-01

Full Text Available RESUMO Este artigo apresenta um estudo econométrico sugerindo que as transferências inter-governamentais no Brasil são significantemente influenciadas por motivações político-partidárias. Diante desse fato estilizado, desenvolve-se uma extensão do modelo de Rogoff (1990 para analisar o efeito dessas transferências politicamente motivadas sobre os equilíbrios eleitoral e fiscal subnacionais. Mostra-se que as transferências politicamente motivadas podem anular o principal aspecto positivo do ciclo político-orçamentário. De fato, essas transferências podem, por um lado, eliminar o ciclo políticoorçamentário, resolvendo o problema de risco moral, mas, por outro lado, elas podem colocar no poder um titular incompetente, gerando um problema de seleção adversa.This article presents an econometric study suggesting that intergovernmental transfers to Brazilian municipalities are strongly partisan motivated. In light of that stylized fact, it develops an extension to Rogoff (1990's model to analyze the effect of partisan motivated transfers into sub-national electoral and fiscal equilibria. The main finding is that important partisan transfers may undo the positive selection aspect of political budget cycles. Indeed, partisan transfers may, on one hand, eliminate the political budget cycle, solving a moral hazard problem, but, on the other hand, they may retain an incompetent incumbent in office, bringing about an adverse selection problem.

BUENAS PRÁCTICAS, UNA SOLUCIÓN PARA UN MEJOR DESARROLLO DE SOFTWARE

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Liliana del Carmen Ramírez-M

2014-12-01

Full Text Available Este articulo tiene como objetivo principal dar a conocer una serie de buenas prácticas planteadas para un mejor desarrollo de software, basadas en las metodologías agiles más representativas se han propuesto unos valores, unas características, unos roles, unas prácticas y un ciclo de vida para el desarrollo de un proyecto de software, con lo cual se busca abarcar todo el proceso desde que surge una necesidad por parte de un cliente, hasta el momento en se tiene la seguridad de que el cliente está totalmente satisfecho con el producto. Estas prácticas planteadas buscan comprometer al equipo de trabajo e integrarlo al proyecto de una manera beneficiosa para las personas participantes, ya que pueden estar desde el inicio hasta la fase final del proyecto cumpliendo un rol u otro específicamente, logrando con esto reducción de tiempo, costos y otros.

Relação entre Ciclo de Vida do Produto Turístico e Estratégias de Cooperação na Faixa Litorânea Urbana do Município de Natal

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Anette Santiago Pereira

2010-07-01

Full Text Available Resumo Com a concretização das ações estruturantes para o turismo em Natal, se expandem as ações baseadas na cooperação e a formalização de instâncias de governança. Este estudo teve como objetivo analisar a relação entre o ciclo de vida do produto turístico ‘Litoral Urbano de Natal’ e as estratégias de cooperação em uma perspectiva histórica. A teoria está constituída de uma revisão sobre ciclo de vida, ecologia populacional, sistema de turismo, estratégias de cooperação e novas formas de gestão. Os resultados apontaram que o gráfico do ciclo de vida do produto ‘Litoral Urbano de Natal’, encontra-se migrando de uma fase de crescimento para uma fase de maturidade. As estratégias de cooperação identificadas foram o consórcio, estratégia coletiva e aglomerados, que se relacionam ao ciclo de vida do Produto Turístico através do alcance da eficiência coletiva. Palavras-chave: turismo; ciclo de vida do produto; cooperação. Abstract With the completion of tourism structuring actions, it was spread actions based on cooperation and formalization of governance institutions. This study aimed to examine the relationship between the tourism product life cycle 'Coastal Range of Natal” and the cooperation strategies in a historical perspective. The theoretical support is a revision about Resort Life Cycle, Theory of Population Ecology, System of Tourism, Co-operation Strategies and Management New Forms. Results showed that the life cycle graph of product 'Coastal Range of Natal’ is moving from one stage of growth to a stage of maturity. The co-operation strategies identified were consortium, collective strategy and clusters, which are related to the life cycle of the tourism product ‘Coastal Range of Natal’ when the efficiency of collective actions is achieved. Keywords: tourism; product life cycle; co-operation.

Das séries aos ciclos de estudos: o desafio da (descontinuidade De los grados a los ciclos de estudios: el desafío de la (descontinuidad From grades to study cycles: the challenge of the (discontinuity

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Doralice Aparecida Paranzini Gorni

2009-12-01

Full Text Available A partir da década de 1980 iniciou-se a reorganização das tradicionais séries do ensino fundamental brasileiro em ciclos, sustentada no princípio da ampliação do tempo de aprendizagem do aluno e na idéia de continuidade. O trabalho objetivou investigar as práticas avaliativas em uma escola pública organizada em ciclos, bem como, as condições necessárias para a concretização da avaliação formativa no seu cotidiano. Consistiu em uma pesquisa qualitativa que propôs a adequação da avaliação do aluno, sendo realizada de 2004 a 2006. Foi desenvolvida em quatro etapas: realização de grupo de estudos junto às docentes e equipe técnico-pedagógica da escola; assessoramento às docentes para elaboração de planejamento anual e bimestral; elaboração de fichas para acompanhamento do desempenho dos alunos; assessoramento às docentes no preenchimento das fichas de suas respectivas turmas e a realização de reuniões mensais para avaliação e encaminhamento das dificuldades encontradas, na construção de uma prática avaliativa continuada e reflexiva. Obteve-se resultado positivo junto a 50% das docentes. A alta rotatividade destes foi o maior problema enfrentado. Destaca-se a necessidade de elaboração de políticas que a combatam e garantam aos professores condições para se envolverem em projetos voltados à melhoria do trabalho pedagógico e ao enfrentamento das dificuldades existentes no cotidiano escolar.Se ha empezado, en el sistema educacional brasileño, a contar de la década de 1980, la reestructuración de los grados tradicionales de la enseñanza básica en ciclos, apoyada en el fundamento de la ampliación del tempo de aprendizaje del alumno, con la idea de continuidad implícita en ella. El estudio presente ha objetivado investigar las prácticas evaluativas en una escuela pública cuyo currículum es organizado en ciclos de estudios, así como las condiciones necesarias a la concretización de la evaluaci

Efeito anti-proliferativo das infusões de Achyrocline satureioides DC (Asteraceae sobre o ciclo celular de Allium cepa

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Juliana M. Fachinetto

Full Text Available Achyrocline satureioides (marcela é utilizada na medicina popular brasileira, na forma de chá, como tratamento de patologias digestivas e inflamatórias. O efeito anti-proliferativo de infusões de marcela sobre o ciclo celular da cebola foi avaliado, utilizando-se inflorescências de marcela recém coletadas (2005 e após armazenamento por 30 meses (2003. Preparou-se as infusões em duas concentrações: 5,0 mg/mL (concentração usual como chá e 20 mg/mL. Utilizaram-se 3 grupos de 6 bulbos de cebola para cada população de marcela. Retirou-se um grupo de bulbos controle de cada população. Todos os bulbos enraizados em água destilada foram transferidos para os extratos de marcela e permaneceram por 24 horas, (os bulbos controle permaneceram em água. As radículas foram coletadas, fixadas em etanol-ácido acético (3:1 por 24 h e estocadas em álcool 70%. Foram analisadas 6000 células por grupo de bulbos, e os índices mitóticos calculados submetidos a análise estatística pelo teste chi2 a 5%. Conclui-se que as infusões de marcela possuem ação antiproliferativa sobre o ciclo celular da cebola e que essa ação inibitória da divisão celular aumenta conforme aumento da concentração, bem como após o armazenamento.

Alterações nos teores nutricionais foliares de bananeira 'prata-anã' adubada com composto orgânico em cinco ciclos de produção

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Erval Rafael Damatto Junior

2011-10-01

Full Text Available O presente trabalho objetivou avaliar o estado nutricional da bananeira-'Prata-anã' durante cinco ciclos de cultivo com adubação orgânica, no município de Botucatu-SP. As plantas foram adubadas com composto orgânico produzido a partir de serragem de madeira e esterco bovino, em que os tratamentos foram constituídos de doses desse composto (0; 98,5; 197,0; 290,5 e 394,0 g de K2O/planta. Empregou-se delineamento experimental em blocos casualizados, com cinco tratamentos e cinco repetições. No florescimento das plantas em cada ciclo, foram retiradas amostras foliares de duas plantas por parcela para serem analisados os teores de nitrogênio, fósforo, potássio, cálcio, magnésio, enxofre, boro, cobre, ferro, manganês e zinco. A maior parte dos macronutrientes presentes nas folhas não foi influenciada pelo incremento de doses de composto orgânico. No decorrer dos ciclos avaliados, os teores foliares de nitrogênio, fósforo, potássio, enxofre, boro, ferro e manganês diminuíram, enquanto o cálcio e o magnésio se acumularam nas plantas. Os teores de potássio estavam abaixo dos padrões para a cultura no Estado de São Paulo, em todos os anos avaliados, mesmo assim as plantas não apresentaram sintomas de deficiência ou queda de produção, inferindo-se que a faixa considerada como adequada para a cultivar pode ser inferior aos padrões atualmente adotados.

Conceptual Design Study of a Closed Brayton Cycle Turbogenerator for Space Power Thermal-To-Electric Conversion System

Science.gov (United States)

Hansen, Jeff L.

2000-01-01

A conceptual design study was completed for a 360 kW Helium-Xenon closed Brayton cycle turbogenerator. The selected configuration is comprised of a single-shaft gas turbine engine coupled directly to a high-speed generator. The engine turbomachinery includes a 2.5:1 pressure ratio compression system with an inlet corrected flow of 0.44 kg/sec. The single centrifugal stage impeller discharges into a scroll via a vaned diffuser. The scroll routes the air into the cold side sector of the recuperator. The hot gas exits a nuclear reactor radiator at 1300 K and enters the turbine via a single-vaned scroll. The hot gases are expanded through the turbine and then diffused before entering the hot side sector of the recuperator. The single shaft design is supported by air bearings. The high efficiency shaft mounted permanent magnet generator produces an output of 370 kW at a speed of 60,000 rpm. The total weight of the turbogenerator is estimated to be only 123 kg (less than 5% of the total power plant) and has a volume of approximately 0.11 cubic meters. This turbogenerator is a key element in achieving the 40 to 45% overall power plant thermal efficiency.

Resiliencia en estudiantes del V ciclo de educación primaria de una institución educativa del Callao

OpenAIRE

Silva Silva, Rosanna

2012-01-01

La presente investigación descriptiva simple tuvo el propósito de determinar el nivel de resiliencia de los estudiantes del V ciclo de educación primaria de una institución educativa del Callao. Se trabajó con una muestra de 150 estudiantes, cuyas edades fluctúan entre 9 y 12 años de edad. Para procesar resultados se realizó un análisis descriptivo mediante medidas de frecuencias y gráficos de barras para la variable resiliencia y sus respectivas dimensiones. El instrumento aplicado fue el In...

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 ...

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...

Fundamental study of key issues related to advanced sCO₂ Brayton cycle: Prototypic HX development and cavitation

Energy Technology Data Exchange (ETDEWEB)

Ranjan, Devesh [Georgia Inst. of Technology, Atlanta, GA (United States)

2018-01-08

Diffusion bonded heat exchangers are the leading candidates for the sCO₂ Brayton cycles in next generation nuclear power plants. Commercially available diffusion bonded heat exchangers utilize set of continuous semi-circular zigzag micro channels to increase the heat transfer area and enhance heat transfer through increased turbulence production. Such heat exchangers can lead to excessive pressure drop as well as flow maldistribution in the case of poorly designed flow distribution headers. The goal of the current project is to fabricate and test potential discontinuous fin patterns for diffusion bonded heat exchangers; which can achieve desired thermal performance at lower pressure drops. Prototypic discontinuous offset rectangular and Airfoil fin surface geometries were chemically etched on to 316 stainless steel plate and sealed against an un-etched flat pate using O-ring seal emulating diffusion bonded heat exchangers. Thermal-hydraulic performance of these prototypic discontinuous fin geometries was experimentally evaluated and compared to the existing data for the continuous zigzag channels. The data generated from this project will serve as the database for future testing and validation of numerical models.

Ciclos Econômicos e Emissão de CO2 no Brasil: Uma Análise Dinâmica para Políticas Ambientais Ótimas

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Ricardo Aguirre Leal

2015-03-01

Full Text Available Este artigo estuda como as políticas ambientais devem responder de forma ótima aos ciclos econômicos no Brasil. Para isso utilizamos um modelo de ciclos reais de negócios (RBC com externalidades de poluição. Os resultados indicam que o custo de mitigação de emissões de carbono é mais baixo que o da poluição no Brasil, justificando a adoção de políticas restritivas. Além disso, diante de choques de produtividade, o comportamento ótimo é uma política de mitigação pró-cíclica, onde o imposto e o teto de emissões devem aumentar em períodos de expansão da economia e diminuir em períodos de crise. Também definimos uma regra de decisão para a dinâmica da política de mitigação.

Seleção para duração do ciclo vegetativo em batata e relação com a produtividade de tubérculos Selection for vegetative growth period and its relationship to tuber yield of potato

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Gabriel B Rodrigues

2009-09-01

Full Text Available As cultivares de batata no Brasil geralmente apresentam ciclo vegetativo de 90 a 110 dias, sendo bem mais longo em países de clima temperado, podendo chegar até 150 dias. O ciclo vegetativo longo nestes países proporciona maior produtividade e constitui-se em alternativa para aumento da produção de tubérculos sob condições tropicais. Os objetivos deste trabalho foram avaliar o potencial da seleção para aumentar ou diminuir o ciclo vegetativo da batata e verificar a relação entre a duração do ciclo vegetativo e a produção de tubérculos em condições tropicais. Na primeira geração clonal foram avaliados a produção de tubérculos e o ciclo vegetativo de 1.561 genótipos oriundos de 22 famílias clonais. Na segunda geração clonal foram avaliadas as mesmas características em 320 genótipos selecionados para ciclo vegetativo precoce, intermediário e tardio. A seleção nas gerações iniciais foi eficiente, tanto para diminuir permitiu obter maior ganho do que a seleção entre famílias. Os genótipos mais tardios foram mais produtivos que os mais precoces.Potato cultivars in Brazil generally present a growth cycle duration ranging from 90 to 110 days, whereas in countries located in temperate climate it can reach up to 150 days. Longer vegetative growth cycle in these countries confer higher tuber yield and, in tropical countries it also could be an alternative to increase tuber yield. In this work we evaluated the selection potential for longer or shorter growth cycle duration of potato clones and we determined the relationship between growth cycle duration and tuber yield. In the first clonal generation tuber yield and growth cycle duration were evaluated on 1561 genotypes derived from 22 clonal families. In the second clonal generation, the same traits were evaluated on 320 genotypes selected for earliness, intermediate and late vegetative cycle. Selection in the initial generations was efficient both to decrease and to

Análisis de ciclo de vida simplificado aplicado a viviendas de paneles SIP (structural insulated panels

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Juan Pablo Cárdenas

2015-04-01

Full Text Available A medida que los asuntos ambientales se vuelven más importantes, las construcciones se han enfocado en su eficiencia energética y la energía necesaria para construir y producir los materiales. Esta investigación muestra un estudio de Análisis de Ciclo de Vida simplificado de energía operacional y energía contenida de cuatro viviendas nuevas ubicadas en Temuco, Chile, estructuradas con paneles SIP (Structural insulated panel para cuantificar la energía en cada etapa de este sistema de construcción. Para obtener la energía contenida, fueron utilizadas dos bases de datos internacionales para cuantificar la energía de cada material y se determinó la energía contenida en el proceso relacionado a la estructura de paneles SIP a través de mediciones en una compañía especializada en construcción de paneles SIP. Para la energía operacional, se llevaron a cabo modelos computacionales con el software Design Builder y se proyectó esta energía con una vida útil de 50 años. El análisis de la información obtenida muestra que la energía contenida por procesos de construcción representa cerca del 1.7% de la energía contenida y mientras que el total de energía contenida representa el 11% de la energía del ciclo de vida total de las viviendas, el remanente 89% representa la energía de operación. Por otro lado, observamos que las viviendas con paneles SIP generan cifras cercanas al 60% en ahorro en demanda energética, comparadas a las viviendas de mampostería estructural normalmente construidas en esta ciudad.

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

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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

Alterações de equilíbrio postural e qualidade de vida em mulheres no ciclo gravídico puerperal

OpenAIRE

Eufrásio, Laiane Santos

2015-01-01

INTRODUÇÃO: O ciclo gravídico-puerperal causa inúmeras transformações na vida da mulher, sejam elas físicas, hormonais, emocionais ou sociais. Tais alterações podem afetar o equilíbrio postural e a qualidade de vida dessas mulheres na gravidez, podendo persistir no pós-parto. OBJETIVO: Analisar alterações no equilíbrio postural e qualidade de vida em mulheres na gravidez e no pós-parto. METODOLOGIA: Este estudo foi composto por 47 mulheres participantes do Curso para Gestant...

Los materiales manipulativos para la enseñanza de las matemáticas en el 1º ciclo de Primaria

OpenAIRE

Hernández Cabezón, Mercedes

2014-01-01

El trabajo está centrado en el área de matemáticas y concretamente en el 1º ciclo de primaria. Planteo la utilización de materiales manipulativos como eje principal en la consecución de los objetivos. Para llevar a cabo mi propuesta he recopilado información teórica, basándome principalmente en seis autores claves en el ámbito de los materiales – manipulativos. Trabajando con materiales manipulativos el alumno se convierte en el protagonista del proceso, dichos materiales están organizados...

Ciclo de vida, hábitos y enemigos naturales de Liriomyza sativae blanchard (Diptera: agromyzidae), minador del fríjol

OpenAIRE

Cruz L. Jaime de la; Cruz R. Ana M. de la; Cardona J. César

1989-01-01

El presente estudio se realizó en el Centro Internacional de Agricultura Tropical CIAT, Palmira. Se consideró como objetivo principal el estudio biológico del minador del fríjol liriomyza sativae Blanchard, en condiciones controladas de invernadero y sus enemigos naturales. Se hizo la descripción morfológica de todos los estados de desarrollo del insecto y de los daños ocasionados por el adulto. Igualmente se midió la duración del ciclo de vida en condiciones controladas; temperatura promedia...

Estilos parentais e formação do autoconceito vocacional : um estudo com crianças do primeiro ciclo

OpenAIRE

Silva, Ana Rita Vieira da

2016-01-01

Tese de mestrado, Psicologia (Secção de Psicologia da Educação e da Orientação), Universidade de Lisboa, Faculdade de Psicologia, 2016 Com fundamentação na Teoria da Circunscrição e Compromisso (Gottfredson, 1981, 1996, 2006), na Teoria Sociocognitiva da Carreira (Lent, Brown & Hackett, 1984) e no Modelo Tipológico dos Estilos Parentais (Baumrind, 1967, 1971), esta investigação analisa, em crianças do 1º ciclo, a influência dos factores familiares e do género na formação do autoconceito vo...

Properties of noble gases and binary mixtures for closed Brayton Cycle applications

International Nuclear Information System (INIS)

Tournier, Jean-Michel P.; El-Genk, Mohamed S.

2008-01-01

A review is conducted of the properties of the noble gases, helium, neon, argon, krypton and xenon, and their binary mixtures at pressures from 0.1 to 20 MPa and temperatures up to 1400 K. An extensive database of experimental measurements is compiled and used to develop semi-empirical properties correlations. The correlations accurately account for the effects of pressure and temperature on the thermodynamic and transport properties of these gases for potential uses in space (∼2 MPa and up to 1400 K) and terrestrial (∼7.0 MPa and up to 1200 K) applications of Closed Brayton Cycle (CBC). The developed correlations are based on the Chapman-Enskog kinetic theory for dilute gases, and on the application of the law of corresponding states to account for the dependence of properties on pressure. The correlations use the critical temperature and density of the gases as scaling parameters, and their predictions are compared with the compiled database. At temperatures ≥400 K and pressures ≤2 MPa in CBC space power systems, He and Ne, and the binary mixtures of He-Xe and He-Kr with molecular weights ≤40 g/mole behave essentially like a perfect gas, and the error of neglecting the effect of pressure on their compressibility factor, specific heats and transport properties is ≤1%. At a typical operating pressure of 7.0 MPa and up to 1200 K in terrestrial CBC power plants, neglecting the effect of pressure can result in ∼4% error in the properties of noble gases and the binary mixtures of He-Xe and He-Kr with molecular weights ≤40 g/mole, and as much as 20% error for pure argon. Therefore, when operating at pressures >2.0 MPa and/or using noble gases or binary mixtures with molecular weights > 40 g/mole, the present correlations should be used to accurately predict the thermodynamic and transport properties

Padrão do ciclo sono-vigília e sua relação com a ansiedade em estudantes universitários Sleep/wake cycle pattern and its relationship with anxiety in college students

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Katie Moraes de Almondes

2003-04-01

Full Text Available Neste trabalho, foram investigadas as relações entre o ciclo sono-vigília e a ansiedade. O ciclo sono-vigília e traço e estado de ansiedade foram avaliados em 37 estudantes do segundo ano do curso médico. Os estudantes responderam ao Índice de Qualidade de Sono de Pittsburgh - IQSP, ao Inventário de Estado e Traço de Ansiedade - IDATE e a um questionário de matutinidade - vespertinidade (cronotipo. Todos registraram seu sono em um diário durante duas semanas. Os resultados mostraram que os estudantes de medicina tinham altos escores de traço e estado de ansiedade. Aqueles que tinham maiores escores de traço de ansiedade acordavam mais cedo nos dias de semana e finais de semana enquanto os que apresentavam irregularidade do seu ciclo sono-vigília apresentaram maior estado de ansiedade. Sugere-se que há uma relação entre o ciclo sono-vigília e a ansiedade.This paper examines the relationship between the sleep/wake cycle and anxiety in medical students. The sleep/wake cycle and anxiety were evaluated in 37 second year medical school students. The volunteers answered a morningness-eveningness questionnaire, Pittsburgh Sleep Quality Index - PSQI and state and trait of anxiety inventory - STAI; all kept a sleep/wake diary for two weeks. The results showed that the students had high anxiety trait and state. Students who had high anxiety trait had an earlier sleep offset on weekdays and weekend, and students who displayed irregularity in the sleep/wake cycle had high anxiety state. These results suggest a relationship between the sleep/wake cycle and anxiety.

Análise teórica da recuperação de calor para geração de energia em indústrias de cimento e cal utilizando o ciclo de Rankine orgânico

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Ricardo Carrasco Carpio

2015-06-01

Full Text Available O presente trabalho consiste em uma apresentação do estado da arte do Ciclo Rankine Orgânico, um ciclo termodinâmico que usa um fluido orgânico como fluido de trabalho e que pode ser usado para recuperação de calor rejeitado em processos industriais, gerando assim energia elétrica para abastecer a própria indústria, o que consequentemente causa uma redução no custo de produção da empresa. São apresentados alguns fluidos orgânicos e alguns de seus parâmetros termodinâmicos.Palavras-chave: Cogeração. Ciclo Rankine Orgânico. Fluidos de Trabalho.ABSTRACTTheoretical analysis of heat recovery for power generation in cement and lime industries using the organic Rankine cycleThis work aims to present the state of the art of the Organic Rankine Cycle, a thermodynamic cycle that uses an organic fluid as a working fluid that can be used to recover the rejected heat in industrial processes, thus generating electricity to supply industry itself, which causes a reduction in the production cost of the company. It also presents some organic fluids and some of their thermodynamic parameters.Keywords: Cogeneration. Organic Rankine Cycle. Working Fluids.

Ciclo Vital de Schistosoma mansoni através do Holochilus brasiliensis (Desmarest, 1818 em ambiente semi-natural (Trematoda, Shistosomatidae; Rodentia, Cricetidae

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Omar dos Santos Carvalho

1976-10-01

Full Text Available Junto ao Lago da Pampulha, Belo Horizonte, MG, foram capturados (julho/72-novembro/73 28 exemplares de Holochilus brasiliensis, dos quais 11 (39,3% eliminavam nas fezes ovos viáveis de S. mansoni. Miracídios da cepa mencionada ("H" infectaram Biomphalaria glabrata e as cercárias obtidas também infectaram camundongos albinos, recuperando-se, ao final do experimento, 35,3% de vermes adultos. Por outro lado, cercárias de cepa humana ("LE" de S. mansoni infectaram sete exemplares de H. brasiliensis, nascidos em laboratório, recuperando-se no fim de 60 dias, 30,5% de vermes adultos. Estudos anatomapatológicos de H. brasiliensis demonstraram infecção generalizada, encontrando-se granuloma no esôfago, estômago, intestino (delgado e grosso, fígado, baço, pâncreas e linfonodos abdominais. Espessamentos fibrosos da íntima da veia porta, granulomas em espaços porta e fibrose incipiente dos espaços porta e interlobular foram lesões decorrentes da presença de ovos de S. mansoni encontrados no fígado. Em ambiente semi-natural, foi possível fechar o ciclo do S. mansoni sem direta participação humana, utilizando-se B. glabrata experimentalmente infectadas com trematódeos da cepa "LE", H. brasiliensis nascidos em laboratório e B. glabrata nascida no ambiente semi-natural estabelecido. Verificou-se que ambas as cepas ("H" e "LE" comportaram-se de maneira análoga, não sendo verificadas, também, diferenças morfológicas entre os ovos e vermes adultos de ambas. As observações, realizadas no campo e no laboratório demonstraram que o Holochilus brasiliensis é bom hospedeiro de Schistosoma mansoni. Assim, em determinadas áreas e sob certas condições ecológicas, o cricetídeo em questão poderá, efetivamente, integrar-se ao ciclo do trematódeo na natureza, independente ou paralelamente à presença do homem. Assinala-se, finalmente, que o presente trabalho relata o segundo fechamento do ciclo biológico de S. mansoni em condi

Performance study of a combined cycle power plant with integral gasification; Estudio del desempeno de una planta de potencia de ciclo combinado con gasificacion integral

Energy Technology Data Exchange (ETDEWEB)

Gonzalez Rocha, Jose Clemente

2007-04-15

con alto valor agregado, como la gasolina, turbosina o diesel, entre otros. Con la nueva reconfiguracion de las refineria mexicanas de Cd. Madero y Cadereyta y proximamente la terminacion de la reconfiguracion de la refineria de Minatitlan, Veracruz, grandes cantidades de coque se estaran produciendo, con la posibilidad de usarlo mediante la tecnologia de gasificacion para producir un gas sintetico limpio (gasl) con caracteristicas energeticas apropiadas para utilizarse como combustible en un ciclo combinado existente en Mexico. En Mexico se han estimado las posibilidades de generacion de energia electrica a partir del uso del coque de petroleo utilizado la tecnologia de gasificacion o usando generadores de vapor de lecho fluidizado, como es el caso de las planta de potencia TEG en Taquin, San Luis Potosi. Tal es el hecho, que actualmente PEMEX refinacion, tiene terminado el proyecto para construir en Tuxpan, Veracruz una refineria procesadora de crudo Maya con un alto contenido de azufre y junto a la termoelectrica de Tuxpan, contemplandose la posibilidad de aplicar el concepto de ciclo combinado con gasificacion integrada (CCGI); con esta infraestructura sera posible consumir el coque generado por las refinerias mexicanas. La generacion electrica esperada es de 500 MW, de los cuales 100 MW seran para consumo propio de la refineria y 400 MW libres para cubrir la demanda de energia electrica de la zona noreste y centro del pais. El coque de petroleo derivado de las refinerias del pais puede ser utilizado para la generacion limpia de electricidad mediante su gasificacion e integracion a una planta de ciclo combinado existente. La ubicacion estrategia del ciclo combinado Tula, el cual se encuentra adyacente a la refineria Miguel Hidalgo presenta la oportunidad de aplicar la tecnologia de gasificacion como una alternativa viable: primeramente, para la utilizacion de coque de petroleo que actualmente se esta produciendo en las refinerias de Mexico o la utilizacion del

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.

Ciclo anual de la clorofila-α satelital en el archipiélago de Juan Fernández (33°S), Chile

OpenAIRE

Andrade,Isabel; Hormazabal,Samuel E; Correa-Ramirez,Marco A

2012-01-01

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 estimulación del lenguaje oral a partir de los cuentos en el primer ciclo de educación primaria

OpenAIRE

Torres Jaramillo, Ana María

2014-01-01

El trabajo que se expone a continuación es una propuesta de intervención para trabajar el lenguaje oral en los alumnos del primer ciclo de Educación Primaria. En él, me he marcado unos objetivos, partiendo de la base legal del currículo de Educación Primaria, de modo que, esta propuesta de trabajo pueda desarrollarse en el aula formando parte del currículo. Contiene aspectos teóricos referidos al lenguaje, destacando la importancia del lenguaje oral y un breve desarrollo del lenguaj...

Aplicación del ciclo phva para el mejoramiento del Control de Piso en una empresa de productos médicos

OpenAIRE

Molina-Mesías, Óscar Armando; Benítez-Ramírez, Lauren; González, Eusebio

2013-01-01

Introducción: la investigación se desarrolló en la empresa industrial de Cali Bsn Medical Ltda., con el fin de identificar las variables que generan inconvenientes en el Control de Piso. Se presentó una propuesta de mejoramiento que cumple los objetivos establecidos de acuerdo con la secuencia del ciclo phva (planear, hacer, verificar, actuar). Metodología: el estudio es exploratorio, no experimental, se trabaja a partir de eventos y escenarios preexistentes, sin manipulación deliberada de la...

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

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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

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)

Concentração do ciclo de produção de pinhão-manso por meio de podas de formação ou de produção

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Vânia Aparecida Silva

2012-01-01

Full Text Available O objetivo deste trabalho foi avaliar a possibilidade de concentração do ciclo de produção de pinhão-manso (Jatropha curcas, por meio do emprego de diferentes podas de formação e de produção. Realizou-se um experimento para cada tipo de poda, no semiárido de Minas Gerais, com cinco tratamentos cada um. Os tratamentos estiveram relacionados a alturas de poda no ramo principal e à poda ou desbrota nos ramos secundários. Com a poda de formação, foi possível reduzir o período de colheita de 120 para 48 dias, mas com prejuízo significativo para a produtividade no primeiro ciclo. A poda de produção pode concentrar a colheita a 90 dias e, em alguns casos, aumentar a produtividade das plantas.

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)

Sogut, Oguz Salim; Ust, Yasin; Sahin, Bahri

2006-01-01

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 (ECOP max ) are always less than those of at the maximum ecological function ( E-dot max ) and the maximum power output conditions ( W-dot max ) leading to a design that requires less investment cost. It is also concluded that a design at ECOP max conditions has the advantage of higher thermal efficiency and a lesser entropy generation rate, but at the cost of a slight power loss

Diseño y construcción de una turbina de gas para generación de baja potencia (TGBP con ciclo regenerativo a partir de un turbocargador

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Cesar Eduardo Mondragón Cediel

2010-01-01

Full Text Available La ciudad de Cantagallo (Bolívar en Colombia requiere 21kW de energía eléctrica para suplir las necesidades de su población ya que no tiene acceso a la red de interconexión eléctrica como muchas otras ciudades del país. La aplicación de la generación distribuida a partir de turbinas de gas de baja potencia (TGBP para suplir estas necesidades es viable en Colombia, además las TGBP a partir de turbocargadores automotrices suplen completamente los requerimientos de la generación distribuida aislada y de soporte de la red de distribución en plantas, fábricas y edificios; por lo tanto se realiza el dise.o detallado y construcción de una TGBP que genera 30kW, cuyas características específicas y técnicas le permiten ser aplicable como sistema de Generación Distribuida en Colombia a partir de un turbocargador automotriz empleando el ciclo termodinámico regenerativo para disminuir  el consumo espec.fico de combustible (SFC y por lo tanto aumentar la eficiencia del ciclo, con sus respectivos sistemas de inyección de combustible, ignición, lubricación y de adquisición de datos. Se realiza una metodolog.a de dise.o de: TGBP con ciclo regenerativo, de c.maras de combusti.n tubulares y de intercambiadores de calor (recuperadores empleando fuentes bibliográficas especializadas en el desarrollo de motores a reacción a nivel mundial así como software FEA, CFD y tecnologías de fabricación asequibles y encontradas en Colombia.

Expectativa y ciclo: hacia una dinámica keynesiana

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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.

Efeitos de ciclos de umedecimento e secagem na reorganização da estrutura microgranular de latossolos Effects of wetting and drying cycles on the reorganization of the microgranular structure of latosols

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J. H. M. Viana

2004-02-01

Full Text Available Um experimento foi realizado em casa de vegetação com o objetivo de examinar as modificações provocadas por ciclos de umedecimento e secagem em amostras de Latossolos com diferentes mineralogias, em agregados integrais ou quando destruídos por moagem. Amostras de terra fina seca ao ar foram passadas em peneira de 1,0 mm e subdivididas em grupos: solo integral não moído e solo moído em almofariz e passado em peneira de 0,105 mm. O solo moído foi ainda subdividido em solo moído puro ou adicionado de ácido húmico purificado. Os materiais foram montados em cilindro de alumínio e submetidos a dez ciclos sucessivos de umedecimento e secagem, realizados por ascensão capilar, seguidos por secagem ao ar, com intervalo de sete dias entre cada ciclo. Após o término dos ciclos, os solos foram impregnados com resina de poliéster, montando-se seções finas para microscopia, as quais foram levadas para observação em microscópio ótico e fotografadas. As imagens obtidas foram digitalizadas, analisadas e quantificadas por meio do programa QUANTIPORO, desenvolvido no Departamento de Solos/Universidade Federal de Viçosa. Os resultados mostraram completa modificação na forma e no padrão da estrutura após a aplicação dos ciclos nos tratamentos que sofreram destruição de agregados por moagem. Essas mudanças foram atribuídas a uma reacomodação dos agregados fragmentados com a retração do plasma, que se seguiu ao processo de secagem. Todos os materiais estudados mostraram uma estrutura bem diferente da estrutura primária original destes solos. Não se observou qualquer tendência à reversão da estrutura após os dez ciclos, demonstrando que outros fatores, além dos físico-químicos e mineralógicos, devem ser invocados para explicar a gênese de microagregados em Latossolos.A greenhouse experiment was conducted to examine the structural modifications engendered by wetting-drying cycles in Latosol samples (Oxisols with different

Ticks (Acari: Ixodidae as ectoparasites of Brazilian wild birds and their association with rickettsial diseases

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Maria Ogrzewalska

2016-04-01

Full Text Available Os carrapatos (Acari: Ixodoidea são ectoparasitas obrigatórias de uma variedade de hospedeiros vertebrados e têm um papel importante na ecologia e transmissão de diversos patógenos causadores de doenças em humanos e animais no mundo todo. No Brasil existem 68 espécies de carrapatos e pelo menos 23 espécies são encontradas parasitando aves silvestres. Esse número tem crescido com o advento de novos estudos ressaltando o papel das aves nos ciclos de vida desses artrópodes. Na América do Sul alguns desses carrapatos estão envolvidos na epidemiologia de doenças graves para o ser humano, como a febre maculosa, causada por bactérias do gênero Rickettsia (Rickettsiales: Rickettsiaceae. O alvo desse artigo é apresentar o estado atual de conhecimento sobre a fauna de carrapatos encontrados em aves no Brasil e as associações estabelecidas com as riquetsioses. A literatura disponível sobre carrapatos em aves e ocorrência de riquétsias foi revisada e pôde ser concluído que aves têm um papel importante nos ciclos de vida de várias espécies de carrapatos, sendo especialmente importantes para os estágios imaturos (larvas e ninfas. A maior parte do conhecimento sabrecai na fauna de carrapatos de aves dos biomas Mata Atlântica e Cerrado no sudeste e centro-oeste do Brasil. Já o conhecimento sobre o parasitismo por carrapatos em aves dos outros biomas: Amazônia, Caatinga, Pantanal e Pampas é muito limitado. Além disso, não há estudos sobre o papel de aves como disseminadores de carrapatos entre áreas e também o papel de aves no ciclo de Rickettsia não está totalmente esclarecido.

Estudios comparativos del ciclo de vida del mosquito Aedes taeniorhynchus (Diptera: culicidae de dos colonias de la costa atlántica colombiana

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Claribell Hernández

1996-12-01

Full Text Available Este estudio se realizó con el propósito de establecer, en forma preliminar, en el laboratorio, si el mosquito Aedes taeniorhynchus procedente de Barranquilla y Cartagena es realmente una sola cepa y si el proceso de colonización (cría en el laboratorio influye en el tiempo de duración de las etapas de desarrollo del ciclo de vida de este díptero. Las colonias se establecieron con mosquitos adultos, machos y hembras, recolectados en lugares cercanos a Barranquilla y Cartagena. Los insectos se identificaron taxonómicamente y se colocaron en jaulas Gerberg, en las que se introdujeron tazas con tierra húmeda para que las hembras ovipositaran. De cada localidad, se mantuvieron seis generaciones continuas a una temperatura promedio de 27°C y una humedad relativa promedio de 80%. Los estadios inmaduros se alimentaron con Ken-L molido; los adultos de los dos sexos, con solución azucarada y a las hembras se les colocó un curí para que tomaran su comida de sangre. Se registraron los tiempos de duración de cada etapa del ciclo biológico en cada una de las generaciones y se analizaron por medio de la prueba t de comparación de promedios para muestras independientes. Para los tiempos de duración de larva (t=1,51 y pupa (t=0,30 de las dos poblaciones del mosquito, no se encontraron diferencias significativas; sin embargo, para el tiempo de eclosión de la larva sí las hubo (t=4,21. Al relacionar las seis generaciones de Cartagena no se encontraron diferencias significativas para el tiempo de duración de pupa y eclosión de la larva, pero sí se presentaron a partir de la cuarta generación, para el tiempo de duración de los estadios larvarios. Los resultados de este estudio preliminar sugieren que el mosquito Aedes taeniorhynchus de Barranquilla y Cartagena representa una sola especie. Se demostró, además, que su proceso de colonización, el cual involucra la adaptación de este insecto a las condiciones específicas de un insectario

Envejecimiento saludable: perspectiva de género y de ciclo vital

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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.

Modelo de Sistema de Control de Prótesis de Rodilla Transfemoral para un Ciclo de Marcha

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Filiberto Fernández Castañeda

2012-06-01

Full Text Available Normal 0 21 false false false ES X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}  En este trabajo se presenta el diseño de un modelo para el sistema de control de una prótesis de rodilla, para un ciclo de marcha humana. El modelo es simulado a través de herramientas computacionales como el Simulink y SimMechanics, en este caso, considerando el modelo biomecánico del péndulo doble como una representación de la pierna humana y basada en los parámetros del antropométricos. A través del análisis y estudio de la marcha humana normal se desarrolla un método de control e identificación de las fases del ciclo de marcha humana, para actuar en la articulación de la rodilla con empleo de una prótesis transfemoral. Entre los principales resultados, se destaca el logro de un control preciso de la posición durante la flexión de la rodilla, que le confiere un desarrollo del proceso de marcha con la prótesis muy similar a la marcha normal.

Ciclo de vida de Culex quinquefasciatus Say, 1826 (Diptera: Culicidae bajo condiciones no controladas en Bogotá.

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Myriam Janeth Salazar

2004-12-01

Full Text Available El objetivo de este trabajo fue estudiar varios aspectos del crecimiento y el desarrollo de los estadios inmaduros de Culex quinquefasciatus Say, 1826 (Diptera: Culicidae, especie antropofílica frecuentemente encontrada en Bogotá. Con este fin, se realizaron dos experimentos en diferentes épocas del año 2001 (enero-febrero y septiembre-octubre, bajo condiciones no controladas (luz, temperatura y humedad relativa. Se colocaron recipientes plásticos transparentes con agua de charca a la que se le adicionó concentrado para perro; se tomaron cuatro balsas al azar para estudiar el ciclo de vida utilizando los parámetros de la tabla de vida: mortalidad y supervivencia. Las hembras ovipositaron entre cinco y ocho días después de la ingestión de sangre. El número de huevos por balsa varió entre 152 y 203. La eclosión de larvas L1 fue de 50% en el primer experimento y de 75% en el segundo. Se destacó la naturaleza no sincrónica de la eclosión de las L1, la menor duración proporcional del estadio de pupa (11% del tiempo del desarrollo total y la eficiencia del cambio pupa-adulto (98,61%. Se reporta una menor duración del ciclo de lo informado previamente. Además, los altos porcentajes de eclosión (83,58%, pupación (86,63% y emergencia (98,61% con las condiciones presentes para estos experimentos (temperatura media 14,8°C y 15,1°C y humedad relativa del 72,5% y 74,1%, respectivamente indican el alto grado de adaptación de C. quinquefasciatus al ambiente bogotano. Estas características, más la capacidad vectorial y la resistencia a los insecticidas, hacen de esta especie un problema de salud pública.

Use of High-Power Brayton Nuclear Electric Propulsion (NEP) for a 2033 Mars Round-Trip Mission

International Nuclear Information System (INIS)

McGuire, Melissa L.; Martini, Michael C.; Packard, Thomas W.; Weglian, John E.; Gilland, James H.

2006-01-01

The Revolutionary Aerospace Systems Concepts (RASC) team, led by the NASA Langley Research Center, is tasked with exploring revolutionary new approaches to enabling NASA to achieve its strategic goals and objectives in future missions. This paper provides the details from the 2004-2005 RASC study of a point-design that uses a high-power nuclear electric propulsion (NEP) based space transportation architecture to support a manned mission to Mars. The study assumes a high-temperature liquid-metal cooled fission reactor with a Brayton power conversion system to generate the electrical power required by magnetoplasmadynamic (MPD) thrusters. The architecture includes a cargo vehicle with an NEP system providing 5 MW of electrical power and a crewed vehicle with an NEP system with two reactors providing a combined total of 10 MW of electrical power. Both vehicles use a low-thrust, high-efficiency (5000 sec specific impulse) MPD system to conduct a spiral-out of the Earth gravity well, a low-thrust heliocentric trajectory, and a spiral-in at Mars with arrival late in 2033. The cargo vehicle carries two moon landers to Mars and arrives shortly before the crewed vehicle. The crewed vehicle and cargo vehicle rendezvous in Mars orbit and, over the course of the 60-day stay, the crew conducts nine-day excursions to Phobos and Deimos with the landers. The crewed vehicle then spirals out of Martian orbit and returns via a low-thrust trajectory to conduct an Earth flyby. The crew separates from the vehicle prior to Earth flyby and aerobrakes for a direct-entry landing

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

International Nuclear Information System (INIS)

Jansen, E.; Bello-Ochende, T.; Meyer, J.P.

2015-01-01

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

Acción colectiva de las organizaciones de población desplazada en Medellín. Ciclos, contextos, repertorios y perspectivas

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James Gilberto Granada Vahos

2009-01-01

Full Text Available El presente artículo ubica, como asunto de preocupación académica y social, el papel activo que los desplazados internos han jugado como sujetos colectivos en la lucha por la garantía y el restablecimiento de sus derechos. Retomando la teoría sobre los movimientos sociales construida por Sidney Tarrow, se reflexiona acerca de dos ciclos de acción colectiva: 1996-2003 y 2004-2009. En ellos se muestra el aumento y diferenciación de las acciones llevadas a cabo por la población desplazada que se asienta en el municipio de Medellín; se referencian las estructuras de contexto que incentivaron, abrieron oportunidades o limitaron la puesta en marcha de las acciones colectivas; se analizan los repertorios para la acción y las diversas formas de interacción entre los sujetos afectados y la administración municipal. Con esto se busca constatar, en el último ciclo, que aparecen formas re-creadas de acción y participación de la población desplazada, tanto a la hora de relacionarse con las instancias e instituciones encargadas de la política, como en el fragor de las acciones de hecho, y que ambas son formas de acción que llaman la atención sobre la garantía de sus derechos conculcados, lo cual se constituye, sin duda, como un reto para la Mesa de Organizaciones de Población Desplazada en Medellín.

Aspectos hidro-limnológicos en las ciénagas de Chucuri y Aguas Negras (Magdalena Medio, Colombia) durante un ciclo anual

OpenAIRE

García Lozano Luis Carlos; Márquez Calle Germán; Pedraza Gilma Estella

1989-01-01

El presente estudio analiza características hrdrológicas-limnológicas de la estructura y funcionamiento de las ciénagas de Chucuri y Aguas Negras localizadas en la planicie aluvial del Valle Medio del rio Magdalena. Se basa en seguimientos bimensuales en diez estaciones de muestreo, durante el ciclo anual: abril de 1983 a marzo de 1984. Se resalta la presencia de dos estadios definidos asociados al régimen de inundación y sequia con rasgos característicos en la comunidad fitoplanctón...

MEJORAMIENTO DEL RENDIMIENTO Y CALIDAD DE FRUTO Y PSEUDOFRUTO DE MARAÑON CON UN CICLO DE FERTILIZACIÓN ORGÁNICA

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LOURDES ADRIANO-ANAYA

2017-12-01

Full Text Available RESUMEN El objetivo del presente estudio fue evaluar la influencia de la aplicación de fertilizantes orgánicos a árboles adultos de marañón por un ciclo productivo sobre la producción y calidad de frutos y pseudofrutos. Para lo anterior, se establecieron tres tratamientos: fertilización orgánica (BIO, fertilización sintética (FS y sin fertilización (SF. Se cuantificó el número de panículas m-3, número de flores por panícula y el número de frutos m-3 en los árboles. Después del corte, a frutos y pseudofrutos se analizaron propiedades físicoquímicas de interés. Aunque el tratamiento FS promovió mayor número de panículas por unidad de área foliar (P 0.05, medido como la cantidad de fruto-pseudofruto m-3 con el tratamiento BIO. Sin embargo, la cantidad de fruto (principal producto comercializado fue mayor en BIO (1.80 kg árbol-1 comparado con los otros dos tratamientos (FS = 1.35; SF = 1.09. El tratamiento BIO aumentó en 81% el contenido de polifenoles respecto al tratamiento no fertilizado. Igualmente, los contenidos de grasa y acidez titulable fueron superiores en BIO, respecto a los tratamientos sin fertilización y con fertilización sintética (P < 0.05. Se demostró que la aplicación de biofertilizantes por un ciclo de producción aumenta la producción de frutos y modifica la composición química de las semillas.

Segundo ciclo de la licenciatura de traducción e interpretación en formato semipresencial en la universidad de VIC

OpenAIRE

Cánovas, Marcos

2005-01-01

La Facultad de Ciencias Humanas, Traducción y Documentación de la Universidad de Vic ofrece desde el curso 2001-2002 el segundo ciclo de la licenciatura de Traducción e Interpretación en formato semipresencial o de blended learning, con el apoyo de entornos virtuales de enseñanza. En la presente comunicación se realiza una descripción del diseño del curso; se tendrán especialmente en cuenta aspectos como el entorno didáctico, el papel del profesorado, la perspectiva de los estudiantes, los fa...

1-N-aminoindol derivatives synthesis in no aqueous means from the 1, 4-dihydrocinnoline obtained by electrolysis in continuous flow redox cell; Sintesis de derivados del 1-N-aminoindol en medios no acuosos a partir de la 1, 4-dihidrocinolina obtenida por electrolisis en celda redox de flujo continuo

Energy Technology Data Exchange (ETDEWEB)

Frontana-Uribe, Bernardo A. [Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico); Moinet, Claude [Laboratoire d' Electrochimie et Organometalliques UMR, Paris (France)

1999-08-01

This work describes the synthesis of 1-N-aminoindol derivatives in organic anhydrous media from 1, 4-dihydrocinnoline. 1, 4-dihydrocinnoline 4 is obtained by electrolysis of 2-(orto-notropheny)-ethylamine 1a in a continuous flow redox cell. The cinnoline ring contraction products are obtained in low yield, but they show the possibility to carry out the reaction in organic media without water addition, as it was noted in previous works. [Spanish] En este trabajo se describe la sintesis de derivados del 1-N-aminoindol en medios anhidros a partir de la 1, 4-dihidrocinolina 4. Esta se obtiene mediante la electrolisis de la 2-(orto-notrofenil)-etilamina 1a en celda redox de flujo continuo. Los productos de contraccion del ciclo de la cinolina en 1-N-aminoindol se obtiene en rendimiento bajo, pero demuestran la posibilidad de llevar a cabo esta reaccion en medios totalmente organicos, sin la necesidad de la adicion de agua en el medio de reaccion, como esta descrito en trabajos precedentes.

Investigación: Modelo de ciclo de negocios real con dinero endógeno y política monetaria pasiva

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Carlos Guberman

2015-11-01

Full Text Available Construimos un modelo de ciclo de negocios real con dinero endógeno y política monetaria pasiva, que muestra algunas particularidades en cuanto a la dinámica de las tasas de interés y los mercados de crédito. Encontramos que el modelo es estable, aspecto que consideramos ausente en la literatura relacionada con la política monetaria pasiva. Creemos que este trabajo puede ser un buen punto de partida para el análisis de lo sucedido antes, durante y después de la crisis financiera internacional que comenzó en el mercado de crédito colateralizado.

La psicopedagogía como disciplina: una perspectiva contextualista y de ciclo vital = Psicopedagogy as a discipline: an environmental and life-cycle approach

OpenAIRE

Poveda, David

2003-01-01

Este artículo plantea aproximarse a la Psicopedagogía desde dos ejes, uno compuesto por los contextos de desarrollo en los que participan los seres humanos y otro compuesto por las diferentes etapas del ciclo vital. Así, la cuestión clave es comprender cómo el desarrollo educativo a lo largo del tiempo esta íntimamente relacionado con diferentes contextos sociales. Para las personas en desarrollo esto implica enfrentarse a las continuidades y discontinuidades entre los contextos y etapas del ...

Trayectorias y ciclos de explotación sexual y trata para la explotación sexual de mujeres en la Amazonía peruana

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Jaris Mujica

2014-01-01

Full Text Available La explotación sexual comercial es una actividad constante y extendida en varias partes del Amazonía peruana. en los alrededores del puerto fluvial de Pucallpa, en la región Ucayali, esa práctica aparece sistemáticamente: las adolescentes que atienden las precarias tabernas alrededor del puerto y aquellas dedicadas a las labores de cocina en los campamentos madereros son víctimas de explotación constante, y muchas de ellas también de trata de personas. este artículo se dirige a reconstruir la trayectoria de vida y el ciclo de reproducción de las formas de explotación en una muestra de veinte mujeres, y se concentra en: (i la evidencia de formas de explotación estacionales; (ii la trayectoria de vida de estas mujeres que muestra pasos en una cadena de explotación de varias etapas y en diferentes áreas de trabajo; (iii en ese contexto, la explotación sexual y la trata parecen no ser fenómenos permanentes sino estar concentrados en un momento de la trayectoria y detenerse con la maternidad, entre los 19 y 25 años, y (iv con la maternidad y el asentamiento matrilocal, las hijas e hijos repiten el ciclo y reproducen la cadena.

Ocho Ciclos de Selección Masal Divergente por Mazorcas por Planta en una Variedad Sintética de Maíz

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Torregroza C. Manuel

1974-08-01

Full Text Available Para evaluar la selección masal, como método de mejoramiento genético de maíz, se inició en Tibaitatá a partir de 1956 una serie de proyectos, cuyo objetivo fundamental ha sido el de utilizar dicho método para obtener variedades mejoradas prolíficas y de alta productividad. En 1960 comenzó a aplicarse un sistema divergente de selección masal por mazorcas por planta en Harinoso Mosquera I Sin. 2, una variedad sintética de maíz obtenida del primer ciclo de selección recurrente reciproca, en la cual el otro recurso germoplásmico era Rocamex V 7. Los ocho ciclos de selección analizados en este estudio se obtuvieron en sendos lotes aislados de aproximadamente un cuarto de hectárea. Las siembras se hacían en tal forma que se dejaba una población equivalente a 40 mil plantas por hectárea, así como también se aplicaba una Intensidad de selección del 15 por ciento. No se usó estratificación en el momento de la cosecha. Los ciclos de selección masal divergente obtenidos, se evaluaron en Tibaitatá durante tres años así: de 1968 a 1967, los ciclos 2, 3, 4 y 5; de 1968 a 1970 los ciclos 5, 6, 7 y 8. Para ello, el material se sembró en bloques completos al azar de 16 repeticiones y nueve tratamientos. En todos los experimentos se utilizó la variedad original, como testigo. El tamaño de las parcelas experimentales fue de 2 x 10, para una población máxima de 60 plantas por parcela. En base al promedio de tres años de evaluación en una localidad, el octavo ciclo cie selección para plantas prolíficas mostró una ganancia total del 35 y 39 por ciento para productividad y prolificidad, respectivamente. Cuando estos resultados se expresaron en función de los coeficientes de regresión, los incrementos por ciclo de selección fueron en su orden de 5.93 y 3.43 por ciento. En la selección en sentido opuesto, es decir, en el sistema de escoger plantas con una sola mazorca, el octavo ciclo rindió igual que la variedad

EFECTO DEL PROCESAMIENTO DE LA DIETA SOBRE EL DESEMPEÑO PRODUCTIVO DE TILAPIA NILÓTICA (Oreochromis niloticus Var. Chitralada EN UN CICLO COMERCIAL DE PRODUCCIÓN

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F. Aguilar

2010-01-01

Full Text Available Este estudio evaluó el efecto del procesamiento de alimento (extruido frente a peletizado sobre el desempeño productivo de tilapia nilótica durante un ciclo comercial de producción. Se utilizaron 504 alevinos reversados que fueron alimentados con un sistema de alimentación por fases (alevinaje, crecimiento 1, crecimiento 2 y finalización con niveles de proteína cruda para cada fase de 43,10%, 36,40%, 31,50% y 28,65% respectivamente. Las dietas fueron procesadas (extruidas o peletizadas en micro extrusora para laboratorio Exteec® (Exteec máquinas, Brasil. El análisis de los indicadores acumulados mostró que el proceso de extrusión generó un mayor crecimiento y una mayor eficiencia en el uso de alimento hasta la fase de crecimiento 2 (P<0,05. En la fase de finalización los desempeños fueron similares entre los tipos de procesamiento, respuesta que podría estar asociada con una mayor densidad en términos de biomasa alcanzada por el grupo alimentado con alimento extruido generando así que el desempeño global del ciclo no presentara diferencias entre los tratamientos.

Evolução da anatomia radicular do milho 'Saracura' em ciclos de seleção sucessivos Evolution of the root anatomy of 'Saracura' maize in successive selection cycles

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Fabricio José Pereira

2008-12-01

Full Text Available Este trabalho teve como objetivo verificar as modificações nas características anatômicas radiculares relacionadas à hipoxia, durante 18 ciclos de seleção da variedade de milho (Zea mays BRS 4154 Saracura, adaptada a áreas sujeitas a alagamento. A variedade BR 107 e o híbrido simples BRS 1010, suscetíveis ao alagamento, foram utilizados como controle. As diferentes cultivares foram submetidas a alagamentos intermitentes, a cada dois dias, durante dois meses. As amostras radiculares foram preparadas e analisadas em microscopiaóptica. Em relação ao grupo controle e aos ciclos anteriores de seleção, a BRS 4154 teve aumento na formação de aerênquima, diminuição do córtex, diminuição do diâmetro dos vasos, diminuição da camada subepidérmica, aumento na espessura do floema e epiderme. Os sucessivos ciclos de seleção melhoraram as características do milho 'Saracura' e sua tolerância a ambientes alagados.This work aimed to verify the modifications in the root anatomical characteristics related to hypoxia, along 18 selection cycles of the maize (Zea mays cultivar BRS 4154 Saracura, adapted to areas subject to flooding. Cultivars not tolerant to fooding, BR 107 and the simple hybrid BRS 1010, were used as controls. The different cultivars were subjected to intermittent soil waterlogging every two days for two months. The root samples were prepared and analyzed through light microscopy. Compared to the controls group and to early selection cycles, BRS 4154 had increased development of aerenchyma, decreased cortex thickness, decreased metaxylem diameter, decreased subepidermal layer, and increased epidermis and phloem thickness. The successive selection cycles improved 'Saracura' maize characteristics and its tolerance to flooding environments.

Virus del dengue: estructura y ciclo viral Dengue virus: structure and viral cycle

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Myriam L Velandia

2011-03-01

Full Text Available El virus del dengue (DENV es el agente causal de la enfermedad conocida como dengue, que es la principal enfermedad viral transmitida por artrópodos en el mundo. El DENV es un flavivirus que ingresa por endocitosis y se replica en el citoplasma de la célula infectada, originando tres proteínas estructurales y siete proteínas no estructurales, sobre las cuales se conocen sólo algunas de sus funciones en la replicación viral o en la infección. El ciclo viral que ocurre en las células infectadas hasta ahora está comenzando a aclararse y su conocimiento permitirá en el futuro próximo diseñar racionalmente moléculas que lo intervengan y eviten la replicación del virus. Durante la infección, el individuo puede presentar fiebre indiferenciada o, en otros casos, puede presentar un proceso generalizado de activación de la respuesta inmunitaria innata y adquirida, lo cual provoca la liberación de factores inflamatorios solubles que alteran la fisiología de los tejidos, principalmente el endotelio, conllevando al desarrollo de manifestaciones clínicas graves. Aunque se ha identificado un gran número de factores del individuo asociados al desarrollo de la enfermedad por DENV, queda por identificar el papel de las diferentes proteínas virales en la patogenia de la enfermedad. En la presente revisión, se presenta una breve actualización sobre la estructura y biología del DENV, de su ciclo viral intracelular y, finalmente, se introducen algunos conceptos sobre la inmunopatogenia de la enfermedad producida por este agente.Dengue virus (DENV is responsible for the clinical entity known as dengue that is a great concern for economy and public health of tropical countries. This flavivirus is a single strand RNA virus that after their translation and replication in host cells produces three structural and seven non-structural proteins with specific function in replication or cell binding process that we will describe here. Intracellular

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

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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. 

Propuesta de contenidos de danza para la Educación Física en el primer ciclo de la Enseñanza Primaria

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Marilys Mesa Fonseca

2007-12-01

Full Text Available En el presente estudio se pretende exponer una propuesta de contenidos específicos de expresión corporal (danza, para el primer ciclo de la enseñaza primaria, con una adecuada base teórica que sustente la propuesta y los resultados de esta investigación sobre la expresión corporal en el ámbito educativo que, a partir, de sus contenidos posibilitará trabajar el movimiento en función de potenciar las habilidades comunicativas en edades tempranas, dirigiendo tareas hacia el desarrollo armónico de la personalidad, permitiendo una equilibrada existencia física y mental y posibilitando además una salida a la imaginación, creatividad, expresividad y originalidad individual La propuesta que se presenta es la visión o el enfoque particular de un trabajo concreto que se desarrolla en la formación integral de la infancia en el primer ciclo de la Educación Física en la enseñanza primaria. Como contenidos específicos se contemplaran: las actividades de interacción, de familiarización con el ritmo, de adaptación a las cualidades del sonido y a los elementos de la música, así como las posibles técnicas de danza apropiadas para esta etapa educativa. Todo ello desde un objetivo muy claro: contribuir a la formación integral del alumno a través de los contenidos de la danza.

Estudo do comportamento térmico de laminados carbono/epóxi submetidos a múltiplos ciclos térmicos

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Christiane Sales Reis de Souza

2016-01-01

Full Text Available Resumo Este trabalho apresenta um estudo comparativo dos comportamentos térmicos de três famílias de laminados de fibra de carbono/resina epóxi, submetidas a múltiplos ciclos térmicos, via análises termogravimétricas e dinâmico-mecânicas. Este estudo procura aliar a possibilidade de utilização de retalhos de pré-impregnados de fibra de carbono com resina epóxi - um material nobre na indústria aeronáutica, por meio da comparação do comportamento térmico de um laminado preparado com retalhos de pré-impregnados (laminado R, com outros dois laminados, sendo um manufaturado com prepreg comercial (laminado A e um terceiro obtido por impregnação manual de reforço seco de fibra de carbono com resina epóxi (laminado B. Os laminados curados a 180 °C foram submetidos a múltiplos ciclos térmicos, totalizando 40, 100 e 300 h de exposição na temperatura máxima de 180 °C. As análises termogravimétricas mostram que os laminados submetidos às múltiplas ciclagens apresentam estabilidade térmica na temperatura de 180 °C, com perda de massa relativa à umidade absorvida pelos laminados. As análises dinâmico-mecânicas evidenciam que as múltiplas ciclagens térmicas afetam pouco ou até aumentam as temperaturas de transição vítrea dos sistemas de resinas epóxis estudados. A partir dos resultados obtidos pode-se afirmar que os laminados submetidos às múltiplas ciclagens térmicas apresentam estabilidade térmica suficiente para serem utilizados, por exemplo, em ferramentais de cura de componentes aeronáuticos.

Optimal temperature of operation of the cold side of a closed Brayton Cycle for space nuclear propulsion

Energy Technology Data Exchange (ETDEWEB)

Romano, Luís F.R.; Ribeiro, Guilherme B., E-mail: luisromano_91@hotmail.com, E-mail: gbribeiro@ieav.cta.br [Instituto Tecnológico de Aeronáutica (ITA), São José dos Campos, SP (Brazil). Pós-Graduação Ciências e Tecnologias Espaciais

2017-07-01

Generating energy in space is a tough challenge, especially because it has to be used efficiently. The optimization of the system operation has to be though up since the design phase and all the minutiae between conception, production and operation should be carefully evaluated in order to deliver a functioning device that will meet all the mission's goals. This work seeks on further describing the operation of a Closed Brayton Cycle coupled toa nuclear microreactor used to generate energy to power spacecraft's systems, focusing specially on the cold side to evaluate the temperature of operation of the cold heat pipes in order to aid the selection of proper models to numerically describe the heat pipes and radiator s thermal operation. The cycle is designed to operate with a noble gas mixture of Helium-Xenon with a molecular weight of 40g/mole, selected for its transport properties and low turbomachinery charge and it is to exchange hear directly with the cold heat pipe' evaporator through convection at the cold heat exchanger. Properties such as size and mass are relevant to be analyzed due space applications requiring a careful development of the equipment in order to fit inside the launcher as well as lowering launch costs. Merit figures comparing both second law energetic efficiency and net energy availability with the device's radiator size are used in order to represent an energetic production density for the apparatus, which is ought to be launched from earth's surface. (author)

Optimal temperature of operation of the cold side of a closed Brayton Cycle for space nuclear propulsion

International Nuclear Information System (INIS)

Romano, Luís F.R.; Ribeiro, Guilherme B.

2017-01-01

Generating energy in space is a tough challenge, especially because it has to be used efficiently. The optimization of the system operation has to be though up since the design phase and all the minutiae between conception, production and operation should be carefully evaluated in order to deliver a functioning device that will meet all the mission's goals. This work seeks on further describing the operation of a Closed Brayton Cycle coupled toa nuclear microreactor used to generate energy to power spacecraft's systems, focusing specially on the cold side to evaluate the temperature of operation of the cold heat pipes in order to aid the selection of proper models to numerically describe the heat pipes and radiator s thermal operation. The cycle is designed to operate with a noble gas mixture of Helium-Xenon with a molecular weight of 40g/mole, selected for its transport properties and low turbomachinery charge and it is to exchange hear directly with the cold heat pipe' evaporator through convection at the cold heat exchanger. Properties such as size and mass are relevant to be analyzed due space applications requiring a careful development of the equipment in order to fit inside the launcher as well as lowering launch costs. Merit figures comparing both second law energetic efficiency and net energy availability with the device's radiator size are used in order to represent an energetic production density for the apparatus, which is ought to be launched from earth's surface. (author)

Formación Profesional y género. Una aproximación al estado actual de los Ciclos Formativos masculinizados y feminizados en Cantabria

OpenAIRE

Mantecón Pelayo, Eva María

2017-01-01

RESUMEN: En un momento de grandes avances en materia de igualdad de género y laboral, en algunas familias profesionales de la Formación Profesional se mantiene una acusada segregación por sexos, mucho mayor que la de los estudios universitarios correspondientes a las mismas áreas temáticas. Investigamos en este estudio las posibles razones de esta diferencia preguntando a los protagonistas: el alumnado y profesorado de dos Ciclos formativos de las familias de Electricidad y Electrónica (muy m...

Estrategias de aprendizaje en la comprensión lectora en estudiantes del sexto ciclo en una institución educativa, San Isidro – 2016

OpenAIRE

Cusihualpa Torres, Julia Isabel

2017-01-01

La investigación titulada “Estrategias de aprendizaje en la comprensión lectora en estudiantes del sexto ciclo en una institución educativa San Isidro - 2016”, tuvo como objetivo comprobar que las estrategias de aprendizaje influyen significativamente en el desarrollo de capacidades de comprensión lectora de estudiante del nivel secundaria. El tipo de investigación fue aplicada con diseño cuasi experimental. La muestra fue de tipo no probabilística y compuesta por 60 estudia...