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Sample records for carnot cycle

  1. Reversible Carnot cycle outside a black hole

    International Nuclear Information System (INIS)

    Xi-Hao, Deng; Si-Jie, Gao

    2009-01-01

    A Carnot cycle outside a Schwarzschild black hole is investigated in detail. We propose a reversible Carnot cycle with a black hole being the cold reservoir. In our model, a Carnot engine operates between a hot reservoir with temperature T 1 and a black hole with Hawking temperature T H . By naturally extending the ordinary Carnot cycle to the black hole system, we show that the thermal efficiency for a reversible process can reach the maximal efficiency 1 – T H /T 1 . Consequently, black holes can be used to determine the thermodynamic temperature by means of the Carnot cycle. The role of the atmosphere around the black hole is discussed. We show that the thermal atmosphere provides a necessary mechanism to make the process reversible. (general)

  2. Thermodynamic performance analysis of sequential Carnot cycles using heat sources with finite heat capacity

    International Nuclear Information System (INIS)

    Park, Hansaem; Kim, Min Soo

    2014-01-01

    The maximum efficiency of a heat engine is able to be estimated by using a Carnot cycle. Even though, in terms of efficiency, the Carnot cycle performs the role of reference very well, its application is limited to the case of infinite heat reservoirs, which is not that realistic. Moreover, considering that one of the recent key issues is to produce maximum work from low temperature and finite heat sources, which are called renewable energy sources, more advanced theoretical cycles, which can present a new standard, and the research about them are necessary. Therefore, in this paper, a sequential Carnot cycle, where multiple Carnot cycles are connected in parallel, is studied. The cycle adopts a finite heat source, which has a certain initial temperature and heat capacity, and an infinite heat sink, which is assumed to be ambient air. Heat transfer processes in the cycle occur with the temperature difference between a heat reservoir and a cycle. In order to resolve the heat transfer rate in those processes, the product of an overall heat transfer coefficient and a heat transfer area is introduced. Using these conditions, the performance of a sequential Carnot cycle is analytically calculated. Furthermore, as the efforts for enhancing the work of the cycle, the optimization research is also conducted with numerical calculation. - Highlights: • Modified sequential Carnot cycles are proposed for evaluating low grade heat sources. • Performance of sequential Carnot cycles is calculated analytically. • Optimization study for the cycle is conducted with numerical solver. • Maximum work from a heat source under a certain condition is obtained by equations

  3. Carnot cycle for magnetic materials: The role of hysteresis

    International Nuclear Information System (INIS)

    Sasso, Carlo P.; Basso, Vittorio; LoBue, Martino; Bertotti, Giorgio

    2006-01-01

    The role of hysteresis in a refrigeration thermodynamic cycle involving ferromagnetic materials is discussed. A model allowing to calculate magnetization, entropy and entropy production in systems with hysteresis is used to compute a non-ideal Carnot cycle performed on a ferromagnetic material

  4. Study on optimal performance and working temperatures of endoreversible forward and reverse Carnot cycles

    Energy Technology Data Exchange (ETDEWEB)

    Chen, W.Z.; Sun, F.R.; Cheng, S.M.; Chen, L.G. [Huazhong Univ. of Sceince and Technology, Wuhan (China). Dept. of Power Engineering

    1995-12-01

    The connection between the expressions of optimization performances of Carnot heat engines, refrigerators and heat pumps, which operate subject to irreversible heat flow, is studied. We consider the endoreversible forward and reverse. Carnot cycles and analyse the expressions which relate efficiency, refrigeration and heating coefficients to power, refrigeration and heating rates, respectively. It is found and proved that when one of the optimal relations is derived the others are also determined, and give the unified formulation of the related optimal working temperatures of the forward and reverse Carnot cycles by isentropic temperature ratio exponent. Finally, several new optimal performance relations are derived for forward and reverse Carnot cycles under nonlinear heat transfer, and some major results in the references are easily deduced and unified in this paper. (author)

  5. Real-Time Numerical Simulation of the Carnot Cycle

    International Nuclear Information System (INIS)

    Hurkala, J.; Gall, M.; Kutner, R.; Maciejczyk, M.

    2005-01-01

    We developed a highly interactive, multi-windows Java applet which made it possible to simulate and visualize within any platform and internet the Carnot cycle (or engine) in a real-time computer experiment. We extended our previous model and algorithm to simulate not only the heat flow but also the macroscopic movement of the piston. since in reality it is impossible to construct a reversible Carnot engine, the question arises whether it is possible to simulate it at least in a numerical experiment? The positive answer to this question which we found is related to our model and algorithm which make it possible to omit the many-body problem arising when many gas particles simultaneously interact with the mobile piston. As usually the considerations of phenomenomenological thermodynamics began with a study of the basic properties of heat engines hence our approach, beside intrinsic physical significance, is also important from the educational, technological and even environmental points of view. (author)

  6. Real-time numerical simulation of the Carnot cycle

    International Nuclear Information System (INIS)

    Hurkala, J; Gall, M; Kutner, R; Maciejczyk, M

    2005-01-01

    We developed a highly interactive, multi-windows Java applet which made it possible to simulate and visualize within any platform and internet the Carnot cycle (or engine) in a real-time computer experiment. We extended our previous model and algorithm (Galant et al 2003 Heat Transfer, Newton's Law of Cooling and the Law of Entropy Increase Simulated by the Real-Time Computer Experiments in Java (Lecture Notes in Computer Science vol 2657) pp 45-53, Gall and Kutner 2005 Molecular mechanisms of heat transfer: Debye relaxation versus power-law Physica A 352 347-78) to simulate not only the heat flow but also the macroscopic movement of the piston. Since in reality it is impossible to construct a reversible Carnot engine, the question arises whether it is possible to simulate it at least in a numerical experiment? The positive answer to this question which we found is related to our model and algorithm which make it possible to omit the many-body problem arising when many gas particles simultaneously interact with the mobile piston. As usual, the considerations of phenomenological thermodynamics began with a study of the basic properties of heat engines, hence our approach, besides intrinsic physical significance, is also important from the educational, technological and even environmental points of view

  7. A novel Carnot-based cycle for ocean thermal energy conversion

    International Nuclear Information System (INIS)

    Semmari, Hamza; Stitou, Driss; Mauran, Sylvain

    2012-01-01

    A thermodynamic engine cycle can be implemented by exploiting the temperature difference existing between the warm surface seawater and cold deep seawater. It employs a working fluid that evaporates by warm seawater, produces work in an expander device, such as a gas turbine and finally condenses by cold deep seawater. A new Carnot-based cycle for OTEC applications, called CAPILI cycle is presented. In this new engine cycle, work is produced by the movement of an inert liquid through a hydraulic turbine. This inert liquid characterized by a very low saturation pressure and immiscibility with the working fluid, acts as a liquid piston that moves alternately between two insulated cylinders. The insulated cylinders are connected alternately to an evaporator and a condenser, each of them operates at different pressure and temperature levels. A performance study which consists in a steady state energy balance is realised first to select the most suitable working fluid for this specific application. It was found that the best fluid is the HFC refrigerant R134a. A dynamic modelling based on the concept of equivalent Gibbs system is carried out to appreciate the dynamic behaviour and the performances of this new thermal conversion process. -- Highlights: ► A novel Carnot-based cycle operating with a liquid piston is investigated for OTEC application. ► The most suitable working fluid giving the best performances is found to be the HFC R134a. ► The performances of this new thermal process are evaluated using a dynamic modelling. ► A thermal efficiency of 1.9% can be obtained by exploiting seawater temperature difference of 20 °C. ► A net cycle efficiency of 1.2% is achieved considering a net to gross power production ratio of 61%.

  8. Are you sure, Mr. Carnot?

    International Nuclear Information System (INIS)

    Liszka, John.

    1992-01-01

    The author discusses the importance and historical background of the second law of thermodynamics as applied to power generation. He considers a device called an 'adiabatic separator' as not having been envisioned by Carnot, and possibly producing a spontaneous temperature difference, thereby violating the second law; however, he does not consider that the Carnot cycle is not the sole theoretical basis of the second law, but only a didactic exemplification thereof; moreover, the device considered by the author will not work continuously without an external supply of energy

  9. The Carnot cycle and the teaching of thermodynamics: a historical approach

    Science.gov (United States)

    Laranjeiras, Cássio C.; Portela, Sebastião I. C.

    2016-09-01

    The Carnot cycle is a topic that is traditionally present in introductory physics courses dedicated to the teaching of thermodynamics, playing an essential role in introducing the concept of Entropy and the consequent formulation of the second Law. Its effective understanding and contribution to the development of thermodynamics is often hindered, however. Among other things, this is the result of a pragmatic approach, which usually limits itself to presenting the isotherms and adiabatic curves in a P-V diagram and is totally disconnected from the historical fundamentals of Heat Theory. The purpose of this paper is to reveal the potential of an approach to the subject that recovers the historical and social dimensions of scientific knowledge, and to promote reflections about the nature of science (NOS).

  10. Nonlinear Thermodynamic Analysis and Optimization of a Carnot Engine Cycle

    Directory of Open Access Journals (Sweden)

    Michel Feidt

    2016-06-01

    Full Text Available As part of the efforts to unify the various branches of Irreversible Thermodynamics, the proposed work reconsiders the approach of the Carnot engine taking into account the finite physical dimensions (heat transfer conductances and the finite speed of the piston. The models introduce the irreversibility of the engine by two methods involving different constraints. The first method introduces the irreversibility by a so-called irreversibility ratio in the entropy balance applied to the cycle, while in the second method it is emphasized by the entropy generation rate. Various forms of heat transfer laws are analyzed, but most of the results are given for the case of the linear law. Also, individual cases are studied and reported in order to provide a simple analytical form of the results. The engine model developed allowed a formal optimization using the calculus of variations.

  11. Achieving the classical Carnot efficiency in a strongly coupled quantum heat engine

    Science.gov (United States)

    Xu, Y. Y.; Chen, B.; Liu, J.

    2018-02-01

    Generally, the efficiency of a heat engine strongly coupled with a heat bath is less than the classical Carnot efficiency. Through a model-independent method, we show that the classical Carnot efficiency is achieved in a strongly coupled quantum heat engine. First, we present the first law of quantum thermodynamics in strong coupling. Then, we show how to achieve the Carnot cycle and the classical Carnot efficiency at strong coupling. We find that this classical Carnot efficiency stems from the fact that the heat released in a nonequilibrium process is balanced by the absorbed heat. We also analyze the restrictions in the achievement of the Carnot cycle. The first restriction is that there must be two corresponding intervals of the controllable parameter in which the corresponding entropies of the work substance at the hot and cold temperatures are equal, and the second is that the entropy of the initial and final states in a nonequilibrium process must be equal. Through these restrictions, we obtain the positive work conditions, including the usual one in which the hot temperature should be higher than the cold, and a new one in which there must be an entropy interval at the hot temperature overlapping that at the cold. We demonstrate our result through a paradigmatic model—a two-level system in which a work substance strongly interacts with a heat bath. In this model, we find that the efficiency may abruptly decrease to zero due to the first restriction, and that the second restriction results in the control scheme becoming complex.

  12. Carnot to Clausius: Caloric to Entropy

    Science.gov (United States)

    Newburgh, Ronald

    2009-01-01

    This paper discusses how the Carnot engine led to the formulation of the second law of thermodynamics and entropy. The operation of the engine is analysed both in terms of heat as the caloric fluid and heat as a form of energy. A keystone of Carnot's thinking was the absolute conservation of caloric. Although the Carnot analysis was partly…

  13. Quantum-Carnot engine for particle confined to 2D symmetric potential well

    International Nuclear Information System (INIS)

    Belfaqih, Idrus Husin; Sutantyo, Trengginas Eka Putra; Prayitno, T. B.; Sulaksono, Anto

    2015-01-01

    Carnot model of heat engine is the most efficient cycle consisting of isothermal and adiabatic processes which are reversible. Although ideal gas usually used as a working fluid in the Carnot engine, Bender used quantum particle confined in 1D potential well as a working fluid. In this paper, by following Bender we generalize the situation to 2D symmetric potential well. The efficiency is express as the ratio of the initial length of the system to the final length of the compressed system. The result then is shown that for the same ratio, 2D potential well is more efficient than 1D potential well

  14. Quantum-Carnot engine for particle confined to 2D symmetric potential well

    Energy Technology Data Exchange (ETDEWEB)

    Belfaqih, Idrus Husin, E-mail: idrushusin21@gmail.com; Sutantyo, Trengginas Eka Putra, E-mail: trengginas.eka@gmail.com; Prayitno, T. B., E-mail: teguh-budi@unj.ac.id [Department of Physics, Universitas Negeri Jakarta, Jl. Pemuda Rawamangun, Jakarta Timur, 13220 (Indonesia); Sulaksono, Anto, E-mail: anto.sulaksono@sci.ui.ac.id [Department of Physics, Universitas Indonesia, Depok, Jawa Barat, 164242 (Indonesia)

    2015-09-30

    Carnot model of heat engine is the most efficient cycle consisting of isothermal and adiabatic processes which are reversible. Although ideal gas usually used as a working fluid in the Carnot engine, Bender used quantum particle confined in 1D potential well as a working fluid. In this paper, by following Bender we generalize the situation to 2D symmetric potential well. The efficiency is express as the ratio of the initial length of the system to the final length of the compressed system. The result then is shown that for the same ratio, 2D potential well is more efficient than 1D potential well.

  15. A note on the use of the temperature–entropy diagram in the proof of the second carnot theorem

    International Nuclear Information System (INIS)

    Morad, M R; Momeni, F

    2014-01-01

    A general graphical proof for the second Carnot principle is presented using the temperature–entropy diagram. This proof is simple and is independent of the proof of the first Carnot principle. The Carnot relation for thermal efficiency is also obtained simultaneously for all totally reversible heat engines between the same two reservoirs. The concept of reversibility in heat transfers and the role of environments in heat engine cycles will be further clarified and could be better understood using the proof presented here, which will be useful both for teaching and performing research in thermodynamics. (letters and comments)

  16. Analysis of a microscale 'Saturation Phase-change Internal Carnot Engine'

    International Nuclear Information System (INIS)

    Lurie, Eli; Kribus, Abraham

    2010-01-01

    A micro heat engine, based on a cavity filled with a stationary working fluid under liquid-vapor saturation conditions and encapsulated by two membranes, is described and analyzed. This engine design is easy to produce using MEMS technologies and is operated with external heating and cooling. The motion of the membranes is controlled such that the internal pressure and temperature are constant during the heat addition and removal processes, and thus the fluid executes a true internal Carnot cycle. A model of this Saturation Phase-change Internal Carnot Engine (SPICE) was developed including thermodynamic, mechanical and heat transfer aspects. The efficiency and maximum power of the engine are derived. The maximum power point is fixed in a three-parameter space, and operation at this point leads to maximum power density that scales with the inverse square of the engine dimension. Inclusion of the finite heat capacity of the engine wall leads to a strong dependence of performance on engine frequency, and the existence of an optimal frequency. Effects of transient reverse heat flow, and 'parasitic heat' that does not participate in the thermodynamic cycle are observed.

  17. The universality of the Carnot theorem

    International Nuclear Information System (INIS)

    Gonzalez-Ayala, Julian; Angulo-Brown, F

    2013-01-01

    It is common in many thermodynamics textbooks to illustrate the Carnot theorem through the use of diverse state equations for gases, paramagnets, and other simple thermodynamic systems. As is well known, the universality of the Carnot efficiency is easily demonstrated in a temperature–entropy diagram, which means that η C is independent of the working substance. In this paper we remark that the universality of the Carnot theorem goes beyond conventional state equations, and is fulfilled by gas state equations that do not correspond to an ideal gas in the dilution limit, namely V → ∞. Some of these unconventional state equations have certain thermodynamic ‘anomalies’ that nonetheless do not forbid them from obeying the Carnot theorem. We discuss how this very general behaviour arises from Maxwell relations, which are connected with a geometrical property expressed through preserving area transformations. A rule is proposed to calculate the Maxwell relations associated with a thermodynamic system by using the preserving area relationships. In this way it is possible to calculate the number of possible preserving area mappings by giving the number of possible Jacobian identities between all pairs of thermodynamic variables included in the corresponding Gibbs equation. This paper is intended for undergraduates and specialists in thermodynamics and related areas. (paper)

  18. Energy and entropy analysis of closed adiabatic expansion based trilateral cycles

    International Nuclear Information System (INIS)

    Garcia, Ramon Ferreiro; Carril, Jose Carbia; Gomez, Javier Romero; Gomez, Manuel Romero

    2016-01-01

    Highlights: • The adiabatic expansion based TC surpass Carnot factor at low temperatures. • The fact of surpassing Carnot factor doesn’t violate the 2nd law. • An entropy analysis is applied to verify the fulfilment of the second law. • Correction of the exergy transfer associated with heat transferred to a cycle. - Abstract: A vast amount of heat energy is available at low cost within the range of medium and low temperatures. Existing thermal cycles cannot make efficient use of such available low grade heat because they are mainly based on conventional organic Rankine cycles which are limited by Carnot constraints. However, recent developments related to the performance of thermal cycles composed of closed processes have led to the exceeding of the Carnot factor. Consequently, once the viability of closed process based thermal cycles that surpass the Carnot factor operating at low and medium temperatures is globally accepted, research work will aim at looking into the consequences that lead from surpassing the Carnot factor while fulfilling the 2nd law, its impact on the 2nd law efficiency definition as well as the impact on the exergy transfer from thermal power sources to any heat consumer, including thermal cycles. The methodology used to meet the proposed objectives involves the analysis of energy and entropy on trilateral closed process based thermal cycles. Thus, such energy and entropy analysis is carried out upon non-condensing mode trilateral thermal cycles (TCs) characterised by the conversion of low grade heat into mechanical work undergoing closed adiabatic path functions: isochoric heat absorption, adiabatic heat to mechanical work conversion and isobaric heat rejection. Firstly, cycle energy analysis is performed to determine the range of some relevant cycle parameters, such as the operating temperatures and their associated pressures, entropies, internal energies and specific volumes. In this way, the ranges of temperatures within which

  19. Analysis of a microscale 'Saturation Phase-change Internal Carnot Engine'

    Energy Technology Data Exchange (ETDEWEB)

    Lurie, Eli [School of Mechanical Engineering, Tel Aviv University, Tel Aviv 69978 (Israel); Kribus, Abraham, E-mail: kribus@eng.tau.ac.i [School of Mechanical Engineering, Tel Aviv University, Tel Aviv 69978 (Israel)

    2010-06-15

    A micro heat engine, based on a cavity filled with a stationary working fluid under liquid-vapor saturation conditions and encapsulated by two membranes, is described and analyzed. This engine design is easy to produce using MEMS technologies and is operated with external heating and cooling. The motion of the membranes is controlled such that the internal pressure and temperature are constant during the heat addition and removal processes, and thus the fluid executes a true internal Carnot cycle. A model of this Saturation Phase-change Internal Carnot Engine (SPICE) was developed including thermodynamic, mechanical and heat transfer aspects. The efficiency and maximum power of the engine are derived. The maximum power point is fixed in a three-parameter space, and operation at this point leads to maximum power density that scales with the inverse square of the engine dimension. Inclusion of the finite heat capacity of the engine wall leads to a strong dependence of performance on engine frequency, and the existence of an optimal frequency. Effects of transient reverse heat flow, and 'parasitic heat' that does not participate in the thermodynamic cycle are observed.

  20. Ecological optimization of an irreversible quantum Carnot heat engine with spin-1/2 systems

    International Nuclear Information System (INIS)

    Liu Xiaowei; Chen Lingen; Wu Feng; Sun Fengrui

    2010-01-01

    A model of a quantum heat engine with heat resistance, internal irreversibility and heat leakage and many non-interacting spin-1/2 systems is established in this paper. The quantum heat engine cycle is composed of two isothermal processes and two irreversible adiabatic processes and is referred to as a spin quantum Carnot heat engine. Based on the quantum master equation and the semi-group approach, equations of some important performance parameters, such as power output, efficiency, entropy generation rate and ecological function (a criterion representing the optimal compromise between exergy output rate and exergy loss rate), for the irreversible spin quantum Carnot heat engine are derived. The optimal ecological performance of the heat engine in the classical limit is analyzed with numerical examples. The effects of internal irreversibility and heat leakage on ecological performance are discussed in detail.

  1. Reflexões sobre a contribuição da Carnot à primeira lei da termodinâmica Reflections on the contribution of Carnot to the first law of thermodynamics

    Directory of Open Access Journals (Sweden)

    Cássius K. Nascimento

    2004-06-01

    Full Text Available The classical interpretations of Nicolas Léonard Sadi Carnot on some physical principles involved in the operation of heat engines were fundamental to the development and formulation of the Second Law of Thermodynamics. Moreover, an accurate historical survey clearly reveals that Carnot was, by that time, also well aware about some new concepts, which were further worked out by other scientists to lead to what was, some time later, known as the mechanical equivalent of heat and the conservation of energy. Benoit Paul Émile Clapeyron recognized these original concepts in the first of Carnot´s monographs, published in 1824, but no explicit citation is found in any post-Carnot classical texts dealing with the First Law of Thermodynamics, including those by Julius Robert Mayer, James Prescott Joule and Hermann Ludwig Ferdinand von Helmholtz. The main objective of the present work is to point out some historical evidences of the pioneering contribution of Carnot to the modern concept of the First Law of Thermodynamics.

  2. A New Simple Approach for Entropy and Carnot Theorem

    International Nuclear Information System (INIS)

    Veliev, E. V.

    2004-01-01

    Entropy and Carnot theorem occupy central place in the typical Thermodynamics courses at the university level. In this work, we suggest a new simple approach for introducing the concept of entropy. Using simple procedure in TV plane, we proved that for reversible processes ∫dQ/T=0 and it is sufficient to define entropy. And also, using reversible processes in TS plane, we give an alternative simple proof for Carnot theorem

  3. Optimum heat power cycles for specified boundary conditions

    International Nuclear Information System (INIS)

    Ibrahim, O.M.; Klein, S.A.; Mitchell, J.W.

    1991-01-01

    In this paper optimization of the power output of Carnot and closed Brayton cycles is considered for both finite and infinite thermal capacitance rates of the external fluid streams. The method of Lagrange multipliers is used to solve for working fluid temperatures that yield maximum power. Analytical expressions for the maximum power and the cycle efficiency at maximum power are obtained. A comparison of the maximum power from the two cycles for the same boundary conditions, i.e., the same heat source/sink inlet temperatures, thermal capacitance rates, and heat exchanger conductances, shows that the Brayton cycle can produce more power than the Carnot cycle. This comparison illustrates that cycles exist that can produce more power than the Carnot cycle. The optimum heat power cycle, which will provide the upper limit of power obtained from any thermodynamic cycle for specified boundary conditions and heat exchanger conductances is considered. The optimum heat power cycle is identified by optimizing the sum of the power output from a sequence of Carnot cycles. The shape of the optimum heat power cycle, the power output, and corresponding efficiency are presented. The efficiency at maximum power of all cycles investigated in this study is found to be equal to (or well approximated by) η = 1 - sq. root T L.in /φT H.in where φ is a factor relating the entropy changes during heat rejection and heat addition

  4. Reversible and irreversible heat engine and refrigerator cycles

    Science.gov (United States)

    Leff, Harvey S.

    2018-05-01

    Although no reversible thermodynamic cycles exist in nature, nearly all cycles covered in textbooks are reversible. This is a review, clarification, and extension of results and concepts for quasistatic, reversible and irreversible processes and cycles, intended primarily for teachers and students. Distinctions between the latter process types are explained, with emphasis on clockwise (CW) and counterclockwise (CCW) cycles. Specific examples of each are examined, including Carnot, Kelvin and Stirling cycles. For the Stirling cycle, potentially useful task-specific efficiency measures are proposed and illustrated. Whether a cycle behaves as a traditional refrigerator or heat engine can depend on whether it is reversible or irreversible. Reversible and irreversible-quasistatic CW cycles both satisfy Carnot's inequality for thermal efficiency, η ≤ η C a r n o t . Irreversible CCW cycles with two reservoirs satisfy the coefficient of performance inequality K ≤ K C a r n o t . However, an arbitrary reversible cycle satisfies K ≥ K C a r n o t when compared with a reversible Carnot cycle operating between its maximum and minimum temperatures, a potentially counterintuitive result.

  5. Free Energy and Internal Combustion Engine Cycles

    OpenAIRE

    Harris, William D.

    2012-01-01

    The performance of one type (Carnot) of Internal Combustion Engine (ICE) cycle is analyzed within the framework of thermodynamic free energies. ICE performance is different from that of an External Combustion Engine (ECE) which is dictated by Carnot's rule.

  6. Quantum-Carnot engine for particle confined to cubic potential

    Energy Technology Data Exchange (ETDEWEB)

    Sutantyo, Trengginas Eka P., E-mail: trengginas.eka@gmail.com; Belfaqih, Idrus H., E-mail: idrushusin21@gmail.com; Prayitno, T. B., E-mail: teguh-budi@unj.ac.id [Department of Physics, State University of Jakarta, Jl. Pemuda No.10, Rawamangun, Jakarta Timur 13220 (Indonesia)

    2015-09-30

    Carnot cycle consists of isothermal and adiabatic processes which are reversible. Using analogy in quantum mechanics, these processes can be well explained by replacing variables in classical process with a quantum system. Quantum system which is shown in this paper is a particle that moves under the influence of a cubic potential which is restricted only to the state of the two energy levels. At the end, the efficiency of the system is shown as a function of the width ratio between the initial conditions and the farthest wall while expanding. Furthermore, the system efficiency will be considered 1D and 2D cases. The providing efficiencies are different due to the influence of the degeneration of energy and the degrees of freedom of the system.

  7. Quantum-Carnot engine for particle confined to cubic potential

    International Nuclear Information System (INIS)

    Sutantyo, Trengginas Eka P.; Belfaqih, Idrus H.; Prayitno, T. B.

    2015-01-01

    Carnot cycle consists of isothermal and adiabatic processes which are reversible. Using analogy in quantum mechanics, these processes can be well explained by replacing variables in classical process with a quantum system. Quantum system which is shown in this paper is a particle that moves under the influence of a cubic potential which is restricted only to the state of the two energy levels. At the end, the efficiency of the system is shown as a function of the width ratio between the initial conditions and the farthest wall while expanding. Furthermore, the system efficiency will be considered 1D and 2D cases. The providing efficiencies are different due to the influence of the degeneration of energy and the degrees of freedom of the system

  8. IFPEN Transports Energy Carnot Institute. Annual report 2016. Innovating mobility

    International Nuclear Information System (INIS)

    2017-01-01

    Under the authority of IFP Energies nouvelles, the IFPEN Transports Energie Carnot Institute develops efficient, clean and sustainable technological innovations in the fields of power-train and propulsion systems, energy sectors and industrial thermal processes with CO_2 capture. IFPEN Transports Energie Carnot Institute is a R and D center serving industry, leader in the fields of transport and energy: - Innovative solutions to address technological challenges and market needs (high-efficiency, low-emission power-trains, power-train electrification, energy optimization and onboard control, alternative fuels with low CO_2 emissions, energy generation based on chemical looping combustion); - High-performance experimental resources and digital tools resulting in innovations with reduced costs and development times; - A proactive industrial protection policy; - Support for industrial sectors, covering a very broad range of technological readiness levels; - Transfer of R and D results via joint product development with licensing out operations, strategic partnerships and collaborative research agreements; - An innovation support policy, aimed particularly at micro-companies, SMEs and intermediate-sized companies. IFPEN Transports Energie Carnot Institute has close ties with industry: from micro-companies, SMEs and intermediate-sized companies to major industrial groups; A strong commitment within competitiveness clusters (Mov'eo, LUTB, Systematic, Astech, etc.); A leadership of the automobile sector and the Transport Alliance within the Carnot Institutes; A synergy with networks of academic partners and R and D laboratories with an international influence

  9. Modern Thermodynamics Based on the Extended Carnot Theorem

    CERN Document Server

    Wang, Jitao

    2012-01-01

    "Modern Thermodynamics- Based on the Extended Carnot Theorem" provides comprehensive definitions and mathematical expressions of both classical and modern thermodynamics. The goal is to develop the fundamental theory on an extended Carnot theorem without incorporating any extraneous assumptions. In particular, it offers a fundamental thermodynamic and calculational methodology for the synthesis of low-pressure diamonds. It also discusses many "abnormal phenomena", such as spiral reactions, cyclic reactions, chemical oscillations, low-pressure carat-size diamond growth, biological systems, and more. The book is intended for chemists and physicists working in thermodynamics, chemical thermodynamics, phase diagrams, biochemistry and complex systems, as well as graduate students in these fields. Jitao Wang is a professor emeritus at Fudan University, Shanghai, China.

  10. Modern thermodynamics. Based on the extended Carnot theorem

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jitao [Fudan Univ., Shanghai (China). Microelectronics Dept.

    2011-07-01

    ''Modern Thermodynamics- Based on the Extended Carnot Theorem'' provides comprehensive definitions and mathematical expressions of both classical and modern thermodynamics. The goal is to develop the fundamental theory on an extended Carnot theorem without incorporating any extraneous assumptions. In particular, it offers a fundamental thermodynamic and calculational methodology for the synthesis of low-pressure diamonds. It also discusses many ''abnormal phenomena'', such as spiral reactions, cyclic reactions, chemical oscillations, low-pressure carat-size diamond growth, biological systems, and more. The book is intended for chemists and physicists working in thermodynamics, chemical thermodynamics, phase diagrams, biochemistry and complex systems, as well as graduate students in these fields. Jitao Wang is a professor emeritus at Fudan University, Shanghai, China. (orig.)

  11. PRI 8.1: CARNOT. Analysis and research community of the new orientations of the thermodynamics. Activity report june 2002/ june 2004; PRI 8.1: CARNOT. Communaute d'Analyse et de Recherche des Nouvelles Orientations de la Thermodynamique. Rapport d'activite juin 2002/ juin 2004

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-07-01

    This progress report takes stock on the CARNOT project. This project aims to standardize the different approaches or identify the application fields of each thermodynamical methodology. The cycles analysis and more generally thermodynamical machines (design, energy efficiency, new energy utilization concepts). The environmental impact is also an important topic of the project. (A.L.B.)

  12. On the proof of the first Carnot theorem in thermodynamics

    International Nuclear Information System (INIS)

    Morad, M R; Momeni, F

    2013-01-01

    The proof of the first Carnot theorem in classical thermodynamics is revisited in this study. The underlying conditions of a general proof of this principle presented by Senft (1978 Phys. Educ. 13 35–37) are explored and discussed. These conditions are analysed in more detail using a physical description of heat and work to present a simpler proof of the first principle prior to using the violation of the second law of thermodynamics. Finally, a new simple proof is also presented based on Gibbs relation. This discussion will benefit the teaching of classical thermodynamics and promote better understanding of the proof of the first Carnot theorem in general form. (paper)

  13. Layer potentials, Kac's problem, and refined Hardy inequality on homogeneous Carnot groups

    OpenAIRE

    Ruzhansky, Michael; Suragan, Durvudkhan

    2017-01-01

    We propose the analogues of boundary layer potentials for the sub-Laplacian on homogeneous Carnot groups/stratified Lie groups and prove continuity results for them. In particular, we show continuity of the single layer potential and establish the Plemelj type jump relations for the double layer potential. We prove sub-Laplacian adapted versions of the Stokes theorem as well as of Green's first and second formulae on homogeneous Carnot groups. Several applications to boundary value problems a...

  14. Carnot efficiency at divergent power output

    Science.gov (United States)

    Polettini, Matteo; Esposito, Massimiliano

    2017-05-01

    The widely debated feasibility of thermodynamic machines achieving Carnot efficiency at finite power has been convincingly dismissed. Yet, the common wisdom that efficiency can only be optimal in the limit of infinitely slow processes overlooks the dual scenario of infinitely fast processes. We corroborate that efficient engines at divergent power output are not theoretically impossible, framing our claims within the theory of Stochastic Thermodynamics. We inspect the case of an electronic quantum dot coupled to three particle reservoirs to illustrate the physical rationale.

  15. Lazare and Sadi Carnot a scientific and filial relationship

    CERN Document Server

    Gillispie, Charles Coulston

    2014-01-01

    Lazare Carnot was the unique example in the history of science of someone who inadvertently owed the scientific recognition he eventually achieved to earlier political prominence. He and his son Sadi produced work that derived from their training as engineers and went largely unnoticed by physicists for a generation or more, even though their respective work introduced concepts that proved fundamental when taken up later by other hands. There was, moreover, a filial as well as substantive relation between the work of father and son. Sadi applied to the functioning of heat engines the analysis that his father had developed in his study of the operation of ordinary machines. Specifically, Sadi's idea of a reversible process originated in the use his father made of geometric motions in the analysis of machines in general. This unique book shows how the two Carnots influenced each other in their work in the fields of mechanics and thermodynamics, and how future generations of scientists have further benefited f...

  16. Layer potentials, Green's formulae, Kac's problem, and refined Hardy inequality on homogeneous Carnot groups

    OpenAIRE

    Ruzhansky, Michael; Suragan, Durvudkhan

    2015-01-01

    We propose the analogues of boundary layer potentials for the sub-Laplacian on homogeneous Carnot groups/stratified Lie groups and prove continuity results for them. In particular, we show continuity of the single layer potential and establish the Plemelj type jump relations for the double layer potential. We prove sub-Laplacian adapted versions of the Stokes theorem as well as of Green's first and second formulae on homogeneous Carnot groups. Several applications to boundary value problems a...

  17. Two Quantum Polytropic Cycles

    Science.gov (United States)

    Arias-Hernández, L. A.; Morales-Serrano, A. F.

    2002-11-01

    In this work we follow the Bender et al paper [1] to study the quantum analogues of the Stirling and Ericsson polytropic cycles. In the context of the classical thermodynamics, the Stirling and Ericsson cycles correspond to reversible heat engines with two isothermal processes joined by two polytropic branches which occur in a device called regenerator. If this device is an ideal one, the efficiency of these cycles is the Carnot efficiency. Here, we introduce the quantum analogues of the Stirling and Ericsson cycles, the first one based on a double square potential well with a finite potential barrier, since in this system the tunnel effect could be the analogue to the regeneration classical process, therefore the isochoric quantum branches would really correspond to an internal energy storage, and the last one with an unknown system where the isobaric quantum processes don't induce changes in its quantum state. With these systems the quantum engines have cycles consisting of polytropic and isothermal quantum processes analogues to the corresponding classical processes. We show that in both cases the quantum cycles have an efficiency given by ηCQM = 1 - EC/EH, which is the same expression for the quantum analogue of the Carnot cycle studied by Bender.

  18. Carnot type magnetic refrigeration below 4.2 K - computer simulation

    International Nuclear Information System (INIS)

    Hashimoto, T.; Numazawa, T.; Maro, T.

    1984-01-01

    Cooling devices based on a utilization of the Carnot type magnetic refrigeration cycle are usually selected for the temperature range from 20 K to 1.8 K. However, the refrigeration power in the case of such devices is frequently limited by the heat transfer coefficient between the heat source and the magnetic working substance. Thus, in a magnetic refrigerator studied by Delpuech et al. (1981), the refrigeration power is mainly restricted by the heat transfer coefficient in the isothermal magnetization process at 4.2 K. The present investigation is concerned with the development of a method for achieving high refrigeration power on the basis of a study utilizing computer simulation. One of two methods considered for enhancing refrigeration power is related to the change in the magnetic field, while the other method involves an enlargement of the effective area of gadolinium-gallium-garnet (GGG) with the aid of deep grooves in the surface. 6 references

  19. Variations on the Zilch Cycle

    Science.gov (United States)

    Binder, P.-M.; Tanoue, C. K. S.

    2013-01-01

    Thermo dynamic cycles in introductory physics courses are usually made up from a small number of permutations of isothermal, adiabatic, and constant-pressure and volume quasistatic strokes, with the working fluid usually being an ideal gas. Among them we find the Carnot, Stirling, Otto, Diesel, and Joule-Brayton cycles; in more advanced courses,…

  20. Ecological optimization for generalized irreversible Carnot refrigerators

    International Nuclear Information System (INIS)

    Chen Lingen; Zhu Xiaoqin; Sun Fengrui; Wu Chih

    2005-01-01

    The optimal ecological performance of a Newton's law generalized irreversible Carnot refrigerator with the losses of heat resistance, heat leakage and internal irreversibility is derived by taking an ecological optimization criterion as the objective, which consists of maximizing a function representing the best compromise between the exergy output rate and exergy loss rate (entropy production rate) of the refrigerator. Numerical examples are given to show the effects of heat leakage and internal irreversibility on the optimal performance of generalized irreversible refrigerators

  1. Local Monotonicity and Isoperimetric Inequality on Hypersurfaces in Carnot groups

    Directory of Open Access Journals (Sweden)

    Francesco Paolo Montefalcone

    2010-12-01

    Full Text Available Let G be a k-step Carnot group of homogeneous dimension Q. Later on we shall present some of the results recently obtained in [32] and, in particular, an intrinsic isoperimetric inequality for a C2-smooth compact hypersurface S with boundary @S. We stress that S and @S are endowed with the homogeneous measures n????1 H and n????2 H , respectively, which are actually equivalent to the intrinsic (Q - 1-dimensional and (Q - 2-dimensional Hausdor measures with respect to a given homogeneous metric % on G. This result generalizes a classical inequality, involving the mean curvature of the hypersurface, proven by Michael and Simon [29] and Allard [1], independently. One may also deduce some related Sobolev-type inequalities. The strategy of the proof is inspired by the classical one and will be discussed at the rst section. After reminding some preliminary notions about Carnot groups, we shall begin by proving a linear isoperimetric inequality. The second step is a local monotonicity formula. Then we may achieve the proof by a covering argument.We stress however that there are many dierences, due to our non-Euclidean setting.Some of the tools developed ad hoc are, in order, a \\blow-up" theorem, which holds true also for characteristic points, and a smooth Coarea Formula for the HS-gradient. Other tools are the horizontal integration by parts formula and the 1st variation formula for the H-perimeter n????1H already developed in [30, 31] and then generalized to hypersurfaces having non-empty characteristic set in [32]. These results can be useful in the study of minimal and constant horizontal mean curvature hypersurfaces in Carnot groups.

  2. Breaking the Carnot limit without violating the second law: A thermodynamic analysis of off-resonant quantum light generation

    Science.gov (United States)

    Boukobza, E.; Ritsch, H.

    2013-06-01

    The Carnot limit, formulated in 1824, represents the maximal efficiency of a classical heat engine. In this work we present a thermodynamical analysis of a light amplifier based on a three-level atom coupled off-resonantly to a single quantized cavity mode and to two heat reservoirs with positive temperatures. Based on standard work and heat flow equilibrium, we show that for a cavity blue-detuned with respect to the atomic resonance, the system can surpass the Carnot limit. Nevertheless, the second law of thermodynamics is still obeyed, as the total entropy always increases. By analyzing a semiclassical version of the model, we derive a formula for the critical frequency for which the Carnot limit is broken and a formula for the amplifier efficiency which agrees with its quantum counterpart. In the semiclassical regime, however, the second law is not satisfied and hence it does not offer a physically acceptable description of the system. Finally, we show that breaking the Carnot limit occurs also in a blue-detuned quantum amplifier with output coupling, which represents a realistic model of a laser or maser.

  3. EDWARDS' REFERENCE CYCLE FOR INTERNAL AND EXTERNAL COMBUSTION ENGINES

    OpenAIRE

    A. E. Piir

    2014-01-01

    Useful physical regularities of a reversible thermodynamic cycle for heat engines have been established in the paper. The engines are using fuel combustion products as a heat source, and the environment - as a heat sink that surpasses Carnot cycle according to efficiency factor.

  4. The story of the greenhouse effect, from Carnot to Gaia. De Carnot a Gaia: histoire de l'effet de serre

    Energy Technology Data Exchange (ETDEWEB)

    Grinevald, J

    1992-05-01

    The theory of the greenhouse effect did not just appear in 1985. It has had a long and interesting birth dating back to the beginning of the 19th century. Here, Jacques Grinevald presents some of its decisive stages such as the thermodynamic revolution and Carnot's transformation of the image of the world into a machine, the hothouse theory advanced by John Tyndall, Vladimir Vernadsky's 'biosphere' ideas or James Lovelock's Gaia hypothesis. In spite of the controversy which surrounds it, the theory of the greenhouse effect is one of science's best established atmospheric theories.

  5. Magnetic refrigeration cycle analysis using selected thermodynamic property characterizations for gadolinium gallium garnet

    International Nuclear Information System (INIS)

    Murphy, R.W.

    1992-01-01

    Magneto-thermodynamic property characterizations were selected, adapted, and compared to material property data for gadolinium gallium garnet in the temperature range 4--40 K and magnetic field range 0--6 T. The most appropriate formulations were incorporated into a model in which methods similar to those previously developed for other materials and temperature ranges were used to make limitation and relative performance assessments of Carnot, ideal regenerative, and pseudo-constant field regenerative cycles. Analysis showed that although Carnot cycle limitations on available temperature lift for gadolinium gallium garnet are not as severe as those for materials previously examined, substantial improvements in cooling capacity/temperature lift combinations can be achieved using regenerative cycles within specified fields limits if significant loss mechanisms are mitigated

  6. Continuity and boundary conditions in thermodynamics: From Carnot's efficiency to efficiencies at maximum power

    Science.gov (United States)

    Ouerdane, H.; Apertet, Y.; Goupil, C.; Lecoeur, Ph.

    2015-07-01

    Classical equilibrium thermodynamics is a theory of principles, which was built from empirical knowledge and debates on the nature and the use of heat as a means to produce motive power. By the beginning of the 20th century, the principles of thermodynamics were summarized into the so-called four laws, which were, as it turns out, definitive negative answers to the doomed quests for perpetual motion machines. As a matter of fact, one result of Sadi Carnot's work was precisely that the heat-to-work conversion process is fundamentally limited; as such, it is considered as a first version of the second law of thermodynamics. Although it was derived from Carnot's unrealistic model, the upper bound on the thermodynamic conversion efficiency, known as the Carnot efficiency, became a paradigm as the next target after the failure of the perpetual motion ideal. In the 1950's, Jacques Yvon published a conference paper containing the necessary ingredients for a new class of models, and even a formula, not so different from that of Carnot's efficiency, which later would become the new efficiency reference. Yvon's first analysis of a model of engine producing power, connected to heat source and sink through heat exchangers, went fairly unnoticed for twenty years, until Frank Curzon and Boye Ahlborn published their pedagogical paper about the effect of finite heat transfer on output power limitation and their derivation of the efficiency at maximum power, now mostly known as the Curzon-Ahlborn (CA) efficiency. The notion of finite rate explicitly introduced time in thermodynamics, and its significance cannot be overlooked as shown by the wealth of works devoted to what is now known as finite-time thermodynamics since the end of the 1970's. The favorable comparison of the CA efficiency to actual values led many to consider it as a universal upper bound for real heat engines, but things are not so straightforward that a simple formula may account for a variety of situations. The

  7. From Finite Time to Finite Physical Dimensions Thermodynamics: The Carnot Engine and Onsager's Relations Revisited

    Science.gov (United States)

    Feidt, Michel; Costea, Monica

    2018-04-01

    Many works have been devoted to finite time thermodynamics since the Curzon and Ahlborn [1] contribution, which is generally considered as its origin. Nevertheless, previous works in this domain have been revealed [2], [3], and recently, results of the attempt to correlate Finite Time Thermodynamics with Linear Irreversible Thermodynamics according to Onsager's theory were reported [4]. The aim of the present paper is to extend and improve the approach relative to thermodynamic optimization of generic objective functions of a Carnot engine with linear response regime presented in [4]. The case study of the Carnot engine is revisited within the steady state hypothesis, when non-adiabaticity of the system is considered, and heat loss is accounted for by an overall heat leak between the engine heat reservoirs. The optimization is focused on the main objective functions connected to engineering conditions, namely maximum efficiency or power output, except the one relative to entropy that is more fundamental. Results given in reference [4] relative to the maximum power output and minimum entropy production as objective function are reconsidered and clarified, and the change from finite time to finite physical dimension was shown to be done by the heat flow rate at the source. Our modeling has led to new results of the Carnot engine optimization and proved that the primary interest for an engineer is mainly connected to what we called Finite Physical Dimensions Optimal Thermodynamics.

  8. Not all counterclockwise thermodynamic cycles are refrigerators

    Science.gov (United States)

    Dickerson, R. H.; Mottmann, J.

    2016-06-01

    Clockwise cycles on PV diagrams always represent heat engines. It is therefore tempting to assume that counterclockwise cycles always represent refrigerators. This common assumption is incorrect: most counterclockwise cycles cannot be refrigerators. This surprising result is explored here for quasi-static ideal gas cycles, and the necessary conditions for refrigeration cycles are clarified. Three logically self-consistent criteria can be used to determine if a counterclockwise cycle is a refrigerator. The most fundamental test compares the counterclockwise cycle with a correctly determined corresponding Carnot cycle. Other criteria we employ include a widely accepted description of the functional behavior of refrigerators, and a corollary to the second law that limits a refrigerator's coefficient of performance.

  9. Sedimentary processes in the Carnot Formation (Central African Republic) related to the palaeogeographic framework of Central Africa

    Science.gov (United States)

    Censier, Claude; Lang, Jacques

    1999-08-01

    The depositional environment, provenance and processes of emplacement of the detrital material of the Mesozoic Carnot Formation are defined, by bedding and sedimentological analysis of its main facies, and are reconstructed within the palaeogeographic framework of Central Africa. The clastic material was laid down between probably the Albian and the end of the Cretaceous, in a NNW-oriented braided stream fluvial system that drained into the Doba Trough (Chad) and probably also into the Touboro Basin (Cameroon). The material was derived from weathering of the underlying Devonian-Carboniferous Mambéré Glacial Formation and of the Precambrian schist-quartzite complex located to the south of the Carnot Formation. These results provide useful indications as to the provenance of diamonds mined in the southwest Central African Republic.

  10. Review of low-temperature vapour power cycle engines with quasi-isothermal expansion

    OpenAIRE

    Igobo, Opubo N.; Davies, Philip A.

    2014-01-01

    External combustion heat cycle engines convert thermal energy into useful work. Thermal energy resources include solar, geothermal, bioenergy, and waste heat. To harness these and maximize work output, there has been a renaissance of interest in the investigation of vapour power cycles for quasi-isothermal (near constant temperature) instead of adiabatic expansion. Quasi-isothermal expansion has the advantage of bringing the cycle efficiency closer to the ideal Carnot efficiency, but it requi...

  11. Absorption heat cycles. An experimental and theoretical study

    International Nuclear Information System (INIS)

    Abrahamsson, K.

    1993-09-01

    A flow sheeting programme, SHPUMP, was developed for simulating different absorption heat cycles. The programme consists of ten different modules which allow the user to construct his own absorption cycle. The ten modules configurate evaporators, absorbers, generators, rectifiers, condensers, solution heat exchangers, pumps, valves, mixers and splitters. Seven basic and well established absorption cycles are available in the configuration data base of the programme. A new Carnot model is proposed heat cycles. Together with exergy analysis, general equations for the Carnot coefficient of performance and equations for thermodynamic efficiency, exergetic efficiency and exergy index, are derived, discussed and compared for both absorption heat pumps and absorption heat transformers. Utilizing SHPUMP, simulation results are presented for different configurations where absorption heat cycles are suggested to be incorporated in three different unit operations within both pulp and paper and oleochemical industries. One of the application studies reveled that an absorption heat transformer incorporated with an evaporation plant in a major pulp and paper industry, would save 18% of the total prime energy consumption in one of the evaporation plants. It was also concluded that installing an absorption heat pump in a paper drying plant would result in steam savings equivalent to 12 MW. An experimental absorption heat transformer unit operating with self-circulation has been modified and thoroughly tested. A reference heat transformer plant has been designed and installed in a major pulp and paper mill where it is directly incorporated with one of the evaporation plants. Preliminary plant operation data are presented. 72 refs, 63 figs, 33 tabs

  12. On the question of heat engine cycles optimization

    Directory of Open Access Journals (Sweden)

    Костянтин Ігорович Ткаченко

    2015-10-01

    Full Text Available It is known that the efficiency of heat engines nowadays isn’t more than 50-60% for prototypes and maximum possible efficiency of a heat engine is considered Carnot cycle efficiency Thus, at least 40% of the disposable amount of heat is lost in the surrounding medium, unless the waste gases heat is utilized somehow. General idea of heat engines cycles is the transfer of energy from the heater (both external and internal to a working fluid, obtaining mechanical work from expanding of the working fluid, and returning the working fluid to the initial state by compression and excess heat discharge into a cooler. In this paper the combination of a heat engine operating according to the standard Edwards cycle and consisting of isochor, adiabat and isotherm, and the heat pump, using the reverse Carnot cycle is investigated. The heat pump partially picks out the heat of the working fluid at its isothermal compression, and returns it to the equivalent working fluid or regenerator cap, at the beginning of isochoric heating. The efficiency coefficient of the heat pump, and thus the work to putting it into action is calculated by proper equations at the constant temperature of the low-potential heat source (working fluid and variable temperature of the heated equivalent of the working fluid or the regenerator cap. Taking as an example selected quantitative parameters of the Edwards cycle it has been proved that the use of the heat pump increases the effective efficiency of combined cycle as compared to the basic one. In addition, it has been shown that the dependence of the efficiency on the degree of heat return is not monotonic and has a maximum

  13. Superfluid thermodynamic cycle refrigerator

    Science.gov (United States)

    Swift, Gregory W.; Kotsubo, Vincent Y.

    1992-01-01

    A cryogenic refrigerator cools a heat source by cyclically concentrating and diluting the amount of .sup.3 He in a single phase .sup.3 He-.sup.4 He solution. The .sup.3 He in superfluid .sup.4 He acts in a manner of an ideal gas in a vacuum. Thus, refrigeration is obtained using any conventional thermal cycle, but preferably a Stirling or Carnot cycle. A single phase solution of liquid .sup.3 He at an initial concentration in superfluid .sup.4 He is contained in a first variable volume connected to a second variable volume through a superleak device that enables free passage of .sup.4 He while restricting passage of .sup.3 He. The .sup.3 He is compressed (concentrated) and expanded (diluted) in a phased manner to carry out the selected thermal cycle to remove heat from the heat load for cooling below 1 K.

  14. Performance characteristics of a quantum Diesel refrigeration cycle

    International Nuclear Information System (INIS)

    He Jizhou; Wang Hao; Liu Sanqiu

    2009-01-01

    The Diesel refrigeration cycle using an ideal quantum gas as the working substance is called quantum Diesel refrigeration cycle, which is different from Carnot, Ericsson, Brayton, Otto and Stirling refrigeration cycles. For ideal quantum gases, a corrected equation of state, which considers the quantum behavior of gas particles, is used instead of the classical one. The purpose of this paper is to investigate the effect of quantum gas as the working substance on the performance of a quantum Diesel refrigeration cycle. It is found that coefficients of performance of the cycle are not affected by the quantum degeneracy of the working substance, which is the same as that of the classical Diesel refrigeration cycle. However, the refrigeration load is different from those of the classical Diesel refrigeration cycle. Lastly, the influence of the quantum degeneracy on the performance characteristics of the quantum Diesel refrigeration cycle operated in different temperature regions is discussed

  15. Low-temperature behaviour of an ideal Bose gas and some forbidden thermodynamic cycles

    International Nuclear Information System (INIS)

    Chen Jincan; Lin Bihong

    2003-01-01

    Based on the equation of state of an ideal Bose gas, the heat capacities at constant volume and constant pressure of the Bose system are derived and used to analyse the low-temperature behaviour of the Bose system. It is expounded that some important thermodynamic processes such as a constant pressure and an adiabatic process cannot be carried out from the region of T > T c to that of T c , where T c is the critical temperature of Bose-Einstein condensation of the Bose system. Consequently, some typical thermodynamic cycles such as the Carnot cycle, Brayton cycle, Otto cycle, Ericsson cycle, Diesel cycle and Atkinson cycle cannot be operated across the critical temperature T c of Bose-Einstein condensation of an ideal Bose gas

  16. Contribution by Lazare and Sadi Carnot to the caloric theory of heat and its inspirative role in thermodynamics

    Czech Academy of Sciences Publication Activity Database

    Šesták, Jaroslav; Mareš, Jiří J.; Hubík, Pavel; Proks, I.

    2009-01-01

    Roč. 97, č. 2 (2009), s. 679-683 ISSN 1388-6150 R&D Projects: GA AV ČR IAA1010404; GA AV ČR IAA100100639 Institutional research plan: CEZ:AV0Z10100521 Keywords : caloric as entropy * Carnot * efficiency * history * thermal analysis * thermodynamics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.587, year: 2009

  17. Stirling Engine Gets Revisited

    Science.gov (United States)

    Thompson, Frank

    2010-01-01

    One of the basic truths regarding energy conversion is that no thermodynamic cycle can be devised that is more efficient than a Carnot cycle operating between the same temperature limits. The efficiency of the Stirling cycle (patented by Rev. Robert Stirling in 1816) can approach that of the Carnot cycle and yet has not had the commercial success…

  18. Thermal power generation during heat cycle near room temperature

    Science.gov (United States)

    Shibata, Takayuki; Fukuzumi, Yuya; Kobayashi, Wataru; Moritomo, Yutaka

    2018-01-01

    We demonstrate that a sodium-ion secondary battery (SIB)-type thermocell consisting of two types of Prussian blue analogue (PBA) with different electrochemical thermoelectric coefficients (S EC ≡ ∂V/∂T V and T are the redox potential and temperature, respectively) produces electrical energy during heat cycles. The device produces an electrical energy of 2.3 meV/PBA per heat cycle between 295 K (= T L) and 323 K (= T H). The ideal thermal efficiency (η = 1.0%), which is evaluated using the heat capacity (C = 4.16 meV/K) of ideal Na2Co[Fe(CN)6], reaches 11% of the Carnot efficiency (ηth = 8.7%). Our SIB-type thermocell is a promising thermoelectric device that harvests waste heat near room temperature.

  19. Ideal thermodynamic processes of oscillatory-flow regenerative engines will go to ideal stirling cycle?

    Science.gov (United States)

    Luo, Ercang

    2012-06-01

    This paper analyzes the thermodynamic cycle of oscillating-flow regenerative machines. Unlike the classical analysis of thermodynamic textbooks, the assumptions for pistons' movement limitations are not needed and only ideal flowing and heat transfer should be maintained in our present analysis. Under such simple assumptions, the meso-scale thermodynamic cycles of each gas parcel in typical locations of a regenerator are analyzed. It is observed that the gas parcels in the regenerator undergo Lorentz cycle in different temperature levels, whereas the locus of all gas parcels inside the regenerator is the Ericson-like thermodynamic cycle. Based on this new finding, the author argued that ideal oscillating-flow machines without heat transfer and flowing losses is not the Stirling cycle. However, this new thermodynamic cycle can still achieve the same efficiency of the Carnot heat engine and can be considered a new reversible thermodynamic cycle under two constant-temperature heat sinks.

  20. Maximum Work of Free-Piston Stirling Engine Generators

    Science.gov (United States)

    Kojima, Shinji

    2017-04-01

    Using the method of adjoint equations described in Ref. [1], we have calculated the maximum thermal efficiencies that are theoretically attainable by free-piston Stirling and Carnot engine generators by considering the work loss due to friction and Joule heat. The net work done by the Carnot cycle is negative even when the duration of heat addition is optimized to give the maximum amount of heat addition, which is the same situation for the Brayton cycle described in our previous paper. For the Stirling cycle, the net work done is positive, and the thermal efficiency is greater than that of the Otto cycle described in our previous paper by a factor of about 2.7-1.4 for compression ratios of 5-30. The Stirling cycle is much better than the Otto, Brayton, and Carnot cycles. We have found that the optimized piston trajectories of the isothermal, isobaric, and adiabatic processes are the same when the compression ratio and the maximum volume of the same working fluid of the three processes are the same, which has facilitated the present analysis because the optimized piston trajectories of the Carnot and Stirling cycles are the same as those of the Brayton and Otto cycles, respectively.

  1. Performances of four magnetic heat-pump cycles

    International Nuclear Information System (INIS)

    Chen, F.C.; Murphy, R.W.; Mel, V.C.; Chen, G.L.

    1990-01-01

    Magnetic heat pumps have been successfully used for refrigeration applications at near absolute-zero-degree temperatures. In these applications, a temperature lift of a few degrees in a cryogenic environment is sufficient and can be easily achieved by a simple magnetic heat-pump cycle. To extend magnetic heat pumping to other temperature ranges and other types of applications in which the temperature lift is more than just a few degrees requires more involved cycle processes. This paper investigates the characteristics of a few better-known thermomagnetic heat-pump cycles (Carnot, Ericsson, Stirling, and regenerative) in extended ranges of temperature lift. The regenerative cycle is the most efficient one. For gadolinium operating between 0 and 7 T (Tesla) in a heat pump cycle with a heat-rejection temperature of 320 K, our analysis predicted a 42% loss in coefficient of performance at 260 K cooling temperature, and a 15% loss in capacity at 232 K cooling temperature for the constant-field cycle as compared with the ideal regenerative cycle. Such substantial penalties indicate that the potential irreversibilities from this one source (the additional heat transfer that would be needed for the constant-field vs. the ideal regenerative cycle) may adversely affect the viability of certain proposed MHP concepts if the relevant loss mechanisms are not adequately addressed

  2. Influence of quantum degeneracy and regeneration on the performance of Bose-Stirling refrigeration-cycles operated in different temperature regions

    International Nuclear Information System (INIS)

    Lin Bihong; Zhang Yue; Chen Jincan

    2006-01-01

    The Stirling refrigeration cycle using an ideal Bose-gas as the working substance is called the Bose-Stirling refrigeration cycle, which is different from other thermodynamic cycles such as the Carnot cycle, Ericsson cycle, Brayton cycle, Otto cycle, Diesel cycle and Atkinson cycle working with an ideal Bose gas and may be operated across the critical temperature of Bose-Einstein condensation of the Bose system. The performance of the cycle is investigated, based on the equation of state of an ideal Bose gas. The inherent regenerative losses of the cycle are considered and the coefficient of performance and the amount of refrigeration of the cycle are calculated. The results obtained here are compared with those derived from the classical Stirling refrigeration cycle, using an ideal gas as the working substance. The influence of quantum degeneracy and inherent regenerative losses on the performance of the Bose Stirling refrigeration cycle operated in different temperature regions is discussed in detail, and consequently, general performance characteristics of the cycle are revealed

  3. Electrical performances of pyroelectric bimetallic strip heat engines describing a Stirling cycle

    Science.gov (United States)

    Arnaud, A.; Boughaleb, J.; Monfray, S.; Boeuf, F.; Cugat, O.; Skotnicki, T.

    2015-12-01

    This paper deals with the analytical modeling of pyroelectric bimetallic strip heat engines. These devices are designed to exploit the snap-through of a thermo-mechanically bistable membrane to transform a part of the heat flowing through the membrane into mechanical energy and to convert it into electric energy by means of a piezoelectric layer deposited on the surface of the bistable membrane. In this paper, we describe the properties of these heat engines in the case when they complete a Stirling cycle, and we evaluate the performances (available energy, Carnot efficiency...) of these harvesters at the macro- and micro-scale.

  4. The optimal performance of a quantum refrigeration cycle working with harmonic oscillators

    International Nuclear Information System (INIS)

    Lin Bihong; Chen Jincan; Hua Ben

    2003-01-01

    The cycle model of a quantum refrigeration cycle working with many non-interacting harmonic oscillators and consisting of two isothermal and two constant-frequency processes is established. Based on the quantum master equation and semi-group approach, the general performance of the cycle is investigated. Expressions for some important performance parameters, such as the coefficient of performance, cooling rate, power input, and rate of the entropy production, are derived. Several interesting cases are discussed and, especially, the optimal performance of the cycle at high temperatures is discussed in detail. Some important characteristic curves of the cycle, such as the cooling rate versus coefficient of performance curves, the power input versus coefficient of performance curves, the cooling rate versus power input curves, and so on, are presented. The maximum cooling rate and the corresponding coefficient of performance are calculated. Other optimal performances are also analysed. The results obtained here are compared with those of an Ericsson or Stirling refrigeration cycle using an ideal gas as the working substance. Finally, the optimal performance of a harmonic quantum Carnot refrigeration cycle at high temperatures is derived easily

  5. Thermally regenerative hydrogen/oxygen fuel cell power cycles

    Science.gov (United States)

    Morehouse, J. H.

    1986-01-01

    Two innovative thermodynamic power cycles are analytically examined for future engineering feasibility. The power cycles use a hydrogen-oxygen fuel cell for electrical energy production and use the thermal dissociation of water for regeneration of the hydrogen and oxygen. The TDS (thermal dissociation system) uses a thermal energy input at over 2000 K to thermally dissociate the water. The other cycle, the HTE (high temperature electrolyzer) system, dissociates the water using an electrolyzer operating at high temperature (1300 K) which receives its electrical energy from the fuel cell. The primary advantages of these cycles is that they are basically a no moving parts system, thus having the potential for long life and high reliability, and they have the potential for high thermal efficiency. Both cycles are shown to be classical heat engines with ideal efficiency close to Carnot cycle efficiency. The feasibility of constructing actual cycles is investigated by examining process irreversibilities and device efficiencies for the two types of cycles. The results show that while the processes and devices of the 2000 K TDS exceed current technology limits, the high temperature electrolyzer system appears to be a state-of-the-art technology development. The requirements for very high electrolyzer and fuel cell efficiencies are seen as determining the feasbility of the HTE system, and these high efficiency devices are currently being developed. It is concluded that a proof-of-concept HTE system experiment can and should be conducted.

  6. Study and Development of an Air Conditioning System Operating on a Magnetic Heat Pump Cycle

    Science.gov (United States)

    Wang, Pao-Lien

    1991-01-01

    This report describes the design of a laboratory scale demonstration prototype of an air conditioning system operating on a magnetic heat pump cycle. Design parameters were selected through studies performed by a Kennedy Space Center (KSC) System Simulation Computer Model. The heat pump consists of a rotor turning through four magnetic fields that are created by permanent magnets. Gadolinium was selected as the working material for this demonstration prototype. The rotor was designed to be constructed of flat parallel disks of gadolinium with very little space in between. The rotor rotates in an aluminum housing. The laboratory scale demonstration prototype is designed to provide a theoretical Carnot Cycle efficiency of 62 percent and a Coefficient of Performance of 16.55.

  7. Exergoeconomic performance optimization for a steady-flow endoreversible refrigeration model including six typical cycles

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Lingen; Kan, Xuxian; Sun, Fengrui; Wu, Feng [College of Naval Architecture and Power, Naval University of Engineering, Wuhan 430033 (China)

    2013-07-01

    The operation of a universal steady flow endoreversible refrigeration cycle model consisting of a constant thermal-capacity heating branch, two constant thermal-capacity cooling branches and two adiabatic branches is viewed as a production process with exergy as its output. The finite time exergoeconomic performance optimization of the refrigeration cycle is investigated by taking profit rate optimization criterion as the objective. The relations between the profit rate and the temperature ratio of working fluid, between the COP (coefficient of performance) and the temperature ratio of working fluid, as well as the optimal relation between profit rate and the COP of the cycle are derived. The focus of this paper is to search the compromised optimization between economics (profit rate) and the utilization factor (COP) for endoreversible refrigeration cycles, by searching the optimum COP at maximum profit, which is termed as the finite-time exergoeconomic performance bound. Moreover, performance analysis and optimization of the model are carried out in order to investigate the effect of cycle process on the performance of the cycles using numerical example. The results obtained herein include the performance characteristics of endoreversible Carnot, Diesel, Otto, Atkinson, Dual and Brayton refrigeration cycles.

  8. Enhanced efficiency of internal combustion engines by employing spinning gas.

    Science.gov (United States)

    Geyko, V I; Fisch, N J

    2014-08-01

    The efficiency of the internal combustion engine might be enhanced by employing spinning gas. A gas spinning at near sonic velocities has an effectively higher heat capacity, which allows practical fuel cycles, which are far from the Carnot efficiency, to approach more closely the Carnot efficiency. A remarkable gain in fuel efficiency is shown to be theoretically possible for the Otto and Diesel cycles. The use of a flywheel, in principle, could produce even greater increases in efficiency.

  9. Applicability of the minimum entropy generation method for optimizing thermodynamic cycles

    Institute of Scientific and Technical Information of China (English)

    Cheng Xue-Tao; Liang Xin-Gang

    2013-01-01

    Entropy generation is often used as a figure of merit in thermodynamic cycle optimizations.In this paper,it is shown that the applicability of the minimum entropy generation method to optimizing output power is conditional.The minimum entropy generation rate and the minimum entropy generation number do not correspond to the maximum output power when the total heat into the system of interest is not prescribed.For the cycles whose working medium is heated or cooled by streams with prescribed inlet temperatures and prescribed heat capacity flow rates,it is theoretically proved that both the minimum entropy generation rate and the minimum entropy generation number correspond to the maximum output power when the virtual entropy generation induced by dumping the used streams into the environment is considered.However,the minimum principle of entropy generation is not tenable in the case that the virtual entropy generation is not included,because the total heat into the system of interest is not fixed.An irreversible Carnot cycle and an irreversible Brayton cycle are analysed.The minimum entropy generation rate and the minimum entropy generation number do not correspond to the maximum output power if the heat into the system of interest is not prescribed.

  10. Applicability of the minimum entropy generation method for optimizing thermodynamic cycles

    International Nuclear Information System (INIS)

    Cheng Xue-Tao; Liang Xin-Gang

    2013-01-01

    Entropy generation is often used as a figure of merit in thermodynamic cycle optimizations. In this paper, it is shown that the applicability of the minimum entropy generation method to optimizing output power is conditional. The minimum entropy generation rate and the minimum entropy generation number do not correspond to the maximum output power when the total heat into the system of interest is not prescribed. For the cycles whose working medium is heated or cooled by streams with prescribed inlet temperatures and prescribed heat capacity flow rates, it is theoretically proved that both the minimum entropy generation rate and the minimum entropy generation number correspond to the maximum output power when the virtual entropy generation induced by dumping the used streams into the environment is considered. However, the minimum principle of entropy generation is not tenable in the case that the virtual entropy generation is not included, because the total heat into the system of interest is not fixed. An irreversible Carnot cycle and an irreversible Brayton cycle are analysed. The minimum entropy generation rate and the minimum entropy generation number do not correspond to the maximum output power if the heat into the system of interest is not prescribed. (general)

  11. Heat exchanger inventory cost optimization for power cycles with one feedwater heater

    International Nuclear Information System (INIS)

    Qureshi, Bilal Ahmed; Antar, Mohamed A.; Zubair, Syed M.

    2014-01-01

    Highlights: • Cost optimization of heat exchanger inventory in power cycles is investigated. • Analysis for an endoreversible power cycle with an open feedwater heater is shown. • Different constraints on the power cycle are investigated. • The constant heat addition scenario resulted in the lowest value of the cost function. - Abstract: Cost optimization of heat exchanger inventory in power cycles with one open feedwater heater is undertaken. In this regard, thermoeconomic analysis for an endoreversible power cycle with an open feedwater heater is shown. The scenarios of constant heat rejection and addition rates, power as well as rate of heat transfer in the open feedwater heater are studied. All cost functions displayed minima with respect to the high-side absolute temperature ratio (θ 1 ). In this case, the effect of the Carnot temperature ratio (Φ 1 ), absolute temperature ratio (ξ) and the phase-change absolute temperature ratio for the feedwater heater (Φ 2 ) are qualitatively the same. Furthermore, the constant heat addition scenario resulted in the lowest value of the cost function. For variation of all cost functions, the smaller the value of the phase-change absolute temperature ratio for the feedwater heater (Φ 2 ), lower the cost at the minima. As feedwater heater to hot end unit cost ratio decreases, the minimum total conductance required increases

  12. Contribution to magnetic refrigeration study at liquid helium study

    International Nuclear Information System (INIS)

    Lacaze, A.

    1985-10-01

    An experimental prototype of magnetic refrigerator operates, following a Carnot cycle, with gallium gadolinium garnet, from liquid helium at 4.2 0 K. Analysis of the cyle and heat exchanges allowed to improve performance up to get more than 50% of Carnot yield at 1.8 0 K and nearly 80% at 2.1 0 K. Operation conditions of a regenerator refrigerator between 4 and 20 0 K are studied. The association of a magnetic refrigerator and a gas refrigerator is analyzed. Among different ways to realize the magnetic stage, an active regenerator cycle is chosen. An experimental device is described [fr

  13. A unified model of combined energy systems with different cycle modes and its optimum performance characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yue [Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen 361005 (China); College of Information Science and Engineering, Huaqiao University, Quanzhou 362021 (China); Hu, Weiqiang [Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen 361005 (China); Ou Congjie [College of Information Science and Engineering, Huaqiao University, Quanzhou 362021 (China); Chen Jincan [Department of Physics and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen 361005 (China)], E-mail: jcchen@xmu.edu.cn

    2009-06-15

    A unified model is presented for a class of combined energy systems, in which the systems mainly consist of a heat engine, a combustor and a counter-flow heat exchanger and the heat engine in the systems may have different thermodynamic cycle modes such as the Brayton cycle, Carnot cycle, Stirling cycle, Ericsson cycle, and so on. Not only the irreversibilities of the heat leak and finite-rate heat transfer but also the different cycle modes of the heat engine are considered in the model. On the basis of Newton's law, expressions for the overall efficiency and power output of the combined energy system with an irreversible Brayton cycle are derived. The maximum overall efficiency and power output and other relevant parameters are calculated. The general characteristic curves of the system are presented for some given parameters. Several interesting cases are discussed in detail. The results obtained here are very general and significant and can be used to discuss the optimal performance characteristics of a class of combined energy systems with different cycle modes. Moreover, it is significant to point out that not only the important conclusions obtained in Bejan's first combustor model and Peterson's general combustion driven model but also the optimal performance of a class of solar-driven heat engine systems can be directly derived from the present paper under some limit conditions.

  14. A unified model of combined energy systems with different cycle modes and its optimum performance characteristics

    International Nuclear Information System (INIS)

    Zhang Yue; Hu, Weiqiang; Ou Congjie; Chen Jincan

    2009-01-01

    A unified model is presented for a class of combined energy systems, in which the systems mainly consist of a heat engine, a combustor and a counter-flow heat exchanger and the heat engine in the systems may have different thermodynamic cycle modes such as the Brayton cycle, Carnot cycle, Stirling cycle, Ericsson cycle, and so on. Not only the irreversibilities of the heat leak and finite-rate heat transfer but also the different cycle modes of the heat engine are considered in the model. On the basis of Newton's law, expressions for the overall efficiency and power output of the combined energy system with an irreversible Brayton cycle are derived. The maximum overall efficiency and power output and other relevant parameters are calculated. The general characteristic curves of the system are presented for some given parameters. Several interesting cases are discussed in detail. The results obtained here are very general and significant and can be used to discuss the optimal performance characteristics of a class of combined energy systems with different cycle modes. Moreover, it is significant to point out that not only the important conclusions obtained in Bejan's first combustor model and Peterson's general combustion driven model but also the optimal performance of a class of solar-driven heat engine systems can be directly derived from the present paper under some limit conditions

  15. The fundamental optimal relations of the allocation, cost and effectiveness of the heat exchangers of a Carnot-like power plant

    Energy Technology Data Exchange (ETDEWEB)

    Aragon-Gonzalez, G; Canales-Palma, A; Leon-Galicia, A; Rivera-Camacho, J M [PDPA, UAM-Azcapotzalco, Av San Pablo 180, Col. Reynosa, Azcapotzalco, 02200 Mexico, DF (Mexico)], E-mail: gag@correo.azc.uam.mx

    2009-10-23

    A stationary Carnot-like power plant model, with three sources of irreversibilities (the finite rate of heat transfers, heat leak and internal dissipations of the working fluid), is analyzed by a criterion of partial optimization for five objective functions (power, efficiency, ecological function, efficient power and {omega}-dot criterion). A remarkable result is that if two constraints (design rules) are applied alternatively: constrained internal thermal conductance or fixed total area of the heat exchangers from hot and cold sides; the optimal allocation, cost and effectiveness of the heat exchangers are the same for all these objective functions independently of the transfer heat law used. Thus, it is enough to find these optimal relations for only one, maximum power, when all heat transfers are linear. In particular, for the Curzon-Albhorn-like model (without heat leak), the criterion for the so-called ecological function, including other variables (the internal isentropic temperature ratio), becomes total.

  16. The fundamental optimal relations of the allocation, cost and effectiveness of the heat exchangers of a Carnot-like power plant

    International Nuclear Information System (INIS)

    Aragon-Gonzalez, G; Canales-Palma, A; Leon-Galicia, A; Rivera-Camacho, J M

    2009-01-01

    A stationary Carnot-like power plant model, with three sources of irreversibilities (the finite rate of heat transfers, heat leak and internal dissipations of the working fluid), is analyzed by a criterion of partial optimization for five objective functions (power, efficiency, ecological function, efficient power and Ω-dot criterion). A remarkable result is that if two constraints (design rules) are applied alternatively: constrained internal thermal conductance or fixed total area of the heat exchangers from hot and cold sides; the optimal allocation, cost and effectiveness of the heat exchangers are the same for all these objective functions independently of the transfer heat law used. Thus, it is enough to find these optimal relations for only one, maximum power, when all heat transfers are linear. In particular, for the Curzon-Albhorn-like model (without heat leak), the criterion for the so-called ecological function, including other variables (the internal isentropic temperature ratio), becomes total.

  17. Combined heat and power considered as a virtual steam cycle heat pump

    International Nuclear Information System (INIS)

    Lowe, Robert

    2011-01-01

    The first aim of this paper is to shed light on the thermodynamic reasons for the practical pursuit of low temperature operation by engineers involved in the design and the operation of combined heat and power (CHP) and district heating (DH) systems. The paper shows that the steam cycle of a combined heat and power generator is thermodynamically equivalent to a conventional steam cycle generator plus an additional virtual steam cycle heat pump. This apparently novel conceptualisation leads directly to (i) the observed sensitivity of coefficient of performance of CHP to supply and return temperatures in associated DH systems, and (ii) the conclusion that the performance of CHP will tend to be significantly higher than real heat pumps operating at similar temperatures. The second aim, which is pursued more qualitatively, is to show that the thermodynamic performance advantages of CHP are consistent with the goal of deep, long-term decarbonisation of industrialised economies. As an example, estimates are presented, which suggest that CHP based on combined-cycle gas turbines with carbon capture and storage has the potential to reduce the carbon intensity of delivered heat by a factor of ∼30, compared with a base case of natural gas-fired condensing boilers. - Highlights: → Large-scale CHP systems are thermodynamically equivalent to virtual steam cycle heat pumps. → COPs of such virtual heat pumps are necessarily better than the Carnot limit for real heat pumps. → COPs can approach 9 for plant matched to district heating systems with flow temperatures of 90 deg. C. → CHP combined with CCGT and CCS can reduce the carbon intensity of delivered heat ∼30-fold.

  18. Quantum Heat Engine and Negative Boltzmann Temperature

    International Nuclear Information System (INIS)

    Xi Jing-Yi; Quan Hai-Tao

    2017-01-01

    To clarify the ambiguity on negative Boltzmann temperature in literature, we study the Carnot and the Otto cycle with one of the heat reservoirs at the negative Boltzmann temperature based on a canonical ensemble description. The work extraction, entropy production and the efficiency of these cycles are explored. Conditions for constructing and properties of these thermodynamic cycles are elucidated. We find that the apparent “violation” of the second law of thermodynamics in these cycles are due to the fact that the traditional definition of thermodynamic efficiency is inappropriate in this situation. When properly understanding the efficiency and the adiabatic processes, in which the system crosses over “absolute ZERO” in a limit sense, the Carnot cycle with one of the heat reservoirs at a negative Boltzmann temperature can be understood straightforwardly, and it contradicts neither the second nor the third law of thermodynamics. Hence, negative Boltzmann temperature is a consistent concept in thermodynamics. We use a two-level system and an Ising spin system to illustrate our central results. (paper)

  19. Optimal operating conditions of a transcritical endoreversible cycle using a low enthalpy heat source

    International Nuclear Information System (INIS)

    Rachedi, Malika; Feidt, Michel; Amirat, Madjid; Merzouk, Mustapha

    2016-01-01

    Highlights: • Thermodynamics analysis of a finite size heat engine driven by a finite heat source. • Mathematical modelling of a transcritical endoreversible organic Rankine cycle. • Parametric study of the optimum operating conditions of transcritical cycle. • Choice of appropriate parameters could lead to very promising efficiencies. - Abstract: In the context of thermodynamic analysis of finite dimensions systems, we studied the optimum operating conditions of an endoreversible thermal machine. In this study, we considered a transcritical cycle, considering external irreversibilities. The hot reservoir is a low enthalpy geothermal heat source; therefore, it is assumed to be finite, whereas the cold reservoir is assumed to be infinite. The power optimisation is investigated by searching the optimum effectiveness of the heat-exchanger at the hot side of the engine. The sum of the total effectiveness and the second law of thermodynamics are used as constraints for optimisation. The optimal temperatures of the working fluid and optimum performances are evaluated based on the most significant parameters of the system: (1) the ratio of heat capacity rate of the working fluid to the heat capacity rate of the coolant and (2) the ratio of the sink temperature to the temperature of the hot source. The parametric study of the cycle and its approximation by a trilateral cycle enabled us to determine the optimum value of the effectiveness of the heat exchangers and the optimal operating temperatures of the cycle considered. The efficiencies obtained are in the range of 15–25% and was found to exceed the efficiency expected by the Curzon and Ahlborn prevision; meanwhile, the Carnot efficiency remains at a high limit.

  20. Fourier heat conduction as a phenomenon described within the scope of the second law

    Energy Technology Data Exchange (ETDEWEB)

    Jesudason, Christopher G. [Chemistry Department and Center for Theoretical and Computational Physics, University of Malaya, 50603 Kuala Lumpur (Malaysia)

    2014-12-10

    The historical development of the Carnot cycle necessitated the construction of isothermal and adiabatic pathways within the cycle that were also mechanically 'reversible' which lead eventually to the Kelvin-Clausius development of the entropy function S where for any reversible closed path C, ∮{sub C} dS = 0 based on an infinite number of concatenated Carnot engines that approximated the said path and where for each engine ΔQ{sub 1}/T{sub 1}+ΔQ{sub 2}/T{sub 2} = 0 where the Q's and T's are the heat absorption increments and temperature respectively with the subscripts indicating the isothermal paths (1;2) where for the Carnot engine, the heat absorption is for the diathermal (isothermal) paths of the cycle only. Since 'heat' has been defined as that form of energy that is transferred as a result of a temperature difference and a corollary of the Clausius statement of the Second law is that it is impossible for heat to be transferred from a cold to a hot reservoir with no other effect on the environment, these statements suggested that the local mode of transfer of 'heat' in the isothermal segments of the pathway does imply a Fourier heat conduction mechanism (to conform to the definition of 'heat') albeit of a 'reversible' kind, but on the other hand, the Fourier mechanism is apparently irreversible, leading to an increase in entropy of the combined reservoirs at either end of the material involved in the conveyance of the heat energy. These and several other considerations lead Benofy and Quay (BQ) to postulate the Fourier heat conduction phenomenon to be an ancillary principle in thermodynamics, with this principle being strictly local in nature, where the global Second law statements could not be applied to this local process. Here we present equations that model heat conduction as a thermodynamically reversible but mechanically irreversible process where due to the belief in mechanical time

  1. Nant-De-Chatillon: electric power generation by ORC (organic Rankine cycle) using waste heat from the Chatillon biogas plant; Nant-de-Chatillon: Production d'electricite par ORC a partir des rejets de chaleur du site de methanisation de Chatillon. Resume

    Energy Technology Data Exchange (ETDEWEB)

    Kane, M.; Gay, B.

    2005-07-01

    This report prepared for the Swiss Federal Office of Energy (SFOE) describes the practical realisation and testing of a heat recovery system based on a one-stage organic Rankine cycle with R134a as the working fluid. The waste heat has a temperature of 95 {sup o}C and originates from a gas engine that powers a small co-generation plant fuelled with biogas produced on-site. Two similar cycles have been built, ORC1 with one and ORC2 with two turbines. Only ORC1 has been tested so far. The maximum efficiency measured in these tests was 6.64% (theoretical Carnot-efficiency: 17 %) and the electric power output was 5.0 kW. The problems encountered during commissioning are described and recommendations for further improvements are given.

  2. Thermodynamic analysis on theoretical models of cycle combined heat exchange process: The reversible heat exchange process

    International Nuclear Information System (INIS)

    Zhang, Chenghu; Li, Yaping

    2017-01-01

    Concept of reversible heat exchange process as the theoretical model of the cycle combined heat exchanger could be useful to determine thermodynamics characteristics and the limitation values in the isolated heat exchange system. In this study, the classification of the reversible heat exchange processes is presented, and with the numerical method, medium temperature variation tendency and the useful work production and usage in the whole process are investigated by the construction and solution of the mathematical descriptions. Various values of medium inlet temperatures and heat capacity ratio are considered to analyze the effects of process parameters on the outlet temperature lift/drop. The maximum process work transferred from the Carnot cycle region to the reverse cycle region is also researched. Moreover, influence of the separating point between different sub-processes on temperature variation profile and the process work production are analyzed. In addition, the heat-exchange-enhancement-factor is defined to study the enhancement effect of the application of the idealized process in the isolated heat exchange system, and the variation degree of this factor with process parameters change is obtained. The research results of this paper can be a theoretical guidance to construct the cycle combined heat exchange process in the practical system. - Highlights: • A theoretical model of Cycle combined heat exchange process is proposed. • The classification of reversible heat exchange process are presented. • Effects of Inlet temperatures and heat capacity ratio on process are analyzed. • Process work transmission through the whole process is studied. • Heat-exchange-enhancement-factor can be a criteria to express the application effect of the idealized process.

  3. Dissipated energy and entropy production for an unconventional heat engine: the stepwise `circular cycle'

    Science.gov (United States)

    di Liberto, Francesco; Pastore, Raffaele; Peruggi, Fulvio

    2011-05-01

    When some entropy is transferred, by means of a reversible engine, from a hot heat source to a colder one, the maximum efficiency occurs, i.e. the maximum available work is obtained. Similarly, a reversible heat pumps transfer entropy from a cold heat source to a hotter one with the minimum expense of energy. In contrast, if we are faced with non-reversible devices, there is some lost work for heat engines, and some extra work for heat pumps. These quantities are both related to entropy production. The lost work, i.e. ? , is also called 'degraded energy' or 'energy unavailable to do work'. The extra work, i.e. ? , is the excess of work performed on the system in the irreversible process with respect to the reversible one (or the excess of heat given to the hotter source in the irreversible process). Both quantities are analysed in detail and are evaluated for a complex process, i.e. the stepwise circular cycle, which is similar to the stepwise Carnot cycle. The stepwise circular cycle is a cycle performed by means of N small weights, dw, which are first added and then removed from the piston of the vessel containing the gas or vice versa. The work performed by the gas can be found as the increase of the potential energy of the dw's. Each single dw is identified and its increase, i.e. its increase in potential energy, evaluated. In such a way it is found how the energy output of the cycle is distributed among the dw's. The size of the dw's affects entropy production and therefore the lost and extra work. The distribution of increases depends on the chosen removal process.

  4. Thermodynamic analysis of vapor compression heat pump cycle for tap water heating and development of CO_2 heat pump water heater for residential use

    International Nuclear Information System (INIS)

    Saikawa, Michiyuki; Koyama, Shigeru

    2016-01-01

    Highlights: • The ideal vapor compression cycle for tap water heating and its COP were defined. • It was verified theoretically that CO_2 achieves the highest COP for tap water heating. • The prototype of CO_2 heat pump water heater for residential use was developed. • Further COP improvement of CO_2 heat pump water heater was estimated. - Abstract: The ideal vapor compression cycle for tap water heating and its coefficient of performance (COP) have been studied theoretically at first. The ideal cycle is defined as the cycle whose high temperature heat source varies temperature with constant specific heat and other processes are same as the reverse Carnot cycle. The COP upper limit of single stage compression heat pump cycle for tap water heating with various refrigerants such as fluorocarbons and natural refrigerants was calculated. The refrigerant which achieves the highest COP for supplying hot water is CO_2. Next, the prototype of CO_2 heat pump water heater for residential use has been developed. Its outline and experimental results are described. Finally its further possibility of COP improvement has been studied. The COP considered a limit from a technical point of view was estimated about 6.0 at the Japanese shoulder season (spring and autumn) test condition of heating water from 17 °C to 65 °C at 16 °C heat source air temperature (dry bulb)/12 °C (wet bulb).

  5. Eficiencia y disimetría: El caso bioético de la máquina de vapor y de la idea de Carnot

    Directory of Open Access Journals (Sweden)

    Ingeborg Carvajal Freese

    2012-01-01

    Full Text Available Sin lugar a dudas, la máquina de vapor representa un prototipo de aquellas iniciativas tecnológicas que parecían destinadas a cumplir el sueño de progreso, poder y control ilimitados. Sadi Carnot visualizó en la energía de vapor el motor universal e intuyó que de ahí en adelante el mundo irrevocablemente se fracturaría en dos: por un lado permanecerían, estáticos y atrasados, los pueblos primitivos productores de calor; por el otro, avanzarían de manera acelerada los hombres civilizados poseedores de la nueva máquina generadora de trabajo. Aún hoy, cuando el mito tecnológico del progreso ilimitado se ha roto, las brechas sociales siguen indefectiblemente vinculadas a los inventos que se traducen en una redistribución de la energía. Corresponde a la Bioética hacer visibles los ámbitos que se afectan cuando la eficiencia técnica se transmuta en valor y las disimetrías concomitantes se difunden y se amplifican por doquier.

  6. Magnetic refrigeration: Materials, design, and applications. (Latest citations from the INSPEC: Information services for the Physics and Engineering Communities database). Published Search

    International Nuclear Information System (INIS)

    1993-08-01

    The bibliography contains citations concerning cryogenics using magnetic refrigerants. Refrigerant properties, magnetic materials, and thermal characteristics are discussed. Magnetic refrigerators are used for helium liquefaction, cooling superconductors, and superfluid helium production. Carnot-cycle refrigerators, reciprocating refrigerators, parasitic refrigerators, Ericsson refrigerators, and Stirling cycle refrigerators are among the types of magnetic refrigerators evaluated. (Contains a minimum of 94 citations and includes a subject term index and title list.)

  7. Magnetic refrigerator for hydrogen liquefaction

    Energy Technology Data Exchange (ETDEWEB)

    Numazawa, T [National Institute for Materials Science, Tsukuba (Japan); Kamlya, K. [Japan Atomic Energy Agency, Naka (Japan); Utaki, T. [Osaka University, Osaka (Japan); Matsumoto, K. [Kanazawa University, Kanazawa (Japan)

    2013-06-15

    This paper reviews the development status of magnetic refrigeration system for hydrogen liquefaction. There is no doubt that hydrogen is one of most important energy sources in the near future. In particular, liquid hydrogen can be utilized for infrastructure construction consisting of storage and transportation. Liquid hydrogen is in cryogenic temperatures and therefore high efficient liquefaction method must be studied. Magnetic refrigeration which uses the magneto-caloric effect has potential to realize not only the higher liquefaction efficiency > 50 %, but also to be environmentally friendly and cost effective. Our hydrogen magnetic refrigeration system consists of Carnot cycle for liquefaction stage and AMR (active magnetic regenerator) cycle for precooling stages. For the Carnot cycle, we develop the high efficient system > 80 % liquefaction efficiency by using the heat pipe. For the AMR cycle, we studied two kinds of displacer systems, which transferred the working fluid. We confirmed the AMR effect with the cooling temperature span of 12 K for 1.8 T of the magnetic field and 6 second of the cycle. By using the simulation, we estimate the total efficiency of the hydrogen liquefaction plant for 10 kg/day. A FOM of 0.47 is obtained in the magnetic refrigeration system operation temperature between 20 K and 77 K including LN2 work input.

  8. On the thermodynamics of waste heat recovery from internal combustion engine exhaust gas

    Science.gov (United States)

    Meisner, G. P.

    2013-03-01

    The ideal internal combustion (IC) engine (Otto Cycle) efficiency ηIC = 1-(1/r)(γ - 1) is only a function of engine compression ratio r =Vmax/Vmin and exhaust gas specific heat ratio γ = cP/cV. Typically r = 8, γ = 1.4, and ηIC = 56%. Unlike the Carnot Cycle where ηCarnot = 1-(TC/TH) for a heat engine operating between hot and cold heat reservoirs at TH and TC, respectively, ηIC is not a function of the exhaust gas temperature. Instead, the exhaust gas temperature depends only on the intake gas temperature (ambient), r, γ, cV, and the combustion energy. The ejected exhaust gas heat is thermally decoupled from the IC engine and conveyed via the exhaust system (manifold, pipe, muffler, etc.) to ambient, and the exhaust system is simply a heat engine that does no useful work. The maximum fraction of fuel energy that can be extracted from the exhaust gas stream as useful work is (1-ηIC) × ηCarnot = 32% for TH = 850 K (exhaust) and TC = 370 K (coolant). This waste heat can be recovered using a heat engine such as a thermoelectric generator (TEG) with ηTEG> 0 in the exhaust system. A combined IC engine and TEG system can generate net useful work from the exhaust gas waste heat with efficiency ηWH = (1-ηIC) × ηCarnot ×ηTEG , and this will increase the overall fuel efficiency of the total system. Recent improvements in TEGs yield ηTEG values approaching 15% giving a potential total waste heat conversion efficiency of ηWH = 4.6%, which translates into a fuel economy improvement approaching 5%. This work is supported by the US DOE under DE-EE0005432.

  9. High temperature refrigerator

    International Nuclear Information System (INIS)

    Steyert, W.A. Jr.

    1978-01-01

    A high temperature magnetic refrigerator is described which uses a Stirling-like cycle in which rotating magnetic working material is heated in zero field and adiabatically magnetized, cooled in high field, then adiabatically demagnetized. During this cycle the working material is in heat exchange with a pumped fluid which absorbs heat from a low temperature heat source and deposits heat in a high temperature reservoir. The magnetic refrigeration cycle operates at an efficiency 70% of Carnot

  10. Identifying Student Difficulties with Entropy, Heat Engines, and the Carnot Cycle

    Science.gov (United States)

    Smith, Trevor I.; Christensen, Warren M.; Mountcastle, Donald B.; Thompson, John R.

    2015-01-01

    We report on several specific student difficulties regarding the second law of thermodynamics in the context of heat engines within upper-division undergraduate thermal physics courses. Data come from ungraded written surveys, graded homework assignments, and videotaped classroom observations of tutorial activities. Written data show that students…

  11. Work extraction and thermodynamics for individual quantum systems

    Science.gov (United States)

    Skrzypczyk, Paul; Short, Anthony J.; Popescu, Sandu

    2014-06-01

    Thermodynamics is traditionally concerned with systems comprised of a large number of particles. Here we present a framework for extending thermodynamics to individual quantum systems, including explicitly a thermal bath and work-storage device (essentially a ‘weight’ that can be raised or lowered). We prove that the second law of thermodynamics holds in our framework, and gives a simple protocol to extract the optimal amount of work from the system, equal to its change in free energy. Our results apply to any quantum system in an arbitrary initial state, in particular including non-equilibrium situations. The optimal protocol is essentially reversible, similar to classical Carnot cycles, and indeed, we show that it can be used to construct a quantum Carnot engine.

  12. Preliminary thermodynamic study of regenerative Otto based cycles with zero NOx emissions operating with adiabatic and polytropic expansion

    International Nuclear Information System (INIS)

    Garcia, Ramon Ferreiro; Carril, Jose Carbia; Romero Gomez, Javier; Romero Gomez, Manuel

    2016-01-01

    Highlights: • Efficient polytropic expansion based Otto cycle. • Thermal efficiency is due to the inherent regeneration. • Low temperature combustion with zero NOx emissions. - Abstract: The aim of the paper is to demonstrate that a regenerative Otto cycle with adiabatic or polytropic expansion can achieve improved performance over traditional Otto engines, even exceeding the Carnot factor. Thus, the work deals with a novel regenerative Otto based internal combustion engine which differs from the conventional Otto thermal cycles in that the process of heat conversion into mechanical work is performed obeying a polytropic path function instead of the conventional adiabatic expansion without regeneration. Design characteristics concern the fact that combustion at constant volume is carried out undergoing large air excess so that the top combustion temperature is significantly lower than in conventional Otto cycles and consequently NOx emissions are neglected. Furthermore, during the polytropic expansion based path function, heat is absorbed by being submitted to a controlled heat flow rate, to achieve the desired polytropic expansion. The analysis of the regenerative Otto based on polytropic expansion is presented and results are compared with a regenerative Otto based on the adiabatic expansion and CF. The results show that a relevant advantage of the proposed regenerative Otto with polytropic expansion over the regenerative Otto cycle with adiabatic expansion involves performance enhancement within a wide range of combustion pressures, temperatures and regeneration capacities. Thus, thermal efficiency and specific work as function of the top combustion pressure ranges are of 71.95–58.43% and 143.5–173.6 kJ/kg respectively, when combustion pressures vary between 105 kPa and 200 kPa and CF is 60.8% (lower than the thermal efficiency). The successful results involving a compact engine structure, technically and economically viable, promises a new generation

  13. Design of closed-loop nitrogen Joule-Thomson refrigeration cycle for 67 K with sub-atmospheric device

    Energy Technology Data Exchange (ETDEWEB)

    Lee, C.; Lee, J.; Jeong, S. [Cryogenic Engineering Laboratory, Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2013-05-15

    Closed-loop J-T (Joule-Thomson) refrigeration cycle is advantageous compared to common open loop N{sub 2} decompression system in terms of nitrogen consumption. In this study, two closed-loop pure N{sub 2} J-T refrigeration systems with sub-atmospheric device for cooling High Temperature Superconductor (HTS) power cable are investigated. J-T cooling systems include 2-stage compressor, 2-stage precooling cycle, J-T valve and a cold compressor or an auxiliary vacuum pump at the room temperature. The cold compressor and the vacuum pump are installed after the J-T valve to create sub-atmospheric condition. The temperature of 67 K is possible by lowering the pressure up to 24 kPa at the cold part. The optimized hydrocarbon mixed refrigerant (MR) J-T system is applied for precooling stage. The cold head of precooling MR J-T have the temperature from 120 K to 150 K. The various characteristics of cold compressor are investigated and applied to design parameter of the cold compressor. The Carnot efficiency of cold compressor system is calculated as 16.7% and that of vacuum pump system as 16.4%. The efficiency difference between the cold compressor system and the vacuum pump system is due to difference of enthalpy change at cryogenic temperature, enthalpy change at room temperature and different work load at the pre-cooling cycle. The efficiency of neon-nitrogen MR J-T system is also presented for comparison with the sub-atmospheric devices. These systems have several pros and cons in comparison to typical MR J-T systems such as vacuum line maintainability, system's COP and etc. In this paper, the detailed design of the subcooled N{sub 2} J-T systems are examined and some practical issues of the sub-atmospheric devices are discussed.

  14. Chemistry of sustainable energy

    CERN Document Server

    Carpenter, Nancy E

    2014-01-01

    Energy BasicsWhat Is Energy?Energy, Technology, and SustainabilityEnergy Units, Terms, and AbbreviationsElectricity Generation and StorageOther ResourcesReferencesFossil FuelsFormation of Oil and GasExtraction of Fossil FuelsRefiningCarbon Capture and StorageSummaryOther ResourcesOnline Resources Related to Carbon Capture andSequestrationReferencesThermodynamicsIntroductionThe First Law of ThermodynamicsThe Second Law and Thermodynamic Cycles: the Carnot EfficiencyExerg

  15. Ideal cycle analysis of a regenerative pulse detonation engine for power production

    Science.gov (United States)

    Bellini, Rafaela

    can be obtained as a function of fuel-oxidizer ratio. The Humphrey and ZND cycles are studied in comparison with the Brayton cycle for different fuel-air mixtures such as methane, propane and hydrogen. The validity and limitations of the ZND and Humphrey cycles related to the detonation process are discussed and the criteria for the selection of the best model for the PDE cycle are explained. It is seen that the ZND cycle is a more appropriate representation of the PDE cycle. Next, the thermal and electrical power generation efficiencies for the PDE are compared with those of the deflagration based Brayton cycle. While the Brayton cycle shows an efficiency of 0 at a compressor pressure ratio of 1, the thermal efficiency for the ZND cycle starts out at 42% for hydrogen--air and then climbs to a peak of 66% at a compression ratio of 7 before falling slowly for higher compression ratios. The Brayton cycle efficiency rises above the PDEs for compression ratios above 23. This finding supports the theoretical advantage of PDEs over the gas turbines because PDEs only require a fan or only a few compressor stages, thereby eliminating the need for heavy compressor machinery, making the PDEs less complex and therefore more cost effective than other engines. Lastly, a regeneration study is presented to analyze how the use of exhaust gases can improve the performance of the system. The thermal efficiencies for the regenerative ZND cycle are compared with the efficiencies for the non--regenerative cycle. For a hydrogen--air mixture the thermal efficiency increases from 52%, for a cycle without regeneration, to 78%, for the regenerative cycle. The efficiency is compared with the Carnot efficiency of 84% which is the maximum possible theoretical efficiency of the cycle. When compared to the Brayton cycle thermal efficiencies, the regenerative cycle shows efficiencies that are always higher for the pressure ratio studied of 5 ≤ pic ≤ 25, where pi c the compressor pressure ratio

  16. Das CARNOTsche Paradigma und seine erkenntnistheoretischen Implikationen

    Science.gov (United States)

    Schöpf, Hans-Georg

    Der vorliegende historisch-kritische Essay führt die Eigentümlichkeiten der klassischen phänomenologischen Thermodynamik auf das von CARNOT geschaffene Paradigma zurück und greift einige damit zusammenhängende Fragen auf.Translated AbstractCARNOT's Paradigm and its Epistemological ImplicationsThe present historic-critical essay traces the pecularities of classical phenomenological thermodynamics back to the paradigm, created by CARNOT, and takes up some questions to which this paradigm gives rise.

  17. Exergy analysis for stationary flow systems with several heat exchange temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Lampinen, M J; Heikkinen, M A [Helsinki Univ. of Technology, Espoo (Finland). Dept. of Energy Engineering

    1995-07-01

    A thermodynamic theory of exergy analysis for a stationary flow system having several heat inputs and outputs at different temperature levels is presented. As a new result a relevant reference temperature of the surroundings is derived for each case. Also a general formula which combines exergy analysis with a modified Carnot efficiency is derived. The results are illustrated by numerical examples for mechanical multi-circuit heat pump cycles, for a Brayton process and for an absorption heat pump. (Author)

  18. Thermodynamic analysis of a novel energy-efficient refrigeration system subcooled by liquid desiccant dehumidification and evaporation

    International Nuclear Information System (INIS)

    She, Xiaohui; Yin, Yonggao; Zhang, Xiaosong

    2014-01-01

    Highlights: • An energy-efficient refrigeration system with a novel subcooling method is proposed. • Thermodynamic analysis is conducted to discuss the effects of operation parameters. • Two different utilization ways of condensation heat are compared. • The system achieves much higher COP, even higher than reverse Carnot cycle. • Suggested mass concentration for LiCl–H 2 O is around 32% at a typical case. - Abstract: A new energy-efficient refrigeration system subcooled by liquid desiccant dehumidification and evaporation was proposed in this paper. In the system, liquid desiccant system could produce very dry air for an indirect evaporative cooler, which would subcool the vapor compression refrigeration system to get higher COP than conventional refrigeration system. The desiccant cooling system can use the condensation heat for the desiccant regeneration. Thermodynamic analysis is made to discuss the effects of operation parameters (condensing temperature, liquid desiccant concentration, ambient air temperature and relative humidity) on the system performance. Results show that the proposed hybrid vapor compression refrigeration system achieves significantly higher COP than conventional vapor compression refrigeration system, and even higher than the reverse Carnot cycle at the same operation conditions. The maximum COPs of the hybrid systems using hot air and ambient air are 18.8% and 16.3% higher than that of the conventional vapor compression refrigeration system under varied conditions, respectively

  19. Transformation of heat into mechanical energy by means of rotating systems

    Directory of Open Access Journals (Sweden)

    Mešina Marian

    2018-01-01

    Full Text Available All heat engines need two different temperatures for their work, T1Carnot formula from above. This article presents a new conception for heat engines. Unlike conventional heat engines, the working medium has an additional degree of freedom, the rotation around a given axis. The heat introduced and removed can not only lead to a change in the parameters of temperature, pressure, and volume, which are considered in conventional thermodynamics, but also to a change in the state of rotation. The rotational speed must also be taken into account in all phases of the cycle for all efficiency calculations. In many cases, this leads to a surprisingly different result from the results of conventional thermodynamics, that the efficiency of the cycle can exceed the Carnot limit. The efficiency values depend not only on temperatures and rotational speeds, but also on the material data. The proposed new type of heat engine makes it possible to better utilise very small temperature differences and under certain conditions, in combination with an ideal heat pump, to extract ambient heat and convert it into mechanical energy. The calculated results were presented for simple geometry and can easily be verified experimentally. In combination with an ideal heat pump, the proposed heat engine facilitates the surroundings to withdraw heat and convert it into mechanical work.

  20. The Proell Effect: A Macroscopic Maxwell's Demon

    Science.gov (United States)

    Rauen, Kenneth M.

    2011-12-01

    Maxwell's Demon is a legitimate challenge to the Second Law of Thermodynamics when the "demon" is executed via the Proell effect. Thermal energy transfer according to the Kinetic Theory of Heat and Statistical Mechanics that takes place over distances greater than the mean free path of a gas circumvents the microscopic randomness that leads to macroscopic irreversibility. No information is required to sort the particles as no sorting occurs; the entire volume of gas undergoes the same transition. The Proell effect achieves quasi-spontaneous thermal separation without sorting by the perturbation of a heterogeneous constant volume system with displacement and regeneration. The classical analysis of the constant volume process, such as found in the Stirling Cycle, is incomplete and therefore incorrect. There are extra energy flows that classical thermo does not recognize. When a working fluid is displaced across a regenerator with a temperature gradient in a constant volume system, complimentary compression and expansion work takes place that transfers energy between the regenerator and the bulk gas volumes of the hot and cold sides of the constant volume system. Heat capacity at constant pressure applies instead of heat capacity at constant volume. The resultant increase in calculated, recyclable energy allows the Carnot Limit to be exceeded in certain cycles. Super-Carnot heat engines and heat pumps have been designed and a US patent has been awarded.

  1. Entransy loss in thermodynamic processes and its application

    International Nuclear Information System (INIS)

    Cheng, Xuetao; Liang, Xingang

    2012-01-01

    The entransy theory has been developed for heat transfer optimization. This paper extends it to optimize thermodynamic processes. The entransy balance equation of thermodynamic processes is introduced, with which the concept of entransy loss is developed. For the Carnot cycle and the irreversible thermodynamic processes where the working fluid is heated by the streams with prescribed inlet temperatures and specific capacity flow rates, we find that the maximum entransy loss leads to the maximum output work, which is the maximum principle of entransy loss in thermodynamic processes. However, the entropy generation cannot describe the change of the output work for the Carnot cycle. Therefore, the concept of entransy loss could describe the performance of thermodynamic processes. Then, the principle is used to optimize the thermodynamic processes of heat exchanger groups and the design of the irreversible Brayton cycle. For these problems, the operation parameters are optimized to get the maximum output work by calculating the maximum entransy loss when the entransy loss induced by dumping the used streams into the environment is considered. The analysis of the air conditioning system for room heating with heat–work conversion processes demonstrates the entransy loss has a direct relation with the input heat. -- Highlights: ► The entransy balance equation of thermodynamic processes is introduced. ► The concept of entransy loss is developed. ► The maximum entransy loss corresponds to the maximum output work. ► Examples show that entransy loss can be used to optimize heat–work conversion.

  2. Introduction to statistical physics

    CERN Document Server

    Huang, Kerson

    2009-01-01

    A Macroscopic View of MatterViewing the World at Different Scales Thermodynamics The Thermodynamic Limit Thermodynamic TransformationsClassic Ideal Gas First Law of Thermodynamics Magnetic SystemsHeat and EntropyThe Heat Equations Applications to Ideal Gas Carnot Cycle Second Law of Thermodynamics Absolute Temperature Temperature as Integrating Factor EntropyEntropy of Ideal Gas The Limits of ThermodynamicsUsing ThermodynamicsThe Energy EquationSome Measurable Coefficients Entropy and Loss TS Diagram Condition for Equilibrium Helmholtz Free EnergyGibbs Potential Maxwell Relations Chemical Pote

  3. Shape memory heat engines

    Science.gov (United States)

    Salzbrenner, R.

    1984-06-01

    The mechanical shape memory effect associated with a thermoelastic martensitic transformation can be used to convert heat directly into mechanical work. Laboratory simulation of two types of heat engine cycles (Stirling and Ericsson) has been performed to measure the amount of work available/cycle in a Ni-45 at. pct Ti alloy. Tensile deformations at ambient temperature induced martensite, while a subsequent increase in temperature caused a reversion to the parent phase during which a load was carried through the strain recovery (i.e., work was accomplished). The amount of heat necessary to carry the engines through a cycle was estimated from calorimeter measurements and the work performed/cycle. The measured efficiency of the system tested reached a maximum of 1.4 percent, which was well below the theoretical (Carnot) maximum efficiency of 35.6 percent.

  4. On the dynamical vs. thermodynamical performance of a β-type Stirling engine

    Science.gov (United States)

    Reséndiz-Antonio, Margarita; Santillán, Moisés

    2014-09-01

    In this work we present a simple mathematical model for a β-type Stirling engine. Despite its simplicity, the model considers all the engine’s relevant thermodynamic and mechanical aspects. The dynamic behavior of the model equation of motion is analyzed in order to obtain the sufficient conditions for engine cycling and to study the stability of the stationary regime. The performance of the engine’s thermodynamic part is also investigated. As a matter of fact, we found that it corresponds to a Carnot engine.

  5. Thermodynamics

    CERN Document Server

    Fermi, Enrico

    1956-01-01

    Indisputably, this is a modern classic of science. Based on a course of lectures delivered by the author at Columbia University, the text is elementary in treatment and remarkable for its clarity and organization. Although it is assumed that the reader is familiar with the fundamental facts of thermometry and calorimetry, no advanced mathematics beyond calculus is assumed.Partial contents: thermodynamic systems, the first law of thermodynamics (application, adiabatic transformations), the second law of thermodynamics (Carnot cycle, absolute thermodynamic temperature, thermal engines), the entr

  6. Equivalent Temperature-Enthalpy Diagram for the Study of Ejector Refrigeration Systems

    Directory of Open Access Journals (Sweden)

    Mohammed Khennich

    2014-05-01

    Full Text Available The Carnot factor versus enthalpy variation (heat diagram has been used extensively for the second law analysis of heat transfer processes. With enthalpy variation (heat as the abscissa and the Carnot factor as the ordinate the area between the curves representing the heat exchanging media on this diagram illustrates the exergy losses due to the transfer. It is also possible to draw the paths of working fluids in steady-state, steady-flow thermodynamic cycles on this diagram using the definition of “the equivalent temperature” as the ratio between the variations of enthalpy and entropy in an analyzed process. Despite the usefulness of this approach two important shortcomings should be emphasized. First, the approach is not applicable for the processes of expansion and compression particularly for the isenthalpic processes taking place in expansion valves. Second, from the point of view of rigorous thermodynamics, the proposed ratio gives the temperature dimension for the isobaric processes only. The present paper proposes to overcome these shortcomings by replacing the actual processes of expansion and compression by combinations of two thermodynamic paths: isentropic and isobaric. As a result the actual (not ideal refrigeration and power cycles can be presented on equivalent temperature versus enthalpy variation diagrams. All the exergy losses, taking place in different equipments like pumps, turbines, compressors, expansion valves, condensers and evaporators are then clearly visualized. Moreover the exergies consumed and produced in each component of these cycles are also presented. The latter give the opportunity to also analyze the exergy efficiencies of the components. The proposed diagram is finally applied for the second law analysis of an ejector based refrigeration system.

  7. Technology of nuclear reactors

    International Nuclear Information System (INIS)

    Ravelet, F.

    2016-01-01

    This academic report for graduation in engineering first presents operation principles of a nuclear reactor core. It presents core components, atomic nuclei, the notions of transmutation and radioactivity, quantities used to characterize ionizing radiations, the nuclear fission, statistical aspects of fission and differences between fast and slow neutrons, a comparison between various heat transfer fluids, the uranium enrichment process, and different types of reactor (boiling water, natural uranium and heavy water, pressurized water, and fourth generation). Then, after having recalled the French installed power, the author proposes an analysis of a typical 900 MWe nuclear power plant: primary circuit, reactor, fuel, spent fuel, pressurizer and primary pump, secondary circuit, aspects related to control-command, regulation, safety and exploitation. The last part proposes a modelling of the thermodynamic cycle of a pressurized water plant by using an equivalent Carnot cycle, a Rankine cycle, and a two-phase expansion cycle with drying-overheating

  8. Performance of a multilevel quantum heat engine of an ideal N-particle Fermi system.

    Science.gov (United States)

    Wang, Rui; Wang, Jianhui; He, Jizhou; Ma, Yongli

    2012-08-01

    We generalize the quantum heat engine (QHE) model which was first proposed by Bender et al. [J. Phys. A 33, 4427 (2000)] to the case in which an ideal Fermi gas with an arbitrary number N of particles in a box trap is used as the working substance. Besides two quantum adiabatic processes, the engine model contains two isoenergetic processes, during which the particles are coupled to energy baths at a high constant energy E(h) and a low constant energy E(c), respectively. Directly employing the finite-time thermodynamics, we find that the power output is enhanced by increasing particle number N (or decreasing minimum trap size L(A)) for given L(A) (or N), without reduction in the efficiency. By use of global optimization, the efficiency at possible maximum power output (EPMP) is found to be universal and independent of any parameter contained in the engine model. For an engine model with any particle-number N, the efficiency at maximum power output (EMP) can be determined under the condition that it should be closest to the EPMP. Moreover, we extend the heat engine to a more general multilevel engine model with an arbitrary 1D power-law potential. Comparison between our engine model and the Carnot cycle shows that, under the same conditions, the efficiency η = 1 - E(c)/E(h) of the engine cycle is bounded from above the Carnot value η(c) =1 - T(c)/T(h).

  9. Rotary magnetic refrigerator for superfluid helium production

    International Nuclear Information System (INIS)

    Hakuraku, Y.; Ogata, H.

    1986-01-01

    A new rotary-magnetic refrigerator designed to obtain superfluid helium temperatures by executing a magnetic Carnot cycle is developed. A rotor containing 12 magnetic refrigerants (gadolinium-gallium-garnet) is immersed in liquid helium at 4.2 K and rotated at constant speed in a steady magnetic field distribution. Performance tests demonstrate that the new rotary refrigerator is capable of obtaining a temperature of 1.48 K. The maximum useful cooling power obtained at 1.8 K is 1.81 W which corresponds to a refrigeration efficiency of 34%

  10. Sulle orme di Carnot

    CERN Document Server

    Carrà, Sergio

    2011-01-01

    L'energia e le sue trasformazioni ; impieghi e rendimenti dell'energia termica ; l'energia elettromagnetica ; l'energia elettrochimica ; natura delle fonti energetiche ; l'energia nucleare ; disponibilità e impieghi dell'energia ; energetica della biosfera ; energia, risorse e ambiente ; cercasi miracolo disperatamente.

  11. Performance characteristics of a methanol ejector refrigeration unit

    International Nuclear Information System (INIS)

    Alexis, G.K.; Katsanis, J.S.

    2004-01-01

    This paper discusses the behavior of methanol through an ejector operating in a refrigeration system with a medium temperature thermal source. For detailed calculation of the proposed system, a method has been developed, which employs analytical functions describing the thermodynamic properties of methanol. The proposed cycle has been compared with a Carnot cycle working at the same temperature levels. The influences of three major parameters, generator, condenser and evaporator temperatures, on ejector efficiency and coefficient of performance are discussed. Also, the maximum value of COP was estimated by correlation of the above three temperatures for constant superheated temperature 150 deg. C, and it was 0.139-0.467. The design conditions were generator temperature 117.7-132.5 deg. C, condenser temperature 42-50 deg. C and evaporator temperature -10-5 deg. C

  12. The Second Law of Thermodynamics in a Quantum Heat Engine Model

    International Nuclear Information System (INIS)

    Zhang Ting; Cai Lifeng; Chen Pingxing; Li Chengzu

    2006-01-01

    The second law of thermodynamics has been proven by many facts in classical world. Is there any new property of it in quantum world? In this paper, we calculate the change of entropy in T.D. Kieu's model for quantum heat engine (QHE) and prove the broad validity of the second law of thermodynamics. It is shown that the entropy of the quantum heat engine neither decreases in a whole cycle, nor decreases in either stage of the cycle. The second law of thermodynamics still holds in this QHE model. Moreover, although the modified quantum heat engine is capable of extracting more work, its efficiency does not improve at all. It is neither beyond the efficiency of T.D. Kieu's initial model, nor greater than the reversible Carnot efficiency.

  13. Size dependence of efficiency at maximum power of heat engine

    KAUST Repository

    Izumida, Y.; Ito, N.

    2013-01-01

    We perform a molecular dynamics computer simulation of a heat engine model to study how the engine size difference affects its performance. Upon tactically increasing the size of the model anisotropically, we determine that there exists an optimum size at which the model attains the maximum power for the shortest working period. This optimum size locates between the ballistic heat transport region and the diffusive heat transport one. We also study the size dependence of the efficiency at the maximum power. Interestingly, we find that the efficiency at the maximum power around the optimum size attains a value that has been proposed as a universal upper bound, and it even begins to exceed the bound as the size further increases. We explain this behavior of the efficiency at maximum power by using a linear response theory for the heat engine operating under a finite working period, which naturally extends the low-dissipation Carnot cycle model [M. Esposito, R. Kawai, K. Lindenberg, C. Van den Broeck, Phys. Rev. Lett. 105, 150603 (2010)]. The theory also shows that the efficiency at the maximum power under an extreme condition may reach the Carnot efficiency in principle.© EDP Sciences Società Italiana di Fisica Springer-Verlag 2013.

  14. Size dependence of efficiency at maximum power of heat engine

    KAUST Repository

    Izumida, Y.

    2013-10-01

    We perform a molecular dynamics computer simulation of a heat engine model to study how the engine size difference affects its performance. Upon tactically increasing the size of the model anisotropically, we determine that there exists an optimum size at which the model attains the maximum power for the shortest working period. This optimum size locates between the ballistic heat transport region and the diffusive heat transport one. We also study the size dependence of the efficiency at the maximum power. Interestingly, we find that the efficiency at the maximum power around the optimum size attains a value that has been proposed as a universal upper bound, and it even begins to exceed the bound as the size further increases. We explain this behavior of the efficiency at maximum power by using a linear response theory for the heat engine operating under a finite working period, which naturally extends the low-dissipation Carnot cycle model [M. Esposito, R. Kawai, K. Lindenberg, C. Van den Broeck, Phys. Rev. Lett. 105, 150603 (2010)]. The theory also shows that the efficiency at the maximum power under an extreme condition may reach the Carnot efficiency in principle.© EDP Sciences Società Italiana di Fisica Springer-Verlag 2013.

  15. Bipolar mood cycles and lunar tidal cycles.

    Science.gov (United States)

    Wehr, T A

    2018-04-01

    In 17 patients with rapid cycling bipolar disorder, time-series analyses detected synchronies between mood cycles and three lunar cycles that modulate the amplitude of the moon's semi-diurnal gravimetric tides: the 14.8-day spring-neap cycle, the 13.7-day declination cycle and the 206-day cycle of perigee-syzygies ('supermoons'). The analyses also revealed shifts among 1:2, 1:3, 2:3 and other modes of coupling of mood cycles to the two bi-weekly lunar cycles. These shifts appear to be responses to the conflicting demands of the mood cycles' being entrained simultaneously to two different bi-weekly lunar cycles with slightly different periods. Measurements of circadian rhythms in body temperature suggest a biological mechanism through which transits of one of the moon's semi-diurnal gravimetric tides might have driven the patients' bipolar cycles, by periodically entraining the circadian pacemaker to its 24.84-h rhythm and altering the pacemaker's phase-relationship to sleep in a manner that is known to cause switches from depression to mania.

  16. The Krebs Uric Acid Cycle: A Forgotten Krebs Cycle.

    Science.gov (United States)

    Salway, Jack G

    2018-05-25

    Hans Kornberg wrote a paper entitled 'Krebs and his trinity of cycles' commenting that every school biology student knows of the Krebs cycle, but few know that Krebs discovered two other cycles. These are (i) the ornithine cycle (urea cycle), (ii) the citric acid cycle (tricarboxylic acid or TCA cycle), and (iii) the glyoxylate cycle that was described by Krebs and Kornberg. Ironically, Kornberg, codiscoverer of the 'glyoxylate cycle', overlooked a fourth Krebs cycle - (iv) the uric acid cycle. Copyright © 2018 Elsevier Ltd. All rights reserved.

  17. Novel thermoenvironmental evaluation criteria and comparing them for an actual heat engine

    International Nuclear Information System (INIS)

    Özel, Gülcan; Açıkkalp, Emin; Savaş, Ahmet Fevzi; Yamık, Hasan

    2015-01-01

    Highlights: • An irreversible Carnot cycle is considered. • Novel thermoenvironmental criteria are presented. • Calculation are conducted for irreversible cycles. • Numerical results are presented and discussed. - Abstract: In the present study, environmental impact analysis is used for the optimization to an actual heat engine. Four new thermoenvironmental evaluation criteria called as thermoenvironmental function, ecological based thermoenvironmental function, ecologicoenvironmental function and finite time exergoenvironmental criteria are developed and compared with the each other. Ecologicoenvironmental function is used to determine environmental impact at the maximum ecological function. It is defined as the most suitable criteria for an actual heat engine. Because, it has lower irreversibilities compared with others, its work output is equal to 90% of the maximum work and 60% energy efficiency at the optimum point and exergy destruction is lower than others at the optimum point.

  18. Quantum Stirling heat engine and refrigerator with single and coupled spin systems

    Science.gov (United States)

    Huang, Xiao-Li; Niu, Xin-Ya; Xiu, Xiao-Ming; Yi, Xue-Xi

    2014-02-01

    We study the reversible quantum Stirling cycle with a single spin or two coupled spins as the working substance. With the single spin as the working substance, we find that under certain conditions the reversed cycle of a heat engine is NOT a refrigerator, this feature holds true for a Stirling heat engine with an ion trapped in a shallow potential as its working substance. The efficiency of quantum Stirling heat engine can be higher than the efficiency of the Carnot engine, but the performance coefficient of the quantum Stirling refrigerator is always lower than its classical counterpart. With two coupled spins as the working substance, we find that a heat engine can turn to a refrigerator due to the increasing of the coupling constant, this can be explained by the properties of the isothermal line in the magnetic field-entropy plane.

  19. On the influence of thermal hysteresis on the performance of thermomagnetic motors

    Science.gov (United States)

    Bessa, C. V. X.; Ferreira, L. D. R.; Horikawa, O.; Monteiro, J. C. B.; Gandra, F. G.; Gama, S.

    2017-12-01

    Although thermal hysteresis might be a problem in the magnetocaloric refrigeration, the same is not necessarily true for thermomagnetic motor applications. This work presents a comparison of the magnetocaloric properties of materials with first order magnetic transition (having large or narrow thermal hysteresis) to those with second order magnetic transition, assessing the application of these materials in thermomagnetic motors through a thermodynamic approach. Results show that the larger the thermal hysteresis, the higher the specific work produced in a thermal cycle. This allows operation at higher temperature differences with high efficiency relative to Carnot efficiency, when compared with systems using narrow hysteresis and second order transition materials.

  20. Mathematical modeling of the Stirling engine in terms of applying the composition of the power complex containing non-conventional and renewable energy

    Science.gov (United States)

    Gaponenko, A. M.; Kagramanova, A. A.

    2017-11-01

    The opportunity of application of Stirling engine with non-conventional and renewable sources of energy. The advantage of such use. The resulting expression for the thermal efficiency of the Stirling engine. It is shown that the work per cycle is proportional to the quantity of matter, and hence the pressure of the working fluid, the temperature difference and, to a lesser extent, depends on the expansion coefficient; efficiency of ideal Stirling cycle coincides with the efficiency of an ideal engine working on the Carnot cycle, which distinguishes a Stirling cycle from the cycles of Otto and Diesel underlying engine. It has been established that the four input parameters, the only parameter which can be easily changed during operation, and which effectively affects the operation of the engine is the phase difference. Dependence of work per cycle of the phase difference, called the phase characteristic, visually illustrates mode of operation of Stirling engine. The mathematical model of the cycle of Schmidt and the analysis of operation of Stirling engine in the approach of Schmidt with the aid of numerical analysis. To conduct numerical experiments designed program feature in the language MathLab. The results of numerical experiments are illustrated by graphical charts.

  1. Pythagorean Means and Carnot Machines

    Indian Academy of Sciences (India)

    When Music Meets Heat. Ramandeep S Johal ... found their use in representing ratios on a musical scale (see Box. 1). There are ... two legs of a journey, spending equal time t in each of them, .... a pump between Ti and Tc, and require that Rhi = Pic. This ... We can make similar statements, when the machines in case are.

  2. Alternative ORC bottoming cycles FOR combined cycle power plants

    International Nuclear Information System (INIS)

    Chacartegui, R.; Sanchez, D.; Munoz, J.M.; Sanchez, T.

    2009-01-01

    In this work, low temperature Organic Rankine Cycles are studied as bottoming cycle in medium and large scale combined cycle power plants. The analysis aims to show the interest of using these alternative cycles with high efficiency heavy duty gas turbines, for example recuperative gas turbines with lower gas turbine exhaust temperatures than in conventional combined cycle gas turbines. The following organic fluids have been considered: R113, R245, isobutene, toluene, cyclohexane and isopentane. Competitive results have been obtained for toluene and cyclohexane ORC combined cycles, with reasonably high global efficiencies. The paper is structured in four main parts. A review of combined cycle and ORC cycle technologies is presented, followed by a thermodynamic analysis of combined cycles with commercial gas turbines and ORC low temperature bottoming cycles. Then, a parametric optimization of an ORC combined cycle plant is performed in order to achieve a better integration between these two technologies. Finally, some economic considerations related to the use of ORC in combined cycles are discussed.

  3. Cycling infrastructure for reducing cycling injuries in cyclists.

    Science.gov (United States)

    Mulvaney, Caroline A; Smith, Sherie; Watson, Michael C; Parkin, John; Coupland, Carol; Miller, Philip; Kendrick, Denise; McClintock, Hugh

    2015-12-10

    Cycling is an attractive form of transport. It is beneficial to the individual as a form of physical activity that may fit more readily into an individual's daily routine, such as for cycling to work and to the shops, than other physical activities such as visiting a gym. Cycling is also beneficial to the wider community and the environment as a result of fewer motorised journeys. Cyclists are seen as vulnerable road users who are frequently in close proximity to larger and faster motorised vehicles. Cycling infrastructure aims to make cycling both more convenient and safer for cyclists. This review is needed to guide transport planning. To:1. evaluate the effects of different types of cycling infrastructure on reducing cycling injuries in cyclists, by type of infrastructure;2. evaluate the effects of cycling infrastructure on reducing the severity of cycling injuries in cyclists;3. evaluate the effects of cycling infrastructure on reducing cycling injuries in cyclists with respect to age, sex and social group. We ran the most recent search on 2nd March 2015. We searched the Cochrane Injuries Group Specialised Register, CENTRAL (The Cochrane Library), MEDLINE (OvidSP), Embase Classic + Embase(OvidSP), PubMed and 10 other databases. We searched websites, handsearched conference proceedings, screened reference lists of included studies and previously published reviews and contacted relevant organisations. We included randomised controlled trials, cluster randomised controlled trials, controlled before-after studies, and interrupted time series studies which evaluated the effect of cycling infrastructure (such as cycle lanes, tracks or paths, speed management, roundabout design) on cyclist injury or collision rates. Studies had to include a comparator, that is, either no infrastructure or a different type of infrastructure. We excluded studies that assessed collisions that occurred as a result of competitive cycling. Two review authors examined the titles and

  4. Optimum gas turbine cycle for combined cycle power plant

    International Nuclear Information System (INIS)

    Polyzakis, A.L.; Koroneos, C.; Xydis, G.

    2008-01-01

    The gas turbine based power plant is characterized by its relatively low capital cost compared with the steam power plant. It has environmental advantages and short construction lead time. However, conventional industrial engines have lower efficiencies, especially at part load. One of the technologies adopted nowadays for efficiency improvement is the 'combined cycle'. The combined cycle technology is now well established and offers superior efficiency to any of the competing gas turbine based systems that are likely to be available in the medium term for large scale power generation applications. This paper has as objective the optimization of a combined cycle power plant describing and comparing four different gas turbine cycles: simple cycle, intercooled cycle, reheated cycle and intercooled and reheated cycle. The proposed combined cycle plant would produce 300 MW of power (200 MW from the gas turbine and 100 MW from the steam turbine). The results showed that the reheated gas turbine is the most desirable overall, mainly because of its high turbine exhaust gas temperature and resulting high thermal efficiency of the bottoming steam cycle. The optimal gas turbine (GT) cycle will lead to a more efficient combined cycle power plant (CCPP), and this will result in great savings. The initial approach adopted is to investigate independently the four theoretically possible configurations of the gas plant. On the basis of combining these with a single pressure Rankine cycle, the optimum gas scheme is found. Once the gas turbine is selected, the next step is to investigate the impact of the steam cycle design and parameters on the overall performance of the plant, in order to choose the combined cycle offering the best fit with the objectives of the work as depicted above. Each alterative cycle was studied, aiming to find the best option from the standpoint of overall efficiency, installation and operational costs, maintainability and reliability for a combined power

  5. Cycles and Common Cycles in Property and Related Sectors

    OpenAIRE

    Peijie Wang

    2003-01-01

    This paper examines cycles and common cycles in the property market and the economy. While focusing on common cycles, the study also incorporates common trends in the meantime, so it covers the whole spectrum of dynamic analysis. It has been found that property shares common cycles, particularly with those sectors that are the user markets of property. The mechanisms of common cycles and the relative magnitudes of cycles of the sectors related to property are discussed to shed light on proper...

  6. SAGD CO2 mitigation through energy efficiency improvements

    International Nuclear Information System (INIS)

    Plessis du, D.

    2010-01-01

    An evaluation of the carbon dioxide (CO 2 ) emissions reductions achieved using energy efficiency measures in steam assisted gravity drainage (SAGD) operations was presented. The efficiency of a typical SAGD operation was analyzed using an indexing tool based on the Carnot cycle efficiency to develop an ideal SAGD heat cycle. The benefits of using an organic Rankine cycle (ORC) technology to convert waste heat to electrical power were also investigated. A CO 2 abatement curve was used to identify the economic benefits and costs of various greenhouse gas (GHG) reductions. The level of recovered energy was determined in relation to energy prices, capital costs, and carbon penalties in order to determine the most efficient means of decreasing energy usage. The study demonstrated that energy efficiency can be improved by up to 20 percent, and water loss reductions of up to 50 percent can be achieved using cost-effective energy efficiency measures. Results of the study can be used to guide government policy and provide industry with practical tools to benchmark performance and improve efficiencies. 4 refs., 1 tab., 10 figs.

  7. Stochastic control and the second law of thermodynamics

    Science.gov (United States)

    Brockett, R. W.; Willems, J. C.

    1979-01-01

    The second law of thermodynamics is studied from the point of view of stochastic control theory. We find that the feedback control laws which are of interest are those which depend only on average values, and not on sample path behavior. We are lead to a criterion which, when satisfied, permits one to assign a temperature to a stochastic system in such a way as to have Carnot cycles be the optimal trajectories of optimal control problems. Entropy is also defined and we are able to prove an equipartition of energy theorem using this definition of temperature. Our formulation allows one to treat irreversibility in a quite natural and completely precise way.

  8. HCl removal using cycled carbide slag from calcium looping cycles

    International Nuclear Information System (INIS)

    Xie, Xin; Li, Yingjie; Wang, Wenjing; Shi, Lei

    2014-01-01

    Highlights: • Cycled carbide slag from calcium looping cycles is used to remove HCl. • The optimum temperature for HCl removal of cycled carbide slag is 700 °C. • The presence of CO 2 restrains HCl removal of cycled carbide slag. • CO 2 capture conditions have important effects on HCl removal of cycled carbide slag. • HCl removal capacity of carbide slag drops with cycle number rising from 1 to 50. - Abstract: The carbide slag is an industrial waste from chlor-alkali plants, which can be used to capture CO 2 in the calcium looping cycles, i.e. carbonation/calcination cycles. In this work, the cycled carbide slag from the calcium looping cycles for CO 2 capture was proposed to remove HCl in the flue gas from the biomass-fired and RDFs-fired boilers. The effects of chlorination temperature, HCl concentration, particle size, presence of CO 2 , presence of O 2 , cycle number and CO 2 capture conditions in calcium looping cycles on the HCl removal behavior of the carbide slag experienced carbonation/calcination cycles were investigated in a triple fixed-bed reactor. The chlorination product of the cycled carbide slag from the calcium looping after absorbing HCl is not CaCl 2 but CaClOH. The optimum temperature for HCl removal of the cycled carbide slag from the carbonation/calcination cycles is 700 °C. The chlorination conversion of the cycled carbide slag increases with increasing the HCl concentration. The cycled carbide slag with larger particle size exhibits a lower chlorination conversion. The presence of CO 2 decreases the chlorination conversions of the cycled carbide slag and the presence of O 2 has a trifling impact. The chlorination conversion of the carbide slag experienced 1 carbonation/calcination cycle is higher than that of the uncycled calcined sorbent. As the number of carbonation/calcination cycles increases from 1 to 50, the chlorination conversion of carbide slag drops gradually. The high calcination temperature and high CO 2

  9. Monsieur Omar Fassi Fihri Secrétaire perpétuel Académie HASSAN II des Sciences et Techniques Royaume du Maroc

    CERN Document Server

    Maximilien Brice

    2010-01-01

    CERN-HI-1007135 01: M. Gouighri, Boursier de l’Académie des Sciences, Université Hassan II; J. Collot, Directeur du Laboratoire international associé; R. Heuer,\tDirecteur général du CERN;O. Fassi Fehri, Secrétaire perpétuel, Académie Hassan II des Sciences et Techniques, Maroc; S. Boutouil, Boursière du Laboratoire international associé; R. Klapisch, Fondation Partager le Savoir, Président et fondateur; G.Carnot, Président de la Fondation Carnot.

  10. Assessment of the Bordas-Carnot Losses within the diffuser of tidal turbines using far-field and near-field CFD models.

    Science.gov (United States)

    Hajaali, Arthur

    2017-04-01

    This project has for ambition to analyse and further the general understanding on cross-flows interactions and behaviours at the mouth of a mini/small tidal hydropower plant and a river. Although, the study of these interactions could benefit and find applications in multiple hydraulic problems, this project concentrates its focus on the influence of the transposed turbulences generated by the cross-flow into the diffuser. These eddies affect the overall performance and efficiency of the bulb-turbines by minimizing the pressure recovery. In the past, these turbulences were accounted with the implementation of the Bordas-Carnot losses coefficient for the design of tidal project using bulb-turbines. The bulb turbine technology has been the interest and subject of many scientific papers but most of them concentrate and narrow their focus on the design of the rotor, blades and combiner. This project wants to focus the design of the diffuser by performing an analysis on the development of eddies and the turbulences using computational fluid dynamic (CFD) models. The Severn estuary is endowed with one of the highest tidal range around the hemisphere. The first part of the research requires to select case studies sites such as Briton-Ferry to virtually design mini-tidal plant in 0-Dimentional (D), 2D and 3D modelling to study development and behaviour of turbulences within the diffuser. The far-field model represents the marine environment prior and after the structure where bulb turbines are located. The near-field modelling has allowed researcher to study at much higher resolution and precision the design of a single turbine feeding model with predetermined and fix boundary condition. For this reason, a near-field model is required to study in depth the behaviour and evolution of the turbulence with the diffuser. One of the main challenge and advancement of this research is to find a methodology and system to link the far-field and near-field modelling to produce an

  11. Will Solar Cycles 25 and 26 Be Weaker than Cycle 24?

    Science.gov (United States)

    Javaraiah, J.

    2017-11-01

    The study of variations in solar activity is important for understanding the underlying mechanism of solar activity and for predicting the level of activity in view of the activity impact on space weather and global climate. Here we have used the amplitudes (the peak values of the 13-month smoothed international sunspot number) of Solar Cycles 1 - 24 to predict the relative amplitudes of the solar cycles during the rising phase of the upcoming Gleissberg cycle. We fitted a cosine function to the amplitudes and times of the solar cycles after subtracting a linear fit of the amplitudes. The best cosine fit shows overall properties (periods, maxima, minima, etc.) of Gleissberg cycles, but with large uncertainties. We obtain a pattern of the rising phase of the upcoming Gleissberg cycle, but there is considerable ambiguity. Using the epochs of violations of the Gnevyshev-Ohl rule (G-O rule) and the `tentative inverse G-O rule' of solar cycles during the period 1610 - 2015, and also using the epochs where the orbital angular momentum of the Sun is steeply decreased during the period 1600 - 2099, we infer that Solar Cycle 25 will be weaker than Cycle 24. Cycles 25 and 26 will have almost same strength, and their epochs are at the minimum between the current and upcoming Gleissberg cycles. In addition, Cycle 27 is expected to be stronger than Cycle 26 and weaker than Cycle 28, and Cycle 29 is expected to be stronger than both Cycles 28 and 30. The maximum of Cycle 29 is expected to represent the next Gleissberg maximum. Our analysis also suggests a much lower value (30 - 40) for the maximum amplitude of the upcoming Cycle 25.

  12. Culture in cycles: considering H.T. Odum's 'information cycle'

    Science.gov (United States)

    Abel, Thomas

    2014-01-01

    'Culture' remains a conundrum in anthropology. When recast in the mold of 'information cycles,' culture is transformed. New fault lines appear. Information is splintered into parallel or nested forms. Dynamics becomes cycling. Energy is essential. And culture has function in a directional universe. The 'information cycle' is the crowning component of H.T. Odum's theory of general systems. What follows is an application of the information cycle to the cultural domains of discourse, social media, ritual, education, journalism, technology, academia, and law, which were never attempted by Odum. In information cycles, cultural information is perpetuated - maintained against Second Law depreciation. Conclusions are that culture is in fact a nested hierarchy of cultural forms. Each scale of information production is semi-autonomous, with its own evolutionary dynamics of production and selection in an information cycle. Simultaneously, each information cycle is channeled or entrained by its larger scale of information and ultimately human-ecosystem structuring.

  13. Dissipation of 'dark energy' by cortex in knowledge retrieval.

    Science.gov (United States)

    Capolupo, Antonio; Freeman, Walter J; Vitiello, Giuseppe

    2013-03-01

    We have devised a thermodynamic model of cortical neurodynamics expressed at the classical level by neural networks and at the quantum level by dissipative quantum field theory. Our model is based on features in the spatial images of cortical activity newly revealed by high-density electrode arrays. We have incorporated the mechanism and necessity for so-called dark energy in knowledge retrieval. We have extended the model first using the Carnot cycle to define our measures for energy, entropy and temperature, and then using the Rankine cycle to incorporate criticality and phase transitions. We describe the dynamics of two interactive fields of neural activity that express knowledge, one at high and the other at low energy density, and the two operators that create and annihilate the fields. We postulate that the extremely high density of energy sequestered briefly in cortical activity patterns can account for the vividness, richness of associations, and emotional intensity of memories recalled by stimuli. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. Proliferation in cycle

    Energy Technology Data Exchange (ETDEWEB)

    Piao Yunsong [College of Physical Sciences, Graduate School of Chinese Academy of Sciences, Beijing 100049 (China)], E-mail: yspiao@gucas.ac.cn

    2009-06-15

    In the contracting phase with w{approx_equal}0, the scale invariant spectrum of curvature perturbation is given by the increasing mode of metric perturbation. In this Letter, it is found that if the contracting phase with w{approx_equal}0 is included in each cycle of a cycle universe, since the metric perturbation is amplified on super horizon scale cycle by cycle, after each cycle the universe will be inevitably separated into many parts independent of one another, each of which corresponds to a new universe and evolves up to next cycle, and then is separated again. In this sense, a cyclic multiverse scenario is actually presented, in which the universe proliferates cycle by cycle. We estimate the number of new universes proliferated in each cycle, and discuss the implications of this result.

  15. Proliferation in cycle

    International Nuclear Information System (INIS)

    Piao Yunsong

    2009-01-01

    In the contracting phase with w≅0, the scale invariant spectrum of curvature perturbation is given by the increasing mode of metric perturbation. In this Letter, it is found that if the contracting phase with w≅0 is included in each cycle of a cycle universe, since the metric perturbation is amplified on super horizon scale cycle by cycle, after each cycle the universe will be inevitably separated into many parts independent of one another, each of which corresponds to a new universe and evolves up to next cycle, and then is separated again. In this sense, a cyclic multiverse scenario is actually presented, in which the universe proliferates cycle by cycle. We estimate the number of new universes proliferated in each cycle, and discuss the implications of this result.

  16. Reflections on the motive power of fire and other papers on the second law of thermodynamics

    CERN Document Server

    Carnot, Sadi

    2005-01-01

    Reflections on the Motive Power of Fire,"" along with other papers in this volume, laid the foundation of modern thermodynamics. Highly readable, ""Reflections"" contains no arguments that depend on calculus, consisting mostly of statements couched in exact language. It represents a tribute to Carnot's capacity to generalize, and to see fundamental processes at work in complex mechanisms.""Reflections on the Motive Power of Fire"" examines the relation between heat and the work done by heat in high- and low-pressure steam engines, air-engines, and an internal combustion machine. Carnot establi

  17. Your Menstrual Cycle

    Science.gov (United States)

    ... your menstrual cycle What happens during your menstrual cycle The menstrual cycle includes not just your period, but the rise ... that take place over the weeks in your cycle. Want to know what happens on each day ...

  18. Fuel cycle cost uncertainty from nuclear fuel cycle comparison

    International Nuclear Information System (INIS)

    Li, J.; McNelis, D.; Yim, M.S.

    2013-01-01

    This paper examined the uncertainty in fuel cycle cost (FCC) calculation by considering both model and parameter uncertainty. Four different fuel cycle options were compared in the analysis including the once-through cycle (OT), the DUPIC cycle, the MOX cycle and a closed fuel cycle with fast reactors (FR). The model uncertainty was addressed by using three different FCC modeling approaches with and without the time value of money consideration. The relative ratios of FCC in comparison to OT did not change much by using different modeling approaches. This observation was consistent with the results of the sensitivity study for the discount rate. Two different sets of data with uncertainty range of unit costs were used to address the parameter uncertainty of the FCC calculation. The sensitivity study showed that the dominating contributor to the total variance of FCC is the uranium price. In general, the FCC of OT was found to be the lowest followed by FR, MOX, and DUPIC. But depending on the uranium price, the FR cycle was found to have lower FCC over OT. The reprocessing cost was also found to have a major impact on FCC

  19. Properties of a two stage adiabatic demagnetization refrigerator

    International Nuclear Information System (INIS)

    Fukuda, H; Ueda, S; Arai, R; Numazawa, T; Li, J; Saito, A T; Nakagome, H

    2015-01-01

    Currently, many space missions using cryogenic temperatures are being planned. In particular, high resolution sensors such as Transition Edge Sensors need very low temperatures, below 100 mK. It is well known that the adiabatic demagnetization refrigerator (ADR) is one of most useful tools for producing ultra-low temperatures in space because it is gravity independent. We studied a continuous ADR system consisting of 4 stages and demonstrated it could provide continuous temperatures around 100 mK. However, there was some heat leakage from the power leads which resulted in reduced cooling power. Our efforts to upgrade our ADR system are presented. We show the effect of using the HTS power leads and discuss a cascaded Carnot cycle consisting of 2 ADR units. (paper)

  20. DETECTING ALIEN LIMIT CYCLES NEAR A HAMILTONIAN 2-SADDLE CYCLE

    OpenAIRE

    LUCA, Stijn; DUMORTIER, Freddy; Caubergh, M.; Roussarie, R.

    2009-01-01

    This paper aims at providing and example of a cubic Hamiltonian 2-saddle cycle that after bifurcation can give rise to an alien limit cycle; this is a limit cycle that is not controlled by a zero of the related Abelian integral. To guarantee the existence of an alien limit cycle one can verify generic conditions on the Abelian integral and on the transition map associated to the connections of the 2-saddle cycle. In this paper, a general method is developed to compute the first and second der...

  1. Proposal of a nuclear cycle research and development plan in Tokai works. The roadmap from LWR cycle to FBR cycle

    International Nuclear Information System (INIS)

    Nakamura, Hirofumi; Abe, Tomoyuki; Kashimura, Takuo; Nagai, Toshihisa; Maeda, Seichiro; Yamaguchi, Toshiya; Kuroki, Ryoichiro

    2003-07-01

    The Generation-II Project Task Force Team has investigated a research and development plan of a future nuclear fuel cycle in Tokai works for about three months from December 19, 2002. First we have discussed about the present condition of Japanese nuclear fuel cycle and have recognized it as the following. The relation of the technology between the LWR-cycle and the FBR-cycle is not clear. MOX Fuel Use in Light Water Reactors is important to establish technology of the FBR fuel cycle. Radioactive waste disposal issue is urgent. Next we have proposed the three basic policies on R and D plan of nuclear fuel cycle in consideration of the F.S. on FBR-cycle. Establishment and advancement of 'the tough nuclear fuel cycle'. Early establishment of the FBR cycle technology to be able to supply energy stably for long-term. Establishment of the radioactive waste treatment and disposal technology, and optimization of nuclear fuel cycle technology from the viewpoint of radioactive waste. And we have proposed the Japanese technical holder system to integrate all LWR and FBR cycle technology. (author)

  2. Simulation of Cycle-to-Cycle Variation in Dual-Fuel Engines

    KAUST Repository

    Jaasim, Mohammed

    2017-03-13

    Standard practices of internal combustion (IC) engine experiments are to conduct the measurements of quantities averaged over a large number of cycles. Depending on the operating conditions, the cycle-to-cycle variation (CCV) of quantities, such as the indicated mean effective pressure (IMEP) are observed at different levels. Accurate prediction of CCV in IC engines is an important but challenging task. Computational fluid dynamics (CFD) simulations using high performance computing (HPC) can be used effectively to visualize such 3D spatial distributions. In the present study, a dual fuel large engine is considered, with natural gas injected into the manifold accompanied with direct injection of diesel pilot fuel to trigger ignition. Multiple engine cycles in 3D are simulated in series as in the experiments to investigate the potential of HPC based high fidelity simulations to accurately capture the cycle to cycle variation in dual fuel engines. Open cycle simulations are conducted to predict the combined effect of the stratification of fuel-air mixture, temperature and turbulence on the CCV of pressure. The predicted coefficient of variation (COV) of pressure compared to the results from closed cycle simulations and the experiments.

  3. Identifying and addressing specific student difficulties in advanced thermal physics

    Science.gov (United States)

    Smith, Trevor I.

    As part of an ongoing multi-university research study on student understanding of concepts in thermal physics at the upper division, I identified several student difficulties with topics related to heat engines (especially the Carnot cycle), as well as difficulties related to the Boltzmann factor. In an effort to address these difficulties, I developed two guided-inquiry worksheet activities (a.k.a. tutorials) for use in advanced undergraduate thermal physics courses. Both tutorials seek to improve student understanding of the utility and physical background of a particular mathematical expression. One tutorial focuses on a derivation of Carnot's theorem regarding the limit on thermodynamic efficiency, starting from the Second Law of Thermodynamics. The other tutorial helps students gain an appreciation for the origin of the Boltzmann factor and when it is applicable; focusing on the physical justification of its mathematical derivation, with emphasis on the connections between probability, multiplicity, entropy, and energy. Student understanding of the use and physical implications of Carnot's theorem and the Boltzmann factor was assessed using written surveys both before and after tutorial instruction within the advanced thermal physics courses at the University of Maine and at other institutions. Classroom tutorial sessions at the University of Maine were videotaped to allow in-depth scrutiny of student successes and failures following tutorial prompts. I also interviewed students on various topics related to the Boltzmann factor to gain a more complete picture of their understanding and inform tutorial revisions. Results from several implementations of my tutorials at the University of Maine indicate that students did not have a robust understanding of these physical principles after lectures alone, and that they gain a better understanding of relevant topics after tutorial instruction; Fisher's exact tests yield statistically significant improvement at the

  4. Simulation of Cycle-to-Cycle Variation in Dual-Fuel Engines

    KAUST Repository

    Jaasim, Mohammed; Pasunurthi, Shyamsundar; Jupudi, Ravichandra S.; Gubba, Sreenivasa Rao; Primus, Roy; Klingbeil, Adam; Wijeyakulasuriya, Sameera; Im, Hong G.

    2017-01-01

    Standard practices of internal combustion (IC) engine experiments are to conduct the measurements of quantities averaged over a large number of cycles. Depending on the operating conditions, the cycle-to-cycle variation (CCV) of quantities

  5. Life-cycle cost analysis of adsorption cycles for desalination

    KAUST Repository

    Thu, Kyaw

    2010-08-01

    This paper presents the thermo-economic analysis of the adsorption desalination (AD) cycle that is driven by low-temperature waste heat from exhaust of industrial processes or renewable sources. The AD cycle uses an adsorbent such as the silica gel to desalt the sea or brackish water. Based on an experimental prototype AD plant, the life-cycle cost analysis of AD plants of assorted water production capacities has been simulated and these predictions are translated into unit cost of water production. Our results show that the specific energy consumption of the AD cycle is 1.38 kWh/m3 which is the lowest ever reported. For a plant capacity of 1000 m3/d, the AD cycle offers a unit cost of $0.457/m3 as compared to more than $0.9 for the average RO plants. Besides being cost-effective, the AD cycle is also environment-friendly as it emits less CO2 emission per m3 generated, typically 85% less, by comparison to an RO process. © 2010 Desalination Publications.

  6. How well can business cycle accounting account for business cycles?

    OpenAIRE

    Keisuke Otsu

    2012-01-01

    The business cycle accounting method introduced by Chari, Kehoe and McGrattan (2007) is a useful tool to decompose business cycle fluctuations into their contributing factors. However, the model estimated by the maximum likelihood method cannot replicate business cycle moments computed from data. Moment-based estimation might be an attractive alternative if the purpose of the research is to study business cycle properties such as volatility, persistence and cross-correlation of variables inst...

  7. A feasibility analysis of replacing the standard ammonia refrigeration device with the cascade NH3/CO2 refrigeration device in the food industry

    Directory of Open Access Journals (Sweden)

    Jankovich Dennis

    2015-01-01

    Full Text Available The thermodynamic analysis demonstrates the feasibility of replacing the standard ammonia refrigeration device with the cascade NH3/CO2 refrigeration device in the food industry. The main reason for replacement is to reduce the total amount of ammonia in spaces like deep-freezing chambers, daily chambers, working rooms and technical passageways. An ammonia-contaminated area is hazardous to human health and the safety of food products. Therefore the preferred reduced amount of ammonia is accumulated in the Central Refrigeration Engine Room, where the cascade NH3/CO2 device is installed as well. Furthermore, the analysis discusses and compares two left Carnot¢s refrigeration cycles, one for the standard ammonia device and the other for the cascade NH3/CO2 device. Both cycles are processes with two-stage compression and two-stage throttling. The thermodynamic analysis demonstrates that the selected refrigeration cycle is the most cost-effective process because it provides the best numerical values for the total refrigeration factor with respect to the observed refrigeration cycle. The chief analyzed influential parameters of the cascade device are: total refrigeration load, total reactive power, mean temperature of the heat exchanger, evaporating and condensing temperature of the low-temperature part.

  8. Cycling in Sydney, Australia

    Directory of Open Access Journals (Sweden)

    Alexis Zander

    2013-01-01

    Full Text Available Introduction. Cycling can be an enjoyable way to meet physical activity recommendations and is suitable for older people; however cycling participation by older Australians is low. This qualitative study explored motivators, enablers, and barriers to cycling among older people through an age-targeted cycling promotion program. Methods. Seventeen adults who aged 50–75 years participated in a 12-week cycling promotion program which included a cycling skills course, mentor, and resource pack. Semistructured interviews at the beginning and end of the program explored motivators, enablers, and barriers to cycling. Results. Fitness and recreation were the primary motivators for cycling. The biggest barrier was fear of cars and traffic, and the cycling skills course was the most important enabler for improving participants’ confidence. Reported outcomes from cycling included improved quality of life (better mental health, social benefit, and empowerment and improved physical health. Conclusions. A simple cycling program increased cycling participation among older people. This work confirms the importance of improving confidence in this age group through a skills course, mentors, and maps and highlights additional strategies for promoting cycling, such as ongoing improvement to infrastructure and advertising.

  9. Single-particle stochastic heat engine

    Science.gov (United States)

    Rana, Shubhashis; Pal, P. S.; Saha, Arnab; Jayannavar, A. M.

    2014-10-01

    We have performed an extensive analysis of a single-particle stochastic heat engine constructed by manipulating a Brownian particle in a time-dependent harmonic potential. The cycle consists of two isothermal steps at different temperatures and two adiabatic steps similar to that of a Carnot engine. The engine shows qualitative differences in inertial and overdamped regimes. All the thermodynamic quantities, including efficiency, exhibit strong fluctuations in a time periodic steady state. The fluctuations of stochastic efficiency dominate over the mean values even in the quasistatic regime. Interestingly, our system acts as an engine provided the temperature difference between the two reservoirs is greater than a finite critical value which in turn depends on the cycle time and other system parameters. This is supported by our analytical results carried out in the quasistatic regime. Our system works more reliably as an engine for large cycle times. By studying various model systems, we observe that the operational characteristics are model dependent. Our results clearly rule out any universal relation between efficiency at maximum power and temperature of the baths. We have also verified fluctuation relations for heat engines in time periodic steady state.

  10. Marine nitrogen cycle

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.

    ) such as the Marine nitrogen cycle The marine nitrogen cycle. ‘X’ and ‘Y’ are intra-cellular intermediates that do not accumulate in water column. (Source: Codispoti et al., 2001) Page 1 of 3Marine nitrogen cycle - Encyclopedia of Earth 11/20/2006http://www... and nitrous oxide budgets: Moving targets as we enter the anthropocene?, Sci. Mar., 65, 85-105, 2001. Page 2 of 3Marine nitrogen cycle - Encyclopedia of Earth 11/20/2006http://www.eoearth.org/article/Marine_nitrogen_cycle square6 Gruber, N.: The dynamics...

  11. Reproductive cycles in tropical intertidal gastropods are timed around tidal amplitude cycles.

    Science.gov (United States)

    Collin, Rachel; Kerr, Kecia; Contolini, Gina; Ochoa, Isis

    2017-08-01

    Reproduction in iteroparous marine organisms is often timed with abiotic cycles and may follow lunar, tidal amplitude, or daily cycles. Among intertidal marine invertebrates, decapods are well known to time larval release to coincide with large amplitude nighttime tides, which minimizes the risk of predation. Such bimonthly cycles have been reported for few other intertidal invertebrates. We documented the reproduction of 6 gastropod species from Panama to determine whether they demonstrate reproductive cycles, whether these cycles follow a 2-week cycle, and whether cycles are timed so that larval release occurs during large amplitude tides. Two of the species ( Crepidula cf. marginalis and Nerita scabricosta ) showed nonuniform reproduction, but without clear peaks in timing relative to tidal or lunar cycles. The other 4 species show clear peaks in reproduction occurring every 2 weeks. In 3 of these species ( Cerithideopsis carlifornica var. valida, Littoraria variegata , and Natica chemnitzi ), hatching occurred within 4 days of the maximum amplitude tides. Siphonaria palmata exhibit strong cycles, but reproduction occurred during the neap tides. Strong differences in the intensity of reproduction of Cerithideopsis carlifornica , and in particular, Littoraria variegata , between the larger and smaller spring tides of a lunar month indicate that these species time reproduction with the tidal amplitude cycle rather than the lunar cycle. For those species that reproduce during both the wet and dry seasons, we found that reproductive timing did not differ between seasons despite strong differences in temperature and precipitation. Overall, we found that most (4/6) species have strong reproductive cycles synchronized with the tidal amplitude cycle and that seasonal differences in abiotic factors do not alter these cycles.

  12. Creeping of hysteresis cycles; Reptation des cycles d'hysteresis

    Energy Technology Data Exchange (ETDEWEB)

    Neel, L [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Faculte des Sciences de Grenoble, 38 (France)

    1959-07-01

    Creeping consists of a kind of progressive translation of dissymmetric ferromagnetic hysteresis cycles as a function of the order number of the cycle. It is interpreted here by means of a probable coupling field, the existence of which is connected to a statistical conception of the distribution of the elementary regions. (author) [French] La reptation consiste en une sorte de translation progressive des cycles d'hysteresis ferromagnetiques dissymetriques en fonction du numero d'ordre du cycle. L'auteur l'interprete au moyen d'un champ aleatoire de couplage dont l'existence est liee a une conception statistique de la distribution des domaines elementaires. (auteur)

  13. Glacial cycles

    DEFF Research Database (Denmark)

    Kaufmann, R. K.; Juselius, Katarina

    We use a statistical model, the cointegrated vector autoregressive model, to assess the degree to which variations in Earth's orbit and endogenous climate dynamics can be used to simulate glacial cycles during the late Quaternary (390 kyr-present). To do so, we estimate models of varying complexity...... and compare the accuracy of their in-sample simulations. Results indicate that strong statistical associations between endogenous climate variables are not enough for statistical models to reproduce glacial cycles. Rather, changes in solar insolation associated with changes in Earth's orbit are needed...... to simulate glacial cycles accurately. Also, results suggest that non-linear 10 dynamics, threshold effects, and/or free oscillations may not play an overriding role in glacial cycles....

  14. The glutathione cycle: Glutathione metabolism beyond the γ-glutamyl cycle.

    Science.gov (United States)

    Bachhawat, Anand Kumar; Yadav, Shambhu

    2018-04-17

    Glutathione was discovered in 1888, over 125 years ago. Since then, our understanding of various functions and metabolism of this important molecule has grown over these years. But it is only now, in the last decade, that a somewhat complete picture of its metabolism has emerged. Glutathione metabolism has till now been largely depicted and understood by the γ-glutamyl cycle that was proposed in 1970. However, new findings and knowledge particularly on the transport and degradation of glutathione have revealed that many aspects of the γ-glutamyl cycle are incorrect. Despite this, an integrated critical analysis of the cycle has never been undertaken and this has led to the cycle and its errors perpetuating in the literature. This review takes a careful look at the γ-glutamyl cycle and its shortcomings and presents a "glutathione cycle" that captures the current understanding of glutathione metabolism. © 2018 IUBMB Life, 2018. © 2018 International Union of Biochemistry and Molecular Biology.

  15. Single generation cycles and delayed feedback cycles are not separate phenomena.

    Science.gov (United States)

    Pfaff, T; Brechtel, A; Drossel, B; Guill, C

    2014-12-01

    We study a simple model for generation cycles, which are oscillations with a period of one or a few generation times of the species. The model is formulated in terms of a single delay-differential equation for the population density of an adult stage, with recruitment to the adult stage depending on the intensity of competition during the juvenile phase. This model is a simplified version of a group of models proposed by Gurney and Nisbet, who were the first to distinguish between single-generation cycles and delayed-feedback cycles. According to these authors, the two oscillation types are caused by different mechanisms and have periods in different intervals, which are one to two generation times for single-generation cycles and two to four generation times for delayed-feedback cycles. By abolishing the strict coupling between the maturation time and the time delay between competition and its effect on the population dynamics, we find that single-generation cycles and delayed-feedback cycles occur in the same model version, with a gradual transition between the two as the model parameters are varied over a sufficiently large range. Furthermore, cycle periods are not bounded to lie within single octaves. This implies that a clear distinction between different types of generation cycles is not possible. Cycles of all periods and even chaos can be generated by varying the parameters that determine the time during which individuals from different cohorts compete with each other. This suggests that life-cycle features in the juvenile stage and during the transition to the adult stage are important determinants of the dynamics of density limited populations. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. [Cycling in Zagreb].

    Science.gov (United States)

    Matos, Stipan; Krapac, Ladislav; Krapac, Josip

    2007-01-01

    Cycling in Zagreb, as means of urban transport inside and outside the city, has a bright past, hazy presence but a promising future. Every day, aggressive citizens who lack urban traffic culture mistreat many cyclists but also many pedestrians. Sedentary way of living, unhealthy eating habits and inadequate recreation would surely be reduced if Zagreb had a network of cycling tracks (190 cm) or lanes (80 cm). Main city roads were constructed at the beginning of the 20th century. Today, the lack of cycling tracks is particularly evident in terms of missing connections between northern and southern parts of the city. Transportation of bikes in public vehicles, parking of bikes as well as cycling along the foot of the mountains Medvednica and Zumberacko gorje is not adequately organized. Better organization is necessary not only because of the present young generation but also because of the young who will shortly become citizens of the EU, where cycling is enormously popular. Cycling tourism is not known in Zagreb, partly due to inadequate roads. The surroundings of Zagreb are more suitable for cycling tourism and attractive brochures and tourist guides offer information to tourists on bikes. Professional, acrobatic and sports cycling do not have a tradition in Zagreb and in Croatia. The same holds true for recreational cycling and indoor exercise cycling. The authors discuss the impact of popularization of cycling using print and electronic media. The role of district and local self-government in the construction and improvement of traffic roads in Zagreb is very important. It is also significant for the implementation of legal regulations that must be obeyed by all traffic participants in order to protect cyclists, the most vulnerable group of traffic participants besides passengers. Multidisciplinary action of all benevolent experts would surely increase safety and pleasure of cycling in the city and its surroundings. This would also help reduce daily stress and

  17. Cycle to Cycle Variation Study in a Dual Fuel Operated Engine

    KAUST Repository

    Pasunurthi, Shyamsundar

    2017-03-28

    The standard capability of engine experimental studies is that ensemble averaged quantities like in-cylinder pressure from multiple cycles and emissions are reported and the cycle to cycle variation (CCV) of indicated mean effective pressure (IMEP) is captured from many consecutive combustion cycles for each test condition. However, obtaining 3D spatial distribution of all the relevant quantities such as fuel-air mixing, temperature, turbulence levels and emissions from such experiments is a challenging task. Computational Fluid Dynamics (CFD) simulations of engine flow and combustion can be used effectively to visualize such 3D spatial distributions. A dual fuel engine is considered in the current study, with manifold injected natural gas (NG) and direct injected diesel pilot for ignition. Multiple engine cycles in 3D are simulated in series like in the experiments to investigate the potential of high fidelity RANS simulations coupled with detailed chemistry, to accurately predict the CCV. Cycle to cycle variation (CCV) is expected to be due to variabilities in operating and boundary conditions, in-cylinder stratification of diesel and natural gas fuels, variation in in-cylinder turbulence levels and velocity flow-fields. In a previous publication by the authors [1], variabilities in operating and boundary conditions are incorporated into several closed cycle simulations performed in parallel. Stochastic variations/stratifications of fuel-air mixture, turbulence levels, temperature and internal combustion residuals cannot be considered in such closed cycle simulations. In this study, open cycle simulations with port injection of natural gas predicted the combined effect of the stratifications on the CCV of in-cylinder pressure. The predicted Coefficient of Variation (COV) of cylinder pressure is improved compared to the one captured by closed cycle simulations in parallel.

  18. Internal cycle modeling and environmental assessment of multiple cycle consumer products

    International Nuclear Information System (INIS)

    Tsiliyannis, C.A.

    2012-01-01

    Highlights: ► Dynamic flow models are presented for remanufactured, reused or recycled products. ► Early loss and stochastic return are included for fast and slow cycling products. ► The reuse-to-input flow ratio (Internal Cycle Factor, ICF) is determined. ► The cycle rate, which is increasing with the ICF, monitors eco-performance. ► Early internal cycle losses diminish the ICF, the cycle rate and performance. - Abstract: Dynamic annual flow models incorporating consumer discard and usage loss and featuring deterministic and stochastic end-of-cycle (EOC) return by the consumer are developed for reused or remanufactured products (multiple cycle products, MCPs), including fast and slow cycling, short and long-lived products. It is shown that internal flows (reuse and overall consumption) increase proportionally to the dimensionless internal cycle factor (ICF) which is related to environmental impact reduction factors. The combined reuse/recycle (or cycle) rate is shown capable for shortcut, albeit effective, monitoring of environmental performance in terms of waste production, virgin material extraction and manufacturing impacts of all MCPs, a task, which physical variables (lifetime, cycling frequency, mean or total number of return trips) and conventional rates, via which environmental policy has been officially implemented (e.g. recycling rate) cannot accomplish. The cycle rate is shown to be an increasing (hyperbolic) function of ICF. The impact of the stochastic EOC return characteristics on total reuse and consumption flows, as well as on eco-performance, is assessed: symmetric EOC return has a small, positive effect on performance compared to deterministic, while early shifted EOC return is more beneficial. In order to be efficient, environmental policy should set higher minimum reuse targets for higher trippage MCPs. The results may serve for monitoring, flow accounting and comparative eco-assessment of MCPs. They may be useful in identifying

  19. Análisis de irreversibilidades en el comportamiento de un motor Stirling // Analysis of irreversibilities on performance of a Stirling engine

    Directory of Open Access Journals (Sweden)

    Juan José González-Bayón

    2011-05-01

    Full Text Available El objetivo de este estudio es determinar el efecto de las irreversibilidades (internas y externasdebidas a la transferencia de calor y las pérdidas de presión debidas a la fricción sobre elrendimiento de Segunda Ley de un motor Stirling de tipo considerando el volumen muerto. Elmotor Stirling es analizado usando un modelo matemático basado en las leyes de la termodinámicapara procesos con una velocidad finita. Se asume un modelo isotérmico de motor con volúmenes deespacio muerto en la zona caliente, zona fría y en el regenerador. Los resultados obtenidos muestranque a pesar de que teóricamente el motor Stirling posee un rendimiento igual al de Carnot, en lapráctica su rendimiento puede ser de 2 a 5 veces menor que éste, dependiendo de la eficiencia delregenerador, del volumen muerto, de la diferencia de temperatura entre fluido y focos térmicos y delas rpm a que se opere el motor.Palabras claves: motor Stirling, motor térmico regenerativo, análisis de irreversibilidades.____________________________________________________________________AbstractThe study aims to determine the effect of the internal and external irreversibilities caused by heattransfer and pressure losses due to friction on the Second Law performance of a Stirling engine tipewith death volume include. The Stirling engine is analyzed using a mathematical model based onthe laws of thermodynamics for processes with finite speed. It is assumed an isothermic model of themotor with death volume on hot zone, cold zone and regenerator. The results of this study show thatthe real cycle efficiency of the Sirling engine is approximately 2 to 5 times minor than the efficiency ofCarnot cycle as function of the regenerator efficiency, death volume, temperature difference betweenfluid and termic source and motor speed.Key words: stirling engine, regenerative heat engine, irreversibilities analysis.

  20. Cycle to Cycle Variation Study in a Dual Fuel Operated Engine

    KAUST Repository

    Pasunurthi, Shyamsundar; Jupudi, Ravichandra; Wijeyakulasuriya, Sameera; Gubba, Sreenivasa Rao; Im, Hong G.; Jaasim, Mohammed; Primus, Roy; Klingbeil, Adam; Finney, Charles

    2017-01-01

    The standard capability of engine experimental studies is that ensemble averaged quantities like in-cylinder pressure from multiple cycles and emissions are reported and the cycle to cycle variation (CCV) of indicated mean effective pressure (IMEP

  1. The Hamburg oceanic carbon cycle circulation model. Cycle 1

    International Nuclear Information System (INIS)

    Maier-Reimer, E.; Heinze, C.

    1992-02-01

    The carbon cycle model calculates the prognostic fields of oceanic geochemical carbon cycle tracers making use of a 'frozen' velocity field provided by a run of the LSG oceanic circulation model (see the corresponding manual, LSG=Large Scale Geostrophic). The carbon cycle model includes a crude approximation of interactions between sediment and bottom layer water. A simple (meridionally diffusive) one layer atmosphere model allows to calculate the CO 2 airborne fraction resulting from the oceanic biogeochemical interactions. (orig.)

  2. Future fuel cycles

    International Nuclear Information System (INIS)

    Archinoff, G.H.

    1980-01-01

    A fuel cycle must offer both financial and resource savings if it is to be considered for introduction into Ontario's nuclear system. The most promising alternative CANDU fuel cycles are examined in the context of both of these factors over a wide range of installed capacity growth rates and economic assumptions, in order to determine which fuel cycle, or cycles, should be introduced, and when. It is concluded that the optimum path for the long term begins with the prompt introduction of the low-enriched-uranium fuel cycle. For a wide range of conditions, this cycle remains the optimum throughout the very long term. Conditions of rapid nuclear growth and very high uranium price escalation rates warrant the supersedure of the low-enriched-uranium cycle by either a plutonium-topped thorium cycle or plutonium recycle, beginning between 2010 and 2025. It is also found that the uranium resource position is sound in terms of both known resources and production capability. Moreover, introduction of the low-enriched-uranium fuel cycle and 1250 MWe reactor units will assure the economic viability of nuclear power until at least 2020, even if uranium prices increase at a rate of 3.5% above inflation. The interrelationship between these two conclusions lies in the tremendous incentive for exploration which will occur if the real uranium price escalation rate is high. From a competitive viewpoint, nuclear power can withstand increases in the price of uranium. However, such increases will likely further expand the resource base, making nuclear an even more reliable energy source. (auth)

  3. Life Cycle Management

    DEFF Research Database (Denmark)

    Bey, Niki

    2018-01-01

    This chapter gives an overview of Life Cycle Management (LCM)—a discipline that deals with the managerial tasks related to practicing sustainable development in an organisation . Just as Life Cycle Assessment, LCM advocates the life cycle perspective , and it applies this perspective in decision...

  4. Statistical properties and time-frequency analysis of temperature, salinity and turbidity measured by the MAREL Carnot station in the coastal waters of Boulogne-sur-Mer (France)

    Science.gov (United States)

    Kbaier Ben Ismail, Dhouha; Lazure, Pascal; Puillat, Ingrid

    2016-10-01

    In marine sciences, many fields display high variability over a large range of spatial and temporal scales, from seconds to thousands of years. The longer recorded time series, with an increasing sampling frequency, in this field are often nonlinear, nonstationary, multiscale and noisy. Their analysis faces new challenges and thus requires the implementation of adequate and specific methods. The objective of this paper is to highlight time series analysis methods already applied in econometrics, signal processing, health, etc. to the environmental marine domain, assess advantages and inconvenients and compare classical techniques with more recent ones. Temperature, turbidity and salinity are important quantities for ecosystem studies. The authors here consider the fluctuations of sea level, salinity, turbidity and temperature recorded from the MAREL Carnot system of Boulogne-sur-Mer (France), which is a moored buoy equipped with physico-chemical measuring devices, working in continuous and autonomous conditions. In order to perform adequate statistical and spectral analyses, it is necessary to know the nature of the considered time series. For this purpose, the stationarity of the series and the occurrence of unit-root are addressed with the Augmented-Dickey Fuller tests. As an example, the harmonic analysis is not relevant for temperature, turbidity and salinity due to the nonstationary condition, except for the nearly stationary sea level datasets. In order to consider the dominant frequencies associated to the dynamics, the large number of data provided by the sensors should enable the estimation of Fourier spectral analysis. Different power spectra show a complex variability and reveal an influence of environmental factors such as tides. However, the previous classical spectral analysis, namely the Blackman-Tukey method, requires not only linear and stationary data but also evenly-spaced data. Interpolating the time series introduces numerous artifacts to the

  5. BWROPT: A multi-cycle BWR fuel cycle optimization code

    Energy Technology Data Exchange (ETDEWEB)

    Ottinger, Keith E.; Maldonado, G. Ivan, E-mail: Ivan.Maldonado@utk.edu

    2015-09-15

    Highlights: • A multi-cycle BWR fuel cycle optimization algorithm is presented. • New fuel inventory and core loading pattern determination. • The parallel simulated annealing algorithm was used for the optimization. • Variable sampling probabilities were compared to constant sampling probabilities. - Abstract: A new computer code for performing BWR in-core and out-of-core fuel cycle optimization for multiple cycles simultaneously has been developed. Parallel simulated annealing (PSA) is used to optimize the new fuel inventory and placement of new and reload fuel for each cycle considered. Several algorithm improvements were implemented and evaluated. The most significant of these are variable sampling probabilities and sampling new fuel types from an ordered array. A heuristic control rod pattern (CRP) search algorithm was also implemented, which is useful for single CRP determinations, however, this feature requires significant computational resources and is currently not practical for use in a full multi-cycle optimization. The PSA algorithm was demonstrated to be capable of significant objective function reduction and finding candidate loading patterns without constraint violations. The use of variable sampling probabilities was shown to reduce runtime while producing better results compared to using constant sampling probabilities. Sampling new fuel types from an ordered array was shown to have a mixed effect compared to random new fuel type sampling, whereby using both random and ordered sampling produced better results but required longer runtimes.

  6. Generalized irreversible heat-engine experiencing a complex heat-transfer law

    International Nuclear Information System (INIS)

    Chen Lingen; Li Jun; Sun Fengrui

    2008-01-01

    The fundamental optimal relation between optimal power-output and efficiency of a generalized irreversible Carnot heat-engine is derived based on a generalized heat-transfer law, including a generalized convective heat-transfer law and a generalized radiative heat-transfer law, q ∝ (ΔT n ) m . The generalized irreversible Carnot-engine model incorporates several internal and external irreversibilities, such as heat resistance, bypass heat-leak, friction, turbulence and other undesirable irreversibility factors. The added irreversibilities, besides heat resistance, are characterized by a constant parameter and a constant coefficient. The effects of heat-transfer laws and various loss terms are analyzed. The results obtained corroborate those in the literature

  7. Prediction of Chiller Power Consumption: An Entropy Generation Approach

    KAUST Repository

    Saththasivam, Jayaprakash

    2016-06-21

    Irreversibilities in each component of vapor compression chillers contribute to additional power consumption in chillers. In this study, chiller power consumption was predicted by computing the Carnot reversible work and entropy generated in every component of the chiller. Thermodynamic properties namely enthalpy and entropy of the entire refrigerant cycle were obtained by measuring the pressure and temperature at the inlet and outlet of each primary component of a 15kW R22 water cooled scroll chiller. Entropy generation of each component was then calculated using the First and Second Laws of Thermodynamics. Good correlation was found between the measured and computed chiller power consumption. This irreversibility analysis can be also effectively used as a performance monitoring tool in vapor compression chillers as higher entropy generation is anticipated during faulty operations.

  8. Efficient protocols for Stirling heat engines at the micro-scale

    Science.gov (United States)

    Muratore-Ginanneschi, Paolo; Schwieger, Kay

    2015-10-01

    We investigate the thermodynamic efficiency of sub-micro-scale Stirling heat engines operating under the conditions described by overdamped stochastic thermodynamics. We show how to construct optimal protocols such that at maximum power the efficiency attains for constant isotropic mobility the universal law η=2 ηC/(4-ηC) , where ηC is the efficiency of an ideal Carnot cycle. We show that these protocols are specified by the solution of an optimal mass transport problem. Such solution can be determined explicitly using well-known Monge-Ampère-Kantorovich reconstruction algorithms. Furthermore, we show that the same law describes the efficiency of heat engines operating at maximum work over short time periods. Finally, we illustrate the straightforward extension of these results to cases when the mobility is anisotropic and temperature dependent.

  9. Grey-box Modelling of a Household Refrigeration Unit Using Time Series Data in Application to Demand Side Management

    DEFF Research Database (Denmark)

    Sossan, Fabrizio; Lakshmanan, Venkatachalam; Costanzo, Giuseppe Tommaso

    2016-01-01

    This paper describes the application of stochastic grey-box modeling to identify electrical power consumption-to-temperature models of a domestic freezer using experimental measurements. The models are formulated using stochastic differential equations (SDEs), estimated by maximum likelihood......) to shift the electricity consumption of a freezer in demand response experiments, thereby addressing the model selection problem also from the application point of view and showing in an experimental context the ability of MPC to exploit the freezer as a demand side resource (DSR)....... estimation (MLE), validated through the model residuals analysis and cross-validated to detect model over-fitting. A nonlinear model based on the reversed Carnot cycle is also presented and included in the modeling performance analysis. As an application of the models, we apply model predictive control (MPC...

  10. The mechanical design of a vapor compressor for a heat pump to be used in space

    Science.gov (United States)

    Berner, F.; Oesch, H.; Goetz, K.; Savage, C. J.

    1982-01-01

    A heat pump developed for use in Spacelab as a stand-alone refrigeration unit as well as within a fluid loop system is discussed. It will provide an active thermal control for payloads. Specifications for the heat pump were established: (1) heat removal rates at the source; (2) heat source temperatures from room temperature; (3) heat-sink fluid temperatures at condenser inlet; and (4) minimum power consumption. A reversed Carnot cycle heat pump using Freon 12 as working fluid incorporating a one-cylinder reciprocating compressor was selected. The maximum crankshaft speed was fixed relatively high at 100 rpm. The specified cooling rates then made it necessary to select a cylinder volume of 10 cu cm, which was obtained with a bore of 40 mm and a stroke of 8 mm.

  11. Coefficient of performance of Stirling refrigerators

    Science.gov (United States)

    E Mungan, Carl

    2017-09-01

    Stirling coolers transfer heat in or out of the working fluid during all four stages of their operation, and their coefficient of performance depends on whether the non-isothermal heat exchanges are performed reversibly or irreversibly. Both of these possibilities can in principle be arranged. Notably, if the working fluid is an ideal gas, the input of energy in the form of heat during one isochoric step is equal in magnitude to the output during the other isochoric step in the cycle. The theoretical performance of the fridge can then attain the reversible Carnot limit if a regenerator is used, which is a high heat capacity material through which the gas flows. Various Stirling refrigerator configurations are analysed in this article at a level of presentation suitable for an introductory undergraduate thermodynamics course.

  12. Sulfur cycle

    Digital Repository Service at National Institute of Oceanography (India)

    LokaBharathi, P.A.

    Microbes, especially bacteria, play an important role in oxidative and reductive cycle of sulfur. The oxidative part of the cycle is mediated by photosynthetic bacteria in the presence of light energy and chemosynthetic forms in the absence of light...

  13. Fast Reactor Fuel Cycle Cost Estimates for Advanced Fuel Cycle Studies

    International Nuclear Information System (INIS)

    Harrison, Thomas

    2013-01-01

    Presentation Outline: • Why Do I Need a Cost Basis?; • History of the Advanced Fuel Cycle Cost Basis; • Description of the Cost Basis; • Current Work; • Fast Reactor Fuel Cycle Applications; • Sample Fuel Cycle Cost Estimate Analysis; • Future Work

  14. Essays on economic cycles

    NARCIS (Netherlands)

    Groot, de E.A. (Bert)

    2006-01-01

    Schumpeter’s line of thought of multiple economic cycles is further investigated. The existence of multiple cycles in economic variables is demonstrated. In basic innovations five different cycles are found. Multiple cycle structures are shown in various macro-economic variables from the United

  15. Nuclear-fuel-cycle education: Module 1. Nuclear fuel cycle overview

    International Nuclear Information System (INIS)

    Eckhoff, N.D.

    1981-07-01

    This educational module is an overview of the nuclear-fule-cycle. The overview covers nuclear energy resources, the present and future US nuclear industry, the industry view of nuclear power, the International Nuclear Fuel Cycle Evaluation program, the Union of Concerned Scientists view of the nuclear-fuel-cycle, an analysis of this viewpoint, resource requirements for a model light water reactor, and world nuclear power considerations

  16. Thorium cycles and proliferation

    International Nuclear Information System (INIS)

    Lovins, A.B.

    1979-01-01

    This paper analyzes several prevalent misconceptions about nuclear fuel cycles that breed fissile uranium-233 from thorium. Its main conclusions are: U-233, despite the gamma radioactivity of associated isotopes, is a rather attractive material for making fission bombs, and is a credible material for subnational as well as national groups to use for this purpose; (2) pure thorium cycles, which in effect merely substitute U-233 for Pu, would take many decades and much U to establish, and offer no significant safeguards advantage over Pu, cycles; (3) denatured Th-U cycles, which dilute the U-233 with inert U-238 to a level not directly usable in bombs, are not an effective safeguard even against subnational bomb-making; (4) several other features of mixed Th-U cycles are rather unattractive from a safeguards point of view; (5) thus, Th cycles of any kind are not a technical fix for proliferation (national or subnational) and, though probably more safeguardable than Pu cycles, are less so than once-through U cycles that entail no reprocessing; (6) while thorium cycles have some potential technical advantages, including flexibility, they cannot provide major savings in nuclear fuel resources compared to simpler ways of saving neutrons and U; and (7) while advocates of nuclear power may find Th cycles worth exploring, such cycles do not differ fundamentally from U cycles in any of the respects--including safeguards and fuel resources--that are relevant to the broader nuclear debate, and should not be euphorically embraced as if they did

  17. SMA foil-based elastocaloric cooling: from material behavior to device engineering

    Science.gov (United States)

    Bruederlin, F.; Ossmer, H.; Wendler, F.; Miyazaki, S.; Kohl, M.

    2017-10-01

    The elastocaloric effect associated with the stress-induced first order phase transformation in pseudoelastic shape memory alloy (SMA) films and foils is of special interest for cooling applications on a miniature scale enabling fast heat transfer and high cycling frequencies as well as tunable transformation temperatures. The focus is on TiNi-based materials having the potential to meet the various challenges associated with elastocaloric cooling including large adiabatic temperature change and ultra-low fatigue. The evolution of strain and temperature bands during tensile load cycling is investigated with respect to strain and strain-rate by in situ digital image correlation and infrared thermography with a spatial resolution in the order of 25 µm. Major design issues and challenges in fabrication of SMA film-based elastocaloric cooling devices are discussed including the efficiency of heat transfer as well as force recovery to enhance the coefficient of performance (COP) on the system level. Advanced demonstrators show a temperature span of 13 °C after 30 s, while the COP of the overall device reaches almost 10% of Carnot efficiency.

  18. Drivers of cycling demand and cycling futures in the Danish context

    DEFF Research Database (Denmark)

    Analysis of the time trend in cycling mode share based on longest possible time series. Logistic regression model of cycling as mode choice as basis for studying ‘driver variables’ contribution to time trend. Describing important vectors of change behind the time trend.......Analysis of the time trend in cycling mode share based on longest possible time series. Logistic regression model of cycling as mode choice as basis for studying ‘driver variables’ contribution to time trend. Describing important vectors of change behind the time trend....

  19. Assessing Cycling Participation in Australia

    Directory of Open Access Journals (Sweden)

    Chris Rissel

    2013-01-01

    Full Text Available Planning and evaluating cycling programs at a national or state level requires accurate measures of cycling participation. However, recent reports of cycling participation have produced very different estimates. This paper examines the reported rates of cycling in five recent population surveys of cycling. Three surveys (one national and two from Sydney asking respondents when they last rode a bicycle generated cycling participation (cycled in the past year estimates of 29.7%, 34.1% and 28.9%. Two other national surveys which asked participants to recall (unprompted any physical activity done for exercise, recreation or sport in the previous 12 months, estimated cycling in the past year as 11.1% and 6.5%. While unprompted recall of cycling as a type of physical activity generates lower estimates of cycling participation than specific recall questions, both assessment approaches produced similar patterns of cycling by age and sex with both approaches indicating fewer women and older adults cycling. The different question styles most likely explain the substantial discrepancies between the estimates of cycling participation. Some differences are to be expected due to sampling variability, question differences, and regional variation in cycling.

  20. Life-cycle cost analysis of adsorption cycles for desalination

    KAUST Repository

    Thu, Kyaw; Chakraborty, A.; Saha, B.B.; Chun, Won Gee; Ng, K.C.

    2010-01-01

    This paper presents the thermo-economic analysis of the adsorption desalination (AD) cycle that is driven by low-temperature waste heat from exhaust of industrial processes or renewable sources. The AD cycle uses an adsorbent such as the silica gel

  1. On approximating restricted cycle covers

    NARCIS (Netherlands)

    Manthey, Bodo

    2008-01-01

    A cycle cover of a graph is a set of cycles such that every vertex is part of exactly one cycle. An $L$-cycle cover is a cycle cover in which the length of every cycle is in the set $L$. The weight of a cycle cover of an edge-weighted graph is the sum of the weights of its edges. We come close to

  2. Nuclear power fuel cycle

    International Nuclear Information System (INIS)

    Havelka, S.; Jakesova, L.

    1982-01-01

    Economic problems are discussed of the fuel cycle (cost of the individual parts of the fuel cycle and the share of the fuel cycle in the price of 1 kWh), the technological problems of the fuel cycle (uranium ore mining and processing, uranium isotope enrichment, the manufacture of fuel elements, the building of long-term storage sites for spent fuel, spent fuel reprocessing, liquid and gaseous waste processing), and the ecologic aspects of the fuel cycle. (H.S.)

  3. 40 CFR 1065.514 - Cycle-validation criteria for operation over specified duty cycles.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Cycle-validation criteria for operation over specified duty cycles. 1065.514 Section 1065.514 Protection of Environment ENVIRONMENTAL... Over Specified Duty Cycles § 1065.514 Cycle-validation criteria for operation over specified duty...

  4. Benefits of cycle stretchout in pressurized water reactor extended-burnup fuel cycles

    International Nuclear Information System (INIS)

    Matzie, R.A.; Leung, D.C.; Liu, Y.; Beekmann, R.W.

    1981-01-01

    Nuclear reactors are inherently capable of operating for a substantial period beyond their nominal end of cycle (EOC) as a result of negative moderator and fuel temperature coefficients and the decrease in xenon poisoning with lower core power levels. This inherent capability can be used to advantage to reduce annual uranium makeup requirements and cycle energy costs by the use of planned EOC stretchout. This paper discusses the fuel utilization efficiency and economics of both the five-batch, extended-burnup cycle and the three-batch, standard-burnup cycle, which can be improved by employing planned EOC (end of cycle) stretchout. 11 refs

  5. Denatured fuel cycles

    International Nuclear Information System (INIS)

    Till, C.E.

    1979-01-01

    This paper traces the history of the denatured fuel concept and discusses the characteristics of fuel cycles based on the concept. The proliferation resistance of denatured fuel cycles, the reactor types they involve, and the limitations they place on energy generation potential are discussed. The paper concludes with some remarks on the outlook for such cycles

  6. Edgeworth cycles revisited

    International Nuclear Information System (INIS)

    Doyle, Joseph; Muehlegger, Erich; Samphantharak, Krislert

    2010-01-01

    Some gasoline markets exhibit remarkable price cycles, where price spikes are followed by a series of small price declines: a pattern consistent with a model of Edgeworth cycles described by Maskin and Tirole. We extend the model and empirically test its predictions with a new dataset of daily station-level prices in 115 US cities. Consistent with the theory, and often in contrast with previous empirical work, we find the least and most concentrated markets are much less likely to exhibit cycling behavior both within and across cities; areas with more independent convenience-store gas stations are also more likely to cycle. (author)

  7. Fuel cycle management

    International Nuclear Information System (INIS)

    Herbin, H.C.

    1977-01-01

    The fuel cycle management is more and more dependent on the management of the generation means among the power plants tied to the grid. This is due mainly because of the importance taken by the nuclear power plants within the power system. The main task of the fuel cycle management is to define the refuelling pattern of the new and irradiated fuel assemblies to load in the core as a function of: 1) the differences which exist between the actual conditions of the core and what was expected for the present cycle, 2) the operating constraints and the reactor availability, 3) the technical requirements in safety and the technological limits of the fuel, 4) the economics. Three levels of fuel cycle management can be considered: 1) a long term management: determination of enrichments and expected cycle lengths, 2) a mid term management whose aim corresponds to the evaluation of the batch to load within the core as a function of both: the next cycle length to achieve and the integrated power history of all the cycles up to the present one, 3) a short term management which deals with the updating of the loaded fuel utilisations to take into account the operation perturbations, or with the alteration of the loading pattern of the next batch to respect unexpected conditions. (orig.) [de

  8. Exergoeconomic comparison of TLC (trilateral Rankine cycle), ORC (organic Rankine cycle) and Kalina cycle using a low grade heat source

    International Nuclear Information System (INIS)

    Yari, M.; Mehr, A.S.; Zare, V.; Mahmoudi, S.M.S.; Rosen, M.A.

    2015-01-01

    Recently, the TLC (trilateral power cycle) has attracted significant interest as it provides better matching between the temperature profiles in the evaporator compared to conventional power cycles. This article investigates the performance of this cycle and compares it with those for the ORC (organic Rankine cycle) and the Kalina cycle, from the viewpoints of thermodynamics and thermoeconomics. A low-grade heat source with a temperature of 120 °C is considered for all the three systems. Parametric studies are performed for the systems for several working fluids in the ORC and TLC. The systems are then optimized for either maximum net output power or minimum product cost, using the EES (engineering equation solver) software. The results for the TLC indicate that an increase in the expander inlet temperature leads to an increase in net output power and a decrease in product cost for this power plant, whereas this is not the case for the ORC system. It is found that, although the TLC can achieve a higher net output power compared with the ORC and Kalina (KCS11 (Kalina cycle system 11)) systems, its product cost is greatly affected by the expander isentropic efficiency. It is also revealed that using n-butane as the working fluid can result in the lowest product cost in the ORC and the TLC. In addition, it is observed that, for both the ORC and Kalina systems, the optimum operating condition for maximum net output power differs from that for minimum product cost. - Highlights: • Exergoeconomic analysis of trilateral Rankine cycle is performed. • The system performance is compared with Organic Rankine and Kalina cycles. • Net power from trilateral Rankine cycle is higher than the other power systems. • Superiority of trilateral cycle depends on its expander isentropic efficiency

  9. Out-of-core fuel cycle optimization for nonequilibrium cycles

    International Nuclear Information System (INIS)

    Comes, S.A.; Turinsky, P.J.

    1988-01-01

    A methodology has been developed for determining the family of near-optimum fuel management schemes that minimize the levelized fuel cycle costs of a light water reactor over a multicycle planning horizon. Feed batch enrichments and sizes, burned batches to reinsert, and burnable poison loadings are determined for each cycle in the planning horizon. Flexibility in the methodology includes the capability to assess the economic benefits of various partially burned bath reload strategies as well as the effects of using split feed enrichments and enrichment palettes. Constraint limitations are imposed on feed enrichments, discharge burnups, moderator temperature coefficient, and cycle energy requirements

  10. Air bottoming cycle, an alternative to combined cycles. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kaikko, J. [Royal Inst. of Techn., Stockholm (Sweden). Dept. of Energy Technology

    2001-10-01

    In this work, the idea of Air Bottoming Cycle (ABC) has been studied. The objectives for the work have been to establish an understanding of the concept for power and heat generation as well as to find - if possible - feasible concepts for future use in the Swedish energy system. Combined cycle in power generation is an established technology. In the conventional combined cycle, a gas turbine works as a topping cycle together with the steam (Rankine) bottoming cycle. In the ABC the steam bottoming cycle is replaced with a gas turbine (Brayton) bottoming cycle having air as a working fluid. The two gas turbines are thermally connected over a gas-to-gas heat exchanger. This concept promises savings in weight and cost, as well as operating benefits, compared to the Rankine bottoming technology. The ABC has been modelled using a heat balance program, and a parametric study for the concept optimisation as well as for off-design analysis has been performed. Performance of the ABC has been compared to other, established technologies. A preliminary economic evaluation has been made. As a result of the study, it is clarified that the Rankine bottoming cycle with steam remains superior to the ABC as regards electrical efficiency in the medium and large power scale. For small-scale applications (<10 MW{sub e}) where the thermodynamic advantage of the Rankine cycle is not dominating any longer and its economy is burdened by the heavy investment structure, the ABC becomes the better alternative for energy utilisation. A preliminary economic evaluation shows that (at energy prices autumn 2000) the ABC is at the same level as the comparable small-scale cogeneration installations. Due to high power-to-heat ratio however, higher electricity prices will favour the ABC. One interesting feature of the ABC is that about 50% of the dissipated low-value heat from the cycle is carried by clean (sterile) air at the temperature around 200 deg C. This air can be utilised for space heating or

  11. 'Benefits cycle' replacing premium cycle as consumerism takes hold.

    Science.gov (United States)

    2002-05-01

    The traditional premium cycle of ups and downs in rates is giving way to a new phenomenon--driven by the advent of consumerism in health care--termed the "benefits cycle" by one consultant. Rather than shifts in rates, he argues, the future will see shifts in benefits packages.

  12. Natural cycle IVF with and without terminal HCG: learning from failed cycles.

    Science.gov (United States)

    Lenton, Elizabeth A

    2007-08-01

    Natural cycle IVF, without the use of LH down-regulation, is difficult because women start spontaneous LH surges at any time of the day and on any day of the week. This is not readily compatible with delivery of a routine IVF service and so historically the natural cycle has been modified by the use of human chorionic gonadotrophin (HCG) to make the natural cycle fit convenient clinical practice. This report re-evaluates data collected some years ago and seeks to determine whether the use of HCG is ultimately beneficial. Two large series of natural cycle IVF where only LH monitoring was performed (534 cycles) or where this was combined with HCG as necessary (241 cycles) were analysed. In essence, the use of HCG introduced as many problems as it overcame: there was no net benefit with respect to the number of eggs collected or clinical pregnancies generated. In fact there was an overall deterioration in all indices. The principle difficulties with natural cycle IVF are those associated with the prediction of follicle maturity and hence timing egg collection, and the conflict between costly and intrusively frequent monitoring with simpler but far less effective approaches.

  13. Dual Expander Cycle Rocket Engine with an Intermediate, Closed-cycle Heat Exchanger

    Science.gov (United States)

    Greene, William D. (Inventor)

    2008-01-01

    A dual expander cycle (DEC) rocket engine with an intermediate closed-cycle heat exchanger is provided. A conventional DEC rocket engine has a closed-cycle heat exchanger thermally coupled thereto. The heat exchanger utilizes heat extracted from the engine's fuel circuit to drive the engine's oxidizer turbomachinery.

  14. Ammonia-water Rankine cycle

    International Nuclear Information System (INIS)

    Bo Hanliang; Ma Changwen; Wu Shaorong

    1997-01-01

    On characteristics of heating source and cooling source in nuclear heating reactor cooperation, the authors advance a new kind of power cycle in which a multicomponent mixture as the work fluid, ammonia-water Rankine cycle, describe its running principle, and compare it with steam Rankine cycle in the same situation. The result is that: the new kind of power cycle, ammonia-water Rankine cycle has higher electricity efficiency; it suits for the situation of heating source and cooling source which offered by nuclear heating reactor cooperation. For low temperature heating source, it maybe has a widely application

  15. Study on the supercritical CO2 power cycles for landfill gas firing gas turbine bottoming cycle

    International Nuclear Information System (INIS)

    Kim, Min Seok; Ahn, Yoonhan; Kim, Beomjoo; Lee, Jeong Ik

    2016-01-01

    In this paper, a comparison of nine supercritical carbon dioxide (S-CO 2 ) bottoming power cycles in conjunction with a topping cycle of landfill gas (LFG) fired 5MWe gas turbine is presented. For the comparison purpose, a sensitivity study of the cycle design parameters for nine different cycles was conducted and each cycle thermodynamic performance is evaluated. In addition, the cycle performance evaluation dependency on the compressor inlet temperature variation is performed to investigate how S-CO 2 cycles sensitive to the heat sink temperature variation. Furthermore, the development of new S-CO 2 cycle layouts is reported and the suggested cycles' performances are compared to the existing cycle layouts. It was found that a recompression cycle is not suitable for the bottoming cycle application, but a partial heating cycle has relatively higher net produced work with a simple layout and small number of components. Although a dual heated and flow split cycle has the highest net produced work, it has disadvantages of having numerous components and complex process which requires more sophisticated operational strategies. This study identified that the recuperation process is much more important than the intercooling process to the S-CO 2 cycle design for increasing the thermal efficiency and the net produced work point of view. - Highlights: • Study of nine S-CO 2 power cycle layouts for a small scale landfill gas power generation application. • Development of new S-CO 2 cycle layouts. • Sensitivity analysis of S-CO 2 cycles to evaluate and compare nine cycles' performances.

  16. A comparison of advanced heat recovery power cycles in a combined cycle for large ships

    International Nuclear Information System (INIS)

    Larsen, Ulrik; Sigthorsson, Oskar; Haglind, Fredrik

    2014-01-01

    Strong motivation exists within the marine sector to reduce fuel expenses and to comply with ever stricter emission regulations. Heat recovery can address both of these issues. The ORC (organic Rankine cycle), the Kalina cycle and the steam Rankine cycle have received the majority of the focus in the literature. In the present work we compare these cycles in a combined cycle application with a large marine two-stroke diesel engine. We present an evaluation of the efficiency and the environmental impact, safety concerns and practical aspects of each of the cycles. A previously validated numerical engine model is combined with a turbocharger model and bottoming cycle models written in Matlab. Genetic algorithm optimisation results suggest that the Kalina cycle possess no significant advantages compared to the ORC or the steam cycle. While contributing to very high efficiencies, the organic working fluids possess high global warming potentials and hazard levels. It is concluded that the ORC has the greatest potential for increasing the fuel efficiency, and the combined cycle offers very high thermal efficiency. While being less efficient, the steam cycle has the advantages of being well proven, harmless to the environment as well as being less hazardous in comparison. - Highlights: • We compare steam, ORC (organic Rankine cycle) and Kalina cycles for waste heat recovery in marine engines. • We evaluate the efficiency and important qualitative differences. • The Kalina cycle presents no apparent advantages. • The steam cycle is well known, harmless and has a high efficiency. • The ORC has the highest efficiency but also important drawbacks

  17. Effect of cycle coupling-configuration on energy cascade utilization for a new power and cooling cogeneration cycle

    International Nuclear Information System (INIS)

    Jing, Xuye; Zheng, Danxing

    2014-01-01

    Highlights: • A new power and cooling cogeneration cycle was proposed. • The thermophysical properties and the performance of the new cycle were calculated. • Different cycle coupling-configurations were analyzed. • The energy efficiency boosting mechanism of the new cycle was elucidated. - Abstract: To recover mid-low grade heat, a new power/cooling cogeneration cycle was proposed by combining the Kalina cycle and the double-effect ammonia–water absorption refrigeration (DAAR) cycle together, and the equivalent heat-to-power and exergy efficiencies of the cogeneration cycle reached 41.18% and 58.00%, respectively. To determine the effect of cycle coupling-configuration on energy cascade utilization for the new cycle, the cycle coupling-configuration of the Kalina and DAAR cycles were first analyzed, after which the cycle coupling-configuration of the new cycle was analyzed. Analysis results showed that the cycle coupling-configuration of the new cycle enhanced the energy cascade utilization. Furthermore, the energy efficiency boosting mechanism of the new cycle was elucidated

  18. Air bottoming cycle, an alternative to combined cycles. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kaikko, J. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Energy Technology

    2002-02-01

    In this work, the idea of Air Bottoming Cycle (ABC) has been studied. The objectives for the work have been to establish an understanding of the concept for power and heat generation as well as to find - if possible - feasible concepts for future use in the Swedish energy system. Combined cycle in power generation is an established technology. In the conventional combined cycle, a gas turbine works as a topping cycle together with the steam (Rankine) bottoming cycle. In the ABC the steam bottoming cycle is replaced with a gas turbine (Brayton) bottoming cycle having air as a working fluid. The two gas turbines are thermally connected over a gas-to-gas heat exchanger. This concept promises savings in weight and cost, as well as operating benefits, compared to the Rankine bottoming technology. The ABC has been modelled using a heat balance program, and a parametric study for the concept optimisation as well as for off-design analysis has been performed. Performance of the ABC has been compared to other, established technologies. A preliminary economic evaluation has been made. As a result of the study, it is clarified that the Rankine bottoming cycle with steam remains superior to the ABC as regards electrical efficiency in the medium and large power scale. For small-scale applications (<10 MW{sub e}) where the thermodynamic advantage of the Rankine cycle is not dominating any longer and its economy is burdened by the heavy investment structure, the ABC becomes the better alternative for energy utilisation. A preliminary economic evaluation shows that (at energy prices autumn 2000) the ABC is at the same level as the comparable small-scale cogeneration installations. Due to high power-to-heat ratio however, higher electricity prices will favour the ABC. One interesting feature of the ABC is that about 50% of the dissipated low-value heat from the cycle is carried by clean (sterile) air at the temperature around 200 deg C. This air can be utilised for space heating or

  19. Very high cycle fatigue testing of concrete using ultrasonic cycling

    Energy Technology Data Exchange (ETDEWEB)

    Karr, Ulrike; Schuller, Reinhard; Fitzka, Michael; Mayer, Herwig [Univ. of Natural Resources and Life Sciences, Vienna (Austria). Inst. of Physics and Materials Science; Denk, Andreas; Strauss, Alfred [Univ. of Natural Resources and Life Sciences, Vienna (Austria)

    2017-06-01

    The ultrasonic fatigue testing method has been further developed to perform cyclic compression tests with concrete. Cylindrical specimens vibrate in resonance at a frequency of approximately 20 kHz with superimposed compressive static loads. The high testing frequency allows time-saving investigations in the very high cycle fatigue regime. Fatigue tests were carried out on ''Concrete 1'' (compressive strength f{sub c} = 80 MPa) and ''Concrete 2'' (f{sub c} = 107 MPa) under purely compressive loading conditions. Experiments at maximum compressive stresses of 0.44 f{sub c} (Concrete 1) and 0.38 f{sub c} (Concrete 2) delivered specimen failures above 109 cycles, indicating that no fatigue limit exists for concrete below one billion load cycles. Resonance frequency, power required to resonate the specimen and second order harmonics of the vibration are used to monitor fatigue damage in situ. Specimens were scanned by X-ray computed tomography prior to and after testing. Fatigue cracks were produced by ultrasonic cycling in the very high cycle fatigue regime at interfaces of grains as well as in cement. The possibilities as well as limitations of ultrasonic fatigue testing of concrete are discussed.

  20. International Business Cycle

    OpenAIRE

    Marek Lubiński

    2007-01-01

    Prime stylized facts of international business cycle theory refer to positive correlation in the cyclical components of important macroeconomic variables across countries. However a number of indicators of business cycle synchronization do not point to clear trends. It can be ascribed to the fact that different forces influence level of business cycle correlation. When investigating into the forces behind the commonness in aggregate fluctuations economic research seems to have pointed in two ...

  1. Nuclear fuel cycle system analysis

    International Nuclear Information System (INIS)

    Ko, W. I.; Kwon, E. H.; Kim, S. G.; Park, B. H.; Song, K. C.; Song, D. Y.; Lee, H. H.; Chang, H. L.; Jeong, C. J.

    2012-04-01

    The nuclear fuel cycle system analysis method has been designed and established for an integrated nuclear fuel cycle system assessment by analyzing various methodologies. The economics, PR(Proliferation Resistance) and environmental impact evaluation of the fuel cycle system were performed using improved DB, and finally the best fuel cycle option which is applicable in Korea was derived. In addition, this research is helped to increase the national credibility and transparency for PR with developing and fulfilling PR enhancement program. The detailed contents of the work are as follows: 1)Establish and improve the DB for nuclear fuel cycle system analysis 2)Development of the analysis model for nuclear fuel cycle 3)Preliminary study for nuclear fuel cycle analysis 4)Development of overall evaluation model of nuclear fuel cycle system 5)Overall evaluation of nuclear fuel cycle system 6)Evaluate the PR for nuclear fuel cycle system and derive the enhancement method 7)Derive and fulfill of nuclear transparency enhancement method The optimum fuel cycle option which is economical and applicable to domestic situation was derived in this research. It would be a basis for establishment of the long-term strategy for nuclear fuel cycle. This work contributes for guaranteeing the technical, economical validity of the optimal fuel cycle option. Deriving and fulfillment of the method for enhancing nuclear transparency will also contribute to renewing the ROK-U.S Atomic Energy Agreement in 2014

  2. KOH concentration effect on cycle life of nickel-hydrogen cells. III - Cycle life test

    Science.gov (United States)

    Lim, H. S.; Verzwyvelt, S. A.

    1988-01-01

    A cycle life test of Ni/H2 cells containing electrolytes of various KOH concentrations and a sintered type nickel electrode was carried out at 23 C using a 45 min accelerated low earth orbit (LEO) cycle regime at 80 percent depth of discharge. One of three cells containing 26 percent KOH has achieved over 28,000 cycles, and the other two 19,000 cycles, without a sign of failure. Two other cells containing 31 percent KOH electrolyte, which is the concentration presently used in aerospace cells, failed after 2,979 and 3,620 cycles. This result indicates that the cycle life of the present type of Ni/H2 cells may be extended by a factor of 5 to 10 simply by lowering the KOH concentration. Long cycle life of a Ni/H2 battery at high depth-of-discharge operation is desired, particularly for an LEO spacecraft application. Typically, battery life of about 30,000 cycles is required for a five year mission in an LEO. Such a cycle life with presently available cells can be assured only at a very low depth-of-discharge operation. Results of testing already show that the cycle life of an Ni/H2 cell is tremendously improved by simply using an electrolyte of low KOH concentration.

  3. Driving and engine cycles

    CERN Document Server

    Giakoumis, Evangelos G

    2017-01-01

    This book presents in detail the most important driving and engine cycles used for the certification and testing of new vehicles and engines around the world. It covers chassis and engine-dynamometer cycles for passenger cars, light-duty vans, heavy-duty engines, non-road engines and motorcycles, offering detailed historical information and critical review. The book also provides detailed examples from SI and diesel engines and vehicles operating during various cycles, with a focus on how the engine behaves during transients and how this is reflected in emitted pollutants, CO2 and after-treatment systems operation. It describes the measurement methods for the testing of new vehicles and essential information on the procedure for creating a driving cycle. Lastly, it presents detailed technical specifications on the most important chassis-dynamometer cycles around the world, together with a direct comparison of those cycles.

  4. The heat engine cycle, the heat removal cycle, and ergonomics of the control room displays

    International Nuclear Information System (INIS)

    Beltracchi, L.

    1986-01-01

    This paper discusses and illustrates the ergonomics of an integrated display, which will allow operators to monitor the heat engine cycle during normal operation of the plant, and the heat removal cycle during emergency operation of the plant. A computer-based iconic display is discussed as an overview to monitor these cycles. Specific emphasis is placed upon the process variables and process functions within each cycle, and the action of control systems and engineered safeguard systems within each cycle. This paper contains examples of display formats for the heat engine cycle and the heat removal cycle in a pressurized water reactor

  5. Novel combined cycle configurations for propane pre-cooled mixed refrigerant (APCI) natural gas liquefaction cycle

    International Nuclear Information System (INIS)

    Mortazavi, Amir; Alabdulkarem, Abdullah; Hwang, Yunho; Radermacher, Reinhard

    2014-01-01

    Highlights: • 10 New LNG plants driver cycle enhancement configurations were developed. • All the 14 enhancement options design variables were optimized to demonstrate their energy saving potentials. • The best driver cycle enhancement option improved the driver cycle energy efficiency by 38%. • The effects of technological advancements on the performances of the enhancement options were studied. - Abstract: A significant amount of energy is required for natural gas liquefaction. Due to the production scale of LNG plants, they consume an intensive amount of energy. Consequently, any enhancement to the energy efficiency of LNG plants will result in a considerable reduction in natural gas consumption and CO 2 emission. Compressor drivers are the main energy consumer in the LNG plants. In this paper, 14 different driver cycle enhancement options were considered. A number of these options have not been proposed for the LNG plants. The new driver cycle development was performed by analyzing and optimizing the design variables of four conventional driver cycle enhancement options. The optimization results were used to develop more efficient cycles through mitigating the active constrains and driver cycle innovations. Based on the current available technologies five of our newly developed driver cycle configurations have higher efficiency than the most efficient existing conventional driver cycle. The best developed driver cycle enhancement option improved the base driver cycle energy efficiency by 38%. The effects of technological advancement on the performances of the all driver cycle enhancement options were also considered

  6. Chords in longest cycles

    DEFF Research Database (Denmark)

    Thomassen, Carsten

    2017-01-01

    If a graph G is 3-connected and has minimum degree at least 4, then some longest cycle in G has a chord. If G is 2-connected and cubic, then every longest cycle in G has a chord.......If a graph G is 3-connected and has minimum degree at least 4, then some longest cycle in G has a chord. If G is 2-connected and cubic, then every longest cycle in G has a chord....

  7. Temporal fluxomics reveals oscillations in TCA cycle flux throughout the mammalian cell cycle.

    Science.gov (United States)

    Ahn, Eunyong; Kumar, Praveen; Mukha, Dzmitry; Tzur, Amit; Shlomi, Tomer

    2017-11-06

    Cellular metabolic demands change throughout the cell cycle. Nevertheless, a characterization of how metabolic fluxes adapt to the changing demands throughout the cell cycle is lacking. Here, we developed a temporal-fluxomics approach to derive a comprehensive and quantitative view of alterations in metabolic fluxes throughout the mammalian cell cycle. This is achieved by combining pulse-chase LC-MS-based isotope tracing in synchronized cell populations with computational deconvolution and metabolic flux modeling. We find that TCA cycle fluxes are rewired as cells progress through the cell cycle with complementary oscillations of glucose versus glutamine-derived fluxes: Oxidation of glucose-derived flux peaks in late G1 phase, while oxidative and reductive glutamine metabolism dominates S phase. These complementary flux oscillations maintain a constant production rate of reducing equivalents and oxidative phosphorylation flux throughout the cell cycle. The shift from glucose to glutamine oxidation in S phase plays an important role in cell cycle progression and cell proliferation. © 2017 The Authors. Published under the terms of the CC BY 4.0 license.

  8. Alternative fuel cycles

    International Nuclear Information System (INIS)

    Penn, W.J.

    1979-05-01

    Uranium resource utilization and economic considerations provide incentives to study alternative fuel cycles as future options to the PHWR natural uranium cycle. Preliminary studies to define the most favourable alternatives and their possible introduction dates are discussed. The important and uncertain components which influence option selection are reviewed, including nuclear capacity growth, uranium availability and demand, economic potential, and required technological developments. Finally, a summary of Ontario Hydro's program to further assess cycle selection and define development needs is given. (auth)

  9. Lunar base heat pump, phase 1

    Science.gov (United States)

    Goldman, Jeffrey H.; Harvey, A.; Lovell, T.; Walker, David H.

    1994-01-01

    This report describes the Phase 1 process and analysis used to select a refrigerant and thermodynamic cycle as the basis of a vapor compression heat pump requiring a high temperature lift, then to perform a preliminary design to implement the selected concept, including major component selection. Use of a vapor compression heat pump versus other types was based on prior work performed for the Electric Power Research Institute. A high lift heat pump is needed to enable a thermal control system to remove heat down to 275 K from a habitable volume when the external thermal environment is severe. For example, a long-term lunar base habitat will reject heat from a space radiator to a 325 K environment. The first step in the selection process was to perform an optimization trade study, quantifying the effect of radiator operating temperature and heat pump efficiency on total system mass; then, select the radiator operating temperature corresponding to the lowest system mass. Total system mass included radiators, all heat pump components, and the power supply system. The study showed that lunar night operation, with no temperature lift, dictated the radiator size. To operate otherwise would require a high mass penalty to store power. With the defined radiation surface, and heat pump performances assumed to be from 40 percent to 60 percent of the Carnot ideal, the optimum heat rejection temperature ranged from 387 K to 377 K, as a function of heat pump performance. Refrigerant and thermodynamic cycles were then selected to best meet the previously determined design conditions. The system was then adapted as a ground-based prototype lifting temperature to 360 K (versus 385 K for flight unit) and using readily available commercial-grade components. Over 40 refrigerants, separated into wet and dry compression behavioral types, were considered in the selection process. Refrigerants were initially screened for acceptable critical temperature. The acceptable refrigerants were

  10. Educational Business Cycles

    DEFF Research Database (Denmark)

    Tepe, Markus; Vanhuysse, Pieter

    Strong institutional constraints and better-informed voters may lead re-election seeking incumbents to shift the use of political business cycle mechanisms away from monetary and fiscal policy towards other policy domains that are more easily manipulable, targetable, and timeable. We investigate...... teacher employment patterns at the state level in Germany and find strong evidence of cycling mechanisms, in the form of electioneering and honeymooning. Against a backdrop of a continuously shrinking total teachers' pool, German state-level incumbents accelerate the hiring of new teachers during election...... periods and partly reverse this during politically safer points in the electoral cycle. Cycles are mediated by issue salience: heightened attention to German public schooling after the notorious PISA-2000 tests further strengthens the manipulation of new teacher hiring for electoral purposes....

  11. Educational Business Cycles

    DEFF Research Database (Denmark)

    Tepe, Markus; Vanhuysse, Pieter

    2009-01-01

    Strong institutional constraints and better-informed voters may lead re-election seeking incumbents to shift the use of political business cycle mechanisms away from monetary and fiscal policy towards other policy domains that are more easily manipulable, targetable, and timeable. We investigate...... teacher employment patterns at the state level in Germany and find strong evidence of cycling mechanisms, in the form of electioneering and honeymooning. Against a backdrop of a continuously shrinking total teachers' pool, German state-level incumbents accelerate the hiring of new teachers during election...... periods and partly reverse this during politically safer points in the electoral cycle. Cycles are mediated by issue salience: heightened attention to German public schooling after the notorious PISA-2000 tests further strengthens the manipulation of new teacher hiring for electoral purposes....

  12. Termination of cycle rewriting

    NARCIS (Netherlands)

    Zantema, H.; König, B.; Bruggink, H.J.S.; Dowek, G.

    2014-01-01

    String rewriting can not only be applied on strings, but also on cycles and even on general graphs. In this paper we investigate termination of string rewriting applied on cycles, shortly denoted as cycle rewriting, which is a strictly stronger requirement than termination on strings. Most

  13. The Nuclear Fuel Cycle

    International Nuclear Information System (INIS)

    2011-08-01

    This brochure describes the nuclear fuel cycle, which is an industrial process involving various activities to produce electricity from uranium in nuclear power reactors. The cycle starts with the mining of uranium and ends with the disposal of nuclear waste. The raw material for today's nuclear fuel is uranium. It must be processed through a series of steps to produce an efficient fuel for generating electricity. Used fuel also needs to be taken care of for reuse and disposal. The nuclear fuel cycle includes the 'front end', i.e. preparation of the fuel, the 'service period' in which fuel is used during reactor operation to generate electricity, and the 'back end', i.e. the safe management of spent nuclear fuel including reprocessing and reuse and disposal. If spent fuel is not reprocessed, the fuel cycle is referred to as an 'open' or 'once-through' fuel cycle; if spent fuel is reprocessed, and partly reused, it is referred to as a 'closed' nuclear fuel cycle.

  14. Can cycling safety be improved by opening all unidirectional cycle paths for cycle traffic in both directions? A theoretical examination of available literature and data.

    Science.gov (United States)

    Methorst, Rob; Schepers, Paul; Kamminga, Jaap; Zeegers, Theo; Fishman, Elliot

    2017-08-01

    Many studies have found bicycle-motor vehicle crashes to be more likely on bidirectional cycle paths than on unidirectional cycle paths because drivers do not expect cyclists riding at the right side of the road. In this paper we discuss the hypothesis that opening all unidirectional cycle paths for cycle traffic in both directions prevent this lack of expectancy and accordingly improves cycling safety. A new national standard requires careful consideration because a reversal is difficult once cyclists are used to their new freedom of route choice. We therefore explored the hypothesis using available data, research, and theories. The results show that of the length of cycle paths along distributor roads in the Netherlands, 72% is bidirectional. If drivers would become used to cyclists riding at the left side of the road, this result raises the question of why bidirectional cycle paths in the Netherlands still have a poor safety record compared to unidirectional cycle paths. Moreover, our exploration suggested that bidirectional cycle paths have additional safety problems. It increases the complexity of unsignalized intersections because drivers have to scan more directions in a short period of time. Moreover, there are some indications that the likelihood of frontal crashes between cyclists increases. We reject the hypothesis that opening all unidirectional cycle paths for cycle traffic in both directions will improve cycle safety. We recommend more attention for mitigating measures given the widespread application of bidirectional cycle paths in the Netherlands. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Nuclear Fuel Cycle Information System. A directory of nuclear fuel cycle facilities. 2009 ed

    International Nuclear Information System (INIS)

    2009-04-01

    The Nuclear Fuel Cycle Information System (NFCIS) is an international directory of civilian nuclear fuel cycle facilities, published online as part of the Integrated Nuclear Fuel Cycle Information System (iNFCIS: http://www-nfcis.iaea.org/). This is the fourth hardcopy publication in almost 30 years and it represents a snapshot of the NFCIS database as of the end of 2008. Together with the attached CD-ROM, it provides information on 650 civilian nuclear fuel cycle facilities in 53 countries, thus helping to improve the transparency of global nuclear fuel cycle activities

  16. Entrepreneurship and the business cycle

    NARCIS (Netherlands)

    Koellinger, Philipp D.; Thurik, A. Roy

    2012-01-01

    We find new empirical regularities in the business cycle in a cross-country panel of 22 OECD countries for the period 1972 to 2007; entrepreneurship Granger-causes the cycles of the world economy. Furthermore, the entrepreneurial cycle is positively affected by the national unemployment cycle. We

  17. Continuation of connecting orbits in 3d-ODEs. (ii) cycle-to-cycle connections.

    NARCIS (Netherlands)

    Doedel, E.J.; Kooi, B.W.; van Voorn, G.A.K.; Kuznetzov, Y.A.

    2009-01-01

    In Part I of this paper we have discussed new methods for the numerical continuation of point-to-cycle connecting orbits in three-dimensional autonomous ODE's using projection boundary conditions. In this second part we extend the method to the numerical continuation of cycle-to-cycle connecting

  18. LIFE CYCLE OF INFORMATION SYSTEMS

    Directory of Open Access Journals (Sweden)

    Y. S. Sennik

    2015-01-01

    Full Text Available This work is a generalization of the theoretical propositions related to the life cycle of information systems. There was given the definition of the life cycle, specify which items you should include every step of the cycle. Describes the methodology division of the life cycle on the main stage, including methodology Rational Unified Process. The description of the fundamental standards in this area. Special attention was paid to the work of the basic life cycle models. It was carried out their comparative characteristics. On the basis of the theoretical propositions, it was concluded that the preferred model of the life cycle for the corporate network is a spiral model and the use of international standards in the life cycle saves a lot of effort, time and material resources.

  19. Increasing thermal efficiency of Rankine cycles by using refrigeration cycles: A theoretical analysis

    International Nuclear Information System (INIS)

    Sarr, Joachim-André Raymond; Mathieu-Potvin, François

    2016-01-01

    Highlights: • A new stratagem is proposed to improve thermal efficiency of Rankine cycles. • Three new configurations are optimized by means of numerical simulations. • The Rankine-1SCR design is advantageous for 1338 different fluid combinations. • The Rankine-2SCR design is advantageous for 772 different fluid combinations. • The Rankine-3SCR design is advantageous for 768 different fluid combinations. - Abstract: In this paper, three different modifications of the basic Rankine thermodynamic cycle are proposed. The objective is to increase the thermal efficiency of power systems based on Rankine cycles. The three new systems are named “Rankine-1SCR”, “Rankine-2SCR”, and “Rankine-3SCR” cycles, and they consist of linking a refrigeration cycle to the basic Rankine cycle. The idea is to use the refrigeration cycle to create a low temperature heat sink for the Rankine cycle. These three new power plant configurations are modeled and optimized with numerical tools, and then they are compared with the basic Rankine cycle. The objective function is the thermal efficiency of the systems (i.e., net power output (kW) divided by heat rate (kW) entering the system), and the design variables are the operating temperatures within the systems. Among the 84 × 84 (i.e., 7056) possible combinations of working and cooling fluids investigated in this paper, it is shown that: (i) the Rankine-1SCR system is advantageous for 1338 different fluid combinations, (ii) the Rankine-2SCR system is advantageous for 772 different fluid combinations, and (iii) the Rankine-3SCR system is advantageous for 768 different fluid combinations.

  20. Hybrid Combined Cycles with Biomass and Waste Fired Bottoming Cycle - a Literature Study

    Energy Technology Data Exchange (ETDEWEB)

    Petrov, Miroslav P.

    2002-02-01

    Biomass is one of the main natural resources in Sweden. The present low-CO{sub 2} emission characteristics of the Swedish electricity production system (hydro and nuclear) can be retained only by expansion of biofuel applications for energy purposes. Domestic Swedish biomass resources are vast and renewable, but not infinite. They must be utilized as efficiently as possible, in order to make sure that they meet the conditions for sustainability in the future. Application of efficient power generation cycles at low costs is essential for meeting this challenge. This applies also to municipal solid waste incineration with energy extraction, which should be preferred to its dumping in landfills. Hybrid dual-fuel combined cycle units are a simple and affordable way to increase the electric efficiency of biofuel energy utilization, without big investments, uncertainties or loss of reliability arising from complicated technologies. Configurations of such power cycles are very flexible and reliable. Their potential for high electric efficiency in condensing mode, high total efficiency in combined heat and power mode and unrivalled load flexibility is explored in this project. The present report is a literature study that concentrates on certain biomass utilization technologies, in particular the design and performance of hybrid combined cycle power units of various configurations, with gas turbines and internal combustion engines as topping cycles. An overview of published literature and general development trends on the relevant topic is presented. The study is extended to encompass a short overview of biomass utilization as an energy source (focusing on Sweden), history of combined cycles development with reference especially to combined cycles with supplementary firing and coal-fired hybrid combined cycles, repowering of old steam units into hybrid ones and combined cycles for internal combustion engines. The hybrid combined cycle concept for municipal solid waste

  1. They gave their names to science

    National Research Council Canada - National Science Library

    Halacy, D. S

    1967-01-01

    ...: Ernst Mach and his number, Gergor Mendel and his laws, Christian Johann Doppler and his effect, Hans Geiger and his radiation counter, Nicholas Sadi Carnot and thermodynamics, Gustave, Gaspard de...

  2. High-intensity cycle interval training improves cycling and running performance in triathletes.

    Science.gov (United States)

    Etxebarria, Naroa; Anson, Judith M; Pyne, David B; Ferguson, Richard A

    2014-01-01

    Effective cycle training for triathlon is a challenge for coaches. We compared the effects of two variants of cycle high-intensity interval training (HIT) on triathlon-specific cycling and running. Fourteen moderately-trained male triathletes ([Formula: see text]O2peak 58.7 ± 8.1 mL kg(-1) min(-1); mean ± SD) completed on separate occasions a maximal incremental test ([Formula: see text]O2peak and maximal aerobic power), 16 × 20 s cycle sprints and a 1-h triathlon-specific cycle followed immediately by a 5 km run time trial. Participants were then pair-matched and assigned randomly to either a long high-intensity interval training (LONG) (6-8 × 5 min efforts) or short high-intensity interval training (SHORT) (9-11 × 10, 20 and 40 s efforts) HIT cycle training intervention. Six training sessions were completed over 3 weeks before participants repeated the baseline testing. Both groups had an ∼7% increase in [Formula: see text]O2peak (SHORT 7.3%, ±4.6%; mean, ±90% confidence limits; LONG 7.5%, ±1.7%). There was a moderate improvement in mean power for both the SHORT (10.3%, ±4.4%) and LONG (10.7%, ±6.8%) groups during the last eight 20-s sprints. There was a small to moderate decrease in heart rate, blood lactate and perceived exertion in both groups during the 1-h triathlon-specific cycling but only the LONG group had a substantial decrease in the subsequent 5-km run time (64, ±59 s). Moderately-trained triathletes should use both short and long high-intensity intervals to improve cycling physiology and performance. Longer 5-min intervals on the bike are more likely to benefit 5 km running performance.

  3. Combined Turbine and Cycle Optimization for Organic Rankine Cycle Power Systems—Part A

    DEFF Research Database (Denmark)

    Meroni, Andrea; La Seta, Angelo; Andreasen, Jesper Graa

    2016-01-01

    Axial-flow turbines represent a well-established technology for a wide variety of power generation systems. Compactness, flexibility, reliability and high efficiency have been key factors for the extensive use of axial turbines in conventional power plants and, in the last decades, in organic...... Rankine cycle power systems. In this two-part paper, an overall cycle model and a model of an axial turbine were combined in order to provide a comprehensive preliminary design of the organic Rankine cycle unit, taking into account both cycle and turbine optimal designs. Part A presents the preliminary...

  4. Menstrual cycle pattern and fertility

    DEFF Research Database (Denmark)

    Kolstad, Henrik A.; Bonde, Jens Peter; Hjøllund, Niels Henrik

    1999-01-01

    To characterize how the menstrual cycle pattern relates to fertility regardless of potential biases caused by inappropriate coital timing during the menstrual cycle or early embryonal loss.......To characterize how the menstrual cycle pattern relates to fertility regardless of potential biases caused by inappropriate coital timing during the menstrual cycle or early embryonal loss....

  5. Spatio-temporal structure and cycle to cycle variations of an in-cylinder tumbling flow

    Science.gov (United States)

    Voisine, M.; Thomas, L.; Borée, J.; Rey, P.

    2011-05-01

    The aim of this paper is to make use of PIV and high-speed PIV in a research engine of moderate tumbling ratio in order to analyze both the spatial structure of the flow and its temporal evolution during series of consecutive cycles. Appropriate analyzing tools are introduced, and four different points are addressed: (1) the chain of events driving the generation of the three-dimensional mean tumbling motion is investigated; (2) a Lagrangian analysis of the roll-up of the tumbling jet in individual cycles demonstrates a strong cycle to cycle variation during the compression phase (the rms of the position of the jet front being approximately 10% of the piston stroke); (3) focussing on the "breakdown" phase, phase invariant proper orthogonal decomposition enables us to distinguish cycles according to their structure near top dead center (TDC). We show that when the coherent energy of the flow is conserved, there is no increase in the fluctuating kinetic energy; (4) finally, the phase-averaged Reynolds stresses is decomposed into a contribution of the in-cycle coherence and the turbulence carried by the flow states. Approximately 30% of the fluctuating kinetic energy is due to cycle to cycle fluctuations in this chamber near TDC.

  6. Evolution of the Second Law of Thermodynamics

    Science.gov (United States)

    Raman, V. V.

    1970-01-01

    Presents the history surrounding the evolution of the second law of thermodynamics. Discusses Sadi Carnot's contributions, but also refers to those by Clapeyron, Thomson, Joule, Clausius, and Boltzman among others. (RR)

  7. Nutrient cycling strategies.

    NARCIS (Netherlands)

    Breemen, van N.

    1995-01-01

    This paper briefly reviews pathways by which plants can influence the nutrient cycle, and thereby the nutrient supply of themselves and of their competitors. Higher or lower internal nutrient use efficiency positively feeds back into the nutrient cycle, and helps to increase or decrease soil

  8. Universal cycle periods

    NARCIS (Netherlands)

    Groot, de E.A. (Bert); Franses, P.H.P.H.

    2009-01-01

    We present a meta-analysis of cycles in historical economic data. The literature on stochastic and deterministic cycles in variables such as the consumer price index, employment, interest rates, commodity prices, and GDP is huge and scattered, but our meta-analysis reveals various communalities. Our

  9. Predicting the start and maximum amplitude of solar cycle 24 using similar phases and a cycle grouping

    International Nuclear Information System (INIS)

    Wang Jialong; Zong Weiguo; Le Guiming; Zhao Haijuan; Tang Yunqiu; Zhang Yang

    2009-01-01

    We find that the solar cycles 9, 11, and 20 are similar to cycle 23 in their respective descending phases. Using this similarity and the observed data of smoothed monthly mean sunspot numbers (SMSNs) available for the descending phase of cycle 23, we make a date calibration for the average time sequence made of the three descending phases of the three cycles, and predict the start of March or April 2008 for cycle 24. For the three cycles, we also find a linear correlation of the length of the descending phase of a cycle with the difference between the maximum epoch of this cycle and that of its next cycle. Using this relationship along with the known relationship between the rise-time and the maximum amplitude of a slowly rising solar cycle, we predict the maximum SMSN of cycle 24 of 100.2 ± 7.5 to appear during the period from May to October 2012. (letters)

  10. Associations between urban form and cycling

    DEFF Research Database (Denmark)

    Nielsen, Thomas Alexander Sick; Olafsson, Anton Stahl; Carstensen, Trine Agervig

    of National Travel Survey data indicated that established walkability factors such as density, connectivity and diversity are related to cycling, and that access to retail concentrations/centres, public transportation level-of-service, as well as competition between walking and cycling depending...... of cycling and the distance cycled. A high probability of cycling generally implies short cycling distances, which leads to non-uniform, non-monotonous relations between environmental indicators such as walkability and total cycling. Further analysis of primary data allowing a consideration of attitudes...

  11. Characterizing cycle-to-cycle variations of the shedding cycle in the turbulent wake of a normal flat plate using generalized phase averages

    Science.gov (United States)

    Martinuzzi, Robert

    2016-11-01

    Quasi-periodic vortex shedding in the turbulent wake of a thin-flat plate placed normal to a uniform stream at Reynolds number of 6700 is investigated based on Particle Image Velocimetry experiments. The wake structure and vortex formation are characterized using a generalized phase average (GPA), a refinement of the triple decomposition of Reynolds and Hussain (1970) incorporating elements of mean-field theory (Stuart, 1958). The resulting analysis highlights the importance of cycle-to-cycle variations in characterizing vortex formation, wake topology and the residual turbulent Reynolds Stresses. For example, it is shown that during high-amplitude cycles vorticity is strongly concentrated within the well-organized shed vortices, whereas during low-amplitude cycles the shed vortices are highly distorted resulting in significant modulation of the shedding frequency. It is found that high-amplitude cycles contribute more to the coherent Reynolds stress field while the low-amplitude cycles contribute to the residual stress field. It is further shown that traditional phase-averaging techniques lead to an over-estimation of the residual stress field. Natural Sciences and Engineering Research Council of Canada.

  12. Stability through cycles

    NARCIS (Netherlands)

    E.A. de Groot (Bert); Ph.H.B.F. Franses (Philip Hans)

    2006-01-01

    textabstractEconomic variables like GDP growth, employment, interest rates and consumption show signs of cyclical behavior. Many variables display multiple cycles, with lengths ranging in between 5 to even up to 100 years. We argue that multiple cycles can be associated with long-run stability of

  13. Economics analysis of fuel cycle cost of fusion–fission hybrid reactors based on different fuel cycle strategies

    Energy Technology Data Exchange (ETDEWEB)

    Zu, Tiejun, E-mail: tiejun@mail.xjtu.edu.cn; Wu, Hongchun; Zheng, Youqi; Cao, Liangzhi

    2015-01-15

    Highlights: • Economics analysis of fuel cycle cost of FFHRs is carried out. • The mass flows of different fuel cycle strategies are established based on the equilibrium fuel cycle model. • The levelized fuel cycle costs of different fuel cycle strategies are calculated, and compared with current once-through fuel cycle. - Abstract: The economics analysis of fuel cycle cost of fusion–fission hybrid reactors has been performed to compare four fuel cycle strategies: light water cooled blanket burning natural uranium (Strategy A) or spent nuclear fuel (Strategy B), sodium cooled blanket burning transuranics (Strategy C) or minor actinides (Strategy D). The levelized fuel cycle costs (LFCC) which does not include the capital cost, operation and maintenance cost have been calculated based on the equilibrium mass flows. The current once-through (OT) cycle strategy has also been analyzed to serve as the reference fuel cycle for comparisons. It is found that Strategy A and Strategy B have lower LFCCs than OT cycle; although the LFCC of Strategy C is higher than that of OT cycle when the uranium price is at its nominal value, it would become comparable to that of OT cycle when the uranium price reaches its historical peak value level; Strategy D shows the highest LFCC, because it needs to reprocess huge mass of spent nuclear fuel; LFCC is sensitive to the discharge burnup of the nuclear fuel.

  14. HTGR fuel and fuel cycle technology

    International Nuclear Information System (INIS)

    Lotts, A.L.; Coobs, J.H.

    1976-08-01

    The status of fuel and fuel cycle technology for high-temperature gas-cooled reactors (HTGRs) is reviewed. The all-ceramic core of the HTGRs permits high temperatures compared with other reactors. Core outlet temperatures of 740 0 C are now available for the steam cycle. For advanced HTGRs such as are required for direct-cycle power generation and for high-temperature process heat, coolant temperatures as high as 1000 0 C may be expected. The paper discusses the variations of HTGR fuel designs that meet the performance requirements and the requirements of the isotopes to be used in the fuel cycle. Also discussed are the fuel cycle possibilities, which include the low-enrichment cycle, the Th- 233 U cycle, and plutonium utilization in either cycle. The status of fuel and fuel cycle development is summarized

  15. Cell cycle phases in the unequal mother/daughter cell cycles of Saccharomyces cerevisiae.

    Science.gov (United States)

    Brewer, B J; Chlebowicz-Sledziewska, E; Fangman, W L

    1984-11-01

    During cell division in the yeast Saccharomyces cerevisiae mother cells produce buds (daughter cells) which are smaller and have longer cell cycles. We performed experiments to compare the lengths of cell cycle phases in mothers and daughters. As anticipated from earlier indirect observations, the longer cell cycle time of daughter cells is accounted for by a longer G1 interval. The S-phase and the G2-phase are of the same duration in mother and daughter cells. An analysis of five isogenic strains shows that cell cycle phase lengths are independent of cell ploidy and mating type.

  16. On acyclicity of games with cycles

    DEFF Research Database (Denmark)

    Andersson, Klas Olof Daniel; Hansen, Thomas Dueholm; Gurvich, Vladimir

    2010-01-01

    We study restricted improvement cycles (ri-cycles) in finite positional n-person games with perfect information modeled by directed graphs (di-graphs) that may contain directed cycles (di-cycles). We assume that all these di-cycles form one outcome c, for example, a draw. We obtain criteria...

  17. An integrated life cycle inventory for demolition processes in the context of life cycle sustainability assessment

    DEFF Research Database (Denmark)

    Bozhilova-Kisheva, Kossara Petrova; Hu, Mingming; van Roekel, Eric

    2012-01-01

    According to the Life Cycle Assessment in Building and Construction: State-of-the-Art Report (2003), the dismantling and demolition stage of the building life cycle is only sometimes included in the Life Cycle Inventory (LCI) when doing Life Cycle Assessments (LCA). The reason that it is less...... inventoried in a traditional LCA maybe because this stage is expected to have a negligible environmental impact comparing to other stages in the life cycle of the buildings. When doing a life cycle sustainability assessment considering not only environmental but also economic and social impacts, the impacts...

  18. A comparison of advanced heat recovery power cycles in a combined cycle for large ships

    DEFF Research Database (Denmark)

    Larsen, Ulrik; Sigthorsson, Oskar; Haglind, Fredrik

    2014-01-01

    Strong motivation exists within the marine sector to reduce fuel expenses and to comply with ever stricter emission regulations. Heat recovery can address both of these issues. The ORC (organic Rankine cycle), the Kalina cycle and the steam Rankine cycle have received the majority of the focus...... fluids possess high global warming potentials and hazard levels. It is concluded that the ORC has the greatest potential for increasing the fuel efficiency, and the combined cycle offers very high thermal efficiency. While being less efficient, the steam cycle has the advantages of being well proven...

  19. CANDU fuel-cycle vision

    International Nuclear Information System (INIS)

    Boczar, P.G.

    1999-01-01

    The fuel-cycle path chosen by a particular country will depend on a range of local and global factors. The CANDU reactor provides the fuel-cycle flexibility to enable any country to optimize its fuel-cycle strategy to suit its own needs. AECL has developed the CANFLEX fuel bundle as the near-term carrier of advanced fuel cycles. A demonstration irradiation of 24 CANFLEX bundles in the Point Lepreau power station, and a full-scale critical heat flux (CHF) test in water are planned in 1998, before commercial implementation of CANFLEX fuelling. CANFLEX fuel provides a reduction in peak linear element ratings, and a significant enhancement in thermalhydraulic performance. Whereas natural uranium fuel provides many advantages, the use of slightly enriched uranium (SEU) in CANDU reactors offers even lower fuel-cycle costs and other benefits, such as uprating capability through flattening the channel power distribution across the core. Recycled uranium (RU) from reprocessing spent PWR fuel is a subset of SEU that has significant economic promise. AECL views the use of SEU/RU in the CANFLEX bundle as the first logical step from natural uranium. High neutron economy enables the use of low-fissile fuel in CANDU reactors, which opens up a spectrum of unique fuel-cycle opportunities that exploit the synergism between CANDU reactors and LWRs. At one end of this spectrum is the use of materials from conventional reprocessing: CANDU reactors can utilize the RU directly without re-enrichment, the plutonium as conventional Mixed-oxide (MOX) fuel, and the actinide waste mixed with plutonium in an inert-matrix carrier. At the other end of the spectrum is the DUPIC cycle, employing only thermal-mechanical processes to convert spent LWR fuel into CANDU fuel, with no purposeful separation of isotopes from the fuel, and possessing a high degree of proliferation resistance. Between these two extremes are other advanced recycling options that offer particular advantages in exploiting the

  20. CANDU fuel-cycle vision

    International Nuclear Information System (INIS)

    Boczar, P.G

    1998-05-01

    The fuel-cycle path chosen by a particular country will depend on a range of local and global factors. The CANDU reactor provides the fuel-cycle flexibility to enable any country to optimize its fuel-cycle strategy to suit its own needs. AECL has developed the CANFLEX fuel bundle as the near-term carrier of advanced fuel cycles. A demonstration irradiation of 24 CANFLEX bundles in the Point Lepreau power station, and a full-scale critical heat flux (CHF) test in water are planned in 1998, before commercial implementation of CANFLEX fuelling. CANFLEX fuel provides a reduction in peak linear element ratings, and a significant enhancement in thermalhydraulic performance. Whereas natural uranium fuel provides many advantages, the use of slightly enriched uranium (SEU) in CANDU reactors offers even lower fuel-cycle costs and other benefits, such as uprating capability through flattening the channel power distribution across the core. Recycled uranium (RU) from reprocessing spent PWR fuel is a subset of SEU that has significant economic promise. AECL views the use of SEU/RU in the CANFLEX bundle as the first logical step from natural uranium. High neutron economy enables the use of low-fissile fuel in CANDU reactors, which opens up a spectrum of unique fuel-cycle opportunities that exploit the synergism between CANDU reactors and LWRs. At one end of this spectrum is the use of materials from conventional reprocessing: CANDU reactors can utilize the RU directly without reenrichment, the plutonium as conventional mixed-oxide (MOX) fuel, and the actinide waste mixed with plutonium in an inert-matrix carrier. At the other end of the spectrum is the DUPIC cycle, employing only thermal-mechanical processes to convert spent LWR fuel into CANDU fuel, with no purposeful separation of isotopes from the fuel, and possessing a high degree of proliferation resistance. Between these two extremes are other advanced recycling options that offer particular advantages in exploiting the

  1. Verifiable Fuel Cycle Simulation Model (VISION): A Tool for Analyzing Nuclear Fuel Cycle Futures

    International Nuclear Information System (INIS)

    Jacobson, Jacob J.; Piet, Steven J.; Matthern, Gretchen E.; Shropshire, David E.; Jeffers, Robert F.; Yacout, A.M.; Schweitzer, Tyler

    2010-01-01

    The nuclear fuel cycle consists of a set of complex components that are intended to work together. To support the nuclear renaissance, it is necessary to understand the impacts of changes and timing of events in any part of the fuel cycle system such as how the system would respond to each technological change, a series of which moves the fuel cycle from where it is to a postulated future state. The system analysis working group of the United States research program on advanced fuel cycles (formerly called the Advanced Fuel Cycle Initiative) is developing a dynamic simulation model, VISION, to capture the relationships, timing, and changes in and among the fuel cycle components to help develop an understanding of how the overall fuel cycle works. This paper is an overview of the philosophy and development strategy behind VISION. The paper includes some descriptions of the model components and some examples of how to use VISION. For example, VISION users can now change yearly the selection of separation or reactor technologies, the performance characteristics of those technologies, and/or the routing of material among separation and reactor types - with the model still operating on a PC in <5 min.

  2. Part 5. Fuel cycle options

    International Nuclear Information System (INIS)

    Lineberry, M.J.; McFarlane, H.F.; Amundson, P.I.; Goin, R.W.; Webster, D.S.

    1980-01-01

    The results of the FBR fuel cycle study that supported US contributions to the INFCE are presented. Fuel cycle technology is reviewed from both generic and historical standpoints. Technology requirements are developed within the framework of three deployment scenarios: the reference international, the secured area, and the integral cycle. Reprocessing, fabrication, waste handling, transportation, and safeguards are discussed for each deployment scenario. Fuel cycle modifications designed to increase proliferation defenses are described and assessed for effectiveness and technology feasibility. The present status of fuel cycle technology is reviewed and key issues that require resolution are identified

  3. Cell-cycle synchronisation of bloodstream forms of Trypanosoma brucei using Vybrant DyeCycle Violet-based sorting.

    Science.gov (United States)

    Kabani, Sarah; Waterfall, Martin; Matthews, Keith R

    2010-01-01

    Studies on the cell-cycle of Trypanosoma brucei have revealed several unusual characteristics that differ from the model eukaryotic organisms. However, the inability to isolate homogenous populations of parasites in distinct cell-cycle stages has limited the analysis of trypanosome cell division and complicated the understanding of mutant phenotypes with possible impact on cell-cycle related events. Although hydroxyurea-induced cell-cycle arrest in procyclic and bloodstream forms has been applied recently with success, such block-release protocols can complicate the analysis of cell-cycle regulated events and have the potential to disrupt important cell-cycle checkpoints. An alternative approach based on flow cytometry of parasites stained with Vybrant DyeCycle Orange circumvents this problem, but is restricted to procyclic form parasites. Here, we apply Vybrant Dyecycle Violet staining coupled with flow cytometry to effectively select different cell-cycle stages of bloodstream form trypanosomes. Moreover, the sorted parasites remain viable, although synchrony is rapidly lost. This method enables cell-cycle enrichment of populations of trypanosomes in their mammal infective stage, particularly at the G1 phase.

  4. Fast breeder fuel cycle

    International Nuclear Information System (INIS)

    1978-09-01

    Basic elements of the ex-reactor part of the fuel cycle (reprocessing, fabrication, waste handling and transportation) are described. Possible technical and proliferation measures are evaluated, including current methods of accountability, surveillance and protection. The reference oxide based cycle and advanced cycles based on carbide and metallic fuels are considered utilizing conventional processes; advanced nonaqueous reprocessing is also considered. This contribution provides a comprehensive data base for evaluation of proliferation risks

  5. Advanced fuel cycles: a rationale and strategy for adopting the low-enriched-uranium fuel cycle

    International Nuclear Information System (INIS)

    James, R.A.

    1980-01-01

    A two-year study of alternatives to the natural uranium fuel cycle in CANDU reactors is summarized. The possible advanced cycles are briefly described. Selection criteria for choosing a cycle for development include resource utilization, economics, ease of implementaton, and social acceptability. It is recommended that a detailed study should be made with a view to the early implementation of the low-enriched uranium cycle. (LL)

  6. Cell Cycle Control by PTEN.

    Science.gov (United States)

    Brandmaier, Andrew; Hou, Sheng-Qi; Shen, Wen H

    2017-07-21

    Continuous and error-free chromosome inheritance through the cell cycle is essential for genomic stability and tumor suppression. However, accumulation of aberrant genetic materials often causes the cell cycle to go awry, leading to malignant transformation. In response to genotoxic stress, cells employ diverse adaptive mechanisms to halt or exit the cell cycle temporarily or permanently. The intrinsic machinery of cycling, resting, and exiting shapes the cellular response to extrinsic stimuli, whereas prevalent disruption of the cell cycle machinery in tumor cells often confers resistance to anticancer therapy. Phosphatase and tensin homolog (PTEN) is a tumor suppressor and a guardian of the genome that is frequently mutated or deleted in human cancer. Moreover, it is increasingly evident that PTEN deficiency disrupts the fundamental processes of genetic transmission. Cells lacking PTEN exhibit cell cycle deregulation and cell fate reprogramming. Here, we review the role of PTEN in regulating the key processes in and out of cell cycle to optimize genomic integrity. Copyright © 2017 Elsevier Ltd. All rights reserved.

  7. Menstrual cycle pattern and fertility

    DEFF Research Database (Denmark)

    Kolstad, Henrik A.; Bonde, Jens Peter; Hjøllund, Niels Henrik

    1999-01-01

    OBJECTIVE: To characterize how the menstrual cycle pattern relates to fertility regardless of potential biases caused by inappropriate coital timing during the menstrual cycle or early embryonal loss. DESIGN: Prospective follow-up study. SETTING: Healthy couples recruited throughout Denmark....... PATIENT(S): Two hundred ninety-five couples who were planning their first pregnancy were followed up from the discontinuation of birth control until a pregnancy was recognized within six menstrual cycles. Early embryonal losses were detected by changes in urinary hCG levels. INTERVENTION(S): None. MAIN...... OUTCOME MEASURE(S): The probability of pregnancy occurring within one menstrual cycle (fecundity). RESULT(S): In women who had a cycle length that differed by >10 days from the usual cycle length, fecundity was approximately 25% that of women who had no variation (odds ratio 0.25, 95% confidence interval...

  8. National Policy on Nuclear Fuel Cycle

    International Nuclear Information System (INIS)

    Soedyartomo, S.

    1996-01-01

    National policy on nuclear fuel cycle is aimed at attaining the expected condition, i.e. being able to support optimality the national energy policy and other related Government policies taking into account current domestic nuclear fuel cycle condition and the trend of international nuclear fuel cycle development, the national strength, weakness, thread and opportunity in the field of energy. This policy has to be followed by the strategy to accomplish covering the optimization of domestic efforts, cooperation with other countries, and or purchasing licences. These policy and strategy have to be broken down into various nuclear fuel cycle programmes covering basically assesment of the whole cycle, performing research and development of the whole cycle without enrichment and reprocessing being able for weapon, as well as programmes for industrialization of the fuel cycle stepwisery commencing with the middle part of the cycle and ending with the edge of the back-end of the cycle

  9. Rock Cycle Roulette.

    Science.gov (United States)

    Schmidt, Stan M.; Palmer, Courtney

    2000-01-01

    Introduces an activity on the rock cycle. Sets 11 stages representing the transitions of an earth material in the rock cycle. Builds six-sided die for each station, and students move to the stations depending on the rolling side of the die. Evaluates students by discussing several questions in the classroom. Provides instructional information for…

  10. [Effects and mechanism of freeze-thawing cycles on key processes of nitrogen cycle in terrestrial ecosystem].

    Science.gov (United States)

    Wang, Li-qin; Qi, Yu-chun; Dong, Yun-she; Peng, Qin; Guo, Shu-fang; He, Yun-long; Yan, Zhong-qing

    2015-11-01

    As a widespread natural phenomenon in the soil of middle and high latitude as well as high altitude, freeze-thawing cycles have a great influence on the nitrogen cycle of terrestrial ecosystem in non-growing season. Freeze-thawing cycles can alter the physicochemical and biological properties of the soil, which thereby affect the migration and transformation of soil nitrogen. The impacts of freeze-thawing cycles on key processes of nitrogen cycle in terrestrial ecosystem found in available studies remain inconsistent, the mechanism is still not clear, and the research methods also need to be further explored and innovated. So it is necessary to sum up and analyze the existing achievements in order to better understand the processes of soil nitrogen cycle subjected to freeze-thawing cycles. This paper reviewed the research progress in China and abroad about the effects and mechanisms of freeze-thawing cycles on key processes of nitrogen cycle in terrestrial ecosystem, including mineralization, immobilization, nitrification and denitrification, N leakage and gaseous loss, and analyzed the deficiencies of extant research. The possible key research topics that should be urgently paid more attention to in the future were also discussed.

  11. Associations between Recreational and Commuter Cycling, Changes in Cycling, and Type 2 Diabetes Risk

    DEFF Research Database (Denmark)

    Rasmussen, Martin G; Grøntved, Anders; Blond, Kim

    2016-01-01

    BACKGROUND: Cycling is a recreational activity and mode of commuting with substantial potential to improve public health in many countries around the world. The aim of this study was to examine prospective associations between recreational and commuter cycling, changes in cycling habits, and risk.......83 (0.69, 1.00), and 0.70 (0.57, 0.85) (p for trend = 150 min/wk to work, respectively. The main limitation of the current study is the use of self-reported physical activity. CONCLUSIONS: Commuter and recreational cycling was consistently associated with lower...

  12. Transportation life cycle assessment (LCA) synthesis : life cycle assessment learning module series.

    Science.gov (United States)

    2015-03-12

    The Life Cycle Assessment Learning Module Series is a set of narrated, self-advancing slideshows on : various topics related to environmental life cycle assessment (LCA). This research project produced the first 27 of such modules, which : are freely...

  13. Large-scale fuel cycle centres

    International Nuclear Information System (INIS)

    Smiley, S.H.; Black, K.M.

    1977-01-01

    The US Nuclear Regulatory Commission (NRC) has considered the nuclear energy centre concept for fuel cycle plants in the Nuclear Energy Centre Site Survey 1975 (NECSS-75) Rep. No. NUREG-0001, an important study mandated by the US Congress in the Energy Reorganization Act of 1974 which created the NRC. For this study, the NRC defined fuel cycle centres as consisting of fuel reprocessing and mixed-oxide fuel fabrication plants, and optional high-level waste and transuranic waste management facilities. A range of fuel cycle centre sizes corresponded to the fuel throughput of power plants with a total capacity of 50,000-300,000MW(e). The types of fuel cycle facilities located at the fuel cycle centre permit the assessment of the role of fuel cycle centres in enhancing the safeguard of strategic special nuclear materials - plutonium and mixed oxides. Siting fuel cycle centres presents a smaller problem than siting reactors. A single reprocessing plant of the scale projected for use in the USA (1500-2000t/a) can reprocess fuel from reactors producing 50,000-65,000MW(e). Only two or three fuel cycle centres of the upper limit size considered in the NECSS-75 would be required in the USA by the year 2000. The NECSS-75 fuel cycle centre evaluation showed that large-scale fuel cycle centres present no real technical siting difficulties from a radiological effluent and safety standpoint. Some construction economies may be achievable with fuel cycle centres, which offer opportunities to improve waste-management systems. Combined centres consisting of reactors and fuel reprocessing and mixed-oxide fuel fabrication plants were also studied in the NECSS. Such centres can eliminate shipment not only of Pu but also mixed-oxide fuel. Increased fuel cycle costs result from implementation of combined centres unless the fuel reprocessing plants are commercial-sized. Development of Pu-burning reactors could reduce any economic penalties of combined centres. The need for effective fissile

  14. Economic comparison of fusion fuel cycles

    International Nuclear Information System (INIS)

    Brereton, S.J.; Kazimi, M.S.

    1987-01-01

    The economics of the DT, DD, and DHe fusion fuel cycles are evaluated by comparison on a consistent basis. The designs for the comparison employ HT-9 structure and helium coolant; liquid lithium is used as the tritium breeding material for the DT fuel cycle. The reactors are pulsed, superconducting tokamaks, producing 1200 MW of electric power. The DT and DD designs scan a range of values of plasma beta, assuming first stability scaling laws. The results indicate that on a purely economic basis, the DT fuel cycle is superior to both of the advanced fuel cycles. Geometric factors, materials limitations, and plasma beta were seen to have an impact on the Cost of Electricity (COE). The economics for the DD fuel cycle are more strongly affected by these parameters than is the DT fuel cycle. Fuel costs are a major factor in determining the COE for the DHe fuel cycle. Based on costs directly attributable to the fuel cycle, the DT fuel cycle appears most attractive. Technological advances, improved understanding of physics, or strides in advanced energy conversion schemes may result in altering the economic ranking of the fuel cycles indicated here. 7 refs., 6 figs., 2 tabs

  15. Cycle layout studies of S-CO2 cycle for the next generation nuclear system application

    International Nuclear Information System (INIS)

    Ahn, Yoonhan; Bae, Seong Jun; Kim, Minseok; Cho, Seong Kuk; Baik, Seungjoon; Lee, Jeong Ik; Cha, Jae Eun

    2014-01-01

    According to the second law of thermodynamics, the next generation nuclear reactor system efficiency can potentially be increased with higher operating temperature. Fig.1 shows several power conversion system efficiencies and heat sources with respect to the system top operating temperature. As shown in Fig.1, the steam Rankine and gas Brayton cycles have been considered as the major power conversion systems more than several decades. In the next generation reactor operating temperature region (450 - 900 .deg. C), the steam Rankine and gas Brayton cycles have limits due to material problems and low efficiency, respectively. Among the future power conversion systems, S-CO 2 cycle is receiving interests due to several benefits including high efficiency under the mild turbine inlet temperature range (450-650 .deg. C), compact turbomachinery and simple layout compared to the steam Rankine cycle. S-CO 2 cycle can show relatively high efficiency under the mild turbine inlet temperature range (450-600 .deg. C) compared to other power conversion systems. The recompression cycle shows the best efficiency among other layouts and it is suitable for the application to advanced nuclear reactor systems. As S-CO 2 cycle performance can vary depending on the layout configuration, further studies on the layouts are required to design a better performing cycle

  16. The Life Cycle of Centrioles

    OpenAIRE

    Hatch, E.; Stearns, T.

    2010-01-01

    Centrioles organize the centrosome and nucleate the ciliary axoneme, and the centriole life cycle has many parallels to the chromosome cycle. The centriole cycle in animals begins at fertilization with the contribution of two centrioles by the male gamete. In the ensuing cell cycles, the duplication of centrioles is controlled temporally, spatially, and numerically. As a consequence of the duplication mechanism, the two centrioles in a typical interphase cell are of different ages and have di...

  17. Gas fired combined cycle plant in Singapore: energy use, GWP and cost-a life cycle approach

    International Nuclear Information System (INIS)

    Kannan, R.; Leong, K.C.; Osman, Ramli; Ho, H.K.; Tso, C.P.

    2005-01-01

    A life cycle assessment was performed to quantify the non-renewable (fossil) energy use and global warming potential (GWP) in electricity generation from a typical gas fired combined cycle power plant in Singapore. The cost of electricity generation was estimated using a life cycle cost analysis (LCCA) tool. The life cycle assessment (LCA) of a 367.5 MW gas fired combined cycle power plant operating in Singapore revealed that hidden processes consume about 8% additional energy in addition to the fuel embedded energy, and the hidden GWP is about 18%. The natural gas consumed during the operational phase accounted for 82% of the life cycle cost of electricity generation. An empirical relation between plant efficiency and life cycle energy use and GWP in addition to a scenario for electricity cost with varying gas prices and plant efficiency have been established

  18. In anticipation of cycle 24

    Science.gov (United States)

    Kunches, Joseph; van der Linden, Ronald; Lundstedt, Henrik

    Anxious eyes are watching for the beginnings of new solar cycle 24. The watchers are many; scientists, engineers, academics, forecasters, end users. Their needs however vary, from the attraction of a better understanding of our nearest star, to how its increase in luminosity will affect particular aspects such as satellite orbits or the strength of the episodic storms that are most likely to occur during the height of the cycle. The first sign, however fleeting, occurred in January, 2008, when an ephemeral new cycle spot was numbered by NOAA as 10981. It was gone quickly but did mark the possible beginning of the new cycle. There has been great debate among solar physicists on how strong cycle 24 will be; and when it will start, reach maximum, and decline. This talk will give the status of the efforts to predict cycle 24, and the most recent projections.

  19. The economics of thorium fuel cycles

    International Nuclear Information System (INIS)

    James, R.A.

    1978-01-01

    The individual cost components and the total fuel cycle costs for natural uranium and thorium fuel cycles are discussed. The thorium cycles are initiated by using either enriched uranium or plutonium. Subsequent thorium cycles utilize recycled uranium-233 and, where necessary, either uranium-235 or plutonium as topping. A calculation is performed to establish the economic conditions under which thorium cycles are economically attractive. (auth)

  20. Active cooling for downhole instrumentation: Preliminary analysis and system selection

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, G.A.

    1988-03-01

    A feasibility study and a series of preliminary designs and analyses were done to identify candidate processes or cycles for use in active cooling systems for downhole electronic instruments. A matrix of energy types and their possible combinations was developed and the energy conversion process for each pari was identified. The feasibility study revealed conventional as well as unconventional processes and possible refrigerants and identified parameters needing further clarifications. A conceptual design or series od oesigns for each system was formulated and a preliminary analysis of each design was completed. The resulting coefficient of performance for each system was compared with the Carnot COP and all systems were ranked by decreasing COP. The system showing the best combination of COP, exchangeability to other operating conditions, failure mode, and system serviceability is chosen for use as a downhole refrigerator. 85 refs., 48 figs., 33 tabs.

  1. Thermodynamics and heat power

    CERN Document Server

    Granet, Irving

    2014-01-01

    Fundamental ConceptsIntroductionThermodynamic SystemsTemperatureForce and MassElementary Kinetic Theory of GasesPressureReviewKey TermsEquations Developed in This ChapterQuestionsProblemsWork, Energy, and HeatIntroductionWorkEnergyInternal EnergyPotential EnergyKinetic EnergyHeatFlow WorkNonflow WorkReviewKey TermsEquations Developed in This ChapterQuestionsProblemsFirst Law of ThermodynamicsIntroductionFirst Law of ThermodynamicsNonflow SystemSteady-Flow SystemApplications of First Law of ThermodynamicsReviewKey TermsEquations Developed in This ChapterQuestionsProblemsThe Second Law of ThermodynamicsIntroductionReversibility-Second Law of ThermodynamicsThe Carnot CycleEntropyReviewKey TermsEquations Developed in This ChapterQuestionsProblemsProperties of Liquids and GasesIntroductionLiquids and VaporsThermodynamic Properties of SteamComputerized PropertiesThermodynamic DiagramsProcessesReviewKey TermsEquations Developed in This ChapterQuestionsProblemsThe Ideal GasIntroductionBasic ConsiderationsSpecific Hea...

  2. Limit cycles in quantum systems

    Energy Technology Data Exchange (ETDEWEB)

    Niemann, Patrick

    2015-04-27

    In this thesis we investigate Limit Cycles in Quantum Systems. Limit cycles are a renormalization group (RG) topology. When degrees of freedom are integrated out, the coupling constants flow periodically in a closed curve. The presence of limit cycles is restricted by the necessary condition of discrete scale invariance. A signature of discrete scale invariance and limit cycles is log-periodic behavior. The first part of this thesis is concerned with the study of limit cycles with the similarity renormalization group (SRG). Limit cycles are mainly investigated within conventional renormalization group frameworks, where degrees of freedom, which are larger than a given cutoff, are integrated out. In contrast, in the SRG potentials are unitarily transformed and thereby obtain a band-diagonal structure. The width of the band structure can be regarded as an effective cutoff. We investigate the appearance of limit cycles in the SRG evolution. Our aim is to extract signatures as well as the scaling factor of the limit cycle. We consider the 1/R{sup 2}-potential in a two-body system and a three-body system with large scattering lengths. Both systems display a limit cycle. Besides the frequently used kinetic energy generator we apply the exponential and the inverse generator. In the second part of this thesis, Limit Cycles at Finite Density, we examine the pole structure of the scattering amplitude for distinguishable fermions at zero temperature in the medium. Unequal masses and a filled Fermi sphere for each fermion species are considered. We focus on negative scattering lengths and the unitary limit. The properties of the three-body spectrum in the medium and implications for the phase structure of ultracold Fermi gases are discussed.

  3. The nuclear fuel cycle versus the carbon cycle

    International Nuclear Information System (INIS)

    Ewing, R.C.

    2005-01-01

    Nuclear power provides approximately 17% of the world's electricity, which is equivalent to a reduction in carbon emissions of ∼0.5 gigatonnes (Gt) of C/yr. This is a modest reduction as compared with global emissions of carbon, ∼7 Gt C/yr. Most analyses suggest that in order to have a significant and timely impact on carbon emissions, carbon-free sources, such as nuclear power, would have to expand total production of energy by factors of three to ten by 2050. A three-fold increase in nuclear power capacity would result in a projected reduction in carbon emissions of 1 to 2 Gt C/yr, depending on the type of carbon-based energy source that is displaced. This three-fold increase utilizing present nuclear technologies would result in 25,000 metric tonnes (t) of spent nuclear fuel (SNF) per year, containing over 200 t of plutonium. This is compared to a present global inventory of approximately 280,000 t of SNF and >1,700 t of Pu. A nuclear weapon can be fashioned from as little as 5 kg of 239 Pu. However, there is considerable technological flexibility in the nuclear fuel cycle. There are three types of nuclear fuel cycles that might be utilized for the increased production of energy: open, closed, or a symbiotic combination of different types of reactor (such as, thermal and fast neutron reactors). The neutron energy spectrum has a significant effect on the fission product yield, and the consumption of long-lived actinides, by fission, is best achieved by fast neutrons. Within each cycle, the volume and composition of the high-level nuclear waste and fissile material depend on the type of nuclear fuel, the amount of burn-up, the extent of radionuclide separation during reprocessing, and the types of materials used to immobilize different radionuclides. As an example, a 232 Th-based fuel cycle can be used to breed fissile 233 U with minimum production of Pu. In this paper, I will contrast the production of excess carbon in the form of CO 2 from fossil fuels with

  4. Measuring Business Cycle Time.

    OpenAIRE

    Stock, James H

    1987-01-01

    The business cycle analysis of Arthur F. Burns and Wesley C. Mitchell and the National Bureau of Economic Research presumed that aggregate economic variables evolve on a time scale defined by business cycle turning points rather than by months or quarters. Do macroeconomic variables appear to evolve on an economic rather than a calendar time scale? Evidence presented here suggests that they do. However, the estimated economic time scales are only weakly related to business cycle time scales, ...

  5. Power generation from a 7700C heat source by means of a main steam cycle, a topping closed gas cycle and a ammonia bottoming cycle

    International Nuclear Information System (INIS)

    Tilliette, Z.P.

    1981-03-01

    For power generation, steam cycles make an efficient use of medium temperature heat sources. They can be adapted to dry cooling, higher power ratings and output increase in winter by addition of an ammonia bottoming cycle. Active development is carried out in this field by 'Electricite de France'. As far as heat sources at higher temperatures are concerned, particularly related to coal-fired or nuclear power plants, a more efficient way of converting energy is at first to expand a hot working fluid through a gas turbine. It is shown in this paper that a satisfactory result, for heat sources of about 770 0 C, is obtained with a topping closed gas cycle of moderate power rating, rejecting its waste heat into the main steam cycle. Attention has to be paid to this gas cycle waste heat recovery and to the coupling of the gas and steam cycles. This concept drastically reduces the importance of new technology components. The use and the significance of an ammonia bottoming cycle in this case are investigated

  6. Multi-d CFD Modeling of a Free-piston Stirling Convertor at NASA Glenn

    Science.gov (United States)

    Wilson, Scott D.; Dyson, Rodger W.; Tew, Roy C.; Ibrahim, Mounir B.

    2004-01-01

    A high efficiency Stirling Radioisotope Generator (SRG) is being developed for possible use in long duration space science missions. NASA s advanced technology goals for next generation Stirling convertors include increasing the Carnot efficiency and percent of Carnot efficiency. To help achieve these goals, a multidimensional Computational Fluid Dynamics (CFD) code is being developed to numerically model unsteady fluid flow and heat transfer phenomena of the oscillating working gas inside Stirling convertors. Simulations of the Stirling convertors for the SRG will help characterize the thermodynamic losses resulting from fluid flow and heat transfer between the working gas and solid walls. The current CFD simulation represents approximated 2-dimensional convertor geometry. The simulation solves the Navier Stokes equations for an ideal helium gas oscillating at low speeds. The current simulation results are discussed.

  7. Entrepreneurship and the Business Cycle

    NARCIS (Netherlands)

    Ph.D. Koellinger (Philipp); A.R. Thurik (Roy)

    2011-01-01

    textabstractWe find new empirical regularities in the business cycle in a cross-country panel of 22 OECD countries for the period 1972-2007; entrepreneurship Granger-causes the cycles of the world economy. Furthermore, the entrepreneurial cycle is positively affected by the national unemployment

  8. Quadratic reactivity fuel cycle model

    International Nuclear Information System (INIS)

    Lewins, J.D.

    1985-01-01

    For educational purposes it is highly desirable to provide simple yet realistic models for fuel cycle and fuel economy. In particular, a lumped model without recourse to detailed spatial calculations would be very helpful in providing the student with a proper understanding of the purposes of fuel cycle calculations. A teaching model for fuel cycle studies based on a lumped model assuming the summability of partial reactivities with a linear dependence of reactivity usefully illustrates fuel utilization concepts. The linear burnup model does not satisfactorily represent natural enrichment reactors. A better model, showing the trend of initial plutonium production before subsequent fuel burnup and fission product generation, is a quadratic fit. The study of M-batch cycles, reloading 1/Mth of the core at end of cycle, is now complicated by nonlinear equations. A complete account of the asymptotic cycle for any order of M-batch refueling can be given and compared with the linear model. A complete account of the transient cycle can be obtained readily in the two-batch model and this exact solution would be useful in verifying numerical marching models. It is convenient to treat the parabolic fit rho = 1 - tau 2 as a special case of the general quadratic fit rho = 1 - C/sub tau/ - (1 - C)tau 2 in suitably normalized reactivity and cycle time units. The parabolic results are given in this paper

  9. Historicising the Hydrosocial Cycle

    Directory of Open Access Journals (Sweden)

    Jeremy J. Schmidt

    2014-02-01

    Full Text Available This paper examines the historical claims made in support of the hydrosocial cycle. In particular, it considers how arguments advancing the hydrosocial cycle make historical claims regarding modernist conceptions of what water is (i.e. H2O and its fit with society. The paper gives special emphasis to the society/nature dualism and to the notion of agency as key sites of contest in arguments regarding the hydrosocial cycle. It finds that, while several versions of the hydrosocial cycle seek to advance a political ecology more sensitive to non-human actions, these same accounts often do not address the robust account of non-human agency in the historical record. Evidence is presented regarding water’s agency amongst late 19th and early 20th century architects of key water management norms in the United States. This evidence troubles accounts of the hydrosocial cycle that critique the US experience and suggests new directions for rethinking the role of historical and institutional norms in water policy.

  10. Combined rankine and vapor compression cycles

    Science.gov (United States)

    Radcliff, Thomas D.; Biederman, Bruce P.; Brasz, Joost J.

    2005-04-19

    An organic rankine cycle system is combined with a vapor compression cycle system with the turbine generator of the organic rankine cycle generating the power necessary to operate the motor of the refrigerant compressor. The vapor compression cycle is applied with its evaporator cooling the inlet air into a gas turbine, and the organic rankine cycle is applied to receive heat from a gas turbine exhaust to heat its boiler within one embodiment, a common condenser is used for the organic rankine cycle and the vapor compression cycle, with a common refrigerant, R-245a being circulated within both systems. In another embodiment, the turbine driven generator has a common shaft connected to the compressor to thereby eliminate the need for a separate motor to drive the compressor. In another embodiment, an organic rankine cycle system is applied to an internal combustion engine to cool the fluids thereof, and the turbo charged air is cooled first by the organic rankine cycle system and then by an air conditioner prior to passing into the intake of the engine.

  11. Life cycle assessment (LCA)

    DEFF Research Database (Denmark)

    Thrane, Mikkel; Schmidt, Jannick Andresen

    2004-01-01

    The chapter introduces Life Cycle Assessment (LCA) and its application according to the ISO 1404043 standards.......The chapter introduces Life Cycle Assessment (LCA) and its application according to the ISO 1404043 standards....

  12. Cycling biomechanics: a literature review.

    Science.gov (United States)

    Wozniak Timmer, C A

    1991-01-01

    Submitted in partial fulfillment for a Master of Science degree at the University of Pittsburgh, School of Health Related Professions, Pittsburgh, PA 1.5213 This review of current literature on cycling biomechanics emphasizes lower extremity muscle actions and joint excursions, seat height, pedal position, pedaling rate, force application, and pedaling symmetry. Guidelines are discussed for optimal seat height, pedal position, and pedaling rate. Force application in the power and recovery phases of cycling and the relationship of force application to pedaling symmetry are discussed. The need for a biomechanical approach to cycling exists since a great deal of the literature is primarily physiologic in nature. The purpose of this review is to make cyclists and their advisors aware of the biomechanics of cycling and guidelines to follow. This approach is also important because cycling is a very common form of exercise prescribed by physical therapists for clinic or home programs. Biomechanical aspects of cycling should be considered by cyclists at any level of participation and by physical therapists in order for goal-oriented, efficient cycling to occur. J Orthop Sports Phys Ther 1991;14(3):106-113.

  13. Thorium fuel cycle analysis

    Energy Technology Data Exchange (ETDEWEB)

    Yamaji, K [Central Research Inst. of Electric Power Industry, Tokyo (Japan)

    1980-07-01

    Systems analysis of the thorium cycle, a nuclear fuel cycle accomplished by using thorium, is reported in this paper. Following a brief review on the history of the thorium cycle development, analysis is made on the three functions of the thorium cycle; (1) auxiliary system of U-Pu cycle to save uranium consumption, (2) thermal breeder system to exert full capacity of the thorium resource, (3) symbiotic system to utilize special features of /sup 233/U and neutron sources. The effects of the thorium loading in LWR (Light Water Reactor), HWR (Heavy Water Reactor) and HTGR (High Temperature Gas-cooled Reactor) are considered for the function of auxiliary system of U-Pu cycle. Analysis is made to find how much uranium is saved by /sup 233/U recycling and how the decrease in Pu production influences the introduction of FBR (Fast Breeder Reactor). Study on thermal breeder system is carried out in the case of MSBR (Molten Salt Breeder Reactor). Under a certain amount of fissile material supply, the potential system expansion rate of MSBR, which is determined by fissile material balance, is superior to that of FBR because of the smaller specific fissile inventory of MSBR. For symbiotic system, three cases are treated; i) nuclear heat supply system using HTGR, ii) denatured fuel supply system for nonproliferation purpose, and iii) hybrid system utilizing neutron sources other than fission reactor.

  14. International Business Cycle Accounting

    OpenAIRE

    Keisuke Otsu

    2009-01-01

    In this paper, I extend the business cycle accounting method a la Chari, Kehoe and McGrattan (2007) to a two-country international business cycle model and quantify the effect of the disturbances in relevant markets on the business cycle correlation between Japan and the US over the 1980-2008 period. This paper finds that disturbances in the labor market and production efficiency are important in accounting for the recent increase in the cross-country output correlation. If international fina...

  15. Optimal Life Cycle Portfolio Choice with Housing Market Cycles

    DEFF Research Database (Denmark)

    Fischer, Marcel; Stamos, Michael Z.

    2013-01-01

    income, and pre-existing housing wealth but also the state of the housing market significantly affect household decisions. Consistently with the data, the model predicts that in good states of housing market cycles (1) homeownership rates increase, (2) households buying homes invest a larger share......In recent decades U.S. households have experienced residential house prices moving persistently, that is, returns being positively serially correlated. We set up a realistically calibrated life cycle model with slow-moving time variation in expected housing returns, showing that not only age, labor...

  16. Large-scale fuel cycle centers

    International Nuclear Information System (INIS)

    Smiley, S.H.; Black, K.M.

    1977-01-01

    The United States Nuclear Regulatory Commission (NRC) has considered the nuclear energy center concept for fuel cycle plants in the Nuclear Energy Center Site Survey - 1975 (NECSS-75) -- an important study mandated by the U.S. Congress in the Energy Reorganization Act of 1974 which created the NRC. For the study, NRC defined fuel cycle centers to consist of fuel reprocessing and mixed oxide fuel fabrication plants, and optional high-level waste and transuranic waste management facilities. A range of fuel cycle center sizes corresponded to the fuel throughput of power plants with a total capacity of 50,000 - 300,000 MWe. The types of fuel cycle facilities located at the fuel cycle center permit the assessment of the role of fuel cycle centers in enhancing safeguarding of strategic special nuclear materials -- plutonium and mixed oxides. Siting of fuel cycle centers presents a considerably smaller problem than the siting of reactors. A single reprocessing plant of the scale projected for use in the United States (1500-2000 MT/yr) can reprocess the fuel from reactors producing 50,000-65,000 MWe. Only two or three fuel cycle centers of the upper limit size considered in the NECSS-75 would be required in the United States by the year 2000 . The NECSS-75 fuel cycle center evaluations showed that large scale fuel cycle centers present no real technical difficulties in siting from a radiological effluent and safety standpoint. Some construction economies may be attainable with fuel cycle centers; such centers offer opportunities for improved waste management systems. Combined centers consisting of reactors and fuel reprocessing and mixed oxide fuel fabrication plants were also studied in the NECSS. Such centers can eliminate not only shipment of plutonium, but also mixed oxide fuel. Increased fuel cycle costs result from implementation of combined centers unless the fuel reprocessing plants are commercial-sized. Development of plutonium-burning reactors could reduce any

  17. Fuel cycle optimization in PWR'S

    International Nuclear Information System (INIS)

    Castro Lobo, P.D. de; Amorim, E.S. do.

    1979-08-01

    Neutronics aspects of a reactor core throughout its cycle were investigated in a search for increasing in-core utilization of the residual fissile isotopes content in the cycle discharged disposal. The effects due to design modifications introduced at burnup levels near the end-of-cycle, in an equilibrium cycle condition, have indicated the possibility of a better in-core utilization of the residual fissile isotopes existing in the cycle discharged disposal. The potential benefits are significant to warranty an examination of the mechanical and thermal hydraulic involved. At convenient burnup levels, change in H 2 O/UO 2 volume ratio were introduced allowing an intense depletion of the residual fissile isotopes existing in assemblies with high exposures levels. (Author) [pt

  18. Gender differences in recreational and transport cycling: a cross-sectional mixed-methods comparison of cycling patterns, motivators, and constraints.

    Science.gov (United States)

    Heesch, Kristiann C; Sahlqvist, Shannon; Garrard, Jan

    2012-09-08

    Gender differences in cycling are well-documented. However, most analyses of gender differences make broad comparisons, with few studies modeling male and female cycling patterns separately for recreational and transport cycling. This modeling is important, in order to improve our efforts to promote cycling to women and men in countries like Australia with low rates of transport cycling. The main aim of this study was to examine gender differences in cycling patterns and in motivators and constraints to cycling, separately for recreational and transport cycling. Adult members of a Queensland, Australia, community bicycling organization completed an online survey about their cycling patterns; cycling purposes; and personal, social and perceived environmental motivators and constraints (47% response rate). Closed and open-end questions were completed. Using the quantitative data, multivariable linear, logistic and ordinal regression models were used to examine associations between gender and cycling patterns, motivators and constraints. The qualitative data were thematically analyzed to expand upon the quantitative findings. In this sample of 1862 bicyclists, men were more likely than women to cycle for recreation and for transport, and they cycled for longer. Most transport cycling was for commuting, with men more likely than women to commute by bicycle. Men were more likely to cycle on-road, and women off-road. However, most men and women did not prefer to cycle on-road without designed bicycle lanes, and qualitative data indicated a strong preference by men and women for bicycle-only off-road paths. Both genders reported personal factors (health and enjoyment related) as motivators for cycling, although women were more likely to agree that other personal, social and environmental factors were also motivating. The main constraints for both genders and both cycling purposes were perceived environmental factors related to traffic conditions, motorist aggression and

  19. Cycle-by-cycle variations in a spark ignition engine fueled with natural gas-hydrogen blends combined with EGR

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Bin; Hu, Erjiang; Huang, Zuohua; Zheng, Jianjun; Liu, Bing; Jiang, Deming [State Key Laboratory of Multiphase Flow in Power Engineering, Xi' an Jiaotong University, 710049 Xi' an (China)

    2009-10-15

    Study of cycle-by-cycle variations in a spark ignition engine fueled with natural gas-hydrogen blends combined with exhaust gas recirculation (EGR) was conducted. The effects of EGR ratio and hydrogen fraction on engine cycle-by-cycle variations are analyzed. The results show that the cylinder peak pressure, the maximum rate of pressure rise and the indicated mean effective pressure decrease and cycle-by-cycle variations increase with the increase of EGR ratio. Interdependency between the above parameters and their corresponding crank angles of cylinder peak pressure is decreased with the increase of EGR ratio. For a given EGR ratio, combustion stability is promoted and cycle-by-cycle variations are decreased with the increase of hydrogen fraction in the fuel blends. Non-linear relationship is presented between the indicated mean effective pressure and EGR ratio. Slight influence of EGR ratio on indicated mean effective pressure is observed at low EGR ratios while large influence of EGR ratio on indicated mean effective pressure is demonstrated at high EGR ratios. The high test engine speed has lower cycle-by-cycle variations due to the enhancement of air flow turbulence and swirls in the cylinder. Increasing hydrogen fraction can maintain low cycle-by-cycle variations at high EGR ratios. (author)

  20. Interventions to promote cycling: systematic review.

    Science.gov (United States)

    Yang, Lin; Sahlqvist, Shannon; McMinn, Alison; Griffin, Simon J; Ogilvie, David

    2010-10-18

    To determine what interventions are effective in promoting cycling, the size of the effects of interventions, and evidence of any associated benefits on overall physical activity or anthropometric measures. Systematic review. Published and unpublished reports in any language identified by searching 13 electronic databases, websites, reference lists, and existing systematic reviews, and papers identified by experts in the field. Review methods Controlled "before and after" experimental or observational studies of the effect of any type of intervention on cycling behaviour measured at either individual or population level. Twenty five studies (of which two were randomised controlled trials) from seven countries were included. Six studies examined interventions aimed specifically at promoting cycling, of which four (an intensive individual intervention in obese women, high quality improvements to a cycle route network, and two multifaceted cycle promotion initiatives at town or city level) were found to be associated with increases in cycling. Those studies that evaluated interventions at population level reported net increases of up to 3.4 percentage points in the population prevalence of cycling or the proportion of trips made by bicycle. Sixteen studies assessing individualised marketing of "environmentally friendly" modes of transport to interested households reported modest but consistent net effects equating to an average of eight additional cycling trips per person per year in the local population. Other interventions that targeted travel behaviour in general were not associated with a clear increase in cycling. Only two studies assessed effects of interventions on physical activity; one reported a positive shift in the population distribution of overall physical activity during the intervention. Community-wide promotional activities and improving infrastructure for cycling have the potential to increase cycling by modest amounts, but further controlled

  1. Effect of irreversible processes on the thermodynamic performance of open-cycle desiccant cooling cycles

    International Nuclear Information System (INIS)

    La, Dong; Li, Yong; Dai, Yanjun; Ge, Tianshu; Wang, Ruzhu

    2013-01-01

    Highlights: ► Effects of irreversible processes on the performance of desiccant cooling cycle are identified. ► The exergy destructions involved are classified by the properties of the individual processes. ► Appropriate indexes for thermodynamic evaluation are proposed based on thermodynamic analyses. - Abstract: Thermodynamic analyses of desiccant cooling cycle usually focus on the overall cycle performance in previous study. In this paper, the effects of the individual irreversible processes in each component on thermodynamic performance are analyzed in detail. The objective of this paper is to reveal the elemental features of the individual components, and to show their effects on the thermodynamic performance of the whole cycle in a fundamental way. Appropriate indexes for thermodynamic evaluation are derived based on the first and second law analyses. A generalized model independent of the connection of components is developed. The results indicate that as the effectiveness of the desiccant wheel increases, the cycle performance is increased principally due to the significant reduction in exergy carried out by exhaust air. The corresponding exergy destruction coefficient of the cycle with moderate performance desiccant wheel is decreased greatly to 3.9%, which is more than 50% lower than that of the cycle with low performance desiccant wheel. The effect of the heat source is similar. As the temperature of the heat source increases from 60 °C to 90 °C, the percentage of exergy destruction raised by exhaust air increases sharply from 5.3% to 21.8%. High heat exchanger effectiveness improves the cycle performance mainly by lowering the irreversibility of the heat exchanger, using less regeneration heat and pre-cooling the process air effectively

  2. Life Cycle Sustainability Dashboard

    DEFF Research Database (Denmark)

    Traverso, Marzia; Finkbeiner, Matthias; Jørgensen, Andreas

    2012-01-01

    One method to assess the sustainability performance of products is life cycle sustainability assessment (LCSA), which assesses product performance considering the environmental,economic, and social dimensions of the life cycle. The results of LCSA can be used to compare different products...... of sustainability is the communicability of the results by means of a graphical representation (a cartogram), characterized by a suitable chromatic scale and ranking score. The integration of LCSA and the dashboard of sustainability into a so-called Life Cycle Sustainability Dashboard (LCSD) is described here...

  3. Assessing the impact of road traffic on cycling for leisure and cycling to work

    Directory of Open Access Journals (Sweden)

    Wareham Nicholas J

    2011-06-01

    Full Text Available Abstract Background To explore the relationship between leisure and commuter cycling with objectively measured levels of road traffic and whether any relationship was affected by traffic levels directly outside of home or in local neighbourhood. Findings We conducted a secondary analysis of data from the UK European Prospective Investigation of Cancer (EPIC Norfolk cohort in 2009. We used a geographical information system (GIS and gender specific multivariate models to relate 13 927 participants' reported levels of cycling with an index of road traffic volume (Road Traffic Volume Index Score - RTVIS. RTVIS were calculated around each participants home, using four distance based buffers, (0.5 km, 1 km, 2 km and 3.2 km. Models were adjusted for age, social status, education, car access and deprivation. Both genders had similar decreases in leisure cycling as traffic volumes increased at greater distances from home (OR 0.42, (95% CI 0.32-0.52, p Conclusions Traffic volumes appear to have greater impact on leisure cycling than commuter cycling. Future research should investigate the importance of traffic on different types of cycling and include psychosocial correlates.

  4. Frozen-Thawed Embryo Transfer Cycles Have a Lower Incidence of Ectopic Pregnancy Compared With Fresh Embryo Transfer Cycles.

    Science.gov (United States)

    Zhang, Xinyu; Ma, Caihong; Wu, Zhangxin; Tao, Liyuan; Li, Rong; Liu, Ping; Qiao, Jie

    2017-01-01

    To evaluate the risk of ectopic pregnancy of embryo transfer. A retrospective cohort study on the incidence of ectopic pregnancy in fresh and frozen-thawed embryo transfer cycles from January 1 st , 2010, to January 1 st , 2015. Infertile women undergoing frozen-thawed transfer cycles or fresh transfer cycles. In-vitro fertilization, fresh embryo transfer, frozen-thawed embryo transfer, ectopic pregnancy. Ectopic pregnancy rate and clinical pregnancy rate. A total of 69 756 in vitro fertilization-embryo transfer cycles from 2010 to 2015 were analyzed, including 45 960 (65.9%) fresh and 23 796 (34.1%) frozen-thawed embryo transfer cycles. The clinical pregnancy rate per embryo transfer was slightly lower in fresh embryo transfer cycles compared with frozen-thawed embryo transfer cycles (40.8% vs 43.1%, P cycles, blastocyst transfer shows a significantly lower incidence of ectopic pregnancy (0.8% vs 1.8%, P = .002) in comparison with day 3 cleavage embryo transfer. The risk of ectopic pregnancy is lower in frozen-thawed embryo transfer cycles than fresh embryo transfer cycles, and blastocyst transfer could further decrease the ectopic pregnancy rate in frozen-thawed embryo transfer cycles.

  5. Research on Correlation between Vehicle Cycle and Engine Cycle in Heavy-duty commercial vehicle

    Science.gov (United States)

    lin, Chen; Zhong, Wang; Shuai, Liu

    2017-12-01

    In order to study the correlation between vehicle cycle and engine cycle in heavy commercial vehicles, the conversion model of vehicle cycle to engine cycle is constructed based on the vehicle power system theory and shift strategy, which considers the verification on diesel truck. The results show that the model has high rationality and reliability in engine operation. In the acceleration process of high speed, the difference of model gear selection leads to the actual deviation. Compared with the drum test, the engine speed distribution obtained by the model deviates to right, which fits to the lower grade. The grade selection has high influence on the model.

  6. Thorium fuel cycle management

    International Nuclear Information System (INIS)

    Zajac, R.; Darilek, P.; Breza, J.; Necas, V.

    2010-01-01

    In this presentation author deals with the thorium fuel cycle management. Description of the thorium fuels and thorium fuel cycle benefits and challenges as well as thorium fuel calculations performed by the computer code HELIOS are presented.

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

    Directory of Open Access Journals (Sweden)

    Lingen Chen

    2012-01-01

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

  8. Nitrogen Cycle Evaluation (NiCE) Chip for the Simultaneous Analysis of Multiple N-Cycle Associated Genes.

    Science.gov (United States)

    Oshiki, Mamoru; Segawa, Takahiro; Ishii, Satoshi

    2018-02-02

    Various microorganisms play key roles in the Nitrogen (N) cycle. Quantitative PCR (qPCR) and PCR-amplicon sequencing of the N cycle functional genes allow us to analyze the abundance and diversity of microbes responsible in the N transforming reactions in various environmental samples. However, analysis of multiple target genes can be cumbersome and expensive. PCR-independent analysis, such as metagenomics and metatranscriptomics, is useful but expensive especially when we analyze multiple samples and try to detect N cycle functional genes present at relatively low abundance. Here, we present the application of microfluidic qPCR chip technology to simultaneously quantify and prepare amplicon sequence libraries for multiple N cycle functional genes as well as taxon-specific 16S rRNA gene markers for many samples. This approach, named as N cycle evaluation (NiCE) chip, was evaluated by using DNA from pure and artificially mixed bacterial cultures and by comparing the results with those obtained by conventional qPCR and amplicon sequencing methods. Quantitative results obtained by the NiCE chip were comparable to those obtained by conventional qPCR. In addition, the NiCE chip was successfully applied to examine abundance and diversity of N cycle functional genes in wastewater samples. Although non-specific amplification was detected on the NiCE chip, this could be overcome by optimizing the primer sequences in the future. As the NiCE chip can provide high-throughput format to quantify and prepare sequence libraries for multiple N cycle functional genes, this tool should advance our ability to explore N cycling in various samples. Importance. We report a novel approach, namely Nitrogen Cycle Evaluation (NiCE) chip by using microfluidic qPCR chip technology. By sequencing the amplicons recovered from the NiCE chip, we can assess diversities of the N cycle functional genes. The NiCE chip technology is applicable to analyze the temporal dynamics of the N cycle gene

  9. 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

  10. Multiparameter Cell Cycle Analysis.

    Science.gov (United States)

    Jacobberger, James W; Sramkoski, R Michael; Stefan, Tammy; Woost, Philip G

    2018-01-01

    Cell cycle cytometry and analysis are essential tools for studying cells of model organisms and natural populations (e.g., bone marrow). Methods have not changed much for many years. The simplest and most common protocol is DNA content analysis, which is extensively published and reviewed. The next most common protocol, 5-bromo-2-deoxyuridine S phase labeling detected by specific antibodies, is also well published and reviewed. More recently, S phase labeling using 5'-ethynyl-2'-deoxyuridine incorporation and a chemical reaction to label substituted DNA has been established as a basic, reliable protocol. Multiple antibody labeling to detect epitopes on cell cycle regulated proteins, which is what this chapter is about, is the most complex of these cytometric cell cycle assays, requiring knowledge of the chemistry of fixation, the biochemistry of antibody-antigen reactions, and spectral compensation. However, because this knowledge is relatively well presented methodologically in many papers and reviews, this chapter will present a minimal Methods section for one mammalian cell type and an extended Notes section, focusing on aspects that are problematic or not well described in the literature. Most of the presented work involves how to segment the data to produce a complete, progressive, and compartmentalized cell cycle analysis from early G1 to late mitosis (telophase). A more recent development, using fluorescent proteins fused with proteins or peptides that are degraded by ubiquitination during specific periods of the cell cycle, termed "Fucci" (fluorescent, ubiquitination-based cell cycle indicators) provide an analysis similar in concept to multiple antibody labeling, except in this case cells can be analyzed while living and transgenic organisms can be created to perform cell cycle analysis ex or in vivo (Sakaue-Sawano et al., Cell 132:487-498, 2007). This technology will not be discussed.

  11. Evaluation method for regional water cycle health based on nature-society water cycle theory

    Science.gov (United States)

    Zhang, Shanghong; Fan, Weiwei; Yi, Yujun; Zhao, Yong; Liu, Jiahong

    2017-08-01

    Regional water cycles increasingly reflect the dual influences of natural and social processes, and are affected by global climate change and expanding human activities. Understanding how to maintain a healthy state of the water cycle has become an important proposition for sustainable development of human society. In this paper, natural-social attributes of the water cycle are synthesized and 19 evaluation indices are selected from four dimensions, i.e., water-based ecosystem integrity, water quality, water resource abundance and water resource use. A hierarchical water-cycle health evaluation system is established. An analytic hierarchy process is used to set the weight of the criteria layer and index layer, and the health threshold for each index is defined. Finally, a water-cycle health composite-index assessment model and fuzzy recognition model are constructed based on the comprehensive index method and fuzzy mathematics theory. The model is used to evaluate the state of health of the water cycle in Beijing during 2010-2014 and in the planning year (late 2014), considering the transfer of 1 billion m3 of water by the South-to-North Water Diversion Project (SNWDP). The results show health scores for Beijing of 2.87, 3.10, 3.38, 3.11 and 3.02 during 2010-2014. The results of fuzzy recognition show that the sub-healthy grade accounted for 54%, 49%, 61% and 49% of the total score, and all years had a sub-healthy state. Results of the criteria layer analysis show that water ecosystem function, water quality and water use were all at the sub-healthy level and that water abundance was at the lowest, or sick, level. With the water transfer from the SNWDP, the health score of the water cycle in Beijing reached 4.04. The healthy grade accounted for 60% of the total score, and the water cycle system was generally in a healthy state. Beijing's water cycle health level is expected to further improve with increasing water diversion from the SNWDP and industrial

  12. 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.

  13. Political Budget Cycles

    DEFF Research Database (Denmark)

    Aaskoven, Lasse; Lassen, David Dreyer

    2017-01-01

    The political budget cycle—how elections affect government fiscal policy—is one of the most studied subjects in political economy and political science. The key theoretical question is whether incumbent governments can time or structure public finances in ways that improve their chances of reelec......The political budget cycle—how elections affect government fiscal policy—is one of the most studied subjects in political economy and political science. The key theoretical question is whether incumbent governments can time or structure public finances in ways that improve their chances...... on political budget cycles have recently focused on conditions under which such cycles are likely to obtain. Much recent research focuses on subnational settings, allowing comparisons of governments in similar institutional environments, and a consensus on the presences of cycles in public finances...

  14. Fuel cycle economics of HTRs

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, U.

    1975-06-15

    The High Temperature Reactor commands a unique fuel cycle flexibility and alternative options are open to the utilities. The reference thorium reactor operating in the U-233 recycle mode is 10 to 20% cheaper than the low-enriched reactor; however, the thorium cycle depends on the supply of 93% enriched uranium and the availability of reprocessing and refabrication facilities to utilize its bred fissile material. The economic landscape towards the end of the 20th Century will presumably be dominated by pronounced increases in the costs of natural resources. In the case of nuclear energy, resource considerations are reflected in the price of uranium, which is expected Lo have reached 50 $/lbm U3O8 in the early 1990s and around 100 $/lbm U3O8 around 2010. In this economic environment the fuel cycle advantage of the thorium system amounts to some 20% and is capable of absorbing substantial expenses in bringing about the closing of the out-of-pile cycle. A most attractive aspect of the HTR fuel cycle flexibility is for the utility to start operating the reactor on the low enriched uranium cycle and at a later date switch over to the thorium cycle as this becomes economically more and more attractive. The incentive amounts to some 50 M$ in terms of present worth money at the time of decision making, assumed to take place 10 years after start-up. The closing of the thorium cycle is of paramount importance and a step to realize this objective lies in simplifying the head-end reprocessing technology by abandoning the segregation concept of feed and breed coated particles in the reference cycle. A one-coated-particle scheme in which all discharged uranium isotopes are recycled in mixed oxide particles is feasible and suffers a very minor economic penalty only.

  15. Cycle bases to the rescue

    Science.gov (United States)

    Tóbiás, Roland; Furtenbacher, Tibor; Császár, Attila G.

    2017-12-01

    Cycle bases of graph theory are introduced for the analysis of transition data deposited in line-by-line rovibronic spectroscopic databases. The principal advantage of using cycle bases is that outlier transitions -almost always present in spectroscopic databases built from experimental data originating from many different sources- can be detected and identified straightforwardly and automatically. The data available for six water isotopologues, H216O, H217O, H218O, HD16O, HD17O, and HD18O, in the HITRAN2012 and GEISA2015 databases are used to demonstrate the utility of cycle-basis-based outlier-detection approaches. The spectroscopic databases appear to be sufficiently complete so that the great majority of the entries of the minimum cycle basis have the minimum possible length of four. More than 2000 transition conflicts have been identified for the isotopologue H216O in the HITRAN2012 database, the seven common conflict types are discussed. It is recommended to employ cycle bases, and especially a minimum cycle basis, for the analysis of transitions deposited in high-resolution spectroscopic databases.

  16. Optimization of the fuel cycle

    International Nuclear Information System (INIS)

    Kidd, S.W.; Balu, K.; Boczar, P.G.; Krebs, W.D.

    1999-01-01

    The nuclear fuel cycle can be optimized subject to a wide range of criteria. Prime amongst these are economics, sustainability of resources, environmental aspects, and proliferation-resistance of the fuel cycle. Other specific national objectives will also be important. These criteria, and their relative importance, will vary from country to country, and with time. There is no single fuel cycle strategy that is optimal for all countries. Within the short term, the industry is attached to dominant thermal reactor technologies, which themselves have two main variants, a cycle closed by reprocessing of spent fuel and subsequent recycling and a once through one where spent fuel is stored in advance of geological disposal. However, even with current technologies, much can be done to optimize the fuel cycles to meet the relevant criteria. In the long term, resource sustainability can be assured for centuries through the use of fast breeder reactors, supporting high-conversion thermal reactors, possibly also utilizing the thorium cycle. These must, however, meet the other key criteria by being both economic and safe. (author)

  17. Gender differences in recreational and transport cycling: a cross-sectional mixed-methods comparison of cycling patterns, motivators, and constraints

    Directory of Open Access Journals (Sweden)

    Heesch Kristiann C

    2012-09-01

    Full Text Available Abstract Background Gender differences in cycling are well-documented. However, most analyses of gender differences make broad comparisons, with few studies modeling male and female cycling patterns separately for recreational and transport cycling. This modeling is important, in order to improve our efforts to promote cycling to women and men in countries like Australia with low rates of transport cycling. The main aim of this study was to examine gender differences in cycling patterns and in motivators and constraints to cycling, separately for recreational and transport cycling. Methods Adult members of a Queensland, Australia, community bicycling organization completed an online survey about their cycling patterns; cycling purposes; and personal, social and perceived environmental motivators and constraints (47% response rate. Closed and open-end questions were completed. Using the quantitative data, multivariable linear, logistic and ordinal regression models were used to examine associations between gender and cycling patterns, motivators and constraints. The qualitative data were thematically analyzed to expand upon the quantitative findings. Results In this sample of 1862 bicyclists, men were more likely than women to cycle for recreation and for transport, and they cycled for longer. Most transport cycling was for commuting, with men more likely than women to commute by bicycle. Men were more likely to cycle on-road, and women off-road. However, most men and women did not prefer to cycle on-road without designed bicycle lanes, and qualitative data indicated a strong preference by men and women for bicycle-only off-road paths. Both genders reported personal factors (health and enjoyment related as motivators for cycling, although women were more likely to agree that other personal, social and environmental factors were also motivating. The main constraints for both genders and both cycling purposes were perceived environmental factors

  18. Sometimes "Newton's Method" Always "Cycles"

    Science.gov (United States)

    Latulippe, Joe; Switkes, Jennifer

    2012-01-01

    Are there functions for which Newton's method cycles for all non-trivial initial guesses? We construct and solve a differential equation whose solution is a real-valued function that two-cycles under Newton iteration. Higher-order cycles of Newton's method iterates are explored in the complex plane using complex powers of "x." We find a class of…

  19. Accounting for the biogeochemical cycle of nitrogen in input-output life cycle assessment.

    Science.gov (United States)

    Singh, Shweta; Bakshi, Bhavik R

    2013-08-20

    Nitrogen is indispensable for sustaining human activities through its role in the production of food, animal feed, and synthetic chemicals. This has encouraged significant anthropogenic mobilization of reactive nitrogen and its emissions into the environment resulting in severe disruption of the nitrogen cycle. This paper incorporates the biogeochemical cycle of nitrogen into the 2002 input-output model of the U.S. economy. Due to the complexity of this cycle, this work proposes a unique classification of nitrogen flows to facilitate understanding of the interaction between economic activities and various flows in the nitrogen cycle. The classification scheme distinguishes between the mobilization of inert nitrogen into its reactive form, use of nitrogen in various products, and nitrogen losses to the environment. The resulting inventory and model of the US economy can help quantify the direct and indirect impacts or dependence of economic sectors on the nitrogen cycle. This paper emphasizes the need for methods to manage the N cycle that focus not just on N losses, which has been the norm until now, but also include other N flows for a more comprehensive view and balanced decisions. Insight into the N profile of various sectors of the 2002 U.S. economy is presented, and the inventory can also be used for LCA or Hybrid LCA of various products. The resulting model is incorporated in the approach of Ecologically-Based LCA and available online.

  20. Fuel cycle modelling of open cycle thorium-fuelled nuclear energy systems

    International Nuclear Information System (INIS)

    Ashley, S.F.; Lindley, B.A.; Parks, G.T.; Nuttall, W.J.; Gregg, R.; Hesketh, K.W.; Kannan, U.; Krishnani, P.D.; Singh, B.; Thakur, A.; Cowper, M.; Talamo, A.

    2014-01-01

    Highlights: • We study three open cycle Th–U-fuelled nuclear energy systems. • Comparison of these systems is made to a reference U-fuelled EPR. • Fuel cycle modelling is performed with UK NNL code “ORION”. • U-fuelled system is economically favourable and needs least separative work per kWh. • Th–U-fuelled systems offer negligible waste and proliferation resistance advantages. - Abstract: In this study, we have sought to determine the advantages, disadvantages, and viability of open cycle thorium–uranium-fuelled (Th–U-fuelled) nuclear energy systems. This has been done by assessing three such systems, each of which requires uranium enriched to ∼20% 235 U, in comparison to a reference uranium-fuelled (U-fuelled) system over various performance indicators, spanning material flows, waste composition, economics, and proliferation resistance. The values of these indicators were determined using the UK National Nuclear Laboratory’s fuel cycle modelling code ORION. This code required the results of lattice-physics calculations to model the neutronics of each nuclear energy system, and these were obtained using various nuclear reactor physics codes and burn-up routines. In summary, all three Th–U-fuelled nuclear energy systems required more separative work capacity than the equivalent benchmark U-fuelled system, with larger levelised fuel cycle costs and larger levelised cost of electricity. Although a reduction of ∼6% in the required uranium ore per kWh was seen for one of the Th–U-fuelled systems compared to the reference U-fuelled system, the other two Th–U-fuelled systems required more uranium ore per kWh than the reference. Negligible advantages and disadvantages were observed for the amount and the properties of the spent nuclear fuel (SNF) generated by the systems considered. Two of the Th–U-fuelled systems showed some benefit in terms of proliferation resistance of the SNF generated. Overall, it appears that there is little

  1. The life cycle of centrioles.

    Science.gov (United States)

    Hatch, E; Stearns, T

    2010-01-01

    Centrioles organize the centrosome and nucleate the ciliary axoneme, and the centriole life cycle has many parallels to the chromosome cycle. The centriole cycle in animals begins at fertilization with the contribution of two centrioles by the male gamete. In the ensuing cell cycles, the duplication of centrioles is controlled temporally, spatially, and numerically. As a consequence of the duplication mechanism, the two centrioles in a typical interphase cell are of different ages and have different functions. Here, we discuss how new centrioles are assembled, what mechanisms limit centriole number, and the consequences of the inherent asymmetry of centriole duplication and segregation.

  2. Pseudo-simple heteroclinic cycles in R4

    Science.gov (United States)

    Chossat, Pascal; Lohse, Alexander; Podvigina, Olga

    2018-06-01

    We study pseudo-simple heteroclinic cycles for a Γ-equivariant system in R4 with finite Γ ⊂ O(4) , and their nearby dynamics. In particular, in a first step towards a full classification - analogous to that which exists already for the class of simple cycles - we identify all finite subgroups of O(4) admitting pseudo-simple cycles. To this end we introduce a constructive method to build equivariant dynamical systems possessing a robust heteroclinic cycle. Extending a previous study we also investigate the existence of periodic orbits close to a pseudo-simple cycle, which depends on the symmetry groups of equilibria in the cycle. Moreover, we identify subgroups Γ ⊂ O(4) , Γ ⊄ SO(4) , admitting fragmentarily asymptotically stable pseudo-simple heteroclinic cycles. (It has been previously shown that for Γ ⊂ SO(4) pseudo-simple cycles generically are completely unstable.) Finally, we study a generalized heteroclinic cycle, which involves a pseudo-simple cycle as a subset.

  3. Extended fuel cycle length

    International Nuclear Information System (INIS)

    Bruyere, M.; Vallee, A.; Collette, C.

    1986-09-01

    Extended fuel cycle length and burnup are currently offered by Framatome and Fragema in order to satisfy the needs of the utilities in terms of fuel cycle cost and of overall systems cost optimization. We intend to point out the consequences of an increased fuel cycle length and burnup on reactor safety, in order to determine whether the bounding safety analyses presented in the Safety Analysis Report are applicable and to evaluate the effect on plant licensing. This paper presents the results of this examination. The first part indicates the consequences of increased fuel cycle length and burnup on the nuclear data used in the bounding accident analyses. In the second part of this paper, the required safety reanalyses are presented and the impact on the safety margins of different fuel management strategies is examined. In addition, systems modifications which can be required are indicated

  4. Detonation Jet Engine. Part 1--Thermodynamic Cycle

    Science.gov (United States)

    Bulat, Pavel V.; Volkov, Konstantin N.

    2016-01-01

    We present the most relevant works on jet engine design that utilize thermodynamic cycle of detonative combustion. The efficiency advantages of thermodynamic detonative combustion cycle over Humphrey combustion cycle at constant volume and Brayton combustion cycle at constant pressure were demonstrated. An ideal Ficket-Jacobs detonation cycle, and…

  5. ITER fuel cycle

    International Nuclear Information System (INIS)

    Leger, D.; Dinner, P.; Yoshida, H.

    1991-01-01

    Resulting from the Conceptual Design Activities (1988-1990) by the parties involved in the International Thermonuclear Experimental Reactor (ITER) project, this document summarizes the design requirements and the Conceptual Design Descriptions for each of the principal subsystems and design options of the ITER Fuel Cycle conceptual design. The ITER Fuel Cycle system provides for the handling of all tritiated water and gas mixtures on ITER. The system is subdivided into subsystems for fuelling, primary (torus) vacuum pumping, fuel processing, blanket tritium recovery, and common processes (including isotopic separation, fuel management and storage, and processes for detritiation of solid, liquid, and gaseous wastes). After an introduction describing system function and conceptual design procedure, a summary of the design is presented including a discussion of scope and main parameters, and the fuel design options for fuelling, plasma chamber vacuum pumping, fuel cleanup, blanket tritium recovery, and auxiliary and common processes. Design requirements are defined and design descriptions are given for the various subsystems (fuelling, plasma vacuum pumping, fuel cleanup, blanket tritium recovery, and auxiliary/common processes). The document ends with sections on fuel cycle design integration, fuel cycle building layout, safety considerations, a summary of the research and development programme, costing, and conclusions. Refs, figs and tabs

  6. Quantifying the Adaptive Cycle.

    Directory of Open Access Journals (Sweden)

    David G Angeler

    Full Text Available The adaptive cycle was proposed as a conceptual model to portray patterns of change in complex systems. Despite the model having potential for elucidating change across systems, it has been used mainly as a metaphor, describing system dynamics qualitatively. We use a quantitative approach for testing premises (reorganisation, conservatism, adaptation in the adaptive cycle, using Baltic Sea phytoplankton communities as an example of such complex system dynamics. Phytoplankton organizes in recurring spring and summer blooms, a well-established paradigm in planktology and succession theory, with characteristic temporal trajectories during blooms that may be consistent with adaptive cycle phases. We used long-term (1994-2011 data and multivariate analysis of community structure to assess key components of the adaptive cycle. Specifically, we tested predictions about: reorganisation: spring and summer blooms comprise distinct community states; conservatism: community trajectories during individual adaptive cycles are conservative; and adaptation: phytoplankton species during blooms change in the long term. All predictions were supported by our analyses. Results suggest that traditional ecological paradigms such as phytoplankton successional models have potential for moving the adaptive cycle from a metaphor to a framework that can improve our understanding how complex systems organize and reorganize following collapse. Quantifying reorganization, conservatism and adaptation provides opportunities to cope with the intricacies and uncertainties associated with fast ecological change, driven by shifting system controls. Ultimately, combining traditional ecological paradigms with heuristics of complex system dynamics using quantitative approaches may help refine ecological theory and improve our understanding of the resilience of ecosystems.

  7. The effectiveness of community-based cycling promotion: findings from the Cycling Connecting Communities project in Sydney, Australia

    Directory of Open Access Journals (Sweden)

    Merom Dafna

    2010-01-01

    Full Text Available Abstract Background Encouraging cycling is an important way to increase physical activity in the community. The Cycling Connecting Communities (CCC Project is a community-based cycling promotion program that included a range of community engagement and social marketing activities, such as organised bike rides and events, cycling skills courses, the distribution of cycling maps of the area and coverage in the local press. The aim of the study was to assess the effectiveness of this program designed to encourage the use of newly completed off-road cycle paths through south west Sydney, Australia. Methods The evaluation used a quasi-experimental design that consisted of a pre- and post-intervention telephone survey (24 months apart of a cohort of residents (n = 909 in the intervention area (n = 520 (Fairfield and Liverpool and a socio-demographically similar comparison area (n = 389 (Bankstown. Both areas had similar bicycle infrastructure. Four bicycle counters were placed on the main bicycle paths in the intervention and comparison areas to monitor daily bicycle use before and after the intervention. Results The telephone survey results showed significantly greater awareness of the Cycling Connecting Communities project (13.5% vs 8.0%, p Conclusion Despite relatively modest resources, the Cycling Connecting Communities project achieved significant increases in bicycle path use, and increased cycling in some sub-groups. However, this community based intervention with limited funding had very limited reach into the community and did not increase population cycling levels.

  8. Sadi Carnot and the Second Law of Thermodynamics

    Indian Academy of Sciences (India)

    (or thermal energy) to work in a continuous process. ... He wan ted to popularize the use of steam engines in ... The study of these engines is of great .... Germany is clear as the German pronounciation of the letter'S' is similar to the English.

  9. The spatial dimension of cycle logistics

    Directory of Open Access Journals (Sweden)

    Luca Staricco

    2016-08-01

    Full Text Available Cycle logistics is emerging as a promising alternative in urban freight transport. Compared to fossil fuelled vans, the use of cycles for delivering goods within urban areas offers advantages in terms of environmental friendliness, economic efficiency, flexibility, and liveability of urban neighbourhood. At the same time, cycle logistics has to face limits in terms of weight and volume of goods that can be delivered, distances that can be covered, and spatial urban structures that can be served. This latter issue has till now received less attention in the scientific literature: it is generally recognized that cycle logistics performs at its best in inner urban areas, but no systematic study has been realized to identify specific spatial requisites for the effectiveness of cycle logistics. This paper provides a brief review of the main issues that emerge from the literature over cycle logistics, and contributes to stimulate the debate over the spatial dimension of cycle logistics: it presents a classification of cycle logistics schemes, on the basis of their integration with other urban logistic facilities and of the spatial structure of delivery operations. A three-level classification is proposed, depending on the type of goods consolidation: only distribution without consolidation, consolidation in a fixed urban consolidation centre, or consolidation in a mobile depot; for each level, operational examples and case studies are provided. This systematizing typology could support both public and private operators in decisions about the organization of cycle logistics facilities, such as the location of urban consolidation centres or the composition of cycle fleets.

  10. Economic evaluation of fast reactor fuel cycling

    International Nuclear Information System (INIS)

    Hu Ping; Zhao Fuyu; Yan Zhou; Li Chong

    2012-01-01

    Economic calculation and analysis of two kinds of nuclear fuel cycle are conducted by check off method, based on the nuclear fuel cycling process and model for fast reactor power plant, and comparison is carried out for the economy of fast reactor fuel cycle and PWR once-through fuel cycle. Calculated based on the current price level, the economy of PWR one-through fuel cycle is better than that of the fast reactor fuel cycle. However, in the long term considering the rising of the natural uranium's price and the development of the post treatment technology for nuclear fuels, the cost of the fast reactor fuel cycle is expected to match or lower than that of the PWR once-through fuel cycle. (authors)

  11. Analysis of possible fuel cycles

    International Nuclear Information System (INIS)

    Boehm, H.; Kessler, G.; Engelmann, P.; Maerkl, H.; Stoll, W.

    1978-01-01

    A brief survey is presented of the most important fuel cycles. A rough analysis of fuel cycles is attempted under the aspects of proliferation, status of technical feasibility, resource conservation and waste management and the most important criteria for such an analysis are discussed. Among the multitude of potential combinations of fuel cycles and types of reactors only a few have reached a level of technical feasibility which would make them eligible for commercial implementation within the next decade. However, if, for instance, the higher proliferation resistance of a specific fuel cycle is to be utilized to diminish the worldwide proliferation hazard, that cycle would first of all have to be introduced on an industrial scale as quickly as possible. The analysis shows that the reduction of the bazard of worldwide proliferation will continue to be the objective primarily of international agreements and measures taken in the political realm. (orig.) [de

  12. Advanced Fuel Cycle Economic Sensitivity Analysis

    Energy Technology Data Exchange (ETDEWEB)

    David Shropshire; Kent Williams; J.D. Smith; Brent Boore

    2006-12-01

    A fuel cycle economic analysis was performed on four fuel cycles to provide a baseline for initial cost comparison using the Gen IV Economic Modeling Work Group G4 ECON spreadsheet model, Decision Programming Language software, the 2006 Advanced Fuel Cycle Cost Basis report, industry cost data, international papers, the nuclear power related cost study from MIT, Harvard, and the University of Chicago. The analysis developed and compared the fuel cycle cost component of the total cost of energy for a wide range of fuel cycles including: once through, thermal with fast recycle, continuous fast recycle, and thermal recycle.

  13. Polity age and political budget cycles

    DEFF Research Database (Denmark)

    Aaskoven, Lasse

    2018-01-01

    Incumbent incentive for competence-signaling and lack of voter information are generally thought to be factors that increase the prevalence of political budget cycles. These mechanisms should be more prevalent in new political units. Since the creation of new political units is rarely exogenous......-experimental to study whether political budget cycles are larger in new political units. Contrary to theoretical predictions, political budget cycles seem to be of a smaller scale in the new municipalities, but only regarding budget cycles in budgetary overruns. The findings are of wider interest for discussions about...... the mechanisms behind context-conditional political budget cycles....

  14. The thorium fuel cycle

    International Nuclear Information System (INIS)

    Merz, E.R.

    1977-01-01

    The utilization of the thorium fuel cycle has long since been considered attractive owing to the excellent neutronic characteristics of 233 U, and the widespread and cheap thorium resources. Rapidly increasing uranium prices, public reluctance for widespread Pu recycling and expected delays for the market penetration of fast breeders have led to a reconsideration of the thorium fuel cycle merits. In addition, problems associated with reprocessing and waste handling, particularly with re-fabrication by remote handling of 233 U, are certainly not appreciably more difficult than for Pu recycling. To divert from uranium as a nuclear energy source it seems worth while intensifying future efforts for closing the Th/ 233 U fuel cycle. HTGRs are particularly promising for economic application. However, further research and development activities should not concentrate on this reactor type alone. Light- and heavy-water-moderated reactors, and even future fast breeders, may just as well take advantage of a demonstrated thorium fuel cycle. (author)

  15. Understanding Solar Cycle Variability

    Energy Technology Data Exchange (ETDEWEB)

    Cameron, R. H.; Schüssler, M., E-mail: cameron@mps.mpg.de [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany)

    2017-07-10

    The level of solar magnetic activity, as exemplified by the number of sunspots and by energetic events in the corona, varies on a wide range of timescales. Most prominent is the 11-year solar cycle, which is significantly modulated on longer timescales. Drawing from dynamo theory, together with the empirical results of past solar activity and similar phenomena for solar-like stars, we show that the variability of the solar cycle can be essentially understood in terms of a weakly nonlinear limit cycle affected by random noise. In contrast to ad hoc “toy models” for the solar cycle, this leads to a generic normal-form model, whose parameters are all constrained by observations. The model reproduces the characteristics of the variable solar activity on timescales between decades and millennia, including the occurrence and statistics of extended periods of very low activity (grand minima). Comparison with results obtained with a Babcock–Leighton-type dynamo model confirm the validity of the normal-mode approach.

  16. Out-of-core nuclear fuel cycle economic optimization for nonequilibrium cycles

    International Nuclear Information System (INIS)

    Comes, S.A.

    1987-01-01

    A methodology and associated computer code was developed to determine near-optimum out-of-core fuel management strategies. The code, named OCEON (Out-of-Core Economic OptimizationN), identified feed-region sizes and enrichments, and partially burned fuel-reload strategies for each cycle of a multi-cycle planning horizon, subject to cycle-energy requirements and constraints on feed enrichments, discharge burnups, and the moderator temperature coefficient. A zero-dimensional reactor physics model, enhanced by a linear reactivity model to provide batch power shares, performs the initial feed enrichment, burnup and constraint evaluations, while a two-dimensional, nodal code is used to refine the calculations for the final solutions. The economic calculations are performed rapidly using an annuity-factor-based model. Use of Monte Carlo integer programming to select the optimum solutions allows for the determination of a family of near-optimum solutions, from which engineering judgment may be used to select an appropriate strategy. Results from various nonequilibrium cycle energy requirement cases typically show a large number of low-cost solutions near the optimum. This confirms that the Monte Carlo integer programming approach of generating a family of solutions will be most useful for selecting optimum strategies when other considerations, such as incore loading pattern concerns, must be addressed

  17. Parametric-based thermodynamic analysis of organic Rankine cycle as bottoming cycle for combined-cycle power plant

    International Nuclear Information System (INIS)

    Qureshi, S.; Memon, A.G.; Abbasi, A.F.

    2017-01-01

    In Pakistan, the thermal efficiency of the power plants is low because of a huge share of fuel energy is dumped into the atmosphere as waste heat. The ORC (Organic Rankine Cycle) has been revealed as one of the promising technologies to recover waste heat to enhance the thermal efficiency of the power plant. In current work, ORC is proposed as a second bottoming cycle for existing CCPP (Combined Cycle Power Plant). In order to assess the efficiency of the plant, a thermodynamic model is developed in the ESS (Engineering Equation Solver) software. The developed model is used for parametric analysis to assess the effects of various operating parameters on the system performance. The analysis of results shows that the integration of ORC system with existing CCPP system enhances the overall power output in the range of 150.5-154.58 MW with 0.24-5% enhancement in the efficiency depending on the operating conditions. During the parametric analysis of ORC, it is observed that inlet pressure of the turbine shows a significant effect on the performance of the system as compared to other operating parameters. (author)

  18. BUSINESS CYCLES, ELECTORAL CYCLES. TOWARD A THEORETICAL FRAME OF INTERACTION

    Directory of Open Access Journals (Sweden)

    BOGDAN-LUCIAN DOSPINESCU

    2015-06-01

    Full Text Available The idea of cyclical movement of a system: be it political, economic, institutional, is one of the constants of critical thinking. In this sense, there is a natural cyclic movement that cannot be avoided (only amplified or diminished and is connected with the nature of these systems. The economy follows a cyclical movement; a period of growth follows a period of decline, and so on. So does popularity for political parties or leaders. In this paper, I explore the links between the business cycles and electoral cycles. For this purpose, I introduce the concept of electoral perception cycles. My hypothesis is that popularity of political parties and leaders follow a cyclical evolution, both on short and long term. I show how perception cycles can impact the “political business cycle theory”. There is great interest in political science literature for the factors that influence the fluctuations in Presidents’ popularity, especially from United States. However, very little has been said about Romania’s case. I investigate the hypothesis of electoral perception cycles looking at the popularity of former president Traian Basescu, over his two terms. The variable used to measure popularity is favorability, measured in national surveys, done face to face, on representative samplez, of around 1000 subjects. I’ve correlated the fluctuations in favorability over time, with key public events or political decisions taken by Traian Băsescu. The main findings are as follows. Firstly, there are significant short term fluctuations (short term perception cycles and they are correlated with major events on the agenda. I would point the following key moments: 1. The referendum for dismissal of the President in May 2007 – Traian Băsescu’s favorability increased by 7 percentage points; 2. The referendum for unicameral Parliament with 300 MPs in the fall of 2009. Coupled with victory in the presidential election, it lead to an increase of 10 percentage

  19. Gender differences in recreational and transport cycling: a cross-sectional mixed-methods comparison of cycling patterns, motivators, and constraints

    OpenAIRE

    Heesch, Kristiann C; Sahlqvist, Shannon; Garrard, Jan

    2012-01-01

    Abstract Background Gender differences in cycling are well-documented. However, most analyses of gender differences make broad comparisons, with few studies modeling male and female cycling patterns separately for recreational and transport cycling. This modeling is important, in order to improve our efforts to promote cycling to women and men in countries like Australia with low rates of transport cycling. The main aim of this study was to examine gender differences in cycling patterns and i...

  20. IFR fuel cycle demonstration in the EBR-II Fuel Cycle Facility

    International Nuclear Information System (INIS)

    Lineberry, M.J.; Phipps, R.D.; Rigg, R.H.; Benedict, R.W.; Carnes, M.D.; Herceg, J.E.; Holtz, R.E.

    1991-01-01

    The next major milestone of the IFR (Integral Fast Reactor) program is engineering-scale demonstration of the pyroprocess fuel cycle. The EBR-II Fuel Cycle Facility has just entered a startup phase which includes completion of facility modifications, and installation and cold checkout of process equipment. This paper reviews the design and construction of the facility, the design and fabrication of the process equipment, and the schedule and initial plan for its operation. (author)

  1. IFR fuel cycle demonstration in the EBR-II Fuel Cycle Facility

    International Nuclear Information System (INIS)

    Lineberry, M.J.; Phipps, R.D.; Rigg, R.H.; Benedict, R.W.; Carnes, M.D.; Herceg, J.E.; Holtz, R.E.

    1991-01-01

    The next major milestone of the IFR program is engineering-scale demonstration of the pyroprocess fuel cycle. The EBR-II Fuel Cycle Facility has just entered a startup phase which includes completion of facility modifications, and installation and cold checkout of process equipment. This paper reviews the design and construction of the facility, the design and fabrication of the process equipment, and the schedule and initial plan for its operation. 5 refs., 4 figs

  2. IFR fuel cycle

    International Nuclear Information System (INIS)

    Battles, J.E.; Miller, W.E.; Lineberry, M.J.; Phipps, R.D.

    1992-01-01

    The next major milestone of the IFR program is engineering-scale demonstration of the pyroprocess fuel cycle. The EBR-II Fuel Cycle Facility has just entered a startup phase, which includes completion of facility modifications and installation and cold checkout of process equipment. This paper reviews the development of the electrorefining pyroprocess, the design and construction of the facility for the hot demonstration, the design and fabrication of the equipment, and the schedule and initial plan for its operation

  3. Life Cycle Impact Assessment

    DEFF Research Database (Denmark)

    Rosenbaum, Ralph K.; Hauschild, Michael Zwicky; Boulay, Anne-Marie

    2018-01-01

    This chapter is dedicated to the third phase of an LCA study, the Life Cycle Impact Assessment (LCIA) where the life cycle inventory’s information on elementary flows is translated into environmental impact scores. In contrast to the three other LCA phases, LCIA is in practice largely automated...

  4. Management Cycle: from Planning to Evaluation

    OpenAIRE

    Kova?i?, Luka; Jakši?, Želimir

    2008-01-01

    The planning process in health care known as management cycle or cycle of organization and management is described. The cycle is divided in four main elements: planning, organization, implementation and evaluation. Each element is defined and described.

  5. Cycling environmental perception in Beijing – A study of residents' attitudes towards future cycling and car purchasing

    DEFF Research Database (Denmark)

    Zhao, Chunli; Nielsen, Thomas Alexander Sick; Olafsson, Anton Stahl

    2018-01-01

    distances up to 2 km are positively linked to future cycling prospects. Non-car owners' attitude to future car ownership is strongly linked to socio-demographic status - low education and low income level groups seems to be most unlikely to take up driving in the future. To encourage people to cycle more...... and drive less, policy should direct efforts to promoting the clarity of cycling space on the street and strengthen pro-cycling policies. Attention should also be given to stabilizing the current travel modes of non-car users, including promoting the image of cycling, improving the service of walking...

  6. The thorium fuel cycle

    International Nuclear Information System (INIS)

    Merz, E.R.

    1977-01-01

    The utilization of the thorium fuel cycle has long since been considered attractive due to the excellent neutronic characteristics of 233 U, and the widespread and cheap thorium resources. Although the uranium ore as well as the separative work requirements are usually lower for any thorium-based fuel cycle in comparison to present uranium-plutonium fuel cycles of thermal water reactors, interest by nuclear industry has hitherto been marginal. Fast increasing uranium prices, public reluctance against widespread Pu-recycling and expected retardations for the market penetration of fast breeders have led to a reconsideration of the thorium fuel cycle merits. In addition, it could be learned in the meantime that problems associated with reprocessing and waste handling, but particularly with a remote refabrication of 233 U are certainly not appreciably more difficult than for Pu-recycling. This may not only be due to psychological constraints but be based upon technological as well as economical facts, which have been mostly neglected up till now. In order to diversify from uranium as a nuclear energy source it seems to be worthwhile to greatly intensify efforts in the future for closing the Th/ 233 U fuel cycle. HTGR's are particularly promising for economic application. However, further R and D activites should not be solely focussed on this reactor type alone. Light and heavy-water moderated reactors, as well as even fast breeders later on, may just as well take advantage of a demonstrated thorium fuel cycle. A summary is presented of the state-of-the-art of Th/ 233 U-recycling technology and the efforts still necessary to demonstrate this technology all the way through to its industrial application

  7. Advanced fuel cycles in CANDU reactors

    International Nuclear Information System (INIS)

    Green, R.E.; Boczar, P.G.

    1990-04-01

    This paper re-examines the rationale for advanced nuclear fuel cycles in general, and for CANDU advanced fuel cycles in particular. The traditional resource-related arguments for more uranium nuclear fuel cycles are currently clouded by record-low prices for uranium. However, the total known conventional uranium resources can support projected uranium requirements for only another 50 years or so, less if a major revival of the nuclear option occurs as part of the solution to the world's environmental problems. While the extent of the uranium resource in the earth's crust and oceans is very large, uncertainty in the availability and price of uranium is the prime resource-related motivation for advanced fuel cycles. There are other important reasons for pursuing advanced fuel cycles. The three R's of the environmental movement, reduce, recycle, reuse, can be achieved in nuclear energy production through the employment of advanced fuel cycles. The adoption of more uranium-conserving fuel cycles would reduce the amount of uranium which needs to be mined, and the environmental impact of that mining. Environmental concerns over the back end of the fuel cycle can be mitigated as well. Higher fuel burnup reduces the volume of spent fuels which needs to be disposed of. The transmutation of actinides and long-lived fission products into short-lived fission products would reduce the radiological hazard of the waste from thousands to hundreds of years. Recycling of uranium and/or plutonium in spent fuel reuses valuable fissile material, leaving only true waste to be disposed of. Advanced fuel cycles have an economical benefit as well, enabling a ceiling to be put on fuel cycle costs, which are

  8. Life-cycle assessment of semiconductors

    CERN Document Server

    Boyd, Sarah B

    2012-01-01

    Life-Cycle Assessment of Semiconductors presents the first and thus far only available transparent and complete life cycle assessment of semiconductor devices. A lack of reliable semiconductor LCA data has been a major challenge to evaluation of the potential environmental benefits of information technologies (IT). The analysis and results presented in this book will allow a higher degree of confidence and certainty in decisions concerning the use of IT in efforts to reduce climate change and other environmental effects. Coverage includes but is not limited to semiconductor manufacturing trends by product type and geography, unique coverage of life-cycle assessment, with a focus on uncertainty and sensitivity analysis of energy and global warming missions for CMOS logic devices, life cycle assessment of flash memory and life cycle assessment of DRAM. The information and conclusions discussed here will be highly relevant and useful to individuals and institutions. The book also: Provides a detailed, complete a...

  9. Comparative analysis of thermodynamic performance and optimization of organic flash cycle (OFC) and organic Rankine cycle (ORC)

    International Nuclear Information System (INIS)

    Lee, Ho Yong; Park, Sang Hee; Kim, Kyoung Hoon

    2016-01-01

    A comparative thermodynamic performance and optimization analysis of basic organic flash cycle (OFCB), organic flash cycle with two-phase expander (OFCT), and organic Rankine cycle (ORC) activated by low-temperature sensible energy is carried out in the subcritical pressure regions. The three substances of R245fa, R123, and o-xylene are considered as the working fluids. Effects of cycle type, working fluid, and evaporation and source temperatures are systemically investigated on the system performance such as net power production, thermal and exergy efficiencies, and exergy destruction ratios at each component of the systems. Results show that the cycle type or working fluid which shows optimum performance depends on the source temperature, and organic flash cycle shows a potential for efficient recovery of low grade energy source.

  10. Practical introduction of thorium fuel cycles

    International Nuclear Information System (INIS)

    Kasten, P.R.

    1982-01-01

    The pracitcal introduction of throrium fuel cycles implies that thorium fuel cycles compete economically with uranium fuel cycles in economic nuclear power plants. In this study the reactor types under consideration are light water reactors (LWRs), heavy water reactors (HWRs), high-temperature gas-cooled reactors (HTGRs), and fast breeder reactors (FBRs). On the basis that once-through fuel cycles will be used almost exclusively for the next 20 or 25 years, introduction of economic thorium fuel cycles appears best accomplished by commercial introduction of HTGRs. As the price of natural uranium increases, along with commercialization of fuel recycle, there will be increasing incentive to utilize thorium fuel cycles in heavy water reactors and light water reactors as well as in HTGRs. After FBRs and fuel recycle are commercialized, use of thorium fuel cycles in the blanket of FBRs appears advantageous when fast breeder reactors and thermal reactors operate in a symbiosis mode (i.e., where 233 U bred in the blanket of a fast breeder reactor is utilized as fissile fuel in thermal converter reactors)

  11. Thermal cycling in multifilamentary superconducting composites

    International Nuclear Information System (INIS)

    Aragao, E.E.A. de.

    1984-01-01

    NbTi-Cu multifilamentary superconducting composites were embedded, polished, characterized by microscopic techniques, and analyzed in a qualitative and semiquantitative way by energy dispersion technique. The superconductors were submitted to thermal cycling between the ambient temperature and the boiling point of helium (4.2K), for different number of cycles. The aims were to study the correlation between the possible microstructural damages due to thermal stresses arising in the composite during cycling and the variation of properties of the material with the number of cycles as well as to verify the validity of an elastic model for thermal stresses for low temperature cycles. (author)

  12. Understanding the petrochemical cycle: Part 1

    International Nuclear Information System (INIS)

    Sedriks, W.

    1994-01-01

    Fitness in the hydrocarbon processing industry (HPI) arena involves understanding and coping with business cycles: supply and demand. This becomes increasingly more important as the industry globalizes and matures. Competitive-edge thinking needs to look hard at the forces that influence business cycles. Recognition of potential pitfalls is very important when considering: future capacity expansion, mergers and acquisitions, market departure, plant closure, potential product substitution, etc. Understanding pricing mechanisms and the workings of hockey-stick profitability profiles help HPI operators endure cycle downturns and prepare plants to maximize profits for the next upswing. The paper discusses characteristic trends, cycles in the hydrocarbon processing industry, current conditions, and mitigating cycle effects

  13. Life cycle management (LCM)

    DEFF Research Database (Denmark)

    Remmen, Arne; Thrane, Mikkel

    2004-01-01

    The chapter gives an introduction to Life Cycle Management (LCM) and shows how LCM can be practiced in different contexts and at different ambition levels.......The chapter gives an introduction to Life Cycle Management (LCM) and shows how LCM can be practiced in different contexts and at different ambition levels....

  14. The NEWS Water Cycle Climatology

    Science.gov (United States)

    Rodell, M.; Beaudoing, H. K.; L'Ecuyer, T.; Olson, W. S.

    2012-12-01

    NASA's Energy and Water Cycle Study (NEWS) program fosters collaborative research towards improved quantification and prediction of water and energy cycle consequences of climate change. In order to measure change, it is first necessary to describe current conditions. The goal of the first phase of the NEWS Water and Energy Cycle Climatology project was to develop "state of the global water cycle" and "state of the global energy cycle" assessments based on data from modern ground and space based observing systems and data integrating models. The project was a multi-institutional collaboration with more than 20 active contributors. This presentation will describe the results of the water cycle component of the first phase of the project, which include seasonal (monthly) climatologies of water fluxes over land, ocean, and atmosphere at continental and ocean basin scales. The requirement of closure of the water budget (i.e., mass conservation) at various scales was exploited to constrain the flux estimates via an optimization approach that will also be described. Further, error assessments were included with the input datasets, and we examine these in relation to inferred uncertainty in the optimized flux estimates in order to gauge our current ability to close the water budget within an expected uncertainty range.

  15. The NEWS Water Cycle Climatology

    Science.gov (United States)

    Rodell, Matthew; Beaudoing, Hiroko Kato; L'Ecuyer, Tristan; William, Olson

    2012-01-01

    NASA's Energy and Water Cycle Study (NEWS) program fosters collaborative research towards improved quantification and prediction of water and energy cycle consequences of climate change. In order to measure change, it is first necessary to describe current conditions. The goal of the first phase of the NEWS Water and Energy Cycle Climatology project was to develop "state of the global water cycle" and "state of the global energy cycle" assessments based on data from modern ground and space based observing systems and data integrating models. The project was a multi-institutional collaboration with more than 20 active contributors. This presentation will describe the results of the water cycle component of the first phase of the project, which include seasonal (monthly) climatologies of water fluxes over land, ocean, and atmosphere at continental and ocean basin scales. The requirement of closure of the water budget (i.e., mass conservation) at various scales was exploited to constrain the flux estimates via an optimization approach that will also be described. Further, error assessments were included with the input datasets, and we examine these in relation to inferred uncertainty in the optimized flux estimates in order to gauge our current ability to close the water budget within an expected uncertainty range.

  16. 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.

  17. Work and power fluctuations in a critical heat engine

    Science.gov (United States)

    Holubec, Viktor; Ryabov, Artem

    2017-09-01

    We investigate fluctuations of output work for a class of Stirling heat engines with working fluid composed of interacting units and compare these fluctuations to an average work output. In particular, we focus on engine performance close to a critical point where Carnot's efficiency may be attained at a finite power as reported by M. Campisi and R. Fazio [Nat. Commun. 7, 11895 (2016), 10.1038/ncomms11895]. We show that the variance of work output per cycle scales with the same critical exponent as the heat capacity of the working fluid. As a consequence, the relative work fluctuation diverges unless the output work obeys a rather strict scaling condition, which would be very hard to fulfill in practice. Even under this condition, the fluctuations of work and power do not vanish in the infinite system size limit. Large fluctuations of output work thus constitute inseparable and dominant element in performance of the macroscopic heat engines close to a critical point.

  18. Work and power fluctuations in a critical heat engine.

    Science.gov (United States)

    Holubec, Viktor; Ryabov, Artem

    2017-09-01

    We investigate fluctuations of output work for a class of Stirling heat engines with working fluid composed of interacting units and compare these fluctuations to an average work output. In particular, we focus on engine performance close to a critical point where Carnot's efficiency may be attained at a finite power as reported by M. Campisi and R. Fazio [Nat. Commun. 7, 11895 (2016)2041-172310.1038/ncomms11895]. We show that the variance of work output per cycle scales with the same critical exponent as the heat capacity of the working fluid. As a consequence, the relative work fluctuation diverges unless the output work obeys a rather strict scaling condition, which would be very hard to fulfill in practice. Even under this condition, the fluctuations of work and power do not vanish in the infinite system size limit. Large fluctuations of output work thus constitute inseparable and dominant element in performance of the macroscopic heat engines close to a critical point.

  19. Thermodynamics of climate change: generalized sensitivities

    Directory of Open Access Journals (Sweden)

    V. Lucarini

    2010-10-01

    Full Text Available Using a recent theoretical approach, we study how global warming impacts the thermodynamics of the climate system by performing experiments with a simplified yet Earth-like climate model. The intensity of the Lorenz energy cycle, the Carnot efficiency, the material entropy production, and the degree of irreversibility of the system change monotonically with the CO2 concentration. Moreover, these quantities feature an approximately linear behaviour with respect to the logarithm of the CO2 concentration in a relatively wide range. These generalized sensitivities suggest that the climate becomes less efficient, more irreversible, and features higher entropy production as it becomes warmer, with changes in the latent heat fluxes playing a predominant role. These results may be of help for explaining recent findings obtained with state of the art climate models regarding how increases in CO2 concentration impact the vertical stratification of the tropical and extratropical atmosphere and the position of the storm tracks.

  20. Automatic control of clock duty cycle

    Science.gov (United States)

    Feng, Xiaoxin (Inventor); Roper, Weston (Inventor); Seefeldt, James D. (Inventor)

    2010-01-01

    In general, this disclosure is directed to a duty cycle correction (DCC) circuit that adjusts a falling edge of a clock signal to achieve a desired duty cycle. In some examples, the DCC circuit may generate a pulse in response to a falling edge of an input clock signal, delay the pulse based on a control voltage, adjust the falling edge of the input clock signal based on the delayed pulse to produce an output clock signal, and adjust the control voltage based on the difference between a duty cycle of the output clock signal and a desired duty cycle. Since the DCC circuit adjusts the falling edge of the clock cycle to achieve a desired duty cycle, the DCC may be incorporated into existing PLL control loops that adjust the rising edge of a clock signal without interfering with the operation of such PLL control loops.

  1. Multidimensional evaluation on FR cycle systems

    International Nuclear Information System (INIS)

    Nakai, Ryodai; Fujii, Sumio; Takakuma, Katsuyuki; Katoh, Atsushi; Ono, Kiyoshi; Ohtaki, Akira; Shiotani, Hiroki

    2004-01-01

    This report explains some results of the multidimensional evaluation on various fast reactor cycle system concepts from an interim report of the 2nd phase of ''Feasibility Study on Commercialized FR Cycle System''. This method is designed to give more objective and more quantitative evaluations to clarify commercialized system candidate concepts. Here we brief current evaluation method from the five viewpoints of safety, economy, environment, resource and non-proliferation, with some trial evaluation results for some cycles consist of promising technologies in reactor, core and fuel, reprocessing and fuel manufacture. Moreover, we describe FR cycle deployment scenarios which describe advantages and disadvantages of the cycles from the viewpoints of uranium resource and radioactive waste based on long-term nuclear material mass flow analyses and advantages of the deployment of FR cycle itself from the viewpoints of the comparison with alternative power supplies as well as cost and benefit. (author)

  2. IAEA activities on nuclear fuel cycle 1997

    Energy Technology Data Exchange (ETDEWEB)

    Oi, N [International Atomic Energy Agency, Vienna (Austria). Nuclear Fuel Cycle and Materials Section

    1997-12-01

    The presentation discussing the IAEA activities on nuclear fuel cycle reviews the following issues: organizational charts of IAEA, division of nuclear power and the fuel cycle, nuclear fuel cycle and materials section; 1997 budget estimates; budget trends; the nuclear fuel cycle programme.

  3. IAEA activities on nuclear fuel cycle 1997

    International Nuclear Information System (INIS)

    Oi, N.

    1997-01-01

    The presentation discussing the IAEA activities on nuclear fuel cycle reviews the following issues: organizational charts of IAEA, division of nuclear power and the fuel cycle, nuclear fuel cycle and materials section; 1997 budget estimates; budget trends; the nuclear fuel cycle programme

  4. Fuel cycle related parametric study considering long lived actinide production, decay heat and fuel cycle performances

    International Nuclear Information System (INIS)

    Raepsaet, X.; Damian, F.; Lenain, R.; Lecomte, M.

    2001-01-01

    One of the very attractive HTGR reactor characteristics is its highly versatile and flexible core that can fulfil a wide range of diverse fuel cycles. Based on a GTMHR-600 MWth reactor, analyses of several fuel cycles were carried out without taking into account common fuel particle performance limits (burnup, fast fluence, temperature). These values are, however, indicated in each case. Fuel derived from uranium, thorium and a wide variety of plutonium grades has been considered. Long-lived actinide production and total residual decay heat were evaluated for the various types of fuel. The results presented in this papers provide a comparison of the potential and limits of each fuel cycle and allow to define specific cycles offering lowest actinide production and residual heat associated with a long life cycle. (author)

  5. CO2 cycle

    Science.gov (United States)

    Titus, Timothy N.; Byrne, Shane; Colaprete, Anthony; Forget, Francois; Michaels, Timothy I.; Prettyman, Thomas H.

    2017-01-01

    This chapter discusses the use of models, observations, and laboratory experiments to understand the cycling of CO2 between the atmosphere and seasonal Martian polar caps. This cycle is primarily controlled by the polar heat budget, and thus the emphasis here is on its components, including solar and infrared radiation, the effect of clouds (water- and CO2-ice), atmospheric transport, and subsurface heat conduction. There is a discussion about cap properties including growth and regression rates, albedos and emissivities, grain sizes and dust and/or water-ice contamination, and curious features like cold gas jets and araneiform (spider-shaped) terrain. The nature of the residual south polar cap is discussed as well as its long-term stability and ability to buffer atmospheric pressures. There is also a discussion of the consequences of the CO2 cycle as revealed by the non-condensable gas enrichment observed by Odyssey and modeled by various groups.

  6. International Business Cycle

    Directory of Open Access Journals (Sweden)

    Marek Lubiński

    2007-04-01

    Full Text Available Prime stylized facts of international business cycle theory refer to positive correlation in the cyclical components of important macroeconomic variables across countries. However a number of indicators of business cycle synchronization do not point to clear trends. It can be ascribed to the fact that different forces influence level of business cycle correlation. When investigating into the forces behind the commonness in aggregate fluctuations economic research seems to have pointed in two directions. One strand of the literature examines the idea of common exogenous shocks that affect economies simultaneously. In addition to that economic interdependencies such as trade in goods and services or capital account transactions may serve as the channels through which disturbances spill over across countries.The observed degree of output co movement reflects both the nature of the shocks that have occurred and the degree of economic interdependence. In the periods when common shocks prevail level of synchronization is usually higher than in times of transmission dominance.

  7. Fast Cycled Superconducting Magnet - Connecting hydraulically the Fast Cycled magnet to the cryogenic feed box.

    CERN Multimedia

    Maximilien Brice

    2012-01-01

    Photo 1 : Connecting hydraulically the Fast Cycled magnet to the cryogenic feed box. Patrck Viret and Guy Deferne technicians of TE-MSC-TF in SM18. - Photo 2 : Installation of the Fast Cycled Superconducting Magnet (FCM) to the new cold feed box in Sm18. - Photo 3 : Connecting the powering cables of the FCM to the feed box. - Photo 5/6 : The connections of the Fast Cycled Magnet. Intermediate pieces. - Photo 7 : Hydraulic connections of the Fast Cycle Magnet cable to allow the cooling of the magnet’s conductor ( Cable in conduit type) with supercritical helium. - Photo 8 : Verification of the connection: design versus reality. Guy Deferne and Frederick Rougemont, technicians of TE-MSC-TE in SM18.

  8. [Physiological differences between cycling and running].

    Science.gov (United States)

    Millet, Grégoire

    2009-08-05

    This review compares the differences in systemic responses (VO2max, anaerobic threshold, heart rate and economy) and in underlying mechanisms of adaptation (ventilatory and hemodynamic and neuromuscular responses) between cycling and running. VO2max is specific to the exercise modality. Overall, there is more physiological training transfer from running to cycling than vice-versa. Several other physiological differences between cycling and running are discussed: HR is different between the two activities both for maximal and sub-maximal intensities. The delta efficiency is higher in running. Ventilation is more impaired in cycling than running due to mechanical constraints. Central fatigue and decrease in maximal strength are more important after prolonged exercise in running than in cycling.

  9. Metabolic Interaction between Urea Cycle and Citric Acid Cycle Shunt: A Guided Approach

    Science.gov (United States)

    Pesi, Rossana; Balestri, Francesco; Ipata, Piero L.

    2018-01-01

    This article is a guided pedagogical approach, devoted to postgraduate students specializing in biochemistry, aimed at presenting all single reactions and overall equations leading to the metabolic interaction between ureagenesis and citric acid cycle to be incorporated into a two-three lecture series about the interaction of urea cycle with other…

  10. On Acyclicity of Games with Cycles

    DEFF Research Database (Denmark)

    Andersson, Daniel; Gurvich, Vladimir; Hansen, Thomas Dueholm

    2009-01-01

    We study restricted improvement cycles (ri-cycles) in finite positional n-person games with perfect information modeled by directed graphs (digraphs) that may contain cycles. We obtain criteria of restricted improvement acyclicity (ri-acyclicity) in two cases: for n = 2 and for acyclic digraphs. We...

  11. New insight into regenerated air heat pump cycle

    International Nuclear Information System (INIS)

    Zhang, Chun-Lu; Yuan, Han; Cao, Xiang

    2015-01-01

    Regenerated air (reverse Brayton) cycle has unique potentials in heat pump applications compared to conventional vapor-compression cycles. To better understand the regenerated air heat pump cycle characteristics, a thermodynamic model with new equivalent parameters was developed in this paper. Equivalent temperature ratio and equivalent isentropic efficiency of expander were introduced to represent the effect of regenerator, which made the regenerated air cycle in the same mathematical expressions as the basic air cycle and created an easy way to prove some important features that regenerated air cycle inherits from the basic one. Moreover, we proved in theory that the regenerator does not always improve the air cycle efficiency. Larger temperature ratio and lower effectiveness of regenerator could make the regenerated air cycle even worse than the basic air cycle. Lastly, we found that only under certain conditions the cycle could get remarkable benefits from a well-sized regenerator. These results would enable further study of the regenerated air cycle from a different perspective. - Highlights: • A thermodynamic model for regenerated air heat pump cycle was developed. • Equivalent temperature ratio and equivalent expander efficiency were introduced. • We proved regenerated air cycle can make heating capacity in line with heating load. • We proved the regenerator does not always improve the air cycle efficiency.

  12. Fuel cycle oriented approach

    International Nuclear Information System (INIS)

    Petit, A.

    1987-01-01

    The term fuel cycle oriented approach is currently used to designate two quite different things: the attempt to consider all or part of a national fuel cycle as one material balance area (MBA) or to consider individual MBAs existing in a state while designing a unique safeguards approach for each and applying the principle of nondiscrimination to fuel cycles as a whole, rather than to individual facilities. The merits of such an approach are acceptability by the industry and comparison with the contemplated establishment of long-term criteria. The following points concern the acceptability by the industry: (1) The main interest of the industry is to keep an open international market and therefore, to have effective and efficient safeguards. (2) The main concerns of the industry regarding international safeguards are economic burden, intrusiveness, and discrimination. Answers to these legitimate concerns, which retain the benefits of a fuel cycle oriented approach, are needed. More specifically, the problem of reimbursing the operator the costs that he has incurred for the safeguards must be considered

  13. Empirical solar/stellar cycle simulations

    Directory of Open Access Journals (Sweden)

    Santos Ângela R. G.

    2015-01-01

    Full Text Available As a result of the magnetic cycle, the properties of the solar oscillations vary periodically. With the recent discovery of manifestations of activity cycles in the seismic data of other stars, the understanding of the different contributions to such variations becomes even more important. With this in mind, we built an empirical parameterised model able to reproduce the properties of the sunspot cycle. The resulting simulations can be used to estimate the magnetic-induced frequency shifts.

  14. The nuclear fuel cycle

    International Nuclear Information System (INIS)

    Jones, P.M.S.

    1987-01-01

    This chapter explains the distinction between fissile and fertile materials, examines briefly the processes involved in fuel manufacture and management, describes the alternative nuclear fuel cycles and considers their advantages and disadvantages. Fuel management is usually divided into three stages; the front end stage of production and fabrication, the back end stage which deals with the fuel after it is removed from the reactor (including reprocessing and waste treatment) and the stage in between when the fuel is actually in the reactor. These stages are illustrated and explained in detail. The plutonium fuel cycle and thorium-uranium-233 fuel cycle are explained. The differences between fuels for thermal reactors and fast reactors are explained. (U.K.)

  15. Dynamic Simulations of Advanced Fuel Cycles

    International Nuclear Information System (INIS)

    Piet, Steven J.; Dixon, Brent W.; Jacobson, Jacob J.; Matthern, Gretchen E.; Shropshire, David E.

    2011-01-01

    Years of performing dynamic simulations of advanced nuclear fuel cycle options provide insights into how they could work and how one might transition from the current once-through fuel cycle. This paper summarizes those insights from the context of the 2005 objectives and goals of the U.S. Advanced Fuel Cycle Initiative (AFCI). Our intent is not to compare options, assess options versus those objectives and goals, nor recommend changes to those objectives and goals. Rather, we organize what we have learned from dynamic simulations in the context of the AFCI objectives for waste management, proliferation resistance, uranium utilization, and economics. Thus, we do not merely describe 'lessons learned' from dynamic simulations but attempt to answer the 'so what' question by using this context. The analyses have been performed using the Verifiable Fuel Cycle Simulation of Nuclear Fuel Cycle Dynamics (VISION). We observe that the 2005 objectives and goals do not address many of the inherently dynamic discriminators among advanced fuel cycle options and transitions thereof.

  16. The status of nuclear fuel cycle system analysis for the development of advanced nuclear fuel cycles

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Won Il; Kim, Seong Ki; Lee, Hyo Jik; Chang, Hong Rae; Kwon, Eun Ha; Lee, Yoon Hee; Gao, Fanxing [KAERI, Daejeon (Korea, Republic of)

    2011-11-15

    The system analysis has been used with different system and objectives in various fields. In the nuclear field, the system can be applied from uranium mining to spent fuel reprocessing or disposal which is called the nuclear fuel cycle. The analysis of nuclear fuel cycle can be guideline for development of advanced fuel cycle through integrating and evaluating the technologies. For this purpose, objective approach is essential and modeling and simulation can be useful. In this report, several methods which can be applicable for development of advanced nuclear fuel cycle, such as TRL, simulation and trade analysis were explained with case study

  17. Answering Key Fuel Cycle Questions

    International Nuclear Information System (INIS)

    Piet, S.J.; Dixon, B.W.; Bennett, R.G.; Smith, J.D.; Hill, R.N.

    2004-01-01

    Given the range of fuel cycle goals and criteria, and the wide range of fuel cycle options, how can the set of options eventually be narrowed in a transparent and justifiable fashion? It is impractical to develop all options. We suggest an approach that starts by considering a range of goals for the Advanced Fuel Cycle Initiative (AFCI) and then posits seven questions, such as whether Cs and Sr isotopes should be separated from spent fuel and, if so, what should be done with them. For each question, we consider which of the goals may be relevant to eventually providing answers. The AFCI program has both ''outcome'' and ''process'' goals because it must address both waste already accumulating as well as completing the fuel cycle in connection with advanced nuclear power plant concepts. The outcome objectives are waste geologic repository capacity and cost, energy security and sustainability, proliferation resistance, fuel cycle economics, and safety. The process objectives are rea diness to proceed and adaptability and robustness in the face of uncertainties

  18. Primary water chemistry optimization for extended fuel cycle operation. Results of the 'Duo experimentation' after three cycles

    International Nuclear Information System (INIS)

    Viricel, L.; Andrieu, C.; Segura, J.C.; Rocher, A.; Thomazet, J.; Clinard, M.H.; Dacquait, F.

    2002-01-01

    The primary coolant conditioning in French nuclear power plants is essentially based on the boron-lithium coordinated chemistry, with a target pH of 7.2 at 300 C and a maximum lithium concentration of 2.2 mg/kg. In 1996, EDF 1300 MWe units began operating 18-month fuel cycles, increasing boron concentrations at the beginning of the cycles. Since today the maximum lithium concentration in normal operation is 2.2 mg/kg, extended cycle operation results in a decrease in the pH at the beginning of the cycles, which may possibly lead to deposits in RCS, and particularly on the fuel cladding, and increased dose rates. It has to be noted that today, the fuel assemblies maximum burnup is set at 52 GWd/tU. One solution is to adjust the pH by increasing the lithium content at the beginning of the cycles, which is easy to implement and does not require any modification on the units. Hence, EDF is testing a ''modified'' chemistry regime in the > during 4 fuel cycles, with a maximum authorized lithium content of 3.5 mg/kg at the beginning of the cycles in the Cattenom 2 pilot unit. The Golfech 1 reference unit implements a standard boron-lithium coordination pH 300 7.2. The major goal of the experimentation is to assess the impact of elevated lithium concentrations at the beginning of the cycles on fuel cladding oxide behavior, mass transport and dose rates. This paper presents the results of the first three cycles of the Duo experimentation. (author)

  19. Rapsodie: A closed fuel cycle

    International Nuclear Information System (INIS)

    Levallet, E.H.; Costa, L.; Mougniot, J.C.; Robin, J.

    1977-01-01

    The Fortissimo Version of the core of the RAPSODIE fast reactor produces 40 MWTh. Since its start up in May 1970 in the CEN-CADARACHE its availability has stayed around 85%. Some of the mixed oxyde fuel pins UO 2 - 30% PuO 2 have already reached 150.000 MWd/t. The reprocessing is done in the pilot plant located in the La Hague Center and the plutonium obtained has already been re-used in the reactor. The Rapsodie-Fortissimo cycle is therefore now a closed cycle. This cycle is quite representative of fast reactor cycle characteristics and thus provides a remarkable research and development tool for the study of fabrication, in-reactor performances, transport, storage and reprocessing. These studies concern in particular the evolution of fission products and heavy isotopes content in fuel which controls both reprocessing schemes and intensity of emitted radiations. A program for the analysis of irradiated fuel has been developed either using samples collected all along the cycle, or following the actual reprocessing subassemblies. A set of basic data and calculation models has been established with two objectives: to give a better interpretation of the experimental program on one hand, and to extrapolate these results to the fuel cycle of fast reactors in general on the other hand. The first results have been quite encouraging up to now [fr

  20. Exergy optimization for a novel combination of organic Rankine cycles, Stirling cycle and direct expander turbines

    Science.gov (United States)

    Moghimi, Mahdi; Khosravian, Mohammadreza

    2018-06-01

    In this paper, a novel combination of organic Rankine cycles (ORCs), Stirling cycle and direct expander turbines is modeled and optimized using the genetic algorithm. The Exergy efficiency is considered as an objective function in the genetic algorithm. High efficiency is the main advantage of Stirling cycle, however, it needs nearly isothermal compressor and turbine. Therefore, an argon ORC and a R14 ORC are placed before and after the Striling cycle along with two expander turbines at the end of the line. Each component and cycle of the proposed plant in this article is verified by the previous works available in the literature and good agreement is achieved. The obtained results reveal that 27.98%, 20.86% and 12.90% of the total cold exergy are used by argon ORC, Stirling cycle and R14 ORC, respectively. Therefore, utilization of the Stirling cycle is a good idea for the LNG line cold exergy. The maximum exergy destruction occurs in the heat exchanger after the argon ORC (85.786 kJ/s per one kg/s LNG) due to the wasted cold exergy, which can be used for air conditioning systems in the plant. Finally, it would be shown that the maximum efficiency of the proposed plant is 54.25% and the maximum output power is 355.72 kW.

  1. Exergy optimization for a novel combination of organic Rankine cycles, Stirling cycle and direct expander turbines

    Science.gov (United States)

    Moghimi, Mahdi; Khosravian, Mohammadreza

    2018-01-01

    In this paper, a novel combination of organic Rankine cycles (ORCs), Stirling cycle and direct expander turbines is modeled and optimized using the genetic algorithm. The Exergy efficiency is considered as an objective function in the genetic algorithm. High efficiency is the main advantage of Stirling cycle, however, it needs nearly isothermal compressor and turbine. Therefore, an argon ORC and a R14 ORC are placed before and after the Striling cycle along with two expander turbines at the end of the line. Each component and cycle of the proposed plant in this article is verified by the previous works available in the literature and good agreement is achieved. The obtained results reveal that 27.98%, 20.86% and 12.90% of the total cold exergy are used by argon ORC, Stirling cycle and R14 ORC, respectively. Therefore, utilization of the Stirling cycle is a good idea for the LNG line cold exergy. The maximum exergy destruction occurs in the heat exchanger after the argon ORC (85.786 kJ/s per one kg/s LNG) due to the wasted cold exergy, which can be used for air conditioning systems in the plant. Finally, it would be shown that the maximum efficiency of the proposed plant is 54.25% and the maximum output power is 355.72 kW.

  2. Policy paper no. 1 : Pedestrians and cycling

    Energy Technology Data Exchange (ETDEWEB)

    Zbogar, H. [City of Brampton, ON (Canada)

    2004-06-01

    The City of Brampton's Transportation and Transit Master Plan includes a workable plan to promote walking and cycling facilities in the area. This paper reviewed existing policies, programs and practices in the City of Brampton that pertain to cycling and walking. Walking and cycling issues and trends were also reviewed with reference to the principles that improve the pedestrian and cycling environment, such as safety, security, convenience, continuity, comfort, coherence and attractiveness. The recreation, health and fitness benefits of walking and cycling were also outlined along with transportation, environmental, and economic benefits. The official plan for the city was included with reference to walking and cycling sections in the city. It was noted that effective pathways should be customer driven and respond to the needs of residents. They should also accommodate all uses, including walking, jogging, cycling and in-line skating. Experience of other jurisdictions in Ontario in providing walking and cycling facilities were also reviewed. It was noted that walking and cycling are significant elements of an intermodal transportation system and have a strong bearing on a city's vision for urban street design. 11 refs., 2 tabs., 3 figs.

  3. Developing a Cost Model and Methodology to Estimate Capital Costs for Thermal Energy Storage

    Energy Technology Data Exchange (ETDEWEB)

    Glatzmaier, G.

    2011-12-01

    system leads to higher thermal-to-electric conversion efficiency. However, in a CSP system, higher operating temperature also leads to greater thermal losses. These two effects combine to give an optimal system-level operating temperature that may be less than the upper operating temperature limit of system components. The overall efficiency may be improved by developing materials, power cycles, and system-integration strategies that enable operation at elevated temperature while limiting thermal losses. This is particularly true for the TES system and its components. Meeting the SunShot cost target will require cost and performance improvements in all systems and components within a CSP plant. Solar collector field hardware will need to decrease significantly in cost with no loss in performance and possibly with performance improvements. As higher temperatures are considered for the power block, new working fluids, heat-transfer fluids (HTFs), and storage fluids will all need to be identified to meet these new operating conditions. Figure 1 shows thermodynamic conversion efficiency as a function of temperature for the ideal Carnot cycle and 75% Carnot, which is considered to be the practical efficiency attainable by current power cycles. Current conversion efficiencies for the parabolic trough steam cycle, power tower steam cycle, parabolic dish/Stirling, Ericsson, and air-Brayton/steam Rankine combined cycles are shown at their corresponding operating temperatures. Efficiencies for supercritical steam and carbon dioxide (CO{sub 2}) are also shown for their operating temperature ranges.

  4. Exploring cycle crash characteristics in Malaysia

    Directory of Open Access Journals (Sweden)

    Hamzah A.

    2017-01-01

    Full Text Available This paper explains the cycle road crash trend, characteristics and injuries in Malaysia. It analyses the in-depth road crash investigation data collected by the Royal Malaysian Police which was made available to MIROS crash database. Fatality data was utilized due to its consistency. Cycle casualties reflected a continual downward pattern for year 2009 to 2014 in which the number of cycle crash involvement reduced by 49% and fatalities dropped by 42%. Among the prevalent factors of cycle fatalities are >60 age group, federal and state roads and straight road sections, rural and small towns, evening peak hours, and mainly involving cars and motorcycles. It is hoped that all these information would spark interests to improve cycle safety in Malaysia.

  5. Fuel cycle centres

    International Nuclear Information System (INIS)

    Hagen, M.

    1977-01-01

    The concept of co-locating and integrating fuel cycle facilities at one site is discussed. This concept offers considerable advantages, especially in minimizing the amount of radioactive material to be transported on public roads. Safeguards and physical protection as relating to such an integrated system of facilities are analysed in detail, also industrial and commercial questions. An overall risk-benefit evaluation turns out to be in favour of fuel cycle centres. These centres seem to be specifically attractive with regard to the back end of the fuel cycle, including on-site disposal of radioactive wastes. The respective German approach is presented as an example. Special emphasis is given to the site selection procedures in this case. Time scale and cost for the implementation of this concept are important factors to be looked at. Since participation of governmental institutions in these centres seems to be indispensable their respective roles as compared to industry must be clearly defined. The idea of adjusting fuel cycle centres to regional rather than national use might be an attractive option, depending on the specific parameters in the region, though results of existing multinational ventures are inconclusive in this respect. Major difficulties might be expected e.g. because of different national safety regulations and standards as well as commercial conditions among partner countries. Public acceptance in the host country seems to be another stumbling block for the realization of this type of multinational facilities

  6. Role of the seasonal cycle in coupling climate and carbon cycling in subanartic zone

    CSIR Research Space (South Africa)

    Monteiro, PMS

    2010-08-01

    Full Text Available There is increasing evidence in the Southern Ocean that mesoscales and seasonal scales play an important role in the coupling of ocean carbon cycling and climate. The seasonal cycle is one of the strongest modes of variability in different...

  7. Measuring business cycles in The Netherlands, 1815-1913: a comparison of business cycle dating methods

    OpenAIRE

    Bonenkamp, Jan; Jacobs, Jan; Kuper, Gerard H.

    2001-01-01

    This paper compares different business cycle dating methods both on theoretical and practical grounds. Weighing the pros and cons of these methods, and based on a new data set for The Netherlands in the nineteenth century, we finally recommend two preferred methods for doing further business cycle research on the economy of the Netherlands. With respect to the methods for finding turning points in the level of economic activity, the classical cycle definition, we prefer the Bry-Boschan algori...

  8. Introducing advanced nuclear fuel cycles in Canada

    International Nuclear Information System (INIS)

    Duret, M.F.

    1978-05-01

    The ability of several different advanced fuel cycles to provide energy for a range of energy growth scenarios has been examined for a few special situations of interest in Canada. Plutonium generated from the CANDU-PHW operating on natural uranium is used to initiate advanced fuel cycles in the year 2000. The four fuel cycles compared are: 1) natural uranium in the CANDU-PHW; 2) high burnup thorium cycle in the CANDU-PHW; 3) self-sufficient thorium cycle in the CANDU-PHW; 4) plutonium-uranium cycle in a fast breeder reactor. The general features of the results are quite clear. While any plutonium generated prior to the introduction of the advanced fuel cycle remains, system requirements for natural uranium for each of the advanced fuel cycles are the same and are governed by the rate at which plants operating on natural uranium can be retired. When the accumulated plutonium inventory has been entirely used, natural uranium is again required to provide inventory for the advanced fuel cycle reactors. The time interval during which no uranium is required varies only from about 25 to 40 years for both thorium cycles, depending primarily on the energy growth rate. The breeder does not require the entire plutonium inventory produced and so would call for less processing of fuel from the PHW reactors. (author)

  9. 40 CFR 94.105 - Duty cycles.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Duty cycles. 94.105 Section 94.105... EMISSIONS FROM MARINE COMPRESSION-IGNITION ENGINES Test Procedures § 94.105 Duty cycles. (a) Overview. For....8(e), engines shall be tested using the appropriate duty cycles described in this section. (b...

  10. When Product Life Cycle Meets Customer Activity Cycle

    DEFF Research Database (Denmark)

    Tan, Adrian Ronald

    2007-01-01

    Manufacturing companies have traditionally focused their efforts on designing, developing and producing products to offer on the market. Today global competition and demands for greater company responsibility of products throughout their entire life cycle are driving manufacturing companies to sh...

  11. Carbon cycle makeover

    DEFF Research Database (Denmark)

    Canfield, Donald Eugene; Kump, Lee R.

    2013-01-01

    remaining in sediments after respiration leave a residual of oxygen in the atmosphere. The source of oxygen to the atmosphere represented by organic matter burial is balanced by oxygen sinks associated with rock weathering and chemical reaction with volcanic gases. This is the long-term carbon and oxygen...... geochemical cycle. But Earth is an old planet, and oxygen levels have changed through time (2). On page 540 of this issue, Schrag et al. (3) challenge the most commonly used geochemical approach to assess long-term changes in the coupled oxygen and carbon cycles....

  12. High performance integrated solar combined cycles with minimum modifications to the combined cycle power plant design

    International Nuclear Information System (INIS)

    Manente, Giovanni

    2016-01-01

    Highlights: • Off-design model of a 390 MW_e three pressure combined cycle developed and validated. • The off-design model is used to evaluate different hybridization schemes with solar. • Power boosting and fuel saving with different design modifications are considered. • Maximum solar share of total electricity is only 1% with the existing equipment. • The maximum incremental solar radiation-to-electrical efficiency approaches 29%. - Abstract: The integration of solar energy into natural gas combined cycles has been successfully demonstrated in several integrated solar combined cycles since the beginning of this decade in many countries. There are many motivations that drive investments on integrated solar combined cycles which are primarily the repowering of existing power plants, the compliance with more severe environmental laws on emissions and the mitigation of risks associated with large solar projects. Integrated solar combined cycles are usually developed as brownfield facilities by retrofitting existing natural gas combined cycles and keeping the existing equipment to minimize costs. In this work a detailed off-design model of a 390 MW_e three pressure level natural gas combined cycle is built to evaluate different integration schemes of solar energy which either keep the equipment of the combined cycle unchanged or include new equipment (steam turbine, heat recovery steam generator). Both power boosting and fuel saving operation strategies are analyzed in the search for the highest annual efficiency and solar share. Results show that the maximum incremental power output from solar at design solar irradiance is limited to 19 MW_e without modifications to the existing equipment. Higher values are attainable only including a larger steam turbine. High solar radiation-to-electrical efficiencies in the range 24–29% can be achieved in the integrated solar combined cycle depending on solar share and extension of tube banks in the heat recovery

  13. Actinide production in different HTR-fuel cycle concepts

    International Nuclear Information System (INIS)

    Filges, D.; Hecker, R.; Mirza, N.; Rueckert, M.

    1978-01-01

    At the 'Institut fuer Reaktorentwicklung der Kernforschungsanlage Juelich' the production of α-activities in the following HTR-OTTO cycle concepts were studied: 1. standard HTR cycle (U-Th); 2. low enriched HTR cycle (U-Pu); 3. near breeder HTR cycle (U-Th); 4. combined system (conventional and near breeder HTR). The production of α-activity in HTR Uranium-Thorium fuel cycles has been investigated and compared with the standard LWR cycles. The production of α-activity in HTR Uranium-Thorium fuel cycles has been investigated and compared with the standard LWR cycles. The calculations were performed by the short depletion code KASCO and the well-known ORIGEN program

  14. Dual Pressure versus Hybrid Recuperation in an Integrated Solid Oxide Fuel Cell Cycle – Steam Cycle

    DEFF Research Database (Denmark)

    Rokni, Masoud

    2014-01-01

    A SOFC (solid oxide fuel cell) cycle running on natural gas was integrated with a ST (steam turbine) cycle. The fuel is desulfurized and pre-reformed before entering the SOFC. A burner was used to combust the remaining fuel after the SOFC stacks. The off-gases from the burner were used to produce...... pressure configuration steam cycle combined with SOFC cycle (SOFC-ST) was new and has not been studied previously. In each of the configuration, a hybrid recuperator was used to recovery the remaining energy of the off-gases after the HRSG. Thus, four different plants system setups were compared to each...... other to reveal the most superior concept with respect to plant efficiency and power. It was found that in order to increase the plant efficiency considerably, it was enough to use a single pressure with a hybrid recuperator instead of a dual pressure Rankine cycle....

  15. Cell cycle gene expression under clinorotation

    Science.gov (United States)

    Artemenko, Olga

    2016-07-01

    Cyclins and cyclin-dependent kinase (CDK) are main regulators of the cell cycle of eukaryotes. It's assumes a significant change of their level in cells under microgravity conditions and by other physical factors actions. The clinorotation use enables to determine the influence of gravity on simulated events in the cell during the cell cycle - exit from the state of quiet stage and promotion presynthetic phase (G1) and DNA synthesis phase (S) of the cell cycle. For the clinorotation effect study on cell proliferation activity is the necessary studies of molecular mechanisms of cell cycle regulation and development of plants under altered gravity condition. The activity of cyclin D, which is responsible for the events of the cell cycle in presynthetic phase can be controlled by the action of endogenous as well as exogenous factors, but clinorotation is one of the factors that influence on genes expression that regulate the cell cycle.These data can be used as a model for further research of cyclin - CDK complex for study of molecular mechanisms regulation of growth and proliferation. In this investigation we tried to summarize and analyze known literature and own data we obtained relatively the main regulators of the cell cycle in altered gravity condition.

  16. Teaching the Rock Cycle with Ease.

    Science.gov (United States)

    Bereki, Debra

    2000-01-01

    Describes a hands-on lesson for teaching high school students the concept of the rock cycle using sedimentary, metamorphic, and igneous rocks. Students use a rock cycle diagram to identify pairs of rocks. From the rock cycle, students explain on paper how their first rock became the second rock and vice versa. (PVD)

  17. 10 CFR 436.19 - Life cycle costs.

    Science.gov (United States)

    2010-01-01

    ... operation and maintenance costs: (c) Replacement costs less salvage costs of replaced building systems; and... 10 Energy 3 2010-01-01 2010-01-01 false Life cycle costs. 436.19 Section 436.19 Energy DEPARTMENT... Procedures for Life Cycle Cost Analyses § 436.19 Life cycle costs. Life cycle costs are the sum of the...

  18. Plant Characteristics of an Integrated Solid Oxide Fuel Cell Cycle and a Steam Cycle

    DEFF Research Database (Denmark)

    Rokni, Masoud

    2010-01-01

    Plant characteristics of a system containing a solid oxide fuel cell (SOFC) cycle on the top of a Rankine cycle were investigated. Natural gas (NG) was used as the fuel for the plant. A desulfurization reactor removes the sulfur content in the fuel, while a pre-reformer broke down the heavier...... recovery steam generator (HRSG). The remaining energy of the off-gases was recycled back to the topping cycle for further utilization. Several parameter studies were carried out to investigate the sensitivity of the suggested plant. It was shown that the operation temperature of the desulfurization unit...

  19. Enhancing Low-Grade Thermal Energy Recovery in a Thermally Regenerative Ammonia Battery Using Elevated Temperatures

    KAUST Repository

    Zhang, Fang; LaBarge, Nicole; Yang, Wulin; Liu, Jia; Logan, Bruce E.

    2015-01-01

    ). The energy density varied with temperature and discharge rates, with a maximum of 650 Whm-3 at a discharge energy efficiency of 54% and a temperature of 37°C. The energy efficiency calculated with chemical process simulation software indicated a Carnot

  20. Nature's third cycle a story of sunspots

    CERN Document Server

    Choudhuri, Arnab Rai

    2015-01-01

    The cycle of day and night and the cycle of seasons are two familiar natural cycles around which many human activities are organized. But is there a third natural cycle of importance for us humans? On 13 March 1989, six million people in Canada went without electricity for many hours: a large explosion on the sun was discovered as the cause of this blackout. Such explosions occur above sunspots, dark features on the surface of the Sun that have been observed through telescopes since the time of Galileo. The number of sunspots has been found to wax and wane over a period of 11 years. Although this cycle was discovered less than two centuries ago, it is becoming increasingly important for us as human society becomes more dependent on technology. For nearly a century after its discovery, the cause of the sunspot cycle remained completely shrouded in mystery. The 1908 discovery of strong magnetic fields in sunspots made it clear that the 11-year cycle is the magnetic cycle of the sun. It is only during the last ...

  1. Solar cycles and climate variations

    International Nuclear Information System (INIS)

    Chistyakov, V.F.

    1990-01-01

    Climate oscillations with 100-, 200- and 300-year periods are positively correlated with solar activity oscillations: the higher is solar activity the warmer is climate. According to geological data (varved clays) it is determined, that length of cycles has decreased from 23.4 up to 11 years during latter 2.5 billion years. 12-year cycles occurred during the great glaciation periods, while 10-year cycles occurred during interglaciation periods. It is suggested, that these oscillations are related with variations of the solar activity and luminescence

  2. Study for Determining the Testing Condition of Compressor and Turbine System

    International Nuclear Information System (INIS)

    Sri Sudadiyo

    2009-01-01

    Study for Determining the Testing Condition of Compressor and Turbine System. From the viewpoint of energy system and environment, the concept for nuclear reactors of the generation IV have good potential for electricity and heat generation devices in producing hydrogen. These gas cooled nuclear reactors employ turbine cycle in transferring the heat. To analyses that coolant system, it is proposed a model of compressor and turbine system with power 3 kW. The used working fluid was hydrogen that be burnt with air within combustion chamber, then be expanded through a turbine for getting shaft work that will be used in driving compressor and generator. This study is aimed to determine the optimum testing conditions of gas turbine system. The used method is by applying the balance equations of energy, mass, and momentum. Gas turbine and compressor were placed at the single shaft, in which it was about 55 percent of power output for running the compressor. Under the testing condition for the speed of 20305 rpm, it was obtained thermal efficiency of the turbine cycle approximate 18 % (equal to the Carnot efficiency ratio 65 %), so that it is properly developed for the development of nuclear power installation in supporting the electricity energy demand and it will be very promising for the future facility. (author)

  3. Rabi model as a quantum coherent heat engine: From quantum biology to superconducting circuits

    Science.gov (United States)

    Altintas, Ferdi; Hardal, Ali Ü. C.; Müstecaplıoǧlu, Özgür E.

    2015-02-01

    We propose a multilevel quantum heat engine with a working medium described by a generalized Rabi model which consists of a two-level system coupled to a single-mode bosonic field. The model is constructed to be a continuum limit of a quantum biological description of light-harvesting complexes so that it can amplify quantum coherence by a mechanism which is a quantum analog of classical Huygens clocks. The engine operates in a quantum Otto cycle where the working medium is coupled to classical heat baths in the isochoric processes of the four-stroke cycle, while either the coupling strength or the resonance frequency is changed in the adiabatic stages. We found that such an engine can produce work with an efficiency close to the Carnot bound when it operates at low temperatures and in the ultrastrong-coupling regime. The interplay of the effects of quantum coherence and quantum correlations on the engine performance is discussed in terms of second-order coherence, quantum mutual information, and the logarithmic negativity of entanglement. We point out that the proposed quantum Otto engine can be implemented experimentally with modern circuit quantum electrodynamic systems where flux qubits can be coupled ultrastrongly to superconducting transmission-line resonators.

  4. Second law-based thermodynamic analysis of water-lithium bromide absorption refrigeration system

    Energy Technology Data Exchange (ETDEWEB)

    Kilic, Muhsin [Department of Mechanical Engineering, Faculty of Engineering and Architecture, Uludag University, TR 16059, Bursa (Turkey)]. E-mail: mkilic@uludag.edu.tr; Kaynakli, Omer [Department of Mechanical Engineering, Faculty of Engineering and Architecture, Uludag University, TR 16059, Bursa (Turkey)

    2007-08-15

    In this study, the first and the second law of thermodynamics are used to analyze the performance of a single-stage water-lithium bromide absorption refrigeration system (ARS) when some working parameters are varied. A mathematical model based on the exergy method is introduced to evaluate the system performance, exergy loss of each component and total exergy loss of all the system components. Parameters connected with performance of the cycle-circulation ratio (CR), coefficient of performance (COP), Carnot coefficient of performance (COP{sub c} ), exergetic efficiency ({xi}) and efficiency ratio ({tau})-are calculated from the thermodynamic properties of the working fluids at various operating conditions. Using the developed model, the effect of main system temperatures on the performance parameters of the system, irreversibilities in the thermal process and non-dimensional exergy loss of each component are analyzed in detail. The results show that the performance of the ARS increases with increasing generator and evaporator temperatures, but decreases with increasing condenser and absorber temperatures. Exergy losses in the expansion valves, pump and heat exchangers, especially refrigerant heat exchanger, are small compared to other components. The highest exergy loss occurs in the generator regardless of operating conditions, which therefore makes the generator the most important component of the cycle.

  5. Second law-based thermodynamic analysis of water-lithium bromide absorption refrigeration system

    International Nuclear Information System (INIS)

    Kilic, Muhsin; Kaynakli, Omer

    2007-01-01

    In this study, the first and the second law of thermodynamics are used to analyze the performance of a single-stage water-lithium bromide absorption refrigeration system (ARS) when some working parameters are varied. A mathematical model based on the exergy method is introduced to evaluate the system performance, exergy loss of each component and total exergy loss of all the system components. Parameters connected with performance of the cycle-circulation ratio (CR), coefficient of performance (COP), Carnot coefficient of performance (COP c ), exergetic efficiency (ξ) and efficiency ratio (τ)-are calculated from the thermodynamic properties of the working fluids at various operating conditions. Using the developed model, the effect of main system temperatures on the performance parameters of the system, irreversibilities in the thermal process and non-dimensional exergy loss of each component are analyzed in detail. The results show that the performance of the ARS increases with increasing generator and evaporator temperatures, but decreases with increasing condenser and absorber temperatures. Exergy losses in the expansion valves, pump and heat exchangers, especially refrigerant heat exchanger, are small compared to other components. The highest exergy loss occurs in the generator regardless of operating conditions, which therefore makes the generator the most important component of the cycle

  6. 40 CFR 89.410 - Engine test cycle.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Engine test cycle. 89.410 Section 89... Procedures § 89.410 Engine test cycle. (a) Emissions shall be measured using one of the test cycles specified...) through (a)(4) of this section. These cycles shall be used to test engines on a dynamometer. (1) The 8...

  7. CHOOSING DRIVING CYCLE OF HYBRID VEHICLE

    Directory of Open Access Journals (Sweden)

    A. Vorona

    2011-01-01

    Full Text Available The analysis of existing driving cycles was performed. After comparing some of the cycles, one specific driving cycle was selected for the hybrid vehicle as the most reliable in representing the real moving of the vehicle in operating conditions and which may be reproduced at experimental tests at the modeling roller stand.

  8. Round and Round the Water Cycle

    Science.gov (United States)

    Bradley, Barbara A.

    2017-01-01

    Children enjoy water play, and kindergarten children can learn about the water cycle. Teachers are already introducing elements of the water cycle when discussing weather and bodies of water. The water cycle also can be a springboard for teaching children about plants and animals and the importance of water for sustaining life and shaping our…

  9. Generalized formulation of free energy and application to photosynthesis

    Science.gov (United States)

    Zhang, Hwe Ik; Choi, M. Y.

    2018-03-01

    The origin of free energy on the earth is solar radiation. However, the amount of free energy it contains has seldom been investigated, because the free energy concept was believed to be inappropriate for a system of photons. Instead, the origin of free energy has been sought in the process of photosynthesis, imposing a limit of conversion given by the Carnot efficiency. Here we present a general formulation, capable of not only assessing accurately the available amount of free energy in the photon gas but also explaining the primary photosynthetic process more succinctly. In this formulation, the problem of "photosynthetic conversion of the internal energy of photons into the free energy of chlorophyll" is replaced by simple "free energy transduction" between the photons and chlorophyll. An analytic expression for the photosynthetic efficiency is derived and shown to deviate from the Carnot efficiency. Some predictions verifiable possibly by observation are also suggested.

  10. A New Perspective on Thermodynamics

    CERN Document Server

    Lavenda, Bernard H

    2010-01-01

    Dr. Bernard H. Lavenda has written A New Perspective on Thermodynamics to combine an old look at thermodynamics with a new foundation. The book presents a historical perspective, which unravels the current presentation of thermodynamics found in standard texts, and which emphasizes the fundamental role that Carnot played in the development of thermodynamics. A New Perspective on Thermodynamics will: Chronologically unravel the development of the principles of thermodynamics and how they were conceived by their discoverers Bring the theory of thermodynamics up to the present time and indicate areas of further development with the union of information theory and the theory of means and their inequalities. New areas include nonextensive thermodynamics, the thermodynamics of coding theory, multifractals, and strange attractors. Reintroduce important, yet nearly forgotten, teachings of N.L. Sardi Carnot Highlight conceptual flaws in timely topics such as endoreversible engines, finite-time thermodynamics, geometri...

  11. Quantum dot as spin current generator and energy harvester

    Science.gov (United States)

    Szukiewicz, Barbara; Wysokiński, Karol I.

    2015-05-01

    The thermoelectric transport in the device composed of a central nanoscopic system in contact with two electrodes and subject to the external magnetic field of Zeeman type has been studied. The device can support pure spin current in the electrodes and may serve as a source of the temperature induced spin currents with possible applications in spintronics. The system may also be used as an energy harvester. We calculate its thermodynamic efficiency η and the power output P. The maximal efficiency of the device reaches the Carnot value when the device works reversibly but with the vanishing power. The interactions between carriers diminish the maximal efficiency of the device, which under the constant load drops well below the Carnot limit but may exceed the Curzon-Ahlborn limit. While the effect of intradot Coulomb repulsion on η depends on the parameters, the interdot/interlevel interaction strongly diminishes the device efficiency.

  12. High temperature absorption compression heat pump for industrial waste heat

    DEFF Research Database (Denmark)

    Reinholdt, Lars; Horntvedt, B.; Nordtvedt, S. R.

    2016-01-01

    Heat pumps are currently receiving extensive interest because they may be able to support the integration of large shares of fluctuating electricity production based on renewable sources, and they have the potential for the utilization of low temperature waste heat from industry. In most industries......, the needed temperature levels often range from 100°C and up, but until now, it has been quite difficult to find heat pump technologies that reach this level, and thereby opening up the large-scale heat recovery in the industry. Absorption compression heat pumps can reach temperatures above 100°C......, and they have proved themselves a very efficient and reliable technology for applications that have large temperature changes on the heat sink and/or heat source. The concept of Carnot and Lorenz efficiency and its use in the analysis of system integration is shown. A 1.25 MW system having a Carnot efficiency...

  13. The uranium-plutonium breeder reactor fuel cycle

    International Nuclear Information System (INIS)

    Salmon, A.; Allardice, R.H.

    1979-01-01

    All power-producing systems have an associated fuel cycle covering the history of the fuel from its source to its eventual sink. Most, if not all, of the processes of extraction, preparation, generation, reprocessing, waste treatment and transportation are involved. With thermal nuclear reactors more than one fuel cycle is possible, however it is probable that the uranium-plutonium fuel cycle will become predominant; in this cycle the fuel is mined, usually enriched, fabricated, used and then reprocessed. The useful components of the fuel, the uranium and the plutonium, are then available for further use, the waste products are treated and disposed of safely. This particular thermal reactor fuel cycle is essential if the fast breeder reactor (FBR) using plutonium as its major fuel is to be used in a power-producing system, because it provides the necessary initial plutonium to get the system started. In this paper the authors only consider the FBR using plutonium as its major fuel, at present it is the type envisaged in all, current national plans for FBR power systems. The corresponding fuel cycle, the uranium-plutonium breeder reactor fuel cycle, is basically the same as the thermal reactor fuel cycle - the fuel is used and then reprocessed to separate the useful components from the waste products, the useful uranium and plutonium are used again and the waste disposed of safely. However the details of the cycle are significantly different from those of the thermal reactor cycle. (Auth.)

  14. Cycle-by-cycle exhaust temperature monitoring for detection of misfiring and combustion instability in reciprocating natural gas engines

    Energy Technology Data Exchange (ETDEWEB)

    Gardiner, D.P. [Nexum Research Corp., Kingston, ON (Canada); Bardon, M.F. [Royal Military Coll. of Canada, Kingston, ON (Canada). Dept. of Mechanical Engineering

    2007-07-01

    The effectiveness of a cycle-by-cycle exhaust temperature monitoring system on engines operating at or near their fully rate load capacity was examined. Tests were conducted on stationary industrial natural gas engines. The study evaluated the monitoring system's ability to detect isolated single misfires, as well as combustion instability during misfire-free operations when the air/fuel ratio of the engine was adjusted to progressively lower settings. The combustion instability level of the engines was quantified by determining the relative variability of the groups of consecutive cycles. The coefficient of variation of indicated mean effective pressure (COV of IMEP) was used to examine cyclic variability. A combustion instability index was used to quantify cyclic variability with cycle-by-cycle exhaust temperature monitoring. Two engines were tested, notably a Cummins QSK 19G turbocharged natural gas engine; and a Waukesha VHP L5790G industrial natural gas engine. The tests demonstrated that cycle-by-cycle exhaust temperature monitoring system was capable of detecting misfiring and combustion instabilities in natural gas engines. 6 refs., 9 figs.

  15. Origins of the supercontinent cycle

    Directory of Open Access Journals (Sweden)

    R. Damian Nance

    2013-07-01

    Full Text Available The supercontinent cycle, by which Earth history is seen as having been punctuated by the episodic assembly and breakup of supercontinents, has influenced the rock record more than any other geologic phenomena, and its recognition is arguably the most important advance in Earth Science since plate tectonics. It documents fundamental aspects of the planet's interior dynamics and has charted the course of Earth's tectonic, climatic and biogeochemical evolution for billions of years. But while the widespread realization of the importance of supercontinents in Earth history is a relatively recent development, the supercontinent cycle was first proposed thirty years ago and episodicity in tectonic processes was recognized long before plate tectonics provided a potential explanation for its occurrence. With interest in the supercontinent cycle gaining momentum and the literature expanding rapidly, it is instructive to recall the historical context from which the concept developed. Here we examine the supercontinent cycle from this perspective by tracing its development from the early recognition of long-term episodicity in tectonic processes, through the identification of tectonic cycles following the advent of plate tectonics, to the first realization that these phenomena were the manifestation of episodic supercontinent assembly and breakup.

  16. Fuel cycles

    International Nuclear Information System (INIS)

    Hawley, N.J.

    1983-05-01

    AECL publications, from the open literature, on fuels and fuel cycles used in CANDU reactors are listed in this bibliography. The accompanying index is by subject. The bibliography will be brought up to date periodically

  17. Reporting in vitro fertilization cycles to the Society for Assisted Reproductive Technology database: where have all the cycles gone?

    Science.gov (United States)

    Kulak, David; Jindal, Sangita K; Oh, Cheongeun; Morelli, Sara S; Kratka, Scott; McGovern, Peter G

    2016-04-01

    To assess the relationship between live birth rates (LBRs) and the incidence of under-reported cycles by IVF clinics. Cohort study. Not applicable. All patients undergoing IVF cycles in the aforementioned clinics. Not applicable. The reporting percentage (RP), defined as number of cycles with reported pregnancy rates divided by total cycles performed. Results from cryopreservation cycles are only presented by SART if an embryo transfer occurs. Thus, RP decreases as incidence of embryo or oocyte banking cycles increases. The LBRs in women aged cycles than the median. In clinics with very low RP, the cycles that are reported have higher success rates. Regardless of intent, the reduction of reported data to SART makes it increasingly difficult for clinicians and patients to accurately assess a clinic's success rates. Copyright © 2016 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

  18. The glutamate/GABA-glutamine cycle

    DEFF Research Database (Denmark)

    Bak, Lasse K; Schousboe, Arne; Waagepetersen, Helle S

    2006-01-01

    Neurons are metabolically handicapped in the sense that they are not able to perform de novo synthesis of neurotransmitter glutamate and gamma-aminobutyric acid (GABA) from glucose. A metabolite shuttle known as the glutamate/GABA-glutamine cycle describes the release of neurotransmitter glutamate...... or GABA from neurons and subsequent uptake into astrocytes. In return, astrocytes release glutamine to be taken up into neurons for use as neurotransmitter precursor. In this review, the basic properties of the glutamate/GABA-glutamine cycle will be discussed, including aspects of transport and metabolism...... of intercellular transfer of ammonia produced in neurons (when glutamine is deamidated to glutamate) and utilized in astrocytes (for amidation of glutamate) when the glutamate/GABA-glutamine cycle is operating. A main objective of this review is to endorse the view that the glutamate/GABA-glutamine cycle must...

  19. Nitrogen Cycle Ninja, A Teaching Exercise.

    Science.gov (United States)

    Raun, William R.; And Others

    1997-01-01

    Assesses the effectiveness of using pop quizzes and rewards to improve student retention of the nitrogen cycle. Students able to diagram the N cycle on pop quizzes were rewarded with special cards that included the N cycle. These cards could then be used on subsequent tests in place of memory alone. Six of 11 students tested three months later…

  20. Does It Have a Life Cycle?

    Science.gov (United States)

    Keeley, Page

    2010-01-01

    If life continues from generation to generation, then all plants and animals must go through a life cycle, even though it may be different from organism to organism. Is this what students have "learned," or do they have their own private conceptions about life cycles? The formative assessment probe "Does It Have a Life Cycle?" reveals some…

  1. Introducing Life Cycle Impact Assessment

    DEFF Research Database (Denmark)

    Hauschild, Michael Zwicky; Huijbregts, Mark AJ

    2015-01-01

    This chapter serves as an introduction to the presentation of the many aspects of life cycle impact assessment (LCIA) in this volume of the book series ‘LCA Compendium’. It starts with a brief historical overview of the development of life cycle impact assessment driven by numerous national LCIA...... methodology projects and presents the international scientific discussions and methodological consensus attempts in consecutive working groups under the auspices of the Society of Environmental Toxicology and Chemistry (SETAC) as well as the UNEP/ SETAC Life Cycle Initiative, and the (almost) parallel...

  2. Plutonium re-cycle in HTR

    Energy Technology Data Exchange (ETDEWEB)

    Desoisa, J. A.

    1974-03-15

    The study of plutonium cycles in HTRs using reprocessed plutonium from Magnox and AGR fuel cycles has shown that full core plutonium/uranium loadings are in general not feasible, burn-up is limited due the need for lower loadings of plutonium to meet reload core reactivity limits, on-line refueling is not practicable due to the need for higher burnable poison loadings, and low conversion rates in the plutonium-uranium cycles cannot be mitigated by axial loading schemes so that fissile make-up is needed if HTR plutonium recycle is desired.

  3. 40 CFR 90.410 - Engine test cycle.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Engine test cycle. 90.410 Section 90... Procedures § 90.410 Engine test cycle. (a) Follow the appropriate 6-mode test cycle for Class I, I-B and II engines and 2-mode test cycle for Class I-A, III, IV, and V engines when testing spark-ignition engines...

  4. Aromatase inhibitors in stimulated IVF cycles

    DEFF Research Database (Denmark)

    Papanikolaou, Evangelos G; Polyzos, Nikolaos P; Al Humaidan, Peter Samir Heskjær

    2011-01-01

    are available regarding their efficacy in IVF stimulated cycles. Current available evidence support that letrozole may have a promising role in stimulated IVF cycles, either when administered during the follicular phase for ovarian stimulation. Especially for women with poor ovarian response, letrozole appears...... to have the potential to increase clinical pregnancy rates when combined with gonadotropins, whereas at the same time reduces the total gonadotropin dose required for ovarian stimulation. However, given that in all of the trials letrozole has been administered in GnRH antagonist cycles, it is intriguing...... to test in the future how it may perform when used in GnRH agonist cycles. Finally administration of letrozole during luteal phase in IVF cycles offers another treatment modality for patients at high risk for OHSS taking into account that it drastically reduces estradiol levels....

  5. Supermarket Defrost Cycles As Flexible Reserve

    DEFF Research Database (Denmark)

    Pedersen, Rasmus; Sloth, Christoffer; Wisniewski, Rafal

    2015-01-01

    This work analyses how supermarket defrost cycles can be used as flexible reserve in a smart grid context. The consumption flexibility originates from being able to shift defrost cycles in time, while adhering to the underlying refrigeration systems constraints. It is shown how this time...... constrained behavior can be modeled and used by a defrost planner to optimally schedule defrost start times for several defrost cycles, according to electricity price. Because the defrost planning problem is a boolean programming problem a method of relaxing it is proposed. While the relaxed problem requires...... less computational effort, convexity is dependent on properties of the price signal. Simulation study show that the optimal planning strategy can reduce cost of defrost cycles with 31.7%, compared to a current strategy of executing all defrost cycles at the same time each day. Copyright ©2015 by IEEE...

  6. Plutonium in an enduring fuel cycle

    International Nuclear Information System (INIS)

    Pillay, K.K.S.

    1998-05-01

    Nuclear fuel cycles evolved over the past five decades have allowed many nations of the world to enjoy the benefits of nuclear energy, while contributing to the sustainable consumption of the world's energy resources. The nuclear fuel cycle for energy production suffered many traumas since the 1970s because of perceived risks of proliferation of nuclear weapons. However, the experience of the past five decades has shown that the world community is committed to safeguarding all fissile materials and continuing the use of nuclear energy resources. Decisions of a few nations to discard spent nuclear fuels in geologic formations are contrary to the goals of an enduring nuclear fuel cycle and sustainable development being pursued by the world community. The maintenance of an enduring nuclear fuel cycle is dependent on sensible management of all the resources of the fuel cycle, including spent fuels

  7. Emissions from photovoltaic life cycles

    NARCIS (Netherlands)

    Fthenakis, V.M.; Kim, H.C.; Alsema, E.A.|info:eu-repo/dai/nl/073416258

    2008-01-01

    Photovoltaic (PV) technologies have shown remarkable progress recently in terms of annual production capacity and life cycle environmental performances, which necessitate timely updates of environmental indicators. Based on PV production data of 2004–2006, this study presents the life-cycle

  8. National Urea Cycle Disorders Foundation

    Science.gov (United States)

    ... urea cycle disorders. Donate Now To End Urea Cycle Disorders © 2005-2017 NUCDF. All rights reserved. This site may be freely linked to but not copied or duplicated in any fashion without the Foundation's consent. Make A Donation in ...

  9. Nuclear-fuel-cycle optimization: methods and modelling techniques

    International Nuclear Information System (INIS)

    Silvennoinen, P.

    1982-01-01

    This book present methods applicable to analyzing fuel-cycle logistics and optimization as well as in evaluating the economics of different reactor strategies. After an introduction to the phases of a fuel cycle, uranium cost trends are assessed in a global perspective. Subsequent chapters deal with the fuel-cycle problems faced by a power utility. The fuel-cycle models cover the entire cycle from the supply of uranium to the disposition of spent fuel. The chapter headings are: Nuclear Fuel Cycle, Uranium Supply and Demand, Basic Model of the LWR (light water reactor) Fuel Cycle, Resolution of Uncertainties, Assessment of Proliferation Risks, Multigoal Optimization, Generalized Fuel-Cycle Models, Reactor Strategy Calculations, and Interface with Energy Strategies. 47 references, 34 figures, 25 tables

  10. Efficiency of an air-cooled thermodynamic cycle

    International Nuclear Information System (INIS)

    Bezborodov, Yu.A.; Bubnov, V.P.; Nesterenko, V.B.

    1979-01-01

    The application of air, nitrogen, helium and the chemically reacting N 2 O 4 reversible 2NO 2 reversible 2NO + O 2 system as working agents and coolants for a low capacity nuclear power plant is investigated. The above system due to its physico-chemical and thermo-physical properties allows both a gaseous cycle and a cycle with condensation. The analysis has shown that a thermodynamic air-cooled cycle with the dissociating nitrogen tetroxide in the temperature range from 500 to 600 deg C has an advantage over cycles with air and nitrogen. To identify the chemical reaction kinetics in the thermodynamic processes, thermodynamic calculations of the gas-liquid cycle with N 2 O 4 both with simple and intermediate heat regeneration at different pressures over hot side were performed. At gas pressures lower than 12 - 15 atm, the cycle with a simple regeneration is more effective, and at pressure increase, the cycle with an intermediate regeneration is preferable

  11. Efficiency bounds for nonequilibrium heat engines

    International Nuclear Information System (INIS)

    Mehta, Pankaj; Polkovnikov, Anatoli

    2013-01-01

    We analyze the efficiency of thermal engines (either quantum or classical) working with a single heat reservoir like an atmosphere. The engine first gets an energy intake, which can be done in an arbitrary nonequilibrium way e.g. combustion of fuel. Then the engine performs the work and returns to the initial state. We distinguish two general classes of engines where the working body first equilibrates within itself and then performs the work (ergodic engine) or when it performs the work before equilibrating (non-ergodic engine). We show that in both cases the second law of thermodynamics limits their efficiency. For ergodic engines we find a rigorous upper bound for the efficiency, which is strictly smaller than the equivalent Carnot efficiency. I.e. the Carnot efficiency can be never achieved in single reservoir heat engines. For non-ergodic engines the efficiency can be higher and can exceed the equilibrium Carnot bound. By extending the fundamental thermodynamic relation to nonequilibrium processes, we find a rigorous thermodynamic bound for the efficiency of both ergodic and non-ergodic engines and show that it is given by the relative entropy of the nonequilibrium and initial equilibrium distributions. These results suggest a new general strategy for designing more efficient engines. We illustrate our ideas by using simple examples. -- Highlights: ► Derived efficiency bounds for heat engines working with a single reservoir. ► Analyzed both ergodic and non-ergodic engines. ► Showed that non-ergodic engines can be more efficient. ► Extended fundamental thermodynamic relation to arbitrary nonequilibrium processes

  12. The Geologic Nitrogen Cycle

    Science.gov (United States)

    Johnson, B. W.; Goldblatt, C.

    2013-12-01

    N2 is the dominant gas in Earth's atmosphere, and has been so through the majority of the planet's history. Originally thought to only be cycled in significant amounts through the biosphere, it is becoming increasingly clear that a large degree of geologic cycling can occur as well. N is present in crustal rocks at 10s to 100s of ppm and in the mantle at 1s to perhaps 10s of ppm. In light of new data, we present an Earth-system perspective of the modern N cycle, an updated N budget for the silicate Earth, and venture to explain the evolution of the N cycle over time. In an fashion similar to C, N has a fast, biologically mediated cycle and a slower cycle driven by plate tectonics. Bacteria fix N2 from the atmosphere into bioavailable forms. N is then cycled through the food chain, either by direct consumption of N-fixing bacteria, as NH4+ (the primary waste form), or NO3- (the most common inorganic species in the modern ocean). Some organic material settles as sediment on the ocean floor. In anoxic sediments, NH4+ dominates; due to similar ionic radii, it can readily substitute for K+ in mineral lattices, both in sedimentary rocks and in oceanic lithosphere. Once it enters a subduction zone, N may either be volatilized and returned to the atmosphere at arc volcanoes as N2 or N2O, sequestered into intrusive igneous rocks (as NH4+?), or subducted deep into the mantle, likely as NH4+. Mounting evidence indicates that a significant amount of N may be sequestered into the solid Earth, where it may remain for long periods (100s m.y.) before being returned to the atmosphere/biosphere by volcanism or weathering. The magnitude fluxes into the solid Earth and size of geologic N reservoirs are poorly constrained. The size of the N reservoirs contained in the solid Earth directly affects the evolution of Earth's atmosphere. It is possible that N now sequestered in the solid Earth was once in the atmosphere, which would have resulted in a higher atmospheric pressure, and

  13. Fuel cycle based safeguards

    International Nuclear Information System (INIS)

    De Montmollin, J.M.; Higinbotham, W.A.; Gupta, D.

    1985-07-01

    In NPT safeguards the same model approach and absolute-quantity inspection goals are applied at present to all similar facilities, irrespective of the State's fuel cycle. There is a continuing interest and activity on the part of the IAEA in new NPT safeguards approaches that more directly address a State's nuclear activities as a whole. This fuel cycle based safeguards system is expected to a) provide a statement of findings for the entire State rather than only for individual facilities; b) allocate inspection efforts so as to reflect more realistically the different categories of nuclear materials in the different parts of the fuel cycle and c) provide more timely and better coordinated information on the inputs, outputs and inventories of nuclear materials in a State. (orig./RF) [de

  14. Alternative fuel cycles and non-proliferation aspects

    International Nuclear Information System (INIS)

    Kessler, G.

    1980-10-01

    The most important physical characteristics of the U/Pu and the Th/U fuel cycles and the technical data of the most significant converter reactors operating with Th/U fuel are outlined in the report. Near breeders as well as breeders with a thermal neutron spectrum are briefly discussed, and the potential of breeders with fast neutron spectra in the Th/U fuel is outlined. The essential criteria for the comparison of the alternative fuel cycles with the reference Pu/U cycle are the consumption of natural uranium, the numbers of U-233 producing and U-233 consuming converter reactors and the amounts of fission material transported and handled within the fuel cycle (reprocessing, refabrication). Although the alternative U/Th fuel cycles are feasible with some advantages and some disadvantages as compared to the reference U/Pu cycle, not much experience has so far been gathered with pilot plants of the fuel cycle. The respective status in reprocessing, refabrication and waste disposal is briefly discussed. Finally, a comparison of the risk potential inherent in secular storage is presented and questions of resistance to proliferation and of safeguards of the U/Th cycle are discussed

  15. Cycle accurate and cycle reproducible memory for an FPGA based hardware accelerator

    Science.gov (United States)

    Asaad, Sameh W.; Kapur, Mohit

    2016-03-15

    A method, system and computer program product are disclosed for using a Field Programmable Gate Array (FPGA) to simulate operations of a device under test (DUT). The DUT includes a device memory having a number of input ports, and the FPGA is associated with a target memory having a second number of input ports, the second number being less than the first number. In one embodiment, a given set of inputs is applied to the device memory at a frequency Fd and in a defined cycle of time, and the given set of inputs is applied to the target memory at a frequency Ft. Ft is greater than Fd and cycle accuracy is maintained between the device memory and the target memory. In an embodiment, a cycle accurate model of the DUT memory is created by separating the DUT memory interface protocol from the target memory storage array.

  16. Steam turbine cycle

    International Nuclear Information System (INIS)

    Okuzumi, Naoaki.

    1994-01-01

    In a steam turbine cycle, steams exhausted from the turbine are extracted, and they are connected to a steam sucking pipe of a steam injector, and a discharge pipe of the steam injector is connected to an inlet of a water turbine. High pressure discharge water is obtained from low pressure steams by utilizing a pressurizing performance of the steam injector and the water turbine is rotated by the high pressure water to generate electric power. This recover and reutilize discharged heat of the steam turbine effectively, thereby enabling to improve heat efficiency of the steam turbine cycle. (T.M.)

  17. Global water cycle

    Science.gov (United States)

    Robertson, Franklin; Goodman, Steven J.; Christy, John R.; Fitzjarrald, Daniel E.; Chou, Shi-Hung; Crosson, William; Wang, Shouping; Ramirez, Jorge

    1993-01-01

    This research is the MSFC component of a joint MSFC/Pennsylvania State University Eos Interdisciplinary Investigation on the global water cycle extension across the earth sciences. The primary long-term objective of this investigation is to determine the scope and interactions of the global water cycle with all components of the Earth system and to understand how it stimulates and regulates change on both global and regional scales. Significant accomplishments in the past year are presented and include the following: (1) water vapor variability; (2) multi-phase water analysis; (3) global modeling; and (4) optimal precipitation and stream flow analysis and hydrologic processes.

  18. Coordination cycles

    Czech Academy of Sciences Publication Activity Database

    Steiner, Jakub

    -, č. 274 (2005), s. 1-26 ISSN 1211-3298 Institutional research plan: CEZ:AV0Z70850503 Keywords : coordination * crises * cycles and fluctuations Subject RIV: AH - Economics http://www.cerge-ei.cz/pdf/wp/Wp274.pdf

  19. Low cycle fatigue: high cycle fatigue damage accumulation in a 304L austenitic stainless steel

    International Nuclear Information System (INIS)

    Lehericy, Y.

    2007-05-01

    The aim of this study was to evaluate the consequences of a Low Cycle Fatigue pre-damage on the subsequent fatigue limit of a 304L stainless steel. The effects of hardening and severe roughness (grinding) have also been investigated. In a first set of tests, the evolution of the surface damage induced by the different LCF pre-cycling was characterized. This has permitted to identify mechanisms and kinetics of damage in the plastic domain for different surface conditions. Then, pre-damaged samples were tested in the High Cycle Fatigue domain in order to establish the fatigue limits associated with each level of pre-damage. Results evidence that, in the case of polished samples, an important number of cycles is required to initiate surface cracks ant then to affect the fatigue limit of the material but, in the case of ground samples, a few number of cycles is sufficient to initiate cracks and to critically decrease the fatigue limit. The fatigue limit of pre-damaged samples can be estimated using the stress intensity factor threshold. Moreover, this detrimental effect of severe surface conditions is enhanced when fatigue tests are performed under a positive mean stress (author)

  20. Nonlinear solar cycle forecasting: theory and perspectives

    Science.gov (United States)

    Baranovski, A. L.; Clette, F.; Nollau, V.

    2008-02-01

    In this paper we develop a modern approach to solar cycle forecasting, based on the mathematical theory of nonlinear dynamics. We start from the design of a static curve fitting model for the experimental yearly sunspot number series, over a time scale of 306 years, starting from year 1700 and we establish a least-squares optimal pulse shape of a solar cycle. The cycle-to-cycle evolution of the parameters of the cycle shape displays different patterns, such as a Gleissberg cycle and a strong anomaly in the cycle evolution during the Dalton minimum. In a second step, we extract a chaotic mapping for the successive values of one of the key model parameters - the rate of the exponential growth-decrease of the solar activity during the n-th cycle. We examine piece-wise linear techniques for the approximation of the derived mapping and we provide its probabilistic analysis: calculation of the invariant distribution and autocorrelation function. We find analytical relationships for the sunspot maxima and minima, as well as their occurrence times, as functions of chaotic values of the above parameter. Based on a Lyapunov spectrum analysis of the embedded mapping, we finally establish a horizon of predictability for the method, which allows us to give the most probable forecasting of the upcoming solar cycle 24, with an expected peak height of 93±21 occurring in 2011/2012.

  1. NICMOS Cycles 13 and 14 Calibration Plans

    Science.gov (United States)

    Arribas, Santiago; Bergeron, Eddie; de Jong, Roeof; Malhotra, Sangeeta; Mobasher, Bahram; Noll, Keith; Schultz, Al; Wiklind, Tommy; Xu, Chun

    2005-11-01

    This document summarizes the NICMOS Calibration Plans for Cycles 13 and 14. These plans complement the SMOV3b, the Cycle 10 (interim), and the Cycles 11 and 12 (regular) calibration programs executed after the installation of the NICMOS Cooling System (NCS).. These previous programs have shown that the instrument is very stable, which has motivated a further reduction in the frequency of the monitoring programs for Cycle 13. In addition, for Cycle 14 some of these programs were slightly modified to account for 2 Gyro HST operations. The special calibrations on Cycle 13 were focussed on a follow up of the spectroscopic recalibration initiated in Cycle 12. This program led to the discovery of a possible count rate non-linearity, which has triggered a special program for Cycle 13 and a number of subsequent tests and calibrations during Cycle 14. At the time of writing this is a very active area of research. We also briefly comment on other calibrations defined to address other specific issues like: the autoreset test, the SPAR sequences tests, and the low-frequency flat residual for NIC1. The calibration programs for the 2-Gyro campaigns are not included here, since they have been described somewhere else. Further details and updates on specific programs can be found via the NICMOS web site.

  2. Pyroelectric Energy Harvesting: With Thermodynamic-Based Cycles

    OpenAIRE

    Saber Mohammadi; Akram Khodayari

    2012-01-01

    This work deals with energy harvesting from temperature variations using ferroelectric materials as a microgenerator. The previous researches show that direct pyroelectric energy harvesting is not effective, whereas thermodynamic-based cycles give higher energy. Also, at different temperatures some thermodynamic cycles exhibit different behaviours. In this paper pyroelectric energy harvesting using Lenoir and Ericsson thermodynamic cycles has been studied numerically and the two cycles were c...

  3. Comparative energy analysis on a new regenerative Brayton cycle

    International Nuclear Information System (INIS)

    Goodarzi, M.

    2016-01-01

    Highlights: • New regenerative Brayton cycle has been introduced. • New cycle has higher thermal efficiency and lower exhausted heat per output power. • Regenerator may remain useful in the new cycle even at high pressure ratio. • New regenerative Brayton cycle is suggested for low pressure ratio operations. - Abstract: Gas turbines are frequently used for power generation. Brayton cycle is the basis for gas turbine operation and developing the alternative cycles. Regenerative Brayton cycle is a developed cycle for basic Brayton cycle with higher thermal efficiency at low to moderate pressure ratios. A new regenerative Brayton cycle has been introduced in the present study. Energy analysis has been conducted on ideal cycles to compare them from the first law of thermodynamics viewpoint. Comparative analyses showed that the new regenerative Brayton cycle has higher thermal efficiency than the original one at the same pressure ratio, and also lower heat absorption and exhausted heat per unite output power. Computed results show that new cycle improves thermal efficiency from 12% to 26% relative to the original regenerative Brayton cycle in the range of studied pressure ratios. Contrary to the original regenerative Brayton cycle, regenerator remains useful in the new regenerative Brayton cycle even at higher pressure ratio.

  4. Naturalistic drive cycle synthesis for pickup trucks.

    Science.gov (United States)

    Liu, Zifan; Ivanco, Andrej; Filipi, Zoran

    2015-09-01

    Future pick-up trucks are meeting much stricter fuel economy and exhaust emission standards. Design tradeoffs will have to be carefully evaluated to satisfy consumer expectations within the regulatory and cost constraints. Boundary conditions will obviously be critical for decision making: thus, the understanding of how customers are driving in naturalistic settings is indispensable. Federal driving schedules, while critical for certification, do not capture the richness of naturalistic cycles, particularly the aggressive maneuvers that often shape consumer perception of performance. While there are databases with large number of drive cycles, applying all of them directly in the design process is impractical. Therefore, representative drive cycles that capture the essence of the naturalistic driving should be synthesized from naturalistic driving data. Naturalistic drive cycles are firstly categorized by investigating their micro-trip components, defined as driving activities between successive stops. Micro-trips are expected to characterize underlying local traffic conditions, and separate different driving patterns. Next, the transitions from one vehicle state to another vehicle state in each cycle category are captured with Transition Probability Matrix (TPM). Candidate drive cycles can subsequently be synthesized using Markov Chain based on TPMs for each category. Finally, representative synthetic drive cycles are selected through assessment of significant cycle metrics to identify the ones with smallest errors. This paper provides a framework for synthesis of representative drive cycles from naturalistic driving data, which can subsequently be used for efficient optimization of design or control of pick-up truck powertrains. Manufacturers will benefit from representative drive cycles in several aspects, including quick assessments of vehicle performance and energy consumption in simulations, component sizing and design, optimization of control strategies, and

  5. Human chorionic gonadotropin-administered natural cycle versus spontaneous ovulatory cycle in patients undergoing two pronuclear zygote frozen-thawed embryo transfer.

    Science.gov (United States)

    Lee, You-Jung; Kim, Chung-Hoon; Kim, Do-Young; Ahn, Jun-Woo; Kim, Sung-Hoon; Chae, Hee-Dong; Kang, Byung-Moon

    2018-03-01

    To compare human chorionic gonadotropin (HCG)-administered natural cycle with spontaneous ovulatory cycle in patients undergoing frozen-thawed embryo transfer (FTET) in natural cycles. In this retrospective cohort study, we analyzed the clinical outcome of a total of 166 consecutive FTET cycles that were performed in either natural cycle controlled by HCG for ovulation triggering (HCG group, n=110) or natural cycle with spontaneous ovulation (control group, n=56) in 166 infertile patients between January 2009 and November 2013. There were no differences in patients' characteristics between the 2 groups. The numbers of oocytes retrieved, mature oocytes, fertilized oocytes, grade I or II embryos and frozen embryos in the previous in vitro fertilization (IVF) cycle in which embryos were frozen were comparable between the HCG and control groups. Significant differences were not also observed between the 2 groups in clinical pregnancy rate (CPR), embryo implantation rate, miscarriage rate, live birth rate and multiple CPR. However, the number of hospital visits for follicular monitoring was significantly fewer in the HCG group than in the control group ( P cycle reduces the number of hospital visits for follicular monitoring without any detrimental effect on FTET outcome when compared with spontaneous ovulatory cycles in infertile patients undergoing FTET in natural ovulatory cycles.

  6. Drought and ecosystem carbon cycling

    NARCIS (Netherlands)

    Molen, M.K. van der; Dolman, A.J.; Ciais, P.; Eglin, T.; Gobron, N.; Law, B.E.; Meir, P.; Peters, P.; Philips, O.L.; Reichstein, M.; Chen, T.; Dekker, S.C.; Doubkova, M.; Friedl, M.A.; Jung, M.; Hurk, B.J.J.M. van den; Jeu, R.A.M. de; Kruijt, B.; Ohta, T.; Rebel, K.T.; Plummer, S.; Seneviratne, S.I.; Sitch, S.; Teuling, A.J.; Werf, G.R. van der; Wang, G.

    2011-01-01

    Drought as an intermittent disturbance of the water cycle interacts with the carbon cycle differently than the ‘gradual’ climate change. During drought plants respond physiologically and structurally to prevent excessive water loss according to species-specific water use strategies. This has

  7. Coordination cycles

    Czech Academy of Sciences Publication Activity Database

    Steiner, Jakub

    2008-01-01

    Roč. 63, č. 1 (2008), s. 308-327 ISSN 0899-8256 Institutional research plan: CEZ:AV0Z70850503 Keywords : global games * coordination * crises * cycles and fluctuations Subject RIV: AH - Economics Impact factor: 1.333, year: 2008

  8. Homogeneous Thorium Fuel Cycles in Candu Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Hyland, B.; Dyck, G.R.; Edwards, G.W.R.; Magill, M. [Chalk River Laboratories, Atomic Energy of Canada Limited (Canada)

    2009-06-15

    The CANDU{sup R} reactor has an unsurpassed degree of fuel-cycle flexibility, as a consequence of its fuel-channel design, excellent neutron economy, on-power refueling, and simple fuel bundle [1]. These features facilitate the introduction and full exploitation of thorium fuel cycles in Candu reactors in an evolutionary fashion. Because thorium itself does not contain a fissile isotope, neutrons must be provided by adding a fissile material, either within or outside of the thorium-based fuel. Those same Candu features that provide fuel-cycle flexibility also make possible many thorium fuel-cycle options. Various thorium fuel cycles can be categorized by the type and geometry of the added fissile material. The simplest of these fuel cycles are based on homogeneous thorium fuel designs, where the fissile material is mixed uniformly with the fertile thorium. These fuel cycles can be competitive in resource utilization with the best uranium-based fuel cycles, while building up a 'mine' of U-233 in the spent fuel, for possible recycle in thermal reactors. When U-233 is recycled from the spent fuel, thorium-based fuel cycles in Candu reactors can provide substantial improvements in the efficiency of energy production from existing fissile resources. The fissile component driving the initial fuel could be enriched uranium, plutonium, or uranium-233. Many different thorium fuel cycle options have been studied at AECL [2,3]. This paper presents the results of recent homogeneous thorium fuel cycle calculations using plutonium and enriched uranium as driver fuels, with and without U-233 recycle. High and low burnup cases have been investigated for both the once-through and U-233 recycle cases. CANDU{sup R} is a registered trademark of Atomic Energy of Canada Limited (AECL). 1. Boczar, P.G. 'Candu Fuel-Cycle Vision', Presented at IAEA Technical Committee Meeting on 'Fuel Cycle Options for LWRs and HWRs', 1998 April 28 - May 01, also Atomic Energy

  9. Endogenous, Imperfectly Competitive Business Cycles

    DEFF Research Database (Denmark)

    Whitta-Jacobsen, Hans Jørgen

    We investigate how imperfect competition affects the occurrence and the properties of endogenous, rational expectations business cycles in an overlapping generations model with constant returns to scale in production. The model has explicit product and labor markets all characterized...... by monopolistic competition. An implicit assumption of barriers to entry justifies that the number of firms is fixed even when positive profits occur. It turns out that both market power of firms on the product markets and market power of unions on the labor markets make the occurrence of cycles more likely....... In particular, imperfect competition on the product markets and the positive profits associated with it may have the effect that there is a cycle even if the labor supply curve is increasing in the real-wage rate. For competitive cycles is required not only a decreasing labor supply curve, but a wage elasticity...

  10. Comparison of rapid-cycling and non-rapid-cycling bipolar disorder based on prospective mood ratings in 539 outpatients

    NARCIS (Netherlands)

    Kupka, RW; Luckenbaugh, DA; Post, RM; Suppes, T; Altshuler, LL; Keck, PE; Frye, MA; Denicoff, KD; Grunze, H; Leverich, GS; McElroy, SL; Walden, J; Nolen, WA

    Objective: To detect risk factors for rapid cycling in bipolar disorder, the authors compared characteristics of rapid-cycling and non-rapid-cycling patients both from a categorical and a dimensional perspective. Method: Outpatients with bipolar I disorder (N = 419), bipolar II disorder (N = 104),

  11. Nuclear fuel cycles : description, demand and supply estimates

    International Nuclear Information System (INIS)

    Gadallah, A.A.; Abou Zahra, A.A.; Hammad, F.H.

    1985-01-01

    This report deals with various nuclear fuel cycles description as well as the world demand and supply estimates of materials and services. Estimates of world nuclear fuel cycle requirements: nuclear fuel, heavy water and other fuel cycle services as well as the availability and production capabilities of these requirements, are discussed for several reactor fuel cycle strategies, different operating and under construction fuel cycle facilities in some industrialized and developed countries are surveyed. Various uncertainties and bottlenecks which are recently facing the development of some fuel cycle components are also discussed, as well as various proposals concerning fuel cycle back-end concepts. finally, the nuclear fuel cycles activities in some developing countries are reviewed with emphasis on the egyptian plans to introduce nuclear power in the country. 11 fig., 16 tab

  12. Variable geometry gas turbines for improving the part-load performance of marine combined cycles - Combined cycle performance

    DEFF Research Database (Denmark)

    Haglind, Fredrik

    2011-01-01

    The part-load performance of combined cycles intended for naval use is of great importance, and it is influenced by the gas turbine configuration and load control strategy. This paper is aimed at quantifying the effects of variable geometry gas turbines on the part-load efficiency for combined...... cycles used for ship propulsion. Moreover, the paper is aimed at developing methodologies and deriving models for part-load simulations suitable for energy system analysis of various components within combined cycle power plants. Two different gas turbine configurations are studied, a two-shaft aero......-derivative configuration and a single-shaft industrial configuration. The results suggest that by the use of variable geometry gas turbines, the combined cycle part-load performance can be improved. In order to minimise the voyage fuel consumption, a combined cycle featuring two-shaft gas turbines with VAN control...

  13. Role of expanders in helium liquefaction cycles: Parametric studies using Collins cycle

    International Nuclear Information System (INIS)

    Thomas, Rijo Jacob; Ghosh, Parthasarathi; Chowdhury, Kanchan

    2011-01-01

    Large scale helium liquefaction/refrigeration plant is a key subsystem of fusion devices. Performance of these plants is dependent on a number of geometric and operating parameters of its constituting components such as compressors, heat exchangers, expanders, valves, etc. Expander has been chosen as the subject matter of analyses in the present study. As the sensible cold of helium vapor is lost in liquefiers, the expanders in liquefaction cycles have to provide more refrigeration than those in refrigeration cycles. The expander parameters such as rate of mass flow, operating pressure, inlet temperature, etc. are inter-dependent, and hence, it is difficult to predict the system behavior with variation of a particular parameter. This necessitates the use of process simulators. Parametric studies have been performed on Collins helium liquefaction cycle using Aspen HYSYS. Collins cycle has all the basic characteristics of a large-scale helium liquefier and the results of this study may be extrapolated to understand the behavior of large scale helium liquefiers. The study shows that the maximum liquid production is obtained when 80% of the compressor flow is diverted through the expanders and it is equally distributed between the two expanders. The relationships between the liquid production and the isentropic efficiency of expanders are almost linear and both the higher and lower temperature expanders exhibit similar trends.

  14. Role of expanders in helium liquefaction cycles: Parametric studies using Collins cycle

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Rijo Jacob, E-mail: rijojthomas@gmail.com [Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur, West Bengal 721302 (India); Ghosh, Parthasarathi; Chowdhury, Kanchan [Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur, West Bengal 721302 (India)

    2011-06-15

    Large scale helium liquefaction/refrigeration plant is a key subsystem of fusion devices. Performance of these plants is dependent on a number of geometric and operating parameters of its constituting components such as compressors, heat exchangers, expanders, valves, etc. Expander has been chosen as the subject matter of analyses in the present study. As the sensible cold of helium vapor is lost in liquefiers, the expanders in liquefaction cycles have to provide more refrigeration than those in refrigeration cycles. The expander parameters such as rate of mass flow, operating pressure, inlet temperature, etc. are inter-dependent, and hence, it is difficult to predict the system behavior with variation of a particular parameter. This necessitates the use of process simulators. Parametric studies have been performed on Collins helium liquefaction cycle using Aspen HYSYS. Collins cycle has all the basic characteristics of a large-scale helium liquefier and the results of this study may be extrapolated to understand the behavior of large scale helium liquefiers. The study shows that the maximum liquid production is obtained when 80% of the compressor flow is diverted through the expanders and it is equally distributed between the two expanders. The relationships between the liquid production and the isentropic efficiency of expanders are almost linear and both the higher and lower temperature expanders exhibit similar trends.

  15. Analysis of Refrigeration Cycle Performance with an Ejector

    Directory of Open Access Journals (Sweden)

    Wani J. R.

    2016-01-01

    Full Text Available A conventional refrigeration cycle uses expansion device between the condenser and the evaporator which has losses during the expansion process. A refrigeration cycle with ejector is a promising modification to improve the performance of conventional refrigeration cycle. The ejector is used to recover some of the available work so that the compressor suction pressure increases. To investigate the enhancement a model with R134a refrigerant was developed. To solve the set of equations and simulate the cycle performance a subroutine was written on engineering equation solver (EES environment. At specific conditions, the refrigerant properties are obtained from EES. At the design conditions the ejector refrigeration cycle achieved 5.141 COP compared to 4.609 COP of the conventional refrigeration cycle. This means that ejector refrigeration cycle offers better COP with 10.35% improvement compared to conventional refrigeration cycle. Parametric analysis of ejector refrigeration cycle indicated that COP was influenced significantly by evaporator and condenser temperatures, entrainment ratio and diffuser efficiency.

  16. The global carbon cycle

    International Nuclear Information System (INIS)

    Maier-Reimer, E.

    1991-01-01

    Basic concepts of the global carbon cycle on earth are described; by careful analyses of isotopic ratios, emission history and oceanic ventilation rates are derived, which provide crucial tests for constraining and calibrating models. Effects of deforestation, fertilizing, fossil fuel burning, soil erosion, etc. are quantified and compared, and the oceanic carbon process is evaluated. Oceanic and terrestrial biosphere modifications are discussed and a carbon cycle model is proposed

  17. International Real Business Cycles

    OpenAIRE

    Mario J. Crucini

    2006-01-01

    This paper is a non-technical review of research developments in the international real business cycle literature. International business cycle facts are summarize with particular attention to the sources of output variance from the expenditure side of the NIPA and the production side, using a familiar neoclassical production function. Theoretical developments focus on the how consumption smoothing and investment dynamics shape the current account; the search for sources and propagation mecha...

  18. Hat cycle dynamic simulation

    International Nuclear Information System (INIS)

    Trucco, A.; Corallo, C.; Pini Prato, A.; Porro, S.

    1999-01-01

    Among the innovative cycle recently proposed in literature, the Humid Air Turbine Cycle - Hat better seems to fulfil the main energy market requirements of today: High efficiency in a large power ranger, low pollution, low specific capital cost. The previous results of an analysis at partial load and transient conditions are here presented, where the Hat plant has been simulated using the original model implemented in LEGO environment [it

  19. The Sphinx's Riddle: Life and Career Cycles.

    Science.gov (United States)

    Burack, Elmer H.

    1984-01-01

    Career cycles should be considered apart from life cycles, even though the two are interrelated. This essay examines five theories about life and career cycles, and offers insights into their limitations and potential uses. (JB)

  20. Evaporative cycles - in theory and in practise

    Energy Technology Data Exchange (ETDEWEB)

    Rosen, P.M.

    2000-08-01

    The thesis is based on applied research, rather closed to industrial development. The developed simulation model, for pre-design of evaporative gas turbine cycles, has been validated in a 600 kW pilot plant and in rebuilt turbo-charged diesel engines. Besides of the work with the thesis including theoretical modelling and hardware development concerning wet cycles, the work has also resulted in three patents dealing with the technique studied. The main feature of the evaporative cycles is the way the integration between the gas and liquid flows is executed, combined with using low-level heat gathered into the liquid phase which is later used to evaporate the liquid itself in a humidification tower. In this tower, the mass- and heat transfer take place under stable physical laws, and if the tower is properly designed, the distilling effect in the tower will also be high. Today the combined cycle has the best thermal efficiency to generate electricity from fuels. Every new power cycle, including the evaporative cycles, will therefore be compared with power stations based on combined cycles. In evaporative cycles, the steam bottoming cycle of the combined cycles has been eliminated. Instead the 'steam' cycle is integrated into the gas cycle. This action has a favourable effect on thermal efficiency and on NO{sub x} formation in the combustion zone. The major part of this thesis is about the EvGT-project. At Lund University, the major objective of this project was to develop, design, erect and operate the world's first evaporative gas turbine unit. The objective was accomplished in 1999, and in the process of reaching the objective, rather large modelling errors, both thermodynamic and dimensioning of the humidification tower, have been detected in the open literature. It seems as if the pressure dependency of the humidification process has been underestimated in the models used today. The EvGT-pilot plant at Lund University was built and taken into

  1. Fuel cycles using adulterated plutonium

    International Nuclear Information System (INIS)

    Brooksbank, R.E.; Bigelow, J.E.; Campbell, D.O.; Kitts, F.G.; Lindauer, R.B.

    1978-01-01

    Adjustments in the U-Pu fuel cycle necessitated by decisions made to improve the nonproliferation objectives of the US are examined. The uranium-based fuel cycle, using bred plutonium to provide the fissile enrichment, is the fuel system with the highest degree of commercial development at the present time. However, because purified plutonium can be used in weapons, this fuel cycle is potentially vulnerable to diversion of that plutonium. It does appear that there are technologically sound ways in which the plutonium might be adulterated by admixture with 238 U and/or radioisotopes, and maintained in that state throughout the fuel cycle, so that the likelihood of a successful diversion is small. Adulteration of the plutonium in this manner would have relatively little effect on the operations of existing or planned reactors. Studies now in progress should show within a year or two whether the less expensive coprocessing scheme would provide adequate protection (coupled perhaps with elaborate conventional safeguards procedures) or if the more expensive spiked fuel cycle is needed as in the proposed civex pocess. If the latter is the case, it will be further necessary to determine the optimum spiking level, which could vary as much as a factor of a billion. A very basic question hangs on these determinations: What is to be the nature of the recycle fuel fabrication facilities. If the hot, fully remote fuel fabrication is required, then a great deal of further development work will be required to make the full cycle fully commercial

  2. Thermodynamic efficiency analysis and cycle optimization of deeply precooled combined cycle engine in the air-breathing mode

    Science.gov (United States)

    Zhang, Jianqiang; Wang, Zhenguo; Li, Qinglian

    2017-09-01

    The efficiency calculation and cycle optimization were carried out for the Synergistic Air-Breathing Rocket Engine (SABRE) with deeply precooled combined cycle. A component-level model was developed for the engine, and exergy efficiency analysis based on the model was carried out. The methods to improve cycle efficiency have been proposed. The results indicate cycle efficiency of SABRE is between 29.7% and 41.7% along the flight trajectory, and most of the wasted exergy is occupied by the unburned hydrogen in exit gas. Exergy loss exists in each engine component, and the sum losses of main combustion chamber(CC), pre-burner(PB), precooler(PC) and 3# heat exchanger(HX3) are greater than 71.3% of the total loss. Equivalence ratio is the main influencing factor of cycle, and it can be regulated by adjusting parameters of helium loop. Increase the maximum helium outlet temperature of PC by 50 K, the total assumption of hydrogen will be saved by 4.8%, and the cycle efficiency is advanced by 3% averagely in the trajectory. Helium recirculation scheme introduces a helium recirculation loop to increase local helium flow rate of PC. It turns out the total assumption of hydrogen will be saved by 9%, that's about 1740 kg, and the cycle efficiency is advanced by 5.6% averagely.

  3. Rotary Stirling-Cycle Engine And Generator

    Science.gov (United States)

    Chandler, Joseph A.

    1990-01-01

    Proposed electric-power generator comprises three motor generators coordinated by microprocessor and driven by rotary Stirling-cycle heat engine. Combination offers thermodynamic efficiency of Stirling cycle, relatively low vibration, and automatic adjustment of operating parameters to suit changing load on generator. Rotary Stirling cycle engine converts heat to power via compression and expansion of working gas between three pairs of rotary pistons on three concentric shafts in phased motion. Three motor/generators each connected to one of concentric shafts, can alternately move and be moved by pistons. Microprocessor coordinates their operation, including switching between motor and generator modes at appropriate times during each cycle.

  4. Life Cycle Assessment for Biofuels

    Science.gov (United States)

    A presentation based on life cycle assessment (LCA) for biofuels is given. The presentation focuses on energy and biofuels, interesting environmental aspects of biofuels, and how to do a life cycle assessment with some examples related to biofuel systems. The stages of a (biofuel...

  5. TryCYCLE: A Prospective Study of the Safety and Feasibility of Early In-Bed Cycling in Mechanically Ventilated Patients.

    Directory of Open Access Journals (Sweden)

    Michelle E Kho

    Full Text Available The objective of this study was to assess the safety and feasibility of in-bed cycling started within the first 4 days of mechanical ventilation (MV to inform a future randomized clinical trial.We conducted a 33-patient prospective cohort study in a 21-bed adult academic medical-surgical intensive care unit (ICU in Hamilton, ON, Canada. We included adult patients (≥ 18 years receiving MV who walked independently pre-ICU. Our intervention was 30 minutes of in-bed supine cycling 6 days/week in the ICU. Our primary outcome was Safety (termination, measured as events prompting cycling termination; secondary Safety (disconnection or dislodgement outcomes included catheter/tube dislodgements. Feasibility was measured as consent rate and fidelity to intervention. For our primary outcome, we calculated the binary proportion and 95% confidence interval (CI.From 10/2013-8/2014, we obtained consent from 34 of 37 patients approached (91.9%, 33 of whom received in-bed cycling. Of those who cycled, 16(48.4% were female, the mean (SD age was 65.8(12.2 years, and APACHE II score was 24.3(6.7; 29(87.9% had medical admitting diagnoses. Cycling termination was infrequent (2.0%, 95% CI: 0.8%-4.9% and no device dislodgements occurred. Cycling began a median [IQR] of 3 [2, 4] days after ICU admission; patients received 5 [3, 8] cycling sessions with a median duration of 30.7 [21.6, 30.8] minutes per session. During 205 total cycling sessions, patients were receiving invasive MV (150 [73.1%], vasopressors (6 [2.9%], sedative or analgesic infusions (77 [37.6%] and dialysis (4 [2.0%].Early cycling within the first 4 days of MV among hemodynamically stable patients is safe and feasible. Research to evaluate the effect of early cycling on patient function is warranted.Clinicaltrials.gov: NCT01885442.

  6. The evolving nuclear fuel cycle

    International Nuclear Information System (INIS)

    Gale, J.D.; Hanson, G.E.; Coleman, T.A.

    1993-01-01

    Various economics and political pressures have shaped the evolution of nuclear fuel cycles over the past 10 to 15 yr. Future trends will no doubt be similarly driven. This paper discusses the influences that long cycles, high discharge burnups, fuel reliability, and costs will have on the future nuclear cycle. Maintaining the economic viability of nuclear generation is a key issue facing many utilities. Nuclear fuel has been a tremendous bargain for utilities, helping to offset major increases in operation and maintenance (O ampersand M) expenses. An important factor in reducing O ampersand M costs is increasing capacity factor by eliminating outages

  7. The fuel cycle scoping system

    International Nuclear Information System (INIS)

    Dooley, G.D.; Malone, J.P.

    1986-01-01

    The Fuel Cycle Scoping System (FCSS) was created to fill the need for a scoping tool which provides the utilities with the ability to quickly evaluate alternative fuel management strategies, tails assay choices, fuel fabrication quotes, fuel financing alternatives, fuel cycle schedules, and other fuel cycle perturbations. The FCSS was specifically designed for PC's that support dBASE-III(TM), a relational data base software system by Ashton-Tate. However, knowledge of dBASE-III is not necessary in order to utilize the FCSS. The FCSS is menu driven and can be utilized as a teaching tool as well as a scoping tool

  8. Digital daily cycles of individuals

    DEFF Research Database (Denmark)

    Aledavood, Talayeh; Jørgensen, Sune Lehmann; Saramäki, Jari

    2015-01-01

    Humans, like almost all animals, are phase-locked to the diurnal cycle. Most of us sleep at night and are active through the day. Because we have evolved to function with this cycle, the circadian rhythm is deeply ingrained and even detectable at the biochemical level. However, within the broader...... day-night pattern, there are individual differences: e.g., some of us are intrinsically morning-active, while others prefer evenings. In this article, we look at digital daily cycles: circadian patterns of activity viewed through the lens of auto-recorded data of communication and online activity. We...

  9. Fuel cycle parameters for strategy studies

    International Nuclear Information System (INIS)

    Archinoff, G.H.

    1979-05-01

    This report summarizes seven fuel cycle parameters (efficiency, specific power, burnup, equilibrium net fissile feed, equilibrium net fissile surplus, first charge fissile content, and whether or not fuel reprocessing is required) to be used in long-term strategy analyses of fuel cycles based on natural UO 2 , low enriched uranium, mixed oxides, plutonium topped thorium, uranium topped thorium, and the fast breeder oxide cycle. (LL)

  10. Synergistic fuel cycles of the future

    International Nuclear Information System (INIS)

    Meneley, D.A.; Dastur, A.R.

    1997-01-01

    Good neutron economy is the basis of the fuel cycle flexibility in the CANDU reactor. This paper describes the fuel cycle options available to the CANDU owner with special emphasis on resource conservation and waste management. CANDU fuel cycles with low initial fissile content operate with relatively high conversion ratio. The natural uranium cycle provides over 55 % of energy from the plutonium that is created during fuel life. Resource utilization is over 7 MWd/kg NU. This can be improved by slight enrichment (between 0.9 and 1.2 wt % U235) of the fuel. Resource utilization increases to 11 MWd/kg NU with the Slightly Enriched Uranium cycle. Thorium based cycles in CANDU operate at near-breeder efficiency. Obey provide attractive options when used with natural uranium or separated (reactor grade and weapons grade) plutonium as driver fuels. In the latter case, the energy from the U233 plus the initial plutonium content amounts to 3.4 GW(th).d/kg Pu-fissile. The same utilization is expected from the use of FBR plutonium in a CANDU thorium cycle. Extension of natural resource is achieved by the use of spent fuels in CANDU. The LWR/CANDU Tandem cycle leads to an additional 77 % of energy through the use of reprocessed LWR fuel (which has a fissile content of 1.6 wt %) in CANDU. Dry reprocessing of LWR fuel with the OREOX process (a more safeguardable alternative to the PUREX process) provides an additional 50 % energy. Uranium recovered (RU) from separation of plutonium contained in spent LWR fuel provides an additional 15 MWd/kg RU. CANDU's low fissile requirement provides the possibility, through the use of non-fertile targets, of extracting energy from the minor actinides contained in spent fuel. In addition to the resource utilization advantage described above, there is a corresponding reduction in waste arisings with such cycles. This is especially significant when separated plutonium is available as a fissile resource. (author)

  11. Exergy Losses in the Szewalski Binary Vapor Cycle

    Directory of Open Access Journals (Sweden)

    Tomasz Kowalczyk

    2015-10-01

    Full Text Available In this publication, we present an energy and exergy analysis of the Szewalski binary vapor cycle based on a model of a supercritical steam power plant. We used energy analysis to conduct a preliminary optimization of the cycle. Exergy loss analysis was employed to perform a comparison of heat-transfer processes, which are essential for hierarchical cycles. The Szewalski binary vapor cycle consists of a steam cycle bottomed with an organic Rankine cycle installation. This coupling has a negative influence on the thermal efficiency of the cycle. However, the primary aim of this modification is to reduce the size of the power unit by decreasing the low-pressure steam turbine cylinder and the steam condenser. The reduction of the “cold end” of the turbine is desirable from economic and technical standpoints. We present the Szewalski binary vapor cycle in addition to a mathematical model of the chosen power plant’s thermodynamic cycle. We elaborate on the procedure of the Szewalski cycle design and its optimization in order to attain an optimal size reduction of the power unit and limit exergy loss.

  12. Direct expansion solar assisted heat pumps – A clean steady state approach for overall performance analysis

    International Nuclear Information System (INIS)

    Tagliafico, Luca A.; Scarpa, Federico; Valsuani, Federico

    2014-01-01

    Traditional thermal solar panel technologies have limited efficiency and the required economic investments make them noncompetitive in the space heating market. The greatest limit to the diffusion of thermal solar systems is the characteristic temperatures they can reach: the strong connection between the user temperature and the collector temperature makes it possible to achieve high thermal (collector) efficiency only at low, often useless, user temperatures. By using solar collectors as thermal exchange units (evaporators) in a heat pump system (direct expansion solar assisted heat pump, DX-SAHP), the overall efficiency greatly increases with a significative cut of the associated investment in terms of pay-back time. In this study, an approach is proposed to the steady state analysis of DX-SAHP, which is based on the simplified inverse Carnot cycle and on the second law efficiency concept. This method, without the need of calculating the refrigerant fluid properties and the detailed processes occurring in the refrigeration device, allows us to link the main features of the plant to its relevant interactions with the surroundings. The very nature of the proposed method makes the relationship explicit and meaningful among all the involved variables. The paper, after the description of the method, presents an explanatory application of this technique by reviewing various aspects of the performance of a typical DX-SAHP in which the savings on primary energy consumption is regarded as the main feature of the plant and highlighted in a monthly averaged analysis. Results agree to those coming from a common standard steady state thermodynamic analysis. The application to a typical DX-SAHP system demonstrates that a mean saved primary energy of about 50% with respect to standard gas burner can be achieved for the same user needs. Such a result is almost independent from the type of flat plate solar panel used (double or single glazed, or even bare panels) as a result of

  13. Advanced nuclear fuel cycles and radioactive waste management

    International Nuclear Information System (INIS)

    2006-01-01

    This study analyses a range of advanced nuclear fuel cycle options from the perspective of their effect on radioactive waste management policies. It presents various fuel cycle options which illustrate differences between alternative technologies, but does not purport to cover all foreseeable future fuel cycles. The analysis extends the work carried out in previous studies, assesses the fuel cycles as a whole, including all radioactive waste generated at each step of the cycles, and covers high-level waste repository performance for the different fuel cycles considered. The estimates of quantities and types of waste arising from advanced fuel cycles are based on best available data and experts' judgement. The effects of various advanced fuel cycles on the management of radioactive waste are assessed relative to current technologies and options, using tools such as repository performance analysis and cost studies. (author)

  14. Fatigue diminishes motoneuronal excitability during cycling exercise.

    Science.gov (United States)

    Weavil, Joshua C; Sidhu, Simranjit K; Mangum, Tyler S; Richardson, Russell S; Amann, Markus

    2016-10-01

    Exercise-induced fatigue influences the excitability of the motor pathway during single-joint isometric contractions. This study sought to investigate the influence of fatigue on corticospinal excitability during cycling exercise. Eight men performed fatiguing constant-load (80% W peak ; 241 ± 13 W) cycling to exhaustion during which the percent increase in quadriceps electromyography (ΔEMG; vastus lateralis and rectus femoris) was quantified. During a separate trial, subjects performed two brief (∼45 s) nonfatiguing cycling bouts (244 ± 15 and 331 ± 23W) individually chosen to match the ΔEMG across bouts to that observed during fatiguing cycling. Corticospinal excitability during exercise was quantified by transcranial magnetic, electric transmastoid, and femoral nerve stimulation to elicit motor-evoked potentials (MEP), cervicomedullary evoked potentials (CMEP), and M waves in the quadriceps. Peripheral and central fatigue were expressed as pre- to postexercise reductions in quadriceps twitch force (ΔQ tw ) and voluntary quadriceps activation (ΔVA). Whereas nonfatiguing cycling caused no measureable fatigue, fatiguing cycling resulted in significant peripheral (ΔQ tw : 42 ± 6%) and central (ΔVA: 4 ± 1%) fatigue. During nonfatiguing cycling, the area of MEPs and CMEPs, normalized to M waves, similarly increased in the quadriceps (∼40%; P fatiguing cycling. As a consequence, the ratio of MEP to CMEP was unchanged during both trials (P > 0.5). Therefore, although increases in muscle activation promote corticospinal excitability via motoneuronal facilitation during nonfatiguing cycling, this effect is abolished during fatigue. We conclude that the unaltered excitability of the corticospinal pathway from start of intense cycling exercise to exhaustion is, in part, determined by inhibitory influences on spinal motoneurons obscuring the facilitating effects of muscle activation.

  15. Introduction to nuclear supply chain management. In the context of fuel cycle strategy from LWR cycle system to FR cycle system

    International Nuclear Information System (INIS)

    Shiotani, Hiroki; Ono, Kiyoshi; Namba, Takashi; Yasumatsu, Naoto; Heta, Masanori

    2011-01-01

    Supply chain management (SCM) is an important technique to maintain supply and demand balance and to achieve total optimization from upstream to downstream in manufacturers' management. One of the major reasons why SCM receives much attention recently is the trend in production and sales systems from 'Push type' to 'Pull type'. 'Push type' can be restated as 'Make to Stock' (MTS). MTS is a type of supply chain in which the production is not connected to actual demand. On the contrary, 'Pull type' can be restated as 'Make to Order' (MTO) in which the production is connected to actual demand. In this paper, the terminologies and ideas of SCM was introduced into the scenario study to give a fresh perspective for considering LWR cycle to FR cycle transition strategies in Japan. Then, an analytical tool (SCM tool) which has been developed by the authors is used to survey Japanese nuclear energy system in transition with the SCM terminologies and viewpoints. When some of the Japanese nuclear fuel cycle strategies and tools are thought back with the framework of SCM, they tend to treat nuclear fuel cycle system as 'Push type' supply chain in their simulations. For example, a reprocessing plant separates SFs (spent fuels) without considering the actual Pu demand. However, because future reprocessing plants and fuel fabrication plants will act as Pu suppliers (front-end facility) to FR as well as back-end facilities of LWRs, the reasonable plant operation principle can be 'Pull type'. The analysis was conducted by the SCM tool to simulate the behaviors of both MTS and MTO type facilities during the LWR to FR transition period. If there are large uncertainties in the Pu demand or the load factor, etc. of future reprocessing plants, SCM framework is beneficial. Furthermore, the realization of MTO type operation by SCM can reduce the recovered Pu stock in spite of the increase of the SF interim storage. As the result of the investigation on the boundary location of 'Push type

  16. Nonlinear solar cycle forecasting: theory and perspectives

    Directory of Open Access Journals (Sweden)

    A. L. Baranovski

    2008-02-01

    Full Text Available In this paper we develop a modern approach to solar cycle forecasting, based on the mathematical theory of nonlinear dynamics. We start from the design of a static curve fitting model for the experimental yearly sunspot number series, over a time scale of 306 years, starting from year 1700 and we establish a least-squares optimal pulse shape of a solar cycle. The cycle-to-cycle evolution of the parameters of the cycle shape displays different patterns, such as a Gleissberg cycle and a strong anomaly in the cycle evolution during the Dalton minimum. In a second step, we extract a chaotic mapping for the successive values of one of the key model parameters – the rate of the exponential growth-decrease of the solar activity during the n-th cycle. We examine piece-wise linear techniques for the approximation of the derived mapping and we provide its probabilistic analysis: calculation of the invariant distribution and autocorrelation function. We find analytical relationships for the sunspot maxima and minima, as well as their occurrence times, as functions of chaotic values of the above parameter. Based on a Lyapunov spectrum analysis of the embedded mapping, we finally establish a horizon of predictability for the method, which allows us to give the most probable forecasting of the upcoming solar cycle 24, with an expected peak height of 93±21 occurring in 2011/2012.

  17. Economic aspects of Dukovany NPP fuel cycle

    International Nuclear Information System (INIS)

    Vesely, P.; Borovicka, M.

    2001-01-01

    The paper discusses some aspects of high burnup program implementation at Dukovany NPP and its influence on the fuel cycle costs. Dukovany internal fuel cycle is originally designed as a three years cycle of the Out-In-In fuel reloading patterns. These reloads are not only uneconomical but they additionally increased the radiation load of the reactor pressure vessel due to high neutron leakage typical for Out-In-In loading pattern. To avoid the high neutron leakage from the core a transition to 4-year fuel cycle is started in 1987. The neutron leakage from the core is sequentially decreased by insertion of older fuel assemblies at the core periphery. Other developments in fuel cycle are: 1) increasing of enrichment in control assemblies (3.6% of U-235); 2) improvement in fuel assembly design (reduce the assembly shroud thickness from 2.1 to 1.6 mm); 3) introduction of Zr spacer grid instead of stainless steel; 4) introduction of new type of assembly with profiled enrichment with average value of 3.82%. Due to increased reactivity of the new assemblies the transition to the partial 5-year fuel cycle is required. Typical fuel loading pattern for 3, 3.5, 4 and 5-year cycles are shown in the presented paper. An evaluation of fuel cost is also discussed by using comparative analysis of different fuel cycle options. The analysis shows that introduction of the high burnup program has decrease relative fuel cycle costs

  18. INTERNAL-CYCLE VARIATION OF SOLAR DIFFERENTIAL ROTATION

    International Nuclear Information System (INIS)

    Li, K. J.; Xie, J. L.; Shi, X. J.

    2013-01-01

    The latitudinal distributions of the yearly mean rotation rates measured by Suzuki in 1998 and 2012 and Pulkkinen and Tuominen in 1998 are utilized to investigate internal-cycle variation of solar differential rotation. The rotation rate at the solar equator seems to have decreased since cycle 10 onward. The coefficient B of solar differential rotation, which represents the latitudinal gradient of rotation, is found to be smaller in the several years after the minimum of a solar cycle than in the several years after the maximum time of the cycle, and it peaks several years after the maximum time of the solar cycle. The internal-cycle variation of the solar rotation rates looks similar in profile to that of the coefficient B. A new explanation is proposed to address such a solar-cycle-related variation of the solar rotation rates. Weak magnetic fields may more effectively reflect differentiation at low latitudes with high rotation rates than at high latitudes with low rotation rates, and strong magnetic fields may more effectively repress differentiation at relatively low latitudes than at high latitudes. The internal-cycle variation is inferred as the result of both the latitudinal migration of the surface torsional pattern and the repression of strong magnetic activity in differentiation.

  19. Theory of limit cycles

    CERN Document Server

    Ye, Yan-Qian; Lo, Chi Y

    1986-01-01

    Over the past two decades the theory of limit cycles, especially for quadratic differential systems, has progressed dramatically in China as well as in other countries. This monograph, updating the 1964 first edition, includes these recent developments, as revised by eight of the author's colleagues in their own areas of expertise. The first part of the book deals with limit cycles of general plane stationary systems, including their existence, nonexistence, stability, and uniqueness. The second section discusses the global topological structure of limit cycles and phase-portraits of quadratic systems. Finally, the last section collects important results that could not be included under the subject matter of the previous two sections or that have appeared in the literature very recently. The book as a whole serves as a reference for college seniors, graduate students, and researchers in mathematics and physics.

  20. Back end of an enduring fuel cycle

    International Nuclear Information System (INIS)

    Pillay, K.K.S.

    1998-03-01

    An enduring nuclear fuel cycle is an essential part of sustainable consumption, the process whereby world's riches are consumed in a responsible manner so that future generations can continue to enjoy at least some of them. In many countries, the goal of sustainable development has focused attention on the benefits of nuclear technologies. However, sustenance of the nuclear fuel cycle is dependent on sensible management of all the resources of the fuel cycle, including energy, spent fuels, and all of its side streams. The nuclear fuel cycle for energy production has suffered many traumas since the mid seventies. The common basis of technologies producing nuclear explosives and consumable nuclear energy has been a preoccupation for some, predicament for others, and a perception problem for many. It is essential to reestablish a reliable back end of the nuclear fuel cycle that can sustain the resource requirements of an enduring full cycle. This paper identifies some pragmatic steps necessary to reverse the trend and to maintain a necessary fuel cycle option for the future

  1. Study of cycle-by-cycle variations of a spark ignition engine fueled with natural gas-hydrogen blends

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jinhua; Chen, Hao; Liu, Bing; Huang, Zuohua [State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi' an Jiaotong University, Xi' an 710049 (China)

    2008-09-15

    Cycle-by-cycle variations of a spark ignition engine fueled with natural gas-hydrogen blends with hydrogen volumetric fraction of 0%, 12%, 23%, 30% and 40% were studied. The effect of hydrogen addition on cycle-by-cycle variations of the natural gas engine was analyzed. The results showed that the peak cylinder pressure, the maximum rate of pressure rise and the indicated mean effective pressure increased and their corresponding cycle-by-cycle variations decreased with the increase of hydrogen fraction at lean mixture operation. The interdependency between the combustion parameters and the corresponding crank angle tended to be strongly correlated with the increase of hydrogen fraction under lean mixture operation. Coefficient of variation of the indicated mean effective pressure gave a low level and is slightly influenced by hydrogen addition under the stoichiometric and relatively rich mixture operation while it decreased remarkably with the increase of hydrogen fraction under the lean mixture operation. The excessive air ratio at CoV{sub imep} = 10% extended to the leaner mixture side with the increase of hydrogen fraction and this indicated that the engine lean operating limit could be extended with hydrogen addition. (author)

  2. Credit cycles and macro fundamentals

    NARCIS (Netherlands)

    Koopman, S.J.; Kraeussl, R.G.W.; Lucas, A.; Monteiro, A.

    2009-01-01

    We use an intensity-based framework to study the relation between macroeconomic fundamentals and cycles in defaults and rating activity. Using Standard and Poor's U.S. corporate rating transition and default data over the period 1980-2005, we directly estimate the default and rating cycle from micro

  3. Towards Life Cycle Sustainability Assessment

    Directory of Open Access Journals (Sweden)

    Marzia Traverso

    2010-10-01

    Full Text Available Sustainability is nowadays accepted by all stakeholders as a guiding principle for both public policy making and corporate strategies. However, the biggest challenge for most organizations remains in the real and substantial implementation of the sustainability concept. The core of the implementation challenge is the question, how sustainability performance can be measured, especially for products and processes. This paper explores the current status of Life Cycle Sustainability Assessment (LCSA for products and processes. For the environmental dimension well established tools like Life Cycle Assessment are available. For the economic and social dimension, there is still need for consistent and robust indicators and methods. In addition to measuring the individual sustainability dimensions, another challenge is a comprehensive, yet understandable presentation of the results. The “Life Cycle Sustainability Dashboard” and the “Life Cycle Sustainability Triangle” are presented as examples for communication tools for both experts and non expert stakeholders.

  4. Ammonium generation during SRAT cycle

    International Nuclear Information System (INIS)

    Hsu, C.W.

    1992-01-01

    During the IDMS noble-metal demonstration runs ammonium nitrate deposition was found in the vessel vent system of the feed preparation area. In the bench-scale experiments of studying the hydrogen generation during the sludge treatment cycle, ammonium ion production was also monitored. It was found that: During a simulation of the DWPF Cold Chemical Runs SRAT cycle no detectable amount of ammonium ions was generated when treating a non-noble-metal containing sludge simulant according to the nitric acid flowsheet. Ammonium ions were generated during the SRAT-SME cycle when treating the noble-metal containing sludge with either formic acid or nitric acid/late-washing PHA. This is due to the reaction between formic acid and nitrate catalyzed by the noble metals in the sludge simulant. Ammonium ion production closely followed the hydrogen evolution from the catalytic decomposition of formic acid. This report summarizes the results of the production of ammonia during the SRAT cycle

  5. Electrofishing power requirements in relation to duty cycle

    Science.gov (United States)

    Miranda, L.E.; Dolan, C.R.

    2004-01-01

    Under controlled laboratory conditions we measured the electrical peak power required to immobilize (i.e., narcotize or tetanize) fish of various species and sizes with duty cycles (i.e., percentage of time a field is energized) ranging from 1.5% to 100%. Electrofishing effectiveness was closely associated with duty cycle. Duty cycles of 10-50% required the least peak power to immobilize fish; peak power requirements increased gradually above 50% duty cycle and sharply below 10%. Small duty cycles can increase field strength by making possible higher instantaneous peak voltages that allow the threshold power needed to immobilize fish to radiate farther away from the electrodes. Therefore, operating within the 10-50% range of duty cycles would allow a larger radius of immobilization action than operating with higher duty cycles. This 10-50% range of duty cycles also coincided with some of the highest margins of difference between the electrical power required to narcotize and that required to tetanize fish. This observation is worthy of note because proper use of duty cycle could help reduce the mortality associated with tetany documented by some authors. Although electrofishing with intermediate duty cycles can potentially increase effectiveness of electrofishing, our results suggest that immobilization response is not fully accounted for by duty cycle because of a potential interaction between pulse frequency and duration that requires further investigation.

  6. Fast power cycle for fusion reactors

    International Nuclear Information System (INIS)

    Powell, J.; Fillo, J.; Makowitz, H.

    1978-01-01

    The unique, deep penetration capability of 14 MeV neutrons produced in DT fusion reactions allows the generation of very high temperature working fluid temperatures in a thermal power cycle. In the FAST (Fusion Augmented Steam Turbine) power cycle steam is directly superheated by the high temperature ceramic refractory interior of the blanket, after being generated by heat extracted from the relatively cool blanket structure. The steam is then passed to a high temperature gas turbine for power generation. Cycle studies have been carried out for a range of turbine inlet temperatures [1600 0 F to 3000 0 F (870 to 1650 0 C)], number of reheats, turbine mechanical efficiency, recuperator effectiveness, and system pressure losses. Gross cycle efficiency is projected to be in the range of 55 to 60%, (fusion energy to electric power), depending on parameters selected. Turbine inlet temperatures above 2000 0 F, while they do increase efficiency somewhat, are not necessarily for high cycle efficiency

  7. Universality, marginal operators, and limit cycles

    International Nuclear Information System (INIS)

    Glazek, Stanislaw D.; Wilson, Kenneth G.

    2004-01-01

    The universality of renormalization-group limit-cycle behavior is illustrated with a simple discrete Hamiltonian model. A nonperturbative renormalization-group equation for the model is soluble analytically at criticality and exhibits one marginal operator (made necessary by the limit cycle) and an infinite set of irrelevant operators. Relevant operators are absent. The model exhibits an infinite series of bound-state energy eigenvalues. This infinite series approaches an exact geometric series as the eigenvalues approach zero--also a consequence of the limit cycle. Wegner's eigenvalues for irrelevant operators are calculated generically for all choices of parameters in the model. We show that Wegner's eigenvalues are independent of location on the limit cycle, in contrast with Wegner's operators themselves, which vary depending on their location on the limit cycle. An example is then used to illustrate numerically how one can tune the initial Hamiltonian to eliminate the first two irrelevant operators. After tuning, the Hamiltonian's bound-state eigenvalues converge much more quickly than otherwise to an exact geometric series

  8. Income inequality and the business cycle

    Directory of Open Access Journals (Sweden)

    Shahee Mostafa

    2015-01-01

    Full Text Available This paper first examines the relationship between ordinary least squares estimators of consumption and investment for 36 selected countries with their respective Gini indices. The analysis shows that income inequality is consistent with a smaller estimator of consumption and a greater estimator of investment. Second, the cycles of GDP, consumption and investment are dated separately to determine how the deepness and duration of cycles of those variables are correlated with the Gini indices of countries. The results show that income inequality leads to a deeper and longer decline of GDP, which causes a greater cumulative income loss of GDP during recession, and a somewhat faster speed of recovery during expansion. Likewise, the result of a correlation between Gini indices and the number of cycles in consumption, investment and GDP indicate that income inequality is associated with a greater number of cycles in consumption and GDP and a lower number of cycles in investment.

  9. A hybrid mammalian cell cycle model

    Directory of Open Access Journals (Sweden)

    Vincent Noël

    2013-08-01

    Full Text Available Hybrid modeling provides an effective solution to cope with multiple time scales dynamics in systems biology. Among the applications of this method, one of the most important is the cell cycle regulation. The machinery of the cell cycle, leading to cell division and proliferation, combines slow growth, spatio-temporal re-organisation of the cell, and rapid changes of regulatory proteins concentrations induced by post-translational modifications. The advancement through the cell cycle comprises a well defined sequence of stages, separated by checkpoint transitions. The combination of continuous and discrete changes justifies hybrid modelling approaches to cell cycle dynamics. We present a piecewise-smooth version of a mammalian cell cycle model, obtained by hybridization from a smooth biochemical model. The approximate hybridization scheme, leading to simplified reaction rates and binary event location functions, is based on learning from a training set of trajectories of the smooth model. We discuss several learning strategies for the parameters of the hybrid model.

  10. Feasibility study on tandem fuel cycle

    International Nuclear Information System (INIS)

    Han, P.S.; Suh, I.S.; Rim, C.S.; Kim, B.K.; Suh, K.S.; Ro, S.K.; Juhn, P.I.; Kim, S.Y.

    1983-01-01

    The objective of this feasibility study is to review and assess the current state of technology concerning the tandem fuel cycle. Based on the results from this study, a long-term development plan suitable for Korea has been proposed for this cycle, i.e., the PWR → CANDU tandem fuel cycle which used plutonium and uranium, recovered from spent PWR fuel by co-processing, as fuel material for CANDU reactors. (Author)

  11. Utilization of Indonesia's Hot Spring Sources for Electricity using Kalina Cycle and Organic Rankine Cycle

    Science.gov (United States)

    Prabumukti, Grano; Purwanto; Widodo, Wahyu

    2018-02-01

    Indonesia posses 40% of the world's geothermal energy sources. The existence of hydrothermal sources is usually characterized by their surface manifestations such as hot springs, geysers and fumarole. Hot spring has a potential to be used as a heat source to generate electricity especially in a rural and isolated area. Hot springs can be converted into electricity by binary thermodynamic cycles such as Kalina cycle and ORC. The aim of this study is to obtain the best performances of cycle configuration and the potential power capacity. Simulation is conducted using UNISIM software with working fluid and its operating condition as the decision variables. The simulation result shows that R1234yf and propene with simple ORC as desired working fluid and cycle configuration. It reaches a maximum thermal efficiency up to 9.6% with a specific turbine inlet pressure. Higher temperature heat source will result a higher thermal efficiency‥ Cycle thermal efficiency varies from 4.7% to 9.6% depends on source of hot spring temperature. Power capacity that can be generated using Indonesia's hot spring is ranged from 2 kWe to 61.2 kWe. The highest capacity located in Kawah Sirung and the least located in Kaendi.

  12. Quantifying fluctuations in reversible enzymatic cycles and clocks

    Science.gov (United States)

    Wierenga, Harmen; ten Wolde, Pieter Rein; Becker, Nils B.

    2018-04-01

    Biochemical reactions are fundamentally noisy at a molecular scale. This limits the precision of reaction networks, but it also allows fluctuation measurements that may reveal the structure and dynamics of the underlying biochemical network. Here, we study nonequilibrium reaction cycles, such as the mechanochemical cycle of molecular motors, the phosphorylation cycle of circadian clock proteins, or the transition state cycle of enzymes. Fluctuations in such cycles may be measured using either of two classical definitions of the randomness parameter, which we show to be equivalent in general microscopically reversible cycles. We define a stochastic period for reversible cycles and present analytical solutions for its moments. Furthermore, we associate the two forms of the randomness parameter with the thermodynamic uncertainty relation, which sets limits on the timing precision of the cycle in terms of thermodynamic quantities. Our results should prove useful also for the study of temporal fluctuations in more general networks.

  13. Economic growth and business cycles

    NARCIS (Netherlands)

    Canton, E.J.F.

    1997-01-01

    This thesis contains five essays on economic growth and business cycles. The main focus is on the interaction between economic growth and the cycle: is cyclical variability good or bad for the long-run rate of economic growth? The introduction aims to provide some empirical evidence for an

  14. Nuclear fuel cycle risk assessment: survey and computer compilation of risk-related literature. [Once-through Cycle and Plutonium Recycle

    Energy Technology Data Exchange (ETDEWEB)

    Yates, K.R.; Schreiber, A.M.; Rudolph, A.W.

    1982-10-01

    The US Nuclear Regulatory Commission has initiated the Fuel Cycle Risk Assessment Program to provide risk assessment methods for assistance in the regulatory process for nuclear fuel cycle facilities other than reactors. Both the once-through cycle and plutonium recycle are being considered. A previous report generated by this program defines and describes fuel cycle facilities, or elements, considered in the program. This report, the second from the program, describes the survey and computer compilation of fuel cycle risk-related literature. Sources of available information on the design, safety, and risk associated with the defined set of fuel cycle elements were searched and documents obtained were catalogued and characterized with respect to fuel cycle elements and specific risk/safety information. Both US and foreign surveys were conducted. Battelle's computer-based BASIS information management system was used to facilitate the establishment of the literature compilation. A complete listing of the literature compilation and several useful indexes are included. Future updates of the literature compilation will be published periodically. 760 annotated citations are included.

  15. Increase of carbon cycle feedback with climate sensitivity: results from a coupled climate and carbon cycle model

    International Nuclear Information System (INIS)

    Govindasamy, B.; Thompson, S.; Mirin, A.; Wickett, M.; Caldeira, K.; Delire, C.

    2005-01-01

    Coupled climate and carbon cycle modelling studies have shown that the feedback between global warming and the carbon cycle, in particular the terrestrial carbon cycle, could accelerate climate change and result in greater warming. In this paper we investigate the sensitivity of this feedback for year 2100 global warming in the range of 0 to 8 K. Differing climate sensitivities to increased CO 2 content are imposed on the carbon cycle models for the same emissions. Emissions from the SRES A2 scenario are used. We use a fully coupled climate and carbon cycle model, the INtegrated Climate and CArbon model (INCCA), the NCAR/DOE Parallel Climate Model coupled to the IBIS terrestrial biosphere model and a modified OCMIP ocean biogeochemistry model. In our integrated model, for scenarios with year 2100 global warming increasing from 0 to 8 K, land uptake decreases from 47% to 29% of total CO 2 emissions. Due to competing effects, ocean uptake (16%) shows almost no change at all. Atmospheric CO 2 concentration increases are 48% higher in the run with 8 K global climate warming than in the case with no warming. Our results indicate that carbon cycle amplification of climate warming will be greater if there is higher climate sensitivity to increased atmospheric CO 2 content; the carbon cycle feedback factor increases from 1.13 to 1.48 when global warming increases from 3.2 to 8 K

  16. Estrogen receptor alpha is cell cycle-regulated and regulates the cell cycle in a ligand-dependent fashion.

    Science.gov (United States)

    JavanMoghadam, Sonia; Weihua, Zhang; Hunt, Kelly K; Keyomarsi, Khandan

    2016-06-17

    Estrogen receptor alpha (ERα) has been implicated in several cell cycle regulatory events and is an important predictive marker of disease outcome in breast cancer patients. Here, we aimed to elucidate the mechanism through which ERα influences proliferation in breast cancer cells. Our results show that ERα protein is cell cycle-regulated in human breast cancer cells and that the presence of 17-β-estradiol (E2) in the culture medium shortened the cell cycle significantly (by 4.5 hours, P cycle duration were observed in the S and G2/M phases, whereas the G1 phase was indistinguishable under liganded and unliganded conditions. In addition, ERα knockdown in MCF-7 cells accelerated mitotic exit, whereas transfection of ERα-negative MDA-MB-231 cells with exogenous ERα significantly shortened the S and G2/M phases (by 9.1 hours, P cycle progression through the S and G2/M phases than fulvestrant does, presumably because of the destabilizing effect of fulvestrant on ERα protein. Together, these results show that ERα modulates breast cancer cell proliferation by regulating events during the S and G2/M phases of the cell cycle in a ligand-dependent fashion. These results provide the rationale for an effective treatment strategy that includes a cell cycle inhibitor in combination with a drug that lowers estrogen levels, such as an aromatase inhibitor, and an antiestrogen that does not result in the degradation of ERα, such as tamoxifen.

  17. Do donor oocyte cycles comply with ASRM/SART embryo transfer guidelines? An analysis of 13,393 donor cycles from the SART registry.

    Science.gov (United States)

    Acharya, Kelly S; Keyhan, Sanaz; Acharya, Chaitanya R; Yeh, Jason S; Provost, Meredith P; Goldfarb, James M; Muasher, Suheil J

    2016-09-01

    To analyze donor oocyte cycles in the Society for Assisted Reproductive Technology (SART) registry to determine: 1) how many cycles complied with the 2009 American Society for Reproductive Medicine/SART embryo transfer guidelines; and 2) cycle outcomes according to the number of embryos transferred. For donor oocyte IVF with donor age cycles from 2011 to 2012. Embryos transferred in donor IVF cycles. Percentage of compliant cycles, multiple pregnancy rate. There were 3,157 donor cleavage-stage transfers and 10,236 donor blastocyst transfers. In the cleavage-stage cycles, 88% met compliance criteria. The multiple pregnancy rate (MPR) was significantly higher in the noncompliant cycles. In a subanalysis of compliant cleavage-stage cycles, 91% transferred two embryos and only 9% single embryos. In those patients transferring two embryos, the MPR was significantly higher (33% vs. 1%). In blastocyst transfers, only 28% of the cycles met compliance criteria. The MPR was significantly higher in the noncompliant blastocyst cohort at 53% (compared with 2% in compliant cycles). The majority of donor cleavage-stage transfers are compliant with current guidelines, but the transfer of two embryos results in a significantly higher MPR compared with single-embryo transfer. The majority of donor blastocyst cycles are noncompliant, which appears to be driving an unacceptably high MPR in these cycles. Copyright © 2016 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

  18. Seasonal variation in assisted conception cycles and the influence of photoperiodism on outcome in in vitro fertilization cycles.

    Science.gov (United States)

    Wood, Simon; Quinn, Alison; Troupe, Stephen; Kingsland, Charles; Lewis-Jones, Iwan

    2006-12-01

    The effect of seasonality and daylight length on mammalian reproduction leading to spring births has been well established, and is known as photoperiodism. In assisted reproduction there is much greater uncertainty as to the effect of seasonality. This was a 4-year retrospective analysis of 2709 standardised cycles of IVF/ICSI. Data was analysed with regard to the 1642 cycles occurring during the months of extended daylight (Apr-Sept) and those 1067 cycles during winter months of restricted light length (Oct-Mar). The results showed that there was significant improvement in assisted conception outcomes in cycles performed in summer (lighter) months with more efficient ovarian stimulation 766iu v880iu/per oocyte retrieved (p=0.006). There was similarly a significantly improved implantation rate per embryo transferred 11.42% vs 9.35% (p=0.011) and greater clinical pregnancy rate 20% vs 15% (p=0.0033) during summer cycles. This study appears to demonstrate a significant benefit of increased daylight length on outcomes of IVF/ICSI cycles. Whilst the exact mechanism of this is unclear, it would seem probable that melatonin may have actions at multiple sites and on multiple levels of the reproductive tract, and may exert a more profound effect on outcomes of assisted conception cycles than has been previously considered.

  19. Combined Turbine and Cycle Optimization for Organic Rankine Cycle Power Systems—Part B

    DEFF Research Database (Denmark)

    La Seta, Angelo; Meroni, Andrea; Andreasen, Jesper Graa

    2016-01-01

    Organic Rankine cycle (ORC) power systems have recently emerged as promising solutions for waste heat recovery in low- and medium-size power plants. Their performance and economic feasibility strongly depend on the expander. The design process and efficiency estimation are particularly challenging...... due to the peculiar physical properties of the working fluid and the gas-dynamic phenomena occurring in the machine. Unlike steam Rankine and Brayton engines, organic Rankine cycle expanders combine small enthalpy drops with large expansion ratios. These features yield turbine designs with few highly...... is the preliminary design of an organic Rankine cycle turbogenerator to increase the overall energy efficiency of an offshore platform. For an increase in expander pressure ratio from 10 to 35, the results indicate up to 10% point reduction in expander performance. This corresponds to a relative reduction in net...

  20. Frozen-thawed embryo transfer in a natural or mildly hormonally stimulated cycle in women with regular ovulatory cycles: a RCT.

    Science.gov (United States)

    Peeraer, Karen; Couck, Isabelle; Debrock, Sophie; De Neubourg, Diane; De Loecker, Peter; Tomassetti, Carla; Laenen, Annouschka; Welkenhuysen, Myriam; Meeuwis, Luc; Pelckmans, Sofie; Meuleman, Christel; D'Hooghe, Thomas

    2015-11-01

    Can ovarian stimulation with low dose hMG improve the implantation rate (IR) per frozen-thawed embryo transferred (FET) when compared with natural cycle in an FET programme in women with a regular ovulatory cycle? Both IR and live birth rate (LBR) per FET were similar in the group with mild ovarian stimulation and the natural cycle group. Different cycle regimens for endometrial preparation are used prior to FET: spontaneous ovulatory cycles, cycles with artificial endometrial preparation using estrogen and progesterone hormones, and cycles stimulated with gonadotrophins or clomiphene citrate. At present, it is not clear which regimen results in the highest IR or LBR. More specifically, there are no RCTs in ovulatory women comparing reproductive outcome after FET during a natural cycle and during a hormonally stimulated cycle. A total of 410 women scheduled for FET during 579 cycles (December 2003-September 2013) were enrolled in an open-label RCT to natural cycle (NC FET group, n = 291) or to a cycle hormonally stimulated with s.c. gonadotrophins (hMG FET group, 37.5-75 IU per day, n = 288). A total of 672 embryos were transferred during 434 cycles (332 embryos and 213 cycles in the NC FET group; 340 embryos and 221 cycles in the hMG FET group). Assuming a = 0.05 and 80% power, it was calculated that 219 frozen-thawed embryos were required for transfer in each group to demonstrate a difference of 10% in IR. Women were eligible according to the following inclusion criteria: regular ovulatory cycle, female age ≥21 years and ≤45 years, informed consent. FET cycles with preimplantation genetic screening were excluded. The primary outcome was IR per embryo transferred. Secondary outcomes included IR with fetal heart beat (FHB), LBR per embryo transferred and endometrial thickness on the day of hCG administration. Statistical analysis was by intention to treat and controlled for the presence of multiple measures, as eligible women could be randomized in more than

  1. Impact of cycling cells and cell cycle regulation on Hydra regeneration.

    Science.gov (United States)

    Buzgariu, Wanda; Wenger, Yvan; Tcaciuc, Nina; Catunda-Lemos, Ana-Paula; Galliot, Brigitte

    2018-01-15

    Hydra tissues are made from three distinct populations of stem cells that continuously cycle and pause in G2 instead of G1. To characterize the role of cell proliferation after mid-gastric bisection, we have (i) used flow cytometry and classical markers to monitor cell cycle modulations, (ii) quantified the transcriptomic regulations of 202 genes associated with cell proliferation during head and foot regeneration, and (iii) compared the impact of anti-proliferative treatments on regeneration efficiency. We confirm two previously reported events: an early mitotic wave in head-regenerating tips, when few cell cycle genes are up-regulated, and an early-late wave of proliferation on the second day, preceded by the up-regulation of 17 cell cycle genes. These regulations appear more intense after mid-gastric bisection than after decapitation, suggesting a position-dependent regulation of cell proliferation during head regeneration. Hydroxyurea, which blocks S-phase progression, delays head regeneration when applied before but not after bisection. This result is consistent with the fact that the Hydra central region is enriched in G2-paused adult stem cells, poised to divide upon injury, thus forming a necessary constitutive pro-blastema. However a prolonged exposure to hydroxyurea does not block regeneration as cells can differentiate apical structures without traversing S-phase, and also escape in few days the hydroxyurea-induced S-phase blockade. Thus Hydra head regeneration, which is a fast event, is highly plastic, relying on large stocks of adult stem cells paused in G2 at amputation time, which immediately divide to proliferate and/or differentiate apical structures even when S-phase is blocked. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  2. Thorium fuel cycle - Potential benefits and challenges

    International Nuclear Information System (INIS)

    2005-05-01

    There has been significant interest among Member States in developing advanced and innovative technologies for safe, proliferation resistant and economically efficient nuclear fuel cycles, while minimizing waste and environmental impacts. This publication provides an insight into the reasons for renewed interest in the thorium fuel cycle, different implementation scenarios and options for the thorium cycle and an update of the information base on thorium fuels and fuel cycles. The present TECDOC focuses on the upcoming thorium based reactors, current information base, front and back end issues, including manufacturing and reprocessing of thorium fuels and waste management, proliferation-resistance and economic issues. The concluding chapter summarizes future prospects and recommendations pertaining to thorium fuels and fuel cycles

  3. Development of FR fuel cycle in japan (1) development scope of fuel cycle technology

    International Nuclear Information System (INIS)

    Nakamura, H.; Funasaka, H.; Namekawa, T.

    2008-01-01

    A fast reactor (FR) cycle has a potential to realize a sustainable energy supply system that is harmonized with environment by fully recycling both uranium (U) and transuranium (TRU) elements. In Japan, a Feasibility Study on Commercialized FR Cycle Systems (FS) was launched in July 1999, and through two different study phases, a final report was presented in 2006. As a result of FS, a combined system of sodium-cooled FR with mixed-oxide (MOX) fuel, advanced aqueous reprocessing and simplified pelletizing fuel fabrication was considered to be most promising for commercialization. The advanced aqueous reprocessing system, which is called the New Extraction system for TRU recovery (NEXT), consists of a U crystallization process for the bulk of U recovery, a simplified solvent extraction process for residual U, plutonium (Pu) and neptunium (Np) without Pu partitioning and purification, and a process for recovering americium (Am) and curium (Cm) from the raffinate. The ratio of Pu/U concentration in the mother solution after crystallization is adequate for MOX fuel fabrication, and thus complicated powder mixing processes for adjusting Pu content in MOX fuel can be eliminated in the subsequent simplified fuel fabrication system. In this system, lubricant-mixing process can also be eliminated by adopting the advanced technology in which lubricant is coated on the inner surface of a die before fuel powder supply. Such a simplification could help us overcoming the difficulty to treat MA bearing fuel powders in a hot cell. Ministry of Education, Culture, Sports, Science and Technology (MEXT) reviewed these results of FS in 2006 and identified the most promising FR cycle concept proposed in the FS phase II study as a mainline choice for commercialization. According to such a governmental assessment, R and D activities of FR cycle systems were decided to be concentrated mainly to the innovative technology development for the mainline concept. The stage of R and D project was

  4. Solar-cycle period-amplitude relation as evidence of hysteresis of the solar-cycle nonlinear magnetic oscillation and the long-term (55 year) cyclic modulation

    International Nuclear Information System (INIS)

    Yoshimura, H.

    1979-01-01

    A new dynamical model of the solar cycle has predicted that the cycle should have a hysteretic nature: the behavior of each 11 year cycle should depend on previous cycles. In the light of this new understanding of the dynamical mechanism of the solar cycle, Waldmeier's (hypothetical) law was examined as a yet unexplained characteristic of the cycle by studying the observed sunspot frequency curve. Contrary to this hypothetical law, however, it was found that sunspot cycle curves did not form a single-parameter family characterized by the maximum amplitude of the cycle. The evolutionary trajectories in period-amplitude phase space verified the hysteretic nature of the observed cycle and revealed long-term (55 year instead of the previously claimed 80 year) periodic modulations, called here 55 year grand cycles. Each 55 year grand cycle forms a loop in the phase space, and the characteristics of each 11 year cycle depend on its position in the ascending or descending phase of the grand cycle. This new law was analyzed by the nonlinear multiple-period dynamo oscillation model which has predicted the hysteretic nature. The era from cycle 11 to cycle 15 turned out to be an anomalous one characterized by alternating amplitudes for odd and even cycles. Cycles 16--20 seem to constitute one grand cycle. If this is true, cycle 21 would be the beginning of another grand maximum and the model predicts that its duration would be short

  5. Hamiltonian cycles in polyhedral maps

    Indian Academy of Sciences (India)

    We present a necessary and sufficient condition for existence of a contractible, non-separating and non-contractible separating Hamiltonian cycle in the edge graph of polyhedral maps on surfaces.We also present algorithms to construct such cycles whenever it exists where one of them is linear time and another is ...

  6. Overlooked runaway feedback in the marine nitrogen cycle: the vicious cycle

    Directory of Open Access Journals (Sweden)

    A. Landolfi

    2013-03-01

    Full Text Available The marine nitrogen (N inventory is thought to be stabilized by negative feedback mechanisms that reduce N inventory excursions relative to the more slowly overturning phosphorus inventory. Using a global biogeochemical ocean circulation model we show that negative feedbacks stabilizing the N inventory cannot persist if a close spatial association of N2 fixation and denitrification occurs. In our idealized model experiments, nitrogen deficient waters, generated by denitrification, stimulate local N2 fixation activity. But, because of stoichiometric constraints, the denitrification of newly fixed nitrogen leads to a net loss of N. This can enhance the N deficit, thereby triggering additional fixation in a vicious cycle, ultimately leading to a runaway N loss. To break this vicious cycle, and allow for stabilizing negative feedbacks to occur, inputs of new N need to be spatially decoupled from denitrification. Our idealized model experiments suggest that factors such as iron limitation or dissolved organic matter cycling can promote such decoupling and allow for negative feedbacks that stabilize the N inventory. Conversely, close spatial co-location of N2 fixation and denitrification could lead to net N loss.

  7. Life cycle assessment : Past, present, and future

    NARCIS (Netherlands)

    Guinée, Jeroen B.; Heijungs, Reinout; Huppes, Gjalt; Zamagni, Alessandra; Masoni, Paolo; Buonamici, Roberto; Ekvall, Tomas; Rydberg, Tomas

    2011-01-01

    Environmental life cycle assessment (LCA) has developed fast over the last three decades. Whereas LCA developed from merely energy analysis to a comprehensive environmental burden analysis in the 1970s, full-fledged life cycle impact assessment and life cycle costing models were introduced in the

  8. Comparative assessment of nuclear fuel cycles. Light-water reactor once-through, classical fast breeder reactor, and symbiotic fast breeder reactor cycles

    International Nuclear Information System (INIS)

    Hardie, R.W.; Barrett, R.J.; Freiwald, J.G.

    1980-06-01

    The object of the Alternative Nuclear Fuel Cycle Study is to perform comparative assessments of nuclear power systems. There are two important features of this study. First, this evaluation attempts to encompass the complete, integrated fuel cycle from mining of uranium ore to disposal of waste rather than isolated components. Second, it compares several aspects of each cycle - energy use, economics, technological status, proliferation, public safety, and commercial potential - instead of concentrating on one or two assessment areas. This report presents assessment results for three fuel cycles. These are the light-water reactor once-through cycle, the fast breeder reactor on the classical plutonium cycle, and the fast breeder reactor on a symbiotic cycle using plutonium and 233 U as fissile fuels. The report also contains a description of the methodology used in this assessment. Subsequent reports will present results for additional fuel cycles

  9. Epigenetic dynamics across the cell cycle

    DEFF Research Database (Denmark)

    Kheir, Tony Bou; Lund, Anders H.

    2010-01-01

    Progression of the mammalian cell cycle depends on correct timing and co-ordination of a series of events, which are managed by the cellular transcriptional machinery and epigenetic mechanisms governing genome accessibility. Epigenetic chromatin modifications are dynamic across the cell cycle...... a correct inheritance of epigenetic chromatin modifications to daughter cells. In this chapter, we summarize the current knowledge on the dynamics of epigenetic chromatin modifications during progression of the cell cycle....

  10. Analysis of Maisotsenko open gas turbine bottoming cycle

    International Nuclear Information System (INIS)

    Saghafifar, Mohammad; Gadalla, Mohamed

    2015-01-01

    Maisotsenko gas turbine cycle (MGTC) is a recently proposed humid air turbine cycle. An air saturator is employed for air heating and humidification purposes in MGTC. In this paper, MGTC is integrated as the bottoming cycle to a topping simple gas turbine as Maisotsenko bottoming cycle (MBC). A thermodynamic optimization is performed to illustrate the advantages and disadvantages of MBC as compared with air bottoming cycle (ABC). Furthermore, detailed sensitivity analysis is reported to present the effect of different operating parameters on the proposed configurations' performance. Efficiency enhancement of 3.7% is reported which results in more than 2600 tonne of natural gas fuel savings per year. - Highlights: • Developed an accurate air saturator model. • Introduced Maisotsenko bottoming cycle (MBC) as a power generation cycle. • Performed Thermodynamic optimization for MBC and air bottoming cycle (ABC). • Performed detailed sensitivity analysis for MBC under different operating conditions. • MBC has higher efficiency and specific net work output as compared to ABC

  11. Resonance – Journal of Science Education | News

    Indian Academy of Sciences (India)

    Annual Meetings · Mid Year Meetings · Discussion Meetings · Public Lectures · Lecture Workshops · Refresher Courses · Symposia · Live Streaming. Home; Journals; Resonance – Journal of Science Education; Volume 22; Issue 12. Pythagorean Means and Carnot Machines: When Music Meets Heat. Ramandeep S Johal.

  12. The remote ischemic preconditioning algorithm: effect of number of cycles, cycle duration and effector organ mass on efficacy of protection.

    Science.gov (United States)

    Johnsen, Jacob; Pryds, Kasper; Salman, Rasha; Løfgren, Bo; Kristiansen, Steen Buus; Bøtker, Hans Erik

    2016-03-01

    Remote ischemic preconditioning (rIPC), induced by cycles of transient limb ischemia and reperfusion (IR), is cardioprotective. The optimal rIPC-algorithm is not established. We investigated the effect of cycle numbers and ischemia duration within each rIPC-cycle and the influence of effector organ mass on the efficacy of cardioprotection. Furthermore, the duration of the early phase of protection by rIPC was investigated. Using a tourniquet tightened at the inguinal level, we subjected C57Bl/6NTac mice to intermittent hind-limb ischemia and reperfusion. The rIPC-protocols consisted of (I) two, four, six or eight cycles, (II) 2, 5 or 10 min of ischemia in each cycle, (III) single or two hind-limb occlusions and (IV) 0.5, 1.5, 2.0 or 2.5 h intervals from rIPC to index cardiac ischemia. All rIPC algorithms were followed by 5 min of reperfusion. The hearts were subsequently exposed to 25 min of global ischemia and 60 min of reperfusion in an ex vivo Langendorff model. Cardioprotection was evaluated by infarct size and post-ischemic hemodynamic recovery. Four to six rIPC cycles yielded significant cardioprotection with no further protection by eight cycles. Ischemic cycles lasting 2 min offered the same protection as cycles of 5 min ischemia, whereas prolonged cycles lasting 10 min abrogated protection. One and two hind-limb preconditioning were equally protective. In our mouse model, the duration of protection by rIPC was 1.5 h. These findings indicate that the number and duration of cycles rather than the tissue mass exposed to rIPC determines the efficacy of rIPC.

  13. Characteristics of fuel cycle waste

    International Nuclear Information System (INIS)

    Aquilina, C.A.; Everette, S.E.

    1982-01-01

    The Low-Level Waste Management System started in 1979 to describe and model the existing commercial low-level waste management system. The system description produced is based on the identification of the different elements making up both the fuel and non-fuel cycle and their relationships to each other. A systems model based on the system description can accurately reflect the flow of low-level waste from generator to disposal site and is only limited by the reliability of the information it uses. For both the fuel cycle and non-fuel cycle large quantities of information is required in order to allow the system to operate at its full potential. Work is ongoing to collect this information. Significant progress is being made in the fuel cycle area primarily because the majority of fuel cycle low-level radioactive waste is produced by commercial power reactor plant operations. The Low-Level Waste Management system is only beginning to derive the benefits to be obtained from an accurate low-level waste management information system. As data is verified and analyzed, results on a national as well as individual organization level will be gained. Comparisons to previous studies will be made. Accurate projections of waste volumes and activities to be produced, projected impacts of waste streams of treatment or management changes are only examples of information to be produced. 1 figure, 1 table

  14. Bifuel coal-gas combined cycles

    International Nuclear Information System (INIS)

    Chmielniak, Tadeusz; Kotowicz, Janusz; Lyczko, Jacek

    1997-01-01

    This paper describes basic ways of realization of bi fuel cool-gas combined cycles. The criterion of classification of the systems specification is a joint of the gas pail with the steam part: a) The gas turbine flue gases are introduced into the steam boiler combustion chamber (the serial, hot wind box). b) Bypass of the beat exchangers at the steam turbine unit and/or the steam boiler, by use the waste heat exchangers, or waste boiler at the gas turbine unit (the parallel-coupled). c) The mixed, it's a combination of the two upper. The analysis of the parallel system has been specially presented. In derived formulas for the total efficiency of the bi fuel parallel combined cycle balance equations have been used. This formulas can be used for planning new combined cycle power plants and for modernization existing steam power plants. It was made a discussion about influence of the ratio the gas and the steam turbine electric power on the cycle efficiency in care of the full and the part load of the bi fuel combined cycle power plant. The various systems of the joint of the gas part with the steam part have been examined. The selected results of the calculations have been attached. The models and the numerical simulations have been based on data from the existing steam power plants and real gas turbine units. (Author)

  15. 40 CFR 1033.520 - Alternative ramped modal cycles.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Alternative ramped modal cycles. 1033... cycles. (a) Locomotive testing over a ramped modal cycle is intended to improve measurement accuracy at... locomotive notch settings. Ramped modal cycles combine multiple test modes of a discrete-mode steady-state...

  16. 40 CFR 1033.530 - Duty cycles and calculations.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Duty cycles and calculations. 1033.530... CONTROLS CONTROL OF EMISSIONS FROM LOCOMOTIVES Test Procedures § 1033.530 Duty cycles and calculations. This section describes how to apply the duty cycle to measured emission rates to calculate cycle...

  17. Developing Asset Life Cycle Management capabilities through the implementation of Asset Life Cycle Plans – an Action Research project

    OpenAIRE

    Ruitenburg, Richard; Braaksma, Anne Johannes Jan

    2017-01-01

    Asset Life Cycle Management is a strategic approach to managing physical assets over their complete life cycle. However, the literature and the recent ISO 55,000 standard do not offer guidance as to how to develop such an approach. This paper investigates the main capabilities for Asset Life Cycle Management by means of a four year Action Research project implementing Asset Life Cycle Plans. Five main capabilities emerged: 1. strategic information use; 2. alignment of operations and strategy;...

  18. Life cycle sustainability assessment of chemical processes

    DEFF Research Database (Denmark)

    Xu, Di; Lv, Liping; Ren, Jingzheng

    2017-01-01

    In this study, an integrated vector-based three-dimensional (3D) methodology for the life cycle sustainability assessment (LCSA) of chemical process alternatives is proposed. In the methodology, a 3D criteria assessment system is first established by using the life cycle assessment, the life cycl...

  19. Characterization of oocyte retrieval cycles with empty zona pellucida.

    Science.gov (United States)

    Oride, Aki; Kanasaki, Haruhiko; Hara, Tomomi; Ohta, Hiroko; Kyo, Satoru

    2018-01-01

    To identify the factors that characterize cycles with empty zona pellucida (EZP). Thirty-six oocyte retrieval cycles from which EZP were collected and another 36 cycles from which no EZP was collected were compared. The patients were divided into three groups: those with no EZP collected during any cycle, those with EZP collected during all cycles, and those experiencing cycles both with and without EZP. The mean number of oocytes collected per cycle was higher in the cycles with EZP than without EZP. The fertilization rate of the collected oocytes and the rate of good embryo formation were significantly lower in the cycles with EZP. No significant difference was observed between the three groups in terms of age, number of oocytes collected, or hormone levels before and after the oocyte retrieval. The fertilization and pregnancy rates were highest in the patients with no EZP being collected during any cycle, followed by those experiencing cycles both with and without EZP, and then by those with EZP collected during all cycles. The observation of lower fertilization, poor embryo formation, and a low pregnancy rate in the patients with EZP suggests the poor quality of oocytes that were collected with EZP in the same cycle.

  20. Efficiency versus speed in quantum heat engines: Rigorous constraint from Lieb-Robinson bound

    Science.gov (United States)

    Shiraishi, Naoto; Tajima, Hiroyasu

    2017-08-01

    A long-standing open problem whether a heat engine with finite power achieves the Carnot efficiency is investgated. We rigorously prove a general trade-off inequality on thermodynamic efficiency and time interval of a cyclic process with quantum heat engines. In a first step, employing the Lieb-Robinson bound we establish an inequality on the change in a local observable caused by an operation far from support of the local observable. This inequality provides a rigorous characterization of the following intuitive picture that most of the energy emitted from the engine to the cold bath remains near the engine when the cyclic process is finished. Using this description, we prove an upper bound on efficiency with the aid of quantum information geometry. Our result generally excludes the possibility of a process with finite speed at the Carnot efficiency in quantum heat engines. In particular, the obtained constraint covers engines evolving with non-Markovian dynamics, which almost all previous studies on this topic fail to address.