International Nuclear Information System (INIS)
Anderson, B.
2000-01-01
The article discusses the identification of efficiencies that can minimise transaction costs in energy trading and marketing. The article describes what is meant by 'trade management'. It is argued that a trade management system should be able to dovetail with existing or future ERP, advanced risk management, and financial management systems, to provide total enterprise integration. With the right trade management systems, traders have all the necessary information to help them manage exposure to financial risks in a world where energy trading companies are forced to accept very small margins. A trade management system can cover many aspects of a business including the winning of contracts for transportation deals, including rail, car, truck, barge and pipeline. There appears to be unprecedented opportunities for companies specialising in development and provision of trade management systems
Energy Technology Data Exchange (ETDEWEB)
Anderson, B. [SolArc, Inc. (United States)
2000-09-01
The article discusses the identification of efficiencies that can minimise transaction costs in energy trading and marketing. The article describes what is meant by 'trade management'. It is argued that a trade management system should be able to dovetail with existing or future ERP, advanced risk management, and financial management systems, to provide total enterprise integration. With the right trade management systems, traders have all the necessary information to help them manage exposure to financial risks in a world where energy trading companies are forced to accept very small margins. A trade management system can cover many aspects of a business including the winning of contracts for transportation deals, including rail, car, truck, barge and pipeline. There appears to be unprecedented opportunities for companies specialising in development and provision of trade management systems.
Fine modeling of energy exchanges between buildings and urban atmosphere
International Nuclear Information System (INIS)
Daviau-Pellegrin, Noelie
2016-01-01
This thesis work is about the effect of buildings on the urban atmosphere and more precisely the energetic exchanges that take place between these two systems. In order to model more finely the thermal effects of buildings on the atmospheric flows in simulations run under the CFD software Code-Saturne, we proceed to couple this tool with the building model BuildSysPro. This library is run under Dymola and can generate matrices describing the building thermal properties that can be used outside this software. In order to carry out the coupling, we use these matrices in a code that allows the building thermal calculations and the CFD to exchange their results. After a review about the physical phenomena and the existing models, we explain the interactions between the atmosphere and the urban elements, especially buildings. The latter can impact the air flows dynamically, as they act as obstacles, and thermally, through their surface temperatures. At first, we analyse the data obtained from the measurement campaign EM2PAU that we use in order to validate the coupled model. EM2PAU was carried out in Nantes in 2011 and represents a canyon street with two rows of four containers. Its distinctive feature lies in the simultaneous measurements of the air and wall temperatures as well as the wind speeds with anemometers located on a 10 m-high mast for the reference wind and on six locations in the canyon. This aims for studying the thermal influence of buildings on the air flows. Then the numerical simulations of the air flows in EM2PAU is carried out with different methods that allow us to calculate or impose the surface temperature we use for each of the container walls. The first method consists in imposing their temperatures from the measurements. For each wall, we set the temperature to the surface temperature that was measured during the EM2PAU campaign. The second method involves imposing the outdoor air temperature that was measured at a given time to all the
High energy charge exchange np and antipp scattering using the dual fermion model
International Nuclear Information System (INIS)
Weigt, G.
1976-01-01
The five independent helicity amplitudes Phisub(i)(s, t) calculated by Mandelstam from the Neveu-Schwarz-Ramond model for fermion-antifermion scattering are used in the Regge limit for a phenomenological description of high energy np and antipp charge exchange scattering. A forward spike which widens with increasing energy as well as an energy dependence changing from lower to higher energy data are reproduced by these non-evasive dual Born amplitudes using π, A 2 and rho Regge pole t-channel exchanges. (author)
Energy exchange analysis in droplet dynamics via the Navier–Stokes–Cahn–Hilliard model
Espath, L. F. R.
2016-05-23
We develop the energy budget equation of the coupled Navier-Stokes-Cahn-Hilliard (NSCH) system. We use the NSCH equations to model the dynamics of liquid droplets in a liquid continuum. Buoyancy effects are accounted for through the Boussinesq assumption. We physically interpret each quantity involved in the energy exchange to gain further insight into the model. Highly resolved simulations involving density-driven flows and the merging of droplets allow us to analyse these energy budgets. In particular, we focus on the energy exchanges when droplets merge, and describe flow features relevant to this phenomenon. By comparing our numerical simulations to analytical predictions and experimental results available in the literature, we conclude that modelling droplet dynamics within the framework of NSCH equations is a sensible approach worthy of further research. © 2016 Cambridge University Press.
Los, S.; Hipps, L.; Alfieri, J. G.; Prueger, J. H.; Kustas, W. P.
2017-12-01
Agriculture in semi-arid regions is globally facing increasing stress on water resources. Hence, knowledge of water used in irrigated crops is essential for water resource management. However, quantifying spatial and temporal distribution of evapotranspiration (ET) has proven difficult because of the inherent complexities involved. Understanding of the complex biophysical relationships that govern ET is incomplete, particularly for heterogeneous vegetation. The USDA-ARS is developing a remotely-sensed ET modeling system that utilizes a two-source energy balance (TSEB) model capable of simulating turbulent water and energy exchange from measurements of radiometric land surface temperature. The modeling system has been tested over a number of vegetated surfaces and is currently being validated for vineyard sites in the Central Valley of California through the Grape Remote sensing Atmospheric Profiling & Evapotranspiration eXperiment (GRAPEX). The highly variable, elevated canopy structure and semi-arid climatic conditions of these sites give the opportunity to gain knowledge of both turbulent exchange processes and the TSEB model's ability to simulate turbulent fluxes for heterogeneous vegetation. Analyzed are fast-response (20 Hz) 3-D velocity, temperature, and humidity measurements gathered over 4 years at two vineyard sites. These data were collected at a height of 5 m, within the surface layer but above the canopy, and at 1.5 m, below the canopy top. Power spectra and cross-spectra are used to study behavior of turbulent water vapor exchanges and coupling between the canopy layer and surface layer under various atmospheric conditions. Frequent light winds and unstable daytime conditions, combined with the complicated canopy structure, often induce intermittent and episodic turbulence transport. This resulted in a modal behavior alternating between periods of more continuous canopy venting and periods where water vapor fluxes are dominated by transient, low
Energy Technology Data Exchange (ETDEWEB)
1982-04-01
The purpose of the study was to determine what energy savings can be achieved by coordinating the resources and requirements of two facilities, the 26th Ward Water Pollution Control Plant (WPCP) and a housing development named Starrett City with its own total energy system. It was determined that three energy exchange options were economically and technically feasible. These include: the transfer of digester gas produced at the 26th Ward to the boilers at the Starrett City's total energy plant (TEP); the transfer of hot water heated at the TEP to the 26th Ward for space and process heating; and the transfer of coal effluent waste water from the 26th Ward to the condenser cooling systems at the TEP. Technical information is presented to support the findings. The report addresses those tasks of the statement of work dedicated to data acquisition, analysis, and energy conservation strategies internal to the Starrett City TEP and the community it supplies as well as to the 26th Ward WPCP. (MCW)
The ground surface energy balance in modelling horizontal ground heat exchangers
Bortoloni, M.; Bottarelli, M.; Su, Y.
2017-01-01
The performance of horizontal ground heat exchangers (HGHEs) is strongly dependent on climatic conditions, due to the low installation depth. In numerical modelling of HGHEs, the estimation of shallow soil temperature distribution is a key issue, therefore the boundary condition (BC) at the ground surface should be assigned carefully. With this in mind, a model of the energy balance at the ground surface (GSEB), based on weather variables, was developed. The model was tested as the 3rd kind BC at ground surface in modelling HGHEs by means of the FEM code Comsol Multiphysics, solving the unsteady heat transfer problem in a 2D domain. The GSEB model was calibrated and validated with the observed soil temperature at different depths. In addition, the effect on numerical solutions of different BCs, when assigned at the ground surface, was analysed. Three different simulations were carried out applying the GSEB model, the equivalent surface heat flux and temperature as boundary conditions of the 1st, 2nd and 3rd kind, respectively. The results of this study indicate that the use of the GSEB model is a preferable approach to the problem and that the use of the equivalent surface temperature can be considered as a reasonable simplification.
Application of the Two-Source Energy Balance (TSEB) Model using land surface temperature (LST) requires aerodynamic resistance parameterizations for the flux exchange above the canopy layer, within the canopy air space and at the soil/substrate surface. There are a number of aerodynamic resistance f...
Thermal Energy Exchange Model and Water Loss of a Barrel Cactus, Ferocactus acanthodes1
Lewis, Donald A.; Nobel, Park S.
1977-01-01
The influences of various diurnal stomatal opening patterns, spines, and ribs on the stem surface temperature and water economy of a CAM succulent, the barrel cactus Ferocactus acanthodes, were examined using an energy budget model. To incorporate energy exchanges by shortwave and longwave irradiation, latent heat, conduction, and convection as well as the heat storage in the massive stem, the plant was subdivided into over 100 internal and external regions in the model. This enabled the average surface temperature to be predicted within 1 C of the measured temperature for both winter and summer days. Reducing the stem water vapor conductance from the values observed in the field to zero caused the average daily stem surface temperature to increase only 0.7 C for a winter day and 0.3 C for a summer day. Thus, latent heat loss does not substantially reduce stem temperature. Although the surface temperatures averaged 18 C warmer for the summer day than for the winter day for a plant 41 cm tall, the temperature dependence of stomatal opening caused the simulated nighttime water loss rates to be about the same for the 2 days. Spines moderated the amplitude of the diurnal temperature changes of the stem surface, since the daily variation was 17 C for the winter day and 25 C for the summer day with spines compared with 23 C and 41 C, respectively, in their simulated absence. Ribs reduced the daytime temperature rise by providing 54% more area for convective heat loss than for a smooth circumscribing surface. In a simulation where both spines and ribs were eliminated, the daytime average surface temperature rose by 5 C. PMID:16660148
Thermal Energy Exchange Model and Water Loss of a Barrel Cactus, Ferocactus acanthodes.
Lewis, D A; Nobel, P S
1977-10-01
The influences of various diurnal stomatal opening patterns, spines, and ribs on the stem surface temperature and water economy of a CAM succulent, the barrel cactus Ferocactus acanthodes, were examined using an energy budget model. To incorporate energy exchanges by shortwave and longwave irradiation, latent heat, conduction, and convection as well as the heat storage in the massive stem, the plant was subdivided into over 100 internal and external regions in the model. This enabled the average surface temperature to be predicted within 1 C of the measured temperature for both winter and summer days.Reducing the stem water vapor conductance from the values observed in the field to zero caused the average daily stem surface temperature to increase only 0.7 C for a winter day and 0.3 C for a summer day. Thus, latent heat loss does not substantially reduce stem temperature. Although the surface temperatures averaged 18 C warmer for the summer day than for the winter day for a plant 41 cm tall, the temperature dependence of stomatal opening caused the simulated nighttime water loss rates to be about the same for the 2 days.Spines moderated the amplitude of the diurnal temperature changes of the stem surface, since the daily variation was 17 C for the winter day and 25 C for the summer day with spines compared with 23 C and 41 C, respectively, in their simulated absence. Ribs reduced the daytime temperature rise by providing 54% more area for convective heat loss than for a smooth circumscribing surface. In a simulation where both spines and ribs were eliminated, the daytime average surface temperature rose by 5 C.
Energy Technology Data Exchange (ETDEWEB)
Bauer, Dan
2011-07-15
The thermal use of the underground for heating and cooling applications can be done with borehole heat exchangers. This work deals with the further development of the modelling of thermal transport processes inside and outside the borehole as well as with the application of the further developed models. The combination of high accuracy and short computation time is achieved by the development of three-dimensional thermal resistance and capacity models for borehole heat exchangers. Short transient transport processes can be calculated by the developed model with a considerable higher dynamic and accuracy than with known models from literature. The model is used to evaluate measurement data of a thermal response test by parameter estimation technique with a transient three-dimensional model for the first time. Clear advantages like shortening of the test duration are shown. The developed borehole heat exchanger model is combined with a three-dimensional description of the underground in the Finite-Element-Program FEFLOW. The influence of moving groundwater on borehole heat exchangers and borehole thermal energy stores is then quantified.
Belkić, Dževad
1999-06-01
Exact comprehensive computations are carried out by means of four leading second-order approximations yielding differential cross sections dQ/ dΩ for the basic charge exchange process H ++H(1s)→H(1s)+H + at intermediate and high energies. The obtained extensive set of results is thoroughly tested against all the existing experimental data with the purpose of critically assessing the validity of the boundary corrected second-Born (CB2), continuum-distorted wave (CDW), impulse approximation (IA) and the reformulated impulse approximation (RIA). The conclusion which emerges from this comparative study clearly indicates that the RIA agrees most favorably with the measurements available over a large energy range 25 keV-5 MeV. Such a finding reaffirms the few-particle quantum scattering theory which imposes several strict conditions on adequate second-order methods. These requirements satisfied by the RIA are: (i) normalisations of all the scattering wave functions, (ii) correct boundary conditions in both entrance and exit channels, (iii) introduction of a mathematically justified two-center continuum state for the sum of an attractive and a repulsive Coulomb potential with the same interaction strength, (iv) inclusion of the multiple scattering effects neglected in the IA, (v) a proper description of the Thomas double scattering in good agreement with the experiments and without any unobserved peak splittings. Nevertheless, the performed comparative analysis of the above four approximations indicates that none of the methods is free from some basic shortcomings. Despite its success, the RIA remains essentially a high-energy model like the other three methods under study. More importantly, their perturbative character leaves virtually no room for further systematic improvements, since the neglected higher-order terms are prohibitively tedious for practical purposes and have never been computed exactly. To bridge this gap, we presently introduce the variational Pad
International Nuclear Information System (INIS)
Belkic, Dzevad
1999-01-01
Exact comprehensive computations are carried out by means of four leading second-order approximations yielding differential cross sections dQ/dΩ for the basic charge exchange process H + +H(1s)→H(1s)+H + at intermediate and high energies. The obtained extensive set of results is thoroughly tested against all the existing experimental data with the purpose of critically assessing the validity of the boundary corrected second-Born (CB2), continuum-distorted wave (CDW), impulse approximation (IA) and the reformulated impulse approximation (RIA). The conclusion which emerges from this comparative study clearly indicates that the RIA agrees most favorably with the measurements available over a large energy range 25 keV-5 MeV. Such a finding reaffirms the few-particle quantum scattering theory which imposes several strict conditions on adequate second-order methods. These requirements satisfied by the RIA are: (i) normalisations of all the scattering wave functions, (ii) correct boundary conditions in both entrance and exit channels, (iii) introduction of a mathematically justified two-center continuum state for the sum of an attractive and a repulsive Coulomb potential with the same interaction strength, (iv) inclusion of the multiple scattering effects neglected in the IA, (v) a proper description of the Thomas double scattering in good agreement with the experiments and without any unobserved peak splittings. Nevertheless, the performed comparative analysis of the above four approximations indicates that none of the methods is free from some basic shortcomings. Despite its success, the RIA remains essentially a high-energy model like the other three methods under study. More importantly, their perturbative character leaves virtually no room for further systematic improvements, since the neglected higher-order terms are prohibitively tedious for practical purposes and have never been computed exactly. To bridge this gap, we presently introduce the variational Pade
Multicomponent ion exchange model
International Nuclear Information System (INIS)
Robinson, S.M.; Arnold, W.D.; Byers, C.H.
1990-01-01
The optimization of ion-exchange column design becomes increasingly important in applications where high efficiency is required to remove trace components in wastewater to very low discharge requirements and for treating hazardous wastewaters where the disposal costs for secondary waste is extremely high. A predictive mathematical model is being developed for improved design of ion-exchange columns for treatment of wastewaters which are contaminated with trace quantities of Sr-90 and Cs-137. Equilibria isotherms and mass transfer mechanisms are being experimentally determined for isothermal multicomponent ion exchange of Ca, Mg, Na, Ca, and Sr with Ionsive IE-95 chabazite zeolite. These equations are being included in a mathematical model to determine the cation breakthrough curves for different column configurations and operating conditions
Guarnieri, Massimo; Alotto, Piergiorgio; Moro, Federico
2015-11-01
Thanks to the independent sizing of power and energy, hydrogen-based energy storage is one of the very few technologies capable of providing long operational times in addition to the other advantages offered by electrochemical energy storage, for example scalability, site versatility, and mobile service. The typical design consists of an electrolyzer in charge mode and a separate fuel cell in discharge mode. Instead, a unitized regenerative fuel cell (URFC) is a single device performing both energy conversions, achieving a higher compactness and power-to-weight ratio. This paper presents a performance model of a URFC based on a proton exchange membrane (PEM) electrolyte and working on hydrogen and oxygen, which can provide high energy and power densities (>0.7 W cm-2). It provides voltage, power, and efficiency at varying load conditions as functions of the controlling physical quantities: temperature, pressure, concentration, and humidification. The model constitutes a tool for designing the interface and control sub-system as well as for exploring optimized cell/stack designs and operational conditions. To date, only a few of such analyses have been carried out and more research is needed in order to explore the true potential of URFCs.
DEFF Research Database (Denmark)
Lunde, Asger; Olesen, Kasper Vinther
measures of volatility. An influential bias in these measures is documented, which motivates the use of a flexible and robust methodology such as the Realized GARCH. Within this framework, forecasting of the full density for long horizons is feasible, which we pursue. We document variability in conditional...... variances over time, which stresses the importance of careful modeling and forecasting of volatility. We show that improved model fit can be obtained in-sample by utilizing high-frequency data compared to standard models that use only daily observations. Additionally, we show that the intraday sampling...... frequency and method have significant implications for model fit in-sample. Finally, we consider an extensive out-of-sample exercise to forecast the conditional return distribution. The out-of-sample results for the Realized GARCH forecasts suggest a limited added value from using “traditional” realized...
Application of the Two-Source Energy Balance (TSEB) Model using land surface temperature (LST) requires aerodynamic resistance parameterizations for the flux exchange above the canopy layer, within the canopy air space and at the soil/substrate surface. There are a number of aerodynamic resistance f...
Offshore Energy Knowledge Exchange Workshop Report
Energy Technology Data Exchange (ETDEWEB)
none,
2012-04-12
A report detailing the presentations and topics discussed at the Offshore Energy Knowledge Exchange Workshop, an event designed to bring together offshore energy industry representatives to share information, best practices, and lessons learned.
Gazijahani, Farhad Samadi; Ravadanegh, Sajad Najafi; Salehi, Javad
2018-02-01
The inherent volatility and unpredictable nature of renewable generations and load demand pose considerable challenges for energy exchange optimization of microgrids (MG). To address these challenges, this paper proposes a new risk-based multi-objective energy exchange optimization for networked MGs from economic and reliability standpoints under load consumption and renewable power generation uncertainties. In so doing, three various risk-based strategies are distinguished by using conditional value at risk (CVaR) approach. The proposed model is specified as a two-distinct objective function. The first function minimizes the operation and maintenance costs, cost of power transaction between upstream network and MGs as well as power loss cost, whereas the second function minimizes the energy not supplied (ENS) value. Furthermore, the stochastic scenario-based approach is incorporated into the approach in order to handle the uncertainty. Also, Kantorovich distance scenario reduction method has been implemented to reduce the computational burden. Finally, non-dominated sorting genetic algorithm (NSGAII) is applied to minimize the objective functions simultaneously and the best solution is extracted by fuzzy satisfying method with respect to risk-based strategies. To indicate the performance of the proposed model, it is performed on the modified IEEE 33-bus distribution system and the obtained results show that the presented approach can be considered as an efficient tool for optimal energy exchange optimization of MGs. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.
Single- and double-charge exchange at low pion energies
International Nuclear Information System (INIS)
Baer, H.W.
1991-01-01
A review is given of pion single- and double-charge exchange reactions at incident energies of 25 to 65 MeV leading to isobaric analog states, and in the case of double-charge exchange leading to the ground state of the residual nucleus. The crucial role of the higher nuclear transparency at low pion energies for the analysis of the data in terms of single and double scattering is demonstrated. The large effects on double-charge exchange produced by the spatial correlations in nuclear wave functions are evident. The data on 1f 7/2 nuclei at 35 MeV are used to establish the general validity of a shell-model-based two-amplitude model for these transitions. Recent measurements of the energy dependence between 25 and 65 MeV of double-charge exchange cross sections at forward angles are presented and discussed. 33 refs., 19 figs
Exchange energy of inhomogenous electron gas near a metal surface
International Nuclear Information System (INIS)
Miglio, L.; Tosi, M.P.; March, N.H.
1980-12-01
Using the first-order density matrix of an infinite-barrier model of a metal surface, the exchange energy density can be evaluated exactly as a function of distance z from the barrier. This result is compared with the local approximation -3/4e 2 (3/π)sup(1/3) rhosup(4/3)(z) where rho is the electron density in the model. The local approximation is demonstrated to be quantitatively accurate at all z. The integrated surface exchange energy is given to within 3% by the local theory. (author)
Energy Technology Data Exchange (ETDEWEB)
Khoa, Dao T.; Thang, Dang Ngoc [VINATOM, Institute for Nuclear Science and Technique, Hanoi (Viet Nam); Loc, Bui Minh [VINATOM, Institute for Nuclear Science and Technique, Hanoi (Viet Nam); University of Pedagogy, Ho Chi Minh City (Viet Nam)
2014-02-15
The Fermi transition (ΔL = ΔS = 0 and ΔT = 1) between the nuclear isobaric analog states (IAS), induced by the charge-exchange (p, n) or ({sup 3}He, t) reaction, can be considered as ''elastic'' scattering of proton or {sup 3}He by the isovector term of the optical potential (OP) that flips the projectile isospin. The accurately measured (p, n) or ({sup 3}He, t) scattering cross section to the IAS can be used, therefore, to probe the isospin dependence of the proton or {sup 3}He optical potential. Within the folding model, the isovector part of the OP is determined exclusively by the neutron-proton difference in the nuclear densities and the isospin dependence of the effective nucleon-nucleon (NN) interaction. Because the isovector coupling explicitly links the isovector part of the proton or {sup 3}He optical potential to the cross section of the charge-exchange (p, n) or ({sup 3}He, t) scattering to the IAS, the isospin dependence of the effective (in-medium) NN interaction can be well tested in the folding model analysis of these charge-exchange reactions. On the other hand, the same isospin- and density-dependent NN interaction can also be used in a Hartree-Fock calculation of asymmetric nuclear matter, to estimate the nuclear matter energy and its asymmetry part (the nuclear symmetry energy). As a result, the fine-tuning of the isospin dependence of the effective NN interaction against the measured (p, n) or ({sup 3}He, t) cross sections should allow us to make some realistic prediction of the nuclear symmetry energy and its density dependence. (orig.)
International Nuclear Information System (INIS)
Khoa, Dao T.; Thang, Dang Ngoc; Loc, Bui Minh
2014-01-01
The Fermi transition (ΔL = ΔS = 0 and ΔT = 1) between the nuclear isobaric analog states (IAS), induced by the charge-exchange (p, n) or ( 3 He, t) reaction, can be considered as ''elastic'' scattering of proton or 3 He by the isovector term of the optical potential (OP) that flips the projectile isospin. The accurately measured (p, n) or ( 3 He, t) scattering cross section to the IAS can be used, therefore, to probe the isospin dependence of the proton or 3 He optical potential. Within the folding model, the isovector part of the OP is determined exclusively by the neutron-proton difference in the nuclear densities and the isospin dependence of the effective nucleon-nucleon (NN) interaction. Because the isovector coupling explicitly links the isovector part of the proton or 3 He optical potential to the cross section of the charge-exchange (p, n) or ( 3 He, t) scattering to the IAS, the isospin dependence of the effective (in-medium) NN interaction can be well tested in the folding model analysis of these charge-exchange reactions. On the other hand, the same isospin- and density-dependent NN interaction can also be used in a Hartree-Fock calculation of asymmetric nuclear matter, to estimate the nuclear matter energy and its asymmetry part (the nuclear symmetry energy). As a result, the fine-tuning of the isospin dependence of the effective NN interaction against the measured (p, n) or ( 3 He, t) cross sections should allow us to make some realistic prediction of the nuclear symmetry energy and its density dependence. (orig.)
Local density approximations for relativistic exchange energies
International Nuclear Information System (INIS)
MacDonald, A.H.
1986-01-01
The use of local density approximations to approximate exchange interactions in relativistic electron systems is reviewed. Particular attention is paid to the physical content of these exchange energies by discussing results for the uniform relativistic electron gas from a new point of view. Work on applying these local density approximations in atoms and solids is reviewed and it is concluded that good accuracy is usually possible provided self-interaction corrections are applied. The local density approximations necessary for spin-polarized relativistic systems are discussed and some new results are presented
Directory of Open Access Journals (Sweden)
Nee Alexander
2016-01-01
Full Text Available Mathematical modeling of conjugate natural convection in a closed rectangular cavity with a radiant energy source in conditions of convective-radiative heat exchange at the external boundary was conducted. The radiant energy distribution was set by the Lambert’s law. Conduction and convection processes analysis showed that the air masses flow pattern is modified slightly over the time. The temperature increases in the gas cavity, despite the heat removal from the one of the external boundary. According to the results of the integral heat transfer analysis were established that the average Nusselt number (Nuav increasing occurs up to τ = 200 (dimensionless time. Further Nuav has changed insignificantly due to the temperature field equalization near the interfaces “gas – wall”.
Houlborg, Rasmus; Anderson, Martha C.; Daughtry, C. S. T.; Kustas, W. P.; Rodell, Matthew
2010-01-01
Chlorophylls absorb photosynthetically active radiation and thus function as vital pigments for photosynthesis, which makes leaf chlorophyll content (C(sub ab) useful for monitoring vegetation productivity and an important indicator of the overall plant physiological condition. This study investigates the utility of integrating remotely sensed estimates of C(sub ab) into a thermal-based Two-Source Energy Balance (TSEB) model that estimates land-surface CO2 and energy fluxes using an analytical, light-use-efficiency (LUE) based model of canopy resistance. The LUE model component computes canopy-scale carbon assimilation and transpiration fluxes and incorporates LUE modifications from a nominal (species-dependent) value (LUE(sub n)) in response to short term variations in environmental conditions, However LUE(sub n) may need adjustment on a daily timescale to accommodate changes in plant phenology, physiological condition and nutrient status. Day to day variations in LUE(sub n) were assessed for a heterogeneous corn crop field in Maryland, U,S.A. through model calibration with eddy covariance CO2 flux tower observations. The optimized daily LUE(sub n) values were then compared to estimates of C(sub ab) integrated from gridded maps of chlorophyll content weighted over the tower flux source area. The time continuous maps of daily C(sub ab) over the study field were generated by focusing in-situ measurements with retrievals generated with an integrated radiative transfer modeling tool (accurate to within +/-10%) using at-sensor radiances in green, red and near-infrared wavelengths acquired with an aircraft imaging system. The resultant daily changes in C(sub ab) within the tower flux source area generally correlated well with corresponding changes in daily calibrated LUE(sub n) derived from the tower flux data, and hourly water, energy and carbon flux estimation accuracies from TSEB were significantly improved when using C(sub ab) for delineating spatio
Veka, Steinar; Lien, Gudbrand; Westgaard, Sjur; Higgs, Helen
2012-01-01
In this paper we investigate the extent to which the price of Nordic electricity derivatives correlates with European Energy Exchange (EEX) and Intercontinental Exchange (ICE) electricity contracts. We also include their price correlation with ICE gas, Brent crude oil, coal and carbon emission contracts. Using multivariate generalized autoregressive conditional heteroskedasticity models, we find significant time-varying relationships between all of the energy commodities included in the analy...
Rethinking exchange market models as optimization algorithms
Luquini, Evandro; Omar, Nizam
2018-02-01
The exchange market model has mainly been used to study the inequality problem. Although the human society inequality problem is very important, the exchange market models dynamics until stationary state and its capability of ranking individuals is interesting in itself. This study considers the hypothesis that the exchange market model could be understood as an optimization procedure. We present herein the implications for algorithmic optimization and also the possibility of a new family of exchange market models
High energy multi-gluon exchange amplitudes
International Nuclear Information System (INIS)
Jaroszewicz, T.
1980-11-01
We examine perturbative high energy n-gluon exchange amplitudes calculated in the Coulomb gauge. If n exceeds the minimum required by the t-channel quantum numbers, such amplitudes are non-leading in lns. We derive a closed system of coupled integral equations for the corresponding two-particle n-gluon vertices, obtained by summing the leading powers of ln(N μ psup(μ)), where psup(μ) is the incident momentum and Nsup(μ) the gauge-defining vector. Our equations are infra-red finite, provided the external particles are colour singlets. (author)
Zeeman, M. J.; Wolz, K.; Adler, B.; Brenner, C.; De Roo, F.; Emeis, S.; Kalthoff, N.; Mauder, M.; Schäfer, K.; Wohlfahrt, G.; Zhao, P.
2016-12-01
We investigated biosphere-atmosphere exchange processes in relation to the atmospheric boundary-layer (ABL) flow in a shallow valley. Land-use heterogeneity and topography can force local atmospheric flow patterns, including local circulations. Such flow patterns can impair current techniques for the quantification and source attribution of surface-exchange fluxes due to flux-divergence, advection and decoupling. Wind field, temperature and humidity structures in the ABL were observed in high resolution with spatially distributed observations in a 1 km3 experimental domain. Remote-sensing observations of wind, temperature and particles in the ABL (Raman-lidar; RASS; ceilometer; microwave radiometer; 3D Doppler-lidar) were combined with a high-resolution network of in-situ observations that included vertical and horizontal profiles of wind, temperature, carbon dioxide, methane and water vapor concentrations. The experiments were co-located with the long-term eddy covariance (EC) observatory Fendt (DE-Fen; ICOS, TERENO) and were part of international cooperative efforts in 2015 and 2016 (the ScaleX campaigns). The gathered experimental data offers a scale-transcending insight in local flow patterns in mountainous terrain and their influence on surface-exchange fluxes of energy and matter as observed by EC and flux-gradient methodology. In addition, the data is used for validation of Large-Eddy Simulations in complex terrain using PALM-LES. Within this modelling framework, virtual measurements are conducted to further assess the importance of three-dimensional advective and horizontal turbulent transport terms.
Mezbahuddin, M.; Grant, R. F.; Hirano, T.
2015-11-01
Soil carbon stocks in tropical peatlands have declined recently from water table depth (WTD) drawdown caused by increased frequency and intensity of climate extremes like El Niño and by artificial drainage. Restoration of these carbon stocks under these climatic and anthropogenic disturbances requires improved predictive capacity for hydrological feedbacks to ecological processes. Process-based modeling of tropical peatland ecohydrology could provide us with such capacity, but such modeling has thus far been limited. We aimed at using basic processes for water and O2 transport and their effects on ecosystem water, carbon, and nitrogen cycling to model seasonal and interannual variations of WTD and surface energy exchange. We tested these processes in a process-based model ecosys in a drained tropical Indonesian peatland from an El Niño year 2002 to a wetter year 2005. WTD was modeled from hydraulically driven water transfers controlled vertically by precipitation versus evapotranspiration (ET) and laterally by discharge versus recharge to or from an external reference WTD. These transfers caused WTD drawdown and soil drying to be modeled during dry seasons, which reduced ET and increased Bowen ratio by lowering stomatal conductance. More pronounced dry seasons in drier years 2002-2004 versus wetter year 2005 caused deeper WTD, more intense peat drying, and greater plant water stress. These modeled trends were well corroborated by site measurements as apparent in regression statistics of modeled versus observed WTD (R2 > 0.8), latent heat (R2 > 0.8), and sensible heat (R2 > 0.7) fluxes. Insights gained from this modeling would aid in predicting the fate of tropical peatlands under future drier climates.
Enabling Detailed Energy Analyses via the Technology Performance Exchange: Preprint
Energy Technology Data Exchange (ETDEWEB)
Studer, D.; Fleming, K.; Lee, E.; Livingood, W.
2014-08-01
One of the key tenets to increasing adoption of energy efficiency solutions in the built environment is improving confidence in energy performance. Current industry practices make extensive use of predictive modeling, often via the use of sophisticated hourly or sub-hourly energy simulation programs, to account for site-specific parameters (e.g., climate zone, hours of operation, and space type) and arrive at a performance estimate. While such methods are highly precise, they invariably provide less than ideal accuracy due to a lack of high-quality, foundational energy performance input data. The Technology Performance Exchange was constructed to allow the transparent sharing of foundational, product-specific energy performance data, and leverages significant, external engineering efforts and a modular architecture to efficiently identify and codify the minimum information necessary to accurately predict product energy performance. This strongly-typed database resource represents a novel solution to a difficult and established problem. One of the most exciting benefits is the way in which the Technology Performance Exchange's application programming interface has been leveraged to integrate contributed foundational data into the Building Component Library. Via a series of scripts, data is automatically translated and parsed into the Building Component Library in a format that is immediately usable to the energy modeling community. This paper (1) presents a high-level overview of the project drivers and the structure of the Technology Performance Exchange; (2) offers a detailed examination of how technologies are incorporated and translated into powerful energy modeling code snippets; and (3) examines several benefits of this robust workflow.
Exchange energy in the local Airy gas approximation
DEFF Research Database (Denmark)
Vitos, Levente; Johansson, B.; Kollár, J.
2000-01-01
The Airy gas model of the edge electron gas is used to construct an exchange-energy functional that is an alternative to those obtained in the local-density and generalized-gradient approximations. Test calculations for rare-gas atoms, molecules, solids, and surfaces show that the Airy gas...... functional performs better than the local-density approximation in all cases and better than the generalized-gradient approximation for solids and surfaces....
Cardioplegia heat exchanger design modelling using computational fluid dynamics.
van Driel, M R
2000-11-01
A new cardioplegia heat exchanger has been developed by Sorin Biomedica. A three-dimensional computer-aided design (CAD) model was optimized using computational fluid dynamics (CFD) modelling. CFD optimization techniques have commonly been applied to velocity flow field analysis, but CFD analysis was also used in this study to predict the heat exchange performance of the design before prototype fabrication. The iterative results of the optimization and the actual heat exchange performance of the final configuration are presented in this paper. Based on the behaviour of this model, both the water and blood fluid flow paths of the heat exchanger were optimized. The simulation predicted superior heat exchange performance using an optimal amount of energy exchange surface area, reducing the total contact surface area, the device priming volume and the material costs. Experimental results confirm the empirical results predicted by the CFD analysis.
Energy exchange between knee and ankle in a transfemoral prosthesis
Koopman, Hubertus F.J.M.; Behrens, Sebastiaan Maria; Hekman, Edsko E.G.; Ünal, Ramazan
2013-01-01
In order to make an energy efficient transfemoral prosthesis, there should be energy exchange between knee and ankle of the prosthesis. A concept containing various spring elements is designed and tested for a single subject. It is shown that the concept of energy exchange can be realized; in this
2012-12-25
divides total solar shortwave into Photosynthetically Available Radiation (PAR; 350-700 nm) and longer (>700 nm) spectral components. The depth...phytoplankton stocks in a coastal embayment may impact thermal energy exchange processes. Monterey Bay simulations parameterizing solar shortwave transparency...suggests that the retention of shortwave solar flux by ocean flora may directly impact even short-term forecasts of coastal meteorological variables
Model Uncertainty and Exchange Rate Forecasting
Kouwenberg, R.; Markiewicz, A.; Verhoeks, R.; Zwinkels, R.C.J.
2017-01-01
Exchange rate models with uncertain and incomplete information predict that investors focus on a small set of fundamentals that changes frequently over time. We design a model selection rule that captures the current set of fundamentals that best predicts the exchange rate. Out-of-sample tests show
Energy and Environment. Electric power stock exchange
International Nuclear Information System (INIS)
Fazioli, R.; Antonioli, B.; Beccarello, M.; Da Rin, B.
2000-01-01
In this paper are reported the structural characteristics of electric power stock exchange in the processes liberalization of european electric markets. International experience are also considered [it
Modelling and simulation of a heat exchanger
Xia, Lei; Deabreu-Garcia, J. Alex; Hartley, Tom T.
1991-01-01
Two models for two different control systems are developed for a parallel heat exchanger. First by spatially lumping a heat exchanger model, a good approximate model which has a high system order is produced. Model reduction techniques are applied to these to obtain low order models that are suitable for dynamic analysis and control design. The simulation method is discussed to ensure a valid simulation result.
Chebbi, Wafa; Le Dantec, Valérie; Boulet, Gilles; Lili Chabaane, Zohra; Fanise, Pascal; Mougenot, Bernard; Ayari, Hassan; Cheheb, Hechmi; Rivalland, Vincent; Zribi, Mehrez
2016-04-01
Evapotranspiration is one of the most important fluxes of the water balance in semi-arid areas. The components of evapotranspiration are soil evaporation (E) and transpiration (T) through the stomata of the plants. The estimation of crop actual transpiration is a major issue in central and south Tunisia because it affects irrigation scheduling, crop growth and yield. Olive is well adapted to the soil and climate conditions of Tunisia and covers an entire agricultural land of 1.7 million hectares representing nearly 79% of the total tree area. The southern part of the Mediterranean basin faces climate change and could affect olive tree production in rainfed conditions. The hydrological functioning of sparse olive trees is difficult to characterize because of its low LAI. For a good comprehension of the functionning of the water and energy transfers throuigh the Soil-Plant-Atmosphere continuum, we combine the eddy covariance method, soil water content measurements and sap flow method. The main objectives of this study are 1) to characterize the eco-hydrological processes of sparse olive trees from a dedicated experimental protocol and a SVAT model adapted to the sparse characteristic of such crop 2) to analyze the vulnerability of the system to climate change. First, we identify the factors of changes of transpiration at different time steps and characterized the different water stress levels by the combined use of different types of ecophysiological (sap flow) and spectral (photochemical reflectance index) measurements. Then, we estimate the percentage of evaporation, transpiration and the total evapotranspiration (ET). We compared scaled evapotranspiration values (the fraction of cover fraction contributing to the footprint of total ET fluxes) with scaled sap flow values. The sum of soil evaporation and transpiration matches well the total ET. A SVAT model is currently be applied and expanded to represent the impact of canopy structure on radiative and turbulent
Heat exchangers: an energy viewpoint approach
International Nuclear Information System (INIS)
Buchet, E.
1981-01-01
This paper, at first, presents a brief discussion of the concept of exergy. The second part studies the exchange of heat by conduction, convection and radiation as well as the irreversibilities due to the required temperature gradient. It shows the importance of the temperature level on the heat flux and the exergy lost. This analysis results also in conclusions on the fins and the thermal insulation. The third part studies the heat exchangers, in general. The loss of exergy due to the thermal exchange permits a comparison of the thermal value of these apparatus and, as well, shows the influence of the isothermal change of state of a fluid, i.e. in vaporization. Finally, based on the conclusions reached above, different types of heat exchangers used in industrial applications are analysed [fr
Magnon energies and exchange interactions in terbium
DEFF Research Database (Denmark)
Houmann, Jens Christian Gylden
1968-01-01
The magnon density of states, and hence the magnetic contribution to the specific heat, and also the exchange interaction between ions in the same sublattice have been calculated for Tb at 90°K, using experimental results obtained by inelastic neutron scattering.......The magnon density of states, and hence the magnetic contribution to the specific heat, and also the exchange interaction between ions in the same sublattice have been calculated for Tb at 90°K, using experimental results obtained by inelastic neutron scattering....
Modelling of isotope exchange experiments in JET
International Nuclear Information System (INIS)
Ehrenberg, J.
1987-01-01
Isotope exchange experiments from hydrogen to deuterium in JET are theoretically described by employing a simple global isotope exchange model. Experimental results for discharges with limiter temperature around 250 0 C can be approximated by this model if an additional slow diffusion process of hydrogen in the limiter bulk is assumed. In discharges where thermal desorption occurs due to higher limiter temperatures (> or approx. 1000 0 C) (post carbonisation discharges) the change over process seems to be predominantly governed by thermal processes. (orig.)
CSIR Research Space (South Africa)
Osburn, L
2010-01-01
Full Text Available The construction industry has turned to energy modelling in order to assist them in reducing the amount of energy consumed by buildings. However, while the energy loads of buildings can be accurately modelled, energy models often under...
The dielectric environment dependent exchange self-energy of the energy structure in graphene
International Nuclear Information System (INIS)
Yang, C.H.; Xu, W.
2010-01-01
We theoretically calculate the energy dispersion in the presence of the screened exchange self-energy in extrinsic monolayer graphene. It is found that the exchange self-energy enhances the renormalized Fermi velocity. With decreasing the dielectric constant, the screening effect and the electron correlation effect increase which induces the Fermi velocity increasing. The screened exchange energy has an energy shift at the Dirac points. The self-energy from the valance band carriers gives the main contribution to the effective energy. We also discuss the electron density dependence of the self-energy.
The dielectric environment dependent exchange self-energy of the energy structure in graphene
Energy Technology Data Exchange (ETDEWEB)
Yang, C.H., E-mail: chyang@nuist.edu.c [Faculty of Maths and Physics, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Xu, W. [Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)
2010-10-01
We theoretically calculate the energy dispersion in the presence of the screened exchange self-energy in extrinsic monolayer graphene. It is found that the exchange self-energy enhances the renormalized Fermi velocity. With decreasing the dielectric constant, the screening effect and the electron correlation effect increase which induces the Fermi velocity increasing. The screened exchange energy has an energy shift at the Dirac points. The self-energy from the valance band carriers gives the main contribution to the effective energy. We also discuss the electron density dependence of the self-energy.
Model Information Exchange System (MIXS).
2013-08-01
Many travel demand forecast models operate at state, regional, and local levels. While they share the same physical network in overlapping geographic areas, they use different and uncoordinated modeling networks. This creates difficulties for models ...
Energy Technology Data Exchange (ETDEWEB)
Wharton, Sonia [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Simpson, Matthew [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Osuna, Jessica [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Newman, Jennifer [National Renewable Energy Lab. (NREL), Golden, CO (United States); Biraud, Sebastien [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2016-05-01
The Weather Research and Forecasting (WRF) model is used to investigate choice of land surface model (LSM) on the near-surface wind profile, including heights reached by multi-megawatt wind turbines. Simulations of wind profiles and surface energy fluxes were made using five LSMs of varying degrees of sophistication in dealing with soil-plant-atmosphere feedbacks for the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility’s Southern Great Plains (SGP) Central Facility in Oklahoma. Surface-flux and wind-profile measurements were available for validation. The WRF model was run for three two-week periods during which varying canopy and meteorological conditions existed. The LSMs predicted a wide range of energy-flux and wind-shear magnitudes even during the cool autumn period when we expected less variability. Simulations of energy fluxes varied in accuracy by model sophistication, whereby LSMs with very simple or no soil-plant-atmosphere feedbacks were the least accurate; however, the most complex models did not consistently produce more accurate results. Errors in wind shear also were sensitive to LSM choice and were partially related to the accuracy of energy flux data. The variability of LSM performance was relatively high, suggesting that LSM representation of energy fluxes in the WRF model remains a significant source of uncertainty for simulating wind turbine inflow conditions.
The empirical relationship between energy futures prices and exchange rates
International Nuclear Information System (INIS)
Sadorsky, P.
2000-01-01
This paper investigates the interaction between energy futures prices and exchange rates. Results are presented to show that futures prices for crude oil, heating oil and unleaded gasoline are co-integrated with a trade-weighted index of exchange rates. This is important because it means that there exists a long-run equilibrium relationship between these four variables. Granger causality results for both the long- and short-run are presented. Evidence is also presented that suggests exchange rates transmit exogenous shocks to energy futures prices. 22 refs
Proton exchange membrane fuel cells modeling
Gao, Fengge; Miraoui, Abdellatif
2013-01-01
The fuel cell is a potential candidate for energy storage and conversion in our future energy mix. It is able to directly convert the chemical energy stored in fuel (e.g. hydrogen) into electricity, without undergoing different intermediary conversion steps. In the field of mobile and stationary applications, it is considered to be one of the future energy solutions.Among the different fuel cell types, the proton exchange membrane (PEM) fuel cell has shown great potential in mobile applications, due to its low operating temperature, solid-state electrolyte and compactness.This book pre
Air to air fixed plate enthalpy heat exchanger, performance variation and energy analysis
Energy Technology Data Exchange (ETDEWEB)
Nasif, Mohammad Shakir [Universiti Teknologi Petronas, Bandar Seri Iskandar (Malaysia); Alwaked, Rafat [Prince Mohammad Bin Fahd University, Al Khobar (Saudi Arabia); Behnia, Masud [University of Sydney, Sydney (Australia); Morrison, Graham [The University of New South Wales, Sydney (Australia)
2013-11-15
The thermal performance of a Z shape enthalpy heat exchanger utilising 70 gsm Kraft paper as the heat and moisture transfer surface has been investigated. Effects of different inlet air humidity ratio conditions on the heat exchanger effectiveness and on the energy recovered by the heat exchanger have been the main focus of this investigation. A typical air conditioning cooling coil which incorporates an enthalpy heat exchanger has been modelled for tropical climate. Under test conditions, results have shown that latent effectiveness and the moisture resistance coefficient have strong dependency on the inlet air humidity ratio. Moreover, the latent effectiveness has been found to be strongly dependent on the moisture resistance coefficient rather than the convective mass transfer coefficient. Finally, annual energy analysis for Singapore weather conditions have also shown that energy recovered under variable inlet air conditions is 15% less than that recovered under constant inlet air conditions for the same heat exchanger.
SPEEDUP{trademark} ion exchange column model
Energy Technology Data Exchange (ETDEWEB)
Hang, T.
2000-03-06
A transient model to describe the process of loading a solute onto the granular fixed bed in an ion exchange (IX) column has been developed using the SpeedUp{trademark} software package. SpeedUp offers the advantage of smooth integration into other existing SpeedUp flowsheet models. The mathematical algorithm of a porous particle diffusion model was adopted to account for convection, axial dispersion, film mass transfer, and pore diffusion. The method of orthogonal collocation on finite elements was employed to solve the governing transport equations. The model allows the use of a non-linear Langmuir isotherm based on an effective binary ionic exchange process. The SpeedUp column model was tested by comparing to the analytical solutions of three transport problems from the ion exchange literature. In addition, a sample calculation of a train of three crystalline silicotitanate (CST) IX columns in series was made using both the SpeedUp model and Purdue University's VERSE-LC code. All test cases showed excellent agreement between the SpeedUp model results and the test data. The model can be readily used for SuperLig{trademark} ion exchange resins, once the experimental data are complete.
Advanced proton-exchange materials for energy efficient fuel cells.
Energy Technology Data Exchange (ETDEWEB)
Fujimoto, Cy H.; Grest, Gary Stephen; Hickner, Michael A.; Cornelius, Christopher James; Staiger, Chad Lynn; Hibbs, Michael R.
2005-12-01
The ''Advanced Proton-Exchange Materials for Energy Efficient Fuel Cells'' Laboratory Directed Research and Development (LDRD) project began in October 2002 and ended in September 2005. This LDRD was funded by the Energy Efficiency and Renewable Energy strategic business unit. The purpose of this LDRD was to initiate the fundamental research necessary for the development of a novel proton-exchange membranes (PEM) to overcome the material and performance limitations of the ''state of the art'' Nafion that is used in both hydrogen and methanol fuel cells. An atomistic modeling effort was added to this LDRD in order to establish a frame work between predicted morphology and observed PEM morphology in order to relate it to fuel cell performance. Significant progress was made in the area of PEM material design, development, and demonstration during this LDRD. A fundamental understanding involving the role of the structure of the PEM material as a function of sulfonic acid content, polymer topology, chemical composition, molecular weight, and electrode electrolyte ink development was demonstrated during this LDRD. PEM materials based upon random and block polyimides, polybenzimidazoles, and polyphenylenes were created and evaluated for improvements in proton conductivity, reduced swelling, reduced O{sub 2} and H{sub 2} permeability, and increased thermal stability. Results from this work reveal that the family of polyphenylenes potentially solves several technical challenges associated with obtaining a high temperature PEM membrane. Fuel cell relevant properties such as high proton conductivity (>120 mS/cm), good thermal stability, and mechanical robustness were demonstrated during this LDRD. This report summarizes the technical accomplishments and results of this LDRD.
Energy Exchange between Weakly Ionized Gas and a Metal Surface
Polikarpov, A. Ph.; Polikarpov, Ph. J.; Borisov, S. F.
2008-12-01
An attempt to describe heat exchange of low ionized gas with a metal surface has been made with the use of DSMC approach and kinetic Monte-Carlo method. Modeling is adhered to concrete experimental conditions at which thin tungsten wire is placed in plasma and dependence of a heat flow on wire surface temperature, gas pressure, gas nature and a degree of ionization is investigated. As a result of simulation temperature profiles near the wire surface for nitrogen and argon as well as dependence of relative heat flow in a gas/surface system on temperature and degree of ionization with consideration of energy accommodation have been obtained. In the case of nitrogen the chemical charge-transfer reaction is taken into account.
Two-Way communication with energy exchange
DEFF Research Database (Denmark)
Popovski, Petar; Simeone, Osvaldo
2012-01-01
The conventional assumption made in the design of communication systems is that the energy used to transfer information between a sender and a recipient cannot be reused for future communication tasks. A notable exception to this norm is given by passive RFID systems, in which a reader can transfer...
Directory of Open Access Journals (Sweden)
Meelis Mölder
2012-10-01
Full Text Available Simulation of atmospheric and surface processes with an atmospheric model (RAMS during a period of ten days in August 2001 over a boreal area in Sweden were compared to tower measurements and aircraft measurements of vertical profiles as well as surface fluxes from low altitude flights. The shape of the vertical profiles was simulated reasonably well by the model although there were significant biases in absolute values. Surface fluxes were less well simulated and the model showed considerable sensitivity to initial soil moisture conditions. The simulations were performed using two different land cover databases, the original one supplied with the RAMS model and the more detailed CORINE database. The two different land cover data bases resulted in relatively large fine scale differences in the simulated values. The conclusion of this study is that RAMS has the potential to be used as a tool to estimate boundary layer conditions and surface fluxes and meteorology over a boreal area but also that further improvement is needed.
Thermal energy storage systems using fluidized bed heat exchangers
Weast, T.; Shannon, L.
1980-06-01
A rotary cement kiln and an electric arc furnace were chosen for evaluation to determine the applicability of a fluid bed heat exchanger (FBHX) for thermal energy storage (TES). Multistage shallow bed FBHX's operating with high temperature differences were identified as the most suitable for TES applications. Analysis of the two selected conceptual systems included establishing a plant process flow configuration, an operational scenario, a preliminary FBHX/TES design, and parametric analysis. A computer model was developed to determine the effects of the number of stages, gas temperatures, gas flows, bed materials, charge and discharge time, and parasitic power required for operation. The maximum national energy conservation potential of the cement plant application with TES is 15.4 million barrels of oil or 3.9 million tons of coal per year. For the electric arc furnance application the maximum national conservation potential with TES is 4.5 million barrels of oil or 1.1 million tons of coal per year. Present time of day utility rates are near the breakeven point required for the TES system. Escalation of on-peak energy due to critical fuel shortages could make the FBHX/TES applications economically attractive in the future.
Thermal energy storage systems using fluidized bed heat exchangers
Weast, T.; Shannon, L.
1980-01-01
A rotary cement kiln and an electric arc furnace were chosen for evaluation to determine the applicability of a fluid bed heat exchanger (FBHX) for thermal energy storage (TES). Multistage shallow bed FBHX's operating with high temperature differences were identified as the most suitable for TES applications. Analysis of the two selected conceptual systems included establishing a plant process flow configuration, an operational scenario, a preliminary FBHX/TES design, and parametric analysis. A computer model was developed to determine the effects of the number of stages, gas temperatures, gas flows, bed materials, charge and discharge time, and parasitic power required for operation. The maximum national energy conservation potential of the cement plant application with TES is 15.4 million barrels of oil or 3.9 million tons of coal per year. For the electric arc furnance application the maximum national conservation potential with TES is 4.5 million barrels of oil or 1.1 million tons of coal per year. Present time of day utility rates are near the breakeven point required for the TES system. Escalation of on-peak energy due to critical fuel shortages could make the FBHX/TES applications economically attractive in the future.
Modeling foreign exchange risk premium in Armenia
Czech Academy of Sciences Publication Activity Database
Poghosyan, Tigran; Kočenda, Evžen; Zemčík, P.
2008-01-01
Roč. 44, č. 1 (2008), s. 41-61 ISSN 1540-496X R&D Projects: GA MŠk LC542 Institutional research plan: CEZ:MSM0021620846 Keywords : foreign exchange risk premium * Armenia * affine term structure models Subject RIV: AH - Economics Impact factor: 0.611, year: 2008
Modeling foreign exchange risk premium in Armenia
Czech Academy of Sciences Publication Activity Database
Poghosyan, T.; Kočenda, E.; Zemčík, Petr
2008-01-01
Roč. 44, č. 1 (2008), s. 41-61 ISSN 1540-496X R&D Projects: GA MŠk LC542 Institutional research plan: CEZ:AV0Z70850503 Keywords : foreign exchange risk premium * Armenia * affine term structure models Subject RIV: AH - Economics Impact factor: 0.611, year: 2008
Energy absorber for sodium-heated heat exchanger
Essebaggers, J.
1975-12-01
A heat exchanger is described in which water-carrying tubes are heated by liquid sodium and in which the results of accidental contact between the water and the sodium caused by failure of one or more of the water tubes is minimized. An energy absorbing chamber contains a compressible gas and is connected to the body of flowing sodium by a channel so that, in the event of a sodium-water reaction, products of the reaction will partially fill the energy absorbing chamber to attenuate the rise in pressure within the heat exchanger.
Bag-model quantum chromodynamics for hyperons at low energy
International Nuclear Information System (INIS)
Weber, H.J.; Maslow, J.N.
1980-01-01
In a non-perturbative bag model framework, gluon exchange which mediates quark exchange scattering in conjunction with quark interchange is shown to be the basis of the OBE interactions of hyperons at low energy. (orig.)
Metropolis Evaluation of the Hartree-Fock Exchange Energy.
Cytter, Yael; Neuhauser, Daniel; Baer, Roi
2014-10-14
We examine the possibility of using a Metropolis algorithm for computing the exchange energy in a large molecular system. Following ideas set forth in a recent publication (Baer, Neuhauser, and Rabani, Phys. Rev. Lett. 111, 106402 (2013)) we focus on obtaining the exchange energy per particle (ExPE, as opposed to the total exchange energy) to a predefined statistical error and on determining the numerical scaling of the calculation achieving this. For this we assume that the occupied molecular orbitals (MOs) are known and given in terms of a standard Gaussian atomic basis set. The Metropolis random walk produces a sequence of pairs of three-dimensional points (x,x'), which are distributed in proportion to ρ(x,x')(2), where ρ(x,x') is the density matrix. The exchange energy per particle is then simply the average of the Coulomb repulsion energy υC(|x-x'|) over these pairs. To reduce the statistical error we separate the exchange energy into a short-range term that can be calculated deterministically in a linear scaling fashion and a long-range term that is treated by the Metropolis method. We demonstrate the method on water clusters and silicon nanocrystals showing the magnitude of the ExPE standard deviation is independent of system size. In the water clusters a longer random walk was necessary to obtain full ergodicity as Metropolis walkers tended to get stuck for a while in localized regions. We developed a diagnostic tool that can alert a user when such a situation occurs. The calculation effort scales linearly with system size if one uses an atom screening procedure that can be made numerically exact. In systems where the MOs can be localized efficiently the ExPE can even be computed with "sublinear scaling" as the MOs themselves can be screened.
Huang, Yu-Ming M; McCammon, J Andrew; Miao, Yinglong
2018-04-10
Through adding a harmonic boost potential to smooth the system potential energy surface, Gaussian accelerated molecular dynamics (GaMD) provides enhanced sampling and free energy calculation of biomolecules without the need of predefined reaction coordinates. This work continues to improve the acceleration power and energy reweighting of the GaMD by combining the GaMD with replica exchange algorithms. Two versions of replica exchange GaMD (rex-GaMD) are presented: force constant rex-GaMD and threshold energy rex-GaMD. During simulations of force constant rex-GaMD, the boost potential can be exchanged between replicas of different harmonic force constants with fixed threshold energy. However, the algorithm of threshold energy rex-GaMD tends to switch the threshold energy between lower and upper bounds for generating different levels of boost potential. Testing simulations on three model systems, including the alanine dipeptide, chignolin, and HIV protease, demonstrate that through continuous exchanges of the boost potential, the rex-GaMD simulations not only enhance the conformational transitions of the systems but also narrow down the distribution width of the applied boost potential for accurate energetic reweighting to recover biomolecular free energy profiles.
Study of thermal energy storage using fluidized bed heat exchangers
Weast, T. E.; Shannon, L. J.; Ananth, K. P.
1980-01-01
The technical and economic feasibility of fluid bed heat exchangers (FBHX) for thermal energy storage (TES) in waste heat recovery applications is assessed by analysis of two selected conceptual systems, the rotary cement kiln and the electric arc furnace. It is shown that the inclusion of TES in the energy recovery system requires that the difference in off-peak and on-peak energy rates be large enough so that the value of the recovered energy exceeds the value of the stored energy by a wide enough margin to offset parasitic power and thermal losses. Escalation of on-peak energy rates due to fuel shortages could make the FBHX/TES applications economically attractive in the future.
Resonance charge exchange mechanism at high and moderate energies
International Nuclear Information System (INIS)
Bogdanov, A.V.; Gevorkyan, A.S.
1984-01-01
Charge exchange mechanisms at high and medium energies are investigated, ta king the resonance charge exchange of a proton by an hydrogen atom as an example . It is established that there are two classical charge exchange mechanisms rel ated to direct proton knockout from the bound state and one quantum-mechanical mechanism corresponding to the electron tunnelling from one bound state to anoth er. The classical cross-section diverges for two of these mechanisms, and the quasiclassical scattering amplitude must be calculated on the base of a complex classical trajectory. Physical grounds for the choice of such trajectories are discussed and calculations of the Van Vleck determinant for these mechanisms a re presented. Contributions from different mechanisms to the total charge excha nge cross-section are analyzed. A comparison with experimental data and results of other authors is made
A dynamic model for helium core heat exchangers
International Nuclear Information System (INIS)
Schiesser, W.E.; Shih, H.J.; Hartozog, D.G.; Herron, D.M.; Nahmias, D.; Stuber, W.G.; Hindmarsh, A.C.
1990-04-01
To meet the helium (He) requirements of the superconducting supercollider (SSC), the cryogenic plants must be able to respond to time-varying loads. Thus the design and simulation of the cryogenic plants requires dynamic models of their principal components, and in particular, the core heat exchangers. In this paper, we detail the derivation and computer implementation of a model for core heat exchangers consisting of three partial differential equations (PDES) for each fluid stream (the continuity, energy and momentum balances for the He), and one PDE for each parting sheet (the energy balance for the parting sheet metal); the PDEs have time and axial position along the exchanger as independent variables. The computer code can accommodate any number of fluid streams and parting sheets in an adiabatic group. Features of the code include: rigorous or approximate thermodynamic properties for He, upwind and downwind approximation of the PDE spatial derivatives, and sparse matrix time integration. The outputs from the code include the time-dependent axial profiles of the fluid He mass flux, density, pressure, temperature, internal energy and enthalpy. The code is written in transportable Fortran 77, and can therefore be executed on essentially any computer
Spin-density functional for exchange anisotropic Heisenberg model
International Nuclear Information System (INIS)
Prata, G.N.; Penteado, P.H.; Souza, F.C.; Libero, Valter L.
2009-01-01
Ground-state energies for antiferromagnetic Heisenberg models with exchange anisotropy are estimated by means of a local-spin approximation made in the context of the density functional theory. Correlation energy is obtained using the non-linear spin-wave theory for homogeneous systems from which the spin functional is built. Although applicable to chains of any size, the results are shown for small number of sites, to exhibit finite-size effects and allow comparison with exact-numerical data from direct diagonalization of small chains.
Loyselle, Patricia; Prokopius, Kevin
2011-01-01
Proton Exchange Membrane (PEM) fuel cell technology is the leading candidate to replace the alkaline fuel cell technology, currently used on the Shuttle, for future space missions. During a 5-yr development program, a PEM fuel cell powerplant was developed. This report details the initial performance evaluation test results of the powerplant.
European energy exchanges: Too many casino's and too little time
International Nuclear Information System (INIS)
Zewald, H.
2001-01-01
The European energy market has the potential of developing into a booming business, and not just for Europeans. Now that liberalization is seriously taking shape and internet trade has overcome its teething troubles, the Europeans are setting up one exchange after another and the Americans are crossing the Atlantic with a lot of dollar signs in front of their eyes to play poker or roulette. 1 ref
Cosmological evolution with brane-bulk energy exchange
Kiritsis, Elias B; Tetradis, N; Tomaras, T N; Zarikas, V
2003-01-01
The consequences for the brane cosmological evolution of energy exchange between the brane and the bulk are analysed in detail, in the context of a non-factorizable background geometry with vanishing effective cosmological constant on the brane. A rich variety of brane cosmologies is obtained, depending on the precise mechanism of energy transfer, the equation of state of brane-matter and the spatial topology. An accelerating era is generically a feature of our solutions. In the case of low-density flat universe more dark matter than in the conventional FRW picture is predicted. Spatially compact solutions are found to delay their recollapse.
Gas exchange and energy expenditure in chicken embryos
DEFF Research Database (Denmark)
Chwalibog, André; Tauson, Anne-Helene; Ali, Abdalla
to evaluate amount of oxidized fat during embryonic development and to compare daily fat oxidation with changes in the fat content of eggs. The experiment comprised 48 embryos from a modern, fast growing line, Ross 308 (RO) and 48 from a slow growing line, Labresse (LA) of White Plymouth Rock. The O2...... fat contributing with nearly 100 % to the total EE. Since oxidised fat was the main energy fuel the content of fat in eggs decreased with 2.0 (RO) and 1.6 g (LA) during the incubation period. It can be concluded that the pattern of gas exchange and thereby the pattern of energy expenditure...
A Range-Based Multivariate Model for Exchange Rate Volatility
B. Tims (Ben); R.J. Mahieu (Ronald)
2003-01-01
textabstractIn this paper we present a parsimonious multivariate model for exchange rate volatilities based on logarithmic high-low ranges of daily exchange rates. The multivariate stochastic volatility model divides the log range of each exchange rate into two independent latent factors, which are
1981-05-01
A summary of the energy situation in Brazil is presented. Energy consumption rates, reserves of primary energy, and the basic needs and strategies for meeting energy self sufficiency are discussed. Conserving energy, increasing petroleum production, and utilizing other domestic energy products and petroleum by-products are discussed. Specific programs are described for the development and use of alcohol fuels, wood and charcoal, coal, schist, solar and geothermal energy, power from the sea, fresh biomass, special batteries, hydrogen, vegetable oil, and electric energy from water power, nuclear, and coal. Details of the energy model for 1985 are given. Attention is also given to the energy demands and the structure of global energy from 1975 to 1985.
Hydrogen-deuterium exchange study of an allosteric energy cycle.
Beckett, Dorothy
2012-01-01
Elucidation of mechanisms of energy transduction through macromolecules in allosteric systems requires application of a broad range of techniques and approaches. High-resolution structures of the end states in an allosteric system provide invaluable clues about allosteric mechanism. Thermodynamic and kinetic studies reveal the rules that govern the transitions between states in the system. Acquisition of detailed molecular level information about allosteric mechanism requires interrogation of the structural and dynamic properties of both intermediates and end states in the allosteric cycle. Many experimental and computational tools have been developed to probe allostery. Among these are hydrogen-deuterium exchange detected by either NMR spectroscopy or mass spectrometry. This article provides a detailed description of application of hydrogen exchange detected by mass spectrometry (HDX-MS) to investigate an allosteric system.
Sensitivity of molecular vibrational dynamics to energy exchange rate constants
International Nuclear Information System (INIS)
Billing, G D; Coletti, C; Kurnosov, A K; Napartovich, A P
2003-01-01
The sensitivity of molecular vibrational population dynamics, governing the CO laser operated in fundamental and overtone transitions, to vibration-to-vibration rate constants is investigated. With this aim, three rate constant sets have been used, differing in their completeness (i.e. accounting for single-quantum exchange only, or for multi-quantum exchange with a limited number of rate constants obtained by semiclassical calculations, and, finally, with an exhaustive set of rate constants including asymmetric exchange processes, as well) and in the employed interaction potential. The most complete set among these three is introduced in this paper. An existing earlier kinetic model was updated to include the latter new data. Comparison of data produced by kinetic modelling with the above mentioned sets of rate constants shows that the vibrational distribution function, and, in particular, the CO overtone laser characteristics, are very sensitive to the choice of the model. The most complete model predicts slower evolution of the vibrational distribution, in qualitative agreement with experiments
Patra, Abhilash; Jana, Subrata; Samal, Prasanjit
2018-04-01
The construction of meta generalized gradient approximations based on the density matrix expansion (DME) is considered as one of the most accurate techniques to design semilocal exchange energy functionals in two-dimensional density functional formalism. The exchange holes modeled using DME possess unique features that make it a superior entity. Parameterized semilocal exchange energy functionals based on the DME are proposed. The use of different forms of the momentum and flexible parameters is to subsume the non-uniform effects of the density in the newly constructed semilocal functionals. In addition to the exchange functionals, a suitable correlation functional is also constructed by working upon the local correlation functional developed for 2D homogeneous electron gas. The non-local effects are induced into the correlation functional by a parametric form of one of the newly constructed exchange energy functionals. The proposed functionals are applied to the parabolic quantum dots with a varying number of confined electrons and the confinement strength. The results obtained with the aforementioned functionals are quite satisfactory, which indicates why these are suitable for two-dimensional quantum systems.
Ontological modeling of electronic health information exchange.
McMurray, J; Zhu, L; McKillop, I; Chen, H
2015-08-01
Investments of resources to purposively improve the movement of information between health system providers are currently made with imperfect information. No inventories of system-level electronic health information flows currently exist, nor do measures of inter-organizational electronic information exchange. Using Protégé 4, an open-source OWL Web ontology language editor and knowledge-based framework, we formalized a model that decomposes inter-organizational electronic health information flow into derivative concepts such as diversity, breadth, volume, structure, standardization and connectivity. The ontology was populated with data from a regional health system and the flows were measured. Individual instance's properties were inferred from their class associations as determined by their data and object property rules. It was also possible to visualize interoperability activity for regional analysis and planning purposes. A property called Impact was created from the total number of patients or clients that a health entity in the region served in a year, and the total number of health service providers or organizations with whom it exchanged information in support of clinical decision-making, diagnosis or treatment. Identifying providers with a high Impact but low Interoperability score could assist planners and policy-makers to optimize technology investments intended to electronically share patient information across the continuum of care. Finally, we demonstrated how linked ontologies were used to identify logical inconsistencies in self-reported data for the study. Copyright © 2015 Elsevier Inc. All rights reserved.
Characterization of energy exchange parameters in the Himalayan foothills Pakistan
Khalid, Bushra; Kumar, Mukul; Cholaw, Bueh; Aziz Khan, Junaid; Hayat Khan, Azmat
2017-04-01
The characterization of energy exchange parameters for spring season (April-May) has been done for Margalla hills national park (MHNP) Islamabad, Pakistan. It is important because Islamabad city lies in the foothills of Himalayas and micro meteorological activity makes the climate of surrounding areas. The activity on Himalaya's foothills (i.e., Margalla hills) regulate weather and also provide fresh water to the lakes and ponds by late afternoon thunder showers. This research is also important from the perspective of rain water harvesting in Islamabad, Pakistan. The objective of this study is to characterize the energy exchange parameters in the foothills of great Himalayas particularly on MHNP. Landsat ETM+ imageries have been used for calculating the land surface temperature (LST), normalized difference vegetation index (NDVI), and normalized difference moisture index (NDMI). SPOT 5 image has been used for land use/land cover classification over MHNP. The turbulent fluxes have been calculated by computing the values acquired from the processing of satellite imageries and real time observation data sets. The comparisons have been made between the land and atmospheric temperature and moisture to see the difference and its impacts on weather of twin cities i.e., Islamabad and Rawalpindi. The energy exchange parameters have been characterized by analyzing the impacts of weather parameters and turbulent fluxes on MHNP and surrounding cities. The potential rain water harvesting sites have been marked in the foothills. Weather and surface conditions become more favorable for the growth of vegetation by the end of April as the spring season reaches at its peak. There is the start of growing season in the month of April whereas the vegetation becomes thick over time during the month of May over Margalla hills however, the energy exchange parameters follow the same pattern in May as in April. The relative humidity remains between 18 - 55 % and the atmospheric temperature
Integrated O&M for energy generation and exchange facilities
International Nuclear Information System (INIS)
2016-01-01
Ingeteam Service, part of the Ingeteam Group, is a leading company in the provision of integrated O&M services at energy generation and exchange facilities worldwide. From its head office in the Albacete Science and Technology Park, it manages the work of the 1,300 employees that make up its global workforce, rendering services to wind farms, PV installations and power generation plants. In addition, it maintains an active participation strategy in a range of R&D+i programmes that improve the existing technologies and are geared towards new production systems and new diagnostic techniques, applied to renewables installation maintenance. (Author)
Exchange rate predictability and state-of-the-art models
Yeșin, Pınar
2016-01-01
This paper empirically evaluates the predictive performance of the International Monetary Fund's (IMF) exchange rate assessments with respect to future exchange rate movements. The assessments of real trade-weighted exchange rates were conducted from 2006 to 2011, and were based on three state-of-the-art exchange rate models with a medium-term focus which were developed by the IMF. The empirical analysis using 26 advanced and emerging market economy currencies reveals that the "diagnosis" of ...
A Range-Based Multivariate Model for Exchange Rate Volatility
Tims, Ben; Mahieu, Ronald
2003-01-01
textabstractIn this paper we present a parsimonious multivariate model for exchange rate volatilities based on logarithmic high-low ranges of daily exchange rates. The multivariate stochastic volatility model divides the log range of each exchange rate into two independent latent factors, which are interpreted as the underlying currency specific components. Due to the normality of logarithmic volatilities the model can be estimated conveniently with standard Kalman filter techniques. Our resu...
Kravchenko, Olga; Thachuk, Mark
2011-03-21
A study is presented of tracer diffusion in a rough hard sphere fluid. Unlike smooth hard spheres, collisions between rough hard spheres can exchange rotational and translational energy and momentum. It is expected that as tracer particles become larger, their diffusion constants will tend toward the Stokes-Einstein hydrodynamic result. It has already been shown that in this limit, smooth hard spheres adopt "slip" boundary conditions. The current results show that rough hard spheres adopt boundary conditions proportional to the degree of translational-rotational energy exchange. Spheres for which this exchange is the largest adopt "stick" boundary conditions while those with more intermediate exchange adopt values between the "slip" and "stick" limits. This dependence is found to be almost linear. As well, changes in the diffusion constants as a function of this exchange are examined and it is found that the dependence is stronger than that suggested by the low-density, Boltzmann result. Compared with smooth hard spheres, real molecules undergo inelastic collisions and have attractive wells. Rough hard spheres model the effect of inelasticity and show that even without the presence of attractive forces, the boundary conditions for large particles can deviate from "slip" and approach "stick."
Shao, Haibing; Hein, Philipp; Bucher, Anke; Kolditz, Olaf
2017-04-01
In previous studies, the amount of shallow geothermal energy was estimated by assuming a uniform temperature drop of at least 2 °C in the aquifer. In this work, a more comprehensive numerical model has been employed to evaluate the technically exploitable geothermal energy by using Borehole Heat Exchanger coupled Ground Source Heat Pump systems. A case study on the city of Cologne was revisited, adopting the same hydrogeological conditions and simulating the long-term evolution of the subsurface temperature field subject to the operation of borehole heat exchangers. It is found that the cities' heating demand could potentially be fully covered by BHE-coupled GSHP systems. The resulting equivalent uniform temperature drop is then around 1.6 °C . It was also found that utilising geothermal energy will lead to at least 50% reduction of CO2 equivalent emission in comparison to conventional district heating, depending on the source of electricity used for heat pump operation.
Flow with vibrational energy exchange, application to CO2 electric laser
International Nuclear Information System (INIS)
Dahan, Claude.
1974-01-01
The performances of a continuous wave (CO 2 , N 2 , He) laser ionized by an electron beam are calculated. Several types of phenomena are considered: energy exchange processes between molecules of laser medium, electron molecular excitation processes, aerodynamic phenomena: the energy exchanges accompanying the laser effect generate important quantities of heat, which have to be evacuated by the flow. After a survey of the fundamental assumptions on molecular phenomena, a computer code was developed for following, along the flow, the evolution of the thermodynamic parameters (pressure, temperature), of the laser gain, and of the electrical properties (electron density and temperature). To provide a finer description of the last ones, a model giving the energy distribution of the electrons in the laser medium was established [fr
2011-02-03
... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. ER11-2730-000] Energy Exchange International, LLC; Supplemental Notice That Initial Market-Based Rate Filing Includes Request for... proceeding Energy Exchange International, LLC's application for market-based rate authority, with an...
Reducing the energy consumption of an earth–air heat exchanger with a PID control system
International Nuclear Information System (INIS)
Diaz-Mendez, S.E.; Patiño-Carachure, C.; Herrera-Castillo, J.A.
2014-01-01
Highlights: • The application of control actions to green technologies has been simulated. • Energy consumption of green technologies can be reduced even more. • The efficiency of green technologies can be raised. • Environmental concerns can be diminished. • The sustainability of the planet can be increased. - Abstract: Reducing environmental emissions is one of the challenges that human being has to overcome. It can only be reached with a proper energetic efficiency and management of the processes that exist in the society nowadays. Several academic works have mentioned that raising the efficiency of a process it also increases sustainability and in turn decreases the environmental impact. One process that requires much attention is the cooling and heating of buildings; this process contributes to the major part of the electric bill, in particular, if a conventional and old air conditioning is used as commonly occurs in many countries. In recent years there have been developed new alternatives that are used in few countries, such as the earth–air heat exchanger, where air is passed through a heat exchanger buried a few meters below the ground. The heat exchanger takes advantage of the well-known difference between the temperature of the surrounding air and the temperature of the ground for cooling or heating the air that is subsequently injected into the buildings. This process requires less energy, then in the present work is thought that a PID (Proportional, Integral and Derivative) controller can be applied to an earth–air heat exchanger to reduce even more the energy consumption. Therefore, a simulation of a thermodynamic model of an earth–air heat exchanger was done and used along with a PID controller, to estimate savings in energy consumption. The results show that the energy consumption can be reduced up to 87% with the PID control, hence the efficiency of the process is increased as well as the sustainability of the planet and thus the
A study of the charge-exchange reaction $pp \\to n\\Delta^{++} (1232)$ at ISR energies
De Kerret, H; Bartl, Walter; Brandt, A; Broll, C; Coignet, G; Dibon, Heinz; Eichinger, H; Favier, Jean; Flügge, G; Gottfried, Christian; Massonnet, Louis; Nagy, E; Neuhofer, G; Niebergall, F; Orr, R S; Regler, Meinhard; Schmidt-Parzefall, W; Schubert, K R; Schumacher, P E; Vivargent, M; Winter, Klaus
1977-01-01
A study is reported of the charge-exchange reaction pp to n Delta /sup ++/(1232) at the CERN intersecting storage rings (ISR) in the energy range square root s=23 to 53 GeV. From the analysis of the energy dependence of the total cross-section, of the differential cross- section d sigma /dt and of the decay angular distributions evidence is found that pion exchange is dominant up to square root s=23 GeV and that ( rho +A/sub 2/) exchange dominates the reaction for square root s>or=30 GeV, as described by simple Regge-pole models. (13 refs).
Information Exchange of the Atomic Energy Society of Japan with Nuclear Societies Worldwide
International Nuclear Information System (INIS)
Masao Hori; Yasushi Tomita
2000-01-01
This paper describes committees of the Atomic Energy Society of Japan (AESJ) related to information exchange, AESJ publications, AESJ Internet applications, and means for future information exchange between nuclear societies
Modeling Multi-commodity Trade Information Exchange Methods
Traczyk, Tomasz
2012-01-01
Market mechanisms are entering into new fields of economy, in which some constraints of physical world, e.g. Kirchoffs Law in power grid, must be taken into account during trading. On such markets, some of commodities, like telecommunication bandwidth or electrical energy, appear to be non-storable, and must be exchanged in real-time. On the other hand, the markets tend to react at shortest possible time, so an idea to delegate some competency to autonomous software agents is very attractive. Multi-commodity mechanism addresses the aforementioned requirements. Modeling the relationships between the commodities allows to formulate new, more sophisticated models and mechanisms, which reflect decision situations in a better manner. Application of multi-commodity approach requires solving several issues related to data modeling, communication, semantics aspects of communication, reliability, etc. This book answers some of the questions and points out promising paths for implementation and development. Presented s...
Low-energy magnetoelectric control of domain states in exchange-coupled heterostructures
Al-Mahdawi, Muftah; Pati, Satya Prakash; Shiokawa, Yohei; Ye, Shujun; Nozaki, Tomohiro; Sahashi, Masashi
2017-04-01
The electric manipulation of antiferromagnets has become an area of great interest recently for zero-stray-field spintronic devices, and for their rich spin dynamics. Generally, the application of antiferromagnetic media for information memories and storage requires a heterostructure with a ferromagnetic layer for readout through the exchange-bias field. In magnetoelectric and multiferroic antiferromagnets, the exchange coupling exerts an additional impediment (energy barrier) to magnetization reversal by the applied magnetoelectric energy. We proposed and verified a method to overcome this barrier. We controlled the energy required for switching the magnetic domains in magnetoelectric Cr2O3 films by compensating the exchange-coupling energy from the ferromagnetic layer with the Zeeman energy of a small volumetric spontaneous magnetization found for the sputtered Cr2O3 films. Based on a simplified phenomenological model of the field-cooling process, the magnetic and electric fields required for switching could be tuned. As an example, the switching of antiferromagnetic domains around a zero-threshold electric field was demonstrated at a magnetic field of 2.6 kOe.
Gas exchange and energy expenditure in chicken embryos
DEFF Research Database (Denmark)
Chwalibog, André; Tauson, Anne-Helene; Ali, Abdalla
. The pattern of curves for gas exchange was identical for RO and LA, but on a lower level for LA. The energy expenditure followed the pattern of curves for gas exchange, with a mean value around 50 J/h on day 10, increasing to 528 (RO) and 402 (LA) J/h on day 19 (Figure 1). The main source of EE was oxidized...... is independent of genetic origin of embryos. However, the embryos from the slow growing broiler line had a lower metabolic rate and oxidised less fat than the modern, fast growing line. The reduced utilization of yolk fat might be a tool for saving fat reserves for the immediate post-hatching period......) in this phase may be a crucial parameter predicting metabolic rate and consquently, growth performance of post-hatched chickens. The aim of this investigation was to determine EE in embryos of slow and fast growing lines of chickens. Taking advantage of the indirect calorimetry technique it was also possible...
On Kinetics Modeling of Vibrational Energy Transfer
Gilmore, John O.; Sharma, Surendra P.; Cavolowsky, John A. (Technical Monitor)
1996-01-01
Two models of vibrational energy exchange are compared at equilibrium to the elementary vibrational exchange reaction for a binary mixture. The first model, non-linear in the species vibrational energies, was derived by Schwartz, Slawsky, and Herzfeld (SSH) by considering the detailed kinetics of vibrational energy levels. This model recovers the result demanded at equilibrium by the elementary reaction. The second model is more recent, and is gaining use in certain areas of computational fluid dynamics. This model, linear in the species vibrational energies, is shown not to recover the required equilibrium result. Further, this more recent model is inconsistent with its suggested rate constants in that those rate constants were inferred from measurements by using the SSH model to reduce the data. The non-linear versus linear nature of these two models can lead to significant differences in vibrational energy coupling. Use of the contemporary model may lead to significant misconceptions, especially when integrated in computer codes considering multiple energy coupling mechanisms.
Gabor Fath; Miklos Sarvary
2001-01-01
B2B exchanges are revolutionizing the way businesses will buy and sell a variety of intermediary products and services. It is estimated that most of the roughly $7 trillion worth of business transactions are likely to go through these new institutions within the next decade. This paper tries to understand the economics governing the transactions within B2B exchanges and analyze their likely evolution over time. In doing so, we start by providing the rigorous definitions to a number of critica...
Low-energy pion double charge exchange and nucleon-nucleon correlations in nuclei
International Nuclear Information System (INIS)
Leitch, M.J.
1989-01-01
Recent measurements of pion double-charge exchange (DCX) at energies 20 to 70 MeV are providing a new means for studying nucleon-nucleon correlations in nuclei. At these energies the nucleus is relatively transparent, allowing simpler theoretical models to be used in interpreting the data and leading to a clearer picture. Also the contribution to DCX of sequential charge-exchange scattering through the intermediate analog state is suppressed near 50 MeV and transitions through non-analog intermediate states become very important. Recent theoretical studies by several groups have shown that while transitions through the analog route involve relatively long nucleon-nucleon distances, those through non-analog intermediate states obtain nearly half their strength from nucleon pairs with less than 1 fermi separation. Thus DCX near 50 MeV is an excellent way to study short-range nucleon-nucleon correlations. 31 refs., 29 figs., 4 tabs
Gaspard, Pierre; Gilbert, Thomas
2017-04-01
We present a systematic computation of the heat conductivity of the Markov jump process modeling the energy exchanges in an array of locally confined hard spheres at the conduction threshold. Based on a variational formula (Sasada 2016 (arXiv:1611.08866)), explicit upper bounds on the conductivity are derived, which exhibit a rapid power-law convergence towards an asymptotic value. We thereby conclude that the ratio of the heat conductivity to the energy exchange frequency deviates from its static contribution by a small negative correction, its dynamic contribution, evaluated to be -0.000 373 in dimensionless units. This prediction is corroborated by kinetic Monte Carlo simulations which were substantially improved compared to earlier results.
Low-energy pion double charge exchange and nucleon-nucleon correlations in nuclei
Energy Technology Data Exchange (ETDEWEB)
Leitch, M.J.
1989-01-01
Recent measurements of pion double-charge exchange (DCX) at energies 20 to 70 MeV are providing a new means for studying nucleon-nucleon correlations in nuclei. At these energies the nucleus is relatively transparent, allowing simpler theoretical models to be used in interpreting the data and leading to a clearer picture. Also the contribution to DCX of sequential charge-exchange scattering through the intermediate analog state is suppressed near 50 MeV and transitions through non-analog intermediate states become very important. Recent theoretical studies by several groups have shown that while transitions through the analog route involve relatively long nucleon-nucleon distances, those through non-analog intermediate states obtain nearly half their strength from nucleon pairs with less than 1 fermi separation. Thus DCX near 50 MeV is an excellent way to study short-range nucleon-nucleon correlations. 31 refs., 29 figs., 4 tabs.
Shapley Value-Based Payment Calculation for Energy Exchange between Micro- and Utility Grids
Directory of Open Access Journals (Sweden)
Robin Pilling
2017-10-01
Full Text Available In recent years, microgrids have developed as important parts of power systems and have provided affordable, reliable, and sustainable supplies of electricity. Each microgrid is managed as a single controllable entity with respect to the existing power system but demands for joint operation and sharing the benefits between a microgrid and its hosting utility. This paper is focused on the joint operation of a microgrid and its hosting utility, which cooperatively minimize daily generation costs through energy exchange, and presents a payment calculation scheme for power transactions based on a fair allocation of reduced generation costs. To fairly compensate for energy exchange between the micro- and utility grids, we adopt the cooperative game theoretic solution concept of Shapley value. We design a case study for a fictitious interconnection model between the Mueller microgrid in Austin, Texas and the utility grid in Taiwan. Our case study shows that when compared to standalone generations, both the micro- and utility grids are better off when they collaborate in power exchange regardless of their individual contributions to the power exchange coalition.
Modeling Philippine Stock Exchange Composite Index Using Time Series Analysis
Gayo, W. S.; Urrutia, J. D.; Temple, J. M. F.; Sandoval, J. R. D.; Sanglay, J. E. A.
2015-06-01
This study was conducted to develop a time series model of the Philippine Stock Exchange Composite Index and its volatility using the finite mixture of ARIMA model with conditional variance equations such as ARCH, GARCH, EG ARCH, TARCH and PARCH models. Also, the study aimed to find out the reason behind the behaviorof PSEi, that is, which of the economic variables - Consumer Price Index, crude oil price, foreign exchange rate, gold price, interest rate, money supply, price-earnings ratio, Producers’ Price Index and terms of trade - can be used in projecting future values of PSEi and this was examined using Granger Causality Test. The findings showed that the best time series model for Philippine Stock Exchange Composite index is ARIMA(1,1,5) - ARCH(1). Also, Consumer Price Index, crude oil price and foreign exchange rate are factors concluded to Granger cause Philippine Stock Exchange Composite Index.
Singh, A.; Strating, Alex T.; Romero Herrera, N.A.; van Dijk, Hylke W.; Keyson, D.V.
2017-01-01
Many energy researchers and practitioners envision householders to have an active role in local energy distribution in emerging energy systems. In the energy literature, the dominant view of local energy distribution, grounded in the rational choice perspective, sees exchanges of energy between
Modeling of Crystalline Silicotitanate Ion Exchange Columns
International Nuclear Information System (INIS)
Walker, D.D.
1999-01-01
Non-elutable ion exchange is being considered as a potential replacement for the In-Tank Precipitation process for removing cesium from Savannah River Site (SRS) radioactive waste. Crystalline silicotitanate (CST) particles are the reference ion exchange medium for the process. A major factor in the construction cost of this process is the size of the ion exchange column required to meet product specifications for decontaminated waste. To validate SRS column sizing calculations, SRS subcontracted two reknowned experts in this field to perform similar calculations: Professor R. G. Anthony, Department of Chemical Engineering, Texas A ampersand 038;M University, and Professor S. W. Wang, Department of Chemical Engineering, Purdue University. The appendices of this document contain reports from the two subcontractors. Definition of the design problem came through several meetings and conference calls between the participants and SRS personnel over the past few months. This document summarizes the problem definition and results from the two reports
Monetary models and exchange rate determination: The Nigerian ...
African Journals Online (AJOL)
Abstract. This paper estimates three different monetary models of exchange rate determination for the Nigerian economy using time series data. These include the Monetary ... Thus, the money supply process should be stable; otherwise, the exchange rate system in the country will be unstable. The policy significance in this ...
Rasch models with exchangeable rows and columns
DEFF Research Database (Denmark)
Lauritzen, Steffen Lilholt
The article studies distributions of doubly infinite binary matrices with exchangeable rows and columns which satify the further property that the probability of any $m \\times n$ submatrix is a function of the row- and column sums of that matrix. We show that any such distribution is a (unique...
STEP - Product Model Data Sharing and Exchange
DEFF Research Database (Denmark)
Kroszynski, Uri
1998-01-01
- Product Data Representation and Exchange", featuring at present some 30 released parts, and growing continuously. Many of the parts are Application Protocols (AP). This article presents an overview of STEP, based upon years of involvement in three ESPRIT projects, which contributed to the development...
Towards hot electron mediated charge exchange in hyperthermal energy ion-surface interactions
DEFF Research Database (Denmark)
Ray, M. P.; Lake, R. E.; Thomsen, Lasse Bjørchmar
2010-01-01
electrons useful for driving chemical reactions at surfaces. Using the binary collision approximation and a nonadiabatic model that takes into account the time-varying nature of the ion–surface interaction, the energy loss of the ions is reproduced. The energy loss for Na + ions incident on the devices......We have made Na + and He + ions incident on the surface of solid state tunnel junctions and measured the energy loss due to atomic displacement and electronic excitations. Each tunnel junction consists of an ultrathin film metal–oxide–semiconductor device which can be biased to create a band of hot...... shows that the primary energy loss mechanism is the atomic displacement of Au atoms in the thin film of the metal–oxide–semiconductor device. We propose that neutral particle detection of the scattered flux from a biased device could be a route to hot electron mediated charge exchange....
Modelling and validation of Proton exchange membrane fuel cell (PEMFC)
Mohiuddin, A. K. M.; Basran, N.; Khan, A. A.
2018-01-01
This paper is the outcome of a small scale fuel cell project. Fuel cell is an electrochemical device that converts energy from chemical reaction to electrical work. Proton Exchange Membrane Fuel Cell (PEMFC) is one of the different types of fuel cell, which is more efficient, having low operational temperature and fast start up capability results in high energy density. In this study, a mathematical model of 1.2 W PEMFC is developed and simulated using MATLAB software. This model describes the PEMFC behaviour under steady-state condition. This mathematical modeling of PEMFC determines the polarization curve, power generated, and the efficiency of the fuel cell. Simulation results were validated by comparing with experimental results obtained from the test of a single PEMFC with a 3 V motor. The performance of experimental PEMFC is little lower compared to simulated PEMFC, however both results were found in good agreement. Experiments on hydrogen flow rate also been conducted to obtain the amount of hydrogen consumed to produce electrical work on PEMFC.
Transverse-to-longitudinal Emittance-exchange with an Energy Chirped Beam
Energy Technology Data Exchange (ETDEWEB)
Thangaraj, J.; Ruan, J.; Johnson, A.S.; Thurman-Keup, R.; Lumpkin, A.H.; Santucci, J.; Sun, Y.-E; Maxwell, T.; Edwards, H.; /Fermilab
2012-05-01
Emittance exchange has been proposed to increase the performance of free electron lasers by tailoring the phase space of an electron beam. The principle of emittance exchange - where the transverse phase space of the electron beam is exchanged with the longitudinal phase space - has been demonstrated recently at the A0 photoinjector. The experiment used a low charge bunch (250 pC) with no energy chirp. Theory predicts an improvement in the emittance exchange scheme when the incoming beam has an energy chirp imparted on it. The energy chirp helps to overcome the thick lens effect of the deflecting mode cavity and other second order effects that might lead to an incomplete emittance exchange at higher charges. In this work, we report experimental and simulation results from operating the emittance exchange beam line using an energy chirped beam with higher charge (500 pC) at different RF-chirp settings.
Role of energy exchange in vibrational dephasing processes in liquids and solids
International Nuclear Information System (INIS)
Marks, S.
1981-08-01
Three theories which claim relevance to the dephasing of molecular vibrations in condensed phase matter are presented. All of these theories predict (in certain limiting cases) that the widths and shifts of molecular vibrations will obey an Arrhenius temperature dependence. The basic tenets of the theories are detailed so that the differences between them may be used in an experiment to distinguish between them. One model, based on intermolecular energy exchange of low-frequency modes, results in dephasing the high-frequency modes when anharmonic coupling is present. A computer analysis of temperature dependent experimental lineshapes can result in the extraction of various parameters such as the anharmonic shifts and the exchange rates. It is shown that, in order to properly assess the relative validity of the three models, other evidence must be obtained such as the spectral parameters of the low-frequency modes, the combination bands, and the isotopic dilution behavior. This evidence is presented for d 14 -durene (perdeutero-1,2,4,5-tetramethylbenzene) and compared to previous data obtained on pure h 14 -durene. An extension of the (HSC) intermolecular energy exchange model which allows for the possibility of partial delocalization of the low-frequency modes gives an adequate description of the experimental evidence. Isotopic dilution experiments, in particular, have resulted in a detailed picture of the energy transfer dynamics of the low-frequency modes. A section in which some spontaneous Raman spectra support a model of inhomogeneous broadening in liquids based on results of picosecond stimulated Raman spectroscopy is presented. The model is that a distribution of environmental sites is created by a distribution in the local density and thus creates inhomogeneous broadening
Track structure for low energy ions including charge exchange processes
International Nuclear Information System (INIS)
Uehara, S.; Nikjoo, H.
2002-01-01
The model and development is described of a new generation of Monte Carlo track structure codes. The code LEAHIST simulates full slowing down of low-energy proton history tracks in the range 1 keV-1 MeV and the code LEAHIST simulates low-energy alpha particle history tracks in the range 1 keV-8 MeV in water. All primary ion interactions are followed down to 1 keV and all electrons to 1 eV. Tracks of secondary electrons ejected by ions were traced using the electron code KURBUC. Microdosimetric parameters derived by analysis of generated tracks are presented. (author)
North, G. R.; Cahalan, R. F.; Coakley, J. A., Jr.
1981-01-01
An introductory survey of the global energy balance climate models is presented with an emphasis on analytical results. A sequence of increasingly complicated models involving ice cap and radiative feedback processes are solved, and the solutions and parameter sensitivities are studied. The model parameterizations are examined critically in light of many current uncertainties. A simple seasonal model is used to study the effects of changes in orbital elements on the temperature field. A linear stability theorem and a complete nonlinear stability analysis for the models are developed. Analytical solutions are also obtained for the linearized models driven by stochastic forcing elements. In this context the relation between natural fluctuation statistics and climate sensitivity is stressed.
Energy Exchange Dynamics across L-H transitions in NSTX
Diallo, Ahmed
2017-10-01
H-mode is planned for future devices such as ITER, and is preceded by a low (L) to high (H) transition. A key question remains. What is the mechanism behind the L-H transition? Most theoretical descriptions of the L-H transition are based on the shear of the radial electric field and coincident ExB poloidal flow shear, which is thought to be responsible for the onset of the anomalous transport suppression that leads to the L-H transition. This talk will focus on the analysis of the flow dynamics across the L-H transition in NSTX. We analyze the L-H transition dynamics using the velocimetry of 2D edge turbulence data from gas-puff imaging (GPI). We determine the velocity components at the edge across the L-H transition for 17 discharges with three types of heating power (NBI, ohmic, and RF). Using a reduced model equation of edge flows and turbulence, the energy transfer dynamics is compared with the turbulence depletion hypothesis of the predator-prey model. In order for Reynolds work to suppress the turbulence, it must deplete the total turbulent free energy, including the thermal free-energy term. For this to occur, the increase in kinetic energy in the mean flow over the L-H transition must be comparable to the pre-transition thermal free energy. However, this ratio was found to be of order 10-2. Although there are significant simplifications in the theoretical model, they are unlikely to cause inaccuracy by two orders of magnitude, suggesting that direct turbulence depletion by the Reynolds work may not be large enough to explain the L-H transition on NSTX, contrary to the predator-prey model. This work is supported by the US DOE Contract No. DE-AC02-09CH11466.
Modeling canopy CO2 exchange in the European Russian Arctic
DEFF Research Database (Denmark)
Kiepe, Isabell; Friborg, Thomas; Herbst, Mathias
2013-01-01
In this study, we use the coupled photosynthesis-stomatal conductance model of Collatz et al. (1991) to simulate the current canopy carbon dioxide exchange of a heterogeneous tundra ecosystem in European Russia. For the parameterization, we used data obtained from in situ leaf level measurements...... in combination with meteorological data from 2008. The modeled CO2 fluxes were compared with net ecosystem exchange (NEE), measured by the eddy covariance technique during the snow-free period in 2008. The findings from this study indicated that the main state parameters of the exchange processes were leaf area...
Optimal model of radiocarbon residence time in exchange reservoir
International Nuclear Information System (INIS)
Dergachev, V.A.
1977-01-01
Radiocarbon content variations in the earth atmosphere were studied using a mathematical model. The so-called exchange reservoir was considered consisting of layers, and the radiocarbon exchange rate at the interfaces between these layers was supposed to be constant. The process of 14 C mixing and exchange in a dynamic system is described by a system of nonhomogeneous 1st order differential equations. The model also accounts for the change in rate of radiocarbon formation in the earth atmosphere due to cosmic and geophysical effects (solar activity, solar cycle, etc.). (J.P.)
Energy exchange in systems of particles with nonreciprocal interaction
Energy Technology Data Exchange (ETDEWEB)
Vaulina, O. S.; Lisina, I. I., E-mail: Irina.Lisina@mail.ru; Lisin, E. A. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)
2015-10-15
A model is proposed to describe the sources of additional kinetic energy and its redistribution in systems of particles with a nonreciprocal interaction. The proposed model is shown to explain the qualitative specific features of the dust particle dynamics in the sheath region of an RF discharge. Prominence is given to the systems of particles with a quasi-dipole–dipole interaction, which is similar to the interaction induced by the ion focusing effects that occur in experiments on a laboratory dusty plasma, and with the shadow interaction caused by thermophoretic forces and Le Sage’s forces.
Energy model in regional energy system
International Nuclear Information System (INIS)
Mura, P.G.; Baccoli, R.; Carlini, U.; Innamorati, R.; Mariotti, S.
2005-01-01
In this report is presented a computational model for analysis of energy, materials and mass flux in a complex energy system, at regional scale level. Specifically is described a calculation model of electric power generation for emission forecasting of CO 2 , SO x , NO x , particulate matter, ashes, limestone, chalks [it
Varlamov, Gennadii Borysovich; Romanova, Kateryna Alexandrovna; Nazarova, Iryna; Daschenko, Olga; Kapustiansky, Andry
2017-12-01
Energy efficiency improvement and ecological safety of heat power plants are urgent problems, which require scientifically grounded approaches and solutions. These problems can be solved partly within the presented heat-and-power cycles by including contact energy exchange equipment in the circuits of existing installations. A significant positive effect is obtained in the contact energy exchange installations, such as gas-steam installation `Aquarius' and the contact hydrogen heat generator that also can use hydrogen as a fuel. In these plants, the efficiency increases approximately by 10-12% in comparison with traditional installations, and the concentration of toxic substances, such as nitrogen oxides and carbon monoxide in flue gas can be reduced to 30 mg/m3 and to 5 mg/m3, respectively. Moreover, the plants additionally `generate' the clean water, which can be used for technical purposes.
Directory of Open Access Journals (Sweden)
Varlamov Gennadii Borysovich
2017-12-01
Full Text Available Energy efficiency improvement and ecological safety of heat power plants are urgent problems, which require scientifically grounded approaches and solutions. These problems can be solved partly within the presented heat-and-power cycles by including contact energy exchange equipment in the circuits of existing installations. A significant positive effect is obtained in the contact energy exchange installations, such as gas-steam installation ‘Aquarius’ and the contact hydrogen heat generator that also can use hydrogen as a fuel. In these plants, the efficiency increases approximately by 10-12% in comparison with traditional installations, and the concentration of toxic substances, such as nitrogen oxides and carbon monoxide in flue gas can be reduced to 30 mg/m3 and to 5 mg/m3, respectively. Moreover, the plants additionally ‘generate’ the clean water, which can be used for technical purposes.
Rose, K.; Rowan, C.; Rager, D.; Dehlin, M.; Baker, D. V.; McIntyre, D.
2015-12-01
Multi-organizational research teams working jointly on projects often encounter problems with discovery, access to relevant existing resources, and data sharing due to large file sizes, inappropriate file formats, or other inefficient options that make collaboration difficult. The Energy Data eXchange (EDX) from Department of Energy's (DOE) National Energy Technology Laboratory (NETL) is an evolving online research environment designed to overcome these challenges in support of DOE's fossil energy goals while offering improved access to data driven products of fossil energy R&D such as datasets, tools, and web applications. In 2011, development of NETL's Energy Data eXchange (EDX) was initiated and offers i) a means for better preserving of NETL's research and development products for future access and re-use, ii) efficient, discoverable access to authoritative, relevant, external resources, and iii) an improved approach and tools to support secure, private collaboration and coordination between multi-organizational teams to meet DOE mission and goals. EDX presently supports fossil energy and SubTER Crosscut research activities, with an ever-growing user base. EDX is built on a heavily customized instance of the open source platform, Comprehensive Knowledge Archive Network (CKAN). EDX connects users to externally relevant data and tools through connecting to external data repositories built on different platforms and other CKAN platforms (e.g. Data.gov). EDX does not download and repost data or tools that already have an online presence. This leads to redundancy and even error. If a relevant resource already has an online instance, is hosted by another online entity, EDX will point users to that external host either using web services, inventorying URLs and other methods. EDX offers users the ability to leverage private-secure capabilities custom built into the system. The team is presently working on version 3 of EDX which will incorporate big data analytical
Directory of Open Access Journals (Sweden)
Ren Yuan
2016-01-01
Full Text Available Current research status in energy management of Proton Exchange Membrane (PEM fuel cell hybrid power electric vehicles are first described in this paper, and then build the PEMFC/ lithium-ion battery/ ultra-capacitor hybrid system model. The paper analysis the key factors of the continuous power available in PEM fuel cell hybrid power electric vehicle and hybrid power system working status under different driving modes. In the end this paper gives the working flow chart of the hybrid power system and concludes the three items of the system performance analysis.
Modeling ion exchange in clinoptilolite using the EQ3/6 geochemical modeling code
International Nuclear Information System (INIS)
Viani, B.E.; Bruton, C.J.
1992-06-01
Assessing the suitability of Yucca Mtn., NV as a potential repository for high-level nuclear waste requires the means to simulate ion-exchange behavior of zeolites. Vanselow and Gapon convention cation-exchange models have been added to geochemical modeling codes EQ3NR/EQ6, allowing exchange to be modeled for up to three exchangers or a single exchanger with three independent sites. Solid-solution models that are numerically equivalent to the ion-exchange models were derived and also implemented in the code. The Gapon model is inconsistent with experimental adsorption isotherms of trace components in clinoptilolite. A one-site Vanselow model can describe adsorption of Cs or Sr on clinoptilolite, but a two-site Vanselow exchange model is necessary to describe K contents of natural clinoptilolites
A lumped parameter, low dimension model of heat exchanger
International Nuclear Information System (INIS)
Kanoh, Hideaki; Furushoo, Junji; Masubuchi, Masami
1980-01-01
This paper reports on the results of investigation of the distributed parameter model, the difference model, and the model of the method of weighted residuals for heat exchangers. By the method of weighted residuals (MWR), the opposite flow heat exchanger system is approximated by low dimension, lumped parameter model. By assuming constant specific heat, constant density, the same form of tube cross-section, the same form of the surface of heat exchange, uniform flow velocity, the linear relation of heat transfer to flow velocity, liquid heat carrier, and the thermal insulation of liquid from outside, fundamental equations are obtained. The experimental apparatus was made of acrylic resin. The response of the temperature at the exit of first liquid to the variation of the flow rate of second liquid was measured and compared with the models. The MWR model shows good approximation for the low frequency region, and as the number of division increases, good approximation spreads to higher frequency region. (Kato, T.)
Policy modeling for industrial energy use
Energy Technology Data Exchange (ETDEWEB)
Worrell, Ernst; Park, Hi-Chun; Lee, Sang-Gon; Jung, Yonghun; Kato, Hiroyuki; Ramesohl, Stephan; Boyd, Gale; Eichhammer, Wolfgang; Nyboer, John; Jaccard, Mark; Nordqvist, Joakim; Boyd, Christopher; Klee, Howard; Anglani, Norma; Biermans, Gijs
2003-03-01
The international workshop on Policy Modeling for Industrial Energy Use was jointly organized by EETA (Professional Network for Engineering Economic Technology Analysis) and INEDIS (International Network for Energy Demand Analysis in the Industrial Sector). The workshop has helped to layout the needs and challenges to include policy more explicitly in energy-efficiency modeling. The current state-of-the-art models have a proven track record in forecasting future trends under conditions similar to those faced in the recent past. However, the future of energy policy in a climate-restrained world is likely to demand different and additional services to be provided by energy modelers. In this workshop some of the international models used to make energy consumption forecasts have been discussed as well as innovations to enable the modeling of policy scenarios. This was followed by the discussion of future challenges, new insights in the data needed to determine the inputs into energy model s, and methods to incorporate decision making and policy in the models. Based on the discussion the workshop participants came to the following conclusions and recommendations: Current energy models are already complex, and it is already difficult to collect the model inputs. Hence, new approaches should be transparent and not lead to extremely complex models that try to ''do everything''. The model structure will be determined by the questions that need to be answered. A good understanding of the decision making framework of policy makers and clear communication on the needs are essential to make any future energy modeling effort successful. There is a need to better understand the effects of policy on future energy use, emissions and the economy. To allow the inclusion of policy instruments in models, evaluation of programs and instruments is essential, and need to be included in the policy instrument design. Increased efforts are needed to better understand the
Quasi-steady-state model of a counter flow air-to-air heat exchanger with phase change
DEFF Research Database (Denmark)
Rose, Jørgen; Nielsen, Toke Rammer; Kragh, Jesper
2008-01-01
Using mechanical ventilation with highly efficient heat-recovery in northern European or arctic climates is a very efficient way of reducing the energy use for heating in buildings. However, it also presents a series of problems concerning condensation and frost formation in the heat......-exchanger. Developing highly efficient heat-exchangers and strategies to avoid/remove frost formation implies the use of detailed models to predict and evaluate different heat-exchanger designs and strategies. This paper presents a quasi-steady-state model of a counter-flow air-to-air heat-exchanger that takes...... into account the effects of condensation and frost formation. The model is developed as an Excel spreadsheet, and specific results are compared with laboratory measurements. As an example, the model is used to determine the most energy-efficient control strategy for a specific heat-exchanger under northern...
Multiphysics Numerical Modeling of a Fin and Tube Heat Exchanger
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph
2015-01-01
In the present research work, a modeling effort to predict the performance of a liquid-gas type fin and tube heat exchanger design is made. Three dimensional (3D) steady state numerical model is developed using commercial software COMSOL Multiphysics based on finite element method (FEM). For the ......In the present research work, a modeling effort to predict the performance of a liquid-gas type fin and tube heat exchanger design is made. Three dimensional (3D) steady state numerical model is developed using commercial software COMSOL Multiphysics based on finite element method (FEM...
Giesbertz, K.J.H.; van Leeuwen, Robert; von Barth, Ulf
We put forward an approach for the development of a nonlocal density functional by a direct modeling of the shape of exchange-correlation (xc) hole in inhomogeneous systems. The functional is aimed at giving an accurate xc energy and an accurate corresponding xc potential even in difficult
A two-gluon exchange model of elastic scattering
International Nuclear Information System (INIS)
Richards, D.G.
1985-01-01
A two-gluon exchange (2GE) model of elastic hadron-hadron scattering is presented employing scalar quarks to facilitate the construction of a simple yet realistic hadronic wave function. The amplitude is calculated both in the forward direction and for non-zero values of t, and the results compared with that generated by pomeron exchange calculations which currently provide the best description of the data. (orig.)
A stochastic modeling of isotope exchange reactions in glutamine synthetase
Kazmiruk, N. V.; Boronovskiy, S. E.; Nartsissov, Ya R.
2017-11-01
The model presented in this work allows simulation of isotopic exchange reactions at chemical equilibrium catalyzed by a glutamine synthetase. To simulate the functioning of the enzyme the algorithm based on the stochastic approach was applied. The dependence of exchange rates for 14C and 32P on metabolite concentration was estimated. The simulation results confirmed the hypothesis of the ascertained validity for preferred order random binding mechanism. Corresponding values of K0.5 were also obtained.
Real Exchange Rate and Productivity in an OLG Model
Thi Hong Thinh DOAN; Karine GENTE
2013-01-01
This article develops an overlapping generations model to show how demography and savings affect the relationship between real exchange rate (RER) and productivity. In high-saving (low-saving) countries and/or low-population-growth-rate countries, a rise in productivity leads to a real depreciation (appreciation) whereas the RER may appreciate or depreciate in highproduction-growth-rate. Using panel data, we conclude that a rise in productivity generally causes a real exchange rate appreciati...
Thermal performance modeling of cross-flow heat exchangers
Cabezas-Gómez, Luben; Saíz-Jabardo, José Maria
2014-01-01
This monograph introduces a numerical computational methodology for thermal performance modeling of cross-flow heat exchangers, with applications in chemical, refrigeration and automobile industries. This methodology allows obtaining effectiveness-number of transfer units (e-NTU) data and has been used for simulating several standard and complex flow arrangements configurations of cross-flow heat exchangers. Simulated results have been validated through comparisons with results from available exact and approximate analytical solutions. Very accurate results have been obtained over wide ranges
DEFF Research Database (Denmark)
Nielsen, Toke Rammer; Rose, Jørgen; Kragh, Jesper
2009-01-01
must be calculated under conditions with condensation and freezing. This article presents a dynamic model of a counter flow air to air heat exchanger taking into account condensation and freezing and melting of ice. The model is implemented in Simulink and results are compared to measurements......In cold climates heat recovery in the ventilation system is essential to reduce heating energy demand. Condensation and freezing occur often in efficient heat exchangers used in cold climates. To develop efficient heat exchangers and defrosting strategies for cold climates, heat and mass transfer...... on a prototype heat exchanger for cold climates....
A phenomenological study of the π- p → π0 n charge exchange reaction at high energy
International Nuclear Information System (INIS)
Michaud, Y.
1995-01-01
The aim of the study was to examine the behaviour of the proton-proton elastic scattering, for mass center energies around 10 GeV, and more especially to study the charge exchange reaction π - p → π 0 n for mass center energies between 3 and 20 GeV. A formalism based on the Glauber model has been used, and a Regge trajectory exchange term was introduced in the model in order to enable the description of the lower energy domain (inferior to 10 GeV) that is characterized by a large contribution of meson exchanges at the scattering amplitude. The Glauber model is then applied to the charge exchange reaction and the differential cross section is analyzed for a center mass energy comprised between 3 and 20 GeV, together with the polarization at 40 GeV/c. The approach is then validated through the study of the π - p → η n reaction. The size of the kernel of proton and pion components implied in the π - p → π 0 n reaction, is also investigated. 90 refs., 48 figs., 4 tabs., 5 appends
Comparison of Moving Boundary and Finite-Volume Heat Exchanger Models in the Modelica Language
Directory of Open Access Journals (Sweden)
Adriano Desideri
2016-05-01
Full Text Available When modeling low capacity energy systems, such as a small size (5–150 kWel organic Rankine cycle unit, the governing dynamics are mainly concentrated in the heat exchangers. As a consequence, the accuracy and simulation speed of the higher level system model mainly depend on the heat exchanger model formulation. In particular, the modeling of thermo-flow systems characterized by evaporation or condensation requires heat exchanger models capable of handling phase transitions. To this aim, the finite volume (FV and the moving boundary (MB approaches are the most widely used. The two models are developed and included in the open-source ThermoCycle Modelica library. In this contribution, a comparison between the two approaches is presented. An integrity and accuracy test is designed to evaluate the performance of the FV and MB models during transient conditions. In order to analyze how the two modeling approaches perform when integrated at a system level, two organic Rankine cycle (ORC system models are built using the FV and the MB evaporator model, and their responses are compared against experimental data collected on an 11 kWel ORC power unit. Additionally, the effect of the void fraction value in the MB evaporator model and of the number of control volumes (CVs in the FV one is investigated. The results allow drawing general guidelines for the development of heat exchanger dynamic models involving two-phase flows.
CONTINUOUS MODELING OF FOREIGN EXCHANGE RATE OF USD VERSUS TRY
Directory of Open Access Journals (Sweden)
Yakup Arı
2011-01-01
Full Text Available This study aims to construct continuous-time autoregressive (CAR model and continuous-time GARCH (COGARCH model from discrete time data of foreign exchange rate of United States Dollar (USD versus Turkish Lira (TRY. These processes are solutions to stochastic differential equation Lévy-driven processes. We have shown that CAR(1 and COGARCH(1,1 processes are proper models to represent foreign exchange rate of USD and TRY for different periods of time February 2002- June 2010.
Dimensional Analysis of Ocean Thermal Energy Conversion Heat Exchangers
1977-06-30
34Utilisation des Forces Naturelles ," Avenir de l’dlectricit6, Revue Scientifigue, pp 370- 372 (Sept. 17, 1881). 2 Claude, Georges, "Power From the...34 fluid side of heat exchanger 11. Convective heat transfer MT" 3 -1 coefficient of working fluid WF 12. Specific heat of working fluid C L2Te" p WY 13...Viscosity of sea water MT 1 L 12. Sea water pressure drop through AtP MT- 2 L-1 -heat exchanger SW 13. Sea water convective heat h MT- 3 e 1 transfer
Modeling Exchange Rate Heteroskedasticity in Nigeria (1986-2008 ...
African Journals Online (AJOL)
On this basis, the study modelled the consistency and persistency of exchange rate hetroskedasticity of Nigerian currency (naira) vis-a-vis the United State dollar using monthly time series data from 1986 to 2008. The ARCH and GARCH models were used to examine the degree of volatility using the first difference, standard ...
Robustness of Component Models in Energy System Simulators
DEFF Research Database (Denmark)
Elmegaard, Brian
2003-01-01
). Others have to do with the interaction between models of the nature of the substances in an energy system (e.g., fuels, air, flue gas), models of the components in a system (e.g., heat exchangers, turbines, pumps), and the solver for the system of equations. This paper proposes that the interaction...... evaluated where it is defined. Outside this region an algorithm is introduced, so the model iterates back to the feasible region. It is shown how this can be done for four different model of energy system component models: turbine constant, gasifier, heat exchanger effectiveness, and heat exchanger heat......During the development of the component-based energy system simulator DNA (Dynamic Network Analysis), several obstacles to easy use of the program have been observed. Some of these have to do with the nature of the program being based on a modelling language, not a graphical user interface (GUI...
Modeling of cesium sorption on biotite using cation exchange selectivity coefficients
Energy Technology Data Exchange (ETDEWEB)
Kylloenen, Jarkko; Hakanen, Martti; Harjula, Risto; Lehto, Jukka [Helsinki Univ. (Finland). Lab. of Radiochemistry; Lindberg, Antero [Geological Survey of Finland, Espoo (Finland); Vehkamaeki, Marko [Helsinki Univ. (Finland). Lab. of Inorganic Chemistry
2014-07-01
For the modeling of cesium sorption on biotite, samples of natural biotite separated from gneissic rocks were converted into monoionic potassium, sodium, and calcium forms, and sorption isotherms for Cs/K, Cs/Na and Cs/Ca exchange were determined at pH 6 and 8 in 10{sup -4}-10{sup -8} M Cs solutions. Selectivity coefficients for Cs/K, Cs/Na, and Cs/Ca ion exchange reactions were calculated from the isotherm data, using the Gaines-Thomas convention. At Cs loadings below 1% of the total ion exchange capacity, the overall selectivity coefficient for Cs/Ca exchange was approximately five and seven orders of magnitude higher than those for Cs/Na and Cs/K exchange, respectively. Based on the selectivity coefficients, the ion exchange isotherms were modeled with the U.S. Geological Survey PhreeqC program, assuming three different types of ion exchange site: sites on the basal planes on biotite crystal surfaces with 95% site abundance, probable interlayer sites on crystal edges [frayed edge sites (FESs)] (0.02%) and third-type sites (5%), the physical background of which is unclear. Of these three types, the FES sites were superior in Cs selectivity, while the planar sites exhibited the lowest selectivity, and the third-type sites had selectivity between these two. The functionality of the model was successfully verified by modeling the Cs sorption isotherms on crushed mica gneiss rock in saline groundwater. Determination of the exchangeable ions K, Na, Ca, and Cs on the basal plane and edge surfaces by scanning electron microscopy-energy-dispersive x-ray spectroscopy (SEM-EDX) supports the results of modeling: edge sites highly prefer Cs ions and also Ca and Na ions but not K ions.
Flight Dynamic Model Exchange using XML
Jackson, E. Bruce; Hildreth, Bruce L.
2002-01-01
The AIAA Modeling and Simulation Technical Committee has worked for several years to develop a standard by which the information needed to develop physics-based models of aircraft can be specified. The purpose of this standard is to provide a well-defined set of information, definitions, data tables and axis systems so that cooperating organizations can transfer a model from one simulation facility to another with maximum efficiency. This paper proposes using an application of the eXtensible Markup Language (XML) to implement the AIAA simulation standard. The motivation and justification for using a standard such as XML is discussed. Necessary data elements to be supported are outlined. An example of an aerodynamic model as an XML file is given. This example includes definition of independent and dependent variables for function tables, definition of key variables used to define the model, and axis systems used. The final steps necessary for implementation of the standard are presented. Software to take an XML-defined model and import/export it to/from a given simulation facility is discussed, but not demonstrated. That would be the next step in final implementation of standards for physics-based aircraft dynamic models.
A Continuous-Time Model for Valuing Foreign Exchange Options
Directory of Open Access Journals (Sweden)
James J. Kung
2013-01-01
Full Text Available This paper makes use of stochastic calculus to develop a continuous-time model for valuing European options on foreign exchange (FX when both domestic and foreign spot rates follow a generalized Wiener process. Using the dollar/euro exchange rate as input for parameter estimation and employing our FX option model as a yardstick, we find that the traditional Garman-Kohlhagen FX option model, which assumes constant spot rates, values incorrectly calls and puts for different values of the ratio of exchange rate to exercise price. Specifically, it undervalues calls when the ratio is between 0.70 and 1.08, and it overvalues calls when the ratio is between 1.18 and 1.30, whereas it overvalues puts when the ratio is between 0.70 and 0.82, and it undervalues puts when the ratio is between 0.86 and 1.30.
Probabilities of vibrational energy exchange between carbon dioxide and carbon tetrafluoride
International Nuclear Information System (INIS)
Manzanares I, C.; Colon, E.
1984-01-01
The deactivation rate constant of CO 2 (ν 3 ) in mixtures with CF 4 has been measured at 298 K. A pulsed CO 2 laser was used to excite the CO 2 molecules. To interpret the mechanism of energy exchange, the probabilities of V--V energy transfer for CO 2 --CF 4 mixtures and the V-T self-relaxation of CF 4 (ν 2 ) were calculated. The model used considers a Morse potential to describe the interaction between the molecules and the quantum mechanical first order distorted wave approximation to calculate the probabilities. Order of magnitude agreement between the experimental and calculated results for CO 2 --CF 4 mixtures and for the CF 4 (ν 2 ) self-relaxation is obtained
Energy models: methods and trends
International Nuclear Information System (INIS)
Reuter, A.; Kuehner, R.; Wohlgemuth, N.
1996-01-01
Energy environmental and economical systems do not allow for experimentation since this would be dangerous, too expensive or even impossible. Instead, mathematical models are applied for energy planning. Experimenting is replaced by varying the structure and some parameters of 'energy models', computing the values of depending parameters, comparing variations, and interpreting their outcomings. Energy models are as old as computers. In this article the major new developments in energy modeling will be pointed out. We distinguish between 3 reasons of new developments: progress in computer technology, methodological progress and novel tasks of energy system analysis and planning
A Lattice-Boltzmann model for simulating bedform-induced hyporheic exchange
Dapelo, D.; Bridgeman, J.; Krause, S.
2016-12-01
Bedform-induced hyporheic exchange plays a fundamental role in the ecohydrological and biogeochemical functioning of aquifer-river interfaces. The understanding of the complex interchange of hyporheic exchange fluxes, solute and energy transport between surface and groundwater is fundamental to design effective management, restoration and pollution mitigation strategies. For the first time, the Lattice-Boltzmann method was used to simulate 2D hyporheic exchange flow across a succession of dunes. The velocity field in both surface and groundwater was simulated directly; then, residence times were computed through post-processing. As a novelty to most previous applications of similar computational fluid dynamics models, a grid-independence test was performed for to analyse independence of the results from the mesh choice. The Lattice-Boltzmann simulation results are compared to previous fluid dynamic models of similar bedforms, and the impact of the bedform on hyporheic exchange flow dynamics is discussed. As an advantage, both the free-flow and the hyporheic exchange flow are simulated within the same model, thus removing the need of developing two distinct models as well as the coupling between them: the model dynamically reproduces turbulent Navier-Stokes (surface water) or generalized Darcian (groundwater) flow, depending only on the local value of the porosity field. Through this model, the critical advantages of the Lattice-Boltzmann method, consisting of unparalleled computational parsimony, meshing simplicity and attitude towards diffuse computing, are made available for a wide range of similar applications.
International Nuclear Information System (INIS)
Inan, Aslan; Izgi, Ercan; Ay, Selim
2009-01-01
In this paper, to what extent a cogeneration system's fixed and variable costs and profits are affected from the exchange rate model implemented in the country is examined. An autoproductor system, as known, uses a part of its electrical energy production for its own requirements while selling the remaining energy to the regional energy corporation. As a function of the load factor and the fuel cost, the production cost and energy sale income of the system are influenced much by the exchange rate model of the country. A cost analysis of a natural gas cogeneration (autoproductor) system has been performed for the numerical application, based on the monetary program supported by the IMF commenced in January 2000. In order to investigate the effect of the change in exchange rate model (introducing the floating exchange rate model) on the fuel cost, both the characteristics of the IMF program and some various forecasting methods have been utilized
Thermal energy storage heat exchanger: Molten salt heat exchanger design for utility power plants
Ferarra, A.; Yenetchi, G.; Haslett, R.; Kosson, R.
1977-01-01
Sizing procedures are presented for latent heat thermal energy storage systems that can be used for electric utility off-peak energy storage, solar power plants and other preliminary design applications.
Information exchange of the Atomic Energy Society of Japan with nuclear societies worldwide
International Nuclear Information System (INIS)
Hori, Masao; Tomita, Yasushi
2000-01-01
The Atomic Energy Society of Japan (AESJ) exchanges information with nuclear societies worldwide by intersocietal communication through international councils of nuclear societies and through bilateral agreements between foreign societies and by such media as international meetings, publications, and Internet applications
Predicted and measured velocity distribution in a model heat exchanger
International Nuclear Information System (INIS)
Rhodes, D.B.; Carlucci, L.N.
1984-01-01
This paper presents a comparison between numerical predictions, using the porous media concept, and measurements of the two-dimensional isothermal shell-side velocity distributions in a model heat exchanger. Computations and measurements were done with and without tubes present in the model. The effect of tube-to-baffle leakage was also investigated. The comparison was made to validate certain porous media concepts used in a computer code being developed to predict the detailed shell-side flow in a wide range of shell-and-tube heat exchanger geometries
Double and super-exchange model in one-dimensional systems
International Nuclear Information System (INIS)
Vallejo, E.; Navarro, O.; Avignon, M.
2010-01-01
We present an analytical and numerical study of the competition between double and super-exchange interactions in a one-dimensional model. For low super-exchange interaction energy we find phase separation between ferromagnetic and anti-ferromagnetic phases. When the super-exchange interaction energy gets larger, the conduction electrons are self-trapped within separate small magnetic polarons. These magnetic polarons contain a single electron inside two or three sites depending on the conduction electron density and form a Wigner crystallization. A new phase separation is found between these small polarons and the anti-ferromagnetic phase. Spin-glass behavior is obtained consistent with experimental results of the nickelate one-dimensional compound Y 2-x Ca x BaNiO 5 .
Towards low carbon business park energy systems: Classification of techno-economic energy models
International Nuclear Information System (INIS)
Timmerman, Jonas; Vandevelde, Lieven; Van Eetvelde, Greet
2014-01-01
To mitigate climate destabilisation, human-induced greenhouse gas emissions urgently need to be curbed. A major share of these emissions originates from the industry and energy sectors. Hence, a low carbon shift in industrial and business park energy systems is called for. Low carbon business parks minimise energy-related carbon dioxide emissions by maximal exploitation of local renewable energy production, enhanced energy efficiency, and inter-firm heat exchange, combined in a collective energy system. The holistic approach of techno-economic energy models facilitates the design of such systems, while yielding an optimal trade-off between energetic, economic and environmental performances. However, no models custom-tailored for industrial park energy systems are detected in literature. In this paper, existing energy model classifications are scanned for adequate model characteristics and accordingly, a confined number of models are selected and described. Subsequently, a practical typology is proposed, existing of energy system evolution, optimisation, simulation, accounting and integration models, and key model features are compared. Finally, important features for a business park energy model are identified. - Highlights: • A holistic perspective on (low carbon) business park energy systems is introduced. • A new categorisation of techno-economic energy models is proposed. • Model characteristics are described per model category. • Essential model features for business park energy system modelling are identified. • A strategy towards a techno-economic energy model for business parks is proposed
XY model with higher-order exchange.
Žukovič, Milan; Kalagov, Georgii
2017-08-01
An XY model, generalized by inclusion of up to an infinite number of higher-order pairwise interactions with an exponentially decreasing strength, is studied by spin-wave theory and Monte Carlo simulations. At low temperatures the model displays a quasi-long-range-order phase characterized by an algebraically decaying correlation function with the exponent η=T/[2πJ(p,α)], nonlinearly dependent on the parameters p and α that control the number of the higher-order terms and the decay rate of their intensity, respectively. At higher temperatures the system shows a crossover from the continuous Berezinskii-Kosterlitz-Thouless to the first-order transition for the parameter values corresponding to a highly nonlinear shape of the potential well. The role of topological excitations (vortices) in changing the nature of the transition is discussed.
Quasielastic scattering charge exchange p3He→nFppp reaction at mean energies
International Nuclear Information System (INIS)
Blinov, A.V.; Vanyushin, I.A.; Grechko, V.E.
1988-01-01
The main characteristics of the quasi-elastic charge-exchange reaction p 3 He → n F ppp (where n F is fast neutron in the rest frame of 3 He nucleus) are studied making use of the ITEP 80-cm liquid-hydrogen bubble chamber exposed in the 3 He beams of 2.5 and 5 GeV/c momenta (the kinetic energy T p of the primary protons in the rest frame of the nucleus is, respectively, 0.318 and 0.978 GeV). The experimental data are compared with the Galuber - Sitenko multiple scattering theory predictions and with the pole-model calculations taking into account the final-state interaction of the spectator nucleons. In the mass spectrum of the 3p system at 3.05 GeV a prominent structure has been observed which cannot be described by the pole model. Possible resonance nature of this structure is discussed
A relativistic, meson exchange model of pion-nucleon scattering
International Nuclear Information System (INIS)
Pearces, B.C.; Jennings, B.K.
1990-06-01
A relativistic meson exchange approach to the pion-nucleon interaction is developed using a three-dimensional relativistic two-body propagator, and the results using different propagators are compared. The relativistic approach is able to describe low energy scattering up to 400 MeV above threshold, while preserving the soft pion theorems. The different propagators give similar results, as the form factors necessary to get a fit suppress much of the multiple scattering. (Author) (24 refs., 4 tabs., 6 figs.)
Advanced Heat/Mass Exchanger Technology for Geothermal and Solar Renewable Energy Systems
Energy Technology Data Exchange (ETDEWEB)
Greiner, Miles [Univ. of Nevada, Reno, NV (United States); Childress, Amy [Univ. of Nevada, Reno, NV (United States); Hiibel, Sage [Univ. of Nevada, Reno, NV (United States); Kim, Kwang [Univ. of Nevada, Reno, NV (United States); Park, Chanwoo [Univ. of Nevada, Reno, NV (United States); Wirtz, Richard [Univ. of Nevada, Reno, NV (United States)
2014-12-16
Northern Nevada has abundant geothermal and solar energy resources, and these renewable energy sources provide an ample opportunity to produce economically viable power. Heat/mass exchangers are essential components to any energy conversion system. Improvements in the heat/mass exchange process will lead to smaller, less costly (more efficient) systems. There is an emerging heat transfer technology, based on micro/nano/molecular-scale surface science that can be applied to heat/mass exchanger design. The objective is to develop and characterize unique coating materials, surface configurations and membranes capable of accommodating a 10-fold increase in heat/mass exchanger performance via phase change processes (boiling, condensation, etc.) and single phase convective heat/mass transfer.
Scattering in Soliton Models and the Bosonic Exchange description
Coriano', Claudio; Parwani, Rajesh R.; Yamagishi, Hidenaga; Zahed, Ismail
1992-01-01
We argue that the description of meson-nucleon dynamics based on the boson-exchange approach, is compatible with the description of the nucleon as a soliton in the nonrelativistic limit. Our arguments are based on an analysis of the meson-soliton form factor and the exact meson-soliton and soliton-soliton scattering amplitudes in the Sine-Gordon model.
Critique of a pion exchange model for interquark forces
International Nuclear Information System (INIS)
Isgur, N.
1999-01-01
The author describes four serious defects of a widely discuss pion exchange model for interquark forces: it doesn't solve the ''spin-orbit problem'' as advertised, it fails to describe the internal structure of baryon resonances, it leads to disastrous conclusions when extended to mesons, and it is not reasonably connected to the physics of heavy-light systems
Modelling of natural-convection driven heat exchangers
Dirkse, M.H.; Loon, van W.K.P.; Stigter, J.D.; Bot, G.P.A.
2007-01-01
Abstract: A lumped model is developed for shell-and-tube heat exchangers driven by natural convection, which is based on a one-dimensional approximation. The heat flux is driven by the logarithmic mean temperature difference. The volumetric air flow rate is driven by the buoyant force. Based on the
Simplified modeling of liquid-liquid heat exchangers for use in control systems
International Nuclear Information System (INIS)
Laszczyk, Piotr
2017-01-01
For last decades various models of heat exchange processes have been developed to capture their specific dynamic nature. These models have different degrees of complexity depending on modeling assumptions and simplifications. Complexity of mathematical model can be very critical when the model is to be a basis for deriving the control law because it directly affects the complexity of mathematical transformations and complexity of final control algorithm. In this paper, the simplified cross convection model for wide class of heat exchangers is suggested. Apart from very few reports so far, the properties of this modeling approach have never been investigated in detail. The concept for this model is derived from the fundamental principle of energy conservation and combined with a simple dynamical approximation in the form of ordinary differential equations. Within this framework, the simplified tuning procedure of the proposed model is suggested and verified for plate and spiral tube heat exchangers based on experimental data. The dynamical properties and stability of the suggested model are addressed and sensitivity analysis is also presented. It is shown that such a modeling approach preserves high modeling accuracy at very low numerical complexity. The validation results show that the suggested modeling and tuning method is useful for practical applications.
Numerical Simulation of Different Models of Heat Pipe Heat Exchanger Using AcuSolve
Directory of Open Access Journals (Sweden)
Zainal Nurul Amira
2017-01-01
Full Text Available In this paper, a numerical simulation of heat pipe heat exchanger (HPHE is computed by using CFD solver program i.e. AcuSolve. Two idealized model of HPHE are created with different variant of entry’s dimension set to be case 1 and case 2. The geometry of HPHE is designed in SolidWorks and imported to AcuSolve to simulate the fluid flow numerically. The design of HPHE is the key to provide a heat exchanger system to work proficient as expected. Finally, the result is used to optimize and improving heat recovery systems of the increasing demand for energy efficiency in industry.
International Nuclear Information System (INIS)
Park, Jae Sung; Jacobi, Anthony M.
2009-01-01
A significant portion of the energy consumed by many home appliances using hot water is used to heat cold supply water. Such home appliances generally are supplied water at a temperature lower than the ambient temperature, and the supply water is normally heated to its maximum operating temperature, often using natural gas or an electrical heater. In some cases, it is possible to pre-heat the supply water and save energy that would normally be consumed by the natural gas or electrical heater. In order to save the energy consumed by an appliance using water heater, a run-around heat exchanger system is used to transfer heat from the ambient to the water before an electrical heater is energized. A simple model to predict the performance of this system is developed and validated, and the model is used to explore design and operating issues relevant to the run-around heat exchanger system. Despite the additional power consumption by the fan and pump of the run-around heat exchanger system, the experimental data and analysis show that for some systems the overall energy efficiency of the appliance can be improved, saving about 6% of the energy used by the baseline machine.
Italian energy scenarios: Markal model
International Nuclear Information System (INIS)
Gracceva, Francesco
2005-01-01
Energy scenarios carried out through formal models comply with scientific criteria such as internal coherence and transparency. Besides, Markal methodology allows a good understanding of the complex nature of the energy system. The business-as-usual scenario carried out through the Markal-Italy model shows that structural changes occurring in end-use sectors will continue to drive up energy consumption, in spite of the slow economic growth and the quite high energy prices [it
Modeling and predicting historical volatility in exchange rate markets
Lahmiri, Salim
2017-04-01
Volatility modeling and forecasting of currency exchange rate is an important task in several business risk management tasks; including treasury risk management, derivatives pricing, and portfolio risk evaluation. The purpose of this study is to present a simple and effective approach for predicting historical volatility of currency exchange rate. The approach is based on a limited set of technical indicators as inputs to the artificial neural networks (ANN). To show the effectiveness of the proposed approach, it was applied to forecast US/Canada and US/Euro exchange rates volatilities. The forecasting results show that our simple approach outperformed the conventional GARCH and EGARCH with different distribution assumptions, and also the hybrid GARCH and EGARCH with ANN in terms of mean absolute error, mean of squared errors, and Theil's inequality coefficient. Because of the simplicity and effectiveness of the approach, it is promising for US currency volatility prediction tasks.
Energy-exchange collisions of dark-bright-bright vector solitons.
Radhakrishnan, R; Manikandan, N; Aravinthan, K
2015-12-01
We find a dark component guiding the practically interesting bright-bright vector one-soliton to two different parametric domains giving rise to different physical situations by constructing a more general form of three-component dark-bright-bright mixed vector one-soliton solution of the generalized Manakov model with nine free real parameters. Moreover our main investigation of the collision dynamics of such mixed vector solitons by constructing the multisoliton solution of the generalized Manakov model with the help of Hirota technique reveals that the dark-bright-bright vector two-soliton supports energy-exchange collision dynamics. In particular the dark component preserves its initial form and the energy-exchange collision property of the bright-bright vector two-soliton solution of the Manakov model during collision. In addition the interactions between bound state dark-bright-bright vector solitons reveal oscillations in their amplitudes. A similar kind of breathing effect was also experimentally observed in the Bose-Einstein condensates. Some possible ways are theoretically suggested not only to control this breathing effect but also to manage the beating, bouncing, jumping, and attraction effects in the collision dynamics of dark-bright-bright vector solitons. The role of multiple free parameters in our solution is examined to define polarization vector, envelope speed, envelope width, envelope amplitude, grayness, and complex modulation of our solution. It is interesting to note that the polarization vector of our mixed vector one-soliton evolves in sphere or hyperboloid depending upon the initial parametric choices.
International Nuclear Information System (INIS)
Voss, A.
1976-01-01
The development and application of energy models as helping factors in planning and decision making has gained more importance in all regions of energy economy and energy policy in recent times. This development not only covered models for the single branches and companies like, for example, for improving power plant systems, but also models showing the whole energy system. These models aim at analizing the possibilities of developing the energy supply with regard to aspects of the entire system, paying special attention to the integration of the energy system into economic and ecological side conditions. The following essay briefly explains the energy models developed for the Federal Republic of Germany after analizing the set of problems of energy and the demands on the energy planning methods arising from them. The energy model system developed by the programming team 'Systems research and technological development' of the nuclear research plant in Juelich is dealt with very intensively, explaining some model results as examples. Finally, the author gives his opinion on the problem of the integration and conversion of model studies in the process of decision making. (orig.) [de
A Dealer Model of Foreign Exchange Market with Finite Assets
Hamano, Tomoya; Kanazawa, Kiyoshi; Takayasu, Hideki; Takayasu, Misako
An agent-based model is introduced to study the finite-asset effect in foreign exchange markets. We find that the transacted price asymptotically approaches an equilibrium price, which is determined by the monetary balance between the pair of currencies. We phenomenologically derive a formula to estimate the equilibrium price, and we model its relaxation dynamics around the equilibrium price on the basis of a Langevin-like equation.
Inventory of state energy models
Energy Technology Data Exchange (ETDEWEB)
Melcher, A.G.; Gist, R.L.; Underwood, R.G.; Weber, J.C.
1980-03-31
These models address a variety of purposes, such as supply or demand of energy or of certain types of energy, emergency management of energy, conservation in end uses of energy, and economic factors. Fifty-one models are briefly described as to: purpose; energy system; applications;status; validation; outputs by sector, energy type, economic and physical units, geographic area, and time frame; structure and modeling techniques; submodels; working assumptions; inputs; data sources; related models; costs; references; and contacts. Discussions in the report include: project purposes and methods of research, state energy modeling in general, model types and terminology, and Federal legislation to which state modeling is relevant. Also, a state-by-state listing of modeling efforts is provided and other model inventories are identified. The report includes a brief encylopedia of terms used in energy models. It is assumed that many readers of the report will not be experienced in the technical aspects of modeling. The project was accomplished by telephone conversations and document review by a team from the Colorado School of Mines Research Institute and the faculty of the Colorado School of Mines. A Technical Committee (listed in the report) provided advice during the course of the project.
Home Performance with ENERGY STAR(R) Exchange
Energy Technology Data Exchange (ETDEWEB)
2003-10-01
Handout for the Energy and Environmental Building Association's Building Solutions 2003 Conference and Expo: Chicago, Illinois, October 2003 The following summaries, provided by implementers of ''Home Performance with ENERGY STAR{reg_sign}'' around the country, are for use in the October 15 discussion during the Energy & Environmental Building Association (EEBA) Building Solutions, 2003 Conference in Chicago. The summaries and session discussions provide an overview of ''Home Performance with ENERGY STAR'', along with results and lessons learned from existing ''Home Performance'' implementers in New York, Wisconsin, Massachusetts, California, and Kansas City. Five future pilot projects set to begin in Georgia/Alabama, Idaho, Missouri, New Jersey and Texas will also be presented and discussed. Session topics will include the use of different training approaches, methods of quality assurance, and the role contractor certification plays in several of the programs. The session will conclude with a roundtable discussion of Home Performance issues by current and emerging implementers, with time for participant questions. ''Home Performance with ENERGY STAR'' uses the growing awareness and credibility of the ENERGY STAR brand to encourage and facilitate whole-house energy improvements in existing homes through self-sustaining energy efficiency programs. Whether you're a state energy official, utility program manager, contractor training professional or efficiency program implementer, you're sure to benefit from the unique presentations and networking opportunities that this session will offer.
Two-phase plate-fin heat exchanger modeling for waste heat recovery systems in diesel engines
Feru, E.; de Jager, B.; Willems, F.; Steinbuch, M.
2014-01-01
This paper presents the modeling and model validation for a modular two-phase heat exchanger that recovers energy in heavy-duty diesel engines. The model is developed for temperature and vapor quality prediction and for control design of the waste heat recovery system. In the studied waste heat
Alimov, V. K.; Tyburska-Puschel, B.; Hoen, Mhjt; Roth, J.; Hatano, Y.; Isobe, K.; Matsuyama, M.; Yamanishi, T.
2011-01-01
Hydrogen isotope exchange in tungsten was investigated at various temperatures both after sequential exposure to low-energy deuterium (D) and protium (H) plasmas and after sequential irradiation with low-energy D and H ions. The methods used were thermal desorption spectroscopy, and the D((3)He,
Pion production in proton-proton collisions in a covariant one boson exchange model
International Nuclear Information System (INIS)
Shyam, R.
1997-01-01
We investigate the pion production in proton-proton collisions over an energy range of 300 MeV to 2 GeV. Starting from a realistic one-boson exchange model with parameters fitted to the amplitudes of the elastic nucleon-nucleon scattering, we perform fully covariant calculations for the total, double and triple differential cross sections of the p(p,nπ + )p and p(p,pπ 0 )p reactions. The calculations incorporate the exchange of π, ρ, ω and σ mesons and treat nucleon and delta isobar as intermediate states. We obtain a reasonably good agreement with the experimental data in the entire range of beam energies. The form of the covariant delta propagator, the cut-off parameter for the πN N and πN Δ vertex form factors and the energy dependence of the delta isobar decay width is investigated. (author)
ECONOMETRIC APPROACH TO DIFFERENCE EQUATIONS MODELING OF EXCHANGE RATES CHANGES
Directory of Open Access Journals (Sweden)
Josip Arnerić
2010-12-01
Full Text Available Time series models that are commonly used in econometric modeling are autoregressive stochastic linear models (AR and models of moving averages (MA. Mentioned models by their structure are actually stochastic difference equations. Therefore, the objective of this paper is to estimate difference equations containing stochastic (random component. Estimated models of time series will be used to forecast observed data in the future. Namely, solutions of difference equations are closely related to conditions of stationary time series models. Based on the fact that volatility is time varying in high frequency data and that periods of high volatility tend to cluster, the most successful and popular models in modeling time varying volatility are GARCH type models and their variants. However, GARCH models will not be analyzed because the purpose of this research is to predict the value of the exchange rate in the levels within conditional mean equation and to determine whether the observed variable has a stable or explosive time path. Based on the estimated difference equation it will be examined whether Croatia is implementing a stable policy of exchange rates.
Charge exchange processes of high energy heavy ions channeled in crystals
International Nuclear Information System (INIS)
Andriamonje, S.; Dural, J.; Toulemonde, M.; Groeneveld, K.O.; Maier, R.; Quere, Y.
1990-01-01
The interaction of moving ions with single crystals is very sensitive to the orientation of the incident beam with respect to the crystalline directions of the target. The experiments show that high energy heavy ion channeling deeply modifies the slowing down and charge exchange processes. In this review, we describe the opportunity offered by channeling conditions to study the charge exchange processes. Some aspects of the charge exchange processes with high energy channeled heavy ions are selected from the extensive literature published over the past few years on this subject. Special attention is given to the work performed at the GANIL facility on the study of Radiative Electron Capture (REG), Electron Impact Ionisation (EII), and convoy electron emission. Finally we emphasize the interest of studying resonant charge exchange processes such as Resonant Coherent Excitation (RCE), Resonant Transfer and Excitation (RTE) or Dielectronic Recombination (DR) and the recently proposed Nuclear Excitation by Electron Capture (NEEC)
Directory of Open Access Journals (Sweden)
Haritonova Larisa
2017-01-01
Full Text Available The article gives the analytical generalization of the data on the energy efficiency for heat exchangers with the flat heat exchange surface to which systems of impact plane parallel jets are sent. Functional relations of specific power consumption (per unit of area, which were obtained for the first time using the techniques of the similarity law, for moving a heat carrier are shown with regard to design and operation factors. The regression equations representing a mathematical model of the process enable to carry out an analysis of various factors impact on the parameter to be determined. The obtained results can be used to optimize or to create the calculation techniques for new highly-efficient heat exchange devices with jet plane -parallel impingement systems and also to reduce power consumption for moving a heat carrier.
Energy modelling in sensor networks
Directory of Open Access Journals (Sweden)
D. Schmidt
2007-06-01
Full Text Available Wireless sensor networks are one of the key enabling technologies for the vision of ambient intelligence. Energy resources for sensor nodes are very scarce. A key challenge is the design of energy efficient communication protocols. Models of the energy consumption are needed to accurately simulate the efficiency of a protocol or application design, and can also be used for automatic energy optimizations in a model driven design process. We propose a novel methodology to create models for sensor nodes based on few simple measurements. In a case study the methodology was used to create models for MICAz nodes. The models were integrated in a simulation environment as well as in a SDL runtime framework of a model driven design process. Measurements on a test application that was created automatically from an SDL specification showed an 80% reduction in energy consumption compared to an implementation without power saving strategies.
Directory of Open Access Journals (Sweden)
Debeljković Dragutin Lj.
2016-01-01
Full Text Available The heat exchangers are frequently used as constructive elements in various plants and their dynamics is very important. Their operation is usually controlled by manipulating inlet fluid temperatures or mass flow rates. On the basis of the accepted and critically clarified assumptions, a linearized mathematical model of the cross-flow heat exchanger has been derived, taking into account the wall dynamics. The model is based on the fundamental law of energy conservation, covers all heat accumulation storages in the process, and leads to the set of partial differential equations (PDE, which solution is not possible in closed form. In order to overcome this problem the approach based on physical discretization was applied with associated time delay on the positions where it was necessary and unavoidable. This is quite new approach, which represent the further extension of previous results which did not include significant time delay existing in the working media. Simulation results, were derived, showing progress in building such a model suitable for further treatment from the position of analysis as well as the needs for control synthesis problem.
Local description of the energy transfer process in a packed bed heat exchanger
International Nuclear Information System (INIS)
Costa, M.L.M.; Sampaio, R.; Gama, R.M.S. da.
1990-01-01
The energy transfer process in a packed-bed heat exchanger, in counter0flow arrangement is considered. The phenomenon is described through a Continuum Theory of Mixtures approach, in which fluid and solid (porous matrix) are regarded as continuous constituents possessing, each one, its own temperature and velocity fields. The heat 'exchangers consists of two channels, separated by an impermeable wall without thermal resistence, in which there exists a saturated flow. Some particular cases are simulated. (author)
DRIFT ANALYSIS ON NEURAL NETWORK MODEL OF HEAT EXCHANGER FOULING
Directory of Open Access Journals (Sweden)
M. RAMASAMY
2008-04-01
Full Text Available Neural Networks (NN provide a good platform for modeling complex and poorly understood systems in many different fields. Due to the empirical nature of NN, it is typically valid only for small operating windows. As the process drifts, the prediction accuracy of such models deteriorates very much rendering the models unfit. An on-line mechanism to follow the drift in the process is necessary in order to retrain the NN models. Information Criteria have been reported to be used for the selection of relevant input variables and determination of optimal NN model structures. This paper proposes the use of information criteria for tracking the model prediction accuracy and provides an algorithm for retraining the model. A heat exchanger in a refinery Crude Preheat Train (CPT has been used as a case study. The operational problems of heat exchangers in CPT are compounded by the varying nature of crude blends and the complex fouling phenomenon. Fouling develops slowly and therefore the drift in the process occurs on a slower scale. The performance of a NN fouling model, developed using industrial data is investigated for drift. Model performance at different operating conditions is evaluated and it has been shown that drifts do occur in the process. An algorithm for retraining NN model has been proposed.
International Nuclear Information System (INIS)
Gadalla, Mamdouh A.
2015-01-01
Energy integration is a key solution in chemical process and crude refining industries to minimise external fuel consumption and to face the impact of growing energy crises. Typical energy integration projects can reach a reduction of heating fuels and cold utilities by up to 40% compared with original designs or existing installations. Pinch Analysis is a leading tool and regarded as an efficient method to increase energy efficiency and minimise fuel flow consumptions. It is valid for both natures of design, grassroots and retrofit situations. It can practically be applied to synthesise a HEN (heat exchanger network) or modify an existing preheat train for minimum energy consumption. Heat recovery systems or HENs are networks for exchanging heat between hot and cold process sources. All heat transferred from hot process sources into cold process sinks represent the scope for energy integration. On the other hand, energies required beyond this integrated amount are to be satisfied by external utilities. Graphical representations of Pinch Analysis, such as Composite and Grand Composite Curves are very useful for grassroots designs. Nevertheless, in retrofit situation the analysis is not adequate and besides it is graphically tedious to represent existing exchangers on such graphs. This research proposes a new graphical method for the analysis of heat recovery systems, applicable to HEN retrofit. The new graphical method is based on plotting temperatures of process hot streams versus temperatures of process cold streams. A new graph is constructed for representing existing HENs. For a given network, each existing exchanger is represented by a straight line, whose slope is proportional to the ratio of heat capacities and flows. Further, the length of each exchanger line is related to the heat flow transferred across this exchanger. This new graphical representation can easily identify exchangers across the pinch, Network Pinch, pinching matches and improper placement
A new modelling approach for piled and other ground heat exchanger applications
Cecinato, F; Loveridge, F; Gajo, A; Powrie, W
2015-01-01
Pile heat exchangers have an increasing role to play in the delivery of renewable heating and cooling energy. Traditionally the thermal design of ground heat exchangers has relied upon analytical approaches which take a relatively simple approach to the inside of the heat exchanger. This approach is justified while the heat exchanger diameter remains small. However, as larger diameter piled founda-tions are used as heat exchangers, the transient heat transfer processes operating within the pi...
Agriculture energy 2030. Report seminar. Summary of talks and exchanges
International Nuclear Information System (INIS)
2011-01-01
Energy in agriculture is a major issue for its economic consequences for farms, for its relationships with environmental and climate issues, and for its influence on sector organisation and land planning. This seminar, through discussions on the relationships between energy, agriculture and territories and on the challenges for public action and research, proposes and discusses a comprehensive diagnosis of present challenges, as well as four scenarios by 2030. These scenarios are defined with respect to three evolution drivers: town-country mobility, economic dynamics, and natural resources
Blockchain for Smart Grid Resilience: Exchanging Distributed Energy at Speed, Scale and Security
Energy Technology Data Exchange (ETDEWEB)
Mylrea, Michael E.; Gourisetti, Sri Nikhil Gup
2017-09-18
Blockchain may help solve several complex problems related to integrity and trustworthiness of rapid, distributed, complex energy transactions and data exchanges. In a move towards resilience, blockchain commoditizes trust and enables automated smart contracts to support auditable multiparty transactions based on predefined rules between distributed energy providers and customers. Blockchain based smart contracts also help remove the need to interact with third-parties, facilitating the adoption and monetization of distributed energy transactions and exchanges, both energy flows as well as financial transactions. This may help reduce transactive energy costs and increase the security and sustainability of distributed energy resource (DER) integration, helping to remove barriers to a more decentralized and resilient power grid.
Modeling Of Proton Exchange Membrane Fuel Cell Systems
DEFF Research Database (Denmark)
Nielsen, Mads Pagh
The objective of this doctoral thesis was to develop reliable steady-state and transient component models suitable to asses-, develop- and optimize proton exchange membrane (PEM) fuel cell systems. Several components in PEM fuel cell systems were characterized and modeled. The developed component......- and system models match experimental data from the literature. However, limited data were available for verification so further work is necessary to confirm detailed aspects of the models. It is nonetheless expected that the developed models will be useful for system modeling and optimization of PEM fuel...... cell systems. Consequences of indirectly fueling PEM stacks with hydrocarbons using reforming technology were investigated using a PEM stack model including CO poisoning kinetics and a transient Simulink steam reforming system model. Aspects regarding the optimization of PEM fuel cell systems...
Energy and CO $ _2 $; exchanges and influencing factors in spring ...
Indian Academy of Sciences (India)
Spring wheat (Triticum aestivum Linn.) is an important crop for food security in the desert-oasis farmland in the middle reaches of the Heihe River in northwestern China. We measured fluxes using eddy covarianceand meteorological parameters to explore the energy fluxes and the relationship between CO² flux and climate ...
Modeling the exchange rate using price levels and country risk
Directory of Open Access Journals (Sweden)
Gábor Regős
2015-12-01
Full Text Available This paper builds two factor discrete time models in order to investigate the effect of sovereign risk on the nominal exchange rates in a Markov switching framework. The empirical section of the paper uses seven currencies from Chile, the Czech Republic, Hungary, Iceland, Japan, Korea, and Mexico. To measure the sovereign risk, we use the credit rating agencies’ ratings classes as proxy variable. In the empirical part, four different versions of the model are calibrated and their in-sample and out-of-sample data will be analyzed leading to the conclusion that none of the four versions dominates the others. As an additional result, it is revealed that risk has significant effect on the nominal exchange rates.
ENERGY BALANCE AND CO2 EXCHANGE BEHAVIOUR IN SUB-TROPICAL YOUNG PINE (Pinus roxburghii PLANTATION
Directory of Open Access Journals (Sweden)
B. K. Bhattacharya
2012-08-01
Full Text Available A study was conducted to understand the seasonal and annual energy balance behaviour of young and growing sub-tropical chir pine (Pinus roxburghii plantation of eight years age in the Doon valley, India and its coupling with CO2 exchange. The seasonal cycle of dekadal daytime latent heat fluxes mostly followed net radiation cycle with two minima and range between 50–200 Wm-2 but differed from the latter during the period when soil wetness and cloudiness were not coupled. Dekadal evaporative fraction closely followed the seasonal dryness-wetness cycle thus minimizing the effect of wind on energy partitioning as compared to diurnal variation. Daytime latent heat fluxes were found to have linear relationship with canopy net assimilation rate (Y = 0.023X + 0.171, R2 = 0.80 though nonlinearity exists between canopy latent heat flux and hourly net CO2 assimilation rate . Night-time plant respiration was found to have linear relationship (Y = 0.088 + 1.736, R2 = 0.72 with night-time average vapour pressure deficit (VPD. Daily average soil respiration was found to be non-linearly correlated to average soil temperatures (Y = -0.034X2 + 1.676X – 5.382, R2 = 0.63 The coupled use of empirical models, seasonal energy fluxes and associated parameters would be useful to annual water and carbon accounting in subtropical pine ecosystem of India in the absence high-response eddy covariance tower.
Stochastic Modelling of Energy Systems
DEFF Research Database (Denmark)
Andersen, Klaus Kaae
2001-01-01
In this thesis dynamic models of typical components in Danish heating systems are considered. Emphasis is made on describing and evaluating mathematical methods for identification of such models, and on presentation of component models for practical applications. The thesis consists of seven...... of component models, such as e.g. heat exchanger and valve models, adequate for system simulations. Furthermore, the thesis demonstrates and discusses the advantages and disadvantages of using statistical methods in conjunction with physical knowledge in establishing adequate component models of heating...... research papers (case studies) together with a summary report. Each case study takes it's starting point in typical heating system components and both, the applied mathematical modelling methods and the application aspects, are considered. The summary report gives an introduction to the scope...
A threshold model for Australian Stock Exchange equities
Bertram, William K.
2005-02-01
In this paper, we present a threshold model to describe the phenomena of zero return enhancement that is present in Australian Stock Exchange data. We examine the intraday behaviour of the ASX data and construct a new measure for the market activity using principal component analysis. We use this measure to create a business time scale that keeps the level of zero return enhancement constant throughout trading hours. Operating in this new time scale we fit the model to data for small and large time scales and find that the model affords an excellent approximation of the distribution of stock returns.
Numerical modeling transport phenomena in proton exchange membrane fuel cells
Suh, DongMyung
To study the coupled phenomena occurring in proton exchange membrane fuel cells, a two-phase, one-dimensional, non-isothermal model is developed in the chapter 1. The model includes water phase change, proton transport in the membrane and electro-osmotic effect. The thinnest, but most complex layer in the membrane electrode assembly, catalyst layer, is considered an interfacial boundary between the gas diffusion layer and the membrane. Mass and heat transfer and electro-chemical reaction through the catalyst layer are formulated into equations, which are applied to boundary conditions for the gas diffusion layer and the membrane. Detail accounts of the boundary equations and the numerical solving procedure used in this work are given. The polarization curve is calculated at different oxygen pressures and compared with the experimental results. When the operating condition is changed along the polarization curve, the change of physicochemical variables in the membrane electrode assembly is studied. In particular, the over-potential diagram presents the usage of the electrochemical energy at each layer of the membrane electrode assembly. Humidity in supplying gases is one of the most important factors to consider for improving the performance of PEMFE. Both high and low humidity conditions can result in a deteriorating cell performance. The effect of humidity on the cell performance is studied in the chapter 2. First, a numerical model based on computational fluid dynamics is developed. Second, the cell performances are simulated, when the relative humidity is changed from 0% to 100% in the anode and the cathode channel. The simulation results show how humidity in the reactant gases affects the water content distribution in the membrane, the over-potential at the catalyst layers and eventually the cell performance. In particular, the rapid enhancement in the cell performance caused by self-hydrating membrane is captured by the simulation. Fully humidifying either H2
Exchange bias of patterned systems: Model and numerical simulation
International Nuclear Information System (INIS)
Garcia, Griselda; Kiwi, Miguel; Mejia-Lopez, Jose; Ramirez, Ricardo
2010-01-01
The magnitude of the exchange bias field of patterned systems exhibits a notable increase in relation to the usual bilayer systems, where a continuous ferromagnetic film is deposited on an antiferromagnet insulator. Here we develop a model, and implement a Monte Carlo calculation, to interpret the experimental observations which is consistent with experimental results, on the basis of assuming a small fraction of spins pinned ferromagnetically in the antiferromagnetic interface layer.
Mussard, Bastien; Rocca, Dario; Jansen, Georg; Ángyán, János G
2016-05-10
Starting from the general expression for the ground state correlation energy in the adiabatic-connection fluctuation-dissipation theorem (ACFDT) framework, it is shown that the dielectric matrix formulation, which is usually applied to calculate the direct random phase approximation (dRPA) correlation energy, can be used for alternative RPA expressions including exchange effects. Within this famework, the ACFDT analog of the second order screened exchange (SOSEX) approximation leads to a logarithmic formula for the correlation energy similar to the direct RPA expression. Alternatively, the contribution of the exchange can be included in the kernel used to evaluate the response functions. In this case, the use of an approximate kernel is crucial to simplify the formalism and to obtain a correlation energy in logarithmic form. Technical details of the implementation of these methods are discussed, and it is shown that one can take advantage of density fitting or Cholesky decomposition techniques to improve the computational efficiency; a discussion on the numerical quadrature made on the frequency variable is also provided. A series of test calculations on atomic correlation energies and molecular reaction energies shows that exchange effects are instrumental for improvement over direct RPA results.
Towards improved local hybrid functionals by calibration of exchange-energy densities
International Nuclear Information System (INIS)
Arbuznikov, Alexei V.; Kaupp, Martin
2014-01-01
A new approach for the calibration of (semi-)local and exact exchange-energy densities in the context of local hybrid functionals is reported. The calibration functions are derived from only the electron density and its spatial derivatives, avoiding spatial derivatives of the exact-exchange energy density or other computationally unfavorable contributions. The calibration functions fulfill the seven more important out of nine known exact constraints. It is shown that calibration improves substantially the definition of a non-dynamical correlation energy term for generalized gradient approximation (GGA)-based local hybrids. Moreover, gauge artifacts in the potential-energy curves of noble-gas dimers may be corrected by calibration. The developed calibration functions are then evaluated for a large range of energy-related properties (atomization energies, reaction barriers, ionization potentials, electron affinities, and total atomic energies) of three sets of local hybrids, using a simple one-parameter local-mixing. The functionals are based on (a) local spin-density approximation (LSDA) or (b) Perdew-Burke-Ernzerhof (PBE) exchange and correlation, and on (c) Becke-88 (B88) exchange and Lee-Yang-Parr (LYP) correlation. While the uncalibrated GGA-based functionals usually provide very poor thermochemical data, calibration allows a dramatic improvement, accompanied by only a small deterioration of reaction barriers. In particular, an optimized BLYP-based local-hybrid functional has been found that is a substantial improvement over the underlying global hybrids, as well as over previously reported LSDA-based local hybrids. It is expected that the present calibration approach will pave the way towards new generations of more accurate hyper-GGA functionals based on a local mixing of exchange-energy densities
Heat pipe heat exchanger and its potential to energy recovery in the tropics
Directory of Open Access Journals (Sweden)
Yau Yat H.
2015-01-01
Full Text Available The heat recovery by the heat pipe heat exchangers was studied in the tropics. Heat pipe heat exchangers with two, four, six, and eight numbers of rows were examined for this purpose. The coil face velocity was set at 2 m/s and the temperature of return air was kept at 24°C in this study. The performance of the heat pipe heat exchangers was recorded during the one week of operation (168 hours to examine the performance data. Then, the collected data from the one week of operation were used to estimate the amount of energy recovered by the heat pipe heat exchangers annually. The effect of the inside design temperature and the coil face velocity on the energy recovery for a typical heat pipe heat exchanger was also investigated. In addition, heat pipe heat exchangers were simulated based on the effectiveness-NTU method, and their theoretical values for the thermal performance were compared with the experimental results.
Energy Technology Data Exchange (ETDEWEB)
Hughes, Patrick [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Im, Piljae [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
2012-01-01
(FHX) has been coined to refer exclusively to ground heat exchangers installed in the overcut around the basement walls. The primary technical challenge undertaken by this project was the development and validation of energy performance models and design tools for FHX. In terms of performance modeling and design, ground heat exchangers in other construction excavations (e.g., utility trenches) are no different from conventional HGHX, and models and design tools for HGHX already exist. This project successfully developed and validated energy performance models and design tools so that FHX or hybrid FHX/HGHX systems can be engineered with confidence, enabling this technology to be applied in residential and light commercial buildings. The validated energy performance model also addresses and solves another problem, the longstanding inadequacy in the way ground-building thermal interaction is represented in building energy models, whether or not there is a ground heat exchanger nearby. Two side-by-side, three-level, unoccupied research houses with walkout basements, identical 3,700 ft{sup 2} floor plans, and hybrid FHX/HGHX systems were constructed to provide validation data sets for the energy performance model and design tool. The envelopes of both houses are very energy efficient and airtight, and the HERS ratings of the homes are 44 and 45 respectively. Both houses are mechanically ventilated with energy recovery ventilators, with space conditioning provided by water-to-air heat pumps with 2 ton nominal capacities. Separate water-to-water heat pumps with 1.5 ton nominal capacities were used for water heating. In these unoccupied research houses, human impact on energy use (hot water draw, etc.) is simulated to match the national average. At House 1 the hybrid FHX/HGHX system was installed in 300 linear feet of excavation, and 60% of that was construction excavation (needed to construct the home). At House 2 the hybrid FHX/HGHX system was installed in 360 feet of
Energy Technology Data Exchange (ETDEWEB)
Hughes, Patrick [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Im, Piljae [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2012-04-01
(FHX) has been coined to refer exclusively to ground heat exchangers installed in the overcut around the basement walls. The primary technical challenge undertaken by this project was the development and validation of energy performance models and design tools for FHX. In terms of performance modeling and design, ground heat exchangers in other construction excavations (e.g., utility trenches) are no different from conventional HGHX, and models and design tools for HGHX already exist. This project successfully developed and validated energy performance models and design tools so that FHX or hybrid FHX/HGHX systems can be engineered with confidence, enabling this technology to be applied in residential and light commercial buildings. The validated energy performance model also addresses and solves another problem, the longstanding inadequacy in the way ground-building thermal interaction is represented in building energy models, whether or not there is a ground heat exchanger nearby. Two side-by-side, three-level, unoccupied research houses with walkout basements, identical 3,700 ft{sup 2} floor plans, and hybrid FHX/HGHX systems were constructed to provide validation data sets for the energy performance model and design tool. The envelopes of both houses are very energy efficient and airtight, and the HERS ratings of the homes are 44 and 45 respectively. Both houses are mechanically ventilated with energy recovery ventilators, with space conditioning provided by water-to-air heat pumps with 2 ton nominal capacities. Separate water-to-water heat pumps with 1.5 ton nominal capacities were used for water heating. In these unoccupied research houses, human impact on energy use (hot water draw, etc.) is simulated to match the national average. At House 1 the hybrid FHX/HGHX system was installed in 300 linear feet of excavation, and 60% of that was construction excavation (needed to construct the home). At House 2 the hybrid FHX/HGHX system was installed in 360 feet of
Wealth distribution of simple exchange models coupled with extremal dynamics
Bagatella-Flores, N.; Rodríguez-Achach, M.; Coronel-Brizio, H. F.; Hernández-Montoya, A. R.
2015-01-01
Punctuated Equilibrium (PE) states that after long periods of evolutionary quiescence, species evolution can take place in short time intervals, where sudden differentiation makes new species emerge and some species extinct. In this paper, we introduce and study the effect of punctuated equilibrium on two different asset exchange models: the yard sale model (YS, winner gets a random fraction of a poorer player's wealth) and the theft and fraud model (TF, winner gets a random fraction of the loser's wealth). The resulting wealth distribution is characterized using the Gini index. In order to do this, we consider PE as a perturbation with probability ρ of being applied. We compare the resulting values of the Gini index at different increasing values of ρ in both models. We found that in the case of the TF model, the Gini index reduces as the perturbation ρ increases, not showing dependence with the agents number. While for YS we observe a phase transition which happens around ρc = 0.79. For perturbations ρ <ρc the Gini index reaches the value of one as time increases (an extreme wealth condensation state), whereas for perturbations greater than or equal to ρc the Gini index becomes different to one, avoiding the system reaches this extreme state. We show that both simple exchange models coupled with PE dynamics give more realistic results. In particular for YS, we observe a power low decay of wealth distribution.
Multilinear Model of Heat Exchanger with Hammerstein Structure
Directory of Open Access Journals (Sweden)
Dragan Pršić
2016-01-01
Full Text Available The multilinear model control design approach is based on the approximation of the nonlinear model of the system by a set of linear models. The paper presents the method of creation of a bank of linear models of the two-pass shell and tube heat exchanger. The nonlinear model is assumed to have a Hammerstein structure. The set of linear models is formed by decomposition of the nonlinear steady-state characteristic by using the modified Included Angle Dividing method. Two modifications of this method are proposed. The first one refers to the addition to the algorithm for decomposition, which reduces the number of linear segments. The second one refers to determination of the threshold value. The dependence between decomposition of the nonlinear characteristic and the linear dynamics of the closed-loop system is established. The decoupling process is more formal and it can be easily implemented by using software tools. Due to its simplicity, the method is particularly suitable in complex systems, such as heat exchanger networks.
A Parameter-Free Semilocal Exchange Energy Functional for Two-Dimensional Quantum Systems.
Patra, Abhilash; Jana, Subrata; Samal, Prasanjit
2018-03-26
The method of constructing semilocal density functional for exchange in two dimensions using one of the premier approaches, i.e., density matrix expansion, is revisited, and an accurate functional is constructed. The form of the functional is quite simple and includes no adjustable semiempirical parameters. In it, the kinetic energy dependent momentum is used to compensate nonlocal effects of the system. The functional is then examined by considering the very well-known semiconductor quantum dot systems. And despite its very simple form, the results obtained for quantum dots containing a higher number of electrons agrees pretty well with that of the standard exact exchange theory. Some of the desired properties relevant for the two-dimensional exchange functional and the lower bound associated with it are also discussed. It is observed that the above parameter-free semilocal exchange functional satisfies most of the discussed conditions.
Chemical bond as a test of density-gradient expansions for kinetic and exchange energies
International Nuclear Information System (INIS)
Perdew, J.P.; Levy, M.; Painter, G.S.; Wei, S.; Lagowski, J.B.
1988-01-01
Errors in kinetic and exchange contributions to the molecular bonding energy are assessed for approximate density functionals by reference to near-exact Hartree-Fock values. From the molecular calculations of Allan et al. and of Lee and Ghosh, it is demonstrated that the density-gradient expansion does not accurately describe the noninteracting kinetic contribution to the bonding energy, even when this expansion is carried to fourth order and applied in its spin-density-functional form to accurate Hartree-Fock densities. In a related study, it is demonstrated that the overbinding of molecules such as N 2 and F 2 , which occurs in the local-spin-density (LSD) approximation for the exchange-correlation energy, is not attributable to errors in the self-consistent LSD densities. Contrary to expectations based upon the Gunnarsson-Jones nodality argument, it is found that the LSD approximation for the exchange energy can seriously overbind a molecule even when bonding does not create additional nodes in the occupied valence orbitals. LSD and exact values for the exchange contribution to the bonding energy are displayed and discussed for several molecules
Development of an analytical diffusion model for modeling hydrogen isotope exchange
Barton, J. L.; Wang, Y. Q.; Doerner, R. P.; Tynan, G. R.
2015-08-01
We create a model for H retention depth profiles in W and subsequently model how this profile changes after isotope exchange. This is accomplished by calculating how trapping defects in W accumulate D (or H) inventory as W is being exposed to plasma. Each trapping site is characterized by a trapping rate and a release rate, where the only free parameters are the distribution of these trapping sites in the material. The filled trap concentrations for each trap type are modeled as a diffusion process because post-mortem deuterium depth profiles indicate that traps are filled well beyond the ion implantation zone (2-5 nm). Using this retention model, an isotope exchange rate is formulated. The retention model and isotope exchange rate are compared to low temperature isotope exchange experiments in tungsten with good agreement. The limitations of the current model highlight important physics and motivate future work.
A novel dynamic kinetic model of oxygen isotopic exchange on a supported metal catalyst
Energy Technology Data Exchange (ETDEWEB)
Galdikas, Arvaidas; Duprez, Daniel; Descorme, Claude
2004-09-15
A time-resolved kinetic analysis has been developed for modeling experimental results of {sup 18}O/{sup 16}O isotopic exchange over oxide-supported metal catalysts. Model is based on two very important points: (1) the parallel calculation of surface and bulk diffusion and (2) the implication of certain O species such as superoxides. The model includes adsorption-desorption processes on metal clusters and oxygen spillover from the metal to the surface of support and vice versa. Different mechanisms of exchange were also taken into account via mononuclear (O atoms, O{sup -}, OH) or binuclear (superoxides) oxygen species. A refined model taking into account surface diffusion, direct exchange on surface of support by binuclear oxygen species and bulk diffusion was also developed. Kinetic (reaction rates and diffusion coefficients) as well as thermodynamic parameters (activation energies) were derived by fitting theoretical and experimental curves of {sup 18}O{sub 2}, {sup 18}O{sup 16}O and {sup 16}O{sub 2} gas phase concentrations versus time. The experimental results of Pt/CeZrO{sub 2} catalyst samples obtained in the 200-450 deg. C range of temperatures are examined. The refined model provides a very good fitting of the kinetic curves recorded with ceria-zirconia-supported catalysts. Moreover, values of diffusion coefficients and activation energies are in good agreement with already published values found by other methods. For a better understanding of all the steps of exchange, the kinetics of {sup 18}O and {sup 16}O distribution on the surface of metal clusters and on the surface of support are calculated and analyzed. On the basis of this model, a computer code is developed for analysis and calculations of kinetic and thermodynamic parameters of automotive catalysts.
Regions in Energy Market Models
Energy Technology Data Exchange (ETDEWEB)
Short, W.
2007-02-01
This report explores the different options for spatial resolution of an energy market model--and the advantages and disadvantages of models with fine spatial resolution. It examines different options for capturing spatial variations, considers the tradeoffs between them, and presents a few examples from one particular model that has been run at different levels of spatial resolution.
Regions in Energy Market Models
Energy Technology Data Exchange (ETDEWEB)
None
2009-01-18
This report explores the different options for spatial resolution of an energy market model and the advantages and disadvantages of models with fine spatial resolution. It examines different options for capturing spatial variations, considers the tradeoffs between them, and presents a few examples from one particular model that has been run at different levels of spatial resolution.
A continuum model for metabolic gas exchange in pear fruit.
Directory of Open Access Journals (Sweden)
Q Tri Ho
2008-03-01
Full Text Available Exchange of O(2 and CO(2 of plants with their environment is essential for metabolic processes such as photosynthesis and respiration. In some fruits such as pears, which are typically stored under a controlled atmosphere with reduced O(2 and increased CO(2 levels to extend their commercial storage life, anoxia may occur, eventually leading to physiological disorders. In this manuscript we have developed a mathematical model to predict the internal gas concentrations, including permeation, diffusion, and respiration and fermentation kinetics. Pear fruit has been selected as a case study. The model has been used to perform in silico experiments to evaluate the effect of, for example, fruit size or ambient gas concentration on internal O(2 and CO(2 levels. The model incorporates the actual shape of the fruit and was solved using fluid dynamics software. Environmental conditions such as temperature and gas composition have a large effect on the internal distribution of oxygen and carbon dioxide in fruit. Also, the fruit size has a considerable effect on local metabolic gas concentrations; hence, depending on the size, local anaerobic conditions may result, which eventually may lead to physiological disorders. The model developed in this manuscript is to our knowledge the most comprehensive model to date to simulate gas exchange in plant tissue. It can be used to evaluate the effect of environmental stresses on fruit via in silico experiments and may lead to commercial applications involving long-term storage of fruit under controlled atmospheres.
Alternate Models to Dark Energy
Arun, Kenath; Gudennavar, S B; Prasad, A; Sivaram, C
2017-01-01
One of the unresolved questions currently in cosmology is that of the non-linear accelerated expansion of the universe. This has been attributed to the so called Dark Energy (DE). The accelerated expansion of the universe is deduced from measurements of Type Ia supernovae. Here we propose alternate models to account for the Type Ia supernovae measurements without invoking dark energy.
Alternate models to dark energy
Arun, Kenath; Gudennavar, S. B.; Prasad, A.; Sivaram, C.
2018-01-01
One of the unresolved questions currently in cosmology is that of the non-linear accelerated expansion of the universe. This has been attributed to the so called Dark Energy (DE). The accelerated expansion of the universe is deduced from measurements of Type Ia supernovae. Here we propose alternate models to account for the Type Ia supernovae measurements without invoking dark energy.
Modeling inflation rates and exchange rates in Ghana: application of multivariate GARCH models.
Nortey, Ezekiel Nn; Ngoh, Delali D; Doku-Amponsah, Kwabena; Ofori-Boateng, Kenneth
2015-01-01
This paper was aimed at investigating the volatility and conditional relationship among inflation rates, exchange rates and interest rates as well as to construct a model using multivariate GARCH DCC and BEKK models using Ghana data from January 1990 to December 2013. The study revealed that the cumulative depreciation of the cedi to the US dollar from 1990 to 2013 is 7,010.2% and the yearly weighted depreciation of the cedi to the US dollar for the period is 20.4%. There was evidence that, the fact that inflation rate was stable, does not mean that exchange rates and interest rates are expected to be stable. Rather, when the cedi performs well on the forex, inflation rates and interest rates react positively and become stable in the long run. The BEKK model is robust to modelling and forecasting volatility of inflation rates, exchange rates and interest rates. The DCC model is robust to model the conditional and unconditional correlation among inflation rates, exchange rates and interest rates. The BEKK model, which forecasted high exchange rate volatility for the year 2014, is very robust for modelling the exchange rates in Ghana. The mean equation of the DCC model is also robust to forecast inflation rates in Ghana.
Variable sound speed in interacting dark energy models
Linton, Mark S.; Pourtsidou, Alkistis; Crittenden, Robert; Maartens, Roy
2018-04-01
We consider a self-consistent and physical approach to interacting dark energy models described by a Lagrangian, and identify a new class of models with variable dark energy sound speed. We show that if the interaction between dark energy in the form of quintessence and cold dark matter is purely momentum exchange this generally leads to a dark energy sound speed that deviates from unity. Choosing a specific sub-case, we study its phenomenology by investigating the effects of the interaction on the cosmic microwave background and linear matter power spectrum. We also perform a global fitting of cosmological parameters using CMB data, and compare our findings to ΛCDM.
A strategic gaming model for health information exchange markets.
Martinez, Diego A; Feijoo, Felipe; Zayas-Castro, Jose L; Levin, Scott; Das, Tapas K
2018-03-01
Current market conditions create incentives for some providers to exercise control over patient data in ways that unreasonably limit its availability and use. Here we develop a game theoretic model for estimating the willingness of healthcare organizations to join a health information exchange (HIE) network and demonstrate its use in HIE policy design. We formulated the model as a bi-level integer program. A quasi-Newton method is proposed to obtain a strategy Nash equilibrium. We applied our modeling and solution technique to 1,093,177 encounters for exchanging information over a 7.5-year period in 9 hospitals located within a three-county region in Florida. Under a set of assumptions, we found that a proposed federal penalty of up to $2,000,000 has a higher impact on increasing HIE adoption than current federal monetary incentives. Medium-sized hospitals were more reticent to adopt HIE than large-sized hospitals. In the presence of collusion among multiple hospitals to not adopt HIE, neither federal incentives nor proposed penalties increase hospitals' willingness to adopt. Hospitals' apathy toward HIE adoption may threaten the value of inter-connectivity even with federal incentives in place. Competition among hospitals, coupled with volume-based payment systems, creates no incentives for smaller hospitals to exchange data with competitors. Medium-sized hospitals need targeted actions (e.g., outside technological assistance, group purchasing arrangements) to mitigate market incentives to not adopt HIE. Strategic game theoretic models help to clarify HIE adoption decisions under market conditions at play in an extremely complex technology environment.
Energy and CO2 exchanges and influencing factors in spring wheat ...
Indian Academy of Sciences (India)
Energy and CO2 exchanges and influencing factors in spring wheat ecosystem along the Heihe River, northwestern China. Shuchen Sun1,3, Ming'an Shao1,2,∗ and Hongbei Gao4. 1State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water. Conservation, Chinese ...
International Nuclear Information System (INIS)
Winslow, A.M.
1975-01-01
The multi-frequency grey method is extended to include Compton scattering. In this way one arrives at an expression for the total Compton scattering energy exchange rate, which, for a Planckian radiation field, reduces to a well known formula. 15 references, 5 graphs
Shapkalijevski, M.M.
2017-01-01
This thesis deals with the representation of the exchange of energy, momentum and chemically reactive compounds between the land, covered by high vegetation, and the lowest part of the atmosphere, named as atmospheric boundary layer (ABL).
The study presented in this thesis introduces the
DEFF Research Database (Denmark)
Ciliberto, S.; Imparato, A.; Naert, A.
2013-01-01
We study both experimentally and theoretically the statistical properties of the energy exchanged between two electrical conductors, kept at different temperatures by two different heat reservoirs, and coupled by the electrical thermal noise. Such a system is ruled by the same equations as two...
Water and energy exchange in East Siberian forest: A synthesis, Agricultural and Forest Meteorology
Maximov, T.; Ohta, T.; Dolman, A.J.
2008-01-01
This paper summarizes and synthesises the results obtained in several recent studies on water and energy exchange of East Siberian forests located on permafrost. It is found that annual evaporation of these forests shows relatively small inter-annual variation (147-196 mm). The availability of
Energy Technology Data Exchange (ETDEWEB)
Anantharaman, Rahul
2011-07-01
This thesis focuses on energy recovery system design and energy integration to improve the energy efficiency of process plants. The objectives of this work are to (a) develop a systematic methodology based on thermodynamic principles to integrate energy intensive processes and (b) develop a mathematical programming based approach using thermodynamics and insight for solving industrial sized HENS problems. A novel energy integration methodology, Energy Level Composite Curves (ELCC), has been developed that is a synergy of Exergy Analysis and Composite Curves. ELCC is a graphical tool which provides the engineer with insights on energy integration and this work represents the first methodological attempt to represent thermal, mechanical and chemical energy in a graphical form similar to composite curves for the thermal integration of energy intensive processes. This method provides physical insight to integrate energy sources with sinks. The methodology is useful as a screening tool, functioning as an idea generator prior to the heat and power integration step. A simple energy targeting algorithm is developed to obtain utility targets. The ELCC was applied to a methanol plant to show the efficacy of the methodology.The Sequential Framework, an iterative and sequential methodology for Heat Exchanger Network Synthesis (HENS), is presented in this thesis. The main objective of the Sequential Framework is to solve industrial size problems. The subtasks of the design process are solved sequentially using Mathematical Programming. There are two main advantages of the methodology. First, the design procedure is, to a large extent, automated while keeping significant user interaction. Second, the subtasks of the framework (MILP and NLP problems) are much easier to solve numerically than the MINLP models that have been suggested for HENS. Application of the Sequential Framework to literature examples showed that the methodology generated solutions with total annualized costs
Comparison of two ESI-MS based H/D exchange methods for extracting protein folding energies
Liyanage, Rohana; Devarapalli, Nagarjuna; Puckett, Latisha M.; Phan, N. H.; Gidden, Jennifer; Stites, Wesley E.; Lay, Jackson O., Jr.
2009-10-01
In this report, the model proteins staphylococcal nuclease and ubiquitin were used to test the applicability of two new hydrogen/deuterium exchange (HX) electrospray ionization mass spectrometry (ESI-MS) methods for estimating protein folding energies. Both methods use the H/D exchange of globally protected amide protons (amide protons which are buried in the hydrophobic core) to elucidate protein folding energies. One method is a kinetic-based method and the other is equilibrium-based. The first method, the HX ESI-MS kinetic-based approach is conceptually identical to SUPREX (stability of unpurified proteins from rates of H/D exchange) method but is based on ESI-MS rather than MALDI-MS (matrix assisted laser desorption mass spectrometry). This method employs the time-dependence of H/D exchange using various denaturant concentrations to extract folding energies. Like SUPREX, this approach requires the assumption of EX2 exchange kinetics. The second method, which we call a protein equilibrium population snapshot (PEPS) by HX ESI-MS uses data collected only for a single time point (usually the shortest possible) to obtain a snapshot of the open and closed populations of the protein. The PEPS approach requires few assumptions in the derivation of the equations used for calculation of the folding energies. The extraction of folding energies from mass spectral data is simple and straightforward. The PEPS method is applicable for proteins that follow either EX1 or EX2 HX mechanisms. In our experiments the kinetic-based method produced less accurate and mGdHCl values for wild-type staphylococcal nuclease and mutants undergoing H/D exchange by EX1, as would be expected. Better results were obtained for ubiquitin which undergoes HX by an EX2 mechanism. Using the PEPS method we obtained and mGdHCl values that were in good agreement with literature values for both staphylococcal nuclease (EX1) and ubiquitin (EX2). We also show that the observation of straight lines in linear
Universal model for water costs of gas exchange by animals and plants
Woods, H. Arthur; Smith, Jennifer N.
2010-01-01
For terrestrial animals and plants, a fundamental cost of living is water vapor lost to the atmosphere during exchange of metabolic gases. Here, by bringing together previously developed models for specific taxa, we integrate properties common to all terrestrial gas exchangers into a universal model of water loss. The model predicts that water loss scales to gas exchange with an exponent of 1 and that the amount of water lost per unit of gas exchanged depends on several factors: the surface t...
Modeling Inflation Using a Non-Equilibrium Equation of Exchange
Chamberlain, Robert G.
2013-01-01
Inflation is a change in the prices of goods that takes place without changes in the actual values of those goods. The Equation of Exchange, formulated clearly in a seminal paper by Irving Fisher in 1911, establishes an equilibrium relationship between the price index P (also known as "inflation"), the economy's aggregate output Q (also known as "the real gross domestic product"), the amount of money available for spending M (also known as "the money supply"), and the rate at which money is reused V (also known as "the velocity of circulation of money"). This paper offers first a qualitative discussion of what can cause these factors to change and how those causes might be controlled, then develops a quantitative model of inflation based on a non-equilibrium version of the Equation of Exchange. Causal relationships are different from equations in that the effects of changes in the causal variables take time to play out-often significant amounts of time. In the model described here, wages track prices, but only after a distributed lag. Prices change whenever the money supply, aggregate output, or the velocity of circulation of money change, but only after a distributed lag. Similarly, the money supply depends on the supplies of domestic and foreign money, which depend on the monetary base and a variety of foreign transactions, respectively. The spreading of delays mitigates the shocks of sudden changes to important inputs, but the most important aspect of this model is that delays, which often have dramatic consequences in dynamic systems, are explicitly incorporated.macroeconomics, inflation, equation of exchange, non-equilibrium, Athena Project
Dziedzic, J; Hill, Q; Skylaris, C-K
2013-12-07
We present a method for the calculation of four-centre two-electron repulsion integrals in terms of localised non-orthogonal generalised Wannier functions (NGWFs). Our method has been implemented in the ONETEP program and is used to compute the Hartree-Fock exchange energy component of Hartree-Fock and Density Functional Theory (DFT) calculations with hybrid exchange-correlation functionals. As the NGWFs are optimised in situ in terms of a systematically improvable basis set which is equivalent to plane waves, it is possible to achieve large basis set accuracy in routine calculations. The spatial localisation of the NGWFs allows us to exploit the exponential decay of the density matrix in systems with a band gap in order to compute the exchange energy with a computational effort that increases linearly with the number of atoms. We describe the implementation of this approach in the ONETEP program for linear-scaling first principles quantum mechanical calculations. We present extensive numerical validation of all the steps in our method. Furthermore, we find excellent agreement in energies and structures for a wide variety of molecules when comparing with other codes. We use our method to perform calculations with the B3LYP exchange-correlation functional for models of myoglobin systems bound with O2 and CO ligands and confirm that the same qualitative behaviour is obtained as when the same myoglobin models are studied with the DFT+U approach which is also available in ONETEP. Finally, we confirm the linear-scaling capability of our method by performing calculations on polyethylene and polyacetylene chains of increasing length.
International Nuclear Information System (INIS)
Dziedzic, J.; Hill, Q.; Skylaris, C.-K.
2013-01-01
We present a method for the calculation of four-centre two-electron repulsion integrals in terms of localised non-orthogonal generalised Wannier functions (NGWFs). Our method has been implemented in the ONETEP program and is used to compute the Hartree-Fock exchange energy component of Hartree-Fock and Density Functional Theory (DFT) calculations with hybrid exchange-correlation functionals. As the NGWFs are optimised in situ in terms of a systematically improvable basis set which is equivalent to plane waves, it is possible to achieve large basis set accuracy in routine calculations. The spatial localisation of the NGWFs allows us to exploit the exponential decay of the density matrix in systems with a band gap in order to compute the exchange energy with a computational effort that increases linearly with the number of atoms. We describe the implementation of this approach in the ONETEP program for linear-scaling first principles quantum mechanical calculations. We present extensive numerical validation of all the steps in our method. Furthermore, we find excellent agreement in energies and structures for a wide variety of molecules when comparing with other codes. We use our method to perform calculations with the B3LYP exchange-correlation functional for models of myoglobin systems bound with O 2 and CO ligands and confirm that the same qualitative behaviour is obtained as when the same myoglobin models are studied with the DFT+U approach which is also available in ONETEP. Finally, we confirm the linear-scaling capability of our method by performing calculations on polyethylene and polyacetylene chains of increasing length
Yu, Zhitao; Miller, Franklin; Pfotenhauer, John M.
2017-12-01
Both a numerical and analytical model of the heat and mass transfer processes in a CO2, N2 mixture gas de-sublimating cross-flow finned duct heat exchanger system is developed to predict the heat transferred from a mixture gas to liquid nitrogen and the de-sublimating rate of CO2 in the mixture gas. The mixture gas outlet temperature, liquid nitrogen outlet temperature, CO2 mole fraction, temperature distribution and de-sublimating rate of CO2 through the whole heat exchanger was computed using both the numerical and analytic model. The numerical model is built using EES [1] (engineering equation solver). According to the simulation, a cross-flow finned duct heat exchanger can be designed and fabricated to validate the models. The performance of the heat exchanger is evaluated as functions of dimensionless variables, such as the ratio of the mass flow rate of liquid nitrogen to the mass flow rate of inlet flue gas.
Modeling renewable energy company risk
International Nuclear Information System (INIS)
Sadorsky, Perry
2012-01-01
The renewable energy sector is one of the fastest growing components of the energy industry and along with this increased demand for renewable energy there has been an increase in investing and financing activities. The tradeoff between risk and return in the renewable energy sector is, however, precarious. Renewable energy companies are often among the riskiest types of companies to invest in and for this reason it is necessary to have a good understanding of the risk factors. This paper uses a variable beta model to investigate the determinants of renewable energy company risk. The empirical results show that company sales growth has a negative impact on company risk while oil price increases have a positive impact on company risk. When oil price returns are positive and moderate, increases in sales growth can offset the impact of oil price returns and this leads to lower systematic risk.
Extreme value modelling of Ghana stock exchange index.
Nortey, Ezekiel N N; Asare, Kwabena; Mettle, Felix Okoe
2015-01-01
Modelling of extreme events has always been of interest in fields such as hydrology and meteorology. However, after the recent global financial crises, appropriate models for modelling of such rare events leading to these crises have become quite essential in the finance and risk management fields. This paper models the extreme values of the Ghana stock exchange all-shares index (2000-2010) by applying the extreme value theory (EVT) to fit a model to the tails of the daily stock returns data. A conditional approach of the EVT was preferred and hence an ARMA-GARCH model was fitted to the data to correct for the effects of autocorrelation and conditional heteroscedastic terms present in the returns series, before the EVT method was applied. The Peak Over Threshold approach of the EVT, which fits a Generalized Pareto Distribution (GPD) model to excesses above a certain selected threshold, was employed. Maximum likelihood estimates of the model parameters were obtained and the model's goodness of fit was assessed graphically using Q-Q, P-P and density plots. The findings indicate that the GPD provides an adequate fit to the data of excesses. The size of the extreme daily Ghanaian stock market movements were then computed using the value at risk and expected shortfall risk measures at some high quantiles, based on the fitted GPD model.
A study of model systems in anionic exchange
International Nuclear Information System (INIS)
Haegele, R.; Boeyens, J.C.A.
1977-01-01
Preliminary experiments are reported on the preparation and characterization of anionic sulphate and chloride complexes of UO 2+ 2 and iron(III), benzyl-trimethylammonium cation being used as a model substance for the simulation of positive sites in an anionic-exchange resin. The structure of (BTMA) 4 [UO 2 CL 3 -O 2 -CL 3 UO 2 ], a binuclear uranyl-peroxocomplex that has not been reported in the literature, was elucidated by single-crystal x-ray examination, and is described and discussed [af
Energy-economic policy modeling
Sanstad, Alan H.
2018-01-01
Computational models based on economic principles and methods are powerful tools for understanding and analyzing problems in energy and the environment and for designing policies to address them. Among their other features, some current models of this type incorporate information on sustainable energy technologies and can be used to examine their potential role in addressing the problem of global climate change. The underlying principles and the characteristics of the models are summarized, and examples of this class of model and their applications are presented. Modeling epistemology and related issues are discussed, as well as critiques of the models. The paper concludes with remarks on the evolution of the models and possibilities for their continued development.
Heat exchanger modelling in central receiver solar power plant using dense particle suspension
Reyes-Belmonte, Miguel A.; Gómez-García, Fabrisio; González-Aguilar, José; Romero, Manuel; Benoit, Hadrien; Flamant, Gilles
2017-06-01
In this paper, a detailed thermodynamic model for a heat exchanger (HX) working with a dense particle suspension (DPS) as heat transfer fluid (HTF) in the solar loop and water-steam as working fluid is presented. HX modelling is based on fluidized bed (FB) technology and its design has been conceived to couple solar plant using DPS as HTF and storage media with Rankine cycle for power generation. Using DPS as heat transfer fluid allows extending operating temperature range what will help to reduce thermal energy storage costs favoring higher energy densities but will also allow running power cycle at higher temperature what will increase its efficiency. Besides HX modelling description, this model will be used to reproduce solar plant performance under steady state and transient conditions.
Contrasting response of European forest and grassland energy exchange to heatwaves
DEFF Research Database (Denmark)
Teuling, A.J.; Seneviratne, S.I.; Stöckli, R.
2010-01-01
on the exchange of water and energy and the interaction of this exchange with the soil water balance during heatwaves is largely unknown. Here we analyse observations from an extensive network of flux towers in Europe that reveal a difference between the temporal responses of forest and grassland ecosystems...... and induces a critical shift in the regional climate system that leads to increased heating. We propose that this mechanism may explain the extreme temperatures in August 2003. We conclude that the conservative water use of forest contributes to increased temperatures in the short term, but mitigates...
Measuring the Effect of Exchange Rate Movements on Stock Market Returns Volatility: GARCH Model
Directory of Open Access Journals (Sweden)
Abdelkadir BESSEBA
2017-06-01
Full Text Available This paper aims to investigate the dynamic links between exchange rate fluctuations and stock market return volatility. For this purpose, we have employed a Generalized Autoregressive Conditional Heteroscedasticity model (GARCH model. Stock market returns sensitivities are found to be stronger for exchange rates, implying that exchange rate change plays an important role in determining the dynamics of the stock market returns.
Short-range second order screened exchange correction to RPA correlation energies
Beuerle, Matthias; Ochsenfeld, Christian
2017-11-01
Direct random phase approximation (RPA) correlation energies have become increasingly popular as a post-Kohn-Sham correction, due to significant improvements over DFT calculations for properties such as long-range dispersion effects, which are problematic in conventional density functional theory. On the other hand, RPA still has various weaknesses, such as unsatisfactory results for non-isogyric processes. This can in parts be attributed to the self-correlation present in RPA correlation energies, leading to significant self-interaction errors. Therefore a variety of schemes have been devised to include exchange in the calculation of RPA correlation energies in order to correct this shortcoming. One of the most popular RPA plus exchange schemes is the second order screened exchange (SOSEX) correction. RPA + SOSEX delivers more accurate absolute correlation energies and also improves upon RPA for non-isogyric processes. On the other hand, RPA + SOSEX barrier heights are worse than those obtained from plain RPA calculations. To combine the benefits of RPA correlation energies and the SOSEX correction, we introduce a short-range RPA + SOSEX correction. Proof of concept calculations and benchmarks showing the advantages of our method are presented.
Short-range second order screened exchange correction to RPA correlation energies.
Beuerle, Matthias; Ochsenfeld, Christian
2017-11-28
Direct random phase approximation (RPA) correlation energies have become increasingly popular as a post-Kohn-Sham correction, due to significant improvements over DFT calculations for properties such as long-range dispersion effects, which are problematic in conventional density functional theory. On the other hand, RPA still has various weaknesses, such as unsatisfactory results for non-isogyric processes. This can in parts be attributed to the self-correlation present in RPA correlation energies, leading to significant self-interaction errors. Therefore a variety of schemes have been devised to include exchange in the calculation of RPA correlation energies in order to correct this shortcoming. One of the most popular RPA plus exchange schemes is the second order screened exchange (SOSEX) correction. RPA + SOSEX delivers more accurate absolute correlation energies and also improves upon RPA for non-isogyric processes. On the other hand, RPA + SOSEX barrier heights are worse than those obtained from plain RPA calculations. To combine the benefits of RPA correlation energies and the SOSEX correction, we introduce a short-range RPA + SOSEX correction. Proof of concept calculations and benchmarks showing the advantages of our method are presented.
Modelling world gold prices and USD foreign exchange relationship using multivariate GARCH model
Ping, Pung Yean; Ahmad, Maizah Hura Binti
2014-12-01
World gold price is a popular investment commodity. The series have often been modeled using univariate models. The objective of this paper is to show that there is a co-movement between gold price and USD foreign exchange rate. Using the effect of the USD foreign exchange rate on the gold price, a model that can be used to forecast future gold prices is developed. For this purpose, the current paper proposes a multivariate GARCH (Bivariate GARCH) model. Using daily prices of both series from 01.01.2000 to 05.05.2014, a causal relation between the two series understudied are found and a bivariate GARCH model is produced.
Investigating convergence of the reaction γp→π±Δ and tensor meson a2 exchange at high energy
Directory of Open Access Journals (Sweden)
Byung-Geel Yu
2017-06-01
Full Text Available A Regge approach to the reaction processes γp→π−Δ++ and γp→π+Δ0 is presented for the description of existing data up to Eγ=16 GeV. The model consists of the t-channel π(139+ρ(775+a2(1320 exchanges which are reggeized from the relevant Born amplitude. Discussion is given on the minimal gauge prescription for the π exchange to render convergent the divergence of the u-channel Δ-pole in the former process. A new Lagrangian is constructed for the a2NΔ coupling in this work and applied to the process for the first time with the coupling constant deduced from the duality plus vector dominance. It is shown that, while the π exchange dominates over the process, the role of the a2 exchange is crucial rather than the ρ in reproducing the cross sections for total, differential, and photon polarization asymmetry to agree with data at high energy.
Effects of energy dependent Δ-nucleus optical potential in charge exchange reactions
International Nuclear Information System (INIS)
Helgesson, J.; Dmitriev, V.
1994-01-01
The Δ-nucleus optical potential from microscopic calculations in nuclear matter is used to study the effects of its energy dependence in charge-exchange (p, n) and ( 3 He, T) reactions. The neutron or triton spectrum is calculated via response function of a finite nucleus accounting for pion renormalization effects and short-range correlations. Only very small effects, 1-2%, were found for ( 3 He, T) reaction where the changes in the high energy part of the triton spectrum are enhanced relative to the low-energy part by ( 3 He, T) form factor. For the (p, n) reaction no visible effects were found. (orig.)
PEMFC contamination model: Foreign cation exchange with ionomer protons
St-Pierre, Jean
2011-08-01
A generic, transient fuel cell ohmic loss mathematical model was developed for the case of contaminants that ion exchange with ionomer protons. The model was derived using step changes in contaminant concentration, constant operating conditions and foreign cation transport via liquid water droplets. In addition, the effect of ionomer cations redistribution within the ionomer on thermodynamic, kinetic and mass transport losses and migration were neglected. Thus, a simpler, ideal, ohmic loss case is defined and is applicable to uncharged contaminant species and gas phase contaminants. The closed form solutions were validated using contamination data from a membrane exposed to NH3. The model needs to be validated against contamination and recovery data sets including an NH4+ contaminated membrane exposed to a water stream. A method is proposed to determine model parameters and relies on the prior knowledge of the initial ionomer resistivity. The model expands the number of previously derived cases. Most models in this inventory, derived with the assumption that the reactant is absent, lead to different dimensionless current vs. time behaviors similar to a fingerprint. These model characteristics facilitate contaminant mechanism identification. Separation between membrane and catalyst (electroinactive contaminant) contamination is conceivably possible using additional indicative cell resistance measurements. Contamination is predicted to be significantly more severe under low relative humidity conditions.
Atomic energy: exchange of letters between Canada and the European Atomic Energy Community (EURATOM)
International Nuclear Information System (INIS)
1978-01-01
Letters exchanged between the Charge d'affaires, mission of Canada to the European Communites and the Commissioner of the European Communities, concerning safeguards, levels of physical protection, and further intra-Community trade of nuclear materials exported from Canada to the European Community
Study of the mass and energy resolution of the E parallel B charge exchange analyzer for TFTR
International Nuclear Information System (INIS)
Kaita, R.; Medley, S.S.
1979-09-01
The charge exchange diagnostic for TFTR requires simultaneous multispecie (H + , D + , γ + ) analysis of particles in the energy range of 0.5 - 150 keV. The analyzer design chosen to provide this capability employs a wide gap semi-circular region of superimposed parallel electric and magnetic fields to accomplish mass and energy resolution, respectively. Combined with a large area, multi-anode microchannel plate detector, this arrangement will enable the energy distributions of protons, deuterions, and tritons to be measured concurrently as a function of time during each discharge. A computer simulation program for calculating ion trajectories through the analyzer was written that includes a realistic model of the magnetic and electrostatic fringe fields. This report presents the results of a study of the proposed E parallel B analyzer, and it reveals that the fringe fields are not detrimental to the performance of the analyzer
International Nuclear Information System (INIS)
Debeljkovic, D.Lj.; Stevic, D.Z.; Simeunovic, G.V.; Misic, M.A.
2015-01-01
The heat exchangers are frequently used as constructive elements in various plants and their dynamics is very important. Their operation is usually controlled by manipulating inlet fluid temperatures or mass flow rates. On the basis of the accepted and critically clarified assumptions, a linearized mathematical model of the cross-flow heat exchanger has been derived, taking into account the wall dynamics. The model is based on the fundamental law of energy conservation, covers all heat accumulation storages in the process, and leads to the set of partial differential equations (PDE), which solution is not possible in closed form. In order to overcome the solutions difficulties in this paper are analyzed different methods for modeling the heat exchanger: approach based on Laplace transformation, approximation of partial differential equations based on finite differences, the method of physical discretization and the transport approach. Specifying the input temperatures and output variables, under the constant initial conditions, the step transient responses have been simulated and presented in graphic form in order to compare these results for the four characteristic methods considered in this paper, and analyze its practical significance. (author)
Pickard, William F; Abraham-Shrauner, Barbara
2018-03-01
The heat exchanger is important in practical thermal processes, especially those of (i) the molten-salt storage schemes, (ii) compressed air energy storage schemes and (iii) other load-shifting thermal storage presumed to undergird a Smart Grid. Such devices, although central to the utilization of energy from sustainable (but intermittent) renewable sources, will be unfamiliar to many scientists, who nevertheless need a working knowledge of them. This tutorial paper provides a largely self-contained conceptual introduction for such persons. It begins by modelling a novel quantized exchanger, impractical as a device, but useful for comprehending the underlying thermophysics. It then reviews the one-dimensional steady-state idealization which demonstrates that effectiveness of heat transfer increases monotonically with (device length)/(device throughput). Next, it presents a two-dimensional steady-state idealization for plug flow and from it derives a novel formula for effectiveness of transfer; this formula is then shown to agree well with a finite-difference time-domain solution of the two-dimensional idealization under Hagen-Poiseuille flow. These results are consistent with a conclusion that effectiveness of heat exchange can approach unity, but may involve unwelcome trade-offs among device cost, size and throughput.
International Nuclear Information System (INIS)
Gjelsvik, E.; Johnsen, T.; Mysen, H.T.
1992-01-01
Simulation results are given of the consumption of electricity and oil in Denmark, Norway and Sweden based on the demand section of a Nordic energy market model which is in the process of being developed in Oslo under the auspices of the Nordic Council of Ministers. The model incorporates supply, and trade between countries so that it can be analyzed how trading can contribute to goals within energy and environmental policies and to cost effective activities aimed at reducing pollution. The article deals in some detail with the subject of how taxation on carbon dioxide emission can influence pollution abatement and with energy consumption development within individual sectors in individual Northern countries. The model of energy demand is described with emphasis on the individual sectors of industry, transport, service and private households. Simulation results giving the effects of energy consumption and increased taxation on fossil fuels are given. On this background the consequences of the adaption of power plants is discussed and a sketch is given of a Nordic electric power market incorporating trading. (AB) (15 refs.)
DEFF Research Database (Denmark)
Cornaton, Y.; Stoyanova, A.; Jensen, Hans Jørgen Aagaard
2013-01-01
An alternative separation of short-range exchange and correlation energies is used in the framework of second-order range-separated density-functional perturbation theory. This alternative separation was initially proposed by Toulouse and relies on a long-range-interacting wave function instead...... of the noninteracting Kohn-Sham one. When second-order corrections to the density are neglected, the energy expression reduces to a range-separated double-hybrid (RSDH) type of functional, RSDHf, where "f" stands for "full-range integrals" as the regular full-range interaction appears explicitly in the energy...... on the potential energy curves in the equilibrium region, improving the accuracy of binding energies and equilibrium bond distances when second-order perturbation theory is appropriate....
Optimal energy exchange of an industrial cogeneration in a day-ahead electricity market
International Nuclear Information System (INIS)
Yusta, J.M.; De Oliveira-De Jesus, P.M.; Khodr, H.M.
2008-01-01
This paper addresses an optimal strategy for the daily energy exchange of a 22-MW combined-cycle cogeneration plant of an industrial factory operating in a liberalized electricity market. The optimization problem is formulated as a Mixed-Integer Linear Programming Problem (MILP) that maximizes the profit from energy exchange of the cogeneration, and is subject to the technical constraints and the industrial demand profile. The integer variables are associated with export or import of electricity whereas the real variables relate to the power output of gas and steam turbines, and to the electricity purchased from or sold to the market. The proposal is applied to a real cogeneration plant in Spain where the detailed cost function of the process is obtained. The problem is solved using a large-scale commercial package and the results are discussed and compared with different predefined scheduling strategies. (author)
Comparison of Methods for Computing the Exchange Energy of quantum helium and hydrogen
International Nuclear Information System (INIS)
Cayao, J. L. C. D.
2009-01-01
I investigate approach methods to find the exchange energy for quantum helium and hydrogen. I focus on Heitler-London, Hund-Mullikan, Molecular Orbital and variational approach methods. I use Fock-Darwin states centered at the potential minima as the single electron wavefunctions. Using these we build Slater determinants as the basis for the two electron problem. I do a comparison of methods for two electron double dot (quantum hydrogen) and for two electron single dot (quantum helium) in zero and finite magnetic field. I show that the variational, Hund-Mullikan and Heitler-London methods are in agreement with the exact solutions. Also I show that the exchange energy calculation by Heitler-London (HL) method is an excellent approximation for large inter dot distances and for single dot in magnetic field is an excellent approximation the Variational method. (author)
Modeling the dynamic operation of a small fin plate heat exchanger - parametric analysis
Motyliński, Konrad; Kupecki, Jakub
2015-09-01
Given its high efficiency, low emissions and multiple fuelling options, the solid oxide fuel cells (SOFC) offer a promising alternative for stationary power generators, especially while engaged in micro-combined heat and power (μ-CHP) units. Despite the fact that the fuel cells are a key component in such power systems, other auxiliaries of the system can play a critical role and therefore require a significant attention. Since SOFC uses a ceramic material as an electrolyte, the high operating temperature (typically of the order of 700-900 °C) is required to achieve sufficient performance. For that reason both the fuel and the oxidant have to be preheated before entering the SOFC stack. Hot gases exiting the fuel cell stack transport substantial amount of energy which has to be partly recovered for preheating streams entering the stack and for heating purposes. Effective thermal integration of the μ-CHP can be achieved only when proper technical measures are used. The ability of efficiently preheating the streams of oxidant and fuel relies on heat exchangers which are present in all possible configurations of power system with solid oxide fuel cells. In this work a compact, fin plate heat exchanger operating in the high temperature regime was under consideration. Dynamic model was proposed for investigation of its performance under the transitional states of the fuel cell system. Heat exchanger was simulated using commercial modeling software. The model includes key geometrical and functional parameters. The working conditions of the power unit with SOFC vary due to the several factors, such as load changes, heating and cooling procedures of the stack and others. These issues affect parameters of the incoming streams to the heat exchanger. The mathematical model of the heat exchanger is based on a set of equations which are simultaneously solved in the iterative process. It enables to define conditions in the outlets of both the hot and the cold sides
Modeling the dynamic operation of a small fin plate heat exchanger – parametric analysis
Directory of Open Access Journals (Sweden)
Motyliński Konrad
2015-09-01
Full Text Available Given its high efficiency, low emissions and multiple fuelling options, the solid oxide fuel cells (SOFC offer a promising alternative for stationary power generators, especially while engaged in micro-combined heat and power (μ-CHP units. Despite the fact that the fuel cells are a key component in such power systems, other auxiliaries of the system can play a critical role and therefore require a significant attention. Since SOFC uses a ceramic material as an electrolyte, the high operating temperature (typically of the order of 700–900 °C is required to achieve sufficient performance. For that reason both the fuel and the oxidant have to be preheated before entering the SOFC stack. Hot gases exiting the fuel cell stack transport substantial amount of energy which has to be partly recovered for preheating streams entering the stack and for heating purposes. Effective thermal integration of the μ-CHP can be achieved only when proper technical measures are used. The ability of efficiently preheating the streams of oxidant and fuel relies on heat exchangers which are present in all possible configurations of power system with solid oxide fuel cells. In this work a compact, fin plate heat exchanger operating in the high temperature regime was under consideration. Dynamic model was proposed for investigation of its performance under the transitional states of the fuel cell system. Heat exchanger was simulated using commercial modeling software. The model includes key geometrical and functional parameters. The working conditions of the power unit with SOFC vary due to the several factors, such as load changes, heating and cooling procedures of the stack and others. These issues affect parameters of the incoming streams to the heat exchanger. The mathematical model of the heat exchanger is based on a set of equations which are simultaneously solved in the iterative process. It enables to define conditions in the outlets of both the hot and the
Papailiou, D. D. (Editor)
1975-01-01
Concepts are described that presently appear to have the potential for propulsion applications in the post-1990 era of space technology. The studies are still in progress, and only the current status of investigation is presented. The topics for possible propulsion application are lasers, nuclear fusion, matter-antimatter annihilation, electronically excited helium, energy exchange through the interaction of various fields, laser propagation, and thermonuclear fusion technology.
A Laboratory Exercise Using a Physical Model for Demonstrating Countercurrent Heat Exchange
Loudon, Catherine; Davis-Berg, Elizabeth C.; Botz, Jason T.
2012-01-01
A physical model was used in a laboratory exercise to teach students about countercurrent exchange mechanisms. Countercurrent exchange is the transport of heat or chemicals between fluids moving in opposite directions separated by a permeable barrier (such as blood within adjacent blood vessels flowing in opposite directions). Greater exchange of…
Self-Service Banking: Value Creation Models and Information Exchange
Directory of Open Access Journals (Sweden)
Ragnvald Sannes
2001-01-01
Full Text Available This paper argues that most banks have failed to exploit the potential of self-service banking because they base their service design on an incomplete business model for self-service. A framework for evaluation of self-service banking concepts is developed on the basis of Stabell and Fjeldstad's three value configurations. The value network and the value shop are consistent with self-service banking while the value chain is inappropriate. The impact of the value configurations on information exchange and self-service functionality is discussed, and a framework for design of such services proposed. Current self-service banking practices are compared to the framework, and it is concluded that current practice matches the concept of a value network and not the value shop. However, current practices are only a partial implementation of a value network-based self-service banking concept.
Enterprise Networks for Competences Exchange: A Simulation Model
Remondino, Marco; Pironti, Marco; Pisano, Paola
A business process is a set of logically related tasks performed to achieve a defined business and related to improving organizational processes. Process innovation can happen at various levels: incrementally, redesign of existing processes, new processes. The knowledge behind process innovation can be shared, acquired, changed and increased by the enterprises inside a network. An enterprise can decide to exploit innovative processes it owns, thus potentially gaining competitive advantage, but risking, in turn, that other players could reach the same technological levels. Or it could decide to share it, in exchange for other competencies or money. These activities could be the basis for a network formation and/or impact the topology of an existing network. In this work an agent based model is introduced (E3), aiming to explore how a process innovation can facilitate network formation, affect its topology, induce new players to enter the market and spread onto the network by being shared or developed by new players.
The geothermal energy, a model energy
International Nuclear Information System (INIS)
2004-11-01
This book, largely illustrated by photos maps and schemes, takes stock on the knowledge on the geothermal energy, the low and high energy applications and the evolutions. Examples describe the french context and the channels of heat and electric power production. (A.L.B.)
Computational fluid dynamics modeling of proton exchange membrane fuel cells
Energy Technology Data Exchange (ETDEWEB)
UM,SUKKEE; WANG,C.Y.; CHEN,KEN S.
2000-02-11
A transient, multi-dimensional model has been developed to simulate proton exchange membrane (PEM) fuel cells. The model accounts simultaneously for electrochemical kinetics, current distribution, hydrodynamics and multi-component transport. A single set of conservation equations valid for flow channels, gas-diffusion electrodes, catalyst layers and the membrane region are developed and numerically solved using a finite-volume-based computational fluid dynamics (CFD) technique. The numerical model is validated against published experimental data with good agreement. Subsequently, the model is applied to explore hydrogen dilution effects in the anode feed. The predicted polarization cubes under hydrogen dilution conditions are found to be in qualitative agreement with recent experiments reported in the literature. The detailed two-dimensional electrochemical and flow/transport simulations further reveal that in the presence of hydrogen dilution in the fuel stream, hydrogen is depleted at the reaction surface resulting in substantial kinetic polarization and hence a lower current density that is limited by hydrogen transport from the fuel stream to the reaction site.
North, G. R.; Cahalan, R. F.; Coakley, J. A., Jr.
1980-01-01
An introductory survey of the global energy balance climate models is presented with an emphasis on analytical results. A sequence of increasingly complicated models involving ice cap and radiative feedback processes are solved and the solutions and parameter sensitivities are studied. The model parameterizations are examined critically in light of many current uncertainties. A simple seasonal model is used to study the effects of changes in orbital elements on the temperature field. A linear stability theorem and a complete nonlinear stability analysis for the models are developed. Analytical solutions are also obtained for the linearized models driven by stochastic forcing elements. In this context the relation between natural fluctuation statistics and climate sensitivity is stressed.
Investigation of heat exchangers for energy conversion systems of megawatt-class space power plants
Ilmov, D. N.; Mamontov, Yu. N.; Skorohodov, A. S.; Smolyarov, V. A.; Filatov, N. I.
2016-01-01
The specifics of operation (high temperatures in excess of 1000 K and large pressure drops of several megapascals between "hot" and "cold" coolant paths) of heat exchangers in the closed circuit of a gasturbine power converter operating in accordance with the Brayton cycle with internal heat recovery are analyzed in the context of construction of space propulsion systems. The design of a heat-exchange matrix made from doubly convex stamped plates with a specific surface relief is proposed. This design offers the opportunity to construct heat exchangers with the required parameters (strength, rigidity, weight, and dimensions) for the given operating conditions. The diagram of the working area of a test bench is presented, and the experimental techniques are outlined. The results of experimental studies of heat exchange and flow regimes in the models of heat exchangers with matrices containing 50 and 300 plates for two pairs of coolants (gas-gas and gas-liquid) are detailed. A criterion equation for the Nusselt number in the range of Reynolds numbers from 200 to 20 000 is proposed. The coefficients of hydraulic resistance for each coolant path are determined as functions of the Reynolds number. It is noted that the pressure in the water path in the "gas-liquid" series of experiments remained almost constant. This suggests that no well-developed processes of vaporization occurred within this heat-exchange matrix design even when the temperature drop between gas and water was as large as tens or hundreds of degrees. The obtained results allow one to design flight heat exchangers for various space power plants.
Test results of heat exchanger cleaning in support of ocean thermal energy conversion
Lott, D. F.
1980-12-01
This report documents tests conducted at the Naval Coastal Systems Center (NCSC) in support of the Department of Energy's Ocean Thermal Energy Conversion (OTEC) Program. These tests covered the period September 1978 to May 1980 and evaluated flow-driven brushes, recirculating sponge rubber balls, chlorination, and mechanical system/chlorination combinations for in-situ cleaning of two potential heat exchanger materials: titanium and aluminum alloy 5052. Tests were successful when fouling resistance was 0.0003 sq. ft. hr-F/Btu. Results indicated systems and cleaning techniques using brushes, soft sponge balls, and various concentrations of chlorine had some potential for maintaining heat transfer efficiency.
Directory of Open Access Journals (Sweden)
Patrícia S. de S. Gondim
2015-01-01
Full Text Available A micrometeorological experiment was conducted over grasslands in a semi-arid region of north-eastern Brazil (São João, Pernambuco from January to December 2011, using the Bowen ratio energy balance method, to improve the current understanding of energy partitioning and water vapour exchange over this ecosystem in this region. The objectives of the present study were to quantify the seasonal and diurnal variations in energy and water vapour exchanges over grasslands and understand the biotic and abiotic factors controlling the energy partitioning of this ecosystem. In the dry period, the low stored soil water limited the grass production and leaf area index, and as a consequence of these conditions, most of the annual net radiation (58% was consumed in sensible heat flux. During the course of the study the evaporative fraction was linearly related to the leaf area index. The total annual evapotranspiration and its daily maximum were 543.8 mm and 3.14 mm d-1. The seasonal and diurnal variations in energy partitioning and evapotranspiration were controlled by soil water availability and leaf area index.
Mathematical model development of heat and mass exchange processes in the outdoor swimming pool
Directory of Open Access Journals (Sweden)
M. V. Shaptala
2014-12-01
Full Text Available Purpose. Currently exploitation of outdoor swimming pools is often not cost-effective and, despite of their relevance, such pools are closed in large quantities. At this time there is no the whole mathematical model which would allow assessing qualitatively the effect of energy-saving measures. The aim of this work is to develop a mathematical model of heat and mass exchange processes for calculating basic heat and mass losses that occur during its exploitation. Methodology. The method for determination of heat and mass loses based on the theory of similarity criteria equations is used. Findings. The main types of heat and mass losses of outdoor pool were analyzed. The most significant types were allocated and mathematically described. Namely: by evaporation of water from the surface of the pool, by natural and forced convection, by radiation to the environment, heat consumption for water heating. Originality. The mathematical model of heat and mass exchange process of the outdoor swimming pool was developed, which allows calculating the basic heat and mass loses that occur during its exploitation. Practical value. The method of determining heat and mass loses of outdoor swimming pool as a software system was developed and implemented. It is based on the mathematical model proposed by the authors. This method can be used for the conceptual design of energy-efficient structures of outdoor pools, to assess their use of energy-intensive and selecting the optimum energy-saving measures. A further step in research in this area is the experimental validation of the method of calculation of heat losses in outdoor swimming pools with its use as an example the pool of Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan. The outdoor pool, with water heating- up from the boiler room of the university, is operated year-round.
Energy Technology Data Exchange (ETDEWEB)
Medlyn, B.E.; McMurtrie, R.E. [New South Wales Univ., Sydney (Australia). School of Biological, Earth and Environmental Sciences; Robinson, A.P. [Idaho Univ., Moscow, ID (United States). Dept. of Forest Resources; Clement, R. [Edinburgh Univ., Edinburgh (United Kingdom). School of Geosciences
2005-07-01
With the advent of eddy covariance technology, long-term records of hourly ecosystem mass and energy exchange are become available for forests. This study reviewed some of the problems associated with the standard methods of evaluating the performance of forest function models against eddy covariance data, such as equifinality, or the possibility that different models can generate similar results; the dominance of the effects of incident photosynthetically active radiation (PAR) over annual and diurnal cycles; and the uncertainty associated with some parameters, data and model structures. Several methods for improving the evaluation of model performance were reviewed and a set of simple models of ecosystem carbon exchange were shown. These included a model of gross primary productivity (GPP) and 2 alternative models of ecosystem respiration. The primary objective was to validate the GPP model and to determine which of the 2 respiration models provides the best data. The major sources of uncertainty in the GPP model were identified using sensitivity and uncertainty analysis. Although the major environmental effects on GPP were sufficiently captured by the GPP model, it was not possible to distinguish between the 2 respiration models. Both models gave similar results for current environmental conditions. It was concluded that the simple models are adequate for modeling carbon dioxide exchange of Scottish Sitka spruce forests under current conditions. However, the models cannot be used to extrapolate into future conditions. 72 refs., 7 tabs., 8 figs., 2 appendices.
Reactive transport modeling of multicomponent cation exchange at the laboratory and field scale
International Nuclear Information System (INIS)
Steefel, Carl I.
2004-01-01
Multicomponent ion exchange models have been successful in describing the chromatographic separation of cations in both laboratory and field settings. Their chief advantage lies in their ability to capture the competitive effects of other cations that may be present. By incorporating exchanger activity coefficients calculated on the basis of the Gibbs-Duhem equation applied to the exchanger phase, it is possible to correct for the non-ideality of exchange. The use of multiple exchange sites can also substantially improve the ability of the cation exchange models to describe adsorption and retardation. All of these benefits are associated with relatively little additional computational burden. Even where the cost of the multicomponent cation exchange calculations are considered too high, the models are useful in calculating distribution coefficients for the environmental conditions of interest
Wu, Chen-Lu; Zhao, Shui-Ping; Yu, Bi-Lian
2015-05-01
Exchangeable apolipoproteins play an important role in systemic lipid metabolism, especially for lipoproteins with which they are associated. Recently, emerging evidence has suggested that exchangeable apolipoproteins, such as apolipoprotein A4 (apoA4), apolipoprotein A5 (apoA5), apolipoprotein C3 (apoC3) and apolipoprotein E (apoE), also exert important effects on intracellular lipid homeostasis. There is a close link between lipid metabolism in adipose tissue and liver because the latter behaves as the metabolic sensor of dysfunctional adipose tissue and is a main target of lipotoxicity. Given that the energy balance between these two major lipogenic organs is intimately involved in the pathogenesis of obesity and non-alcoholic fatty liver disease (NAFLD), we here review recent findings concerning the intracellular function of exchangeable apolipoproteins in triglyceride metabolism in adipocytes and hepatocytes. These apolipoproteins may act as mediators of crosstalk between adipose tissue and liver, thus influencing development of obesity and hepatosteatosis. This review provides new insights into the physiological role of exchangeable apolipoproteins and identifies latent targets for therapeutic intervention of obesity and its related disorders. © 2014 The Authors. Biological Reviews © 2014 Cambridge Philosophical Society.
Schelenz, Sophie; Dietrich, Peter; Vienken, Thomas
2016-04-01
A sustainable thermal exploitation of the shallow subsurface requires a precise understanding of all relevant heat transport processes. Currently, planning practice of shallow geothermal systems (especially for systems source while the impact of groundwater flow as the driver for advective heat transport is neglected or strongly simplified. The presented study proves that those simplifications of complex geological and hydrogeological subsurface characteristics are insufficient for a precise evaluation of site-specific energy extraction rates. Based on synthetic model scenarios with varying subsurface conditions (groundwater flow velocity and aquifer thickness) the impact of advection on induced long term temperature changes in 5 and 10 m distance of the borehole heat exchanger is presented. Extending known investigations, this study enhances the evaluation of shallow geothermal energy extraction rates by considering conductive and advective heat transport under varying aquifer thicknesses. Further, it evaluates the impact of advection on installation lengths of the borehole heat exchanger to optimize the initial financial investment. Finally, an evaluation approach is presented that classifies relevant heat transport processes according to their Péclet number to enable a first quantitative assessment of the subsurface energy regime and recommend further investigation and planning procedures.
A two level hierarchical model of protein retention in ion exchange chromatography.
Salvalaglio, Matteo; Paloni, Matteo; Guelat, Bertrand; Morbidelli, Massimo; Cavallotti, Carlo
2015-09-11
Predicting protein retention in ion exchange chromatography (IEX) from first principles is a fascinating perspective. In this work a two level hierarchical modeling strategy is proposed in order to calculate protein retention factors. Model predictions are tested against experimental data measured for Lysozyme and Chymotrypsinogen A in IEX columns as a function of ionic strength and pH. At the highest level of accuracy Molecular Dynamics (MD) simulations in explicit water are used to determine the interaction free energy between each of the two proteins and the IEX stationary phase for a reference pH and ionic strength. At a lower level of accuracy a linear response model based on an implicit treatment of solvation and adopting a static protein structure is used to calculate interaction free energies for the full range of pHs and ionic strengths considered. A scaling coefficient, determined comparing MD and implicit solvent simulations, is then introduced in order to correct the linear response model for errors induced by the adoption of a static protein structure. The calculated free energies are then used to compute protein retention factors, which can be directly compared with experimental data. The possibility to introduce a third level of accuracy is explored testing the predictions of a semiempirical model. A quantitative agreement between the predicted and measured protein retention factors is obtained using the coupled MD-linear response models, supporting the reliability of the proposed approach. The model allows quantifying the electrostatic, van der Waals, and conformational contributions to the interaction free energies. A good agreement between experiments and model is obtained also using the semiempirical model that, although requiring parameterization over higher level models or experimental data, proves to be useful in order to rapidly determine protein retention factors across wide pH and ionic strength ranges as it is computationally inexpensive
Monotonic entropy growth for a nonlinear model of random exchanges.
Apenko, S M
2013-02-01
We present a proof of the monotonic entropy growth for a nonlinear discrete-time model of a random market. This model, based on binary collisions, also may be viewed as a particular case of Ulam's redistribution of energy problem. We represent each step of this dynamics as a combination of two processes. The first one is a linear energy-conserving evolution of the two-particle distribution, for which the entropy growth can be easily verified. The original nonlinear process is actually a result of a specific "coarse graining" of this linear evolution, when after the collision one variable is integrated away. This coarse graining is of the same type as the real space renormalization group transformation and leads to an additional entropy growth. The combination of these two factors produces the required result which is obtained only by means of information theory inequalities.
On quark model relations for hypercharge-exchange reactions
International Nuclear Information System (INIS)
Kluyver, J.C.; Blokzijl, R.; Massaro, G.G.G.; Wolters, G.F.; Grossmann, P.; Lamb, P.R.; Wells, J.
1978-01-01
Peripheral two-body reactions of the type K - p → M 0 + Λ, Σ 0 or Σ 0 (1385) are considered. Predictions based on the additive quark model and SU(6) baryon wave functions are tested against data on cross sections and polarisations for given momentum transfer. Data obtained in a high statistics experiment at 4.2 GeV/c K - momentum, as well as data from a large variety of other experiments are used. Highly significant violations of these predictions are observed in the data. These violations are shown to occur in a systematic fashion, according to which SU(6) must be relaxed, but the amplitude structure implied by additivity would remain valid. As an application an amplitude analysis for natural parity exchange reactions with M 0 = π, phi and rho respectively is performed, which determines a relative phase, which cannot be obtained in model-independent analysis. Also reactions with M 0 = delta or B are considered, and some implications for coupling constants are discussed. (Auth.)
Ammonium Bicarbonate Transport in Anion Exchange Membranes for Salinity Gradient Energy
Geise, Geoffrey M.
2013-09-17
Many salinity gradient energy technologies such as reverse electrodialysis (RED) rely on highly selective anion transport through polymeric anion exchange membranes. While there is considerable interest in using thermolytic solutions such as ammonium bicarbonate (AmB) in RED processes for closed-loop conversion of heat energy to electricity, little is known about membrane performance in this electrolyte. The resistances of two commercially available cation exchange membranes in AmB were lower than their resistances in NaCl. However, the resistances of commercially available anion exchange membranes (AEMs) were much larger in AmB than in NaCl, which would adversely affect energy recovery. The properties of a series of quaternary ammonium-functionalized poly(phenylene oxide) and Radel-based AEMs were therefore examined to understand the reasons for increased resistance in AmB to overcome this performance penalty due to the lower mobility of bicarbonate, 4.59 × 10-4 cm2/(V s), compared to chloride, 7.90 × 10-4 cm2/(V s) (the dilute aqueous solution mobility ratio of HCO3 - to Cl- is 0.58). Most membrane resistances were generally consistent with the dilute solution mobilities of the anions. For a few key samples, however, increased water uptake in AmB solution reduced the ionic resistance of the polymer compared to its resistance in NaCl solution. This increased water uptake was attributed to the greater hydration of the bicarbonate ion compared to the chloride ion. The increased resistance due to the use of bicarbonate as opposed to chloride ions in AEMs can therefore be mitigated by designing polymers that swell more in AmB compared to NaCl solutions, enabling more efficient energy recovery using AmB thermolytic solutions in RED. © 2013 American Chemical Society.
U.S. Department of Energy national technology information exchange workshops
International Nuclear Information System (INIS)
Daub, G.J.; Earle, S.D.; Smibert, A.M.; Wight, E.H.
1994-01-01
The U.S. Department of Energy National Technology Information Exchange (TIE) Workshops bring together environmental restoration and technology development personnel to exchange and share problems, needs, technological solutions, ideas, and successes and failures from lessons learned at DOE sites. The success of this forum is measured by the knowledge gained, contacts made, and program dollars saved by the people who actually do the work in the field. TIE is a unique opportunity to unite the DOE community and allow individuals to listen and to learn about each others' problems and solutions. By using today's technologies better, the National TIE Workshops help identify and implement cost-effective and appropriate technologies to meet the needs of the DOE environmental restoration program
Chipuk, Joseph E; Brodbelt, Jennifer S
2007-04-01
Gas-phase hydrogen/deuterium (H/D) exchange reactions for deprotonated 2'-deoxy-5'-monophosphate and 2'-deoxy-3'-monophosphate nucleotides with D(2)O were performed in a quadrupole ion trap mass spectrometer. To augment these experiments, molecular modeling was also conducted to identify likely deprotonation sites and potential gas-phase conformations of the anions. A majority of the 5'-monophosphates exchanged extensively with several of the compounds completely incorporating deuterium in place of their labile hydrogen atoms. In contrast, most of the 3'-monophosphate isomers exchanged relatively few hydrogen atoms, even though the rate of the first two exchanges was greater than observed for the 5'-monophosphates. Mononucleotides that failed to incorporate more than two deuterium atoms under default reaction conditions were often found to exchange more extensively when reactions were performed under higher energy conditions. Integration of the experimental and theoretical results supports the use of a relay exchange mechanism and suggests that the exchange behavior depends highly on the identity and orientation of the nucleobase and the position and flexibility of the deprotonated phosphate moiety. These observations also highlight the importance of the distance between the various participating groups in addition to their gas-phase acidity and basicity.
Mathematical model of heat-mass exchange processes in a flat solar collector SUN 1
Directory of Open Access Journals (Sweden)
Tunik Aleksandr Aleksandrovich
2016-01-01
Full Text Available In a flat solar collector SUN 1 The active development of environmental friendly energy sources alternative to HPPs is currently of great importance in the world. Such alternative energy sources are: water, ground, sun, wind, biofuel, etc. If we have a look at the atlas of solar energy resources on the territory of Russia, we can make a conclusion, that in many regions of our country solar activity level allows using solar collector. Though the analysis of different models of solar collector showed, that most of them are ineffective in the regions with cold climate, though the solar activity of these regions is of a great level. In this regard, a mathematical model of heat-mass exchange processes in flat solar collectors is introduced in this article. The model was a basis for the development of a new solar collector, named SUN 1, which has an original heating tubes form. This form allows heat transfer medium to be under the influence of solar energy for a longer time and consequently to warm to a higher temperature, increasing the warming rapidity.
Balmorel open source energy system model
DEFF Research Database (Denmark)
Wiese, Frauke; Bramstoft, Rasmus; Koduvere, Hardi
2018-01-01
As the world progresses towards a cleaner energy future with more variable renewable energy sources, energy system models are required to deal with new challenges. This article describes design, development and applications of the open source energy system model Balmorel, which is a result of a l...... transport of local biomass as part of the optimisation and speeding up the model....
Thermal dispersivity based calibration of a numerical borehole heat exchanger model
Wagner, Valentin; Bayer, Peter; Bisch, Gerhard; Klaas, Norbert; Braun, Jürgen; Blum, Philipp
2013-04-01
Shallow geothermal energy is used worldwide as a heat and/or cooling source for buildings. The most often used technique to exploit energy from the subsurface is ground source heat pump systems in combination with a borehole heat exchanger (BHE). The BHE consists either of one U-pipe, two U-pipes or a coaxial pipe, which are inserted in a borehole. The remaining void space is filled with a grouting material to improve the thermal connection between the pipes and the subsurface and to protect the subsurface if there is a leakage in the pipes. In the pipes, a heat carrier fluid is circulated to establish a thermal gradient around the BHE and thus promote conductive heat transfer. This causes a temperature anomaly in the subsurface. Extension and magnitude of such temperature anomalies do not only depend on the amount of exchanged energy, but also on the characteristics of the ground and the installed ground source heat pump system itself. In this study, we developed a high-resolution finite element BHE model to simulate the heat propagation from a BHE to the subsurface or vice versa. First, the resulting heat propagation predicted by the numerical model is compared to the analogous analytical solutions. Then the numerical model is calibrated based on a large-scale geothermal tank experiment. The tank has a size of 9m × 6m × 4.5m (length × width × depth), and it hosts a layered artificial aquifer with four BHEs, which are surrounded by a dense temperature sensor network (> 150 PT-100 temperature sensors). In the tank, a hydraulic gradient can be established and thus groundwater flow can be imitated. By calibrating the numerical model, the sensitivity of longitudinal and transversal dispersivity values is evaluated. Our analysis cannot prove that the commonly assumed ratio of 1:10 between transversal and longitudinal dispersivity is correct. Rather, it is shown that there exists a wide range of possible parameter value combinations.
Fox, Douglas M; Rodriguez, Rebeca S; Devilbiss, Mackenzie N; Woodcock, Jeremiah; Davis, Chelsea S; Sinko, Robert; Keten, Sinan; Gilman, Jeffrey W
2016-10-12
Cellulose nanocrystals (CNCs) have great potential as sustainable reinforcing materials for polymers, but there are a number of obstacles to commercialization that must first be overcome. High levels of water absorption, low thermal stabilities, poor miscibility with nonpolar polymers, and irreversible aggregation of the dried CNCs are among the greatest challenges to producing cellulose nanocrystal-polymer nanocomposites. A simple, scalable technique to modify sulfated cellulose nanocrystals (Na-CNCs) has been developed to address all of these issues. By using an ion exchange process to replace Na + with imidazolium or phosphonium cations, the surface energy is altered, the thermal stability is increased, and the miscibility of dried CNCs with a nonpolar polymer (epoxy and polystyrene) is enhanced. Characterization of the resulting ion exchanged CNCs (IE-CNCs) using potentiometry, inverse gas chromatography, dynamic vapor sorption, and laser scanning confocal microscopy reveals that the IE-CNCs have lower surface energies, adsorb less water, and have thermal stabilities of up to 100 °C higher than those of prepared protonated cellulose nanocrystals (H-CNCs) and 40 °C higher than that of neutralized Na-CNC. Methyl(triphenyl)phosphonium exchanged cellulose nanocrystals (MePh 3 P-CNC) adsorbed 30% less water than Na-CNC, retained less water during desorption, and were used to prepare well-dispersed epoxy composites without the aid of a solvent and well-dispersed polystyrene nanocomposites using a melt blending technique at 195 °C. Predictions of dispersion quality and glass transition temperatures from molecular modeling experiments match experimental observations. These fiber-reinforced polymers can be used as lightweight composites in transportation, infrastructure, and renewable energy applications.
Modeling and estimating the jump risk of exchange rates: Applications to RMB
Wang, Yiming; Tong, Hanfei
2008-11-01
In this paper we propose a new type of continuous-time stochastic volatility model, SVDJ, for the spot exchange rate of RMB, and other foreign currencies. In the model, we assume that the change of exchange rate can be decomposed into two components. One is the normally small-cope innovation driven by the diffusion motion; the other is a large drop or rise engendered by the Poisson counting process. Furthermore, we develop a MCMC method to estimate our model. Empirical results indicate the significant existence of jumps in the exchange rate. Jump components explain a large proportion of the exchange rate change.
Energy exchangers with LCT as a precision method for diet control in LCHADD.
Mozrzymas, Renata; Konikowska, Klaudia; Regulska-Ilow, Bożena
2017-01-01
Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) is a rare genetic disease. The LCHADD treatment is mainly based on special diet. In this diet, energy from long-chain triglycerides (LCT) cannot exceed 10%, however energy intake from the consumption of medium-chain triglycerides (MCTs) should increase. The daily intake of energy should be compatible with energy requirements and treatment should involve frequent meals including during the night to avoid periods of fasting. In fact, there are no recommendations for total content of LCT in all of the allowed food in the LCHADD diet. The aim of the study was to present a new method of diet composition in LCHADD with the use of blocks based on energy exchangers with calculated LCT content. In the study, the diet schema was shown for calculating the energy requirements and LCT content in the LCHADD diet. How to create the diet was also shown, based on a food pyramid developed for patients with LCHADD. The blocks will make it possible, in a quick and simple way, to create a balanced diet which provides adequate energy value, essential nutrients and LCT content. This method can be used by doctors and dietitians who specialize in treating rare metabolic diseases. It can also be used by patients and their families for accurate menu planning with limited LCT content.
Evaluating Energy Efficiency Policies with Energy-Economy Models
Energy Technology Data Exchange (ETDEWEB)
Mundaca, Luis; Neij, Lena; Worrell, Ernst; McNeil, Michael A.
2010-08-01
The growing complexities of energy systems, environmental problems and technology markets are driving and testing most energy-economy models to their limits. To further advance bottom-up models from a multidisciplinary energy efficiency policy evaluation perspective, we review and critically analyse bottom-up energy-economy models and corresponding evaluation studies on energy efficiency policies to induce technological change. We use the household sector as a case study. Our analysis focuses on decision frameworks for technology choice, type of evaluation being carried out, treatment of market and behavioural failures, evaluated policy instruments, and key determinants used to mimic policy instruments. Although the review confirms criticism related to energy-economy models (e.g. unrealistic representation of decision-making by consumers when choosing technologies), they provide valuable guidance for policy evaluation related to energy efficiency. Different areas to further advance models remain open, particularly related to modelling issues, techno-economic and environmental aspects, behavioural determinants, and policy considerations.
International Nuclear Information System (INIS)
Plakida, N. M.; Anton, L.; Adam, S. . Department of Theoretical Physics, Horia Hulubei National Institute for Physics and Nuclear Engineering, PO Box MG-6, RO-76900 Bucharest - Magurele; RO); Adam, Gh. . Department of Theoretical Physics, Horia Hulubei National Institute for Physics and Nuclear Engineering, PO Box MG-6, RO-76900 Bucharest - Magurele; RO)
2001-01-01
A microscopical theory of superconductivity in the two-band singlet-hole Hubbard model, in the strong coupling limit in a paramagnetic state, is developed. The model Hamiltonian is obtained by projecting the p-d model to an asymmetric Hubbard model with the lower Hubbard subband occupied by one-hole Cu d-like states and the upper Hubbard subband occupied by two-hole p-d singlet states. The model requires two microscopical parameters only, the p-d hybridization parameter t and the charge-transfer gap Δ. It was previously shown to secure an appropriate description of the normal state properties of the high -T c cuprates. To treat rigorously the strong correlations, the Hubbard operator technique within the projection method for the Green function is used. The Dyson equation is derived. In the molecular field approximation, d-wave superconducting pairing of conventional hole (electron) pairs in one Hubbard subband is found, which is mediated by the exchange interaction given by the interband hopping, J ij = 4 (t ij ) 2 / Δ. The normal and anomalous components of the self-energy matrix are calculated in the self-consistent Born approximation for the electron-spin-fluctuation scattering mediated by kinematic interaction of the second order of the intraband hopping. The derived numerical and analytical solutions predict the occurrence of singlet d x 2 -y 2 -wave pairing both in the d-hole and singlet Hubbard subbands. The gap functions and T c are calculated for different hole concentrations. The exchange interaction is shown to be the most important pairing interaction in the Hubbard model in the strong correlation limit, while the spin-fluctuation coupling results only in a moderate enhancement of T c . The smaller weight of the latter comes from two specific features: its vanishing inside the Brillouin zone (BZ) along the lines, |k x | + |k y |=π pointing towards the hot spots and the existence of a small energy shell within which the pairing is effective. By
Reaction mechanism and nuclear correlations study by low energy pion double charge exchange
International Nuclear Information System (INIS)
Weinfeld, Z.
1993-06-01
In pion double-charge-exchange (DCX) reactions, a positive (negative) pion is incident on a nucleus and a negative (positive) pion emerges. These reactions are of fundamental interest since the process must involve at least two nucleons in order to conserve charge. Although two nucleon processes are present in many reactions they are usually masked by the dominant single nucleon processes. DCX is unique in that respect since it is a two nucleon process in lowest order and thus may be sensitive to two-nucleon correlations. Measurements of low energy pion double-charge-exchange reactions to the double-isobaric-analog-state (DIAS) and ground-state (GS) of the residual nucleus provide new means for studying nucleon-nucleon correlations in nuclei. At low energies (T π 7/2 shell at energies ranging from 25 to 65 MeV. Cross sections were measured on 42,44,48 Ca, 46,50 Ti and 54 Fe. The calcium isotopes make a good set of nuclei on which to study the effects of correlations in DCX reactions
Statistical modelling of citation exchange between statistics journals.
Varin, Cristiano; Cattelan, Manuela; Firth, David
2016-01-01
Rankings of scholarly journals based on citation data are often met with scepticism by the scientific community. Part of the scepticism is due to disparity between the common perception of journals' prestige and their ranking based on citation counts. A more serious concern is the inappropriate use of journal rankings to evaluate the scientific influence of researchers. The paper focuses on analysis of the table of cross-citations among a selection of statistics journals. Data are collected from the Web of Science database published by Thomson Reuters. Our results suggest that modelling the exchange of citations between journals is useful to highlight the most prestigious journals, but also that journal citation data are characterized by considerable heterogeneity, which needs to be properly summarized. Inferential conclusions require care to avoid potential overinterpretation of insignificant differences between journal ratings. Comparison with published ratings of institutions from the UK's research assessment exercise shows strong correlation at aggregate level between assessed research quality and journal citation 'export scores' within the discipline of statistics.
Bayesian analysis for exponential random graph models using the adaptive exchange sampler
Jin, Ick Hoon
2013-01-01
Exponential random graph models have been widely used in social network analysis. However, these models are extremely difficult to handle from a statistical viewpoint, because of the existence of intractable normalizing constants. In this paper, we consider a fully Bayesian analysis for exponential random graph models using the adaptive exchange sampler, which solves the issue of intractable normalizing constants encountered in Markov chain Monte Carlo (MCMC) simulations. The adaptive exchange sampler can be viewed as a MCMC extension of the exchange algorithm, and it generates auxiliary networks via an importance sampling procedure from an auxiliary Markov chain running in parallel. The convergence of this algorithm is established under mild conditions. The adaptive exchange sampler is illustrated using a few social networks, including the Florentine business network, molecule synthetic network, and dolphins network. The results indicate that the adaptive exchange algorithm can produce more accurate estimates than approximate exchange algorithms, while maintaining the same computational efficiency.
Directory of Open Access Journals (Sweden)
Predrag Petrović
2013-04-01
Full Text Available The focus of this research holds the most important determinants of real exchange rate covered by various theoretical models. The empirical testing was carried out on the real exchange rate between RSD and Euro for the period from January 2007 to December 2010, which was significantly imposed by availability of consistent time series. The research pertains to five basic model specifications and is based on the testing of time series cointegration by applying Johansen and Engle-Granger’s test. The obtained results have shown that the observed models do not have grounds in empirical data. Time series figuring in models are not cointegrated, and besides that, the estimated cointegration coefficients have signs opposite to the expected ones in large number of cases. In our opinion, the reasons for such findings can be found in the fact that used time series are quite short, i.e. they pertain to the period of only four years, as well as that prices of some significant services are still under the administrative control. Still, despite the aforementioned lacks, we think that our findings can be accepted as preliminary knowledge about the ability of the observed models to explain the dynamics of real exchange rate between RSD and Euro.
Modelling distributed energy resources in energy service networks
Acha, Salvador
2013-01-01
Focuses on modelling two key infrastructures (natural gas and electrical) in urban energy systems with embedded technologies (cogeneration and electric vehicles) to optimise the operation of natural gas and electrical infrastructures under the presence of distributed energy resources
Energy Technology Data Exchange (ETDEWEB)
Danilo Dragoni; Hans Peter Schmid; C.S.B. Grimmond; J.C. Randolph; J.R. White
2012-12-17
During the project period we continued to conduct long-term (multi-year) measurements, analysis, and modeling of energy and mass exchange in and over a deciduous forest in the Midwestern United States, to enhance the understanding of soil-vegetation-atmosphere exchange of carbon. At the time when this report was prepared, results from nine years of measurements (1998 - 2006) of above canopy CO2 and energy fluxes at the AmeriFlux site in the Morgan-Monroe State Forest, Indiana, USA (see Table 1), were available on the Fluxnet database, and the hourly CO2 fluxes for 2007 are presented here (see Figure 1). The annual sequestration of atmospheric carbon by the forest is determined to be between 240 and 420 g C m-2 a-1 for the first ten years. These estimates are based on eddy covariance measurements above the forest, with a gap-filling scheme based on soil temperature and photosynthetically active radiation. Data gaps result from missing data or measurements that were rejected in qua)lity control (e.g., during calm nights). Complementary measurements of ecological variables (i.e. inventory method), provided an alternative method to quantify net carbon uptake by the forest, partition carbon allocation in each ecosystem components, and reduce uncertainty on annual net ecosystem productivity (NEP). Biometric datasets are available on the Fluxnext database since 1998 (with the exclusion of 2006). Analysis for year 2007 is under completion.
Land-use change arising from rural land exchange : an agent-based simulation model
Bakker, Martha M.; Alam, Shah Jamal; van Dijk, Jerry; Rounsevell, Mark D. A.
Land exchange can be a major factor driving land-use change in regions with high pressure on land, but is generally not incorporated in land-use change models. Here we present an agent-based model to simulate land-use change arising from land exchange between multiple agent types representing
Value-exchange patterns in business models of intermediaries that offer negotiation services
Zlatev, Z.V.; van Eck, Pascal; Wieringa, Roelf J.
This document is a library of value-exchange patterns. A value-exchange pattern is a repeatedly occurring fragment in value-based business models. The collection is drawn out of business models of market intermediaries that offer negotiation services. The intermediaries are selected as a result of
Directory of Open Access Journals (Sweden)
A. O. Sulym
2017-10-01
Full Text Available Purpose. The analysis of the existing studies showed that the increasing of energy efficiency of metro rolling stock becomes especially important and requires timely solutions. It is known that the implementation of regenerative braking systems on rolling stock will allow significantly solving this problem. It was proved that one of the key issues regarding the introduction of the above-mentioned systems is research on efficient use of electric energy of regenerative braking. The purpose of the work is to evaluate the amount of excessive electric power of regenerative braking under normal operation conditions of the rolling stock with regenerative braking systems for the analysis of the energy saving reserves. Methodology. Quantifiable values of electrical energy consumed for traction, returned to the contact line and dissipated in braking resistors (excessive energy are determined using results of experimental studies of energy exchange processes under normal operating conditions of metro rolling stock with regenerative systems. Statistical methods of data processing were applied as well. Findings. Results of the studies analysis of metro rolling stock operation under specified conditions in Sviatoshinsko-Brovarskaia line of KP «Kyiv Metro system» stipulate the following: 1 introduction of regenerative braking systems into the rolling stock allows to return about 17.9-23.2% of electrical energy consumed for traction to the contact line; 2 there are reserves for improving of energy efficiency of rolling stock with regenerative systems at the level of 20.2–29.9 % of electrical energy consumed for traction. Originality. For the first time, it is proved that the most significant factor that influences the quantifiable values of the electrical energy regeneration is a track profile. It is suggested to use coefficients which indicate the amount and reserves of unused (excessive electrical energy for quantitative evaluation. Studies on
A General Model for Cost Estimation in an Exchange
Directory of Open Access Journals (Sweden)
Benzion Barlev
2014-03-01
Full Text Available Current Generally Accepted Accounting Principles (GAAP state that the cost of an asset acquired for cash is the fair value (FV of the amount surrendered, and that of an asset acquired in a non-monetary exchange is the FV of the asset surrendered or, if it is more “clearly evident,” the FV of the acquired asset. The measurement method prescribed for a non-monetary exchange ignores valuable information about the “less clearly evident” asset. Thus, we suggest that the FV in any exchange be measured by the weighted average of the exchanged assets’ FV estimations, where the weights are the inverse of the variances’ estimations. This alternative valuation process accounts for the uncertainty involved in estimating the FV of each of the asset in the exchange. The proposed method suits all types of exchanges: monetary and non-monetary. In a monetary transaction, the weighted average equals the cash paid because the variance of its FV is nil.
Universal model for water costs of gas exchange by animals and plants.
Woods, H Arthur; Smith, Jennifer N
2010-05-04
For terrestrial animals and plants, a fundamental cost of living is water vapor lost to the atmosphere during exchange of metabolic gases. Here, by bringing together previously developed models for specific taxa, we integrate properties common to all terrestrial gas exchangers into a universal model of water loss. The model predicts that water loss scales to gas exchange with an exponent of 1 and that the amount of water lost per unit of gas exchanged depends on several factors: the surface temperature of the respiratory system near the outside of the organism, the gas consumed (oxygen or carbon dioxide), the steepness of the gradients for gas and vapor, and the transport mode (convective or diffusive). Model predictions were largely confirmed by data on 202 species in five taxa--insects, birds, bird eggs, mammals, and plants--spanning nine orders of magnitude in rate of gas exchange. Discrepancies between model predictions and data seemed to arise from biologically interesting violations of model assumptions, which emphasizes how poorly we understand gas exchange in some taxa. The universal model provides a unified conceptual framework for analyzing exchange-associated water losses across taxa with radically different metabolic and exchange systems.
Numerical calibration and experimental validation of a PCM-Air heat exchanger model
International Nuclear Information System (INIS)
Stathopoulos, N.; El Mankibi, M.; Santamouris, Mattheos
2017-01-01
Highlights: • Development of a PCM-Air heat exchanger experimental unit and its numerical model. • Differential Scanning Calorimetry for PCM properties. • Ineptitude of DSC obtained heat capacity curves. • Creation of adequate heat capacity curves depending on heat transfer rates. • Confrontation of numerical and experimental results and validation of the model. - Abstract: Ambitious goals have been set at international, European and French level for energy consumption and greenhouse gas emissions decrease of the building sector. Achieving them requires renewable energy integration, a technology that presents however an important drawback: intermittent energy production. In response, thermal energy storage (TES) technology applications have been developed in order to correlate energy production and consumption of the building. Phase Change Materials (PCMs) have been widely used in TES applications as they offer a high storage density and adequate phase change temperature range. It is important to accurately know the thermophysical properties of the PCM, both for experimental (system design) and numerical (correct prediction) purposes. In this paper, the fabrication of a PCM – Air experimental prototype is presented at first, along with the development of a numerical model simulating the downstream temperature evolution of the heat exchanger. Particular focus is given to the calibration method and the validation of the model using experimental characterization results. Differential scanning calorimetry (DSC) is used to define the thermal properties of the PCM. Initial numerical results are underestimated compared to experimental ones. Various factors were investigated, pointing to the ineptitude of the heat capacity parameter, as DSC results depend on heating/cooling rates. Adequate heat capacity curves were empirically determined, depending on heat transfer rates and based on DSC results and experimental observations. The results of the proposed model
Koon, Norman C.
1997-04-01
It is shown using full micromagnetic relaxation calculations that exchange bias behavior is predicted for single-crystal ferro/antiferromagnetic layers with a fully compensated interface. The particular example most fully studied has a bcc/bct lattice structure with a fully compensated (110) interface plane. Only bilinear Heisenberg exchange was assumed, with anisotropy only in the antiferromagnet. In spite of the intuitive notion that exchange coupling between a ferromagnet and an antiferromagnet across a fully compensated plane of the antiferromagnet should be zero, we find strong coupling, comparable to the bilinear exchange, with a 90° angle between the ferromagnetic and antiferromagnetic axes of layers far from the interface in absence of an applied field. Even though the 90° coupling has characteristics resembling "biquadratic" exchange, it originates entirely from frustrated bilinear exchange. The development of exchange bias is found to originate from the formation of a domain wall in the antiferromagnet via the strong 90° exchange coupling and pinning of the wall by the magnetocrystalline anisotropy in the antiferromagnet. Because the large demagnetizing factor of the ferromagnet tends to confine its magnetization to the plane, the exchange bias is found to depend mainly on the strength and the symmetry of the in-plane component of anisotropy. Although little effort was made to analyze specific systems, the model reproduces many of the qualitative features observed in real exchange bias systems and gives reasonable semiquantitative estimates for the bias field when exchange and anisotropy values consistent with real systems are used.
Conference on new consumption and commercialization models for photovoltaic energy
International Nuclear Information System (INIS)
Freier, Karin; Fontaine, Pierre; Mayer, Joerg; Jimenez, Julien; Richard, Pascal; Vogtmann, Michael; Schaefer, Felix; Martin, Nicolas; Buis, Sabine
2014-01-01
The French-German office for Renewable energies (OFAEnR) organised a conference on new consumption and commercialization models for photovoltaic energy. In the framework of this French-German exchange of experience, about 120 participants exchanged views on the new economic models for solar energy producers while the photovoltaic industry has to face a progressive reduction of feed-in tariffs and of other incentive mechanisms. Beside the legal and economic aspects, technical questions around energy storage and integration of photovoltaic production to the grid were also addressed. This document brings together the available presentations (slides) made during this event: 1 - Stimulating self-consumption and direct selling within the EEG (Karin Freier); 2 - Development of PV self-consumption in France (Pierre Fontaine); 3 - experience from applying the new support program for solar energy storage systems (Joerg Mayer); 4 - Call for solar photovoltaic projects for own consumption in Aquitaine region (Julien Jimenez); 5 - SMA Flexible Storage System - New version of the Sunny Island inverter for smart photovoltaic energy storage (Pascal Richard); 6 - PV Own Consumption in industry and commerce - examples und Operating Concepts (Michael Vogtmann); 7 - Supplying tenants in multiple-family housing with solar power in the 'Neue Heimat' project (Felix Schaefer); 8 - How to manage PV-storage self-consumption from a grid point of view? (Nicolas Martin); 9 - Closing talk (Sabine Buis)
Two sustainable energy system analysis models
DEFF Research Database (Denmark)
Lund, Henrik; Goran Krajacic, Neven Duic; da Graca Carvalho, Maria
2005-01-01
This paper presents a comparative study of two energy system analysis models both designed with the purpose of analysing electricity systems with a substantial share of fluctuating renewable energy.......This paper presents a comparative study of two energy system analysis models both designed with the purpose of analysing electricity systems with a substantial share of fluctuating renewable energy....
Derivation of the tunnelling exchange time for the model of trap-assisted tunnelling
International Nuclear Information System (INIS)
Racko, J.; Ballo, P.; Benko, P.; Harmatha, L.; Grmanova, A.; Breza, J.
2014-01-01
We present derivation of the tunnelling exchange times that play the key role in the model of trap assisted tunnelling (TAT) considering the electron and hole exchange processes between the trapping centre lying in the forbidden band of the semiconductor and the conduction band, valence band or a metal. All exchange processes are quantitatively described by respective exchange times. The reciprocal values of these exchange times represent the frequency with which the exchange processes contribute to the probability of occupation of the trap by free charge carriers. The crucial problem in any model of TAT is the calculation of the occupation probability. In our approach this probability is expressed in terms of only thermal and tunnelling exchange times. The concept of tunnelling exchange times presents a dominant contribution to our model of TAT. The new approach allows to simply calculate the probability of occupation of the trapping centre by a free charge carrier and subsequently to get the thermal and tunnelling generation-recombination rates occurring in the continuity equations. This is why the TAT model based on thermal and tunnelling exchange times is suitable for simulating the electrical properties of semiconductor nanostructures in which quantum mechanical phenomena play a key role. (authors)
DEFF Research Database (Denmark)
Shrestha, Pravin Malla; Rotaru, Amelia-Elena; Aklujkar, Muktak
2013-01-01
Direct interspecies electron transfer (DIET) through biological electrical connections is an alternative to interspecies H2 transfer as a mechanism for electron exchange in syntrophic cultures. However, it has not previously been determined whether electrons received via DIET yield energy....... The lack of acetate metabolism resulted in less fumarate reduction and lower cell abundance of G. sulfurreducens. RNAseq analysis of transcript abundance was consistent with a lack of acetate metabolism in G. sulfurreducens and revealed gene expression levels for the uptake hydrogenase, formate...... dehydrogenase, the pilus-associated c-type cytochrome OmcS and pili consistent with electron transfer via DIET. These results suggest that electrons transferred via DIET can serve as the sole energy source to support anaerobic respiration....
Energy Blocks — A Physical Model for Teaching Energy Concepts
Hertting, Scott
2016-01-01
Most physics educators would agree that energy is a very useful, albeit abstract topic. It is therefore important to use various methods to help the student internalize the concept of energy itself and its related ideas. These methods include using representations such as energy bar graphs, energy pie charts, or energy tracking diagrams. Activities and analogies like Energy Theater and Richard Feynman's blocks, as well as the popular money (or wealth) analogy, can also be very effective. The goal of this paper is to describe a physical model of Feynman's blocks that can be employed by instructors to help students learn the following energy-related concepts: 1. The factors affecting each individual mechanical energy storage mode (this refers to what has been traditionally called a form of energy, and while the Modeling Method of instruction is not the focus of this paper, much of the energy related language used is specific to the Modeling Method). For example, how mass or height affects gravitational energy; 2. Energy conservation; and 3. The graphical relationships between the energy storage mode and a factor affecting it. For example, the graphical relationship between elastic energy and the change in length of a spring.
Charge exchange during pion-nucleon scattering at low energy: experiment and analysis
International Nuclear Information System (INIS)
Vernin, Pascal
1972-01-01
This research thesis lies within the frame of a more general study of pion-nucleon scattering according to the following processes: π + p → π + p; π - p → π - p; π - p → π 0 n. It more precisely addresses the last reaction, so-called charge exchange. Pion-nucleon interactions are described by phase shifts of scattering waves. But the measurement of one of these phase shifts (that of the S wave) requires very low energy pions, and could not have been performed until now with a good precision. In order to fill this gap, the author performed charge exchange experiments at 180 deg. and for energies of 22.6, 33.9 and 42.6 MeV. After a recall on involved theoretical data, the author describes the experimental setup, and reports the detailed study of problems raised by neutron detection. He shows that the analysis of experimental data allows (a 3 - a 1 ) to be obtained with a precision which, without being as high as desired, is nevertheless satisfying [fr
Extreme nonlinear energy exchanges in a geometrically nonlinear lattice oscillating in the plane
Zhang, Zhen; Manevitch, Leonid I.; Smirnov, Valeri; Bergman, Lawrence A.; Vakakis, Alexander F.
2018-01-01
We study the in-plane damped oscillations of a finite lattice of particles coupled by linear springs under distributed harmonic excitation. Strong nonlinearity in this system is generated by geometric effects due to the in-plane stretching of the coupling spring elements. The lattice has a finite number of nonlinear transverse standing waves (termed nonlinear normal modes - NNMs), and an equal number of axial linear modes which are nonlinearly coupled to the transverse ones. Nonlinear interactions between the transverse and axial modes under harmonic excitation give rise to unexpected and extreme nonlinear energy exchanges in the lattice. In particular, we directly excite a transverse NNM by harmonic forcing (causing simulataneous indirect excitation of a corresponding axial linear mode due to nonlinear coupling), and identify three energy transfer mechanisms in the lattice. First, we detect the stable response of the directly excited transverse NNM (despite its instability in the absence of forcing), with simultaneous stability of the indirectly excited axial linear mode. Second, by changing the system and forcing parameters we report extreme nonlinear "energy explosions," whereby, after an initial regime of stability, the directly excited transverse NNM loses stability, leading to abrupt excitation of all transverse and axial modes of the lattice, at all possible wave numbers. This strong instability is triggered by the parametric instability of an indirectly excited axial mode which builds energy until the explosion. This is proved through theoretical analysis. Finally, in other parameter ranges we report intermittent, intense energy transfers from the directly excited transverse NNM to a small set of transverse NNMs with smaller wavelengths, and from the indirectly excited axial mode to a small set of axial modes, but with larger wavelengths. These intermittent energy transfers resemble energy cascades occurring in turbulent flows. Our results show that
Model Based Controller Design for a Shell and Tube Heat Exchanger
Directory of Open Access Journals (Sweden)
S. Nithya
2007-10-01
Full Text Available In all the process industries the process variables like flow, pressure, level and temperature are the main parameters that need to be controlled in both set point and load changes. The transfer of heat is one of the main important operation in the heat exchanger .The transfer of heat may be fluid to fluid, gas to gas i.e. in the same phase or the phase change can occur on either side of the heat exchanger. The control of heat exchanger is complex due to its nonlinear dynamics. For this nonlinear process of a heat exchanger the model is identified to be First Order plus Dead Time (FOPDT.The Internal Model Control (IMC is one of the model predictive control methods based on the predictive output of the process model. The conventional controller tuning is compared with IMC techniques and it found to be suitable for heat exchanger than the conventional PI tuning.
Modelling bidirectional fluxes of methanol and acetaldehyde with the FORCAsT canopy exchange model
Directory of Open Access Journals (Sweden)
K. Ashworth
2016-12-01
Full Text Available The FORCAsT canopy exchange model was used to investigate the underlying mechanisms governing foliage emissions of methanol and acetaldehyde, two short chain oxygenated volatile organic compounds ubiquitous in the troposphere and known to have strong biogenic sources, at a northern mid-latitude forest site. The explicit representation of the vegetation canopy within the model allowed us to test the hypothesis that stomatal conductance regulates emissions of these compounds to an extent that its influence is observable at the ecosystem scale, a process not currently considered in regional- or global-scale atmospheric chemistry models.We found that FORCAsT could only reproduce the magnitude and diurnal profiles of methanol and acetaldehyde fluxes measured at the top of the forest canopy at Harvard Forest if light-dependent emissions were introduced to the model. With the inclusion of such emissions, FORCAsT was able to successfully simulate the observed bidirectional exchange of methanol and acetaldehyde. Although we found evidence that stomatal conductance influences methanol fluxes and concentrations at scales beyond the leaf level, particularly at dawn and dusk, we were able to adequately capture ecosystem exchange without the addition of stomatal control to the standard parameterisations of foliage emissions, suggesting that ecosystem fluxes can be well enough represented by the emissions models currently used.
Directory of Open Access Journals (Sweden)
G. M. Wolfe
2011-01-01
Full Text Available We present the Chemistry of Atmosphere-Forest Exchange (CAFE model, a vertically-resolved 1-D chemical transport model designed to probe the details of near-surface reactive gas exchange. CAFE integrates all key processes, including turbulent diffusion, emission, deposition and chemistry, throughout the forest canopy and mixed layer. CAFE utilizes the Master Chemical Mechanism (MCM and is the first model of its kind to incorporate a suite of reactions for the oxidation of monoterpenes and sesquiterpenes, providing a more comprehensive description of the oxidative chemistry occurring within and above the forest. We use CAFE to simulate a young Ponderosa pine forest in the Sierra Nevada, CA. Utilizing meteorological constraints from the BEARPEX-2007 field campaign, we assess the sensitivity of modeled fluxes to parameterizations of diffusion, laminar sublayer resistance and radiation extinction. To characterize the general chemical environment of this forest, we also present modeled mixing ratio profiles of biogenic hydrocarbons, hydrogen oxides and reactive nitrogen. The vertical profiles of these species demonstrate a range of structures and gradients that reflect the interplay of physical and chemical processes within the forest canopy, which can influence net exchange.
Global energy modeling - A biophysical approach
Energy Technology Data Exchange (ETDEWEB)
Dale, Michael
2010-09-15
This paper contrasts the standard economic approach to energy modelling with energy models using a biophysical approach. Neither of these approaches includes changing energy-returns-on-investment (EROI) due to declining resource quality or the capital intensive nature of renewable energy sources. Both of these factors will become increasingly important in the future. An extension to the biophysical approach is outlined which encompasses a dynamic EROI function that explicitly incorporates technological learning. The model is used to explore several scenarios of long-term future energy supply especially concerning the global transition to renewable energy sources in the quest for a sustainable energy system.
International Nuclear Information System (INIS)
Rehman, Nasir; Shashiashvili, Malkhaz
2009-01-01
The classical Garman-Kohlhagen model for the currency exchange assumes that the domestic and foreign currency risk-free interest rates are constant and the exchange rate follows a log-normal diffusion process.In this paper we consider the general case, when exchange rate evolves according to arbitrary one-dimensional diffusion process with local volatility that is the function of time and the current exchange rate and where the domestic and foreign currency risk-free interest rates may be arbitrary continuous functions of time. First non-trivial problem we encounter in time-dependent case is the continuity in time argument of the value function of the American put option and the regularity properties of the optimal exercise boundary. We establish these properties based on systematic use of the monotonicity in volatility for the value functions of the American as well as European options with convex payoffs together with the Dynamic Programming Principle and we obtain certain type of comparison result for the value functions and corresponding exercise boundaries for the American puts with different strikes, maturities and volatilities.Starting from the latter fact that the optimal exercise boundary curve is left continuous with right-hand limits we give a mathematically rigorous and transparent derivation of the significant early exercise premium representation for the value function of the American foreign exchange put option as the sum of the European put option value function and the early exercise premium.The proof essentially relies on the particular property of the stochastic integral with respect to arbitrary continuous semimartingale over the predictable subsets of its zeros. We derive from the latter the nonlinear integral equation for the optimal exercise boundary which can be studied by numerical methods
International Nuclear Information System (INIS)
Demichev, A.; Kryukov, A.; Rodionov, A.
2002-01-01
We propose an XML-based standard for formulation of field theoretical models. The goal of creation of such a standard is to provide a way for an unambiguous exchange and cross-checking of results of computer calculations in high energy physics. At the moment, the suggested standard implies that models under consideration are of the SM or MSSM type (i.e., they are just SM or MSSM, their submodels, smooth modifications or straightforward generalizations). (author)
Sugiyanto; Wibowo, Supriyadi; Rizky Aristina Suwardi, Vivi
2017-12-01
The severity of the financial crisis that occurred in Indonesia required an early warning system of financial crisis. The financial crisis in Indonesia can be detected based on imports, exports, and foreign exchange reserves. The purpose of the research is to determine an appropriate model to detect the financial crisis in Indonesia based on imports, exports, and foreign exchange reserves. Markov switching is an alternative framework for the approach often used in financial crisis detection. Combined volatility and Markov switching model with three states assumptions can be established if an AR and volatility models have been obtained. Imports, exports, and foreign exchange reserves data from January 1990 to December 2016 have the heteroscedasticity effect so that an ARCH model is used as a volatility model. Research shows that SWARCH(3.1) model is an appropriate model for detecting financial crisis in Indonesia based on imports, exports, and foreign exchange reserves.
Economic modelling of energy services: Rectifying misspecified energy demand functions
International Nuclear Information System (INIS)
Hunt, Lester C.; Ryan, David L.
2015-01-01
Although it is well known that energy demand is derived, since energy is required not for its own sake but for the energy services it produces – such as heating, lighting, and motive power – energy demand models, both theoretical and empirical, often fail to take account of this feature. In this paper, we highlight the misspecification that results from ignoring this aspect, and its empirical implications – biased estimates of price elasticities and other measures – and provide a relatively simple and empirically practicable way to rectify it, which has a strong theoretical grounding. To do so, we develop an explicit model of consumer behaviour in which utility derives from consumption of energy services rather than from the energy sources that are used to produce them. As we discuss, this approach opens up the possibility of examining many aspects of energy demand in a theoretically sound way that have not previously been considered on a widespread basis, although some existing empirical work could be interpreted as being consistent with this type of specification. While this formulation yields demand equations for energy services rather than for energy or particular energy sources, these are shown to be readily converted, without added complexity, into the standard type of energy demand equation(s) that is (are) typically estimated. The additional terms that the resulting energy demand equations include, compared to those that are typically estimated, highlight the misspecification that is implicit when typical energy demand equations are estimated. A simple solution for dealing with an apparent drawback of this formulation for empirical purposes, namely that information is required on typically unobserved energy efficiency, indicates how energy efficiency can be captured in the model, such as by including exogenous trends and/or including its possible dependence on past energy prices. The approach is illustrated using an empirical example that involves
Energy technologies and energy efficiency in economic modelling
DEFF Research Database (Denmark)
Klinge Jacobsen, Henrik
1998-01-01
This paper discusses different approaches to incorporating energy technologies and technological development in energy-economic models. Technological development is a very important issue in long-term energy demand projections and in environmental analyses. Different assumptions on technological...... technological development. This paper examines the effect on aggregate energy efficiency of using technological models to describe a number of specific technologies and of incorporating these models in an economic model. Different effects from the technology representation are illustrated. Vintage effects...... illustrates the dependence of average efficiencies and productivity on capacity utilisation rates. In the long run regulation induced by environmental policies are also very important for the improvement of aggregate energy efficiency in the energy supply sector. A Danish policy to increase the share...
DFT-SAPT intermolecular interaction energies employing exact-exchange Kohn-Sham response methods.
Hesselmann, Andreas
2018-03-22
Intermolecular interaction energies have been calculated by symmetry-adapted perturbation theory based on density-functional theory monomer properties (DFT-SAPT) employing response functions from time-dependent exact-exchange (TDEXX) kernels. Combined with a new asymptotic correction scheme for the xc potentials of the monomers, it is shown that this DFT-SAPT[TDEXX] method delivers highly accurate intermolecular interaction energies for the S22, S66 and IonHB benchmark data bases by Hobza et al.. A corresponding DFT-SAPT approach employing the adiabatic TDEXX kernel in the response calculations has also been tested. While exhibiting a similar performance than DFT-SAPT[TDEXX] for dispersion-dominated dimer systems, it was found found that the accuracies of the interaction energies for hydrogen-bonded dimers deteriorate with this DFT-SAPT[ATDEXX] method. Compared to this, the DFT-SAPT[TDEXX] yields a balanced description of the interaction energies for various interaction-type motifs, similar to the standard DFT-SAPT method that utilises the ALDA xc kernel to compute the response functions.
Application of models for exchange of electronic documents in complex administrative services
Glavev, Victor
2015-11-01
The report presents application of models for exchange of electronic documents between different administrations in government and business sectors. It shows the benefits of implementing electronic exchange of documents between different local offices of one administration in government sector such as a municipality and the way it is useful for implementing complex administrative services.
A Model for Trading the Foreign Exchange Market | Nwokorie | West ...
African Journals Online (AJOL)
The electronic Foreign Exchange (FOREX) market where currencies are bought and sold has become more complex and dynamic with characteristics of high volatility, nonlinearity, and irregularity. Some important factors such as economic growth, trade development, interest rates, inflation rates, etc. have significant impacts ...
Process Model for Studying Regional 13C Stable Isotope Exchange between Vegetation and Atmosphere
Chen, J. M.; Chen, B.; Huang, L.; Tans, P.; Worthy, D.; Ishizawa, M.; Chan, D.
2007-12-01
The variation of the stable isotope 13CO2 in the air in exchange with land ecosystems results from fractionation processes in both plants and soil during photosynthesis and respiration. Its diurnal and seasonal variations therefore contain information on the carbon cycle. We developed a model (BEPS-iso) to simulate its exchange between vegetation and the atmosphere. To be useful for regional carbon cycle studies, the model has the following characteristics: (i) it considers the turbulent mixing in the vertical profile from the soil surface to the top of the planetary boundary layer (PBL); (ii) it scales individual leaf photosynthetic discrimination to the whole canopy through the separation of sunlit and shaded leaf groups; (iii) through simulating leaf-level photosynthetic processes, it has the capacity to mechanistically examine isotope discrimination resulting from meteorological forcings, such as radiation, precipitation and humidity; and (iv) through complete modeling of radiation, energy and water fluxes, it also simulates soil moisture and temperature needed for estimating ecosystem respiration and the 13C signal from the soil. After validation using flask data acquired at 20 m level on a tower near Fraserdale, Ontario, Canada, during intensive campaigns (1998-2000), the model has been used for several purposes: (i) to investigate the diurnal and seasonal variations in the disequilibrium in 13C fractionation between ecosystem respiration and photosynthesis, which is an important step in using 13C measurements to separate these carbon cycle components; (ii) to quantify the 13C rectification in the PBL, which differs significantly from CO2 rectification because of the diurnal and seasonal disequilibriums; and (iii) to model the 13C spatial and temporal variations over the global land surface for the purpose of CO2 inversion using 13C as an additional constraint.
Models of Energy Saving Systems
DEFF Research Database (Denmark)
Nørgård, Jørgen Stig
1999-01-01
The paper first describes the concepts and methods around energy saving, such as energy chain, energy services, end-use technologies, secondary energy, etc. Next are discussed the problems of defining and adding energy services and hence end-use energy efficiency or intensity. A section is devoted...... to what is termed lifestyle efficiency, including the cultural values and the ability of the economy to provide the services wanted. As explained, integrated resource planning with its optimizing the whole energy chain cannot be combined with sub-optimizing part of it, for instance the supply technology...... only. The need for including also the economic policy in the energy planning is illustrated with what is termed the efficiency pittfall. This points towards difficulties in imaging an integrated resource planning combined with a liberalized market. The three variable parameters, population, energy...
Directory of Open Access Journals (Sweden)
Dinh An Nguyen
2012-07-01
Full Text Available Many of the Proton Exchange Membrane Fuel Cell (PEMFC models proposed in the literature consist of mathematical equations. However, they are not adequately practical for simulating power systems. The proposed model takes into account phenomena such as activation polarization, ohmic polarization, double layer capacitance and mass transport effects present in a PEM fuel cell. Using electrical analogies and a mathematical modeling of PEMFC, the circuit model is established. To evaluate the effectiveness of the circuit model, its static and dynamic performances under load step changes are simulated and compared to the numerical results obtained by solving the mathematical model. Finally, the applicability of our model is demonstrated by simulating a practical system.
Directory of Open Access Journals (Sweden)
Xun Yang
2017-08-01
Full Text Available In this study, the dynamic melting process of the phase change material (PCM in a vertical cylindrical tube-in-tank thermal energy storage (TES unit was investigated through numerical simulations and experimental measurements. To ensure good heat exchange performance, a concentric helical coil was inserted into the TES unit to pipe the heat transfer fluid (HTF. A numerical model using the computational fluid dynamics (CFD approach was developed based on the enthalpy-porosity method to simulate the unsteady melting process including temperature and liquid fraction variations. Temperature measurements using evenly spaced thermocouples were conducted, and the temperature variation at three locations inside the TES unit was recorded. The effects of the HTF inlet parameters were investigated by parametric studies with different temperatures and flow rate values. Reasonably good agreement was achieved between the numerical prediction and the temperature measurement, which confirmed the numerical simulation accuracy. The numerical results showed the significance of buoyancy effect for the dynamic melting process. The system TES performance was very sensitive to the HTF inlet temperature. By contrast, no apparent influences can be found when changing the HTF flow rates. This study provides a comprehensive solution to investigate the heat exchange process of the TES system using PCM.
Kodra, Evan; Sheldon, Seth; Dolen, Ryan; Zik, Ory
2015-11-17
Using a complex network framework, the North American electric grid is modeled as a dynamic, equilibrium-based supply chain of more than 100 interconnected power control areas (PCAs) in the contiguous United States, Canada, and Northern Mexico. Monthly generation and yearly inter-PCA exchange data reported by PCAs are used to estimate a directed network topology. Variables including electricity, as well as primary fuels, technologies, and greenhouse gas emissions associated with power generation can be traced through the network, providing energy source composition statistics for power consumers at a given location. Results show opportunities for more precise measurement by consumers of emissions occurring on their behalf at power plants. Specifically, we show a larger range of possible factors (∼0 to 1.3 kgCO2/kWh) as compared to the range provided by the EPA's eGRID analysis (∼0.4 to 1 kgCO2/kWh). We also show that 66-73% of the variance in PCA-level estimated emissions savings is the result of PCA-to-PCA differences that are not captured by the larger eGRID subregions. The increased precision could bolster development of effective greenhouse gas reporting and mitigation policies. This study also highlights the need for improvements in the consistency and spatiotemporal resolution of PCA-level generation and exchange data reporting.
Decoupled dirac equation in one-boson-Exchange potential model and Hartree-fock calculations
International Nuclear Information System (INIS)
Hanna, K.M.; Swelam, Sh.M.; Nafea, H.O.
2004-01-01
On the basis of a semi-relativistic decoupled Dirac equation and self consistent Hartree-Fock formulation, it is used the One-Boson-Exchange Potential (OBEP) model where each nucleon, as a Dirac particle, is considered to be a source of a scalar (a) and vector (co) fields, and is also acted upon by these fields, to get the ground state of some spherical nuclei. An important mathematical advantage gained by the assumption that each nucleon in the nucleus is moving under the influence of a common harmonic oscillator is that (as shown by Talmi) the wave function of the two nucleons is separable in their relative and center of mass (C.M) coordinates and the known Talmi-Moshinsky brackets. Three different static nucleon-nucleon interaction forms are used to predict the ground state energy for 4 He nucleus
Rapid Energy Modeling Workflow Demonstration Project
2014-01-01
Conditioning Engineers BIM Building Information Model BLCC building life cycle costs BPA Building Performance Analysis CAD computer assisted...utilizes information on operations, geometry, orientation, weather, and materials, generating Three-Dimensional (3D) Building Information Models ( BIM ...executed a demonstration of Rapid Energy Modeling (REM) workflows that employed building information modeling ( BIM ) approaches and conceptual energy
Three-dimensional modeling of radiative and convective exchanges in the urban atmosphere
International Nuclear Information System (INIS)
Qu, Yongfeng
2011-01-01
In many micro-meteorological studies, building resolving models usually assume a neutral atmosphere. Nevertheless, urban radiative transfers play an important role because of their influence on the energy budget. In order to take into account atmospheric radiation and the thermal effects of the buildings in simulations of atmospheric flow and pollutant dispersion in urban areas, we have developed a three-dimensional (3D) atmospheric radiative scheme, in the atmospheric module of the Computational Fluid Dynamics model Code-Saturne. The radiative scheme was previously validated with idealized cases, using as a first step, a constant 3D wind field. In this work, the full coupling of the radiative and thermal schemes with the dynamical model is evaluated. The aim of the first part is to validate the full coupling with the measurements of the simple geometry from the 'Mock Urban Setting Test' (MUST) experiment. The second part discusses two different approaches to model the radiative exchanges in urban area with a comparison between Code-Saturne and SOLENE. The third part applies the full coupling scheme to show the contribution of the radiative transfer model on the airflow pattern in low wind speed conditions in a 3D urban canopy. In the last part we use the radiative-dynamics coupling to simulate a real urban environment and validate the modeling approach with field measurements from the 'Canopy and Aerosol Particles Interactions in Toulouse Urban Layer' (CAPITOUL). (author) [fr
Heat exchange studies on coconut oil cells as thermal energy storage for room thermal conditioning
Sutjahja, I. M.; Putri, Widya A.; Fahmi, Z.; Wonorahardjo, S.; Kurnia, D.
2017-07-01
As reported by many thermal environment experts, room air conditioning might be controlled by thermal mass system. In this paper we discuss the performance of coconut oil cells as room thermal energy storage. The heat exchange mechanism of coconut oil (CO) which is one of potential organic Phase Change Material (PCM) is studied based on the results of temperature measurements in the perimeter and core parts of cells. We found that the heat exchange performance, i.e. heat absorption and heat release processes of CO cells are dominated by heat conduction in the sensible solid from the higher temperature perimeter part to the lower temperature core part and heat convection during the solid-liquid phase transition and sensible liquid phase. The capability of heat absorption as measured by the reduction of air temperature is not influenced by CO cell size. Besides that, the application of CO as the thermal mass has to be accompanied by air circulation to get the cool sensation of the room’s occupants.
Energy-Efficient Implementation of ECDH Key Exchange for Wireless Sensor Networks
Lederer, Christian; Mader, Roland; Koschuch, Manuel; Großschädl, Johann; Szekely, Alexander; Tillich, Stefan
Wireless Sensor Networks (WSNs) are playing a vital role in an ever-growing number of applications ranging from environmental surveillance over medical monitoring to home automation. Since WSNs are often deployed in unattended or even hostile environments, they can be subject to various malicious attacks, including the manipulation and capture of nodes. The establishment of a shared secret key between two or more individual nodes is one of the most important security services needed to guarantee the proper functioning of a sensor network. Despite some recent advances in this field, the efficient implementation of cryptographic key establishment for WSNs remains a challenge due to the resource constraints of small sensor nodes such as the MICAz mote. In this paper we present a lightweight implementation of the elliptic curve Diffie-Hellman (ECDH) key exchange for ZigBee-compliant sensor nodes equipped with an ATmega128 processor running the TinyOS operating system. Our implementation uses a 192-bit prime field specified by the NIST as underlying algebraic structure and requires only 5.20 ·106 clock cycles to compute a scalar multiplication if the base point is fixed and known a priori. A scalar multiplication using a random base point takes about 12.33 ·106 cycles. Our results show that a full ECDH key exchange between two MICAz motes consumes an energy of 57.33 mJ (including radio communication), which is significantly better than most previously reported ECDH implementations on comparable platforms.
Modeling of Diffusion Process in the Isotopic Oxygen Exchange Experiments of CexZr(1-xO2 Catalysts
Directory of Open Access Journals (Sweden)
Arvaidas GALDIKAS
2013-03-01
Full Text Available The oxygen mobility processes during the temperature programmed oxygen isotopic exchange is considered by proposed kinetic model. Model includes simple and complex heteroexchange reactions and bulk diffusion processes. The model is applied to fit experimental curves of CexZr(1-xO2 catalysts with different composition in order to calculate reaction rates and diffusion coefficients, and activation energies of those processes.DOI: http://dx.doi.org/10.5755/j01.ms.19.1.1630
EFFECTS OF RUN-UP VELOCITY ON PERFORMANCE, KINEMATICS, AND ENERGY EXCHANGES IN THE POLE VAULT
Directory of Open Access Journals (Sweden)
Nicholas P. Linthorne
2012-06-01
Full Text Available This study examined the effect of run-up velocity on the peak height achieved by the athlete in the pole vault and on the corresponding changes in the athlete's kinematics and energy exchanges. Seventeen jumps by an experienced male pole vaulter were video recorded in the sagittal plane and a wide range of run-up velocities (4.5-8.5 m/s was obtained by setting the length of the athlete's run-up (2-16 steps. A selection of performance variables, kinematic variables, energy variables, and pole variables were calculated from the digitized video data. We found that the athlete's peak height increased linearly at a rate of 0.54 m per 1 m/s increase in run-up velocity and this increase was achieved through a combination of a greater grip height and a greater push height. At the athlete's competition run-up velocity (8.4 m/s about one third of the rate of increase in peak height arose from an increase in grip height and about two thirds arose from an increase in push height. Across the range of run-up velocities examined here the athlete always performed the basic actions of running, planting, jumping, and inverting on the pole. However, he made minor systematic changes to his jumping kinematics, vaulting kinematics, and selection of pole characteristics as the run-up velocity increased. The increase in run-up velocity and changes in the athlete's vaulting kinematics resulted in substantial changes to the magnitudes of the energy exchanges during the vault. A faster run-up produced a greater loss of energy during the take-off, but this loss was not sufficient to negate the increase in run-up velocity and the increase in work done by the athlete during the pole support phase. The athlete therefore always had a net energy gain during the vault. However, the magnitude of this gain decreased slightly as run-up velocity increased
Capabilities and accuracy of energy modelling software
CSIR Research Space (South Africa)
Osburn, L
2010-11-01
Full Text Available Energy modelling can be used in a number of different ways to fulfill different needs, including certification within building regulations or green building rating tools. Energy modelling can also be used in order to try and predict what the energy...
Effect of injection energy on residual dose around the charge exchange foil
Directory of Open Access Journals (Sweden)
Kazami Yamamoto
2012-12-01
Full Text Available The rapid cycling synchrotron (RCS of Japan Proton Accelerator Research Complex (J-PARC and the accumulator ring (AR of Spallation Neutron Source (SNS can be used as high-power pulsed neutron sources. In both cases, the injection region becomes one of the highest activation areas in the ring. However, residual dose distributions have revealed that the highest activation points in the J-PARC RCS and the SNS AR are different in detail. The dose of the charge exchange chamber in the SNS is more than 100 times larger than that of the RCS though the ratio of beam power is less than 10. We investigated the reason of this difference by Geant4 and MARS, and the calculation results indicated that the difference was due to the dependence of the neutron and pion production rate on the injection energy.
Energy Technology Data Exchange (ETDEWEB)
Martin, F.; Riera, A.; Yanez, M.
1986-05-15
We point out a fundamental difference between the molecular treatment of charge exchange X/sup n/++H(1s) and X/sup n/++He(1s/sup 2/) collisions, which is that the latter process involves molecular states that are formally autoionizing. Then standard ab initio methods do not, in general, yield the relevant wave functions that are needed in the collision treatment, irrespective of whether quasimolecular autoionization be significant or not during the collision. We implement a particularly simple and useful form of the Feshbach formalism to calculate the energies of those two electron systems, and a method to evaluate the corresponding dynamical couplings is presented for the first time. Our implementation of this formalism together with the new computational techniques involved are presented in detail.
Information exchange within the U.S. Department of Energy pollution prevention community
Energy Technology Data Exchange (ETDEWEB)
Thuot, J.R. [Argonne National Lab., IL (United States). Environmental Management Operations
1995-07-01
Improving Pollution Prevention and Waste Minimization Program (PP/WMIN) technologies, actions, and culture could be an important cost-cutting step for the US Department of Energy (DOE). Communicating ideas, concepts, process changes, and achievements is essential for the success of this program. The need to openly communicate ideas and concepts in a cost-effective manner is essential in an organization that has such diverse components as research and development, weapons production, and power generation. This approach is in contrast to the historic DOE culture developed within the cold war period in which compartmentalization, independence, and secrecy were stressed. DOE has now recognized that for any pollution prevention program to be successful, the many diverse elements of the organization must share information. Avenues for such information exchange are examined in this report.
Far-from-equilibrium processes without net thermal exchange via energy sorting.
Vilar, Jose M G; Rubi, J Miguel
2012-02-14
Many important processes at the microscale require far-from-equilibrium conditions to occur, as in the functioning of mesoscopic bioreactors, nanoscopic rotors, and nanoscale mass conveyors. Achieving such conditions, however, is typically based on energy inputs that strongly affect the thermal properties of the environment and the controllability of the system itself. Here, we present a general class of far-from-equilibrium processes that suppress the net thermal exchange with the environment by maintaining the Maxwell-Boltzmann velocity distribution intact. This new phenomenon, referred to as ghost equilibrium, results from the statistical cancellation of superheated and subcooled nonequilibrated degrees of freedom that are autonomously generated through a microscale energy sorting process. We provide general conditions to observe this phenomenon and study its implications for manipulating energy at the microscale. The results are applied explicitly to two mechanistically different cases, an ensemble of rotational dipoles and a gas of trapped particles, which encompass a great variety of common situations involving both rotational and translational degrees of freedom. © 2012 American Institute of Physics
Hybrid Energy System Modeling in Modelica
Energy Technology Data Exchange (ETDEWEB)
William R. Binder; Christiaan J. J. Paredis; Humberto E. Garcia
2014-03-01
In this paper, a Hybrid Energy System (HES) configuration is modeled in Modelica. Hybrid Energy Systems (HES) have as their defining characteristic the use of one or more energy inputs, combined with the potential for multiple energy outputs. Compared to traditional energy systems, HES provide additional operational flexibility so that high variability in both energy production and consumption levels can be absorbed more effectively. This is particularly important when including renewable energy sources, whose output levels are inherently variable, determined by nature. The specific HES configuration modeled in this paper include two energy inputs: a nuclear plant, and a series of wind turbines. In addition, the system produces two energy outputs: electricity and synthetic fuel. The models are verified through simulations of the individual components, and the system as a whole. The simulations are performed for a range of component sizes, operating conditions, and control schemes.
Specification of a STEP Based Reference Model for Exchange of Robotics Models
DEFF Research Database (Denmark)
Haenisch, Jochen; Kroszynski, Uri; Ludwig, Arnold
combining geometric, dynamic, process and robot specific data.The growing need for accurate information about manufacturing data (models of robots and other mechanisms) in diverse industrial applications has initiated ESPRIT Project 6457: InterRob. Besides the topics associated with standards for industrial...... of pilot processor programs are based. The processors allow for the exchange of product data models between Analysis systems (e.g. ADAMS), CAD systems (e.g. CATIA, BRAVO), Simulation and off-line programming systems (e.g. GRASP, KISMET, ROPSIM)....
Optimization of Heat Exchangers
International Nuclear Information System (INIS)
Catton, Ivan
2010-01-01
The objective of this research is to develop tools to design and optimize heat exchangers (HE) and compact heat exchangers (CHE) for intermediate loop heat transport systems found in the very high temperature reator (VHTR) and other Generation IV designs by addressing heat transfer surface augmentation and conjugate modeling. To optimize heat exchanger, a fast running model must be created that will allow for multiple designs to be compared quickly. To model a heat exchanger, volume averaging theory, VAT, is used. VAT allows for the conservation of mass, momentum and energy to be solved for point by point in a 3 dimensional computer model of a heat exchanger. The end product of this project is a computer code that can predict an optimal configuration for a heat exchanger given only a few constraints (input fluids, size, cost, etc.). As VAT computer code can be used to model characteristics (pumping power, temperatures, and cost) of heat exchangers more quickly than traditional CFD or experiment, optimization of every geometric parameter simultaneously can be made. Using design of experiment, DOE and genetric algorithms, GE, to optimize the results of the computer code will improve heat exchanger design.
Optimization of Heat Exchangers
Energy Technology Data Exchange (ETDEWEB)
Ivan Catton
2010-10-01
The objective of this research is to develop tools to design and optimize heat exchangers (HE) and compact heat exchangers (CHE) for intermediate loop heat transport systems found in the very high temperature reator (VHTR) and other Generation IV designs by addressing heat transfer surface augmentation and conjugate modeling. To optimize heat exchanger, a fast running model must be created that will allow for multiple designs to be compared quickly. To model a heat exchanger, volume averaging theory, VAT, is used. VAT allows for the conservation of mass, momentum and energy to be solved for point by point in a 3 dimensional computer model of a heat exchanger. The end product of this project is a computer code that can predict an optimal configuration for a heat exchanger given only a few constraints (input fluids, size, cost, etc.). As VAT computer code can be used to model characteristics )pumping power, temperatures, and cost) of heat exchangers more quickly than traditional CFD or experiment, optimization of every geometric parameter simultaneously can be made. Using design of experiment, DOE and genetric algorithms, GE, to optimize the results of the computer code will improve heat exchanger disign.
A Distributed Model of Oilseed Biorefining, via Integrated Industrial Ecology Exchanges
Ferrell, Jeremy C.
As the demand for direct petroleum substitutes increases, biorefineries are poised to become centers for conversion of biomass into fuels, energy, and biomaterials. A distributed model offers reduced transportation, tailored process technology to available feedstock, and increased local resilience. Oilseeds are capable of producing a wide variety of useful products additive to food, feed, and fuel needs. Biodiesel manufacturing technology lends itself to smaller-scale distributed facilities able to process diverse feedstocks and meet demand of critical diesel fuel for basic municipal services, safety, sanitation, infrastructure repair, and food production. Integrating biodiesel refining facilities as tenants of eco-industrial parks presents a novel approach for synergistic energy and material exchanges whereby environmental and economic metrics can be significantly improved upon compared to stand alone models. This research is based on the Catawba County NC EcoComplex and the oilseed crushing and biodiesel processing facilities (capacity-433 tons biodiesel per year) located within. Technical and environmental analyses of the biorefinery components as well as agronomic and economic models are presented. The life cycle assessment for the two optimal biodiesel feedstocks, soybeans and used cooking oil, resulted in fossil energy ratios of 7.19 and 12.1 with carbon intensity values of 12.51 gCO2-eq/MJ and 7.93 gCO2-eq/MJ, respectively within the industrial ecology system. Economic modeling resulted in a biodiesel conversion cost of 1.43 per liter of fuel produced with used cooking oil, requiring a subsidy of 0.58 per liter to reach the break-even point. As subsidies continue significant fluctuation, metrics other than operating costs are required to justify small-scale biofuel projects.
U.S. Environmental Protection Agency — This dataset provides the city-specific air exchange rate measurements, modeled, literature-based as well as housing characteristics. This dataset is associated with...
An Early Model for Value and Sustainability in Health Information Exchanges: Qualitative Study.
Feldman, Sue S
2018-04-30
The primary value relative to health information exchange has been seen in terms of cost savings relative to laboratory and radiology testing, emergency department expenditures, and admissions. However, models are needed to statistically quantify value and sustainability and better understand the dependent and mediating factors that contribute to value and sustainability. The purpose of this study was to provide a basis for early model development for health information exchange value and sustainability. A qualitative study was conducted with 21 interviews of eHealth Exchange participants across 10 organizations. Using a grounded theory approach and 3.0 as a relative frequency threshold, 5 main categories and 16 subcategories emerged. This study identifies 3 core current perceived value factors and 5 potential perceived value factors-how interviewees predict health information exchanges may evolve as there are more participants. These value factors were used as the foundation for early model development for sustainability of health information exchange. Using the value factors from the interviews, the study provides the basis for early model development for health information exchange value and sustainability. This basis includes factors from the research: fostering consumer engagement; establishing a provider directory; quantifying use, cost, and clinical outcomes; ensuring data integrity through patient matching; and increasing awareness, usefulness, interoperability, and sustainability of eHealth Exchange. ©Sue S Feldman. Originally published in JMIR Medical Informatics (http://medinform.jmir.org), 30.04.2018.
Energy Systems Modelling Research and Analysis
DEFF Research Database (Denmark)
Møller Andersen, Frits; Alberg Østergaard, Poul
2015-01-01
This editorial introduces the seventh volume of the International Journal of Sustainable Energy Planning and Management. The volume presents part of the outcome of the project Energy Systems Modelling Research and Analysis (ENSYMORA) funded by the Danish Innovation Fund. The project carried out...... by 11 university and industry partners has improved the basis for decision-making within energy planning and energy scenario making by providing new and improved tools and methods for energy systems analyses....
A model for foreign exchange markets based on glassy Brownian systems
Sánchez-Granero, M. A.; Trinidad-Segovia, J. E.; Clara-Rahola, J.; Puertas, A. M.; De las Nieves, F. J.
2017-01-01
In this work we extend a well-known model from arrested physical systems, and employ it in order to efficiently depict different currency pairs of foreign exchange market price fluctuation distributions. We consider the exchange rate price in the time range between 2010 and 2016 at yearly time intervals and resolved at one minute frequency. We then fit the experimental datasets with this model, and find significant qualitative symmetry between price fluctuation distributions from the currency...
The Monetary Model of Exchange Rate: Evidence from the Philippines Using ARDL Approach
Sovannroeun SAMRETH; Dara LONG
2008-01-01
In this paper, we re-examine the validity of both short and long run monetary models of exchange rate for the case of the Philippines by using new approach called Autoregressive Distributed Lag (ARDL) to cointegration. From our analysis, some findings are obtained. First, there are robust short and long run relationships between variables in the monetary exchange rate model. Second, the stability of the estimated parameters is confirmed by CUSUM and CUMSUQ stability tests. Third, the Purchasi...
Explaining the Exchange Rate Pass-Through in Hungary: Simulations with the NIGEM Model
Zoltán M. Jakab; Mihály András Kovács
2003-01-01
This paper explores the major determinants of the exchange rate pass-through to CPI. The simulations were performed with the Bank's estimated Hungarian block linked to the NIGEM model of the National Institute of Economic and Social Research (NIESR). The modelling framework offers some insight into the role of different markets in the price-exchange rate relationship. The paper gives an analysis of the relative importance of expectations, goods and labour market parameters. Our results show t...
Comparing holographic dark energy models with statefinder
International Nuclear Information System (INIS)
Cui, Jing-Lei; Zhang, Jing-Fei
2014-01-01
We apply the statefinder diagnostic to the holographic dark energy models, including the original holographic dark energy (HDE) model, the new holographic dark energy model, the new agegraphic dark energy (NADE) model, and the Ricci dark energy model. In the low-redshift region the holographic dark energy models are degenerate with each other and with the ΛCDM model in the H(z) and q(z) evolutions. In particular, the HDE model is highly degenerate with the ΛCDM model, and in the HDE model the cases with different parameter values are also in strong degeneracy. Since the observational data are mainly within the low-redshift region, it is very important to break this lowredshift degeneracy in the H(z) and q(z) diagnostics by using some quantities with higher order derivatives of the scale factor. It is shown that the statefinder diagnostic r(z) is very useful in breaking the low-redshift degeneracies. By employing the statefinder diagnostic the holographic dark energy models can be differentiated efficiently in the low-redshift region. The degeneracy between the holographic dark energy models and the ΛCDM model can also be broken by this method. Especially for the HDE model, all the previous strong degeneracies appearing in the H(z) and q(z) diagnostics are broken effectively. But for the NADE model, the degeneracy between the cases with different parameter values cannot be broken, even though the statefinder diagnostic is used. A direct comparison of the holographic dark energy models in the r-s plane is also made, in which the separations between the models (including the ΛCDM model) can be directly measured in the light of the current values {r 0 , s 0 } of the models. (orig.)
Impact of Groundwater Flow and Energy Load on Multiple Borehole Heat Exchangers.
Dehkordi, S Emad; Schincariol, Robert A; Olofsson, Bo
2015-01-01
The effect of array configuration, that is, number, layout, and spacing, on the performance of multiple borehole heat exchangers (BHEs) is generally known under the assumption of fully conductive transport. The effect of groundwater flow on BHE performance is also well established, but most commonly for single BHEs. In multiple-BHE systems the effect of groundwater advection can be more complicated due to the induced thermal interference between the boreholes. To ascertain the influence of groundwater flow and borehole arrangement, this study investigates single- and multi-BHE systems of various configurations. Moreover, the influence of energy load balance is also examined. The results from corresponding cases with and without groundwater flow as well as balanced and unbalanced energy loads are cross-compared. The groundwater flux value, 10(-7) m/s, is chosen based on the findings of previous studies on groundwater flow interaction with BHEs and thermal response tests. It is observed that multi-BHE systems with balanced loads are less sensitive to array configuration attributes and groundwater flow, in the long-term. Conversely, multi-BHE systems with unbalanced loads are influenced by borehole array configuration as well as groundwater flow; these effects become more pronounced with time, unlike when the load is balanced. Groundwater flow has more influence on stabilizing loop temperatures, compared to array characteristics. Although borehole thermal energy storage (BTES) systems have a balanced energy load function, preliminary investigation on their efficiency shows a negative impact by groundwater which is due to their dependency on high temperature gradients between the boreholes and surroundings. © 2014, National Ground Water Association.
Directory of Open Access Journals (Sweden)
Minakhi Rout
2014-01-01
Full Text Available To alleviate the limitations of statistical based methods of forecasting of exchange rates, soft and evolutionary computing based techniques have been introduced in the literature. To further the research in this direction this paper proposes a simple but promising hybrid prediction model by suitably combining an adaptive autoregressive moving average (ARMA architecture and differential evolution (DE based training of its feed-forward and feed-back parameters. Simple statistical features are extracted for each exchange rate using a sliding window of past data and are employed as input to the prediction model for training its internal coefficients using DE optimization strategy. The prediction efficiency is validated using past exchange rates not used for training purpose. Simulation results using real life data are presented for three different exchange rates for one–fifteen months’ ahead predictions. The results of the developed model are compared with other four competitive methods such as ARMA-particle swarm optimization (PSO, ARMA-cat swarm optimization (CSO, ARMA-bacterial foraging optimization (BFO and ARMA-forward backward least mean square (FBLMS. The derivative based ARMA-FBLMS forecasting model exhibits worst prediction performance of the exchange rates. Comparisons of different performance measures including the training time of the all three evolutionary computing based models demonstrate that the proposed ARMA-DE exchange rate prediction model possesses superior short and long range prediction potentiality compared to others.
Technology Learning Ratios in Global Energy Models
International Nuclear Information System (INIS)
Varela, M.
2001-01-01
The process of introduction of a new technology supposes that while its production and utilisation increases, also its operation improves and its investment costs and production decreases. The accumulation of experience and learning of a new technology increase in parallel with the increase of its market share. This process is represented by the technological learning curves and the energy sector is not detached from this process of substitution of old technologies by new ones. The present paper carries out a brief revision of the main energy models that include the technology dynamics (learning). The energy scenarios, developed by global energy models, assume that the characteristics of the technologies are variables with time. But this trend is incorporated in a exogenous way in these energy models, that is to say, it is only a time function. This practice is applied to the cost indicators of the technology such as the specific investment costs or to the efficiency of the energy technologies. In the last years, the new concept of endogenous technological learning has been integrated within these global energy models. This paper examines the concept of technological learning in global energy models. It also analyses the technological dynamics of the energy system including the endogenous modelling of the process of technological progress. Finally, it makes a comparison of several of the most used global energy models (MARKAL, MESSAGE and ERIS) and, more concretely, about the use these models make of the concept of technological learning. (Author) 17 refs
Energy Technology Data Exchange (ETDEWEB)
Kuldna, Piret, E-mail: piret.kuldna@seit.ee [Stockholm Environment Institute Tallinn Centre, Lai 34, Tallinn 10133 (Estonia); Peterson, Kaja [Stockholm Environment Institute Tallinn Centre, Lai 34, Tallinn 10133 (Estonia); Kuhi-Thalfeldt, Reeli [Stockholm Environment Institute Tallinn Centre, Lai 34, Tallinn 10133 (Estonia); Tallinn University of Technology, Ehitajate tee 5, Tallinn 19086 (Estonia)
2015-09-15
Strategic Environmental Assessment (SEA) serves as a platform for bringing together researchers, policy developers and other stakeholders to evaluate and communicate significant environmental and socio-economic effects of policies, plans and programmes. Quantitative computer models can facilitate knowledge exchange between various parties that strive to use scientific findings to guide policy-making decisions. The process of facilitating knowledge generation and exchange, i.e. knowledge brokerage, has been increasingly explored, but there is not much evidence in the literature on how knowledge brokerage activities are used in full cycles of SEAs which employ quantitative models. We report on the SEA process of the national energy plan with reflections on where and how the Long-range Energy Alternatives Planning (LEAP) model was used for knowledge brokerage on emissions modelling between researchers and policy developers. Our main suggestion is that applying a quantitative model not only in ex ante, but also ex post scenario modelling and associated impact assessment can facilitate systematic and inspiring knowledge exchange process on a policy problem and capacity building of participating actors. - Highlights: • We examine the knowledge brokering on emissions modelling between researchers and policy developers in a full cycle of SEA. • Knowledge exchange process can evolve at any modelling stage within SEA. • Ex post scenario modelling enables systematic knowledge exchange and learning on a policy problem.
International Nuclear Information System (INIS)
Kuldna, Piret; Peterson, Kaja; Kuhi-Thalfeldt, Reeli
2015-01-01
Strategic Environmental Assessment (SEA) serves as a platform for bringing together researchers, policy developers and other stakeholders to evaluate and communicate significant environmental and socio-economic effects of policies, plans and programmes. Quantitative computer models can facilitate knowledge exchange between various parties that strive to use scientific findings to guide policy-making decisions. The process of facilitating knowledge generation and exchange, i.e. knowledge brokerage, has been increasingly explored, but there is not much evidence in the literature on how knowledge brokerage activities are used in full cycles of SEAs which employ quantitative models. We report on the SEA process of the national energy plan with reflections on where and how the Long-range Energy Alternatives Planning (LEAP) model was used for knowledge brokerage on emissions modelling between researchers and policy developers. Our main suggestion is that applying a quantitative model not only in ex ante, but also ex post scenario modelling and associated impact assessment can facilitate systematic and inspiring knowledge exchange process on a policy problem and capacity building of participating actors. - Highlights: • We examine the knowledge brokering on emissions modelling between researchers and policy developers in a full cycle of SEA. • Knowledge exchange process can evolve at any modelling stage within SEA. • Ex post scenario modelling enables systematic knowledge exchange and learning on a policy problem
Dynamic energy models and carbon mitigation policies
Tilley, Luke A.
In this dissertation I examine a specific class of energy models and their implications for carbon mitigation policies. The class of models includes a production function capable of reproducing the empirically observed phenomenon of short run rigidity of energy use in response to energy price changes and long run exibility of energy use in response to energy price changes. I use a theoretical model, parameterized using empirical data, to simulate economic performance under several tax regimes where taxes are levied on capital income, investment, and energy. I also investigate transitions from one tax regime to another. I find that energy taxes intended to reduce energy use can successfully achieve those goals with minimal or even positive impacts on macroeconomic performance. But the transition paths to new steady states are lengthy, making political commitment to such policies very challenging.
Model-based analysis of anion-exchanger positioning in direct methanol fuel cell systems
Kraus, Maik; Schröder, Daniel; Krewer, Ulrike
2014-09-01
In this work we present a model based study to investigate the presence of anion exchangers in direct methanol fuel cell (DMFC) systems. It is well known that environmental or fuel impurities lead to accumulation of harmful anions, such as chloride, in the system. However, due to DMFC anodic reaction, a carbonate system is present. These corbanate anions have to be taken into account for the anion exchanger design and placement as well as for the system operation strategy with and without anion exchanger, which is the objective of this study. For this purpose, the expected amount of harmful chloride ions in a DMFC system is estimated, and that of carbonate ions is calculated with a model of the carbonate system in a DMFC system. The predicition of durability and dimensions of an anion exchanger is based on a monovalent anion exchange model. The design of gas liquid separators in the DMFC system has a major influence on the amount of dissolved carbon dioxide, which is crucial for durability and dimension of a system integrated anion exchanger. Finally, feasible positions of anion exchanger in a DMFC system are elaborated to fulfill the needs for long term and stable DMFC operation.
Fan cycling strategies and heat pipe heat exchangers provide energy efficient dehumidification
Energy Technology Data Exchange (ETDEWEB)
Shirey, D.B. III [Florida Solar Energy Center, Cape Canaveral, FL (United States)
1995-03-01
This article describes two methods to reduce energy consumption and peak demand in buildings that require humidity control that were demonstrated at the Salvador Dali Museum in St. Petersburg, Florida. The first method centered on alternative indoor fan cycling strategies and the second method involved the use of heat pipe heat exchangers. Both approaches increased the dehumidification performance of the existing air-conditioning systems and provided substantial savings. Simple, low cost alternative fan cycling strategies were used. When possible, auto fan control replaced constant fan operation to avoid excess fan energy consumption, ventilation load and compressor operation. The alternative fan control strategies reduced indoor humidity fluctuations in all zones, and significantly reduced overall humidity levels in the museum lobby and storage area. An HPHX was installed within one of the two gallery RTUs to improve the unit`s dehumidification performance. The passive HPHX significantly reduced electric reheat and compressor operation while maintaining the precise temperature and humidity requirements within the gallery. The second gallery RTU now operates primarily as a back-up unit to the heat pipe-assisted air-conditioning unit.
Anomalous energy exchange in the gBL and quasilinear theories
International Nuclear Information System (INIS)
Mynick, H.E.
1992-02-01
The rate of turbulence-induced energy exchange W o between species is computed in the framework of the quasilinear and gBL transport theories, and the relationship between these two theories, and the relationship between these two similar theories is thereby elucidated. For both theories, general formal expressions for W o are developed, and then applied to the trapped electron mode for illustration. The general expressions for W o in the two theories are formally closely related, but can yield predictions of very different magnitude in concrete applications. The fact that quasilinear theory is not valid for saturated steady-state turbulence gives rise to certain peculiarities in its predictions for this normal experimental situation, such as permitting energy to flow from the cooler to the hotter species, even in the limit of thermal equilibrium, where real-space gradients vanish. The gBL theory may be viewed as a modification of quasilinear theory to be valid for steady-state turbulence, keeping extra terms due to the self-consistent back reaction of particles on the fluctuations, which are just such as to eliminate these peculiarities
Directory of Energy Information Administration models 1996
Energy Technology Data Exchange (ETDEWEB)
NONE
1996-07-01
This directory revises and updates the Directory of Energy Information Administration Models 1995, DOE/EIA-0293(95), Energy Information Administration (EIA), U.S. Department of Energy, July 1995. Four models have been deleted in this directory as they are no longer being used: (1) Market Penetration Model for Ground-Water Heat Pump Systems (MPGWHP); (2) Market Penetration Model for Residential Rooftop PV Systems (MPRESPV-PC); (3) Market Penetration Model for Active and Passive Solar Technologies (MPSOLARPC); and (4) Revenue Requirements Modeling System (RRMS).
An Empirical Model for Energy Storage Systems
Energy Technology Data Exchange (ETDEWEB)
Rosewater, David Martin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Scott, Paul [TransPower, Poway, CA (United States)
2016-03-17
Improved models of energy storage systems are needed to enable the electric grid’s adaptation to increasing penetration of renewables. This paper develops a generic empirical model of energy storage system performance agnostic of type, chemistry, design or scale. Parameters for this model are calculated using test procedures adapted from the US DOE Protocol for Uniformly Measuring and Expressing the Performance of Energy Storage. We then assess the accuracy of this model for predicting the performance of the TransPower GridSaver – a 1 MW rated lithium-ion battery system that underwent laboratory experimentation and analysis. The developed model predicts a range of energy storage system performance based on the uncertainty of estimated model parameters. Finally, this model can be used to better understand the integration and coordination of energy storage on the electric grid.
DEFF Research Database (Denmark)
Alberdi Pagola, Maria; Poulsen, Søren Erbs; Loveridge, Fleur
2018-01-01
This paper investigates the applicability of currently available analytical, empirical and numerical heat flow models for interpreting thermal response tests (TRT) of quadratic cross section precast pile heat exchangers. A 3D finite element model (FEM) is utilised for interpreting five TRTs...... by inverse modelling. The calibrated estimates of soil and concrete thermal conductivity are consistent with independent laboratory measurements. Due to the computational cost of inverting the 3D model, simpler models are utilised in additional calibrations. Interpretations based on semi-empirical pile G-functions...... the potential of applying TRTs for sizing quadratic, precast pile heat exchanger foundations....
Swat, MJ; Moodie, S; Wimalaratne, SM; Kristensen, NR; Lavielle, M; Mari, A; Magni, P; Smith, MK; Bizzotto, R; Pasotti, L; Mezzalana, E; Comets, E; Sarr, C; Terranova, N; Blaudez, E; Chan, P; Chard, J; Chatel, K; Chenel, M; Edwards, D; Franklin, C; Giorgino, T; Glont, M; Girard, P; Grenon, P; Harling, K; Hooker, AC; Kaye, R; Keizer, R; Kloft, C; Kok, JN; Kokash, N; Laibe, C; Laveille, C; Lestini, G; Mentré, F; Munafo, A; Nordgren, R; Nyberg, HB; Parra-Guillen, ZP; Plan, E; Ribba, B; Smith, G; Trocóniz, IF; Yvon, F; Milligan, PA; Harnisch, L; Karlsson, M; Hermjakob, H; Le Novère, N
2015-01-01
The lack of a common exchange format for mathematical models in pharmacometrics has been a long-standing problem. Such a format has the potential to increase productivity and analysis quality, simplify the handling of complex workflows, ensure reproducibility of research, and facilitate the reuse of existing model resources. Pharmacometrics Markup Language (PharmML), currently under development by the Drug Disease Model Resources (DDMoRe) consortium, is intended to become an exchange standard in pharmacometrics by providing means to encode models, trial designs, and modeling steps. PMID:26225259
A quantitative approach to developing more mechanistic gas exchange models for field grown potato
DEFF Research Database (Denmark)
Ahmadi, Seyed Hamid; Andersen, Mathias Neumann; Poulsen, Rolf Thostrup
2009-01-01
In this study we introduce new gas exchange models that are developed under natural conditions of field grown potato. The new models could explain about 85% of the stomatal conductance variations, which was much higher than the well-known gas exchange models such as the Ball-Berry model [Ball...... and photosynthesis rate, respectively, were significantly higher and lower than unity....... the stomatal conductance regulation. While previous models considered the same weighting for relative humidity and photosynthesis rate, we found that relative humidity has a more pronounced regulating effect on stomatal conductance than photosynthesis rate and the weightings for relative humidity...
Directory of Open Access Journals (Sweden)
Jeanette Janaina Jaber Lucato
2009-06-01
Full Text Available OBJECTIVES: To evaluate and compare the efficiency of humidification in available heat and moisture exchanger models under conditions of varying tidal volume, respiratory rate, and flow rate. INTRODUCTION: Inspired gases are routinely preconditioned by heat and moisture exchangers to provide a heat and water content similar to that provided normally by the nose and upper airways. The absolute humidity of air retrieved from and returned to the ventilated patient is an important measurable outcome of the heat and moisture exchangers' humidifying performance. METHODS: Eight different heat and moisture exchangers were studied using a respiratory system analog. The system included a heated chamber (acrylic glass, maintained at 37°C, a preserved swine lung, a hygrometer, circuitry and a ventilator. Humidity and temperature levels were measured using eight distinct interposed heat and moisture exchangers given different tidal volumes, respiratory frequencies and flow-rate conditions. Recovery of absolute humidity (%RAH was calculated for each setting. RESULTS: Increasing tidal volumes led to a reduction in %RAH for all heat and moisture exchangers while no significant effect was demonstrated in the context of varying respiratory rate or inspiratory flow. CONCLUSIONS: Our data indicate that heat and moisture exchangers are more efficient when used with low tidal volume ventilation. The roles of flow and respiratory rate were of lesser importance, suggesting that their adjustment has a less significant effect on the performance of heat and moisture exchangers.
Lucato, Jeanette Janaina Jaber; Adams, Alexander Bernard; Souza, Rogério; Torquato, Jamili Anbar; Carvalho, Carlos Roberto Ribeiro; Marini, John J
2009-01-01
To evaluate and compare the efficiency of humidification in available heat and moisture exchanger models under conditions of varying tidal volume, respiratory rate, and flow rate. Inspired gases are routinely preconditioned by heat and moisture exchangers to provide a heat and water content similar to that provided normally by the nose and upper airways. The absolute humidity of air retrieved from and returned to the ventilated patient is an important measurable outcome of the heat and moisture exchangers' humidifying performance. Eight different heat and moisture exchangers were studied using a respiratory system analog. The system included a heated chamber (acrylic glass, maintained at 37 degrees C), a preserved swine lung, a hygrometer, circuitry and a ventilator. Humidity and temperature levels were measured using eight distinct interposed heat and moisture exchangers given different tidal volumes, respiratory frequencies and flow-rate conditions. Recovery of absolute humidity (%RAH) was calculated for each setting. Increasing tidal volumes led to a reduction in %RAH for all heat and moisture exchangers while no significant effect was demonstrated in the context of varying respiratory rate or inspiratory flow. Our data indicate that heat and moisture exchangers are more efficient when used with low tidal volume ventilation. The roles of flow and respiratory rate were of lesser importance, suggesting that their adjustment has a less significant effect on the performance of heat and moisture exchangers.
Stationarity test with a direct test for heteroskedasticity in exchange rate forecasting models
Khin, Aye Aye; Chau, Wong Hong; Seong, Lim Chee; Bin, Raymond Ling Leh; Teng, Kevin Low Lock
2017-05-01
Global economic has been decreasing in the recent years, manifested by the greater exchange rates volatility on international commodity market. This study attempts to analyze some prominent exchange rate forecasting models on Malaysian commodity trading: univariate ARIMA, ARCH and GARCH models in conjunction with stationarity test on residual diagnosis direct testing of heteroskedasticity. All forecasting models utilized the monthly data from 1990 to 2015. Given a total of 312 observations, the data used to forecast both short-term and long-term exchange rate. The forecasting power statistics suggested that the forecasting performance of ARIMA (1, 1, 1) model is more efficient than the ARCH (1) and GARCH (1, 1) models. For ex-post forecast, exchange rate was increased from RM 3.50 per USD in January 2015 to RM 4.47 per USD in December 2015 based on the baseline data. For short-term ex-ante forecast, the analysis results indicate a decrease in exchange rate on 2016 June (RM 4.27 per USD) as compared with 2015 December. A more appropriate forecasting method of exchange rate is vital to aid the decision-making process and planning on the sustainable commodities' production in the world economy.
International Nuclear Information System (INIS)
Nekrasov, Anatoly K.
2011-01-01
Thermal instability in an electron-ion magnetized plasma, which is relevant in the intragalactic medium of galaxy clusters, solar corona, and other two-component plasma objects, is investigated. We apply the multicomponent plasma approach where the dynamics of all species are considered separately through electric field perturbations. General expressions for the dynamical variables obtained in this paper can be applied over a wide range of astrophysical and laboratory plasmas also containing neutrals and dust grains. We assume that background temperatures of electrons and ions are different and include the energy exchange in thermal equations for electrons and ions along with the collisional momentum exchange in equations of motion. We take into account the dependence of collision frequency on density and temperature perturbations. The cooling-heating functions are taken for both electrons and ions. A condensation mode of thermal instability has been studied in the fast sound speed limit. We derive a new dispersion relation including different electron and ion cooling-heating functions and other effects mentioned above and find its simple solutions for growth rates in limiting cases. We show that the perturbations have an electromagnetic nature and demonstrate the crucial role of the electric field perturbation along the background magnetic field in the fast sound speed limit. We find that at the conditions under consideration, condensation must occur along the magnetic field while the transverse scale sizes can be both larger and smaller than the longitudinal ones. The results obtained can be useful for interpretating observations of dense cold regions in astrophysical objects.
High-energy-ion depletion in the charge exchange spectrum of Alcator C
International Nuclear Information System (INIS)
Schissel, D.P.
1982-01-01
A three-dimensional, guiding center, Monte Carlo code is developed to study ion orbits in Alcator C. The highly peaked ripple of the magnetic field of Alcator is represented by an analytical expression for the vector potential. The analytical ripple field is compared to the resulting magnetic field generated by a current model of the toroidal plates; agreement is excellent. Ion-Ion scattering is simulated by a pitch angle and an energy scattering operator. The equations of motion are integrated with a variable time step, extrapolating integrator. The code produces collisionless banana and ripple trapped loss cones which agree well with present theory. Global energy distributions have been calculated and show a slight depletion above 8.5 keV. Particles which are ripple trapped and lost are at energies below where depletion is observed. It is found that ions pitch angle scatter less as energy is increased. The result is that, when viewed in velocity space, ions form probability lobes the shape of mouse ears which are fat near the thermal energy. Therefore, particles enter the loss cone at low energies near the bottom of the core. Recommendations for future work include improving the analytic model of the ripple field, testing the effect of del . B not equal to 0 on ion orbits, and improving the efficiency of the code by either using a spline fit for the magnetic fields or by creating a vectorized Monte Carlo code
Models for the energy performance of low-energy houses
DEFF Research Database (Denmark)
Andersen, Philip Hvidthøft Delff
of buildings is needed both in order to assess energy-effciency and to operate modern buildings economically. Energy signatures are a central tool in both energy performance assessment and decision making related to refurbishment of buildings. Also for operation of modern buildings with installations......-building. The building is well-insulated and features large modern energy-effcient windows and oor heating. These features lead to increased non-linear responses to solar radiation and longer time constants. The building is equipped with advanced control and measuring equipment. Experiments are designed and performed...... in order to identify important dynamical properties of the building, and the collected data is used for modeling. The thesis emphasizes the statistical model building and validation needed to identify dynamical systems. It distinguishes from earlier work by focusing on modern low-energy construction...
DEFF Research Database (Denmark)
Olchev, A.; Ibrom, Andreas; Ross, T.
2008-01-01
An one-dimensional process-based SVAT model (Mixfor-SVAT) was developed to describe energy, water and carbon dioxide exchanges between vegetation canopy and the atmosphere at a local scale. Simulation of the energy, water and CO2 fluxes in Mixfor-SVAT is based on aggregated description of the phy......An one-dimensional process-based SVAT model (Mixfor-SVAT) was developed to describe energy, water and carbon dioxide exchanges between vegetation canopy and the atmosphere at a local scale. Simulation of the energy, water and CO2 fluxes in Mixfor-SVAT is based on aggregated description...... in measured data series caused by some instrumental errors, sensor wetting, changes in the footprint or fast changes in turbulence conditions resulted in some reduction of correlation between modeled and measured fluxes (e.g. r(2) = 0.62 for CO2 and r(2) = 0.64 for H2O fluxes under friction velocity u* > 0...
Modeling net ecosystem carbon exchange of alpine grasslands with a satellite-driven model.
Directory of Open Access Journals (Sweden)
Wei Yan
Full Text Available Estimate of net ecosystem carbon exchange (NEE between the atmosphere and terrestrial ecosystems, the balance of gross primary productivity (GPP and ecosystem respiration (Reco has significant importance for studying the regional and global carbon cycles. Using models driven by satellite data and climatic data is a promising approach to estimate NEE at regional scales. For this purpose, we proposed a semi-empirical model to estimate NEE in this study. In our model, the component GPP was estimated with a light response curve of a rectangular hyperbola. The component Reco was estimated with an exponential function of soil temperature. To test the feasibility of applying our model at regional scales, the temporal variations in the model parameters derived from NEE observations in an alpine grassland ecosystem on Tibetan Plateau were investigated. The results indicated that all the inverted parameters exhibit apparent seasonality, which is in accordance with air temperature and canopy phenology. In addition, all the parameters have significant correlations with the remote sensed vegetation indexes or environment temperature. With parameters estimated with these correlations, the model illustrated fair accuracy both in the validation years and at another alpine grassland ecosystem on Tibetan Plateau. Our results also indicated that the model prediction was less accurate in drought years, implying that soil moisture is an important factor affecting the model performance. Incorporating soil water content into the model would be a critical step for the improvement of the model.
Directory of Energy Information Administration Models 1994
Energy Technology Data Exchange (ETDEWEB)
1994-07-01
This directory revises and updates the 1993 directory and includes 15 models of the National Energy Modeling System (NEMS). Three other new models in use by the Energy Information Administration (EIA) have also been included: the Motor Gasoline Market Model (MGMM), Distillate Market Model (DMM), and the Propane Market Model (PPMM). This directory contains descriptions about each model, including title, acronym, purpose, followed by more detailed information on characteristics, uses and requirements. Sources for additional information are identified. Included in this directory are 37 EIA models active as of February 1, 1994.
Directory of Energy Information Administration Models 1994
International Nuclear Information System (INIS)
1994-07-01
This directory revises and updates the 1993 directory and includes 15 models of the National Energy Modeling System (NEMS). Three other new models in use by the Energy Information Administration (EIA) have also been included: the Motor Gasoline Market Model (MGMM), Distillate Market Model (DMM), and the Propane Market Model (PPMM). This directory contains descriptions about each model, including title, acronym, purpose, followed by more detailed information on characteristics, uses and requirements. Sources for additional information are identified. Included in this directory are 37 EIA models active as of February 1, 1994
Energy flow modeling and optimal operation analysis of the micro energy grid based on energy hub
International Nuclear Information System (INIS)
Ma, Tengfei; Wu, Junyong; Hao, Liangliang
2017-01-01
Highlights: • Design a novel architecture for energy hub integrating power hub, cooling hub and heating hub. • The micro energy grid based on energy hub is introduced and its advantages are discussed. • Propose a generic modeling method for the energy flow of micro energy grid. • Propose an optimal operation model for micro energy grid with considering demand response. • The roles of renewable energy, energy storage devices and demand response are discussed separately. - Abstract: The energy security and environmental problems impel people to explore a more efficient, environment friendly and economical energy utilization pattern. In this paper, the coordinated operation and optimal dispatch strategies for multiple energy system are studied at the whole Micro Energy Grid level. To augment the operation flexibility of energy hub, the innovation sub-energy hub structure including power hub, heating hub and cooling hub is put forward. Basing on it, a generic energy hub architecture integrating renewable energy, combined cooling heating and power, and energy storage devices is developed. Moreover, a generic modeling method for the energy flow of micro energy grid is proposed. To minimize the daily operation cost, a day-ahead dynamic optimal operation model is formulated as a mixed integer linear programming optimization problem with considering the demand response. Case studies are undertaken on a community Micro Energy Grid in four different scenarios on a typical summer day and the roles of renewable energy, energy storage devices and demand response are discussed separately. Numerical simulation results indicate that the proposed energy flow modeling and optimal operation method are universal and effective over the entire energy dispatching horizon.
International Nuclear Information System (INIS)
Nikolov, Ned; Zeller, Karl F.
2003-01-01
A new biophysical model (FORFLUX) is presented to link ozone deposition with carbon and water cycles in terrestrial ecosystems. - A new biophysical model (FORFLUX) is presented to study the simultaneous exchange of ozone, carbon dioxide, and water vapor between terrestrial ecosystems and the atmosphere. The model mechanistically couples all major processes controlling ecosystem flows trace gases and water implementing recent concepts in plant eco-physiology, micrometeorology, and soil hydrology. FORFLUX consists of four interconnected modules-a leaf photosynthesis model, a canopy flux model, a soil heat-, water- and CO 2 - transport model, and a snow pack model. Photosynthesis, water-vapor flux and ozone uptake at the leaf level are computed by the LEAFC3 sub-model. The canopy module scales leaf responses to a stand level by numerical integration of the LEAFC3 model over canopy leaf area index (LAI). The integration takes into account (1) radiative transfer inside the canopy, (2) variation of foliage photosynthetic capacity with canopy depth, (3) wind speed attenuation throughout the canopy, and (4) rainfall interception by foliage elements. The soil module uses principles of the diffusion theory to predict temperature and moisture dynamics within the soil column, evaporation, and CO 2 efflux from soil. The effect of soil heterogeneity on field-scale fluxes is simulated employing the Bresler-Dagan stochastic concept. The accumulation and melt of snow on the ground is predicted using an explicit energy balance approach. Ozone deposition is modeled as a sum of three fluxes- ozone uptake via plant stomata, deposition to non-transpiring plant surfaces, and ozone flux into the ground. All biophysical interactions are computed hourly while model projections are made at either hourly or daily time step. FORFLUX represents a comprehensive approach to studying ozone deposition and its link to carbon and water cycles in terrestrial ecosystems
Srinivasan, Supramaniam; Velev, Omourtag A.; Parthasathy, Arvind; Manko, David J.; Appleby, A. John
1991-01-01
The development of proton exchange membrane (PEM) fuel cell power plants with high energy efficiencies and high power densities is gaining momentum because of the vital need of such high levels of performance for extraterrestrial (space, underwater) and terrestrial (power source for electric vehicles) applications. Since 1987, considerable progress has been made in achieving energy efficiencies of about 60 percent at a current density of 200 mA/sq cm and high power densities (greater than 1 W/sq cm) in PEM fuel cells with high (4 mg/sq cm) or low (0.4 mg/sq cm) platinum loadings in electrodes. The following areas are discussed: (1) methods to obtain these high levels of performance with low Pt loading electrodes - by proton conductor impregnation into electrodes, localization of Pt near front surface; (2) a novel microelectrode technique which yields electrode kinetic parameters for oxygen reduction and mass transport parameters; (3) demonstration of lack of water transport from anode to cathode; (4) modeling analysis of PEM fuel cell for comparison with experimental results and predicting further improvements in performance; and (5) recommendations of needed research and development for achieving the above goals.
International Nuclear Information System (INIS)
Barrado, J.M.; Blazquez, J.B.; Perez-Navarro, A.; Zurro, B.
1977-01-01
An one-dimensional model to analyze the neutral atoms penetration into a hot plasma has been introduced in order to get the ionic temperature from the energy distribution of the charge exchange neutrals, which is obtained following a Montecarlo procedure. The model enhances the influence of the non homogeneous charge-exchange and temperature profiles over the energy distribution. It also shows haw the inner neutrals are screened by the plasma external layers and the dependence of the effective temperature on the charge-exchange cross section. Results agree with experimental data and with obtained through some others more elaborated models. (author) [es
Modelling of Integrated Renewable Energy System
Akella, A. K.; Saini, R. P.; Sharma, M. P.
2007-10-01
Energy is supplied in the form of electricity, heat or fuels and an energy supply system must guarantee sufficient production and distribution of energy. An energy supply system based on renewable energy can be utilized as integrated renewable energy system (IRES), which can satisfy the energy needs of an area in appropriate & sustainable manner. Given the key role of renewable energy in rural electrification of remote rural areas, the IRES for a given area can be modeled & optimized for meeting the energy needs. In the present paper, Jaunpur block of Uttaranchal state of India has been selected as remote area. Based upon the data collected, the resource potential and energy demand has been calculated & presented. The model on the basis of unit cost of the energy has been optimized using LINDO software 6.10 version. The results indicated that the optimized model has been found to the best choice for meeting the energy needs of the area. The results further indicated that for the above area, either an IRES consisting of the above sources can provide a feasible solution in terms of energy fulfillments in the range of EPDF from 1.0 to 0.75.
World energy projection system: Model documentation
International Nuclear Information System (INIS)
1992-06-01
The World Energy Project System (WEPS) is an accounting framework that incorporates projects from independently documented models and assumptions about the future energy intensity of economic activity (ratios of total energy consumption divided by gross domestic product) and about the rate of incremental energy requirements met by hydropower, geothermal, coal, and natural gas to produce projections of world energy consumption published annually by the Energy Information Administration (EIA) in the International Energy Outlook (IEO) (Figure 1). Two independently documented models presented in Figure 1, the Oil Market Simulation (OMS) model and the World Integrated Nuclear Evaluation System (WINES) provide projections of oil and nuclear power consumption published in the IEO. Output from a third independently documented model, and the International Coal Trade Model (ICTM), is not published in the IEO but is used in WEPS as a supply check on projections of world coal consumption produced by WEPS and published in the IEO. A WEPS model of natural gas production documented in this report provides the same type of implicit supply check on the WEPS projections of world natural gas consumption published in the IEO. Two additional models are included in Figure 1, the OPEC Capacity model and the Non-OPEC Oil Production model. These WEPS models provide inputs to the OMS model and are documented in this report
A cultural model of household energy consumption
International Nuclear Information System (INIS)
Lutzenhiser, Loren
1992-01-01
In this paper, we consider the development of demand-side research, from an early interest in conservation behavior to a later focus on physical, economic, psychological and social models of energy consumption. Unfortunately, none of these models account satisfactorily for measured energy consumption in the residential sector. Growing interest in the end-uses of energy (e.g. in support of load forecasting, demand-side management and least-cost utility planning), increasing international studies of energy use, and continuing work in the energy and lifestyles research tradition now support an emerging cultural perspective on household energy use. The ecological foundations of the cultural model and its applications in energy research are discussed, along with some of the analytic consequences of this approach. (author)
Modeling of renewable hybrid energy sources
Directory of Open Access Journals (Sweden)
Dumitru Cristian Dragos
2009-12-01
Full Text Available Recent developments and trends in the electric power consumption indicate an increasing use of renewable energy. Renewable energy technologies offer the promise of clean, abundant energy gathered from self-renewing resources such as the sun, wind, earth and plants. Virtually all regions of the world have renewable resources of one type or another. By this point of view studies on renewable energies focuses more and more attention. The present paper intends to present different mathematical models related to different types of renewable energy sources such as: solar energy and wind energy. It is also presented the validation and adaptation of such models to hybrid systems working in geographical and meteorological conditions specific to central part of Transylvania region. The conclusions based on validation of such models are also shown.
Modelling energy demand of Croatian industry sector
DEFF Research Database (Denmark)
Medić, Zlatko Bačelić; Pukšec, Tomislav; Mathiesen, Brian Vad
2014-01-01
Industry represents one of the most interesting sectors when analysing Croatian final energy demand. Croatian industry represents 20% of nation's GDP and employs 25% of total labour force making it a significant subject for the economy. Today, with around 60 PJ of final energy demand...... it is the third most energy intensive sector in Croatia after transport and households. Implementing mechanisms that would lead to improvements in energy efficiency in this sector seems relevant. Through this paper, long-term energy demand projections for Croatian industry will be shown. The central point...... for development of the model will be parameters influencing the industry in Croatia. Energy demand predictions in this paper are based upon bottom-up approach model. IED model produces results which can be compared to Croatian National Energy Strategy. One of the conclusions shown in this paper is significant...
Energy Technology Data Exchange (ETDEWEB)
Tso, C.P. [Multimedia University, Jalan Ayer Keroh Lama, Melaka (Malaysia). Faculty of Engineering and Technology; Cheng, Y.C.; Lai, A.C.K. [Nanyang Technological University, Singapore (Singapore). School of Mechanical and Aerospace Engineering
2006-01-15
Frost accumulation on a heat exchanger, a direct result of combined heat and mass transfer between the moist air flowing across a cold surface, causes heat transfer performance degradation due to the insulating effect of frost layer and the coil blockage as the frost grows. The complex geometry of finned tube heat exchangers leads to uneven wall and air temperature distribution inside the coil, and causes variations of frost growth rate and densification along the coil. In this study, a general distributed model with frost formation was developed. The equations for finned tube heat exchanger were derived in non-steady-state manner and quasi-steady state in the frost model. In order to make the model more realistic, the variation of frost along fin due to uneven temperature distribution was included. The presented model is able to predict the dynamic behavior of an air cooler both under non-frost and frost condition. Comparisons were made based on the frost mass accumulation, pressure drop across coil and energy transfer coefficient, and results were found to agree well with reported experimental results. (author)
Dynamic Models of Learning That Characterize Parent-Child Exchanges Predict Vocabulary Growth
Ober, David R.; Beekman, John A.
2016-01-01
Cumulative vocabulary models for infants and toddlers were developed from models of learning that predict trajectories associated with low, average, and high vocabulary growth rates (14 to 46 months). It was hypothesized that models derived from rates of learning mirror the type of exchanges provided to infants and toddlers by parents and…
A computational fluid dynamics model for designing heat exchangers based on natural convection
Dirkse, M.H.; Loon, van W.K.P.; Walle, van der T.; Speetjens, S.L.; Bot, G.P.A.
2006-01-01
A computational fluid dynamics model was created for the design of a natural convection shell-and-tube heat exchanger with baffles. The flow regime proved to be turbulent and this was modelled using the k¿¿ turbulence model. The features of the complex geometry were simplified considerably resulting
COMPARISON OF MATHEMATICAL MODELS FOR HEAT EXCHANGERS OF UNCONVENTIONAL CHP UNITS
Directory of Open Access Journals (Sweden)
Peter Durcansky
2015-08-01
Full Text Available An unconventional CHP unit with a hot air engine is designed as the primary energy source with fuel in the form of biomass. The heat source is a furnace designed for combustion of biomass, whether in the form of wood logs or pellets. The transport of energy generated by the biomass combustion to the working medium of a hot-air engine is ensured by a special heat exchanger connected to this resource. The correct operation of the hot-air engine is largely dependent on an appropriate design of the exchanger. The paper deals with the calculation of the heat exchanger for the applicationsmentioned, using criterion equations, and based on CFD simulations.
Exchange bias and asymmetric hysteresis loops from a microscopic model of core/shell nanoparticles
International Nuclear Information System (INIS)
Iglesias, Oscar; Batlle, Xavier; Labarta, Amilcar
2007-01-01
We present Monte Carlo simulations of hysteresis loops of a model of a magnetic nanoparticle with a ferromagnetic core and an antiferromagnetic shell with varying values of the core/shell interface exchange coupling which aim to clarify the microscopic origin of exchange bias observed experimentally. We have found loop shifts in the field direction as well as displacements along the magnetization axis that increase in magnitude when increasing the interfacial exchange coupling. Overlap functions computed from the spin configurations along the loops have been obtained to explain the origin and magnitude of these features microscopically
Gao, Zhiqiang; Zhang, Wenjiang; Gao, Wei; Chang, Ni-Bin
2009-12-01
Most ecosystems and crops experience water stress in arid and semiarid areas of the Inner Mongolia grassland, Northern China. Yet the lack of long-term in situ monitoring data hinders the managerial capacity of changing water vapor environment, which is tied with sustaining the grassland in the Inner Mongolia. Environmental remote sensing monitoring and modeling may provide synergistic means of observing changes in thermodynamic balance during drought onset at the grassland surface, providing reliable projections accounting for variations and correlations of water vapor and heat fluxes. It is the aim of this paper to present a series of estimates of latent heat, sensible heat, and net radiation using an innovative first-principle, physics-based model (GEOMOD: GEO-model estimated the land surface heat with MODis data) with the aid of integrated satellite remote sensing and in situ eddy covariance data. Based on the energy balance principle and aerodynamics diffusion theory, the GEOMOD model is featured with MODIS (Moderate Resolution Imaging Spectroradiometer) data with 250 m spatial resolution to collectively reflect the spatial heterogeneity of surface properties, supplement missing data with the neighborhood values across both spatial and temporal domains, estimate the surface roughness height and zero-plane displacement with dynamic look-up table, and implement a fast iterative algorithm to calculate sensible heat. Its analytical framework is designed against overreliance on local micro-meteorological parameters. Practical implementation was assessed in the study area, the Xilin Gol River Basin, a typical grassland environment, Northern China. With 179 days of MODIS data in support of modeling, coincident ground-based observations between 2000 and 2006 were selected for model calibration. The findings indicate that GEOMOD performs reasonably well in modeling the land surface heat exchange process, as demonstrated by a case study of Inner Mongolia.
Long Term Validity of Monetary Exchange Rate Model: Evidence from Turkey
Directory of Open Access Journals (Sweden)
Ugur Ahmet
2014-03-01
Full Text Available In this study, it was analyzed if there is a long term relationship among the nominal exchange rate and monetary fundamentals within the periods of 1998:1-2011:2 in Turkey. This relationship has been analysed by using structural VAR (SVAR model. Besides, Granger causality test and Dolado-Lütkepohl Granger causality test were used to determine if there were a causality relationship among the nominal exchange rate and monetary fundamentals. As a result of the SVAR model, the relationship among the series related to nominal exchange rate and money supply, GDP, interest rate in Turkey in long term were not determined and at the end of causality tests, causality relationship among the nominal exchange rate and monetary fundamentals were not determined.
Turning Simulation into Estimation: Generalized Exchange Algorithms for Exponential Family Models.
Directory of Open Access Journals (Sweden)
Maarten Marsman
Full Text Available The Single Variable Exchange algorithm is based on a simple idea; any model that can be simulated can be estimated by producing draws from the posterior distribution. We build on this simple idea by framing the Exchange algorithm as a mixture of Metropolis transition kernels and propose strategies that automatically select the more efficient transition kernels. In this manner we achieve significant improvements in convergence rate and autocorrelation of the Markov chain without relying on more than being able to simulate from the model. Our focus will be on statistical models in the Exponential Family and use two simple models from educational measurement to illustrate the contribution.
A CFD model for the IEA-R1 reactor neat exchanger inlet nozzle flow
Energy Technology Data Exchange (ETDEWEB)
Andrade, Delvonei A.; Angelo, Gabriel; Gainer, Gerson; Angelo, Edvaldo; Umbehaun, Pedro E.; Torres, Walmir M.; Sabundjian, Gaiane; Macedo, Luiz A.; Belchior Junior, Antonio; Conti, Thadeu N.; Watanabe, Bruno C.; Sakai, Caio C., E-mail: delvonei@ipen.b, E-mail: gfainer@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)
2011-07-01
A previous preliminary model of the IEA-R1 heat exchanger inlet nozzle flow was developed and published in the International Nuclear Atlantic Conference-INAC-2009. A new model was created based on the preliminary one. It was improved concerning the actual heat exchanger tube bundle geometry. This became a very special issue. Difficulties with the size of the numerical mesh came out pointing to our computational system limits. New CFD calculations with this improved model were performed using ANSYS-CFX. In this paper, we present this model and discuss the results. (author)
Modeling Energy and Development : An Evaluation of Models and Concepts
Ruijven, Bas van; Urban, Frauke; Benders, René M.J.; Moll, Henri C.; Sluijs, Jeroen P. van der; Vries, Bert de; Vuuren, Detlef P. van
2008-01-01
Most global energy models are developed by institutes from developed countries focusing primarily oil issues that are important in industrialized countries. Evaluation of the results for Asia of the IPCC/SRES models shows that broad concepts of energy and development. the energy ladder and the
Design Fluida Temperature Control in Heat Exchanger using Model Predictive Control Algoritm
Directory of Open Access Journals (Sweden)
Fatimah Ekasari Masturi
2014-03-01
Full Text Available Heat Exchanger merupakan suatu alat proses pertukaran panas, berfungsi untuk memindahkan panas antara dua fluida yang berbeda temperatur dan dipisahkan oleh suatu sekat pemisah. Pada proses perpindahan panas ini terdapat delay time sehingga dibutuhkan suatu kontroller agar diperoleh temperatur fluida sesuai dengan kriteria yang diinginkan, tidak terdapat energi yang terbuang, serta pemanfaatan sumber energi yang tersedia benar-benar dapat lebih efisien. Model Predictive Control (MPC telah berhasil diaplikasikan di berbagai industri proses, karena kemampuannya untuk mengatasi berbagai masalah multivariabel kontrol seperti interaksi, waktu tunda dan batasan. Keuntungan dari MPC karena kedua variabel, yaitu variabel manipulasi dan variabel kontrol, dihitung dengan menggunakan teknik optimasi. Pengendalian terhadap pendekatan linear plant dengan Kontroler MPC menggunakan parameter Hp (prediksi horizon= 20 Hc(kontrol horizon= 4 matriks pembobot Q=1 R=0.1 dapat menghasilkan respon yang stabil tanpa adanya overshoot serta mampu mencapai setpoint yang diinginkan yaitu 70°C, pada beban tetap (nominal ataupun beban bervariasi sekitar 20 % dari beban nominal dengan waktu steady state 35s.
Nikolov, Ned; Zeller, Karl F
2003-01-01
A new biophysical model (FORFLUX) is presented to study the simultaneous exchange of ozone, carbon dioxide, and water vapor between terrestrial ecosystems and the atmosphere. The model mechanistically couples all major processes controlling ecosystem flows trace gases and water implementing recent concepts in plant eco-physiology, micrometeorology, and soil hydrology. FORFLUX consists of four interconnected modules-a leaf photosynthesis model, a canopy flux model, a soil heat-, water- and CO2- transport model, and a snow pack model. Photosynthesis, water-vapor flux and ozone uptake at the leaf level are computed by the LEAFC3 sub-model. The canopy module scales leaf responses to a stand level by numerical integration of the LEAFC3model over canopy leaf area index (LAI). The integration takes into account (1) radiative transfer inside the canopy, (2) variation of foliage photosynthetic capacity with canopy depth, (3) wind speed attenuation throughout the canopy, and (4) rainfall interception by foliage elements. The soil module uses principles of the diffusion theory to predict temperature and moisture dynamics within the soil column, evaporation, and CO2 efflux from soil. The effect of soil heterogeneity on field-scale fluxes is simulated employing the Bresler-Dagan stochastic concept. The accumulation and melt of snow on the ground is predicted using an explicit energy balance approach. Ozone deposition is modeled as a sum of three fluxes- ozone uptake via plant stomata, deposition to non-transpiring plant surfaces, and ozone flux into the ground. All biophysical interactions are computed hourly while model projections are made at either hourly or daily time step. FORFLUX represents a comprehensive approach to studying ozone deposition and its link to carbon and water cycles in terrestrial ecosystems.
Modeling and simulation of the dynamic behavior of portable proton exchange membrane fuel cells
Energy Technology Data Exchange (ETDEWEB)
Ziegler, C.
2005-07-01
In order to analyze the operational behavior, a mathematical model of planar self-breathing fuel cells is developed and validated in Chapter 3 of this thesis. The multicomponent transport of the species is considered as well as the couplings between the transport processes of heat, charge, and mass and the electrochemical reactions. Furthermore, to explain the oxygen mass transport limitation in the porous electrode of the cathode side an agglomerate model for the oxygen reduction reaction is developed. In Chapter 4 the important issue of liquid water generation and transport in PEMFCs is addressed. One of the major tasks when operating this type of fuel cell is avoiding the complete flooding of the PEMFC during operation. A one-dimensional and isothermal model is developed that is based on a coupled system of partial differential equations. The model contains a dynamic and two-phase description of the proton exchange membrane fuel cell. The mass transport in the gas phase and in the liquid phase is considered as well as the phase transition between liquid water and water vapor. The transport of charges and the electrochemical reactions are part of the model. Flooding effects that are caused by liquid water accumulation are described by this model. Moreover, the model contains a time-dependent description of the membrane that accounts for Schroeder's paradox. The model is applied to simulate cyclic voltammograms. Chapter 5 is focused on the dynamic investigation of PEMFC stacks. Understanding the dynamic behavior of fuel cell stacks is important for the operation and control of fuel cell stacks. Using the single cell model of Chapter 3 and the dynamic model of Chapter 4 as basis, a mathematical model of a PEMFC stack is developed. However, due to the complexity of a fuel cell stack, the spatial resolution and dynamic description of the liquid water transport are not accounted for. These restrictions allow for direct comparison between the solution variables of
Modeling of battery energy storage in the National Energy Modeling System
Energy Technology Data Exchange (ETDEWEB)
Swaminathan, S.; Flynn, W.T.; Sen, R.K. [Sentech, Inc., Bethesda, MD (United States)
1997-12-01
The National Energy Modeling System (NEMS) developed by the U.S. Department of Energy`s Energy Information Administration is a well-recognized model that is used to project the potential impact of new electric generation technologies. The NEMS model does not presently have the capability to model energy storage on the national grid. The scope of this study was to assess the feasibility of, and make recommendations for, the modeling of battery energy storage systems in the Electricity Market of the NEMS. Incorporating storage within the NEMS will allow the national benefits of storage technologies to be evaluated.
Modelling of biomass utilization for energy purpose
Energy Technology Data Exchange (ETDEWEB)
Grzybek, Anna (ed.)
2010-07-01
the overall farms structure, farms land distribution on several separate subfields for one farm, villages' overpopulation and very high employment in agriculture (about 27% of all employees in national economy works in agriculture). Farmers have low education level. In towns 34% of population has secondary education and in rural areas - only 15-16%. Less than 2% inhabitants of rural areas have higher education. The structure of land use is as follows: arable land 11.5%, meadows and pastures 25.4%, forests 30.1%. Poland requires implementation of technical and technological progress for intensification of agricultural production. The reason of competition for agricultural land is maintenance of the current consumption level and allocation of part of agricultural production for energy purposes. Agricultural land is going to be key factor for biofuels production. In this publication research results for the Project PL0073 'Modelling of energetical biomass utilization for energy purposes' have been presented. The Project was financed from the Norwegian Financial Mechanism and European Economic Area Financial Mechanism. The publication is aimed at moving closer and explaining to the reader problems connected with cultivations of energy plants and dispelling myths concerning these problems. Exchange of fossil fuels by biomass for heat and electric energy production could be significant input in carbon dioxide emission reduction. Moreover, biomass crop and biomass utilization for energetical purposes play important role in agricultural production diversification in rural areas transformation. Agricultural production widening enables new jobs creation. Sustainable development is going to be fundamental rule for Polish agriculture evolution in long term perspective. Energetical biomass utilization perfectly integrates in the evolution frameworks, especially on local level. There are two facts. The fist one is that increase of interest in energy crops in Poland
Mathematical modelling of thermal and flow processes in vertical ground heat exchangers
Directory of Open Access Journals (Sweden)
Pater Sebastian
2017-12-01
Full Text Available The main task of mathematical modelling of thermal and flow processes in vertical ground heat exchanger (BHE-Borehole Heat Exchanger is to determine the unit of borehole depth heat flux obtainable or transferred during the operation of the installation. This assignment is indirectly associated with finding the circulating fluid temperature flowing out from the U-tube at a given inlet temperature of fluid in respect to other operational parameters of the installation.
A QCD derivation of the additive quark model from two and three gluon exchanges
International Nuclear Information System (INIS)
Lipkin, H.J.
1982-06-01
The contributions to the Pomeron from two and three gluon exchanges are shown to give the correct combinatorial factors for the additive quark model relation between meson and baryon Pomeron couplings, even though two-quark and three-quark operators are involved. Similar results hold for the contributions to hadron masses from three-gluon vertices as well as one-gluon exchange. The color algebra reduces the multiquark couplings to a linear function of quark number. (author)
Model-Driven Energy Intelligence
2015-03-01
Buildings Integrator ECIP Environmental Conservation Investment Program ECM electronically commuted motors EISA Energy Independence and Security Act...FIPS Federal Information Processing Standard HBS Honeywell Building Solutions HQUSACE Headquarters, U.S. Army Corps of Engineers HVAC ...conditioning ( HVAC ) design, root causes for anomalous behavior can be more easily understood. Combined visualizations reveal the behavior of specific
DEFF Research Database (Denmark)
Wendt, Fabian F.; Yu, Yi-Hsiang; Nielsen, Kim
2017-01-01
This is the first joint reference paper for the Ocean Energy Systems (OES) Task 10 Wave Energy Converter modeling verification and validation group. The group is established under the OES Energy Technology Network program under the International Energy Agency. OES was founded in 2001 and Task 10 ...
Evaluating Force-Field London Dispersion Coefficients Using the Exchange-Hole Dipole Moment Model.
Mohebifar, Mohamad; Johnson, Erin R; Rowley, Christopher N
2017-12-12
London dispersion interactions play an integral role in materials science and biophysics. Force fields for atomistic molecular simulations typically represent dispersion interactions by the 12-6 Lennard-Jones potential using empirically determined parameters. These parameters are generally underdetermined, and there is no straightforward way to test if they are physically realistic. Alternatively, the exchange-hole dipole moment (XDM) model from density-functional theory predicts atomic and molecular London dispersion coefficients from first principles, providing an innovative strategy to validate the dispersion terms of molecular-mechanical force fields. In this work, the XDM model was used to obtain the London dispersion coefficients of 88 organic molecules relevant to biochemistry and pharmaceutical chemistry and the values compared with those derived from the Lennard-Jones parameters of the CGenFF, GAFF, OPLS, and Drude polarizable force fields. The molecular dispersion coefficients for the CGenFF, GAFF, and OPLS models are systematically higher than the XDM-calculated values by a factor of roughly 1.5, likely due to neglect of higher order dispersion terms and premature truncation of the dispersion-energy summation. The XDM dispersion coefficients span a large range for some molecular-mechanical atom types, suggesting an unrecognized source of error in force-field models, which assume that atoms of the same type have the same dispersion interactions. Agreement with the XDM dispersion coefficients is even poorer for the Drude polarizable force field. Popular water models were also examined, and TIP3P was found to have dispersion coefficients similar to the experimental and XDM references, although other models employ anomalously high values. Finally, XDM-derived dispersion coefficients were used to parametrize molecular-mechanical force fields for five liquids-benzene, toluene, cyclohexane, n-pentane, and n-hexane-which resulted in improved accuracy in the
Rechargeable Metal-Air Proton-Exchange Membrane Batteries for Renewable Energy Storage.
Nagao, Masahiro; Kobayashi, Kazuyo; Yamamoto, Yuta; Yamaguchi, Togo; Oogushi, Akihide; Hibino, Takashi
2016-02-01
Rechargeable proton-exchange membrane batteries that employ organic chemical hydrides as hydrogen-storage media have the potential to serve as next-generation power sources; however, significant challenges remain regarding the improvement of the reversible hydrogen-storage capacity. Here, we address this challenge through the use of metal-ion redox couples as energy carriers for battery operation. Carbon, with a suitable degree of crystallinity and surface oxygenation, was used as an effective anode material for the metal redox reactions. A Sn 0.9 In 0.1 P 2 O 7 -based electrolyte membrane allowed no crossover of vanadium ions through the membrane. The V 4+ /V 3+ , V 3+ /V 2+ , and Sn 4+ /Sn 2+ redox reactions took place at a more positive potential than that for hydrogen reduction, so that undesired hydrogen production could be avoided. The resulting electrical capacity reached 306 and 258 mAh g -1 for VOSO 4 and SnSO 4 , respectively, and remained at 76 and 91 % of their respective initial values after 50 cycles.
Ding, Zhangwei; Ma, Yaoming; Wen, Zhiping; Ma, Weiqiang; Chen, Shiji
2017-07-01
Banana plantation and alpine meadow ecosystems in southern China and the Tibetan Plateau (TP) are unique in the underlying surfaces they exhibit. In this study, we used eddy covariance and a micrometeorological tower to examine the characteristics of land surface energy exchanges over a banana plantation in southern China and an alpine meadow in the Tibetan Plateau from May 2010 to August 2012. The results showed that the diurnal and seasonal variations in upward shortwave radiation flux and surface soil heat flux were larger over the alpine meadow than over the banana plantation surface. Dominant energy partitioning varied with season. Latent heat flux was the main consumer of net radiation flux in the growing season, whereas sensible heat flux was the main consumer during other periods. The Monin-Obukhov similarity theory was employed for comparative purposes, using sonic anemometer observations of flow over the surfaces of banana plantations in the humid southern China monsoon region and the semi-arid areas of the TP, and was found to be applicable. Over banana plantation and alpine meadow areas, the average surface albedo and surface aerodynamic roughness lengths under neutral atmospheric conditions were ˜0.128 and 0.47 m, and ˜0.223 and 0.01 m, respectively. During the measuring period, the mean annual bulk transfer coefficients for momentum and sensible heat were 1.47 × 10-2 and 7.13 × 10-3, and 2.91 × 10-3 and 1.96 × 10-3, for banana plantation and alpine meadow areas, respectively.
Dark energy observational evidence and theoretical models
Novosyadlyj, B; Shtanov, Yu; Zhuk, A
2013-01-01
The book elucidates the current state of the dark energy problem and presents the results of the authors, who work in this area. It describes the observational evidence for the existence of dark energy, the methods and results of constraining of its parameters, modeling of dark energy by scalar fields, the space-times with extra spatial dimensions, especially Kaluza---Klein models, the braneworld models with a single extra dimension as well as the problems of positive definition of gravitational energy in General Relativity, energy conditions and consequences of their violation in the presence of dark energy. This monograph is intended for science professionals, educators and graduate students, specializing in general relativity, cosmology, field theory and particle physics.
An Experimentally Validated Numerical Modeling Technique for Perforated Plate Heat Exchangers
Nellis, G. F.; Kelin, S. A.; Zhu, W.; Gianchandani, Y.
2010-01-01
Cryogenic and high-temperature systems often require compact heat exchangers with a high resistance to axial conduction in order to control the heat transfer induced by axial temperature differences. One attractive design for such applications is a perforated plate heat exchanger that utilizes high conductivity perforated plates to provide the stream-to-stream heat transfer and low conductivity spacers to prevent axial conduction between the perforated plates. This paper presents a numerical model of a perforated plate heat exchanger that accounts for axial conduction, external parasitic heat loads, variable fluid and material properties, and conduction to and from the ends of the heat exchanger. The numerical model is validated by experimentally testing several perforated plate heat exchangers that are fabricated using microelectromechanical systems based manufacturing methods. This type of heat exchanger was investigated for potential use in a cryosurgical probe. One of these heat exchangers included perforated plates with integrated platinum resistance thermometers. These plates provided in situ measurements of the internal temperature distribution in addition to the temperature, pressure, and flow rate measured at the inlet and exit ports of the device. The platinum wires were deposited between the fluid passages on the perforated plate and are used to measure the temperature at the interface between the wall material and the flowing fluid. The experimental testing demonstrates the ability of the numerical model to accurately predict both the overall performance and the internal temperature distribution of perforated plate heat exchangers over a range of geometry and operating conditions. The parameters that were varied include the axial length, temperature range, mass flow rate, and working fluid. PMID:20976021
An Experimentally Validated Numerical Modeling Technique for Perforated Plate Heat Exchangers.
White, M J; Nellis, G F; Kelin, S A; Zhu, W; Gianchandani, Y
2010-11-01
Cryogenic and high-temperature systems often require compact heat exchangers with a high resistance to axial conduction in order to control the heat transfer induced by axial temperature differences. One attractive design for such applications is a perforated plate heat exchanger that utilizes high conductivity perforated plates to provide the stream-to-stream heat transfer and low conductivity spacers to prevent axial conduction between the perforated plates. This paper presents a numerical model of a perforated plate heat exchanger that accounts for axial conduction, external parasitic heat loads, variable fluid and material properties, and conduction to and from the ends of the heat exchanger. The numerical model is validated by experimentally testing several perforated plate heat exchangers that are fabricated using microelectromechanical systems based manufacturing methods. This type of heat exchanger was investigated for potential use in a cryosurgical probe. One of these heat exchangers included perforated plates with integrated platinum resistance thermometers. These plates provided in situ measurements of the internal temperature distribution in addition to the temperature, pressure, and flow rate measured at the inlet and exit ports of the device. The platinum wires were deposited between the fluid passages on the perforated plate and are used to measure the temperature at the interface between the wall material and the flowing fluid. The experimental testing demonstrates the ability of the numerical model to accurately predict both the overall performance and the internal temperature distribution of perforated plate heat exchangers over a range of geometry and operating conditions. The parameters that were varied include the axial length, temperature range, mass flow rate, and working fluid.
Making work safer: testing a model of social exchange and safety management.
DeJoy, David M; Della, Lindsay J; Vandenberg, Robert J; Wilson, Mark G
2010-04-01
This study tests a conceptual model that focuses on social exchange in the context of safety management. The model hypothesizes that supportive safety policies and programs should impact both safety climate and organizational commitment. Further, perceived organizational support is predicted to partially mediate both of these relationships. Study outcomes included traditional outcomes for both organizational commitment (e.g., withdrawal behaviors) as well as safety climate (e.g., self-reported work accidents). Questionnaire responses were obtained from 1,723 employees of a large national retailer. Using structural equation modeling (SEM) techniques, all of the model's hypothesized relationships were statistically significant and in the expected directions. The results are discussed in terms of social exchange in organizations and research on safety climate. Maximizing safety is a social-technical enterprise. Expectations related to social exchange and reciprocity figure prominently in creating a positive climate for safety within the organization. Copyright 2010 Elsevier Ltd. All rights reserved.
Pion-nucleus double charge exchange and the nuclear shell model
International Nuclear Information System (INIS)
Auerbach, N.; Gibbs, W.R.; Ginocchio, J.N.; Kaufmann, W.B.
1988-01-01
The pion-nucleus double charge exchange reaction is studied with special emphasis on nuclear structure. The reaction mechanism and nuclear structure aspects of the process are separated using both the plane-wave and distorted-wave impulse approximations. Predictions are made employing both the seniority model and a full shell model (with a single active orbit). Transitions to the double analog state and to the ground state of the residual nucleus are computed. The seniority model yields particularly simple relations among double charge exchange cross sections for nuclei within the same shell. Limitations of the seniority model and of the plane-wave impulse approximation are discussed as well as extensions to the generalized seniority scheme. Applications of the foregoing ideas to single charge exchange are also presented
Walch, Stephen P.; Rohlfing, Celeste Mcmichael
1989-01-01
The results of CASSCF multireference contracted CI calculations with large ANO basis sets are presented for the exchange region of the HO2 potential-energy surface. The saddle point for H atom exchange is about 13 kcal/mol below the energy of H + O2; therefore, this region of the surface should be accessible during H + O2 recombination and methathesis reactions.
Computerized mathematical model for the anion exchange processing of plutonium(IV)
International Nuclear Information System (INIS)
Navratil, J.D.; Proctor, S.G.; Kirkby, L.L.
1977-01-01
A computerized mathematical model for anion exchange processing of plutonium(IV) was adopted from a previously written code. The model was verified to predict, within +-30 percent, a profile of plutonium breakthrough for the sorption process on Dowex 1-X4 anion exchange resin. The program was modified to incorporate column washing and elution logic. Experimental washing and elution data were in satisfactory agreement with predicted data. Provisions for changing the flow rate during the course of a run and for plotting capabilities to aid in better presentation of column breakthrough curves also were incorporated into the model
A modified wake oscillator model for predicting vortex induced vibration of heat exchanger tube
International Nuclear Information System (INIS)
Feng Zhipeng; Zang Fenggang; Zhang Yixiong; Ye Xianhui
2014-01-01
Base on the classical wake oscillator model, a new modified wake oscillator model is proposed, for predicting vortex induced vibration of heat exchanger tube in uniform current. The comparison between the new wake oscillator model and experimental show that the present model can simulate the characteristics of vortex induced vibration of tube. Firstly, the research shows that the coupled fluid-structure dynamical system should be modeled by combined displacement and acceleration mode. Secondly, the empirical parameter in wake oscillator model depends on the material properties of the structure, instead of being a universal constant. Lastly, the results are compared between modified wake oscillator model and fluid-structure interaction numerical model. It shows the present, predicted results are compared to the fluid-structure interaction numerical data. The new modified wake oscillator model can predict the vortex induced heat exchanger tube vibration feasibly. (authors)
Energy based prediction models for building acoustics
DEFF Research Database (Denmark)
Brunskog, Jonas
2012-01-01
In order to reach robust and simplified yet accurate prediction models, energy based principle are commonly used in many fields of acoustics, especially in building acoustics. This includes simple energy flow models, the framework of statistical energy analysis (SEA) as well as more elaborated...... principles as, e.g., wave intensity analysis (WIA). The European standards for building acoustic predictions, the EN 12354 series, are based on energy flow and SEA principles. In the present paper, different energy based prediction models are discussed and critically reviewed. Special attention is placed...... on underlying basic assumptions, such as diffuse fields, high modal overlap, resonant field being dominant, etc., and the consequences of these in terms of limitations in the theory and in the practical use of the models....
Towards increased policy relevance in energy modeling
Energy Technology Data Exchange (ETDEWEB)
Worrell, Ernst; Ramesohl, Stephan; Boyd, Gale
2003-07-29
Historically, most energy models were reasonably equipped to assess the impact of a subsidy or change in taxation, but are often insufficient to assess the impact of more innovative policy instruments. We evaluate the models used to assess future energy use, focusing on industrial energy use. We explore approaches to engineering-economic analysis that could help improve the realism and policy relevance of engineering-economic modeling frameworks. We also explore solutions to strengthen the policy usefulness of engineering-economic analysis that can be built from a framework of multi-disciplinary cooperation. We focus on the so-called ''engineering-economic'' (or ''bottom-up'') models, as they include the amount of detail that is commonly needed to model policy scenarios. We identify research priorities for the modeling framework, technology representation in models, policy evaluation and modeling of decision-making behavior.
Extraproximal approach to calculating equilibriums in pure exchange models
Antipin, A. S.
2006-10-01
Models of economic equilibrium are a powerful tool of mathematical modeling of various markets. However, according to many publications, there are as yet no universal techniques for finding equilibrium prices that are solutions to such models. A technique of this kind that is a natural implementation of the Walras idea of tatonnements (i.e., groping for equilibrium prices) is proposed, and its convergence is proved.
Modeling energy fluxes in heterogeneous landscapes employing a mosaic approach
Klein, Christian; Thieme, Christoph; Priesack, Eckart
2015-04-01
Recent studies show that uncertainties in regional and global climate and weather simulations are partly due to inadequate descriptions of the energy flux exchanges between the land surface and the atmosphere. One major shortcoming is the limitation of the grid-cell resolution, which is recommended to be about at least 3x3 km² in most models due to limitations in the model physics. To represent each individual grid cell most models select one dominant soil type and one dominant land use type. This resolution, however, is often too coarse in regions where the spatial diversity of soil and land use types are high, e.g. in Central Europe. An elegant method to avoid the shortcoming of grid cell resolution is the so called mosaic approach. This approach is part of the recently developed ecosystem model framework Expert-N 5.0. The aim of this study was to analyze the impact of the characteristics of two managed fields, planted with winter wheat and potato, on the near surface soil moistures and on the near surface energy flux exchanges of the soil-plant-atmosphere interface. The simulated energy fluxes were compared with eddy flux tower measurements between the respective fields at the research farm Scheyern, North-West of Munich, Germany. To perform these simulations, we coupled the ecosystem model Expert-N 5.0 to an analytical footprint model. The coupled model system has the ability to calculate the mixing ratio of the surface energy fluxes at a given point within one grid cell (in this case at the flux tower between the two fields). This approach accounts for the differences of the two soil types, of land use managements, and of canopy properties due to footprint size dynamics. Our preliminary simulation results show that a mosaic approach can improve modeling and analyzing energy fluxes when the land surface is heterogeneous. In this case our applied method is a promising approach to extend weather and climate models on the regional and on the global scale.
International Nuclear Information System (INIS)
Shrier, O; Khachan, J; Bosi, S
2006-01-01
A Markov chain method is presented as an alternative approach to Monte Carlo simulations of charge exchange collisions by an energetic hydrogen ion beam with a cold background hydrogen gas. This method was used to determine the average energy of the resulting energetic neutrals along the path of the beam. A comparison with Monte Carlo modelling showed a good agreement but with the advantage that it required much less computing time and produced no numerical noise. In particular, the Markov chain method works well for monotonically increasing or decreasing electrostatic potentials. Finally, a good agreement is obtained with experimental results from Doppler shift spectroscopy on energetic beams from a hollow cathode discharge. In particular, the average energy of ions that undergo charge exchange reaches a plateau that can be well below the full energy that might be expected from the applied voltage bias, depending on the background gas pressure. For example, pressures of ∼20 mTorr limit the ion energy to ∼20% of the applied voltage
Lang, Katharina M H; Kittelmann, Jörg; Dürr, Cathrin; Osberghaus, Anna; Hubbuch, Jürgen
2015-02-13
In downstream processing, the underlying adsorption mechanism of biomolecules to adsorbent material are still subject of extensive research. One approach to more mechanistic understanding is simulating this adsorption process and hereby the possibility to identify the parameters with strongest impact. So far this method was applied with all-atom molecular dynamics simulations of two model proteins on one cation exchanger. In this work we developed a molecular dynamics tool to simulate protein-adsorber interaction for various proteins on an anion exchanger and ran gradient elution experiments to relate the simulation results to experimental data. We were able to show that simulation results yield similar results as experimental data regarding retention behavior as well as binding orientation. We could identify arginines in case of cation exchangers and aspartic acids in case of anion exchangers as major contributors to binding. Copyright © 2015 Elsevier B.V. All rights reserved.
Study of exchange current contributions for the pion-deuteron scattering at intermediate energies
International Nuclear Information System (INIS)
Melo, S.W.A. de.
1983-01-01
The contribution of the pions exchange currents to the πd elastic scattering in the Δ(1232) resonance region is calculated using Feynman diagrams. The results show that the addition of exchange currents to the simple and double scattering terms improve the agreement with the experimental data. (L.C.) [pt
Co-simulation and Dynamic Model Exchange with Consideration for Wind Projects
Cvetkovic, M.; López Torres, C.D.; Bhandia, R.; Rueda Torres, José L.; Palensky, P.; Betancourt, Uta; Ackermann, Thomas
2017-01-01
This paper discusses and compares two approaches to address technical challenges in performing collaborative studies of power system dynamics. On one side, we consider the model migration approach which is an essential piece of dynamic model exchange. On the other side, we look at the co-simulation
A one-dimensional heat transfer model for parallel-plate thermoacoustic heat exchangers
de Jong, Anne; Wijnant, Ysbrand H.; de Boer, Andries
2014-01-01
A one-dimensional (1D) laminar oscillating flow heat transfer model is derived and applied to parallel-plate thermoacoustic heat exchangers. The model can be used to estimate the heat transfer from the solid wall to the acoustic medium, which is required for the heat input/output of thermoacoustic
Sridhar, Upasana Manimegalai; Govindarajan, Anand; Rhinehart, R Russell
2016-01-01
This work reveals the applicability of a relatively new optimization technique, Leapfrogging, for both nonlinear regression modeling and a methodology for nonlinear model-predictive control. Both are relatively simple, yet effective. The application on a nonlinear, pilot-scale, shell-and-tube heat exchanger reveals practicability of the techniques. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.
The Monetary Exchange Rate Model as a Long-Run Phenomenon
J.J.J. Groen (Jan)
1998-01-01
textabstractPure time series-based tests fail to find empirical support for monetary exchange rate models. In this paper we apply pooled time series estimation on a forward-looking monetary model, resulting in parameter estimates which are in compliance with the underlying theory. Based on a panel
Numerical Modeling of Fin and Tube Heat Exchanger for Waste Heat Recovery
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph
In the present work, multiphysics numerical modeling is carried out to predict the performance of a liquid-gas fin and tube heat exchanger design. Three-dimensional (3D) steady-state numerical model using commercial software COMSOL based on finite element method (FEM) is developed. The study...
Model-based fault detection for proton exchange membrane fuel cell ...
African Journals Online (AJOL)
In this paper, an intelligent model-based fault detection (FD) is developed for proton exchange membrane fuel cell (PEMFC) dynamic systems using an independent radial basis function (RBF) networks. The novelty is that this RBF networks is used to model the PEMFC dynamic systems and residuals are generated based ...
Energy models for commercial energy prediction and substitution of renewable energy sources
International Nuclear Information System (INIS)
Iniyan, S.; Suganthi, L.; Samuel, Anand A.
2006-01-01
In this paper, three models have been projected namely Modified Econometric Mathematical (MEM) model, Mathematical Programming Energy-Economy-Environment (MPEEE) model, and Optimal Renewable Energy Mathematical (OREM) model. The actual demand for coal, oil and electricity is predicted using the MEM model based on economic, technological and environmental factors. The results were used in the MPEEE model, which determines the optimum allocation of commercial energy sources based on environmental limitations. The gap between the actual energy demand from the MEM model and optimal energy use from the MPEEE model, has to be met by the renewable energy sources. The study develops an OREM model that would facilitate effective utilization of renewable energy sources in India, based on cost, efficiency, social acceptance, reliability, potential and demand. The economic variations in solar energy systems and inclusion of environmental constraint are also analyzed with OREM model. The OREM model will help policy makers in the formulation and implementation of strategies concerning renewable energy sources in India for the next two decades
Seasonal and inter-annual variability of energy exchange above a boreal Scots pine forest
Directory of Open Access Journals (Sweden)
S. Launiainen
2010-12-01
Full Text Available Twelve-years of eddy-covariance measurements conducted above a boreal Scots pine forest in Hyytiälä, Southern Finland, were analyzed to assess the seasonal and inter-annual variability of surface conductance (g_{s} and energy partitioning. The g_{s} had distinct annual course, driven by the seasonal cycle of the Scots pine. Low g_{s} (2–3 mm s^{−1} in April cause the sensible heat flux to peak in May–June while evapotranspiration takes over later in July–August when g_{s} is typically 5–7 mm s^{−1}. Hence, during normal years Bowen ratio decreases from 4–6 in April to 0.7–0.9 in August. Sensitivity of g_{s} to ambient vapor pressure deficit (D was relatively constant but the reference value at D = 1 kPa varied seasonally and between years. Only two drought episodes when volumetric soil moisture content in upper mineral soil decreased below 0.15 m^{3} m^{−3} occurred during the period. Below this threshold value, transpiration was strongly reduced, which promoted sensible heat exchange increasing Bowen ratio to 3–4. Annual evapotranspiration varied between 218 and 361 mm and accounted between 50% and 90% of equilibrium evaporation. The forest floor contributed between 16 and 25% of the total evapotranspiration on annual scale. The fraction stayed similar over the observed range of environmental conditions including drought periods. The inter-annual variability of evapotranspiration could not be linked to any mean climate variable while the summertime sensible heat flux and net radiation were well explained by global radiation. The energy balance closure varied annually between 0.66 and 0.95 and had a distinct seasonal cycle with worse closure in spring when a large proportion of available energy is partitioned into sensible heat.
Modeling Conflict And Exchange In Collective Decision Making
Stokman, Frans N.
1995-01-01
Two dynamic models of collecuve decision maklng are Introduced and lllustrated wlth a simple example. A more extensive presentation and appllcauon concerning the European Community can be found In Bueno de Mesqulta and Stokman (19941. The two dynamlc models reflect two alternative views of
Jana, Subrata; Patra, Abhilash; Samal, Prasanjit
2018-03-01
Semilocal exchange-correlation functionals are frequently used to accurately describe the complex many-electron effects of two-dimensional quantum systems. Most of these functionals are designed using the reduced density gradient as the main ingredient. A semilocal functional for the exchange and the corresponding enhancement factor is constructed using the inhomogeneity parameter of the generalized gradient approximations by analyzing the small and large-density gradient expansion of the exchange hole. This exchange functional significantly reduces the error compared to the existing gradient approximations. Performance of the proposed semilocal functional is demonstrated by considering parabolic and Gaussian quantum dots with varying particle number and confinement strength. The results are also compared with that of the exact exchange formalism by considering it as the standard.
Modelling energy utilisation in broiler breeder hens.
Rabello, C B V; Sakomura, N K; Longo, F A; Couto, H P; Pacheco, C R; Fernandes, J B K
2006-10-01
1. The objective of this study was to determine a metabolisable energy (ME) requirement model for broiler breeder hens. The influence of temperature on ME requirements for maintenance was determined in experiments conducted in three environmental rooms with temperatures kept constant at 13, 21 and 30 degrees C using a comparative slaughter technique. The energy requirements for weight gain were determined based upon body energy content and efficiency of energy utilisation for weight gain. The energy requirements for egg production were determined on the basis of egg energy content and efficiency of energy deposition in the eggs. 2. The following model was developed using these results: ME = kgW0.75(806.53-26.45T + 0.50T2) + 31.90G + 10.04EM, where kgW0.75 is body weight (kg) raised to the power 0.75, T is temperature ( degrees C), G is weight gain (g) and EM is egg mass (g). 3. A feeding trial was conducted using 400 Hubbard Hi-Yield broiler breeder hens and 40 Peterson males from 31 to 46 weeks of age in order to compare use of the model with a recommended feeding programme for this strain of bird. The application of the model in breeder hens provided good productive and reproductive performance and better results in feed and energy conversion than in hens fed according to strain recommendation. In conclusion, the model evaluated predicted an ME intake which matched breeder hens' requirements.
Energy Technology Data Exchange (ETDEWEB)
NONE
2001-03-01
For the purpose of surveying the situation of the arrangement of methods of energy conservation promotion and the emissions trading system in developing countries by Japan having the effectiveness or in cooperation with developed countries, information was collected through the participation in international conferences related to energy conservation promotion, etc. and by visits at governmental organizations in charge in developed countries and developing countries. The results of the survey were classified into the following four items: 1) survey method; 2) exchanges of information on energy conservation in main 3 developing counties; 3) exchanges of information of energy conservation in the main developed countries; 4) exchanges of information of the emissions trading system (international trading system of energy conservation values (greenhouse effect gas emission right)). In 4), survey was made on the following: the emissions trading system for the inside of company group (BP-Amoco), the details of the emissions trading system for one country (the U.K.), the grapple with the emissions trading by a private trading organization (NATSOURCE Co.), and the handle with the emissions trading system by each of the OECD countries. (NEDO)
Multiphysics Model of Palladium Hydride Isotope Exchange Accounting for Higher Dimensionality
Energy Technology Data Exchange (ETDEWEB)
Gharagozloo, Patricia E.; Eliassi, Mehdi; Bon, Bradley Luis
2015-03-01
This report summarizes computational model developm ent and simulations results for a series of isotope exchange dynamics experiments i ncluding long and thin isothermal beds similar to the Foltz and Melius beds and a lar ger non-isothermal experiment on the NENG7 test bed. The multiphysics 2D axi-symmetr ic model simulates the temperature and pressure dependent exchange reactio n kinetics, pressure and isotope dependent stoichiometry, heat generation from the r eaction, reacting gas flow through porous media, and non-uniformities in the bed perme ability. The new model is now able to replicate the curved reaction front and asy mmetry of the exit gas mass fractions over time. The improved understanding of the exchange process and its dependence on the non-uniform bed properties and te mperatures in these larger systems is critical to the future design of such sy stems.
Activity systems modeling as a theoretical lens for social exchange studies
Directory of Open Access Journals (Sweden)
Ernest Jones
2016-01-01
Full Text Available The social exchange perspective seeks to acknowledge, understand and predict the dynamics of social interactions. Empirical research involving social exchange constructs have grown to be highly technical including confirmatory factor analysis to assess construct distinctiveness and structural equation modeling to assess construct causality. Each study seemingly strives to assess how underlying social exchange theoretic constructs interrelate. Yet despite this methodological depth and resultant explanatory and predictive power, a significant number of studies report findings that, once synthesized, suggest an underlying persistent threat of conceptual or construct validity brought about by a search for epistemological parsimony. Further, it is argued that a methodological approach that embraces inherent complexity such as activity systems modeling facilitates the search for simplified models while not ignoring contextual factors.
Modeling gas exchange in a closed plant growth chamber
Cornett, J. D.; Hendrix, J. E.; Wheeler, R. M.; Ross, C. W.; Sadeh, W. Z.
1994-01-01
Fluid transport models for fluxes of water vapor and CO2 have been developed for one crop of wheat and three crops of soybean grown in a closed plant growth chamber. Correspondence among these fluxes is discussed. Maximum fluxes of gases are provided for engineering design requirements of fluid recycling equipment in growth chambers. Furthermore, to investigate the feasibility of generalized crop models, dimensionless representations of water vapor fluxes are presented. The feasibility of such generalized models and the need for additional data are discussed.
Cognata, Thomas; Leimkuehler, Thomas; Ramaswamy, Balasubramaniam; Nayagam, Vedha; Hasan, Mohammad; Stephan, Ryan
2011-01-01
Water affords manifold benefits for human space exploration. Its properties make it useful for the storage of thermal energy as a Phase Change Material (PCM) in thermal control systems, in radiation shielding against Solar Particle Events (SPE) for the protection of crew members, and it is indisputably necessary for human life support. This paper envisions a single application for water which addresses these benefits for future exploration support vehicles and it describes recent experimental and modeling work that has been performed in order to arrive at a description of the thermal behavior of such a system. Experimental units have been developed and tested which permit the evaluation of the many parameters of design for such a system with emphasis on the latent energy content, temperature rise, mass, and interstitial material geometry. The experimental results are used to develop a robust and well correlated model which is intended to guide future design efforts toward the multi-purposed water PCM heat exchanger envisioned.
An energy balance climate model with cloud feedbacks
Roads, J. O.; Vallis, G. K.
1984-01-01
The present two-level global climate model, which is based on the atmosphere-surface energy balance, includes physically based parameterizations for the exchange of heat and moisture across latitude belts and between the surface and the atmosphere, precipitation and cloud formation, and solar and IR radiation. The model field predictions obtained encompass surface and atmospheric temperature, precipitation, relative humidity, and cloudiness. In the model integrations presented, it is noted that cloudiness is generally constant with changing temperature at low latitudes. High altitude cloudiness increases with temperature, although the cloud feedback effect on the radiation field remains small because of compensating effects on thermal and solar radiation. The net global feedback by the cloud field is negative, but small.
Schneider, P. A.; Bustos, A.; Hennequin, P.; Ryter, F.; Bernert, M.; Cavedon, M.; Dunne, M. G.; Fischer, R.; Görler, T.; Happel, T.; Igochine, V.; Kurzan, B.; Lebschy, A.; McDermott, R. M.; Morel, P.; Willensdorfer, M.; the ASDEX Upgrade Team; The EUROfusion MST1 Team
2017-06-01
In ASDEX Upgrade (AUG), the normalised gyroradius {ρ\\star} was varied via a hydrogen isotope scan while keeping other dimensionless parameters constant. This was done in L-mode, to minimise the impact of pedestal stability on confinement. Power balance and perturbative transport analyses reveal that the electron heat transport is unaffected by the differences in isotope mass. Nonlinear simulations with the Gene code suggest that these L-mode discharges are ion temperature gradient (ITG) dominated. The different gyroradii due to the isotope mass do not necessarily result in a change of the predicted heat fluxes. This result is used in simulations with the Astra transport code to match the experimental profiles. In these simulations the experimental profiles and confinement times are reproduced with the same transport coefficients for hydrogen and deuterium plasmas. The mass only enters in the energy exchange term between electrons and ions. These numerical observations are supported by additional experiments which show a lower ion energy confinement compared to that of the electrons. Additionally, hydrogen and deuterium plasmas have a similar confinement when the energy exchange time between electrons and ions is matched. This strongly suggests that the observed isotope dependence in L-mode is not dominated by a gyroradius effect, but a consequence of the mass dependence in the collisional energy exchange between electrons and ions.
International Nuclear Information System (INIS)
Perdew, John P.; Ruzsinszky, Adrienn; Tao, Jianmin; Csonka, Gabor I.; Scuseria, Gustavo E.
2007-01-01
The meta-generalized-gradient-approximation (meta-GGA) for the exchange-correlation energy, as constructed by Tao, Perdew, Staroverov, and Scuseria (TPSS) [Phys. Rev. Lett. 91, 146401 (2003)], has achieved usefully consistent accuracy for diverse systems and is the most reliable nonempirical density functional (and the most reliable nonhybrid) in common use. We present here an optimized version of this TPSS functional obtained by empirically fitting a single free parameter that controls the approach of the exchange enhancement factor to its rapidly-varying-density limit, while preserving all the exact constraints that the original TPSS functional satisfies. We find that molecular atomization energies are significantly improved with the optimized version and are even better than those obtained with the best hybrid functionals employing a fraction of exact exchange (e.g., the TPSS hybrid), while energy barrier heights are slightly improved; jellium surface energies remain accurate and almost unchanged. The one-parameter freedom of the TPSS functional may be useful even beyond the meta-GGA level, since the TPSS approximation is a natural starting point for the higher-level hyper-GGA
Impacts of Model Building Energy Codes
Energy Technology Data Exchange (ETDEWEB)
Athalye, Rahul A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sivaraman, Deepak [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Elliott, Douglas B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Liu, Bing [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bartlett, Rosemarie [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2016-10-31
The U.S. Department of Energy (DOE) Building Energy Codes Program (BECP) periodically evaluates national and state-level impacts associated with energy codes in residential and commercial buildings. Pacific Northwest National Laboratory (PNNL), funded by DOE, conducted an assessment of the prospective impacts of national model building energy codes from 2010 through 2040. A previous PNNL study evaluated the impact of the Building Energy Codes Program; this study looked more broadly at overall code impacts. This report describes the methodology used for the assessment and presents the impacts in terms of energy savings, consumer cost savings, and reduced CO_{2} emissions at the state level and at aggregated levels. This analysis does not represent all potential savings from energy codes in the U.S. because it excludes several states which have codes which are fundamentally different from the national model energy codes or which do not have state-wide codes. Energy codes follow a three-phase cycle that starts with the development of a new model code, proceeds with the adoption of the new code by states and local jurisdictions, and finishes when buildings comply with the code. The development of new model code editions creates the potential for increased energy savings. After a new model code is adopted, potential savings are realized in the field when new buildings (or additions and alterations) are constructed to comply with the new code. Delayed adoption of a model code and incomplete compliance with the code’s requirements erode potential savings. The contributions of all three phases are crucial to the overall impact of codes, and are considered in this assessment.
World Energy Projection System model documentation
International Nuclear Information System (INIS)
Hutzler, M.J.; Anderson, A.T.
1997-09-01
The World Energy Projection System (WEPS) was developed by the Office of Integrated Analysis and Forecasting within the Energy Information Administration (EIA), the independent statistical and analytical agency of the US Department of Energy. WEPS is an integrated set of personal computer based spreadsheets containing data compilations, assumption specifications, descriptive analysis procedures, and projection models. The WEPS accounting framework incorporates projections from independently documented models and assumptions about the future energy intensity of economic activity (ratios of total energy consumption divided by gross domestic product GDP), and about the rate of incremental energy requirements met by natural gas, coal, and renewable energy sources (hydroelectricity, geothermal, solar, wind, biomass, and other renewable resources). Projections produced by WEPS are published in the annual report, International Energy Outlook. This report documents the structure and procedures incorporated in the 1998 version of the WEPS model. It has been written to provide an overview of the structure of the system and technical details about the operation of each component of the model for persons who wish to know how WEPS projections are produced by EIA
Energy and development : A modelling approach
van Ruijven, B.J.|info:eu-repo/dai/nl/304834521
2008-01-01
Rapid economic growth of developing countries like India and China implies that these countries become important actors in the global energy system. Examples of this impact are the present day oil shortages and rapidly increasing emissions of greenhouse gases. Global energy models are used explore
Directory of energy information administration models 1995
Energy Technology Data Exchange (ETDEWEB)
NONE
1995-07-13
This updated directory has been published annually; after this issue, it will be published only biennially. The Disruption Impact Simulator Model in use by EIA is included. Model descriptions have been updated according to revised documentation approved during the past year. This directory contains descriptions about each model, including title, acronym, purpose, followed by more detailed information on characteristics, uses, and requirements. Sources for additional information are identified. Included are 37 EIA models active as of February 1, 1995. The first group is the National Energy Modeling System (NEMS) models. The second group is all other EIA models that are not part of NEMS. Appendix A identifies major EIA modeling systems and the models within these systems. Appendix B is a summary of the `Annual Energy Outlook` Forecasting System.
A macro-physics model of depreciation rate in economic exchange
Marmont Lobo, Rui F.; de Sousa, Miguel Rocha
2014-02-01
This article aims at a new approach for a known fundamental result: barter or trade increases economic value. It successfully bridges the gap between the theory of value and the exchange process attached to the transition from endowments to the equilibrium in the core and contract curve. First, we summarise the theory of value; in Section 2, we present the Edgeworth (1881) box and an axiomatic approach and in Section 3, we apply our pure exchange model. Finally (in Section 4), using our open econo-physics pure barter (EPB) model, we derive an improvement in value, which means that pure barter leads to a decline in depreciation rate.
Goyal, Mukesh; Chakravarty, Anindya; Atrey, M. D.
2017-03-01
Experimental investigations are carried out using a specially developed three-layer plate fin heat exchanger (PFHE), with helium as the working fluid cooled to cryogenic temperatures using liquid nitrogen (LN2) as a coolant. These results are used for validation of an already proposed and reported numerical model based on finite volume analysis for multistream (MS) plate fin heat exchangers (PFHE) for cryogenic applications (Goyal et al., 2014). The results from the experiments are presented and a reasonable agreement is observed with the already reported numerical model.
Directory of Open Access Journals (Sweden)
Oreiro José Luis
2015-01-01
Full Text Available The aim of this paper is to show at theoretical level that maintaining a competitive real exchange rate positively affects the economic growth of developing countries by means of a Keynesian-Structuralist model that combines elements of Kaleckian growth models with the balance of payments constrained growth models pioneered developed by Thirlwall. In this setting, the level of real exchange rate is capable, due to its effect over capital accumulation, to induce a structural change in the economy, making endogenous income elasticities of exports and imports. For reasonable parameter values it is shown that in steady-state growth there is two long-run equilibrium values for real exchange rate, one that corresponds to an under-valued currency and another that corresponds to an over-valued currency. If monetary authorities run exchange rate policy in order to target a competitive level for real exchange rate, than under-valued equilibrium is stable and the economy will show a high growth rate in the long-run.
Modelling the energy transition in cities
Energy Technology Data Exchange (ETDEWEB)
Huber, Felix [Wuppertal Univ. (Germany). Dept. of Civil Engineering; Schwarze, Bjoern; Spiekermann, Klaus; Wegener, Michael [Spiekermann und Wegener Urban and Regional Research, Dortmund (Germany)
2013-09-01
The history of cities is a history of energy transitions. In the medieval city heating and cooking occurred with wood and peat. The growth of the industrial city in the 19th century was built on coal and electricity. The sprawling metropolis of the 20th century was made possible by oil and gas. How will the city of the 21st century look after the next energy transition from fossil to renewable energy? This paper reports on the extension of an urban land-use transport interaction model to a model of the energy transition in the Ruhr Area, a five-million agglomeration in Germany. The paper presents the planned model extensions and how they are to be integrated into the model and shows first preliminary results.
Medlyn, Belinda E; Robinson, Andrew P; Clement, Robert; McMurtrie, Ross E
2005-07-01
With the widespread application of eddy covariance technology, long-term records of hourly ecosystem mass and energy exchange are becoming available for forests around the world. These data sets hold great promise for testing and validation of models of forest function. However, model validation is not a straightforward task. The goals of this paper were to: (1) review some of the problems inherent in model validation; and (2) survey the tools available to modelers to improve validation procedures, with particular reference to eddy covariance data. A simple set of models applied to a data set of ecosystem CO2 exchange is used to illustrate our points. The major problems discussed are equifinality, insensitivity and uncertainty. Equifinality is the problem that different models, or different parameterizations of the same model, may yield similar results, making it difficult to distinguish which is correct. Insensitivity arises because the major sources of variation in eddy covariance data are the annual and diurnal cycles, which are represented by even the most basic models, and the size of the response to these cycles can mask effects of other driving variables. Uncertainty arises from three main sources: parameters, model structure and data, each of which is discussed in turn. Uncertainty is a particular issue with eddy covariance data because of the lack of replicated measurements and the potential for unquantified systematic errors such as flux loss due to advection. We surveyed several tools that improve model validation, including sensitivity analysis, uncertainty analysis, residual analysis and model comparison. Illustrative examples are used to demonstrate the use of each tool. We show that simplistic comparisons of model outputs with eddy covariance data are problematic, but use of these tools can greatly improve our confidence in model predictions.
Stochastic effects in a discretized kinetic model of economic exchange
Bertotti, M. L.; Chattopadhyay, A. K.; Modanese, G.
2017-04-01
Linear stochastic models and discretized kinetic theory are two complementary analytical techniques used for the investigation of complex systems of economic interactions. The former employ Langevin equations, with an emphasis on stock trade; the latter is based on systems of ordinary differential equations and is better suited for the description of binary interactions, taxation and welfare redistribution. We propose a new framework which establishes a connection between the two approaches by introducing random fluctuations into the kinetic model based on Langevin and Fokker-Planck formalisms. Numerical simulations of the resulting model indicate positive correlations between the Gini index and the total wealth, that suggest a growing inequality with increasing income. Further analysis shows, in the presence of a conserved total wealth, a simultaneous decrease in inequality as social mobility increases, in conformity with economic data.
NLP model and stochastic multi-start optimization approach for heat exchanger networks
International Nuclear Information System (INIS)
Núñez-Serna, Rosa I.; Zamora, Juan M.
2016-01-01
Highlights: • An NLP model for the optimal design of heat exchanger networks is proposed. • The NLP model is developed from a stage-wise grid diagram representation. • A two-phase stochastic multi-start optimization methodology is utilized. • Improved network designs are obtained with different heat load distributions. • Structural changes and reductions in the number of heat exchangers are produced. - Abstract: Heat exchanger network synthesis methodologies frequently identify good network structures, which nevertheless, might be accompanied by suboptimal values of design variables. The objective of this work is to develop a nonlinear programming (NLP) model and an optimization approach that aim at identifying the best values for intermediate temperatures, sub-stream flow rate fractions, heat loads and areas for a given heat exchanger network topology. The NLP model that minimizes the total annual cost of the network is constructed based on a stage-wise grid diagram representation. To improve the possibilities of obtaining global optimal designs, a two-phase stochastic multi-start optimization algorithm is utilized for the solution of the developed model. The effectiveness of the proposed optimization approach is illustrated with the optimization of two network designs proposed in the literature for two well-known benchmark problems. Results show that from the addressed base network topologies it is possible to achieve improved network designs, with redistributions in exchanger heat loads that lead to reductions in total annual costs. The results also show that the optimization of a given network design sometimes leads to structural simplifications and reductions in the total number of heat exchangers of the network, thereby exposing alternative viable network topologies initially not anticipated.
Integrated hydrologic and hydrodynamic modeling to assess water exchange in a data-scarce reservoir
Wu, Binbin; Wang, Guoqiang; Wang, Zhonggen; Liu, Changming; Ma, Jianming
2017-12-01
Integrated hydrologic and hydrodynamic modeling is useful in evaluating hydrodynamic characteristics (e.g. water exchange processes) in data-scarce water bodies, however, most studies lack verification of the hydrologic model. Here, water exchange (represented by water age) was investigated through integrated hydrologic and hydrodynamic modeling of the Hongfeng Reservoir, a poorly gauged reservoir in southwest China. The performance of the hydrologic model and parameter replacement among sub-basins with hydrological similarity was verified by historical data. Results showed that hydrological similarity based on the hierarchical cluster analysis and topographic index probability density distribution was reliable with satisfactory performance of parameter replacement. The hydrodynamic model was verified using daily water levels and water temperatures from 2009 and 2010. The water exchange processes in the Hongfeng Reservoir are very complex with temporal, vertical, and spatial variations. The temporal water age was primarily controlled by the variable inflow and outflow, and the maximum and minimum ages for the site near the dam were 406.10 d (15th June) and 90.74 d (3rd August), respectively, in 2010. Distinct vertical differences in water age showed that surface flow, interflow, and underflow appeared alternately, depending on the season and water depth. The worst water exchange situation was found in the central areas of the North Lake with the highest water ages in the bottom on both 15th June and 3rd August, in 2010. Comparison of the spatial water ages revealed that the more favorable hydraulic conditions on 3rd August mainly improved the water exchange in the dam areas and most areas of the South Lake, but had little effect on the bottom layers of the other deepest areas in the South and North Lakes. The presented framework can be applied in other data-scarce waterbodies worldwide to provide better understanding of water exchange processes.
A computational model of insect discontinuous gas exchange: A two-sensor, control systems approach.
Grieshaber, Beverley J; Terblanche, John S
2015-06-07
The insect gas exchange system is characterised by branching air-filled tubes (tracheae/tracheoles) and valve-like structures in their outer integument (spiracles) which allow for a periodic gas exchange pattern known as the discontinuous gas exchange cycle (DGC). The DGC facilitates the temporal decoupling of whole animal gas exchange from cellular respiration rates and may confer several physiological benefits, which are nevertheless highly controversial (primarily reduction of cellular oxidative damage and/or respiratory water saving). The intrinsic and extrinsic factors influencing DGCs are the focus of extensive ongoing research and little consensus has been reached on the evolutionary genesis or mechanistic costs and benefits of the pattern. Despite several hypotheses and much experimental and evolutionary biology research, a mechanistic physical model, which captures various key elements of the DGC pattern, is currently lacking. Here, we present a biologically realistic computational, two-sensor DGC model (pH/carbon dioxide and oxygen setpoints) for an Orthopteran gas exchange system, and show computationally for the first time that a control system of two interacting feedback loops is capable of generating a full DGC pattern with outputs which are physiologically realistic, quantitatively matching experimental results found in this taxonomic model elsewhere. A finite-element mathematical approach is employed and various trigger sets are considered. Parameter sensitivity analyses suggest that various aspects of insect DGC are adequately captured in this model. In particular, with physiologically relevant input parameters, the full DGC pattern is induced; and the phase durations, endotracheal carbon dioxide partial pressure ranges, and pH fluctuations which arise are physically realistic. The model results support the emergent property hypothesis for the existence of DGC, and indicate that asymmetric loading and off-loading (hysteresis) in one of the sensor
International Nuclear Information System (INIS)
Yoon, Seok; Lee, Seung-Rae; Xue, Jianfeng; Zosseder, Kai; Go, Gyu-Hyun; Park, Hyunku
2015-01-01
Highlights: • We performed field TPT with W and coil-type GHEs in energy piles. • We evaluated heat exchange rates from TPT results. • Field TPT results were compared with numerical analysis. • Cost analysis with GSHP design method was conducted for each type of GHEs in energy piles. - Abstract: This paper presents an experimental and numerical study of the results of a thermal performance test using precast high-strength concrete (PHC) energy piles with W and coil-type ground heat exchangers (GHEs). In-situ thermal performance tests (TPTs) were conducted for four days under an intermittent operation condition (8 h on; 16 h off) on W and coil-type PHC energy piles installed in a partially saturated weathered granite soil deposit. In addition, three-dimensional finite element analyses were conducted and the results were compared with the four-day experimental results. The heat exchange rates were also predicted for three months using the numerical analysis. The heat exchange rate of the coil-type GHE showed 10–15% higher efficiency compared to the W-type GHE in the energy pile. However, in considering the cost for the installation of the heat exchanger and cement grouting the additional cost of W-type GHE in energy pile was 200–250% cheaper than coil-type GHE under the condition providing equivalent thermal performance. Furthermore, the required lengths of the W, 3U and coil-type GHEs in the energy piles were calculated based on the design process of Kavanaugh and Rafferty. The additional cost for the W and 3U types of GHEs were also 200–250% lower than that of the coil-type GHE. However, the required number of piles was much less with the coil-type GHE as compared to the W and 3U types of GHEs. They are advantageous in terms of the construction period, and further, selecting the coil-type GHE could be a viable option when there is a limitation in the number of piles in consideration of the scale of the building.
A Model for Trading the Foreign Exchange Market
African Journals Online (AJOL)
PROF. OLIVER OSUAGWA
The predictions from the networks are integrated to get the direction of price movement. Market sentiment and volatility values are combined with the neural network prediction to develop trading strategies using Marcov chain. Finally, an application of the model in FOREX trading is demonstrated and implemented with the ...
Xia, Xinhui; Zhu, Changrong; Luo, Jingshan; Zeng, Zhiyuan; Guan, Cao; Ng, Chin Fan; Zhang, Hua; Fan, Hong Jin
2014-02-26
Metal sulfides are an emerging class of high-performance electrode materials for solar cells and electrochemical energy storage devices. Here, a facile and powerful method based on anion exchange reactions is reported to achieve metal sulfide nanoarrays through a topotactical transformation from their metal oxide and hydroxide preforms. Demonstrations are made to CoS and NiS nanowires, nanowalls, and core-branch nanotrees on carbon cloth and nickel foam substrates. The sulfide nanoarrays exhibit superior redox reactivity for electrochemical energy storage. The self-supported CoS nanowire arrays are tested as the pseudo-capacitor cathode, which demonstrate enhanced high-rate specific capacities and better cycle life as compared to the powder counterparts. The outstanding electrochemical properties of the sulfide nanoarrays are a consequence of the preservation of the nanoarray architecture and rigid connection with the current collector after the anion exchange reactions.
Teaching model: Energy. 3. rev. ed.
International Nuclear Information System (INIS)
1979-01-01
The model attempts to give a picture of the energy situation and the problems connected with the various energy sources. An 'energy syllabus' is obtained which deals mostly with energy industry and sociopolitical aspects. The material is for teaching from 9th grade onwards; it may be used for socio-economic projects at upper secondary. The book is considered as an attempt at a critical discussion and a better understanding of this important field of economy and, at that, our lives. (orig./HP) [de
DEFF Research Database (Denmark)
Bjerg, Poul Løgstrup; Ammentorp, Hans Christian; Christensen, Thomas Højlund
1993-01-01
A large-scale and long-term field experiment on cation exchange in a sandy aquifer has been modelled by a three-dimensional geochemical transport model. The geochemical model includes cation-exchange processes using a Gaines-Thomas expression, the closed carbonate system and the effects of ionic...... by batch experiments and by the composition of the cations on the exchange complex. Potassium showed a non-ideal exchange behaviour with K&z.sbnd;Ca selectivity coefficients indicating dependency on equivalent fraction and K+ concentration in the aqueous phase. The model simulations over a distance of 35 m...
Atmosphere-soil-vegetation model including CO2 exchange processes: SOLVEG2
International Nuclear Information System (INIS)
Nagai, Haruyasu
2004-11-01
A new atmosphere-soil-vegetation model named SOLVEG2 (SOLVEG version 2) was developed to study the heat, water, and CO 2 exchanges between the atmosphere and land-surface. The model consists of one-dimensional multilayer sub-models for the atmosphere, soil, and vegetation. It also includes sophisticated processes for solar and long-wave radiation transmission in vegetation canopy and CO 2 exchanges among the atmosphere, soil, and vegetation. Although the model usually simulates only vertical variation of variables in the surface-layer atmosphere, soil, and vegetation canopy by using meteorological data as top boundary conditions, it can be used by coupling with a three-dimensional atmosphere model. In this paper, details of SOLVEG2, which includes the function of coupling with atmosphere model MM5, are described. (author)
Directory of Open Access Journals (Sweden)
Chang-Sei eKim
2016-02-01
Full Text Available The goal of this study is to derive a minimally complex but credible model of respiratory CO2 gas exchange that may be used in systematic design and pilot testing of closed-loop end-tidal CO2 controllers in mechanical ventilation. We first derived a candidate model that captures the essential mechanisms involved in the respiratory CO2 gas exchange process. Then, we simplified the candidate model to derive two lower-order candidate models. We compared these candidate models for predictive capability and reliability using experimental data collected from 25 pediatric subjects undergoing dynamically varying mechanical ventilation during surgical procedures. A two-compartment model equipped with transport delay to account for CO2 delivery between the lungs and the tissues showed modest but statistically significant improvement in predictive capability over the same model without transport delay. Aggregating the lungs and the tissues into a single compartment further degraded the predictive fidelity of the model. In addition, the model equipped with transport delay demonstrated superior reliability to the one without transport delay. Further, the respiratory parameters derived from the model equipped with transport delay, but not the one without transport delay, were physiologically plausible. The results suggest that gas transport between the lungs and the tissues must be taken into account to accurately reproduce the respiratory CO2 gas exchange process under conditions of wide-ranging and dynamically varying mechanical ventilation conditions.
Modeling Innovations Advance Wind Energy Industry
2009-01-01
In 1981, Glenn Research Center scientist Dr. Larry Viterna developed a model that predicted certain elements of wind turbine performance with far greater accuracy than previous methods. The model was met with derision from others in the wind energy industry, but years later, Viterna discovered it had become the most widely used method of its kind, enabling significant wind energy technologies-like the fixed pitch turbines produced by manufacturers like Aerostar Inc. of Westport, Massachusetts-that are providing sustainable, climate friendly energy sources today.
Thermal modeling and optimization of a thermally matched energy harvester
Boughaleb, J.; Arnaud, A.; Cottinet, P. J.; Monfray, S.; Gelenne, P.; Kermel, P.; Quenard, S.; Boeuf, F.; Guyomar, D.; Skotnicki, T.
2015-08-01
The interest in energy harvesting devices has grown with the development of wireless sensors requiring small amounts of energy to function. The present article addresses the thermal investigation of a coupled piezoelectric and bimetal-based heat engine. The thermal energy harvester in question converts low-grade heat flows into electrical charges by achieving a two-step conversion mechanism for which the key point is the ability to maintain a significant thermal gradient without any heat sink. Many studies have previously focused on the electrical properties of this innovative device for energy harvesting but until now, no thermal modeling has been able to describe the device specificities or improve its thermal performances. The research reported in this paper focuses on the modeling of the harvester using an equivalent electrical circuit approach. It is shown that the knowledge of the thermal properties inside the device and a good comprehension of its heat exchange with the surrounding play a key role in the optimization procedure. To validate the thermal modeling, finite element analyses as well as experimental measurements on a hot plate were carried out and the techniques were compared. The proposed model provided a practical guideline for improving the generator design to obtain a thermally matched energy harvester that can function over a wide range of hot source temperatures for the same bimetal. A direct application of this study has been implemented on scaled structures to maintain an important temperature difference between the cold surface and the hot reservoir. Using the equations of the thermal model, predictions of the thermal properties were evaluated depending on the scaling factor and solutions for future thermal improvements are presented.
Pan-Arctic modelling of net ecosystem exchange of CO2
Shaver, G. R.; Rastetter, E. B.; Salmon, V.; Street, L. E.; van de Weg, M. J.; Rocha, A.; van Wijk, M. T.; Williams, M.
2013-01-01
Net ecosystem exchange (NEE) of C varies greatly among Arctic ecosystems. Here, we show that approximately 75 per cent of this variation can be accounted for in a single regression model that predicts NEE as a function of leaf area index (LAI), air temperature and photosynthetically active radiation (PAR). The model was developed in concert with a survey of the light response of NEE in Arctic and subarctic tundras in Alaska, Greenland, Svalbard and Sweden. Model parametrizations based on data...
Pujol, Josep M.; Flache, Andreas; Delgado, Jordi; Sangüesa, Ramon; Sanguessa, R.
2005-01-01
Small-world and power-law network structures have been prominently proposed as models of large networks. However, the assumptions of these models usually-lack sociological grounding. We present a computational model grounded in social exchange theory. Agents search attractive exchange partners in a
Langevin model of low-energy fission
Sierk, Arnold J.
2017-09-01
Background: Since the earliest days of fission, stochastic models have been used to describe and model the process. For a quarter century, numerical solutions of Langevin equations have been used to model fission of highly excited nuclei, where microscopic potential-energy effects have been neglected. Purpose: In this paper I present a Langevin model for the fission of nuclei with low to medium excitation energies, for which microscopic effects in the potential energy cannot be ignored. Method: I solve Langevin equations in a five-dimensional space of nuclear deformations. The macroscopic-microscopic potential energy from a global nuclear structure model well benchmarked to nuclear masses is tabulated on a mesh of approximately 107 points in this deformation space. The potential is defined continuously inside the mesh boundaries by use of a moving five-dimensional cubic spline approximation. Because of reflection symmetry, the effective mesh is nearly twice this size. For the inertia, I use a (possibly scaled) approximation to the inertia tensor defined by irrotational flow. A phenomenological dissipation tensor related to one-body dissipation is used. A normal-mode analysis of the dynamical system at the saddle point and the assumption of quasiequilibrium provide distributions of initial conditions appropriate to low excitation energies, and are extended to model spontaneous fission. A dynamical model of postscission fragment motion including dynamical deformations and separation allows the calculation of final mass and kinetic-energy distributions, along with other interesting quantities. Results: The model makes quantitative predictions for fragment mass and kinetic-energy yields, some of which are very close to measured ones. Varying the energy of the incident neutron for induced fission allows the prediction of energy dependencies of fragment yields and average kinetic energies. With a simple approximation for spontaneous fission starting conditions
DEFF Research Database (Denmark)
Charalampidis, C.; Van As, D.; Box, J. E.
2015-01-01
negative surface mass budget (SMB) and surface meltwater run-off. The observed run-off was due to a large ice fraction in the upper 10 m of firn that prevented meltwater from percolating to available pore volume below. Analysis reveals an anomalously low 2012 summer-averaged albedo of 0.71 (typically ∼ 0...... energy fluxes. The model reproduces the observed melt rates as well as the SMB for each season. A sensitivity analysis reveals that 71 % of the additional solar radiation in 2012 was used for melt, corresponding to 36 % (0.64 m) of the 2012 surface lowering. The remaining 64 % (1.14 m) of surface...
International Nuclear Information System (INIS)
Xing, Lei; Du, Shangfeng; Chen, Rui; Mamlouk, Mohamed; Scott, Keith
2016-01-01
A two-dimensional along-the-channel CFD (computational fluid dynamic) model, coupled with a two-phase flow model of liquid water and gas transport for a PEM (proton exchange membrane) fuel cell is described. The model considers non-isothermal operation and thus the non-uniform temperature distribution in the cell structure. Water phase-transfer between the vapour, liquid water and dissolved phase is modelled with the combinational transport mechanism through the membrane. Liquid water saturation is simulated inside the electrodes and channels at both the anode and cathode sides. Three types of models are compared for the HOR (hydrogen oxidation reaction) and ORR (oxygen reduction reaction) in catalyst layers, including Butler–Volmer (B–V), liquid water saturation corrected B–V and agglomerate mechanisms. Temperature changes in MEA (membrane electrode assembly) and channels due to electrochemical reaction, ohmic resistance and water phase-transfer are analysed as a function of current density. Nonlinear relations of liquid water saturations with respect to current densities at both the anode and cathode are regressed. At low and high current densities, liquid water saturation at the anode linearly increases as a consequence of the linear increase of liquid water saturation at the cathode. In contrast, exponential relation is found to be more accurate at medium current densities. - Highlights: • A fully coupled 2D, along-the-channel, two-phase flow, non-isothermal, CFD model is developed. • Temperature rise due to electrochemical reactions, ohmic resistance and water phase-transfer is analysed. • Mathematical expressions of liquid water saturation against current density at anode and cathode are regressed. • Relationship between the liquid water saturation at anode and cathode is built.
International Nuclear Information System (INIS)
PERG (University of Palermo, Physics Education Research Group) Dipartimento di Fisica e Chimica, Università di Palermo, Palermo (Italy))" data-affiliation=" (UOPPERG (University of Palermo, Physics Education Research Group) Dipartimento di Fisica e Chimica, Università di Palermo, Palermo (Italy))" >Pizzolato, Nicola; PERG (University of Palermo, Physics Education Research Group) Dipartimento di Fisica e Chimica, Università di Palermo, Palermo (Italy))" data-affiliation=" (UOPPERG (University of Palermo, Physics Education Research Group) Dipartimento di Fisica e Chimica, Università di Palermo, Palermo (Italy))" >Fazio, Claudio; PERG (University of Palermo, Physics Education Research Group) Dipartimento di Fisica e Chimica, Università di Palermo, Palermo (Italy))" data-affiliation=" (UOPPERG (University of Palermo, Physics Education Research Group) Dipartimento di Fisica e Chimica, Università di Palermo, Palermo (Italy))" >Battaglia, Onofrio Rosario
2014-01-01
An open inquiry (OI)-based teaching/learning experience, regarding a scientific investigation of the process of energy exchange by thermal radiation, is presented. A sample of upper secondary school physics teachers carried out this experience at the University of Palermo, Italy, in the framework of ESTABLISH, a FP7 European Project aimed at promoting and developing inquiry-based science education. The teachers had the opportunity to personally experience an OI-based learning activity, with the aim of exploring the pedagogical potentialities of this teaching approach to promote both the understanding of difficult concepts and a deeper view of scientific practices. The teachers were firstly engaged in discussions concerning real-life problematic situations, and then stimulated to design and carry out their own laboratory activities, aimed at investigating the process of energy exchange by thermal radiation. A scientific study on the energy exchange between a powered resistor and its surrounding environment, during the heating and cooling processes, was designed and performed. Here we report the phases of this experiment by following the teachers' perspective. A structured interview conducted both before and after the OI experience allowed us to analyze and point out the teachers' feedback from a pedagogical point of view. The advantages and limits of an OI-based approach to promote the development of more student-centred inquiry-oriented teaching strategies are finally discussed. (paper)
Energy Technology Data Exchange (ETDEWEB)
VanKuiken, J.C.; Veselka, T.D.; Guziel, K.A.; Blodgett, D.W.; Hamilton, S.; Kavicky, J.A.; Koritarov, V.S.; North, M.J.; Novickas, A.A.; Paprockas, K.R. [and others
1994-11-01
This report describes operating procedures and background documentation for the Argonne Production, Expansion, and Exchange Model for Electrical Systems (APEX). This modeling system was developed to provide the U.S. Department of Energy, Division of Fossil Energy, Office of Coal and Electricity with in-house capabilities for addressing policy options that affect electrical utilities. To meet this objective, Argonne National Laboratory developed a menu-driven programming package that enables the user to develop and conduct simulations of production costs, system reliability, spot market network flows, and optimal system capacity expansion. The APEX system consists of three basic simulation components, supported by various databases and data management software. The components include (1) the investigation of Costs and Reliability in Utility Systems (ICARUS) model, (2) the Spot Market Network (SMN) model, and (3) the Production and Capacity Expansion (PACE) model. The ICARUS model provides generating-unit-level production-cost and reliability simulations with explicit recognition of planned and unplanned outages. The SMN model addresses optimal network flows with recognition of marginal costs, wheeling charges, and transmission constraints. The PACE model determines long-term (e.g., longer than 10 years) capacity expansion schedules on the basis of candidate expansion technologies and load growth estimates. In addition, the Automated Data Assembly Package (ADAP) and case management features simplify user-input requirements. The ADAP, ICARUS, and SMN modules are described in detail. The PACE module is expected to be addressed in a future publication.
Holographic dark energy in the DGP model
International Nuclear Information System (INIS)
Cruz, Norman; Lepe, Samuel; Pena, Francisco; Avelino, Arturo
2012-01-01
The braneworld model proposed by Dvali, Gabadadze, and Porrati leads to an accelerated universe without cosmological constant or any other form of dark energy. Nevertheless, we have investigated the consequences of this model when an holographic dark energy is included, taking the Hubble scale as IR cutoff. We have found that the holographic dark energy leads to an accelerated flat universe (de Sitter-like expansion) for the two branches: ε=±1, of the DGP model. Nevertheless, in universes with no null curvature the dark energy presents an EoS corresponding to a phantom fluid during the present era and evolving to a de Sitter-like phase for future cosmic time. In the special case in which the holographic parameter c is equal to one we have found a sudden singularity in closed universes. In this case the expansion is decelerating. (orig.)
Holographic dark energy in the DGP model
Energy Technology Data Exchange (ETDEWEB)
Cruz, Norman [Universidad de Santiago, Departamento de Fisica, Facultad de Ciencia, Santiago (Chile); Lepe, Samuel [Pontificia Universidad Catolica de Valparaiso, Instituto de Fisica, Facultad de Ciencias, Valparaiso (Chile); Pena, Francisco [Universidad de La Frontera, Departamento de Ciencias Fisicas, Facultad de Ingenieria, Ciencias y Administracion, Avda. Francisco Salazar 01145, Casilla 54-D, Temuco (Chile); Avelino, Arturo [Universidad de Guanajuato, Departamento de Fisica, DCI, Codigo Postal 37150, Leon, Guanajuato (Mexico)
2012-09-15
The braneworld model proposed by Dvali, Gabadadze, and Porrati leads to an accelerated universe without cosmological constant or any other form of dark energy. Nevertheless, we have investigated the consequences of this model when an holographic dark energy is included, taking the Hubble scale as IR cutoff. We have found that the holographic dark energy leads to an accelerated flat universe (de Sitter-like expansion) for the two branches: {epsilon}={+-}1, of the DGP model. Nevertheless, in universes with no null curvature the dark energy presents an EoS corresponding to a phantom fluid during the present era and evolving to a de Sitter-like phase for future cosmic time. In the special case in which the holographic parameter c is equal to one we have found a sudden singularity in closed universes. In this case the expansion is decelerating. (orig.)
Modelling of proton and metal exchange in the alginate biopolymer.
De Stefano, Concetta; Gianguzza, Antonio; Piazzese, Daniela; Sammartano, Silvio
2005-10-01
Acid-base behaviour of a commercial sodium alginate extracted from brown seaweed (Macrocystis pyrifera) has been investigated at different ionic strengths (0.1titration calorimetric data were expressed as a function of the dissociation degree (alpha) using different models (Henderson-Hasselbalch modified, Högfeldt three parameters and linear equations). The dependence on ionic strength of the protonation constants was taken into account by a modified specific interaction theory model. Differences among different media were explained in terms of the interaction between polyanion and metal cations of the supporting electrolytes. Quantitative information on the proton-binding capacity, together with the stabilities of different species formed, is reported. Protonation thermodynamic parameters, at alpha=0.5, are log K H=3.686+/-0.005, DeltaG 0=-21.04+/-0.03 kJ mol(-1), DeltaH 0=4.8+/-0.2 kJ mol(-1) and TDeltaS 0=35.7+/-0.3 kJ mol(-1), at infinite dilution. Protonation enthalpies indicate that the main contribution to proton binding arises from the entropy term. A strict correlation between DeltaG and TDeltaS was found, TDeltaS=-9.5-1.73 DeltaG. Results are reported in light of building up a chemical complexation model of general validity to explain the binding ability of naturally occurring polycarboxylate polymers and biopolymers. Speciation profiles of alginate in the presence of sodium and magnesium ions, naturally occurring cations in natural waters, are also reported.
Modeling shoreline bioremediation: Continuous flow and seawater exchange columns
International Nuclear Information System (INIS)
Ramstad, S.; Sveum, P.; Bech, C.; Faksness, L.G.
1995-01-01
This paper describes the design and use of the columns in the study of bioremediation processes, and gives some results from an experiment designed to study the effects of different additives (fish meal, stick water, and Max Bac) on biodegradation of crude oil. There is significant difference in oil degradation(nC 17 /pristane ratio) between the column with additives and those without. Open system models in this type of open column give valuable data o how the chemical and biological parameters, including oil degradation, are affected by the additives, and simultaneously by the dilutive effect of seawater washing through the sediment, and for optimizing formulations. The system is designed with a large number of units and provides a good first approximation for mesocosm studies and field experiments, thus reducing the need for large numbers of such resource-demanding experiments
Equity and Foreign Exchange Hybrid Models for Pricing Long-Maturity Financial Derivatives
Grzelak, L.A.
2011-01-01
Modelling derivative products in Finance usually starts with the specification of a system of Stochastic Differential Equations (SDEs), that corresponds to state variables like stock, interest rate, Foreign Exchange (FX) rate and volatility. By correlating the SDEs for the different asset classes
Residential air exchange rates (AERs) are a key determinant in the infiltration of ambient air pollution indoors. Population-based human exposure models using probabilistic approaches to estimate personal exposure to air pollutants have relied on input distributions from AER meas...
Pan-Arctic modelling of net ecosystem exchange of CO2
Shaver, G.R.; Rastetter, E.B.; Salmon, V.; Street, L.E.; Weg, van de M.J.; Rocha, A.; Wijk, van M.T.; Williams, M.
2013-01-01
Net ecosystem exchange (NEE) of C varies greatly among Arctic ecosystems. Here, we show that approximately 75 per cent of this variation can be accounted for in a single regression model that predicts NEE as a function of leaf area index (LAI), air temperature and photosynthetically active radiation
Energy Technology Data Exchange (ETDEWEB)
Ninokata, H. [Tokyo Institute of Technology (Japan); Deguchi, A. [ENO Mathematical Analysis, Tokyo (Japan); Kawahara, A. [Kumamoto Univ., Kumamoto (Japan)
1995-09-01
A new void drift model for the subchannel analysis method is presented for the thermohydraulics calculation of two-phase flows in rod bundles where the flow model uses a two-fluid formulation for the conservation of mass, momentum and energy. A void drift model is constructed based on the experimental data obtained in a geometrically simple inter-connected two circular channel test sections using air-water as working fluids. The void drift force is assumed to be an origin of void drift velocity components of the two-phase cross-flow in a gap area between two adjacent rods and to overcome the momentum exchanges at the phase interface and wall-fluid interface. This void drift force is implemented in the cross flow momentum equations. Computational results have been successfully compared to experimental data available including 3x3 rod bundle data.
Terrestrial magnetospheric imaging: Numerical modeling of low energy neutral atoms
International Nuclear Information System (INIS)
Moore, K.R.; Funsten, H.O.; McComas, D.J.; Scime, E.E.; Thomsen, M.F.
1993-01-01
Imaging of the terrestrial magnetosphere can be performed by detection of low energy neutral atoms (LENAs) that are produced by charge exchange between magnetospheric plasma ions and cold neutral atoms of the Earth's geocorona. As a result of recent instrumentation advances it is now feasible to make energy-resolved measurements of LENAs from less than I key to greater than 30 key. To model expected LENA fluxes at a spacecraft, we initially used a simplistic, spherically symmetric magnetospheric plasma model. 6 We now present improved calculations of both hydrogen and oxygen line-of-sight LENA fluxes expected on orbit for various plasma regimes as predicted by the Rice University Magnetospheric Specification Model. We also estimate expected image count rates based on realistic instrument geometric factors, energy passbands, and image accumulation intervals. The results indicate that presently proposed LENA instruments are capable of imaging of storm time ring current and potentially even quiet time ring current fluxes, and that phenomena such as ion injections from the tail and subsequent drifts toward the dayside magnetopause may also be deduced
A Meta Model for Domestic Energy Consumption
Directory of Open Access Journals (Sweden)
K.,J SREEKANTH
2011-01-01
Full Text Available Prediction of energy consumption particularly in micro level is of vital importance in terms of energy planning and also implementation of any Clean Development Mechanism (CDM activities that has become the order of the world today. It may be difficult to model household energy consumption using conventional methods such as time series forecasting due to many influencing factors. This paper presents a step wise regression model for forecasting domestic energy consumption based on micro level household survey data collected from Kerala, a state in southern part of India. The analysis of the data reveals significant influence of socio-economic, demographic, geographic, and family attributes upon total household energy requirements. While a wide variation in the pattern of energy requirements across the domestic sector belonging to different expenditure classes, per capita income level can be identified as the most important explanatory variable influencing variation in energy requirements. The models developed also demonstrates the influence of per capita land area, residential area among the higher income group while average age and literacy forms significant variables among the lower income group.
Improved diagnostic model for estimating wind energy
Energy Technology Data Exchange (ETDEWEB)
Endlich, R.M.; Lee, J.D.
1983-03-01
Because wind data are available only at scattered locations, a quantitative method is needed to estimate the wind resource at specific sites where wind energy generation may be economically feasible. This report describes a computer model that makes such estimates. The model uses standard weather reports and terrain heights in deriving wind estimates; the method of computation has been changed from what has been used previously. The performance of the current model is compared with that of the earlier version at three sites; estimates of wind energy at four new sites are also presented.
Interacting Dark Energy Models and Observations
Shojaei, Hamed; Urioste, Jazmin
2017-01-01
Dark energy is one of the mysteries of the twenty first century. Although there are candidates resembling some features of dark energy, there is no single model describing all the properties of dark energy. Dark energy is believed to be the most dominant component of the cosmic inventory, but a lot of models do not consider any interaction between dark energy and other constituents of the cosmic inventory. Introducing an interaction will change the equation governing the behavior of dark energy and matter and creates new ways to explain cosmic coincidence problem. In this work we studied how the Hubble parameter and density parameters evolve with time in the presence of certain types of interaction. The interaction serves as a way to convert dark energy into matter to avoid a dark energy-dominated universe by creating new equilibrium points for the differential equations. Then we will use numerical analysis to predict the values of distance moduli at different redshifts and compare them to the values for the distance moduli obtained by WMAP (Wilkinson Microwave Anisotropy Probe). Undergraduate Student
Yuan, F.; Thornton, P. E.; McGuire, A. D.; Oechel, W. C.; Yang, B.; Tweedie, C. E.; Rogers, A.; Norby, R. J.
2013-12-01
Bryophyte cover is greater than 50% in many Arctic tundra ecosystems. In regions of the Arctic where shrubs are expanding it is expected that bryophyte cover will be substantially reduced. Such a loss in cover could influence the hydrological, biogeochemical, and permafrost dynamics of Arctic tundra ecosystems. The explicit representation of bryophyte physiological and biophysical processes in large-scale ecological and land surface models is rare, and we hypothesize that the representation of bryophytes has consequences for estimates of the exchange of water, energy, and carbon by these models. This study explicitly represents the effects of bryophyte function and structure on the exchange of carbon (e.g., summer photosynthesis effects) and energy (e.g., summer insulation effects) with the atmosphere in the Community Land Model (CLM-CN). The modified model was evaluated for its ability to simulate C exchange, soil temperature, and soil moisture since the 1970s at Barrow, Alaska through comparison with data from AmeriFlux sites, USDA Soil Climate Networks observation sites at Barrow, and other sources. We also compare the outputs of the CLM-CN simulations with those of the recently developed Dynamical Organic Soil coupled Terrestrial Ecosystem Model (DOS-TEM). Overall, our evaluation indicates that bryophytes are important contributors to land-atmospheric C exchanges in Arctic tundra and that they play an important role to permafrost thermal and hydrological processes which are critical to permafrost stability. Our next step in this study is to examine the climate system effects of explicitly representing bryophyte dynamics in the land surface model. Key Words: Bryophytes, Arctic coastal tundra, Vegetation composition, Net Ecosystem Exchange, Permafrost, Land Surface Model, Terrestrial Ecosystem Model
Rate equation modelling of the optically pumped spin-exchange source
International Nuclear Information System (INIS)
Stenger, J.; Rith, K.
1995-01-01
Sources for spin polarized hydrogen or deuterium, polarized via spin-exchange of a laser optically pumped alkali metal, can be modelled by rate equations. The rate equations for this type of source, operated either with hydrogen or deuterium, are given explicitly with the intention of providing a useful tool for further source optimization and understanding. Laser optical pumping of alkali metal, spin-exchange collisions of hydrogen or deuterium atoms with each other and with alkali metal atoms are included, as well as depolarization due to flow and wall collisions. (orig.)
Electric dipole moment of the top quark in Higgs-boson-exchange models of CP nonconservation
International Nuclear Information System (INIS)
Soni, A.; Xu, R.M.
1992-01-01
The leading contribution to the electric and the chromoelectric dipole moments of the top quark is calculated in Higgs-boson-exchange models of CP nonconservation. The dipole moments are typically of the order of 10 -20 e cm and 10 -20 g cm, respectively and arise at one-loop order through neutral-Higgs-boson exchange. Several two-loop contributions are estimated to be smaller by about 2 orders of magnitude for the electric case and about 1 order of magnitude smaller for the chromoelectric case. The q 2 dependence of the dipole moment form factor is given for possible application to experimental searches
Charge Exchange in Low-Energy H, D + C4+ Collisions with Full Account of Electron Translation
Directory of Open Access Journals (Sweden)
N. Vaeck
2002-03-01
Full Text Available We report the application of the quantum approach, which takes full account of electron translation at low collisional energies, to the charge exchange process H, D + C4+ Ã¢Â†Â’ H+, D+ + C3+(3s; 3p; 3d. The partial and the total integral cross sections of the process are calculated in the energy range from 1 till 60 eV/amu. It is shown that the present results are independent from the upper integration limit for numerical solution of the coupled channel equations although nonadiabatic couplings remain nonzero up to infinity. The calculated partial and total cross sections are in agreement with the previous low-energy calculations and the available experimental data. It is shown that for low collisional energies the isotopic effect takes place. The observed effect is explained in terms of the nonadiabatic dynamics.
Active heat exchange system development for latent heat thermal energy storage
Lefrois, R. T.; Mathur, A. K.
1980-01-01
Five tasks to select, design, fabricate, test and evaluate candidate active heat exchanger modules for future applications to solar and conventional utility power plants were discussed. Alternative mechanizations of active heat exchange concepts were analyzed for use with heat of fusion phase change materials (PCMs) in the temperature range of 250 to 350 C. Twenty-six heat exchange concepts were reviewed, and eight were selected for detailed assessment. Two candidates were selected for small-scale experimentation: a coated tube and shell heat exchanger and a direct contact reflux boiler. A dilute eutectic mixture of sodium nitrate and sodium hydroxide was selected as the PCM from over 50 candidate inorganic salt mixtures. Based on a salt screening process, eight major component salts were selected initially for further evaluation. The most attractive major components in the temperature range of 250 to 350 C appeared to be NaNO3, NaNO2, and NaOH. Sketches of the two active heat exchange concepts selected for test are given.
Baldwin, Darryl Dean; Willi, Martin Leo; Fiveland, Scott Byron; Timmons, Kristine Ann
2010-12-14
A segmented heat exchanger system for transferring heat energy from an exhaust fluid to a working fluid. The heat exchanger system may include a first heat exchanger for receiving incoming working fluid and the exhaust fluid. The working fluid and exhaust fluid may travel through at least a portion of the first heat exchanger in a parallel flow configuration. In addition, the heat exchanger system may include a second heat exchanger for receiving working fluid from the first heat exchanger and exhaust fluid from a third heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the second heat exchanger in a counter flow configuration. Furthermore, the heat exchanger system may include a third heat exchanger for receiving working fluid from the second heat exchanger and exhaust fluid from the first heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the third heat exchanger in a parallel flow configuration.
Energy laboratory data and model directory
Lahiri, S.; Carson, J.
1981-07-01
Over the past several years M.I.T. faculty, staff, and students have produced a substantial body of research and analysis relating to the production, conversion,, and use of energy in domestic and international markets. Much of this research takes the form of models and associated data bases that have enduring value in policy studies (models) and in supporting related research and modeling efforts (date). For such models and data it is important to ensure that the useful life cycle does not end with the conclusion of the research project. This directory is an important step in extending the usefulness of models and data bases available at the M.I.T. Energy Laboratory. It will be updated from time to time to include new models and data bases that have been developed, or significant changes that have occurred.
Energy and Development. A Modelling Approach
International Nuclear Information System (INIS)
Van Ruijven, B.J.
2008-01-01
Rapid economic growth of developing countries like India and China implies that these countries become important actors in the global energy system. Examples of this impact are the present day oil shortages and rapidly increasing emissions of greenhouse gases. Global energy models are used to explore possible future developments of the global energy system and identify policies to prevent potential problems. Such estimations of future energy use in developing countries are very uncertain. Crucial factors in the future energy use of these regions are electrification, urbanisation and income distribution, issues that are generally not included in present day global energy models. Model simulations in this thesis show that current insight in developments in low-income regions lead to a wide range of expected energy use in 2030 of the residential and transport sectors. This is mainly caused by many different model calibration options that result from the limited data availability for model development and calibration. We developed a method to identify the impact of model calibration uncertainty on future projections. We developed a new model for residential energy use in India, in collaboration with the Indian Institute of Science. Experiments with this model show that the impact of electrification and income distribution is less univocal than often assumed. The use of fuelwood, with related health risks, can decrease rapidly if the income of poor groups increases. However, there is a trade off in terms of CO2 emissions because these groups gain access to electricity and the ownership of appliances increases. Another issue is the potential role of new technologies in developing countries: will they use the opportunities of leapfrogging? We explored the potential role of hydrogen, an energy carrier that might play a central role in a sustainable energy system. We found that hydrogen only plays a role before 2050 under very optimistic assumptions. Regional energy
Energy and Development. A Modelling Approach
Energy Technology Data Exchange (ETDEWEB)
Van Ruijven, B.J.
2008-12-17
Rapid economic growth of developing countries like India and China implies that these countries become important actors in the global energy system. Examples of this impact are the present day oil shortages and rapidly increasing emissions of greenhouse gases. Global energy models are used to explore possible future developments of the global energy system and identify policies to prevent potential problems. Such estimations of future energy use in developing countries are very uncertain. Crucial factors in the future energy use of these regions are electrification, urbanisation and income distribution, issues that are generally not included in present day global energy models. Model simulations in this thesis show that current insight in developments in low-income regions lead to a wide range of expected energy use in 2030 of the residential and transport sectors. This is mainly caused by many different model calibration options that result from the limited data availability for model development and calibration. We developed a method to identify the impact of model calibration uncertainty on future projections. We developed a new model for residential energy use in India, in collaboration with the Indian Institute of Science. Experiments with this model show that the impact of electrification and income distribution is less univocal than often assumed. The use of fuelwood, with related health risks, can decrease rapidly if the income of poor groups increases. However, there is a trade off in terms of CO2 emissions because these groups gain access to electricity and the ownership of appliances increases. Another issue is the potential role of new technologies in developing countries: will they use the opportunities of leapfrogging? We explored the potential role of hydrogen, an energy carrier that might play a central role in a sustainable energy system. We found that hydrogen only plays a role before 2050 under very optimistic assumptions. Regional energy
International Nuclear Information System (INIS)
Reyes, Alejandro; Negrete, Daniela; Mahn, Andrea; Sepúlveda, Francisco
2014-01-01
Highlights: • Thermal conductivity of paraffin wax was improved with aluminum wool. • Aluminum wool surrounding the cans favored the energy recuperation from the wax. • The heat exchanger accumulated 3000 kJ energy. • The accumulated energy can be easily increased with larger units. • COMSOL simulated adequately the energy removal process from the cans. - Abstract: Soft drink cans filled with paraffin wax mixed with 5% w/w aluminum wool, obtained from disposable cans, doubled the thermal conductivity of cans filled only with paraffin wax. Thermal conductivity of the systems was determined by two ways: directly using a thermal conductivimeter, and indirectly based on temperature profiles and on the analytical solution of a cylinder. We designed, built and evaluated a heat exchanger for solar energy accumulation, composed by 48 disposable soft drink cans filled with a total of 9.5 kg of paraffin wax mixed with 5% w/w aluminum wool. In sunny days, the wax melted completely in 3 h. The accumulated energy of 3000 kJ, allowed increasing the temperature of 3.5 m 3 /h air flow rate from 20 to 40 °C during a period of 2 h. This application will allow extending the use of solar energy in drying processes or could be used as household calefaction system. The progress of the phase change front in time during the energy discharge period was simulated with COMSOL, whereas the effect of the number of cans and thermal conductivity of the paraffin wax on the air temperature increase was simulated with MATLAB
A new model for predicting performance of fin-and-tube heat exchanger under frost condition
Energy Technology Data Exchange (ETDEWEB)
Cui, J. [Key Lab. of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024 (China); Li, W.Z., E-mail: wzhongli@dlut.edu.c [Key Lab. of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024 (China); Liu, Y.; Zhao, Y.S. [Key Lab. of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology, Dalian 116024 (China)
2011-02-15
Accurate prediction of frost characteristics has crucial influence on designing effective heat exchangers. In this paper, a new CFD (Computational Fluid Dynamics) model has been proposed to predict the frost behaviour. The initial period of frost formation can be predicted and the influence of surface structure can be considered. The numerical simulations have been carried out to investigate the performance of fin-and-tube heat exchanger under frost condition. The results have been validated by comparison of simulations with the data computed by empirical formulas. The transient local frost formation has been obtained. The average frost thickness, heat exchanger coefficient and pressure drop on air side has been analysed as well. In addition, the influence factors have also been discussed, such as fin pitch, relative humidity, air flow rate and evaporating temperature of refrigerant.
International Nuclear Information System (INIS)
Harjula, R.; Lehto, J.; Paajanen, A.; Saarinen, L.
1997-01-01
Three different inorganic sorbents/ion exchangers have been tested in this work. Granular hexacyanoferrate-based ion exchanger was developed for Cs removal from radioactive liquid waste at NPPs. It was tested for Cs removal from waste solutions containing different complexing agents and detergents. Radiation stability and thermal stability test has shown, that this sorbent can be used for treatment of medium-active waste treatment. Active carbon materials were tested for Co removal from liquid waste effluents at NPPs. It was found that 60 Co cannot be removed from the evaporator concentrates with reasonable efficiency and a combined process with up-stream precipitation step is needed for better Co separation efficiency. Granular modified titanium oxide was tested for 90 Sr removal from the waste effluents and showed very high efficiency. A mathematical model was developed to analyze ion exchange performance in feeds of different chemical and radiochemical compositions. (author). 9 refs, 7 figs, 3 tabs
Net modelling of energy mix among European Countries: A proposal for ruling new scenarios
International Nuclear Information System (INIS)
Dassisti, M.; Carnimeo, L.
2012-01-01
European energy policy pursues the objective of a sustainable, competitive and secure supply of energy. In 2007, the European Commission adopted an energy policy for Europe, which was supported by several documents on different aspects of energy and included an action plan to meet the major energy challenges Europe has to face. A farsighted diversified yearly mix of energies was suggested to countries, aiming at increasing security of supply and efficiency, but a wide and contemporary view of energy interchanges between states was not available. In a previous work of the same authors, energy import/export interchanges between European States were used to develop a geographic overview at one-glance. In this paper, the enhanced Interchange Energy Network (IEN) is investigated from a modelling point of view, as a Small-World Net, by supposing that connections can exist between States with a probability depending also on economic/political relations between countries. -- Highlights: ► Different view of the imports and exports of electric energy flows between European for potential use in ruling exchanges. ► Panel data from 1996 to 2008 as part of a network of exchanges was considered from Eurostat official database. ► The European import/export energy flows modelled as a network with Small-World phenomena, interpreting the evolution over the years. ► Interesting behavioural features as outcome derived, as shown for the case example of the Germany.
Heat exchange modeling in a multilayered karst aquifer affected by seawater intrusion
Directory of Open Access Journals (Sweden)
Luca Vettorello
2015-11-01
Full Text Available A Feflow thermohaline model has been implemented in order to study borehole heat exchangers (BHEs activity in a coastal aquifer in the South of Italy (Province of Lecce, Puglia Region. The modeled closed-loop system consists of two double u-pipe heat exchangers, installed in 200 meters deep boreholes. The main purpose of numerical modeling was to forecast thermal plume extension in groundwater after a long period of heat exchange, calculating temperature trends in observation points during a 10 years transport simulation. The complex geological structure, including calcarenites, fractured limestones and a deep karst aquifer, has been translated into a multilayered model, with a depth-related parameter distribution, assigning different values of hydraulic, thermal and chemical properties to each layer. In particular saltwater concentration has been taken into account, considering the influence of seawater intrusion on the heat transport density-dependent model. Parameters assignment was based on experimental datasets collected during initial field investigations, including thermal characterization of soil samples and GRTs, together with historical hydrogeological and hydrochemical measures and previous groundwater surveys. After model structure configuration and aquifers parameterization, a sensitivity analysis on porosity and heat dispersivity has been conducted, to evaluate their influence on thermal transport phenomena with a multiple scenarios approach, considering in particular the uncertainty related to secondary porosity in karst systems. Feflow simulation represented the first step in environmental compatibility evaluation for the BHE plant, waiting for the necessary model calibration with groundwater temperature monitoring trends.
International Nuclear Information System (INIS)
Zarrella, Angelo; Capozza, Antonio; De Carli, Michele
2013-01-01
This paper presents a new simulation tool package that calculates the energy efficiency of an entire Ground Source Heat Pump (GSHP) system. The package consists of two detailed models of borehole heat exchangers and heat pump equipment coupled in a single well-integrated calculation tool. It was used to analyze two types of ground heat exchangers in the same operating conditions for two Italian climates. Research focused on comparing a short helical-shaped pipe configuration with the more widespread and longer double U-tube. Analysis was carried out at the same energy exchange rate with the ground and addressed the difference in total borehole depth. The package also took into account the effects of the weather on the heat transfer between the heat exchanger and the surrounding ground. Analysis found that a much shorter total borehole depth was needed for the helical-shaped pipe, which consequently reduces installation costs. Therefore, this configuration may be a suitable alternative to conventional U-shaped tubes, especially for new residential housing with low energy loads and where deep probe drilling is not possible. Finally, this paper also investigates the influence of the axial effects in the ground on the seasonal energy efficiency of the whole system. -- Highlights: • A new model to evaluate the efficiency of the whole GSHP system is presented. • The model considers the interaction between the ground and the environment. • Two types of vertical ground heat exchangers are analyzed: helix and 2U-tube. • They are analyzed in the same operating conditions for two Italian climates. • With helical shaped pipe a shorter total borehole depth is required
A Three-State Markov-Modulated Switching Model for Exchange Rates
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Idowu Oluwasayo Ayodeji
2016-01-01
Full Text Available Several authors have examined the long swings hypothesis in exchange rates using a two-state Markov switching model. This study developed a model to investigate long swings hypothesis in currencies which may exhibit a k-state (k≥2 pattern. The proposed model was then applied to euros, British pounds, Japanese yen, and Nigerian naira. Specification measures such as AIC, BIC, and HIC favoured a three-state pattern in Nigerian naira but a two-state one in the other three currencies. For the period January 2004 to May 2016, empirical results suggested the presence of asymmetric swings in naira and yen and long swings in euros and pounds. In addition, taking 0.5 as the benchmark for smoothing probabilities, choice models provided a clear reading of the cycle in a manner that is consistent with the realities of the movements in corresponding exchange rate series.
Volume Averaging Theory (VAT) based modeling and closure evaluation for fin-and-tube heat exchangers
Zhou, Feng; Catton, Ivan
2012-10-01
A fin-and-tube heat exchanger was modeled based on Volume Averaging Theory (VAT) in such a way that the details of the original structure was replaced by their averaged counterparts, so that the VAT based governing equations can be efficiently solved for a wide range of parameters. To complete the VAT based model, proper closure is needed, which is related to a local friction factor and a heat transfer coefficient of a Representative Elementary Volume (REV). The terms in the closure expressions are complex and sometimes relating experimental data to the closure terms is difficult. In this work we use CFD to evaluate the rigorously derived closure terms over one of the selected REVs. The objective is to show how heat exchangers can be modeled as a porous media and how CFD can be used in place of a detailed, often formidable, experimental effort to obtain closure for the model.
Modeling pressure drop of inclined flow through a heat exchanger for aero-engine applications
International Nuclear Information System (INIS)
Missirlis, D.; Yakinthos, K.; Storm, P.; Goulas, A.
2007-01-01
In the present work further numerical predictions for the flow field through a specific type of a heat exchanger, which is planned to be used in the exhaust nozzle of aircraft engines. In order to model the flow field through the heat exchanger, a porous medium model is used based on a simple quadratic relation, which connects the pressure drop with the inlet air velocity in the external part of the heat exchanger. The aim of this work is to check the applicability of the quadratic law in a variety of velocity inlet conditions configured by different angles of attack. The check is performed with CFD and the results are compared with new available experimental data for these inlet conditions. A detailed qualitative analysis shows that although the quadratic law has been derived for a zero angle of attack, it performs very well for alternative non-zero angles. These observations are very helpful since this simple pressure drop law can be used for advanced computations where the whole system of the exhaust nozzle together with the heat exchangers can be modeled within a holistic approach
Model Predictive Control for Smart Energy Systems
DEFF Research Database (Denmark)
Halvgaard, Rasmus
In this thesis, we consider control strategies for flexible distributed energy resources in the future intelligent energy system – the Smart Grid. The energy system is a large-scale complex network with many actors and objectives in different hierarchical layers. Specifically the power system must...... significantly. A Smart Grid calls for flexible consumers that can adjust their consumption based on the amount of green energy in the grid. This requires coordination through new large-scale control and optimization algorithms. Trading of flexibility is key to drive power consumption in a sustainable direction....... In Denmark, we expect that distributed energy resources such as heat pumps, and batteries in electric vehicles will mobilize part of the needed flexibility. Our primary objectives in the thesis were threefold: 1.Simulate the components in the power system based on simple models from literature (e.g. heat...
Directory of Open Access Journals (Sweden)
R. J. Wichink Kruit
2012-12-01
Full Text Available A large shortcoming of current chemistry transport models (CTM for simulating the fate of ammonia in the atmosphere is the lack of a description of the bi-directional surface–atmosphere exchange. In this paper, results of an update of the surface–atmosphere exchange module DEPAC, i.e. DEPosition of Acidifying Compounds, in the chemistry transport model LOTOS-EUROS are discussed. It is shown that with the new description, which includes bi-directional surface–atmosphere exchange, the modeled ammonia concentrations increase almost everywhere, in particular in agricultural source areas. The reason is that by using a compensation point the ammonia lifetime and transport distance is increased. As a consequence, deposition of ammonia and ammonium decreases in agricultural source areas, while it increases in large nature areas and remote regions especially in southern Scandinavia. The inclusion of a compensation point for water reduces the dry deposition over sea and allows reproducing the observed marine background concentrations at coastal locations to a better extent. A comparison with measurements shows that the model results better represent the measured ammonia concentrations. The concentrations in nature areas are slightly overestimated, while the concentrations in agricultural source areas are still underestimated. Although the introduction of the compensation point improves the model performance, the modeling of ammonia remains challenging. Important aspects are emission patterns in space and time as well as a proper approach to deal with the high concentration gradients in relation to model resolution. In short, the inclusion of a bi-directional surface–atmosphere exchange is a significant step forward for modeling ammonia.
DEFF Research Database (Denmark)
Sørensen, P. B.; Fauser, P.; Carlsen, L.
It is shown how diffusion and deposition of solids drive the flux of substance between the water column and the sediment. The generic compartment models (Mackay type) use a one box model for the sediment in order to keep the calculations simple. However, when diffusion needs to be included...... where diffusion or deposition is negligible or where both processes must be included in order to describe the sediment-water substance exchange most appropriately....
Diaz-Espejo, A.; Verhoef, A.
2003-04-01
Soil moisture is, together with nitrogen, the most important limiting factor in the plant global production. Its spatial and temporal evolution will determine the energy, water and carbon budgets and the vegetation distribution. For vegetated surfaces, the evapotranspiration is a large component of the energy balance. Understanding the response of the plants to their environment is critical to estimate this flux. To study the evolution of the evapotranspiration under different conditions we have designed a high precision mini lysimeter system. The aim of this set-up is to get a better insight into the interaction between root-zone soil moisture and canopy exchange processes. The experiment consists of 25 soil-filled perspex boxes, which are arranged in a 5× 5-square. This set-up allows for flexibility in experimental set-up and vegetation types/soil moisture levels, and enables us to mimic within-field, or even within-region, variability, without the experimental difficulties encountered in field trials. The results show how soil water stress promotes a high variability in the canopy development and in the evapotranspiration, thereby affecting other components of the energy balance, especially the sensible heat flux. The effect of this variation on the CO_2 exchange and its impact on the water use efficiency by plants is also discussed. The results will be used to include the impact of soil water stress on canopy gas exchange in a Soil Vegetation Atmosphere Transfer model (SVAT). Furthermore, it will be tested how well a simple SVAT scheme can deal with within and between pixel variability. This study is deemed extremely relevant for large-scale remote sensing and to aid our understanding the impact of climate change on heterogeneous surfaces.
Radisavljevic, Verica
2011-10-01
In this paper we first show that the linear models of proton exchange membrane (polymer electrolyte membrane, PEM) and solid oxide (SO) fuel cells, commonly used in power and energy literature, are not controllable. The source of uncontrollability is the equation for pressure of the water vapor that is only affected by the fuel cell current, which in fact is a disturbance in this system and cannot be controlled by the given model inputs: inlet molar flow rates of hydrogen and oxygen. Being uncontrollable these models are not good candidates for studying control of dynamic processes in PEM and SO fuel cells. However, due to their simplicity, they can be used in hybrid configurations with other energy producing devices such as photovoltaic (solar) cells, wind turbine, micro gas turbine, battery (ultra capacitor) to demonstrate some other phenomena, but not for control purposes unless the hybrid models formed in such hybrid configurations are controllable. Testing controllability of such hybrid models is mandatory. Secondly, we introduce some algebraic constraints that follow from the model dynamics and the Nernst open-loop fuel cell voltage formula. These constraints must be satisfied in simulation of considered fuel cell modes, for example, via MATLAB/Simulink or any other computer software package.
Nacer, B.; Massobrio, C.; Félix, C.
1997-10-01
We have investigated the deposition at zero impact kinetic energy of the Ag atom and clusters (Ag7,Ag19) on the (100) and (111) surfaces of Pd by molecular-dynamics simulations performed within the embedded-atom-method scheme. Our results elucidate the role played by the adsorption energy in determining the final morphology of the cluster/substrate system when ideal nondestructive deposition conditions are implemented. While implantation of the atom is not observed, we find a finite probability of site Ag-Pd exchanges in the case of clusters. Deposition-assisted mixing occurring at the topmost surface layer appears to be correlated to the size of the cluster and the orientation of the substrate, being higher for Ag7/Pd(100) and lower for Ag19/Pd(111). Total-energy calculations, combined with an analysis of the atomic motion, indicate that the structural transformation accompanying the deposition of the cluster provides the needed activation energy to induce the observed Ag-Pd atomic exchanges.
Directory of Open Access Journals (Sweden)
Rybiński Witold
2016-09-01
Full Text Available The paper presents four 1-dimensional models of thermal resistance of walls in a heat exchanger with rectangular minichannels. The first model is the simplest one, with a single wall separating two fluids. The second model of the so called equivalent wall takes into account total volume of intermediate walls between layers of minichannels and of side walls of minichannels. The next two more complicated models take separately into account thermal resistance of these walls. In these two models side walls are treated as fins. The results of models comparison are presented. It is shown that thermal resistance may be neglected for metal walls but it should be taken into account for the walls made of plastics. For the case of non-neglected wall thermal resistance the optimum wall thickness was derived. Minichannel heat exchangers made of plastic are larger than those built of metal, but are significantly cheaper. It makes possible to use of such exchangers in inexpensive microscale ORC installations.
DEFF Research Database (Denmark)
Hilpert, Simon; Günther, Stephan; Kaldemeyer, Cord
2017-01-01
complexity of energy systems and high uncertainties on different levels. In addition, interdisciplinary modelling is necessary for getting insight in mechanisms of an integrated world. At the same time models need to meet scientific standards as public acceptance becomes increasingly important......The process of modelling energy systems is accompanied by challenges inherently connected with mathematical modelling. However, due to modern realities in the 21st century, existing challenges are gaining in magnitude and are supplemented with new ones. Modellers are confronted with a rising....... In this intricate environment model application as well as result communication and interpretation is also getting more difficult. In this paper we present the open energy modelling framework (oemof) as a novel approach for energy system modelling and derive its contribution to existing challenges. Therefore, based...
A Statistical Model for Energy Intensity
Directory of Open Access Journals (Sweden)
Marjaneh Issapour
2012-12-01
Full Text Available A promising approach to improve scientific literacy in regards to global warming and climate change is using a simulation as part of a science education course. The simulation needs to employ scientific analysis of actual data from internationally accepted and reputable databases to demonstrate the reality of the current climate change situation. One of the most important criteria for using a simulation in a science education course is the fidelity of the model. The realism of the events and consequences modeled in the simulation is significant as well. Therefore, all underlying equations and algorithms used in the simulation must have real-world scientific basis. The "Energy Choices" simulation is one such simulation. The focus of this paper is the development of a mathematical model for "Energy Intensity" as a part of the overall system dynamics in "Energy Choices" simulation. This model will define the "Energy Intensity" as a function of other independent variables that can be manipulated by users of the simulation. The relationship discovered by this research will be applied to an algorithm in the "Energy Choices" simulation.
Metamaterial Model of Tachyonic Dark Energy
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Igor I. Smolyaninov
2014-02-01
Full Text Available Dark energy with negative pressure and positive energy density is believed to be responsible for the accelerated expansion of the universe. Quite a few theoretical models of dark energy are based on tachyonic fields interacting with itself and normal (bradyonic matter. Here, we propose an experimental model of tachyonic dark energy based on hyperbolic metamaterials. Wave equation describing propagation of extraordinary light inside hyperbolic metamaterials exhibits 2 + 1 dimensional Lorentz symmetry. The role of time in the corresponding effective 3D Minkowski spacetime is played by the spatial coordinate aligned with the optical axis of the metamaterial. Nonlinear optical Kerr effect bends this spacetime resulting in effective gravitational force between extraordinary photons. We demonstrate that this model has a self-interacting tachyonic sector having negative effective pressure and positive effective energy density. Moreover, a composite multilayer SiC-Si hyperbolic metamaterial exhibits closely separated tachyonic and bradyonic sectors in the long wavelength infrared range. This system may be used as a laboratory model of inflation and late time acceleration of the universe.
Non-Regge and hyper-Regge effects in pion-nucleon charge exchange scattering at high energies
International Nuclear Information System (INIS)
Joynson, D.; Leader, E.; Nicolescu, B.; Paris-6 Univ., 75; Lopez, C.
1975-04-01
The experimental data on the charge exchange differential cross-section and on the difference on the π + p and π - p total cross-sections between 5GeV/c to 200GeV/c are shown to be incompatible with conventional Regge asymptotic behavior. It is shown that an additional term is required which grows in importance with energy. The precise form of the new term cannot be ascertained, but it is shown that it corresponds to a singularity at J=1 in the complex angular momentum plane. Amongst the possible types of additional term there are two which have been closely analysed: a non-Regge behavior, a hyper-Regge term which have allowed very striking predictions in particular for the charge exchange polarisation [fr
A thermoelectric power generating heat exchanger: Part II – Numerical modeling and optimization
International Nuclear Information System (INIS)
Sarhadi, Ali; Bjørk, Rasmus; Lindeburg, Niels; Viereck, Peter; Pryds, Nini
2016-01-01
Highlights: • A comprehensive model was developed to optimize the integrated TEG-heat exchanger. • The developed model was validated with the experimental data. • The effect of using different interface materials on the output power was assessed. • The influence of TEG arrangement on the power production was investigated. • Optimized geometrical parameters and proper interface materials were suggested. - Abstract: In Part I of this study, the performance of an experimental integrated thermoelectric generator (TEG)-heat exchanger was presented. In the current study, Part II, the obtained experimental results are compared with those predicted by a finite element (FE) model. In the simulation of the integrated TEG-heat exchanger, the thermal contact resistance between the TEG and the heat exchanger is modeled assuming either an ideal thermal contact or using a combined Cooper–Mikic–Yovanovich (CMY) and parallel plate gap formulation, which takes into account the contact pressure, roughness and hardness of the interface surfaces as well as the air gap thermal resistance at the interface. The combined CMY and parallel plate gap model is then further developed to simulate the thermal contact resistance for the case of an interface material. The numerical results show good agreement with the experimental data with an average deviation of 17% for the case without interface material and 12% in the case of including additional material at the interfaces. The model is then employed to evaluate the power production of the integrated system using different interface materials, including graphite, aluminum (Al), tin (Sn) and lead (Pb) in a form of thin foils. The numerical results show that lead foil at the interface has the best performance, with an improvement in power production of 34% compared to graphite foil. Finally, the model predicts that for a certain flow rate, increasing the parallel TEG channels for the integrated systems with 4, 8, and 12 TEGs
OSeMOSYS Energy Modeling Using an Extended UTOPIA Model
Lavigne, Denis
2017-01-01
The OSeMOSYS project offers open-access energy modeling to a wide audience. Its relative simplicity makes it appealing for academic research and governmental organizations to study the impacts of policy decisions on an energy system in the context of possibly severe greenhouse gases emissions limitations. OSeMOSYS is a tool that enhances the…
Bollen, Y.J.M.; Kamphuis, M.B.; Mierlo, van C.P.M.
2006-01-01
Many native proteins occasionally form partially unfolded forms (PUFs), which can be detected by hydrogen/deuterium exchange and NMR spectroscopy. Knowledge about these metastable states is required to better understand the onset of folding-related diseases. So far, not much is known about where
Bollen, Y.J.M.; Kamphuis, M.B.; Van Mierlo, C.P.M.
2006-01-01
Many native proteins occasionally form partially unfolded forms (PUFs), which can be detected by hydrogen/deuterium exchange and NMR spectroscopy. Knowledge about these metastable states is required to better understand the onset of folding-related diseases. So far, not much is known about where
Modeling energy-economy interactions using integrated models
International Nuclear Information System (INIS)
Uyterlinde, M.A.
1994-06-01
Integrated models are defined as economic energy models that consist of several submodels, either coupled by an interface module, or embedded in one large model. These models can be used for energy policy analysis. Using integrated models yields the following benefits. They provide a framework in which energy-economy interactions can be better analyzed than in stand-alone models. Integrated models can represent both energy sector technological details, as well as the behaviour of the market and the role of prices. Furthermore, the combination of modeling methodologies in one model can compensate weaknesses of one approach with strengths of another. These advantages motivated this survey of the class of integrated models. The purpose of this literature survey therefore was to collect and to present information on integrated models. To carry out this task, several goals were identified. The first goal was to give an overview of what is reported on these models in general. The second one was to find and describe examples of such models. Other goals were to find out what kinds of models were used as component models, and to examine the linkage methodology. Solution methods and their convergence properties were also a subject of interest. The report has the following structure. In chapter 2, a 'conceptual framework' is given. In chapter 3 a number of integrated models is described. In a table, a complete overview is presented of all described models. Finally, in chapter 4, the report is summarized, and conclusions are drawn regarding the advantages and drawbacks of integrated models. 8 figs., 29 refs
International Nuclear Information System (INIS)
Cristescu, Ioana R.; Cristescu, I.; Bornea, Anisia; Penzhorn, R.-D.; Tamm, U.
2001-01-01
The objectives of the models presented in this paper are to simulate the deuterium enrichment performances of several catalytic exchange columns under test at the Tritium Laboratory in Karlsruhe (TLK). The models and the corresponding software are presently being verified by experiments aimed to provide the data required for the design of large isotopic exchange columns such as needed for the recovery of tritium from waste water generated during the operation of the tritium facilities of fusion machines. In the ongoing TLK experiments the transfer of deuterium takes place in a counter current isotopic exchange column. Pre-heated water is fed into the column from the top and deuterated hydrogen from the bottom. Condensed water vapor and deuterium-depleted hydrogen are removed from the top and deuterium enriched water from the bottom and analyzed by standard procedures. To describe the performance of the separation process two approaches were considered: a graphical approach (classical) that uses the operating line and equilibrium curve for the process and an analytical approach that solves the transport equations characterizing the isotopic exchange process. (authors)
A model for foreign exchange markets based on glassy Brownian systems
Trinidad-Segovia, J. E.; Clara-Rahola, J.; Puertas, A. M.; De las Nieves, F. J.
2017-01-01
In this work we extend a well-known model from arrested physical systems, and employ it in order to efficiently depict different currency pairs of foreign exchange market price fluctuation distributions. We consider the exchange rate price in the time range between 2010 and 2016 at yearly time intervals and resolved at one minute frequency. We then fit the experimental datasets with this model, and find significant qualitative symmetry between price fluctuation distributions from the currency market, and the ones belonging to colloidal particles position in arrested states. The main contribution of this paper is a well-known physical model that does not necessarily assume the independent and identically distributed (i.i.d.) restrictive condition. PMID:29206868
Modelling the Dependence Structure of MUR/USD and MUR/INR Exchange Rates using Copula
Directory of Open Access Journals (Sweden)
Vandna Jowaheer
2012-01-01
Full Text Available American Dollar (USD and Indian Rupee (INR play an important role in Mauritian economy. It is important to model the pattern of dependence in their co-movement with respect to Mauritian Rupee (MUR, as this may indicate the export-import behavior in Mauritius. However, it is known that distributions of exchange rates are usually non-normal and the use of linear correlation as a dependence measure is inappropriate. Moreover it is quite difficult to obtain the joint distribution of such random variables in order to specify the complete covariance matrix to measure their dependence structure. In this paper, we first identify the marginal distributions of the exchange rates of MUR against USD and INR and then select the best fitting copula model for the bivariate series. It is concluded that both the series are asymmetric and fat-tailed following hyperbolic distribution. Their dependence structure is appropriately modeled by t copula.
A model for foreign exchange markets based on glassy Brownian systems.
Sánchez-Granero, M A; Trinidad-Segovia, J E; Clara-Rahola, J; Puertas, A M; De Las Nieves, F J
2017-01-01
In this work we extend a well-known model from arrested physical systems, and employ it in order to efficiently depict different currency pairs of foreign exchange market price fluctuation distributions. We consider the exchange rate price in the time range between 2010 and 2016 at yearly time intervals and resolved at one minute frequency. We then fit the experimental datasets with this model, and find significant qualitative symmetry between price fluctuation distributions from the currency market, and the ones belonging to colloidal particles position in arrested states. The main contribution of this paper is a well-known physical model that does not necessarily assume the independent and identically distributed (i.i.d.) restrictive condition.