International Nuclear Information System (INIS)
Owusu, Haile K; Yuzbashyan, Emil A
2011-01-01
We study general quantum integrable Hamiltonians linear in a coupling constant and represented by finite N x N real symmetric matrices. The restriction on the coupling dependence leads to a natural notion of nontrivial integrals of motion and classification of integrable families into types according to the number of such integrals. A type M family in our definition is formed by N-M nontrivial mutually commuting operators linear in the coupling. Working from this definition alone, we parameterize type M operators, i.e. resolve the commutation relations, and obtain an exact solution for their eigenvalues and eigenvectors. We show that our parameterization covers all type 1, 2 and 3 integrable models and discuss the extent to which it is complete for other types. We also present robust numerical observation on the number of energy-level crossings in type M integrable systems and analyze the taxonomy of types in the 1D Hubbard model. (paper)
Impact mitigation using kinematic constraints and the full space parameterization method
Energy Technology Data Exchange (ETDEWEB)
Morgansen, K.A.; Pin, F.G.
1996-02-01
A new method for mitigating unexpected impact of a redundant manipulator with an object in its environment is presented. Kinematic constraints are utilized with the recently developed method known as Full Space Parameterization (FSP). System performance criterion and constraints are changed at impact to return the end effector to the point of impact and halt the arm. Since large joint accelerations could occur as the manipulator is halted, joint acceleration bounds are imposed to simulate physical actuator limitations. Simulation results are presented for the case of a simple redundant planar manipulator.
Resolving kinematic redundancy with constraints using the FSP (Full Space Parameterization) approach
International Nuclear Information System (INIS)
Pin, F.G.; Tulloch, F.A.
1996-01-01
A solution method is presented for the motion planning and control of kinematically redundant serial-link manipulators in the presence of motion constraints such as joint limits or obstacles. Given a trajectory for the end-effector, the approach utilizes the recently proposed Full Space Parameterization (FSP) method to generate a parameterized expression for the entire space of solutions of the unconstrained system. At each time step, a constrained optimization technique is then used to analytically find the specific joint motion solution that satisfies the desired task objective and all the constraints active during the time step. The method is applicable to systems operating in a priori known environments or in unknown environments with sensor-based obstacle detection. The derivation of the analytical solution is first presented for a general type of kinematic constraint and is then applied to the problem of motion planning for redundant manipulators with joint limits and obstacle avoidance. Sample results using planar and 3-D manipulators with various degrees of redundancy are presented to illustrate the efficiency and wide applicability of constrained motion planning using the FSP approach
On the Dependence of Cloud Feedbacks on Physical Parameterizations in WRF Aquaplanet Simulations
Cesana, Grégory; Suselj, Kay; Brient, Florent
2017-10-01
We investigate the effects of physical parameterizations on cloud feedback uncertainty in response to climate change. For this purpose, we construct an ensemble of eight aquaplanet simulations using the Weather Research and Forecasting (WRF) model. In each WRF-derived simulation, we replace only one parameterization at a time while all other parameters remain identical. By doing so, we aim to (i) reproduce cloud feedback uncertainty from state-of-the-art climate models and (ii) understand how parametrizations impact cloud feedbacks. Our results demonstrate that this ensemble of WRF simulations, which differ only in physical parameterizations, replicates the range of cloud feedback uncertainty found in state-of-the-art climate models. We show that microphysics and convective parameterizations govern the magnitude and sign of cloud feedbacks, mostly due to tropical low-level clouds in subsidence regimes. Finally, this study highlights the advantages of using WRF to analyze cloud feedback mechanisms owing to its plug-and-play parameterization capability.
Parameterization of the Age-Dependent Whole Brain Apparent Diffusion Coefficient Histogram
Batra, Marion; Nägele, Thomas
2015-01-01
Purpose. The distribution of apparent diffusion coefficient (ADC) values in the brain can be used to characterize age effects and pathological changes of the brain tissue. The aim of this study was the parameterization of the whole brain ADC histogram by an advanced model with influence of age considered. Methods. Whole brain ADC histograms were calculated for all data and for seven age groups between 10 and 80 years. Modeling of the histograms was performed for two parts of the histogram separately: the brain tissue part was modeled by two Gaussian curves, while the remaining part was fitted by the sum of a Gaussian curve, a biexponential decay, and a straight line. Results. A consistent fitting of the histograms of all age groups was possible with the proposed model. Conclusions. This study confirms the strong dependence of the whole brain ADC histograms on the age of the examined subjects. The proposed model can be used to characterize changes of the whole brain ADC histogram in certain diseases under consideration of age effects. PMID:26609526
Parameterization of the Age-Dependent Whole Brain Apparent Diffusion Coefficient Histogram
Directory of Open Access Journals (Sweden)
Uwe Klose
2015-01-01
Full Text Available Purpose. The distribution of apparent diffusion coefficient (ADC values in the brain can be used to characterize age effects and pathological changes of the brain tissue. The aim of this study was the parameterization of the whole brain ADC histogram by an advanced model with influence of age considered. Methods. Whole brain ADC histograms were calculated for all data and for seven age groups between 10 and 80 years. Modeling of the histograms was performed for two parts of the histogram separately: the brain tissue part was modeled by two Gaussian curves, while the remaining part was fitted by the sum of a Gaussian curve, a biexponential decay, and a straight line. Results. A consistent fitting of the histograms of all age groups was possible with the proposed model. Conclusions. This study confirms the strong dependence of the whole brain ADC histograms on the age of the examined subjects. The proposed model can be used to characterize changes of the whole brain ADC histogram in certain diseases under consideration of age effects.
DEFF Research Database (Denmark)
Tastu, Julija; Pinson, Pierre; Madsen, Henrik
2015-01-01
-correlations. Estimation is performed in a maximum likelihood framework. Based on a test case application in Denmark, with spatial dependencies over 15 areas and temporal ones for 43 hourly lead times (hence, for a dimension of n = 645), it is shown that accounting for space-time effects is crucial for generating skilful......Emphasis is placed on generating space-time trajectories of wind power generation, consisting of paths sampled from high-dimensional joint predictive densities, describing wind power generation at a number of contiguous locations and successive lead times. A modelling approach taking advantage...
Directory of Open Access Journals (Sweden)
K. M. Sakamoto
2016-06-01
Full Text Available Biomass-burning aerosols have a significant effect on global and regional aerosol climate forcings. To model the magnitude of these effects accurately requires knowledge of the size distribution of the emitted and evolving aerosol particles. Current biomass-burning inventories do not include size distributions, and global and regional models generally assume a fixed size distribution from all biomass-burning emissions. However, biomass-burning size distributions evolve in the plume due to coagulation and net organic aerosol (OA evaporation or formation, and the plume processes occur on spacial scales smaller than global/regional-model grid boxes. The extent of this size-distribution evolution is dependent on a variety of factors relating to the emission source and atmospheric conditions. Therefore, accurately accounting for biomass-burning aerosol size in global models requires an effective aerosol size distribution that accounts for this sub-grid evolution and can be derived from available emission-inventory and meteorological parameters. In this paper, we perform a detailed investigation of the effects of coagulation on the aerosol size distribution in biomass-burning plumes. We compare the effect of coagulation to that of OA evaporation and formation. We develop coagulation-only parameterizations for effective biomass-burning size distributions using the SAM-TOMAS large-eddy simulation plume model. For the most-sophisticated parameterization, we use the Gaussian Emulation Machine for Sensitivity Analysis (GEM-SA to build a parameterization of the aged size distribution based on the SAM-TOMAS output and seven inputs: emission median dry diameter, emission distribution modal width, mass emissions flux, fire area, mean boundary-layer wind speed, plume mixing depth, and time/distance since emission. This parameterization was tested against an independent set of SAM-TOMAS simulations and yields R2 values of 0.83 and 0.89 for Dpm and modal width
Sakamoto, Kimiko M.; Laing, James R.; Stevens, Robin G.; Jaffe, Daniel A.; Pierce, Jeffrey R.
2016-06-01
Biomass-burning aerosols have a significant effect on global and regional aerosol climate forcings. To model the magnitude of these effects accurately requires knowledge of the size distribution of the emitted and evolving aerosol particles. Current biomass-burning inventories do not include size distributions, and global and regional models generally assume a fixed size distribution from all biomass-burning emissions. However, biomass-burning size distributions evolve in the plume due to coagulation and net organic aerosol (OA) evaporation or formation, and the plume processes occur on spacial scales smaller than global/regional-model grid boxes. The extent of this size-distribution evolution is dependent on a variety of factors relating to the emission source and atmospheric conditions. Therefore, accurately accounting for biomass-burning aerosol size in global models requires an effective aerosol size distribution that accounts for this sub-grid evolution and can be derived from available emission-inventory and meteorological parameters. In this paper, we perform a detailed investigation of the effects of coagulation on the aerosol size distribution in biomass-burning plumes. We compare the effect of coagulation to that of OA evaporation and formation. We develop coagulation-only parameterizations for effective biomass-burning size distributions using the SAM-TOMAS large-eddy simulation plume model. For the most-sophisticated parameterization, we use the Gaussian Emulation Machine for Sensitivity Analysis (GEM-SA) to build a parameterization of the aged size distribution based on the SAM-TOMAS output and seven inputs: emission median dry diameter, emission distribution modal width, mass emissions flux, fire area, mean boundary-layer wind speed, plume mixing depth, and time/distance since emission. This parameterization was tested against an independent set of SAM-TOMAS simulations and yields R2 values of 0.83 and 0.89 for Dpm and modal width, respectively. The
International Nuclear Information System (INIS)
Herrero, Jose Javier; Garcia-Herranz, Nuria; Ahnert, Carol
2011-01-01
There exists an interest in performing full core pin-by-pin computations for present nuclear reactors. In such type of problems the use of a transport approximation like the diffusion equation requires the introduction of correction parameters. Interface discontinuity factors can improve the diffusion solution to nearly reproduce a transport solution. Nevertheless, calculating accurate pin-by-pin IDF requires the knowledge of the heterogeneous neutron flux distribution, which depends on the boundary conditions of the pin-cell as well as the local variables along the nuclear reactor operation. As a consequence, it is impractical to compute them for each possible configuration. An alternative to generate accurate pin-by-pin interface discontinuity factors is to calculate reference values using zero-net-current boundary conditions and to synthesize afterwards their dependencies on the main neighborhood variables. In such way the factors can be accurately computed during fine-mesh diffusion calculations by correcting the reference values as a function of the actual environment of the pin-cell in the core. In this paper we propose a parameterization of the pin-by-pin interface discontinuity factors allowing the implementation of a cross sections library able to treat the neighborhood effect. First results are presented for typical PWR configurations. (author)
Energy Technology Data Exchange (ETDEWEB)
Herrero, Jose Javier; Garcia-Herranz, Nuria; Ahnert, Carol, E-mail: herrero@din.upm.es, E-mail: nuria@din.upm.es, E-mail: carol@din.upm.es [Departamento de Ingenieria Nuclear, Universidad Politecnica de Madrid (Spain)
2011-07-01
There exists an interest in performing full core pin-by-pin computations for present nuclear reactors. In such type of problems the use of a transport approximation like the diffusion equation requires the introduction of correction parameters. Interface discontinuity factors can improve the diffusion solution to nearly reproduce a transport solution. Nevertheless, calculating accurate pin-by-pin IDF requires the knowledge of the heterogeneous neutron flux distribution, which depends on the boundary conditions of the pin-cell as well as the local variables along the nuclear reactor operation. As a consequence, it is impractical to compute them for each possible configuration. An alternative to generate accurate pin-by-pin interface discontinuity factors is to calculate reference values using zero-net-current boundary conditions and to synthesize afterwards their dependencies on the main neighborhood variables. In such way the factors can be accurately computed during fine-mesh diffusion calculations by correcting the reference values as a function of the actual environment of the pin-cell in the core. In this paper we propose a parameterization of the pin-by-pin interface discontinuity factors allowing the implementation of a cross sections library able to treat the neighborhood effect. First results are presented for typical PWR configurations. (author)
Surface shear stress dependence of gas transfer velocity parameterizations using DNS
Fredriksson, S. T.; Arneborg, L.; Nilsson, H.; Handler, R. A.
2016-10-01
Air-water gas-exchange is studied in direct numerical simulations (DNS) of free-surface flows driven by natural convection and weak winds. The wind is modeled as a constant surface-shear-stress and the gas-transfer is modeled via a passive scalar. The simulations are characterized via a Richardson number Ri=Bν/u*4 where B, ν, and u* are the buoyancy flux, kinematic viscosity, and friction velocity respectively. The simulations comprise 0Ric or kg=AShearu*Sc-n, Ri
Dependence of optimal wind turbine spacing on wind farm length
Stevens, Richard Johannes Antonius Maria
2016-01-01
Recent large eddy simulations have led to improved parameterizations of the effective roughness height of wind farms. This effective roughness height can be used to predict the wind velocity at hub-height as function of the geometric mean of the spanwise and streamwise turbine spacings and the
Nelson, R. R.; O'Dell, C.
2017-12-01
The primary goal of OCO-2 is to use hyperspectral measurements of reflected near-infrared sunlight to retrieve the column-averaged dry-air mole fraction of carbon dioxide (XCO2) with high accuracy. This is only possible for measurements of scenes nearly free of optically thick clouds and aerosols. As some cloud or aerosol contamination will always be present, the OCO-2 retrieval algorithm includes clouds and aerosols as retrieved properties in its state vector. Information content analyses demonstrate that there are only 2-6 pieces of information about aerosols in the OCO-2 radiances. However, the upcoming OCO-2 algorithm (B8) attempts to retrieve 9 aerosol parameters; this over-fitting can hinder convergence and produce multiple solutions. In this work, we develop a simplified cloud and aerosol parameterization that intelligently reduces the number of retrieved parameters to 5 by only retrieving information about two aerosol layers: a lower tropospheric layer and an upper tropospheric / stratospheric layer. We retrieve the optical depth of each layer and the height of the lower tropospheric layer. Each of these layers contains a mixture of fine and coarse mode aerosol. In comparisons between OCO-2 XCO2 estimates and validation sources including TCCON, this scheme performs about as well as the more complicated OCO-2 retrieval algorithm, but has the potential benefits of more interpretable aerosol results, faster convergence, less nonlinearity, and greater throughput. We also investigate the dependence of our results on the optical properties of the fine and coarse mode aerosol types, such as their effective radii and the environmental relative humidity.
Active Subspaces of Airfoil Shape Parameterizations
Grey, Zachary J.; Constantine, Paul G.
2018-05-01
Design and optimization benefit from understanding the dependence of a quantity of interest (e.g., a design objective or constraint function) on the design variables. A low-dimensional active subspace, when present, identifies important directions in the space of design variables; perturbing a design along the active subspace associated with a particular quantity of interest changes that quantity more, on average, than perturbing the design orthogonally to the active subspace. This low-dimensional structure provides insights that characterize the dependence of quantities of interest on design variables. Airfoil design in a transonic flow field with a parameterized geometry is a popular test problem for design methodologies. We examine two particular airfoil shape parameterizations, PARSEC and CST, and study the active subspaces present in two common design quantities of interest, transonic lift and drag coefficients, under each shape parameterization. We mathematically relate the two parameterizations with a common polynomial series. The active subspaces enable low-dimensional approximations of lift and drag that relate to physical airfoil properties. In particular, we obtain and interpret a two-dimensional approximation of both transonic lift and drag, and we show how these approximation inform a multi-objective design problem.
Stray light field dependence for large astronomical space telescopes
Lightsey, Paul A.; Bowers, Charles W.
2017-09-01
Future large astronomical telescopes in space will have architectures that expose the optics to large angular extents of the sky. Options for reducing stray light coming from the sky range from enclosing the telescope in a tubular baffle to having an open telescope structure with a large sunshield to eliminate solar illumination. These two options are considered for an on-axis telescope design to explore stray light considerations. A tubular baffle design will limit the sky exposure to the solid angle of the cone in front of the telescope set by the aspect ratio of the baffle length to Primary Mirror (PM) diameter. Illumination from this portion of the sky will be limited to the PM and structures internal to the tubular baffle. Alternatively, an open structure design will allow a large portion of the sky to directly illuminate the PM and Secondary Mirror (SM) as well as illuminating sunshield and other structure surfaces which will reflect or scatter light onto the PM and SM. Portions of this illumination of the PM and SM will be scattered into the optical train as stray light. A Radiance Transfer Function (RTF) is calculated for the open architecture that determines the ratio of the stray light background radiance in the image contributed by a patch of sky having unit radiance. The full 4π steradian of sky is divided into a grid of patches, with the location of each patch defined in the telescope coordinate system. By rotating the celestial sky radiance maps into the telescope coordinate frame for a given pointing direction of the telescope, the RTF may be applied to the sky brightness and the results integrated to get the total stray light from the sky for that pointing direction. The RTF data generated for the open architecture may analyzed as a function of the expanding cone angle about the pointing direction. In this manner, the open architecture data may be used to directly compare to a tubular baffle design parameterized by allowed cone angle based on the
A Lagrangian-dependent metric space
International Nuclear Information System (INIS)
El-Tahir, A.
1989-08-01
A generalized Lagrangian-dependent metric of the static isotropic spacetime is derived. Its behaviour should be governed by imposing physical constraints allowing to avert the pathological features of gravity at the strong field domain. This would restrict the choice of the Lagrangian form. (author). 10 refs
Energy Technology Data Exchange (ETDEWEB)
Hacker, C.J.; Fries, G.A.; Pin, F.G.
1997-01-01
Few optimization methods exist for path planning of kinematically redundant manipulators. Among these, a universal method is lacking that takes advantage of a manipulator`s redundancy while satisfying possibly varying constraints and task requirements. Full Space Parameterization (FSP) is a new method that generates the entire solution space of underspecified systems of algebraic equations and then calculates the unique solution satisfying specific constraints and optimization criteria. The FSP method has been previously tested on several configurations of the redundant manipulator HERMIES-III. This report deals with the extension of the FSP driver, Inverse Kinematics On Redundant systems (IKOR), to include three-dimensional manipulation systems, possibly incorporating a mobile platform, with and without orientation control. The driver was also extended by integrating two optimized versions of the FSP solution generator as well as the ability to easily port to any manipulator. IKOR was first altered to include the ability to handle orientation control and to integrate an optimized solution generator. The resulting system was tested on a 4 degrees-of-redundancy manipulator arm and was found to successfully perform trajectories with least norm criteria while avoiding obstacles and joint limits. Next, the system was adapted and tested on a manipulator arm placed on a mobile platform yielding 7 degrees of redundancy. After successful testing on least norm trajectories while avoiding obstacles and joint limits, IKORv1.0 was developed. The system was successfully verified using comparisons with a current industry standard, the Moore Penrose Pseudo-Inverse. Finally, IKORv2.0 was created, which includes both the one shot and two step methods, manipulator portability, integration of a second optimized solution generator, and finally a more robust and usable code design.
The causal structure of spacetime is a parameterized Randers geometry
Energy Technology Data Exchange (ETDEWEB)
Skakala, Jozef; Visser, Matt, E-mail: jozef.skakala@msor.vuw.ac.nz, E-mail: matt.visser@msor.vuw.ac.nz [School of Mathematics, Statistics and Operations Research, Victoria University of Wellington, PO Box 600, Wellington (New Zealand)
2011-03-21
There is a well-established isomorphism between stationary four-dimensional spacetimes and three-dimensional purely spatial Randers geometries-these Randers geometries being a particular case of the more general class of three-dimensional Finsler geometries. We point out that in stably causal spacetimes, by using the (time-dependent) ADM decomposition, this result can be extended to general non-stationary spacetimes-the causal structure (conformal structure) of the full spacetime is completely encoded in a parameterized (t-dependent) class of Randers spaces, which can then be used to define a Fermat principle, and also to reconstruct the null cones and causal structure.
The causal structure of spacetime is a parameterized Randers geometry
International Nuclear Information System (INIS)
Skakala, Jozef; Visser, Matt
2011-01-01
There is a well-established isomorphism between stationary four-dimensional spacetimes and three-dimensional purely spatial Randers geometries-these Randers geometries being a particular case of the more general class of three-dimensional Finsler geometries. We point out that in stably causal spacetimes, by using the (time-dependent) ADM decomposition, this result can be extended to general non-stationary spacetimes-the causal structure (conformal structure) of the full spacetime is completely encoded in a parameterized (t-dependent) class of Randers spaces, which can then be used to define a Fermat principle, and also to reconstruct the null cones and causal structure.
Dependent Space and Attribute Reduction on Fuzzy Information System
Directory of Open Access Journals (Sweden)
Shu Chang
2017-01-01
Full Text Available From equivalence relation RBδ on discourse domain U, we can derive equivalence relation Rδ on the attribute set A. From equivalence relation Rδ on discourse domain A, we can derive a congruence relation on the attribute power set P(A and establish an object dependent space. And then,we discuss the reduction method of fuzzy information system on object dependent space. At last ,the example in this paper demonstrates the feasibility and effectiveness of the reduction method based on the congruence relation Tδ providing an insight into the link between equivalence relation and congruence relation of dependent spaces in the rough set. In this way, the paper can provide powerful theoritical support to the combined using of reduction method, so it is of certain practical value.
Physics in space-time with scale-dependent metrics
Balankin, Alexander S.
2013-10-01
We construct three-dimensional space Rγ3 with the scale-dependent metric and the corresponding Minkowski space-time Mγ,β4 with the scale-dependent fractal (DH) and spectral (DS) dimensions. The local derivatives based on scale-dependent metrics are defined and differential vector calculus in Rγ3 is developed. We state that Mγ,β4 provides a unified phenomenological framework for dimensional flow observed in quite different models of quantum gravity. Nevertheless, the main attention is focused on the special case of flat space-time M1/3,14 with the scale-dependent Cantor-dust-like distribution of admissible states, such that DH increases from DH=2 on the scale ≪ℓ0 to DH=4 in the infrared limit ≫ℓ0, where ℓ0 is the characteristic length (e.g. the Planck length, or characteristic size of multi-fractal features in heterogeneous medium), whereas DS≡4 in all scales. Possible applications of approach based on the scale-dependent metric to systems of different nature are briefly discussed.
A position-dependent mass harmonic oscillator and deformed space
da Costa, Bruno G.; Borges, Ernesto P.
2018-04-01
We consider canonically conjugated generalized space and linear momentum operators x^ q and p^ q in quantum mechanics, associated with a generalized translation operator which produces infinitesimal deformed displacements controlled by a deformation parameter q. A canonical transformation (x ^ ,p ^ ) →(x^ q,p^ q ) leads the Hamiltonian of a position-dependent mass particle in usual space to another Hamiltonian of a particle with constant mass in a conservative force field of the deformed space. The equation of motion for the classical phase space (x, p) may be expressed in terms of the deformed (dual) q-derivative. We revisit the problem of a q-deformed oscillator in both classical and quantum formalisms. Particularly, this canonical transformation leads a particle with position-dependent mass in a harmonic potential to a particle with constant mass in a Morse potential. The trajectories in phase spaces (x, p) and (xq, pq) are analyzed for different values of the deformation parameter. Finally, we compare the results of the problem in classical and quantum formalisms through the principle of correspondence and the WKB approximation.
Inheritance versus parameterization
DEFF Research Database (Denmark)
Ernst, Erik
2013-01-01
This position paper argues that inheritance and parameterization differ in their fundamental structure, even though they may emulate each other in many ways. Based on this, we claim that certain mechanisms, e.g., final classes, are in conflict with the nature of inheritance, and hence causes...
Space dependence of reactivity parameters on reactor dynamic perturbation measurements
International Nuclear Information System (INIS)
Maletti, R.; Ziegenbein, D.
1985-01-01
Practical application of reactor-dynamic perturbation measurements for on-power determination of differential reactivity weight of control rods and power coefficients of reactivity has shown a significant dependence of parameters on the position of outcore detectors. The space dependence of neutron flux signal in the core of a VVER-440-type reactor was measured by means of 60 self-powered neutron detectors. The greatest neutron flux alterations are located close to moved control rods and in height of the perturbation position. By means of computations, detector positions can be found in the core in which the one-point model is almost valid. (author)
Observer-dependent quantum vacua in curved space. II
International Nuclear Information System (INIS)
Castagnino, M.A.; Sztrajman, J.B.
1989-01-01
An observer-dependent Hamiltonian is introduced in order to describe massless spin-1 particles in curved space-times. The vacuum state is defined by means of Hamiltonian diagonalization and minimization, which turns out to be equivalent criteria. This method works in an arbitrary geometry, although a condition on the fluid of observers is required. Computations give the vacua commonly accepted in the literature
Rayleigh-Taylor mixing with space-dependent acceleration
Abarzhi, Snezhana
2016-11-01
We extend the momentum model to describe Rayleigh-Taylor (RT) mixing driven by a space-dependent acceleration. The acceleration is a power-law function of space coordinate, similarly to astrophysical and plasma fusion applications. In RT flow the dynamics of a fluid parcel is driven by a balance per unit mass of the rates of momentum gain and loss. We find analytical solutions in the cases of balanced and imbalanced gains and losses, and identify their dependence on the acceleration exponent. The existence is shown of two typical sub-regimes of self-similar RT mixing - the acceleration-driven Rayleigh-Taylor-type mixing and dissipation-driven Richtymer-Meshkov-type mixing with the latter being in general non-universal. Possible scenarios are proposed for transitions from the balanced dynamics to the imbalanced self-similar dynamics. Scaling and correlations properties of RT mixing are studied on the basis of dimensional analysis. Departures are outlined of RT dynamics with space-dependent acceleration from canonical cases of homogeneous turbulence as well as blast waves with first and second kind self-similarity. The work is supported by the US National Science Foundation.
Evolution of space dependent growth in the teleost Astyanax mexicanus.
Directory of Open Access Journals (Sweden)
Natalya D Gallo
Full Text Available The relationship between growth rate and environmental space is an unresolved issue in teleosts. While it is known from aquaculture studies that stocking density has a negative relationship to growth, the underlying mechanisms have not been elucidated, primarily because the growth rate of populations rather than individual fish were the subject of all previous studies. Here we investigate this problem in the teleost Astyanax mexicanus, which consists of a sighted surface-dwelling form (surface fish and several blind cave-dwelling (cavefish forms. Surface fish and cavefish are distinguished by living in spatially contrasting environments and therefore are excellent models to study the effects of environmental size on growth. Multiple controlled growth experiments with individual fish raised in confined or unconfined spaces showed that environmental size has a major impact on growth rate in surface fish, a trait we have termed space dependent growth (SDG. In contrast, SDG has regressed to different degrees in the Pachón and Tinaja populations of cavefish. Mating experiments between surface and Pachón cavefish show that SDG is inherited as a dominant trait and is controlled by multiple genetic factors. Despite its regression in blind cavefish, SDG is not affected when sighted surface fish are raised in darkness, indicating that vision is not required to perceive and react to environmental space. Analysis of plasma cortisol levels showed that an elevation above basal levels occurred soon after surface fish were exposed to confined space. This initial cortisol peak was absent in Pachón cavefish, suggesting that the effects of confined space on growth may be mediated partly through a stress response. We conclude that Astyanax reacts to confined spaces by exhibiting SDG, which has a genetic component and shows evolutionary regression during adaptation of cavefish to confined environments.
Airborne Precision Spacing (APS) Dependent Parallel Arrivals (DPA)
Smith, Colin L.
2012-01-01
The Airborne Precision Spacing (APS) team at the NASA Langley Research Center (LaRC) has been developing a concept of operations to extend the current APS concept to support dependent approaches to parallel or converging runways along with the required pilot and controller procedures and pilot interfaces. A staggered operations capability for the Airborne Spacing for Terminal Arrival Routes (ASTAR) tool was developed and designated as ASTAR10. ASTAR10 has reached a sufficient level of maturity to be validated and tested through a fast-time simulation. The purpose of the experiment was to identify and resolve any remaining issues in the ASTAR10 algorithm, as well as put the concept of operations through a practical test.
Supporting Space Systems Design via Systems Dependency Analysis Methodology
Guariniello, Cesare
The increasing size and complexity of space systems and space missions pose severe challenges to space systems engineers. When complex systems and Systems-of-Systems are involved, the behavior of the whole entity is not only due to that of the individual systems involved but also to the interactions and dependencies between the systems. Dependencies can be varied and complex, and designers usually do not perform analysis of the impact of dependencies at the level of complex systems, or this analysis involves excessive computational cost, or occurs at a later stage of the design process, after designers have already set detailed requirements, following a bottom-up approach. While classical systems engineering attempts to integrate the perspectives involved across the variety of engineering disciplines and the objectives of multiple stakeholders, there is still a need for more effective tools and methods capable to identify, analyze and quantify properties of the complex system as a whole and to model explicitly the effect of some of the features that characterize complex systems. This research describes the development and usage of Systems Operational Dependency Analysis and Systems Developmental Dependency Analysis, two methods based on parametric models of the behavior of complex systems, one in the operational domain and one in the developmental domain. The parameters of the developed models have intuitive meaning, are usable with subjective and quantitative data alike, and give direct insight into the causes of observed, and possibly emergent, behavior. The approach proposed in this dissertation combines models of one-to-one dependencies among systems and between systems and capabilities, to analyze and evaluate the impact of failures or delays on the outcome of the whole complex system. The analysis accounts for cascading effects, partial operational failures, multiple failures or delays, and partial developmental dependencies. The user of these methods can
Parameterization of solar flare dose
International Nuclear Information System (INIS)
Lamarche, A.H.; Poston, J.W.
1996-01-01
A critical aspect of missions to the moon or Mars will be the safety and health of the crew. Radiation in space is a hazard for astronauts, especially high-energy radiation following certain types of solar flares. A solar flare event can be very dangerous if astronauts are not adequately shielded because flares can deliver a very high dose in a short period of time. The goal of this research was to parameterize solar flare dose as a function of time to see if it was possible to predict solar flare occurrence, thus providing a warning time. This would allow astronauts to take corrective action and avoid receiving a dose greater than the recommended limit set by the National Council on Radiation Protection and Measurements (NCRP)
Chaos in Time-Dependent Space-Charge Potentials
Betzel, Gregory T; Sideris, Ioannis V
2005-01-01
We consider a spherically symmetric, homologously breathing, space-charge-dominated beam bunch in the spirit of the particle-core model. The question we ask is: How does the time dependence influence the population of chaotic orbits? The static beam has zero chaotic orbits; the equation of particle motion is integrable up to quadrature. This is generally not true once the bunch is set into oscillation. We quantify the population of chaotic orbits as a function of space charge and oscillation amplitude (mismatch). We also apply a newly developed measure of chaos, one that distinguishes between regular, sticky, and wildly chaotic orbits, to characterize the phase space in detail. We then introduce colored noise into the system and show how its presence modifies the dynamics. One finding is that, despite the presence of a sizeable population of chaotic orbits, halo formation in the homologously breathing beam is much less prevalent than in an envelope-matched counterpart wherein an internal collective mode is ex...
Hybrid colored noise process with space-dependent switching rates
Bressloff, Paul C.; Lawley, Sean D.
2017-07-01
A fundamental issue in the theory of continuous stochastic process is the interpretation of multiplicative white noise, which is often referred to as the Itô-Stratonovich dilemma. From a physical perspective, this reflects the need to introduce additional constraints in order to specify the nature of the noise, whereas from a mathematical perspective it reflects an ambiguity in the formulation of stochastic differential equations (SDEs). Recently, we have identified a mechanism for obtaining an Itô SDE based on a form of temporal disorder. Motivated by switching processes in molecular biology, we considered a Brownian particle that randomly switches between two distinct conformational states with different diffusivities. In each state, the particle undergoes normal diffusion (additive noise) so there is no ambiguity in the interpretation of the noise. However, if the switching rates depend on position, then in the fast switching limit one obtains Brownian motion with a space-dependent diffusivity of the Itô form. In this paper, we extend our theory to include colored additive noise. We show that the nature of the effective multiplicative noise process obtained by taking both the white-noise limit (κ →0 ) and fast switching limit (ɛ →0 ) depends on the order the two limits are taken. If the white-noise limit is taken first, then we obtain Itô, and if the fast switching limit is taken first, then we obtain Stratonovich. Moreover, the form of the effective diffusion coefficient differs in the two cases. The latter result holds even in the case of space-independent transition rates, where one obtains additive noise processes with different diffusion coefficients. Finally, we show that yet another form of multiplicative noise is obtained in the simultaneous limit ɛ ,κ →0 with ɛ /κ2 fixed.
Parameterized examination in econometrics
Malinova, Anna; Kyurkchiev, Vesselin; Spasov, Georgi
2018-01-01
The paper presents a parameterization of basic types of exam questions in Econometrics. This algorithm is used to automate and facilitate the process of examination, assessment and self-preparation of a large number of students. The proposed parameterization of testing questions reduces the time required to author tests and course assignments. It enables tutors to generate a large number of different but equivalent dynamic questions (with dynamic answers) on a certain topic, which are automatically assessed. The presented methods are implemented in DisPeL (Distributed Platform for e-Learning) and provide questions in the areas of filtering and smoothing of time-series data, forecasting, building and analysis of single-equation econometric models. Questions also cover elasticity, average and marginal characteristics, product and cost functions, measurement of monopoly power, supply, demand and equilibrium price, consumer and product surplus, etc. Several approaches are used to enable the required numerical computations in DisPeL - integration of third-party mathematical libraries, developing our own procedures from scratch, and wrapping our legacy math codes in order to modernize and reuse them.
An energetically consistent vertical mixing parameterization in CCSM4
DEFF Research Database (Denmark)
Nielsen, Søren Borg; Jochum, Markus; Eden, Carsten
2018-01-01
An energetically consistent stratification-dependent vertical mixing parameterization is implemented in the Community Climate System Model 4 and forced with energy conversion from the barotropic tides to internal waves. The structures of the resulting dissipation and diffusivity fields are compared......, however, depends greatly on the details of the vertical mixing parameterizations, where the new energetically consistent parameterization results in low thermocline diffusivities and a sharper and shallower thermocline. It is also investigated if the ocean state is more sensitive to a change in forcing...
Impact of space dependent eddy mixing on large ocean circulation
Pradal, M. A. S.; Gnanadesikan, A.; Abernathey, R. P.
2016-02-01
Throughout the ocean, mesoscale eddies stir tracers such as heat, oxygen, helium, dissolved CO2, affecting their spatial distribution. Recent work (Gnanadesikan et al., 2013) showed that changes in eddy stirring could result in changes of the volume of hypoxic and anoxic waters, leading to drastic consequences for ocean biogeochemical cycles. The parameterization of mesocale eddies in global climate models (GCMs) is two parts, based on the formulations of Redi (1982) and Gent and McWilliams (1990) which are associated with mixing parameters ARedi and AGM respectively. Numerous studies have looked at the sensitivity of ESMs to changing AGM, either alone or in combination with an ARedi parameter taken to be equivalent to the value of the AGM. By contrast the impact of the Redi parameterization in isolation remains unexplored. In a previous article, Pradal and Gnanadesikan, 2014, described the sensitivity of the climate system to a six fold increase in the Redi parameter. They found that increasing the isopycnal mixing coefficient tended to warm the climate of the planet overall, through an increase of heat absorption linked to a destabilization of the halocline in subpolar regions (particularly the Southern Ocean). This previous work varied a globally constant Redi parameter from 400m2/s to 2400m2/s. New estimates from altimetry (Abernathey and Marshall, 2013) better constrain the spatial patterns and range for the ARedi parameter. Does such spatial variation matter, and if so, where does matter? Following Gnanadesikan et al. (2013) and Pradal and Gnanadesikan, 2014 this study examines this question with a suite of Earth System Models.
Parameterization analysis and inversion for orthorhombic media
Masmoudi, Nabil
2018-05-01
Accounting for azimuthal anisotropy is necessary for the processing and inversion of wide-azimuth and wide-aperture seismic data because wave speeds naturally depend on the wave propagation direction. Orthorhombic anisotropy is considered the most effective anisotropic model that approximates the azimuthal anisotropy we observe in seismic data. In the framework of full wave form inversion (FWI), the large number of parameters describing orthorhombic media exerts a considerable trade-off and increases the non-linearity of the inversion problem. Choosing a suitable parameterization for the model, and identifying which parameters in that parameterization could be well resolved, are essential to a successful inversion. In this thesis, I derive the radiation patterns for different acoustic orthorhombic parameterization. Analyzing the angular dependence of the scattering of the parameters of different parameterizations starting with the conventionally used notation, I assess the potential trade-off between the parameters and the resolution in describing the data and inverting for the parameters. In order to build practical inversion strategies, I suggest new parameters (called deviation parameters) for a new parameterization style in orthorhombic media. The novel parameters denoted ∈d, ƞd and δd are dimensionless and represent a measure of deviation between the vertical planes in orthorhombic anisotropy. The main feature of the deviation parameters consists of keeping the scattering of the vertical transversely isotropic (VTI) parameters stationary with azimuth. Using these scattering features, we can condition FWI to invert for the parameters which the data are sensitive to, at different stages, scales, and locations in the model. With this parameterization, the data are mainly sensitive to the scattering of 3 parameters (out of six that describe an acoustic orthorhombic medium): the horizontal velocity in the x1 direction, ∈1 which provides scattering mainly near
Parameterizing convective organization
Directory of Open Access Journals (Sweden)
Brian Earle Mapes
2011-06-01
Full Text Available Lateral mixing parameters in buoyancy-driven deep convection schemes are among the most sensitive and important unknowns in atmosphere models. Unfortunately, there is not a true optimum value for plume mixing rate, but rather a dilemma or tradeoff: Excessive dilution of updrafts leads to unstable stratification bias in the mean state, while inadequate dilution allows deep convection to occur too easily, causing poor space and time distributions and variability. In this too-small parameter space, compromises are made based on competing metrics of model performance. We attempt to escape this “entrainment dilemma” by making bulk plume parameters (chiefly entrainment rate depend on a new prognostic variable (“organization,” org meant to reflect the rectified effects of subgrid-scale structure in meteorological fields. We test an org scheme in the Community Atmosphere Model (CAM5 with a new unified shallow-deep convection scheme (UW-ens, a 2-plume version of the University of Washington scheme. Since buoyant ascent involves natural selection, subgrid structure makes convection systematically deeper and stronger than the pure unorganized case: plumes of average (or randomly sampled air rising in the average environment. To reflect this, org is nonnegative, but we leave it dimensionless. A time scale characterizes its behavior (here ∼3 h for a 2o model. Currently its source is rain evaporation, but other sources can be added easily. We also let org be horizontally transported by advection, as a mass-weighted mean over the convecting layer. Linear coefficients link org to a plume ensemble, which it assists via: 1 plume base warmth above the mean temperature 2 plume radius enhancement (reduced mixing, and 3 increased probability of overlap in a multi-plume scheme, where interactions benefit later generations (this part has only been implemented in an offline toy column model. Since rain evaporation is a source for org, it functions as a time
SPace weather applications in a technology-dependent society
Ngwira, C. M.
2017-12-01
Space weather can adversely key technology assets, such as, high-voltage electric power transmission grids, oil and gas pipelines, and communications systems that are critical to national security and economy. However, the term of "space weather" is not well known in our society. This presentation will introduce key concepts related to the space weather problem and show how space weather impacts our everyday life. The goal is to promote awareness among the general public. Also, this presentation will highlight how space weather is being used to promote STEM education for community college students through the NASA internship program.
Directory of Open Access Journals (Sweden)
H. Van Diest
2008-04-01
Full Text Available The exchange of carbonyl sulfide (COS between soil and the atmosphere was investigated for three arable soils from Germany, China and Finland and one forest soil from Siberia for parameterization in the relation to ambient carbonyl sulfide (COS concentration, soil water content (WC and air temperature. All investigated soils acted as sinks for COS. A clear and distinct uptake optimum was found for the German, Chinese, Finnish and Siberian soils at 11.5%, 9%, 11.5%, and 9% soil WC, respectively, indicating that the soil WC acts as an important biological and physical parameter for characterizing the exchange of COS between soils and the atmosphere. Different optima of deposition velocities (V_{d} as observed for the Chinese, Finnish and Siberian boreal soil types in relation to their soil WC, aligned at 19% in relation to the water-filled pore space (WFPS, indicating the dominating role of gas diffusion. This interpretation was supported by the linear correlation between V_{d} and bulk density. We suggest that the uptake of COS depends on the diffusivity dominated by WFPS, a parameter depending on soil WC, soil structure and porosity of the soil.
Structural and parameteric uncertainty quantification in cloud microphysics parameterization schemes
van Lier-Walqui, M.; Morrison, H.; Kumjian, M. R.; Prat, O. P.; Martinkus, C.
2017-12-01
Atmospheric model parameterization schemes employ approximations to represent the effects of unresolved processes. These approximations are a source of error in forecasts, caused in part by considerable uncertainty about the optimal value of parameters within each scheme -- parameteric uncertainty. Furthermore, there is uncertainty regarding the best choice of the overarching structure of the parameterization scheme -- structrual uncertainty. Parameter estimation can constrain the first, but may struggle with the second because structural choices are typically discrete. We address this problem in the context of cloud microphysics parameterization schemes by creating a flexible framework wherein structural and parametric uncertainties can be simultaneously constrained. Our scheme makes no assuptions about drop size distribution shape or the functional form of parametrized process rate terms. Instead, these uncertainties are constrained by observations using a Markov Chain Monte Carlo sampler within a Bayesian inference framework. Our scheme, the Bayesian Observationally-constrained Statistical-physical Scheme (BOSS), has flexibility to predict various sets of prognostic drop size distribution moments as well as varying complexity of process rate formulations. We compare idealized probabilistic forecasts from versions of BOSS with varying levels of structural complexity. This work has applications in ensemble forecasts with model physics uncertainty, data assimilation, and cloud microphysics process studies.
Observer-dependent quantum vacua in curved space
International Nuclear Information System (INIS)
Castagnino, M.; Ferraro, R.
1986-01-01
An observer-dependent Hamiltonian is introduced. The vacuum state is defined by means of Hamiltonian diagonalization and minimization, which result to be equivalent criteria. This method encompasses a great number of known vacuum definitions, and works in an arbitrary geometry if the observer's field satisfies certain properties
International Nuclear Information System (INIS)
Lerner, Rose N.; McDonald, John
2009-01-01
A step feature in the inflaton potential can model a transient breakdown of slow-roll inflation. Here we generalize the step feature to include space-dependence, allowing it also to model a breakdown of homogeneity and isotropy. The space-dependent inflaton potential generates a classical curvature perturbation mode characterized by the wave number of the step inhomogeneity. For inhomogeneities small compared with the horizon at the step, space-dependence has a small effect on the curvature perturbation. Therefore, the smoothly oscillating quantum power spectrum predicted by the homogeneous step is robust with respect to subhorizon space-dependence. For inhomogeneities equal to or greater than the horizon at the step, the space-dependent classical mode can dominate, producing a curvature perturbation in which modes of wave number determined by the step inhomogeneity are superimposed on the oscillating power spectrum. Generation of a space-dependent step feature may therefore provide a mechanism to introduce primordial anisotropy into the curvature perturbation. Space-dependence also modifies the quantum fluctuations, in particular, via resonancelike features coming from mode coupling to amplified superhorizon modes. However, these effects are small relative to the classical modes.
Parameterization of mixing by secondary circulation in estuaries
Basdurak, N. B.; Huguenard, K. D.; Valle-Levinson, A.; Li, M.; Chant, R. J.
2017-07-01
Eddy viscosity parameterizations that depend on a gradient Richardson number Ri have been most pertinent to the open ocean. Parameterizations applicable to stratified coastal regions typically require implementation of a numerical model. Two novel parameterizations of the vertical eddy viscosity, based on Ri, are proposed here for coastal waters. One turbulence closure considers temporal changes in stratification and bottom stress and is coined the "regular fit." The alternative approach, named the "lateral fit," incorporates variability of lateral flows that are prevalent in estuaries. The two turbulence parameterization schemes are tested using data from a Self-Contained Autonomous Microstructure Profiler (SCAMP) and an Acoustic Doppler Current Profiler (ADCP) collected in the James River Estuary. The "regular fit" compares favorably to SCAMP-derived vertical eddy viscosity values but only at relatively small values of gradient Ri. On the other hand, the "lateral fit" succeeds at describing the lateral variability of eddy viscosity over a wide range of Ri. The modifications proposed to Ri-dependent eddy viscosity parameterizations allow applicability to stratified coastal regions, particularly in wide estuaries, without requiring implementation of a numerical model.
Application of the dual Youla parameterization
DEFF Research Database (Denmark)
Niemann, Hans Henrik
1999-01-01
Different applications of the parameterization of all systems stabilized by a given controller, i.e. the dual Youla parameterization, are considered in this paper. It will be shown how the parameterization can be applied in connection with controller design, adaptive controllers, model validation...
Space-Time Dependent Transport, Activation, and Dose Rates for Radioactivated Fluids.
Gavazza, Sergio
Two methods are developed to calculate the space - and time-dependent mass transport of radionuclides, their production and decay, and the associated dose rates generated from the radioactivated fluids flowing through pipes. The work couples space- and time-dependent phenomena, treated as only space- or time-dependent in the open literature. The transport and activation methodology (TAM) is used to numerically calculate space- and time-dependent transport and activation of radionuclides in fluids flowing through pipes exposed to radiation fields, and volumetric radioactive sources created by radionuclide motions. The computer program Radionuclide Activation and Transport in Pipe (RNATPA1) performs the numerical calculations required in TAM. The gamma ray dose methodology (GAM) is used to numerically calculate space- and time-dependent gamma ray dose equivalent rates from the volumetric radioactive sources determined by TAM. The computer program Gamma Ray Dose Equivalent Rate (GRDOSER) performs the numerical calculations required in GAM. The scope of conditions considered by TAM and GAM herein include (a) laminar flow in straight pipe, (b)recirculating flow schemes, (c) time-independent fluid velocity distributions, (d) space-dependent monoenergetic neutron flux distribution, (e) space- and time-dependent activation process of a single parent nuclide and transport and decay of a single daughter radionuclide, and (f) assessment of space- and time-dependent gamma ray dose rates, outside the pipe, generated by the space- and time-dependent source term distributions inside of it. The methodologies, however, can be easily extended to include all the situations of interest for solving the phenomena addressed in this dissertation. A comparison is made from results obtained by the described calculational procedures with analytical expressions. The physics of the problems addressed by the new technique and the increased accuracy versus non -space and time-dependent methods
Parameterized post-Newtonian cosmology
International Nuclear Information System (INIS)
Sanghai, Viraj A A; Clifton, Timothy
2017-01-01
Einstein’s theory of gravity has been extensively tested on solar system scales, and for isolated astrophysical systems, using the perturbative framework known as the parameterized post-Newtonian (PPN) formalism. This framework is designed for use in the weak-field and slow-motion limit of gravity, and can be used to constrain a large class of metric theories of gravity with data collected from the aforementioned systems. Given the potential of future surveys to probe cosmological scales to high precision, it is a topic of much contemporary interest to construct a similar framework to link Einstein’s theory of gravity and its alternatives to observations on cosmological scales. Our approach to this problem is to adapt and extend the existing PPN formalism for use in cosmology. We derive a set of equations that use the same parameters to consistently model both weak fields and cosmology. This allows us to parameterize a large class of modified theories of gravity and dark energy models on cosmological scales, using just four functions of time. These four functions can be directly linked to the background expansion of the universe, first-order cosmological perturbations, and the weak-field limit of the theory. They also reduce to the standard PPN parameters on solar system scales. We illustrate how dark energy models and scalar-tensor and vector-tensor theories of gravity fit into this framework, which we refer to as ‘parameterized post-Newtonian cosmology’ (PPNC). (paper)
Parameterized post-Newtonian cosmology
Sanghai, Viraj A. A.; Clifton, Timothy
2017-03-01
Einstein’s theory of gravity has been extensively tested on solar system scales, and for isolated astrophysical systems, using the perturbative framework known as the parameterized post-Newtonian (PPN) formalism. This framework is designed for use in the weak-field and slow-motion limit of gravity, and can be used to constrain a large class of metric theories of gravity with data collected from the aforementioned systems. Given the potential of future surveys to probe cosmological scales to high precision, it is a topic of much contemporary interest to construct a similar framework to link Einstein’s theory of gravity and its alternatives to observations on cosmological scales. Our approach to this problem is to adapt and extend the existing PPN formalism for use in cosmology. We derive a set of equations that use the same parameters to consistently model both weak fields and cosmology. This allows us to parameterize a large class of modified theories of gravity and dark energy models on cosmological scales, using just four functions of time. These four functions can be directly linked to the background expansion of the universe, first-order cosmological perturbations, and the weak-field limit of the theory. They also reduce to the standard PPN parameters on solar system scales. We illustrate how dark energy models and scalar-tensor and vector-tensor theories of gravity fit into this framework, which we refer to as ‘parameterized post-Newtonian cosmology’ (PPNC).
Polynomial parameterized representation of macroscopic cross section for PWR reactor
International Nuclear Information System (INIS)
Fiel, Joao Claudio B.
2015-01-01
The purpose of this work is to describe, by means of Tchebychev polynomial, a parameterized representation of the homogenized macroscopic cross section for PWR fuel element as a function of soluble boron concentration, moderator temperature, fuel temperature, moderator density and 235 U 92 enrichment. Analyzed cross sections are: fission, scattering, total, transport, absorption and capture. This parameterization enables a quick and easy determination of the problem-dependent cross-sections to be used in few groups calculations. The methodology presented here will enable to provide cross-sections values to perform PWR core calculations without the need to generate them based on computer code calculations using standard steps. The results obtained by parameterized cross-sections functions, when compared with the cross-section generated by SCALE code calculations, or when compared with K inf , generated by MCNPX code calculations, show a difference of less than 0.7 percent. (author)
Designing key-dependent chaotic S-box with larger key space
International Nuclear Information System (INIS)
Yin Ruming; Yuan Jian; Wang Jian; Shan Xiuming; Wang Xiqin
2009-01-01
The construction of cryptographically strong substitution boxes (S-boxes) is an important concern in designing secure cryptosystems. The key-dependent S-boxes designed using chaotic maps have received increasing attention in recent years. However, the key space of such S-boxes does not seem to be sufficiently large due to the limited parameter range of discretized chaotic maps. In this paper, we propose a new key-dependent S-box based on the iteration of continuous chaotic maps. We explore the continuous-valued state space of chaotic systems, and devise the discrete mapping between the input and the output of the S-box. A key-dependent S-box is constructed with the logistic map in this paper. We show that its key space could be much larger than the current key-dependent chaotic S-boxes.
A new parameterization for waveform inversion in acoustic orthorhombic media
Masmoudi, Nabil
2016-05-26
Orthorhombic anisotropic model inversion is extra challenging because of the multiple parameter nature of the inversion problem. The high number of parameters required to describe the medium exerts considerable trade-off and additional nonlinearity to a full-waveform inversion (FWI) application. Choosing a suitable set of parameters to describe the model and designing an effective inversion strategy can help in mitigating this problem. Using the Born approximation, which is the central ingredient of the FWI update process, we have derived radiation patterns for the different acoustic orthorhombic parameterizations. Analyzing the angular dependence of scattering (radiation patterns) of the parameters of different parameterizations starting with the often used Thomsen-Tsvankin parameterization, we have assessed the potential trade-off between the parameters and the resolution in describing the data and inverting for the parameters. The analysis led us to introduce new parameters ϵd, δd, and ηd, which have azimuthally dependent radiation patterns, but keep the scattering potential of the transversely isotropic parameters stationary with azimuth (azimuth independent). The novel parameters ϵd, δd, and ηd are dimensionless and represent a measure of deviation between the vertical planes in orthorhombic anisotropy. Therefore, these deviation parameters offer a new parameterization style for an acoustic orthorhombic medium described by six parameters: three vertical transversely isotropic (VTI) parameters, two deviation parameters, and one parameter describing the anisotropy in the horizontal symmetry plane. The main feature of any parameterization based on the deviation parameters, is the azimuthal independency of the modeled data with respect to the VTI parameters, which allowed us to propose practical inversion strategies based on our experience with the VTI parameters. This feature of the new parameterization style holds for even the long-wavelength components of
Lin, Shangfei; Sheng, Jinyu
2017-12-01
Depth-induced wave breaking is the primary dissipation mechanism for ocean surface waves in shallow waters. Different parametrizations were developed for parameterizing depth-induced wave breaking process in ocean surface wave models. The performance of six commonly-used parameterizations in simulating significant wave heights (SWHs) is assessed in this study. The main differences between these six parameterizations are representations of the breaker index and the fraction of breaking waves. Laboratory and field observations consisting of 882 cases from 14 sources of published observational data are used in the assessment. We demonstrate that the six parameterizations have reasonable performance in parameterizing depth-induced wave breaking in shallow waters, but with their own limitations and drawbacks. The widely-used parameterization suggested by Battjes and Janssen (1978, BJ78) has a drawback of underpredicting the SWHs in the locally-generated wave conditions and overpredicting in the remotely-generated wave conditions over flat bottoms. The drawback of BJ78 was addressed by a parameterization suggested by Salmon et al. (2015, SA15). But SA15 had relatively larger errors in SWHs over sloping bottoms than BJ78. We follow SA15 and propose a new parameterization with a dependence of the breaker index on the normalized water depth in deep waters similar to SA15. In shallow waters, the breaker index of the new parameterization has a nonlinear dependence on the local bottom slope rather than the linear dependence used in SA15. Overall, this new parameterization has the best performance with an average scatter index of ∼8.2% in comparison with the three best performing existing parameterizations with the average scatter index between 9.2% and 13.6%.
International Nuclear Information System (INIS)
Lell, R.M.; Hanan, N.A.
1987-01-01
Effects of multigroup neutron cross section generation procedures on core physics parameters for compact fast spectrum reactors have been examined. Homogeneous and space-dependent multigroup cross section sets were generated in 11 and 27 groups for a representative fast reactor core. These cross sections were used to compute various reactor physics parameters for the reference core. Coarse group structure and neglect of space-dependence in the generation procedure resulted in inaccurate computations of reactor flux and power distributions and in significant errors regarding estimates of core reactivity and control system worth. Delayed neutron fraction was insensitive to cross section treatment, and computed reactivity coefficients were only slightly sensitive. However, neutron lifetime was found to be very sensitive to cross section treatment. Deficiencies in multigroup cross sections are reflected in core nuclear design and, consequently, in system mechanical design
DEFF Research Database (Denmark)
Wang, Fei; Petersen, Dirch Hjorth; Østerberg, Frederik Westergaard
2009-01-01
In this paper, we discuss a probe spacing dependence study in order to estimate the accuracy of micro four-point probe measurements on inhomogeneous samples. Based on sensitivity calculations, both sheet resistance and Hall effect measurements are studied for samples (e.g. laser annealed samples...... the probe spacing is smaller than 1/40 of the variation wavelength, micro four-point probes can provide an accurate record of local properties with less than 1% measurement error. All the calculations agree well with previous experimental results.......) with periodic variations of sheet resistance, sheet carrier density, and carrier mobility. With a variation wavelength of Â¿, probe spacings from 0.0012 to 1002 have been applied to characterize the local variations. The calculations show that the measurement error is highly dependent on the probe spacing. When...
Phase-Space Manipulation of Ultracold Ion Bunches with Time-Dependent Fields
International Nuclear Information System (INIS)
Reijnders, M. P.; Debernardi, N.; Geer, S. B. van der; Mutsaers, P. H. A.; Vredenbregt, E. J. D.; Luiten, O. J.
2010-01-01
All applications of high brightness ion beams depend on the possibility to precisely manipulate the trajectories of the ions or, more generally, to control their phase-space distribution. We show that the combination of a laser-cooled ion source and time-dependent acceleration fields gives new possibilities to perform precise phase-space control. We demonstrate reduction of the longitudinal energy spread and realization of a lens with control over its focal length and sign, as well as the sign of the spherical aberrations. This creates new possibilities to correct for the spherical and chromatic aberrations which are presently limiting the spatial resolution.
Neutrosophic Parameterized Soft Relations and Their Applications
Directory of Open Access Journals (Sweden)
Irfan Deli
2014-06-01
Full Text Available The aim of this paper is to introduce the concept of relation on neutrosophic parameterized soft set (NP- soft sets theory. We have studied some related properties and also put forward some propositions on neutrosophic parameterized soft relation with proofs and examples. Finally the notions of symmetric, transitive, reflexive, and equivalence neutrosophic parameterized soft set relations have been established in our work. Finally a decision making method on NP-soft sets is presented.
Infrared radiation parameterizations in numerical climate models
Chou, Ming-Dah; Kratz, David P.; Ridgway, William
1991-01-01
This study presents various approaches to parameterizing the broadband transmission functions for utilization in numerical climate models. One-parameter scaling is applied to approximate a nonhomogeneous path with an equivalent homogeneous path, and the diffuse transmittances are either interpolated from precomputed tables or fit by analytical functions. Two-parameter scaling is applied to parameterizing the carbon dioxide and ozone transmission functions in both the lower and middle atmosphere. Parameterizations are given for the nitrous oxide and methane diffuse transmission functions.
Parameterized representation of macroscopic cross section for PWR reactor
International Nuclear Information System (INIS)
Fiel, João Cláudio Batista; Carvalho da Silva, Fernando; Senra Martinez, Aquilino; Leal, Luiz C.
2015-01-01
Highlights: • This work describes a parameterized representation of the homogenized macroscopic cross section for PWR reactor. • Parameterization enables a quick determination of problem-dependent cross-sections to be used in few group calculations. • This work allows generating group cross-section data to perform PWR core calculations without computer code calculations. - Abstract: The purpose of this work is to describe, by means of Chebyshev polynomials, a parameterized representation of the homogenized macroscopic cross section for PWR fuel element as a function of soluble boron concentration, moderator temperature, fuel temperature, moderator density and 235 92 U enrichment. The cross-section data analyzed are fission, scattering, total, transport, absorption and capture. The parameterization enables a quick and easy determination of problem-dependent cross-sections to be used in few group calculations. The methodology presented in this paper will allow generation of group cross-section data from stored polynomials to perform PWR core calculations without the need to generate them based on computer code calculations using standard steps. The results obtained by the proposed methodology when compared with results from the SCALE code calculations show very good agreement
CLOUD PARAMETERIZATIONS, CLOUD PHYSICS, AND THEIR CONNECTIONS: AN OVERVIEW
International Nuclear Information System (INIS)
LIU, Y.; DAUM, P.H.; CHAI, S.K.; LIU, F.
2002-01-01
This paper consists of three parts. The first part is concerned with the parameterization of cloud microphysics in climate models. We demonstrate the crucial importance of spectral dispersion of the cloud droplet size distribution in determining radiative properties of clouds (e.g., effective radius), and underline the necessity of specifying spectral dispersion in the parameterization of cloud microphysics. It is argued that the inclusion of spectral dispersion makes the issue of cloud parameterization essentially equivalent to that of the droplet size distribution function, bringing cloud parameterization to the forefront of cloud physics. The second part is concerned with theoretical investigations into the spectral shape of droplet size distributions in cloud physics. After briefly reviewing the mainstream theories (including entrainment and mixing theories, and stochastic theories), we discuss their deficiencies and the need for a paradigm shift from reductionist approaches to systems approaches. A systems theory that has recently been formulated by utilizing ideas from statistical physics and information theory is discussed, along with the major results derived from it. It is shown that the systems formalism not only easily explains many puzzles that have been frustrating the mainstream theories, but also reveals such new phenomena as scale-dependence of cloud droplet size distributions. The third part is concerned with the potential applications of the systems theory to the specification of spectral dispersion in terms of predictable variables and scale-dependence under different fluctuating environments
Parameterization Of Solar Radiation Using Neural Network
International Nuclear Information System (INIS)
Jiya, J. D.; Alfa, B.
2002-01-01
This paper presents a neural network technique for parameterization of global solar radiation. The available data from twenty-one stations is used for training the neural network and the data from other ten stations is used to validate the neural model. The neural network utilizes latitude, longitude, altitude, sunshine duration and period number to parameterize solar radiation values. The testing data was not used in the training to demonstrate the performance of the neural network in unknown stations to parameterize solar radiation. The results indicate a good agreement between the parameterized solar radiation values and actual measured values
Tuning controllers using the dual Youla parameterization
DEFF Research Database (Denmark)
Niemann, Hans Henrik; Stoustrup, Jakob
2000-01-01
This paper describes the application of the Youla parameterization of all stabilizing controllers and the dual Youla parameterization of all systems stabilized by a given controller in connection with tuning of controllers. In the uncertain case, it is shown that the use of the Youla parameteriza......This paper describes the application of the Youla parameterization of all stabilizing controllers and the dual Youla parameterization of all systems stabilized by a given controller in connection with tuning of controllers. In the uncertain case, it is shown that the use of the Youla...
Redshift space correlations and scale-dependent stochastic biasing of density peaks
Desjacques, Vincent; Sheth, Ravi K.
2010-01-01
We calculate the redshift space correlation function and the power spectrum of density peaks of a Gaussian random field. Our derivation, which is valid on linear scales k≲0.1hMpc-1, is based on the peak biasing relation given by Desjacques [Phys. Rev. DPRVDAQ1550-7998, 78, 103503 (2008)10.1103/PhysRevD.78.103503]. In linear theory, the redshift space power spectrum is Ppks(k,μ)=exp(-f2σvel2k2μ2)[bpk(k)+bvel(k)fμ2]2Pδ(k), where μ is the angle with respect to the line of sight, σvel is the one-dimensional velocity dispersion, f is the growth rate, and bpk(k) and bvel(k) are k-dependent linear spatial and velocity bias factors. For peaks, the value of σvel depends upon the functional form of bvel. When the k dependence is absent from the square brackets and bvel is set to unity, the resulting expression is assumed to describe models where the bias is linear and deterministic, but the velocities are unbiased. The peak model is remarkable because it has unbiased velocities in this same sense—peak motions are driven by dark matter flows—but, in order to achieve this, bvel must be k dependent. We speculate that this is true in general: k dependence of the spatial bias will lead to k dependence of bvel even if the biased tracers flow with the dark matter. Because of the k dependence of the linear bias parameters, standard manipulations applied to the peak model will lead to k-dependent estimates of the growth factor that could erroneously be interpreted as a signature of modified dark energy or gravity. We use the Fisher formalism to show that the constraint on the growth rate f is degraded by a factor of 2 if one allows for a k-dependent velocity bias of the peak type. Our analysis also demonstrates that the Gaussian smoothing term is part and parcel of linear theory. We discuss a simple estimate of nonlinear evolution and illustrate the effect of the peak bias on the redshift space multipoles. For k≲0.1hMpc-1, the peak bias is deterministic but k
The path dependence of district manager decision-space in Ghana
Kwamie, Aku; Dijk, van Han; Ansah, Evelyn K.; Agyepong, Irene Akua
2016-01-01
The district health system in Ghana today is characterized by high resource-uncertainty and narrow decision-space. This article builds a theory-driven historical case study to describe the influence of path-dependent administrative, fiscal and political decentralization processes on development
Leucine-based receptor sorting motifs are dependent on the spacing relative to the plasma membrane
DEFF Research Database (Denmark)
Geisler, C; Dietrich, J; Nielsen, B L
1998-01-01
Many integral membrane proteins contain leucine-based motifs within their cytoplasmic domains that mediate internalization and intracellular sorting. Two types of leucine-based motifs have been identified. One type is dependent on phosphorylation, whereas the other type, which includes an acidic...... amino acid, is constitutively active. In this study, we have investigated how the spacing relative to the plasma membrane affects the function of both types of leucine-based motifs. For phosphorylation-dependent leucine-based motifs, a minimal spacing of 7 residues between the plasma membrane...... and the phospho-acceptor was required for phosphorylation and thereby activation of the motifs. For constitutively active leucine-based motifs, a minimal spacing of 6 residues between the plasma membrane and the acidic residue was required for optimal activity of the motifs. In addition, we found that the acidic...
Radiative flux and forcing parameterization error in aerosol-free clear skies.
Pincus, Robert; Mlawer, Eli J; Oreopoulos, Lazaros; Ackerman, Andrew S; Baek, Sunghye; Brath, Manfred; Buehler, Stefan A; Cady-Pereira, Karen E; Cole, Jason N S; Dufresne, Jean-Louis; Kelley, Maxwell; Li, Jiangnan; Manners, James; Paynter, David J; Roehrig, Romain; Sekiguchi, Miho; Schwarzkopf, Daniel M
2015-07-16
Radiation parameterizations in GCMs are more accurate than their predecessorsErrors in estimates of 4 ×CO 2 forcing are large, especially for solar radiationErrors depend on atmospheric state, so global mean error is unknown.
Time-dependent gravitating solitons in five dimensional warped space-times
Giovannini, Massimo
2007-01-01
Time-dependent soliton solutions are explicitly derived in a five-dimensional theory endowed with one (warped) extra-dimension. Some of the obtained geometries, everywhere well defined and technically regular, smoothly interpolate between two five-dimensional anti-de Sitter space-times for fixed value of the conformal time coordinate. Time dependent solutions containing both topological and non-topological sectors are also obtained. Supplementary degrees of freedom can be also included and, in this case, the resulting multi-soliton solutions may describe time-dependent kink-antikink systems.
Finite-difference solution of the space-angle-lethargy-dependent slowing-down transport equation
Energy Technology Data Exchange (ETDEWEB)
Matausek, M V [Boris Kidric Vinca Institute of Nuclear Sciences, Vinca, Belgrade (Yugoslavia)
1972-07-01
A procedure has been developed for solving the slowing-down transport equation for a cylindrically symmetric reactor system. The anisotropy of the resonance neutron flux is treated by the spherical harmonics formalism, which reduces the space-angle-Iethargy-dependent transport equation to a matrix integro-differential equation in space and lethargy. Replacing further the lethargy transfer integral by a finite-difference form, a set of matrix ordinary differential equations is obtained, with lethargy-and space dependent coefficients. If the lethargy pivotal points are chosen dense enough so that the difference correction term can be ignored, this set assumes a lower block triangular form and can be solved directly by forward block substitution. As in each step of the finite-difference procedure a boundary value problem has to be solved for a non-homogeneous system of ordinary differential equations with space-dependent coefficients, application of any standard numerical procedure, for example, the finite-difference method or the method of adjoint equations, is too cumbersome and would make the whole procedure practically inapplicable. A simple and efficient approximation is proposed here, allowing analytical solution for the space dependence of the spherical-harmonics flux moments, and hence the derivation of the recurrence relations between the flux moments at successive lethargy pivotal points. According to the procedure indicated above a computer code has been developed for the CDC -3600 computer, which uses the KEDAK nuclear data file. The space and lethargy distribution of the resonance neutrons can be computed in such a detailed fashion as the neutron cross-sections are known for the reactor materials considered. The computing time is relatively short so that the code can be efficiently used, either autonomously, or as part of some complex modular scheme. Typical results will be presented and discussed in order to prove and illustrate the applicability of the
Parameterizing the interstellar dust temperature
Hocuk, S.; Szűcs, L.; Caselli, P.; Cazaux, S.; Spaans, M.; Esplugues, G. B.
2017-08-01
The temperature of interstellar dust particles is of great importance to astronomers. It plays a crucial role in the thermodynamics of interstellar clouds, because of the gas-dust collisional coupling. It is also a key parameter in astrochemical studies that governs the rate at which molecules form on dust. In 3D (magneto)hydrodynamic simulations often a simple expression for the dust temperature is adopted, because of computational constraints, while astrochemical modelers tend to keep the dust temperature constant over a large range of parameter space. Our aim is to provide an easy-to-use parametric expression for the dust temperature as a function of visual extinction (AV) and to shed light on the critical dependencies of the dust temperature on the grain composition. We obtain an expression for the dust temperature by semi-analytically solving the dust thermal balance for different types of grains and compare to a collection of recent observational measurements. We also explore the effect of ices on the dust temperature. Our results show that a mixed carbonaceous-silicate type dust with a high carbon volume fraction matches the observations best. We find that ice formation allows the dust to be warmer by up to 15% at high optical depths (AV> 20 mag) in the interstellar medium. Our parametric expression for the dust temperature is presented as Td = [ 11 + 5.7 × tanh(0.61 - log 10(AV) ]χuv1/5.9, where χuv is in units of the Draine (1978, ApJS, 36, 595) UV field.
Parameterized Linear Longitudinal Airship Model
Kulczycki, Eric; Elfes, Alberto; Bayard, David; Quadrelli, Marco; Johnson, Joseph
2010-01-01
A parameterized linear mathematical model of the longitudinal dynamics of an airship is undergoing development. This model is intended to be used in designing control systems for future airships that would operate in the atmospheres of Earth and remote planets. Heretofore, the development of linearized models of the longitudinal dynamics of airships has been costly in that it has been necessary to perform extensive flight testing and to use system-identification techniques to construct models that fit the flight-test data. The present model is a generic one that can be relatively easily specialized to approximate the dynamics of specific airships at specific operating points, without need for further system identification, and with significantly less flight testing. The approach taken in the present development is to merge the linearized dynamical equations of an airship with techniques for estimation of aircraft stability derivatives, and to thereby make it possible to construct a linearized dynamical model of the longitudinal dynamics of a specific airship from geometric and aerodynamic data pertaining to that airship. (It is also planned to develop a model of the lateral dynamics by use of the same methods.) All of the aerodynamic data needed to construct the model of a specific airship can be obtained from wind-tunnel testing and computational fluid dynamics
Space-dependent perfusion coefficient estimation in a 2D bioheat transfer problem
Bazán, Fermín S. V.; Bedin, Luciano; Borges, Leonardo S.
2017-05-01
In this work, a method for estimating the space-dependent perfusion coefficient parameter in a 2D bioheat transfer model is presented. In the method, the bioheat transfer model is transformed into a time-dependent semidiscrete system of ordinary differential equations involving perfusion coefficient values as parameters, and the estimation problem is solved through a nonlinear least squares technique. In particular, the bioheat problem is solved by the method of lines based on a highly accurate pseudospectral approach, and perfusion coefficient values are estimated by the regularized Gauss-Newton method coupled with a proper regularization parameter. The performance of the method on several test problems is illustrated numerically.
Space-time dependent couplings In N = 1 SUSY gauge theories: Anomalies and central functions
International Nuclear Information System (INIS)
Babington, J.; Erdmenger, J.
2005-01-01
We consider N = 1 supersymmetric gauge theories in which the couplings are allowed to be space-time dependent functions. Both the gauge and the superpotential couplings become chiral superfields. As has recently been shown, a new topological anomaly appears in models with space-time dependent gauge coupling. Here we show how this anomaly may be used to derive the NSVZ β-function in a particular, well-determined renormalisation scheme, both without and with chiral matter. Moreover we extend the topological anomaly analysis to theories coupled to a classical curved superspace background, and use it to derive an all-order expression for the central charge c, the coefficient of the Weyl tensor squared contribution to the conformal anomaly. We also comment on the implications of our results for the central charge a expected to be of relevance for a four-dimensional C-theorem. (author)
Space-time-dependent development of the plasma in a pulsed hollow-cathode discharge
International Nuclear Information System (INIS)
Schaefer, G.; Wages, M.
1988-01-01
This paper presents streak camera investigations on the space-time-dependent development of pulsed hollow-cathode discharges (HCD's) starting from low-current preionization discharges. The discharges started closer to the end of the cathode, then moved further into the cathode, and then spread over a longer range along the axis of the cathode. The depth range of the intense pulsed hollow-cathode plasma was found to be two to eight times the cathode diameter
Said-Houari, Belkacem
2012-03-01
In this paper, we consider a viscoelastic wave equation with an absorbing term and space-time dependent damping term. Based on the weighted energy method, and by assuming that the kernel decaying exponentially, we obtain the L2 decay rates of the solutions. More precisely, we show that the decay rates are the same as those obtained in Lin et al. (2010) [15] for the semilinear wave equation with absorption term. © 2011 Elsevier Inc.
Said-Houari, Belkacem
2012-01-01
In this paper, we consider a viscoelastic wave equation with an absorbing term and space-time dependent damping term. Based on the weighted energy method, and by assuming that the kernel decaying exponentially, we obtain the L2 decay rates of the solutions. More precisely, we show that the decay rates are the same as those obtained in Lin et al. (2010) [15] for the semilinear wave equation with absorption term. © 2011 Elsevier Inc.
Directory of Open Access Journals (Sweden)
Kunito Fukuda
2017-08-01
Full Text Available Spin-dependent space-charge-limited carrier conduction in a Schottky barrier diode using polycrystalline p-type π-conjugated molecular pentacene is explored using multiple-frequency electrically detected magnetic resonance (EDMR spectroscopy with a variable-angle configuration. The measured EDMR spectra are decomposed into two components derived, respectively, from mobile and trapped positive polarons. The linewidth of the EDMR signal for the trapped polarons increases with increasing resonance magnetic field for an in-plane configuration where the normal vector of the device substrate is perpendicular to the resonance magnetic field, while it is independent of the field for an out-of-plane configuration. This difference is consistent with the pentacene arrangement on the device substrate, where pentacene molecules exhibit a uniaxial orientation on the out-of-substrate plane. By contrast, the mobile polarons do not show anisotropic behavior with respect to the resonance magnetic field, indicating that the anisotropic effect is averaged out owing to carrier motion. These results suggest that the orientational arrangements of polycrystalline pentacene molecules in a nano thin film play a crucial role in spin-dependent electrical conduction.
Fukuda, Kunito; Asakawa, Naoki
2017-08-01
Spin-dependent space charge limited carrier conduction in a Schottky barrier diode using polycrystalline p-type π-conjugated molecular pentacene is explored using multiple-frequency electrically detected magnetic resonance (EDMR) spectroscopy with a variable-angle configuration. The measured EDMR spectra are decomposed into two components derived respectively from mobile and trapped positive polarons. The linewidth of the EDMR signal for the trapped polarons increases with increasing resonance magnetic field for an in-plane configuration where the normal vector of the device substrate is perpendicular to the resonance magnetic field, while it is independent of the field for an out-of-plane configuration. This difference is consistent with the pentacene arrangement on the device substrate, where pentacene molecules exhibit a uniaxial orientation on the out-of-substrate plane. By contrast, the mobile polarons do not show anisotropic behavior with respect to the resonance magnetic field, indicating that the anisotropic effect is averaged out owing to carrier motion. These results suggest that the orientational arrangements of polycrystalline pentacene molecules in a nano thin film play a crucial role in spin-dependent electrical conduction.
A universal parameterization of chaos in various beam-wave interactions
International Nuclear Information System (INIS)
Lee, Jae Koo; Lee, Hae June; Hur, Min Sup; Bae, InDeog; Yang, Yi
1998-01-01
The comprehensive parameter space of sell-oscillation and its period-doubling route to chaos are shown for a bounded collisionless beam-plasma system. In this parameterization, it is helpful to use a potentially universal parameter in close analogy with free-electron-laser chaos. A common parameter, which is related to the velocity slippage and the ratio of bounce to oscillation frequencies, is shown to have similar significance for different physical systems. This single parameter replaces the dependences on many input parameters, thus suitable for a simplifying and diagnostic measure of nonlinear dynamical and chaotic phenomena for various systems of particle-wave interactions. The results of independent kinetic-simulations verify those of nonlinear fluid-simulations. Other standard routes to chaos via intermittent or quasiperiodic oscillations are also shown for the undriven plasma systems. Some correlation of linear characteristics to nonlinear phenomena was noted. (author)
International Nuclear Information System (INIS)
Musazay, M.S.
1981-01-01
A solution to the space and energy dependent neutron transport equation in the framework of the consistent P-1 approximation is sought. The transport equation for thermal neutrons in a moderator of 1/v absorption and constant scattering cross section is changed into a set of coupled partial differential equations. The space dependent part is removed by assuming a cosine shaped flux due to a cosine shaped source at a very high energy. The resulting set of strongly coupled ordinary differential equations is decoupled by assuming expansion of collision density in the powers of a leakage parameter whose coefficients are energy and absorption dependent. These energy dependent coefficients are solutions of a set of weakly coupled differential equations. Series solutions to these differential equations in powers of epsilon and 1/epsilon, where epsilon = E/kT, E being the neutron energy and kT the moderator temperature in units of energy, are found. The properties of these solutions are studied extensively. Absorption appears as a parameter in the coefficients of the series. The difficulties arising in choosing the correct form of the asymptotic solutions are resolved by comparing slowing and thermalization. The limitations on the size of the slab and on the range of absorption are included in the analysis
Global model comparison of heterogeneous ice nucleation parameterizations in mixed phase clouds
Yun, Yuxing; Penner, Joyce E.
2012-04-01
A new aerosol-dependent mixed phase cloud parameterization for deposition/condensation/immersion (DCI) ice nucleation and one for contact freezing are compared to the original formulations in a coupled general circulation model and aerosol transport model. The present-day cloud liquid and ice water fields and cloud radiative forcing are analyzed and compared to observations. The new DCI freezing parameterization changes the spatial distribution of the cloud water field. Significant changes are found in the cloud ice water fraction and in the middle cloud fractions. The new DCI freezing parameterization predicts less ice water path (IWP) than the original formulation, especially in the Southern Hemisphere. The smaller IWP leads to a less efficient Bergeron-Findeisen process resulting in a larger liquid water path, shortwave cloud forcing, and longwave cloud forcing. It is found that contact freezing parameterizations have a greater impact on the cloud water field and radiative forcing than the two DCI freezing parameterizations that we compared. The net solar flux at top of atmosphere and net longwave flux at the top of the atmosphere change by up to 8.73 and 3.52 W m-2, respectively, due to the use of different DCI and contact freezing parameterizations in mixed phase clouds. The total climate forcing from anthropogenic black carbon/organic matter in mixed phase clouds is estimated to be 0.16-0.93 W m-2using the aerosol-dependent parameterizations. A sensitivity test with contact ice nuclei concentration in the original parameterization fit to that recommended by Young (1974) gives results that are closer to the new contact freezing parameterization.
Shteyne, B. A.; Nevzgodina, L. V.; Miller, A. T.
1982-01-01
The effects of space flight factors on lettuce seeds aboard the Kosmos-936 and Kosmos-1129 satellites for 20 days were studied. The phytochrome dependent (PD) reaction of light sensitive seeds was a sensitive criterion for evaluating the biological effects of space flight factors. The PD reaction of air dry lettuce seeds was suppressed after space flight, especially if the seeds were exposed to open space during the flight. Space flight affects the physiological activity of both phytochrome forms, and both the phi sub 730 dependent reactions of lettuce seeds were suppressed.
Elastic FWI for VTI media: A synthetic parameterization study
Kamath, Nishant
2016-09-06
A major challenge for multiparameter full-waveform inversion (FWI) is the inherent trade-offs (or cross-talk) between model parameters. Here, we perform FWI of multicomponent data generated for a synthetic VTI (transversely isotropic with a vertical symmetry axis) model based on a geologic section of the Valhall field. A horizontal displacement source, which excites intensive shear waves in the conventional offset range, helps provide more accurate updates to the SV-wave vertical velocity. We test three model parameterizations, which exhibit different radiation patterns and, therefore, create different parameter trade-offs. The results show that the choice of parameterization for FWI depends on the availability of long-offset data, the quality of the initial model for the anisotropy coefficients, and the parameter that needs to be resolved with the highest accuracy.
Parameterization and measurements of helical magnetic fields
International Nuclear Information System (INIS)
Fischer, W.; Okamura, M.
1997-01-01
Magnetic fields with helical symmetry can be parameterized using multipole coefficients (a n , b n ). We present a parameterization that gives the familiar multipole coefficients (a n , b n ) for straight magnets when the helical wavelength tends to infinity. To measure helical fields all methods used for straight magnets can be employed. We show how to convert the results of those measurements to obtain the desired helical multipole coefficients (a n , b n )
Menangkal Serangan SQL Injection Dengan Parameterized Query
Directory of Open Access Journals (Sweden)
Yulianingsih Yulianingsih
2016-06-01
Full Text Available Semakin meningkat pertumbuhan layanan informasi maka semakin tinggi pula tingkat kerentanan keamanan dari suatu sumber informasi. Melalui tulisan ini disajikan penelitian yang dilakukan secara eksperimen yang membahas tentang kejahatan penyerangan database secara SQL Injection. Penyerangan dilakukan melalui halaman autentikasi dikarenakan halaman ini merupakan pintu pertama akses yang seharusnya memiliki pertahanan yang cukup. Kemudian dilakukan eksperimen terhadap metode Parameterized Query untuk mendapatkan solusi terhadap permasalahan tersebut. Kata kunci— Layanan Informasi, Serangan, eksperimen, SQL Injection, Parameterized Query.
Modeling Space-Time Dependent Helium Bubble Evolution in Tungsten Armor under IFE Conditions
International Nuclear Information System (INIS)
Qiyang Hu; Shahram Sharafat; Nasr Ghoniem
2006-01-01
The High Average Power Laser (HAPL) program is a coordinated effort to develop Laser Inertial Fusion Energy. The implosion of the D-T target produces a spectrum of neutrons, X-rays, and charged particles, which arrive at the first wall (FW) at different times within about 2.5 μs at a frequency of 5 to 10 Hz. Helium is one of several high-energy charged particle constituents impinging on the candidate tungsten armored low activation ferritic steel First Wall. The spread of the implanted debris and burn helium energies results in a unique space-time dependent implantation profile that spans about 10 μm in tungsten. Co-implantation of X-rays and other ions results in spatially dependent damage profiles and rapid space-time dependent temperature spikes and gradients. The rate of helium transport and helium bubble formation will vary significantly throughout the implanted region. Furthermore, helium will also be transported via the migration of helium bubbles and non-equilibrium helium-vacancy clusters. The HEROS code was developed at UCLA to model the spatial and time-dependent helium bubble nucleation, growth, coalescence, and migration under transient damage rates and transient temperature gradients. The HEROS code is based on kinetic rate theory, which includes clustering of helium and vacancies, helium mobility, helium-vacancy cluster stability, cavity nucleation and growth and other microstructural features such as interstitial loop evolution, grain boundaries, and precipitates. The HEROS code is based on space-time discretization of reaction-diffusion type equations to account for migration of mobile species between neighboring bins as single atoms, clusters, or bubbles. HAPL chamber FW implantation conditions are used to model helium bubble evolution in the implanted tungsten. Helium recycling rate predictions are compared with experimental results of helium ion implantation experiments. (author)
Density-Dependent Spacing Behaviour and Activity Budget in Pregnant, Domestic Goats (Capra hircus).
Vas, Judit; Andersen, Inger Lise
2015-01-01
Very little is known about the spacing behaviour in social groups of domestic goats (Capra hircus) in the farm environment. In this experiment, we studied interindividual distances, movement patterns and activity budgets in pregnant goats housed at three different densities. Norwegian dairy goats were kept in stable social groups of six animals throughout pregnancy at 1, 2 or 3 m2 per individual and their spacing behaviours (i.e., distance travelled, nearest and furthest neighbour distance) and activity budgets (e.g., resting, feeding, social activities) were monitored. Observations were made in the first, second and last thirds of pregnancy in the mornings, at noon and in the afternoons of each of these phases (4.5 hours per observation period). The findings show that goats held at animal densities of 2 and 3 m2 moved longer distances when they had more space per animal and kept larger nearest and furthest neighbour distances when compared to the 1 m2 per animal density. Less feeding activity was observed at the high animal density compared to the medium and low density treatments. The phase of gestation also had an impact on almost all behavioural variables. Closer to parturition, animals moved further distances and the increase in nearest and furthest neighbour distance was more pronounced at the lower animal densities. During the last period of gestation, goats spent less time feeding and more on resting, social behaviours and engaging in other various activities. Our data suggest that more space per goat is needed for goats closer to parturition than in the early gestation phase. We concluded that in goats spacing behaviour is density-dependent and changes with stages of pregnancy and activities. Finally, the lower density allowed animals to express individual preferences regarding spacing behaviour which is important in ensuring good welfare in a farming situation.
Density-Dependent Spacing Behaviour and Activity Budget in Pregnant, Domestic Goats (Capra hircus.
Directory of Open Access Journals (Sweden)
Judit Vas
Full Text Available Very little is known about the spacing behaviour in social groups of domestic goats (Capra hircus in the farm environment. In this experiment, we studied interindividual distances, movement patterns and activity budgets in pregnant goats housed at three different densities. Norwegian dairy goats were kept in stable social groups of six animals throughout pregnancy at 1, 2 or 3 m2 per individual and their spacing behaviours (i.e., distance travelled, nearest and furthest neighbour distance and activity budgets (e.g., resting, feeding, social activities were monitored. Observations were made in the first, second and last thirds of pregnancy in the mornings, at noon and in the afternoons of each of these phases (4.5 hours per observation period. The findings show that goats held at animal densities of 2 and 3 m2 moved longer distances when they had more space per animal and kept larger nearest and furthest neighbour distances when compared to the 1 m2 per animal density. Less feeding activity was observed at the high animal density compared to the medium and low density treatments. The phase of gestation also had an impact on almost all behavioural variables. Closer to parturition, animals moved further distances and the increase in nearest and furthest neighbour distance was more pronounced at the lower animal densities. During the last period of gestation, goats spent less time feeding and more on resting, social behaviours and engaging in other various activities. Our data suggest that more space per goat is needed for goats closer to parturition than in the early gestation phase. We concluded that in goats spacing behaviour is density-dependent and changes with stages of pregnancy and activities. Finally, the lower density allowed animals to express individual preferences regarding spacing behaviour which is important in ensuring good welfare in a farming situation.
Density-Dependent Spacing Behaviour and Activity Budget in Pregnant, Domestic Goats (Capra hircus)
Vas, Judit; Andersen, Inger Lise
2015-01-01
Very little is known about the spacing behaviour in social groups of domestic goats (Capra hircus) in the farm environment. In this experiment, we studied interindividual distances, movement patterns and activity budgets in pregnant goats housed at three different densities. Norwegian dairy goats were kept in stable social groups of six animals throughout pregnancy at 1, 2 or 3 m2 per individual and their spacing behaviours (i.e. distance travelled, nearest and furthest neighbour distance) and activity budgets (e.g. resting, feeding, social activities) were monitored. Observations were made in the first, second and last thirds of pregnancy in the mornings, at noon and in the afternoons of each of these phases (4.5 hours per observation period). The findings show that goats held at animal densities of 2 and 3 m2 moved longer distances when they had more space per animal and kept larger nearest and furthest neighbour distances when compared to the 1 m2 per animal density. Less feeding activity was observed at the high animal density compared to the medium and low density treatments. The phase of gestation also had an impact on almost all behavioural variables. Closer to parturition, animals moved further distances and the increase in nearest and furthest neighbour distance was more pronounced at the lower animal densities. During the last period of gestation, goats spent less time feeding and more on resting, social behaviours and engaging in other various activities. Our data suggest that more space per goat is needed for goats closer to parturition than in the early gestation phase. We concluded that in goats spacing behaviour is density-dependent and changes with stages of pregnancy and activities. Finally, the lower density allowed animals to express individual preferences regarding spacing behaviour which is important in ensuring good welfare in a farming situation. PMID:26657240
Elmer, Franziska; Bell, James J.; Gardner, Jonathan P. A.
2018-06-01
Competition for space is a major factor affecting coral survival. Since adult coral colonies are sessile, the settlement preferences of larvae have a strong impact on the competition for space that corals will face post-metamorphosis and will therefore influence long-term survival. Laboratory-based studies show that in simplified systems coral larvae use cues to guide them to suitable settlement locations, an adaptation that enhances post-settlement survival. Settlement preferences have also been reported from the field, where coral larvae encounter a wide variety of different potential settlement surfaces as the availability of free substratum (bare space) changes over time. In this field-based study, the abundance of different encrusting organisms and bare space present on settlement tiles was compared to their abundance under newly settled pocilloporid and poritid recruits, to determine if recruits choose their settlement substratum randomly. Tiles deployed for 3, 9, 12 and 15 months were used to determine if settlement choice varied as a function of benthic community successional stage. We found that pocilloporid and poritid larvae changed their settlement preference depending on the age of the benthic community they encountered. They reacted neutrally to crustose coralline algae (CCA) on tiles deployed for 3 months when bare space was abundant, but showed a clear preference for settlement on CCA on tiles deployed for 9-15 months once bare space was limited. Simultaneously, poritid recruits showed a decreasing preference over time to settle on biofilm. This change in preference is not linked to the availability of CCA because its abundance did not change significantly between tiles deployed for 3 versus 9-15 months. These results indicate that coral recruits react to several settlement cues simultaneously, guiding them to different settlement locations as the benthos changes over time. Furthermore, recruits from both families reacted similarly, suggesting that
A Thermal Infrared Radiation Parameterization for Atmospheric Studies
Chou, Ming-Dah; Suarez, Max J.; Liang, Xin-Zhong; Yan, Michael M.-H.; Cote, Charles (Technical Monitor)
2001-01-01
This technical memorandum documents the longwave radiation parameterization developed at the Climate and Radiation Branch, NASA Goddard Space Flight Center, for a wide variety of weather and climate applications. Based on the 1996-version of the Air Force Geophysical Laboratory HITRAN data, the parameterization includes the absorption due to major gaseous absorption (water vapor, CO2, O3) and most of the minor trace gases (N2O, CH4, CFCs), as well as clouds and aerosols. The thermal infrared spectrum is divided into nine bands. To achieve a high degree of accuracy and speed, various approaches of computing the transmission function are applied to different spectral bands and gases. The gaseous transmission function is computed either using the k-distribution method or the table look-up method. To include the effect of scattering due to clouds and aerosols, the optical thickness is scaled by the single-scattering albedo and asymmetry factor. The parameterization can accurately compute fluxes to within 1% of the high spectral-resolution line-by-line calculations. The cooling rate can be accurately computed in the region extending from the surface to the 0.01-hPa level.
Subdiffusive master equation with space-dependent anomalous exponent and structural instability
Fedotov, Sergei; Falconer, Steven
2012-03-01
We derive the fractional master equation with space-dependent anomalous exponent. We analyze the asymptotic behavior of the corresponding lattice model both analytically and by Monte Carlo simulation. We show that the subdiffusive fractional equations with constant anomalous exponent μ in a bounded domain [0,L] are not structurally stable with respect to the nonhomogeneous variations of parameter μ. In particular, the Gibbs-Boltzmann distribution is no longer the stationary solution of the fractional Fokker-Planck equation whatever the space variation of the exponent might be. We analyze the random distribution of μ in space and find that in the long-time limit, the probability distribution is highly intermediate in space and the behavior is completely dominated by very unlikely events. We show that subdiffusive fractional equations with the nonuniform random distribution of anomalous exponent is an illustration of a “Black Swan,” the low probability event of the small value of the anomalous exponent that completely dominates the long-time behavior of subdiffusive systems.
Analysis of cavity effect on space- and time-dependent fast and thermal neutron energy spectra
International Nuclear Information System (INIS)
Kudo, Katsuhisa; Narita, Masakuni; Ozawa, Yasutomo.
1975-01-01
The effects of the presence of a central cavity on the space- and time-dependent neutron energy spectra in both thermal and fast neutron systems are analyzed theoretically with use made of the multi-group one-dimensional time-dependent Ssub(n) method. The thermal neutron field is also analyzed for the case of a fundamental time eigenvalue problem with the time-dependent P 1 approximation. The cavity radius is variable, and the system radius for graphite is 120 cm and for the other materials 7 cm. From the analysis of the time-dependent Ssub(n) calculations in the non-multiplying systems of polythene, light water and graphite, cavity heating is the dominant effect for the slowing-down spectrum in the initial period following fast neutron burst, and when the slowing-down spectrum comes into the thermal energy region, cavity heating shifts to cavity cooling. In the multiplying system of 235 U, cavity cooling also takes place as the spectrum approaches equilibrium after the fast neutron burst is injected. The mechanism of cavity cooling is explained analytically for the case of thermal neutron field to illustrate its physical aspects, using the time-dependent P 1 approximation. An example is given for the case of light water. (auth.)
Random walk in degree space and the time-dependent Watts-Strogatz model
Grande, H. L. Casa; Cotacallapa, M.; Hase, M. O.
2016-01-01
In this work, we propose a scheme that provides an analytical estimate for the time-dependent degree distribution of some networks. This scheme maps the problem into a random walk in degree space, and then we choose the paths that are responsible for the dominant contributions. The method is illustrated on the dynamical versions of the Erd\\"os-R\\'enyi and Watts-Strogatz graphs, which were introduced as static models in the original formulation. We have succeeded in obtaining an analytical for...
Random walk in degree space and the time-dependent Watts-Strogatz model
Casa Grande, H. L.; Cotacallapa, M.; Hase, M. O.
2017-01-01
In this work, we propose a scheme that provides an analytical estimate for the time-dependent degree distribution of some networks. This scheme maps the problem into a random walk in degree space, and then we choose the paths that are responsible for the dominant contributions. The method is illustrated on the dynamical versions of the Erdős-Rényi and Watts-Strogatz graphs, which were introduced as static models in the original formulation. We have succeeded in obtaining an analytical form for the dynamics Watts-Strogatz model, which is asymptotically exact for some regimes.
Simulation of transients with space-dependent feedback by coarse mesh flux expansion method
International Nuclear Information System (INIS)
Langenbuch, S.; Maurer, W.; Werner, W.
1975-01-01
For the simulation of the time-dependent behaviour of large LWR-cores, even the most efficient Finite-Difference (FD) methods require a prohibitive amount of computing time in order to achieve results of acceptable accuracy. Static CM-solutions computed with a mesh-size corresponding to the fuel element structure (about 20 cm) are at least as accurate as FD-solutions computed with about 5 cm mesh-size. For 3d-calculations this results in a reduction of storage requirements by a factor 60 and of computing costs by a factor 40, relative to FD-methods. These results have been obtained for pure neutronic calculations, where feedback is not taken into account. In this paper it is demonstrated that the method retains its accuracy also in kinetic calculations, even in the presence of strong space dependent feedback. (orig./RW) [de
Technique for sensitivity analysis of space- and energy-dependent burn-up calculations
International Nuclear Information System (INIS)
Williams, M.L.; White, J.R.
1979-01-01
A practical method is presented for sensitivity analysis of the very complex, space-energy dependent burn-up equations, in which the neutron and nuclide fields are coupled nonlinearly. The adjoint burn-up equations that are given are in a form which can be directly implemented into multi-dimensional depletion codes, such as VENTURE/BURNER. The data sensitivity coefficients can be used to determine the effect of data uncertainties on time-dependent depletion responses. Initial condition sensitivity coefficients provide a very effective method for computing the change in end of cycle parameters (such as k/sub eff/, fissile inventory, etc.) due to changes in nuclide concentrations at beginning of cycle
Energy Technology Data Exchange (ETDEWEB)
Analytis, G.T. [Paul Scherrer Institute (PSI), Villigen (Switzerland)
1995-09-01
A non-linear one-group space-dependent neutronic model for a finite one-dimensional core is coupled with a simple BWR feed-back model. In agreement with results obtained by the authors who originally developed the point-kinetics version of this model, we shall show numerically that stochastic reactivity excitations may result in limit-cycles and eventually in a chaotic behaviour, depending on the magnitude of the feed-back coefficient K. In the framework of this simple space-dependent model, the effect of the non-linearities on the different spatial harmonics is studied and the importance of the space-dependent effects is exemplified and assessed in terms of the importance of the higher harmonics. It is shown that under certain conditions, when the limit-cycle-type develop, the neutron spectra may exhibit strong space-dependent effects.
Statistical dynamical subgrid-scale parameterizations for geophysical flows
International Nuclear Information System (INIS)
O'Kane, T J; Frederiksen, J S
2008-01-01
Simulations of both atmospheric and oceanic circulations at given finite resolutions are strongly dependent on the form and strengths of the dynamical subgrid-scale parameterizations (SSPs) and in particular are sensitive to subgrid-scale transient eddies interacting with the retained scale topography and the mean flow. In this paper, we present numerical results for SSPs of the eddy-topographic force, stochastic backscatter, eddy viscosity and eddy-mean field interaction using an inhomogeneous statistical turbulence model based on a quasi-diagonal direct interaction approximation (QDIA). Although the theoretical description on which our model is based is for general barotropic flows, we specifically focus on global atmospheric flows where large-scale Rossby waves are present. We compare and contrast the closure-based results with an important earlier heuristic SSP of the eddy-topographic force, based on maximum entropy or statistical canonical equilibrium arguments, developed specifically for general ocean circulation models (Holloway 1992 J. Phys. Oceanogr. 22 1033-46). Our results demonstrate that where strong zonal flows and Rossby waves are present, such as in the atmosphere, maximum entropy arguments are insufficient to accurately parameterize the subgrid contributions due to eddy-eddy, eddy-topographic and eddy-mean field interactions. We contrast our atmospheric results with findings for the oceans. Our study identifies subgrid-scale interactions that are currently not parameterized in numerical atmospheric climate models, which may lead to systematic defects in the simulated circulations.
Understanding and Improving Ocean Mixing Parameterizations for modeling Climate Change
Howard, A. M.; Fells, J.; Clarke, J.; Cheng, Y.; Canuto, V.; Dubovikov, M. S.
2017-12-01
Climate is vital. Earth is only habitable due to the atmosphere&oceans' distribution of energy. Our Greenhouse Gas emissions shift overall the balance between absorbed and emitted radiation causing Global Warming. How much of these emissions are stored in the ocean vs. entering the atmosphere to cause warming and how the extra heat is distributed depends on atmosphere&ocean dynamics, which we must understand to know risks of both progressive Climate Change and Climate Variability which affect us all in many ways including extreme weather, floods, droughts, sea-level rise and ecosystem disruption. Citizens must be informed to make decisions such as "business as usual" vs. mitigating emissions to avert catastrophe. Simulations of Climate Change provide needed knowledge but in turn need reliable parameterizations of key physical processes, including ocean mixing, which greatly impacts transport&storage of heat and dissolved CO2. The turbulence group at NASA-GISS seeks to use physical theory to improve parameterizations of ocean mixing, including smallscale convective, shear driven, double diffusive, internal wave and tidal driven vertical mixing, as well as mixing by submesoscale eddies, and lateral mixing along isopycnals by mesoscale eddies. Medgar Evers undergraduates aid NASA research while learning climate science and developing computer&math skills. We write our own programs in MATLAB and FORTRAN to visualize and process output of ocean simulations including producing statistics to help judge impacts of different parameterizations on fidelity in reproducing realistic temperatures&salinities, diffusivities and turbulent power. The results can help upgrade the parameterizations. Students are introduced to complex system modeling and gain deeper appreciation of climate science and programming skills, while furthering climate science. We are incorporating climate projects into the Medgar Evers college curriculum. The PI is both a member of the turbulence group at
Energy Technology Data Exchange (ETDEWEB)
Grasselli, Federico, E-mail: federico.grasselli@unimore.it; Goldoni, Guido, E-mail: guido.goldoni@unimore.it [Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, Modena (Italy); CNR-NANO S3, Institute for Nanoscience, Via Campi 213/a, 41125 Modena (Italy); Bertoni, Andrea, E-mail: andrea.bertoni@nano.cnr.it [CNR-NANO S3, Institute for Nanoscience, Via Campi 213/a, 41125 Modena (Italy)
2015-01-21
We study the unitary propagation of a two-particle one-dimensional Schrödinger equation by means of the Split-Step Fourier method, to study the coherent evolution of a spatially indirect exciton (IX) in semiconductor heterostructures. The mutual Coulomb interaction of the electron-hole pair and the electrostatic potentials generated by external gates and acting on the two particles separately are taken into account exactly in the two-particle dynamics. As relevant examples, step/downhill and barrier/well potential profiles are considered. The space- and time-dependent evolutions during the scattering event as well as the asymptotic time behavior are analyzed. For typical parameters of GaAs-based devices, the transmission or reflection of the pair turns out to be a complex two-particle process, due to comparable and competing Coulomb, electrostatic, and kinetic energy scales. Depending on the intensity and anisotropy of the scattering potentials, the quantum evolution may result in excitation of the IX internal degrees of freedom, dissociation of the pair, or transmission in small periodic IX wavepackets due to dwelling of one particle in the barrier region. We discuss the occurrence of each process in the full parameter space of the scattering potentials and the relevance of our results for current excitronic technologies.
The path dependence of district manager decision-space in Ghana
Kwamie, Aku; van Dijk, Han; Ansah, Evelyn K; Agyepong, Irene Akua
2016-01-01
The district health system in Ghana today is characterized by high resource-uncertainty and narrow decision-space. This article builds a theory-driven historical case study to describe the influence of path-dependent administrative, fiscal and political decentralization processes on development of the district health system and district manager decision-space. Methods included a non-exhaustive literature review of democratic governance in Ghana, and key informant interviews with high-level health system officials integral to the development of the district health system. Through our analysis we identified four periods of district health system progression: (1) development of the district health system (1970–85); (2) Strengthening District Health Systems Initiative (1986–93); (3) health sector reform planning and creation of the Ghana Health Service (1994–96) and (4) health sector reform implementation (1997–2007). It was observed that district manager decision-space steadily widened during periods (1) and (2), due to increases in managerial profile, and concerted efforts at managerial capacity strengthening. Periods (3) and (4) saw initial augmentation of district health system financing, further widening managerial decision-space. However, the latter half of period 4 witnessed district manager decision-space contraction. Formalization of Ghana Health Service structures influenced by self-reinforcing tendencies towards centralized decision-making, national and donor shifts in health sector financing, and changes in key policy actors all worked to the detriment of the district health system, reversing early gains from bottom-up development of the district health system. Policy feedback mechanisms have been influenced by historical and contemporary sequencing of local government and health sector decentralization. An initial act of administrative decentralization, followed by incomplete political and fiscal decentralization has ensured that the balance of
The path dependence of district manager decision-space in Ghana.
Kwamie, Aku; van Dijk, Han; Ansah, Evelyn K; Agyepong, Irene Akua
2016-04-01
The district health system in Ghana today is characterized by high resource-uncertainty and narrow decision-space. This article builds a theory-driven historical case study to describe the influence of path-dependent administrative, fiscal and political decentralization processes on development of the district health system and district manager decision-space. Methods included a non-exhaustive literature review of democratic governance in Ghana, and key informant interviews with high-level health system officials integral to the development of the district health system. Through our analysis we identified four periods of district health system progression: (1) development of the district health system (1970-85); (2) Strengthening District Health Systems Initiative (1986-93); (3) health sector reform planning and creation of the Ghana Health Service (1994-96) and (4) health sector reform implementation (1997-2007). It was observed that district manager decision-space steadily widened during periods (1) and (2), due to increases in managerial profile, and concerted efforts at managerial capacity strengthening. Periods (3) and (4) saw initial augmentation of district health system financing, further widening managerial decision-space. However, the latter half of period 4 witnessed district manager decision-space contraction. Formalization of Ghana Health Service structures influenced by self-reinforcing tendencies towards centralized decision-making, national and donor shifts in health sector financing, and changes in key policy actors all worked to the detriment of the district health system, reversing early gains from bottom-up development of the district health system. Policy feedback mechanisms have been influenced by historical and contemporary sequencing of local government and health sector decentralization. An initial act of administrative decentralization, followed by incomplete political and fiscal decentralization has ensured that the balance of power has
International Nuclear Information System (INIS)
Yan, Y.T.
1991-01-01
The transverse motion of charged particles in a circular accelerator can be well represented by a one-turn high-order Taylor map. For particles without energy deviation, the one-turn Taylor map is a 4-dimensional polynomials of four variables. The four variables are the transverse canonical coordinates and their conjugate momenta. To include the energy deviation (off-momentum) effects, the map has to be parameterized with a smallness factor representing the off-momentum and so the Taylor map becomes a 4-dimensional polynomials of five variables. It is for this type of parameterized Taylor map that a mehtod is presented for converting it into a parameterized Dragt-Finn factorization map. Parameterized nonlinear normal form and parameterized kick factorization can thus be obtained with suitable modification of the existing technique
Analysis of sensitivity to different parameterization schemes for a subtropical cyclone
Quitián-Hernández, L.; Fernández-González, S.; González-Alemán, J. J.; Valero, F.; Martín, M. L.
2018-05-01
A sensitivity analysis to diverse WRF model physical parameterization schemes is carried out during the lifecycle of a Subtropical cyclone (STC). STCs are low-pressure systems that share tropical and extratropical characteristics, with hybrid thermal structures. In October 2014, a STC made landfall in the Canary Islands, causing widespread damage from strong winds and precipitation there. The system began to develop on October 18 and its effects lasted until October 21. Accurate simulation of this type of cyclone continues to be a major challenge because of its rapid intensification and unique characteristics. In the present study, several numerical simulations were performed using the WRF model to do a sensitivity analysis of its various parameterization schemes for the development and intensification of the STC. The combination of parameterization schemes that best simulated this type of phenomenon was thereby determined. In particular, the parameterization combinations that included the Tiedtke cumulus schemes had the most positive effects on model results. Moreover, concerning STC track validation, optimal results were attained when the STC was fully formed and all convective processes stabilized. Furthermore, to obtain the parameterization schemes that optimally categorize STC structure, a verification using Cyclone Phase Space is assessed. Consequently, the combination of parameterizations including the Tiedtke cumulus schemes were again the best in categorizing the cyclone's subtropical structure. For strength validation, related atmospheric variables such as wind speed and precipitable water were analyzed. Finally, the effects of using a deterministic or probabilistic approach in simulating intense convective phenomena were evaluated.
Single-Column Modeling, GCM Parameterizations and Atmospheric Radiation Measurement Data
International Nuclear Information System (INIS)
Somerville, R.C.J.; Iacobellis, S.F.
2005-01-01
Our overall goal is identical to that of the Atmospheric Radiation Measurement (ARM) Program: the development of new and improved parameterizations of cloud-radiation effects and related processes, using ARM data at all three ARM sites, and the implementation and testing of these parameterizations in global and regional models. To test recently developed prognostic parameterizations based on detailed cloud microphysics, we have first compared single-column model (SCM) output with ARM observations at the Southern Great Plains (SGP), North Slope of Alaska (NSA) and Topical Western Pacific (TWP) sites. We focus on the predicted cloud amounts and on a suite of radiative quantities strongly dependent on clouds, such as downwelling surface shortwave radiation. Our results demonstrate the superiority of parameterizations based on comprehensive treatments of cloud microphysics and cloud-radiative interactions. At the SGP and NSA sites, the SCM results simulate the ARM measurements well and are demonstrably more realistic than typical parameterizations found in conventional operational forecasting models. At the TWP site, the model performance depends strongly on details of the scheme, and the results of our diagnostic tests suggest ways to develop improved parameterizations better suited to simulating cloud-radiation interactions in the tropics generally. These advances have made it possible to take the next step and build on this progress, by incorporating our parameterization schemes in state-of-the-art 3D atmospheric models, and diagnosing and evaluating the results using independent data. Because the improved cloud-radiation results have been obtained largely via implementing detailed and physically comprehensive cloud microphysics, we anticipate that improved predictions of hydrologic cycle components, and hence of precipitation, may also be achievable. We are currently testing the performance of our ARM-based parameterizations in state-of-the--art global and regional
SANDYL, 3-D Time-Dependent and Space-Dependent Gamma Electron Cascade Transport by Monte-Carlo
International Nuclear Information System (INIS)
Haggmark, L.G.
1980-01-01
1 - Description of problem or function: SANDYL performs three- dimensional, time and space dependent Monte Carlo transport calculations for photon-electron cascades in complex systems. 2 - Method of solution: The problem geometry is divided into zones of homogeneous atomic composition bounded by sections of planes and quadrics. The material of each zone is a specified element or combination of elements. For a photon history, the trajectory is generated by following the photon from scattering to scattering using the various probability distributions to find distances between collisions, types of collisions, types of secondaries, and their energies and scattering angles. The photon interactions are photoelectric absorption (atomic ionization), coherent scattering, incoherent scattering, and pair production. The secondary photons which are followed include Bremsstrahlung, fluorescence photons, and positron-electron annihilation radiation. The condensed-history Monte Carlo method is used for the electron transport. In a history, the spatial steps taken by an electron are pre-computed and may include the effects of a number of collisions. The corresponding scattering angle and energy loss in the step are found from the multiple scattering distributions of these quantities. Atomic ionization and secondary particles are generated with the step according to the probabilities for their occurrence. Electron energy loss is through inelastic electron-electron collisions, Bremsstrahlung generation, and polarization of the medium (density effect). Included in the loss is the fluctuation due to the variation in the number of energy-loss collisions in a given Monte Carlo step (straggling). Scattering angular distributions are determined from elastic nuclear-collision cross sections corrected for electron-electron interactions. The secondary electrons which are followed included knock-on, pair, Auger (through atomic ionizations), Compton, and photoelectric electrons. 3
Non-perturbative Aspects of QCD and Parameterized Quark Propagator
Institute of Scientific and Technical Information of China (English)
HAN Ding-An; ZHOU Li-Juan; ZENG Ya-Guang; GU Yun-Ting; CAO Hui; MA Wei-Xing; MENG Cheng-Ju; PAN Ji-Huan
2008-01-01
Based on the Global Color Symmetry Model, the non-perturbative QCD vacuum is investigated in theparameterized fully dressed quark propagator. Our theoretical predictions for various quantities characterized the QCD vacuum are in agreement with those predicted by many other phenomenological QCD inspired models. The successful predictions clearly indicate the extensive validity of our parameterized quark propagator used here. A detailed discussion on the arbitrariness in determining the integration cut-off parameter of# in calculating QCD vacuum condensates and a good method, which avoided the dependence of calculating results on the cut-off parameter is also strongly recommended to readers.
Energy Technology Data Exchange (ETDEWEB)
Hoogenboom, J.E.; van Dam, H.; Kleiss, E.B.J.; van Uitert, G.C.; Veldhuis, D.
1982-01-01
The measured cross power spectral densities of the signals from three neutron detectors and the displacement of the control rod of the 2 MW research reactor HOR at Delft have been used to determine the space-dependent reactor transfer function, the transfer function of the automatic reactor control system and the noise sources influencing the measured signals. From a block diagram of the reactor with control system and noise sources expressions were derived for the measured cross power spectral densities, which were adjusted to satisfy the requirements following from the adopted model. Then for each frequency point the required transfer functions and noise sources could be derived. The results are in agreement with those of autoregressive modelling of the reactor control feed-back loop. A method has been developed to determine the non-linear characteristics of the automatic reactor control system by analysing the non-gaussian probability density function of the power fluctuations.
International Nuclear Information System (INIS)
Hoogenboom, J.E.
1982-01-01
The measured cross power spectral densities of the signals from three neutron detectors and the displacement of the control rod of the 2 MW research reactor HOR at Delft have been used to determine the space-dependent reactor transfer function, the transfer function of the automatic reactor control system and the noise sources influencing the measured signals. From a block diagram of the reactor with control system and noise sources expressions were derived for the measured cross power spectral densities, which were adjusted to satisfy the requirements following from the adopted model. Then for each frequency point the required transfer functions and noise sources could be derived. The results are in agreement with those of autoregressive modelling of the reactor control feed-back loop. A method has been developed to determine the non-linear characteristics of the automatic reactor control system by analysing the non-gaussian probability density function of the power fluctuations. (author)
International Nuclear Information System (INIS)
Mewdell, C.G.; Harrison, W.C.; Hawley, E.H.
1980-01-01
This paper describes the development and verification of a Non-Linear Space-Dependent Dynamic Model of a Natural Circulation Steam Generator typical of boilers used in CANDU nuclear power stations. The model contains a detailed one-dimensional dynamic description of both the primary and secondary sides of an integral pre-heater natural circulation boiler. Two-phase flow effects on the primary side are included. The secondary side uses a drift-flux model in the boiling sections and a detailed non-equilibrium point model for the steam drum. The paper presents the essential features of the final model called BOILER-2, its solution scheme, the RD-12 loop and test boiler, the boiler steady-state and transient experiments, and the comparison of the model predictions with experimental results. (author)
Abidi, Yassine; Bellassoued, Mourad; Mahjoub, Moncef; Zemzemi, Nejib
2018-03-01
In this paper, we consider the inverse problem of space dependent multiple ionic parameters identification in cardiac electrophysiology modelling from a set of observations. We use the monodomain system known as a state-of-the-art model in cardiac electrophysiology and we consider a general Hodgkin-Huxley formalism to describe the ionic exchanges at the microscopic level. This formalism covers many physiological transmembrane potential models including those in cardiac electrophysiology. Our main result is the proof of the uniqueness and a Lipschitz stability estimate of ion channels conductance parameters based on some observations on an arbitrary subdomain. The key idea is a Carleman estimate for a parabolic operator with multiple coefficients and an ordinary differential equation system.
International Nuclear Information System (INIS)
Staff, Jan E.; Niebergal, Brian P.; Ouyed, Rachid; Pudritz, Ralph E.; Cai, Kai
2010-01-01
We perform state-of-the-art, three-dimensional, time-dependent simulations of magnetized disk winds, carried out to simulation scales of 60 AU, in order to confront optical Hubble Space Telescope observations of protostellar jets. We 'observe' the optical forbidden line emission produced by shocks within our simulated jets and compare these with actual observations. Our simulations reproduce the rich structure of time-varying jets, including jet rotation far from the source, an inner (up to 400 km s -1 ) and outer (less than 100 km s -1 ) component of the jet, and jet widths of up to 20 AU in agreement with observed jets. These simulations when compared with the data are able to constrain disk wind models. In particular, models featuring a disk magnetic field with a modest radial spatial variation across the disk are favored.
Parameterization of ionization rate by auroral electron precipitation in Jupiter
Directory of Open Access Journals (Sweden)
Y. Hiraki
2008-02-01
Full Text Available We simulate auroral electron precipitation into the Jovian atmosphere in which electron multi-directional scattering and energy degradation processes are treated exactly with a Monte Carlo technique. We make a parameterization of the calculated ionization rate of the neutral gas by electron impact in a similar way as used for the Earth's aurora. Our method allows the altitude distribution of the ionization rate to be obtained as a function of an arbitrary initial energy spectrum in the range of 1–200 keV. It also includes incident angle dependence and an arbitrary density distribution of molecular hydrogen. We show that there is little dependence of the estimated ionospheric conductance on atomic species such as H and He. We compare our results with those of recent studies with different electron transport schemes by adapting our parameterization to their atmospheric conditions. We discuss the intrinsic problem of their simplified assumption. The ionospheric conductance, which is important for Jupiter's magnetosphere-ionosphere coupling system, is estimated to vary by a factor depending on the electron energy spectrum based on recent observation and modeling. We discuss this difference through the relation with field-aligned current and electron spectrum.
Parameterization of ionization rate by auroral electron precipitation in Jupiter
Directory of Open Access Journals (Sweden)
Y. Hiraki
2008-02-01
Full Text Available We simulate auroral electron precipitation into the Jovian atmosphere in which electron multi-directional scattering and energy degradation processes are treated exactly with a Monte Carlo technique. We make a parameterization of the calculated ionization rate of the neutral gas by electron impact in a similar way as used for the Earth's aurora. Our method allows the altitude distribution of the ionization rate to be obtained as a function of an arbitrary initial energy spectrum in the range of 1–200 keV. It also includes incident angle dependence and an arbitrary density distribution of molecular hydrogen. We show that there is little dependence of the estimated ionospheric conductance on atomic species such as H and He. We compare our results with those of recent studies with different electron transport schemes by adapting our parameterization to their atmospheric conditions. We discuss the intrinsic problem of their simplified assumption. The ionospheric conductance, which is important for Jupiter's magnetosphere-ionosphere coupling system, is estimated to vary by a factor depending on the electron energy spectrum based on recent observation and modeling. We discuss this difference through the relation with field-aligned current and electron spectrum.
Gain scheduling using the Youla parameterization
DEFF Research Database (Denmark)
Niemann, Hans Henrik; Stoustrup, Jakob
1999-01-01
Gain scheduling controllers are considered in this paper. The gain scheduling problem where the scheduling parameter vector cannot be measured directly, but needs to be estimated is considered. An estimation of the scheduling vector has been derived by using the Youla parameterization. The use...... in connection with H_inf gain scheduling controllers....
Marangoni convection radiative flow of dusty nanoliquid with exponential space dependent heat source
Directory of Open Access Journals (Sweden)
Basavarajappa Mahanthesh
2017-12-01
Full Text Available The flow of liquids submerged with nanoparticles is of significance to industrial applications, specifically in nuclear reactors and the cooling of nuclear systems to improve energy efficiency. The application of nanofluids in water-cooled nuclear systems can result in a significant improvement of their economic performance and/or safety margins. Therefore, in this paper, Marangoni thermal convective boundary layer dusty nanoliquid flow across a flat surface in the presence of solar radiation is studied. A two phase dusty liquid model is considered. Unlike classical temperature-dependent heat source effects, an exponential space-dependent heat source aspect is considered. Stretching variables are utilized to transform the prevailing partial differential system into a nonlinear ordinary differential system, which is then solved numerically via the Runge-Kutta-Fehlberg approach coupled with a shooting technique. The roles of physical parameters are focused in momentum and heat transport distributions. Graphical illustrations are also used to consider local and average Nusselt numbers. We examined the results under both linear and quadratic variation of the surface temperature. Our simulations established that the impact of Marangoni flow is useful for an enhancement of the heat transfer rate.
DEFF Research Database (Denmark)
Miyagi, Haruhide; Madsen, Lars Bojer
2013-01-01
We present the time-dependent restricted-active-space self-consistent-field (TD-RASSCF) theory as a framework for the time-dependent many-electron problem. The theory generalizes the multiconfigurational time-dependent Hartree-Fock (MCTDHF) theory by incorporating the restricted-active-space scheme...... well known in time-independent quantum chemistry. Optimization of the orbitals as well as the expansion coefficients at each time step makes it possible to construct the wave function accurately while using only a relatively small number of electronic configurations. In numerical calculations of high...
Radiation tolerance of a spin-dependent tunnelling magnetometer for space applications
International Nuclear Information System (INIS)
Persson, Anders; Thornell, Greger; Nguyen, Hugo
2011-01-01
To meet the increasing demand for miniaturized space instruments, efforts have been made to miniaturize traditional magnetometers, e.g. fluxgate and spin-exchange relaxation-free magnetometers. These have, for different reasons, turned out to be difficult. New technologies are needed, and promising in this respect are tunnelling magnetoresistive (TMR) magnetometers, which are based on thin film technology. However, all new space devices first have to be qualified, particularly in terms of radiation resistance. A study on TMR magnetometers' vulnerability to radiation is crucial, considering the fact that they employ a dielectric barrier, which can be susceptible to charge trapping from ionizing radiation. Here, a TMR-based magnetometer, called the spin-dependent tunnelling magnetometer (SDTM), is presented. A magnetometer chip consisting of three Wheatstone bridges, with an angular pitch of 120°, was fabricated using microstructure technology. Each branch of the Wheatstone bridges consists of eight pairs of magnetic tunnel junctions (MTJs) connected in series. Two such chips are used to measure the three-dimensional magnetic field vector. To investigate the SDTM's resistance to radiation, one branch of a Wheatstone bridge was irradiated with gamma rays from a Co 60 source with a dose rate of 10.9 rad min −1 to a total dose of 100 krad. The TMR of the branch was monitored in situ, and the easy axis TMR loop and low-frequency noise characteristics of a single MTJ were acquired before and after irradiation with the total dose. It was concluded that radiation did not influence the MTJs in any noticeable way in terms of the TMR ratio, coercivity, magnetostatic coupling or low-frequency noise
Spiegel, Orr; Leu, Stephan T; Sih, Andrew; Godfrey, Stephanie S; Bull, C Michael
2015-11-22
Understanding space use remains a major challenge for animal ecology, with implications for species interactions, disease spread, and conservation. Behavioural type (BT) may shape the space use of individuals within animal populations. Bolder or more aggressive individuals tend to be more exploratory and disperse further. Yet, to date we have limited knowledge on how space use other than dispersal depends on BT. To address this question we studied BT-dependent space-use patterns of sleepy lizards (Tiliqua rugosa) in southern Australia. We combined high-resolution global positioning system (GPS) tracking of 72 free-ranging lizards with repeated behavioural assays, and with a survey of the spatial distributions of their food and refuge resources. Bayesian generalized linear mixed models (GLMM) showed that lizards responded to the spatial distribution of resources at the neighbourhood scale and to the intensity of space use by other conspecifics (showing apparent conspecific avoidance). BT (especially aggressiveness) affected space use by lizards and their response to ecological and social factors, in a seasonally dependent manner. Many of these effects and interactions were stronger later in the season when food became scarce and environmental conditions got tougher. For example, refuge and food availability became more important later in the season and unaggressive lizards were more responsive to these predictors. These findings highlight a commonly overlooked source of heterogeneity in animal space use and improve our mechanistic understanding of processes leading to behaviourally driven disease dynamics and social structure. © 2015 The Author(s).
Directory of Open Access Journals (Sweden)
Qi-lin Xiong
Full Text Available Abstract The generalized magneto-thermoelastic problem of an infinite homogeneous isotropic microstretch half-space with temperature-dependent material properties placed in a transverse magnetic field is investigated in the context of different generalized thermoelastic theories. The upper surface of the half-space is subjected to a zonal time-dependent heat shock. By solving finite element governing equations, the solution to the problem is obtained, from which the transient magneto-thermoelastic responses, including temperature, stresses, displacements, microstretch, microrotation, induced magnetic field and induced electric field are presented graphically. Comparisons are made in the results obtained under different generalized thermoelastic theories to show some unique features of generalized thermoelasticity, and comparisons are made in the results obtained under three forms of temperature dependent material properties (absolute temperature dependent, reference temperature dependent and temperature-independent to show the effects of absolute temperature and reference temperature. Weibull or Log-normal.
Invariant box-parameterization of neutrino oscillations
International Nuclear Information System (INIS)
Weiler, Thomas J.; Wagner, DJ
1998-01-01
The model-independent 'box' parameterization of neutrino oscillations is examined. The invariant boxes are the classical amplitudes of the individual oscillating terms. Being observables, the boxes are independent of the choice of parameterization of the mixing matrix. Emphasis is placed on the relations among the box parameters due to mixing-matrix unitarity, and on the reduction of the number of boxes to the minimum basis set. Using the box algebra, we show that CP-violation may be inferred from measurements of neutrino flavor mixing even when the oscillatory factors have averaged. General analyses of neutrino oscillations among n≥3 flavors can readily determine the boxes, which can then be manipulated to yield magnitudes of mixing matrix elements
Parameterized Concurrent Multi-Party Session Types
Directory of Open Access Journals (Sweden)
Minas Charalambides
2012-08-01
Full Text Available Session types have been proposed as a means of statically verifying implementations of communication protocols. Although prior work has been successful in verifying some classes of protocols, it does not cope well with parameterized, multi-actor scenarios with inherent asynchrony. For example, the sliding window protocol is inexpressible in previously proposed session type systems. This paper describes System-A, a new typing language which overcomes many of the expressiveness limitations of prior work. System-A explicitly supports asynchrony and parallelism, as well as multiple forms of parameterization. We define System-A and show how it can be used for the static verification of a large class of asynchronous communication protocols.
Automatic Parameterization Strategy for Cardiac Electrophysiology Simulations.
Costa, Caroline Mendonca; Hoetzl, Elena; Rocha, Bernardo Martins; Prassl, Anton J; Plank, Gernot
2013-10-01
Driven by recent advances in medical imaging, image segmentation and numerical techniques, computer models of ventricular electrophysiology account for increasingly finer levels of anatomical and biophysical detail. However, considering the large number of model parameters involved parameterization poses a major challenge. A minimum requirement in combined experimental and modeling studies is to achieve good agreement in activation and repolarization sequences between model and experiment or patient data. In this study, we propose basic techniques which aid in determining bidomain parameters to match activation sequences. An iterative parameterization algorithm is implemented which determines appropriate bulk conductivities which yield prescribed velocities. In addition, a method is proposed for splitting the computed bulk conductivities into individual bidomain conductivities by prescribing anisotropy ratios.
Invariant box parameterization of neutrino oscillations
International Nuclear Information System (INIS)
Weiler, T.J.; Wagner, D.
1998-01-01
The model-independent 'box' parameterization of neutrino oscillations is examined. The invariant boxes are the classical amplitudes of the individual oscillating terms. Being observables, the boxes are independent of the choice of parameterization of the mixing matrix. Emphasis is placed on the relations among the box parameters due to mixing matrix unitarity, and on the reduction of the number of boxes to the minimum basis set. Using the box algebra, we show that CP-violation may be inferred from measurements of neutrino flavor mixing even when the oscillatory factors have averaged. General analyses of neutrino oscillations among n≥3 flavors can readily determine the boxes, which can then be manipulated to yield magnitudes of mixing matrix elements. copyright 1998 American Institute of Physics
Statistical inference and visualization in scale-space for spatially dependent images
Vaughan, Amy
2012-03-01
SiZer (SIgnificant ZERo crossing of the derivatives) is a graphical scale-space visualization tool that allows for statistical inferences. In this paper we develop a spatial SiZer for finding significant features and conducting goodness-of-fit tests for spatially dependent images. The spatial SiZer utilizes a family of kernel estimates of the image and provides not only exploratory data analysis but also statistical inference with spatial correlation taken into account. It is also capable of comparing the observed image with a specific null model being tested by adjusting the statistical inference using an assumed covariance structure. Pixel locations having statistically significant differences between the image and a given null model are highlighted by arrows. The spatial SiZer is compared with the existing independent SiZer via the analysis of simulated data with and without signal on both planar and spherical domains. We apply the spatial SiZer method to the decadal temperature change over some regions of the Earth. © 2011 The Korean Statistical Society.
Anomalous temperature dependence of layer spacing of de Vries liquid crystals: Compensation model
Energy Technology Data Exchange (ETDEWEB)
Merkel, K. [Central Mining Institute, Katowice 40-166 (Poland); Kocot, A. [Institute of Physics, Silesian University, Katowice 40-007 (Poland); Vij, J. K., E-mail: jvij@tcd.ie [Department of Electronic and Electrical Engineering, Trinity College, The University of Dublin, Dublin 2 (Ireland); Stevenson, P. J.; Panov, A.; Rodriguez, D. [School of Chemistry and Chemical Engineering, Queens University Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom)
2016-06-13
Smectic liquid crystals that exhibit temperature independent layer thickness offer technological advantages for their use in displays and photonic devices. The dependence of the layer spacing in SmA and SmC phases of de Vries liquid crystals is found to exhibit distinct features. On entering the SmC phase, the layer thickness initially decreases below SmA to SmC (T{sub A–C}) transition temperature but increases anomalously with reducing temperature despite the molecular tilt increasing. This anomalous observation is being explained quantitatively. Results of IR spectroscopy show that layer shrinkage is caused by tilt of the mesogen's rigid core, whereas the expansion is caused by the chains getting more ordered with reducing temperature. This mutual compensation arising from molecular fragments contributing to the layer thickness differs from the previous models. The orientational order parameter of the rigid core of the mesogen provides direct evidence for de Vries cone model in the SmA phase for the two compounds investigated.
Automatic Parameterization Strategy for Cardiac Electrophysiology Simulations
Costa, Caroline Mendonca; Hoetzl, Elena; Rocha, Bernardo Martins; Prassl, Anton J; Plank, Gernot
2013-01-01
Driven by recent advances in medical imaging, image segmentation and numerical techniques, computer models of ventricular electrophysiology account for increasingly finer levels of anatomical and biophysical detail. However, considering the large number of model parameters involved parameterization poses a major challenge. A minimum requirement in combined experimental and modeling studies is to achieve good agreement in activation and repolarization sequences between model and experiment or ...
Directory of Open Access Journals (Sweden)
Pedro Saa
2015-04-01
Full Text Available Kinetic models provide the means to understand and predict the dynamic behaviour of enzymes upon different perturbations. Despite their obvious advantages, classical parameterizations require large amounts of data to fit their parameters. Particularly, enzymes displaying complex reaction and regulatory (allosteric mechanisms require a great number of parameters and are therefore often represented by approximate formulae, thereby facilitating the fitting but ignoring many real kinetic behaviours. Here, we show that full exploration of the plausible kinetic space for any enzyme can be achieved using sampling strategies provided a thermodynamically feasible parameterization is used. To this end, we developed a General Reaction Assembly and Sampling Platform (GRASP capable of consistently parameterizing and sampling accurate kinetic models using minimal reference data. The former integrates the generalized MWC model and the elementary reaction formalism. By formulating the appropriate thermodynamic constraints, our framework enables parameterization of any oligomeric enzyme kinetics without sacrificing complexity or using simplifying assumptions. This thermodynamically safe parameterization relies on the definition of a reference state upon which feasible parameter sets can be efficiently sampled. Uniform sampling of the kinetics space enabled dissecting enzyme catalysis and revealing the impact of thermodynamics on reaction kinetics. Our analysis distinguished three reaction elasticity regions for common biochemical reactions: a steep linear region (0> ΔGr >-2 kJ/mol, a transition region (-2> ΔGr >-20 kJ/mol and a constant elasticity region (ΔGr <-20 kJ/mol. We also applied this framework to model more complex kinetic behaviours such as the monomeric cooperativity of the mammalian glucokinase and the ultrasensitive response of the phosphoenolpyruvate carboxylase of Escherichia coli. In both cases, our approach described appropriately not only
A Solar Radiation Parameterization for Atmospheric Studies. Volume 15
Chou, Ming-Dah; Suarez, Max J. (Editor)
1999-01-01
The solar radiation parameterization (CLIRAD-SW) developed at the Goddard Climate and Radiation Branch for application to atmospheric models are described. It includes the absorption by water vapor, O3, O2, CO2, clouds, and aerosols and the scattering by clouds, aerosols, and gases. Depending upon the nature of absorption, different approaches are applied to different absorbers. In the ultraviolet and visible regions, the spectrum is divided into 8 bands, and single O3 absorption coefficient and Rayleigh scattering coefficient are used for each band. In the infrared, the spectrum is divided into 3 bands, and the k-distribution method is applied for water vapor absorption. The flux reduction due to O2 is derived from a simple function, while the flux reduction due to CO2 is derived from precomputed tables. Cloud single-scattering properties are parameterized, separately for liquid drops and ice, as functions of water amount and effective particle size. A maximum-random approximation is adopted for the overlapping of clouds at different heights. Fluxes are computed using the Delta-Eddington approximation.
Directory of Open Access Journals (Sweden)
M. Keller
2018-04-01
Full Text Available Climate models project an increase in heavy precipitation events in response to greenhouse gas forcing. Important elements of such events are rain showers and thunderstorms, which are poorly represented in models with parameterized convection. In this study, simulations with 12 km horizontal grid spacing (convection-parameterizing model, CPM and 2 km grid spacing (convection-resolving model, CRM are employed to investigate the change in the diurnal cycle of convection with warmer climate. For this purpose, simulations of 11 days in June 2007 with a pronounced diurnal cycle of convection are compared with surrogate simulations from the same period. The surrogate climate simulations mimic a future climate with increased temperatures but unchanged relative humidity and similar synoptic-scale circulation. Two temperature scenarios are compared: one with homogeneous warming (HW using a vertically uniform warming and the other with vertically dependent warming (VW that enables changes in lapse rate.The two sets of simulations with parameterized and explicit convection exhibit substantial differences, some of which are well known from the literature. These include differences in the timing and amplitude of the diurnal cycle of convection, and the frequency of precipitation with low intensities. The response to climate change is much less studied. We can show that stratification changes have a strong influence on the changes in convection. Precipitation is strongly increasing for HW but decreasing for the VW simulations. For cloud type frequencies, virtually no changes are found for HW, but a substantial reduction in high clouds is found for VW. Further, we can show that the climate change signal strongly depends upon the horizontal resolution. In particular, significant differences between CPM and CRM are found in terms of the radiative feedbacks, with CRM exhibiting a stronger negative feedback in the top-of-the-atmosphere energy budget.
Keller, Michael; Kröner, Nico; Fuhrer, Oliver; Lüthi, Daniel; Schmidli, Juerg; Stengel, Martin; Stöckli, Reto; Schär, Christoph
2018-04-01
Climate models project an increase in heavy precipitation events in response to greenhouse gas forcing. Important elements of such events are rain showers and thunderstorms, which are poorly represented in models with parameterized convection. In this study, simulations with 12 km horizontal grid spacing (convection-parameterizing model, CPM) and 2 km grid spacing (convection-resolving model, CRM) are employed to investigate the change in the diurnal cycle of convection with warmer climate. For this purpose, simulations of 11 days in June 2007 with a pronounced diurnal cycle of convection are compared with surrogate simulations from the same period. The surrogate climate simulations mimic a future climate with increased temperatures but unchanged relative humidity and similar synoptic-scale circulation. Two temperature scenarios are compared: one with homogeneous warming (HW) using a vertically uniform warming and the other with vertically dependent warming (VW) that enables changes in lapse rate. The two sets of simulations with parameterized and explicit convection exhibit substantial differences, some of which are well known from the literature. These include differences in the timing and amplitude of the diurnal cycle of convection, and the frequency of precipitation with low intensities. The response to climate change is much less studied. We can show that stratification changes have a strong influence on the changes in convection. Precipitation is strongly increasing for HW but decreasing for the VW simulations. For cloud type frequencies, virtually no changes are found for HW, but a substantial reduction in high clouds is found for VW. Further, we can show that the climate change signal strongly depends upon the horizontal resolution. In particular, significant differences between CPM and CRM are found in terms of the radiative feedbacks, with CRM exhibiting a stronger negative feedback in the top-of-the-atmosphere energy budget.
Directory of Open Access Journals (Sweden)
Selvaraj Suganya
2016-01-01
Full Text Available A recent nonlinear alternative for multivalued contractions in Fréchet spaces thanks to Frigon fixed point theorem consolidated with semigroup theory is utilized to examine the existence results for fractional neutral integrodifferential inclusions (FNIDI with state-dependent delay (SDD. An example is described to represent the hypothesis.
Parameterized and resolved Southern Ocean eddy compensation
Poulsen, Mads B.; Jochum, Markus; Nuterman, Roman
2018-04-01
The ability to parameterize Southern Ocean eddy effects in a forced coarse resolution ocean general circulation model is assessed. The transient model response to a suite of different Southern Ocean wind stress forcing perturbations is presented and compared to identical experiments performed with the same model in 0.1° eddy-resolving resolution. With forcing of present-day wind stress magnitude and a thickness diffusivity formulated in terms of the local stratification, it is shown that the Southern Ocean residual meridional overturning circulation in the two models is different in structure and magnitude. It is found that the difference in the upper overturning cell is primarily explained by an overly strong subsurface flow in the parameterized eddy-induced circulation while the difference in the lower cell is mainly ascribed to the mean-flow overturning. With a zonally constant decrease of the zonal wind stress by 50% we show that the absolute decrease in the overturning circulation is insensitive to model resolution, and that the meridional isopycnal slope is relaxed in both models. The agreement between the models is not reproduced by a 50% wind stress increase, where the high resolution overturning decreases by 20%, but increases by 100% in the coarse resolution model. It is demonstrated that this difference is explained by changes in surface buoyancy forcing due to a reduced Antarctic sea ice cover, which strongly modulate the overturning response and ocean stratification. We conclude that the parameterized eddies are able to mimic the transient response to altered wind stress in the high resolution model, but partly misrepresent the unperturbed Southern Ocean meridional overturning circulation and associated heat transports.
Time-dependent restricted-active-space self-consistent-field theory for bosonic many-body systems
International Nuclear Information System (INIS)
Lévêque, Camille; Madsen, Lars Bojer
2017-01-01
We develop an ab initio time-dependent wavefunction based theory for the description of a many-body system of cold interacting bosons. Like the multi-configurational time-dependent Hartree method for bosons (MCTDHB), the theory is based on a configurational interaction Ansatz for the many-body wavefunction with time-dependent self-consistent-field orbitals. The theory generalizes the MCTDHB method by incorporating restrictions on the active space of the orbital excitations. The restrictions are specified based on the physical situation at hand. The equations of motion of this time-dependent restricted-active-space self-consistent-field (TD-RASSCF) theory are derived. The similarity between the formal development of the theory for bosons and fermions is discussed. The restrictions on the active space allow the theory to be evaluated under conditions where other wavefunction based methods due to exponential scaling in the numerical effort cannot, and to clearly identify the excitations that are important for an accurate description, significantly beyond the mean-field approach. For ground state calculations we find it to be important to allow a few particles to have the freedom to move in many orbitals, an insight facilitated by the flexibility of the restricted-active-space Ansatz . Moreover, we find that a high accuracy can be obtained by including only even excitations in the many-body self-consistent-field wavefunction. Time-dependent simulations of harmonically trapped bosons subject to a quenching of their noncontact interaction, show failure of the mean-field Gross-Pitaevskii approach within a fraction of a harmonic oscillation period. The TD-RASSCF theory remains accurate at much reduced computational cost compared to the MCTDHB method. Exploring the effect of changes of the restricted-active-space allows us to identify that even self-consistent-field excitations are mainly responsible for the accuracy of the method. (paper)
New superintegrable models with position-dependent mass from Bertrand's Theorem on curved spaces
Energy Technology Data Exchange (ETDEWEB)
Ballesteros, A; Herranz, F J [Departamento de Fisica, Universidad de Burgos, E-09001 Burgos (Spain); Enciso, A [Departamento de Fisica Teorica II, Universidad Complutense, E-28040 Madrid (Spain); Ragnisco, O; Riglioni, D, E-mail: angelb@ubu.es, E-mail: aenciso@fis.ucm.es, E-mail: fjherranz@ubu.es, E-mail: ragnisco@fis.uniroma3.it, E-mail: riglioni@fis.uniroma3.it [Dipartimento di Fisica, Universita di Roma Tre and Instituto Nazionale di Fisica Nucleare sezione di Roma Tre, Via Vasca Navale 84, I-00146 Roma (Italy)
2011-03-01
A generalized version of Bertrand's theorem on spherically symmetric curved spaces is presented. This result is based on the classification of (3+1)-dimensional (Lorentzian) Bertrand spacetimes, that gives rise to two families of Hamiltonian systems defined on certain 3-dimensional (Riemannian) spaces. These two systems are shown to be either the Kepler or the oscillator potentials on the corresponding Bertrand spaces, and both of them are maximally superintegrable. Afterwards, the relationship between such Bertrand Hamiltonians and position-dependent mass systems is explicitly established. These results are illustrated through the example of a superintegrable (nonlinear) oscillator on a Bertrand-Darboux space, whose quantization and physical features are also briefly addressed.
Consider the category: The effect of spacing depends on individual learning histories.
Slone, Lauren K; Sandhofer, Catherine M
2017-07-01
The spacing effect refers to increased retention following learning instances that are spaced out in time compared with massed together in time. By one account, the advantages of spaced learning should be independent of task particulars and previous learning experiences given that spacing effects have been demonstrated in a variety of tasks across the lifespan. However, by another account, spaced learning should be affected by previous learning because past learning affects the memory and attention processes that form the crux of the spacing effect. The current study investigated whether individuals' learning histories affect the role of spacing in category learning. We examined the effect of spacing on 24 2- to 3.5-year-old children's learning of categories organized by properties to which children's previous learning experiences have biased them to attend (i.e., shape) and properties to which children are less biased to attend (i.e., texture and color). Spaced presentations led to significantly better learning of shape categories, but not of texture or color categories, compared with massed presentations. In addition, generalized estimating equations analyses revealed positive relations between the size of children's "shape-side" productive vocabularies and their shape category learning and between the size of children's "against-the-system" productive vocabularies and their texture category learning. These results suggest that children's attention to and memory for novel object categories are strongly related to their individual word-learning histories. Moreover, children's learned attentional biases affected the types of categories for which spacing facilitated learning. These findings highlight the importance of considering how learners' previous experiences may influence future learning. Copyright © 2017 Elsevier Inc. All rights reserved.
Midgley, S M
2004-01-21
A novel parameterization of x-ray interaction cross-sections is developed, and employed to describe the x-ray linear attenuation coefficient and mass energy absorption coefficient for both elements and mixtures. The new parameterization scheme addresses the Z-dependence of elemental cross-sections (per electron) using a simple function of atomic number, Z. This obviates the need for a complicated mathematical formalism. Energy dependent coefficients describe the Z-direction curvature of the cross-sections. The composition dependent quantities are the electron density and statistical moments describing the elemental distribution. We show that it is possible to describe elemental cross-sections for the entire periodic table and at energies above the K-edge (from 6 keV to 125 MeV), with an accuracy of better than 2% using a parameterization containing not more than five coefficients. For the biologically important elements 1 coefficients. At higher energies, the parameterization uses fewer coefficients with only two coefficients needed at megavoltage energies.
Liu, S.; Ng, G. H. C.
2017-12-01
The global plant database has revealed that plant traits can vary more within a plant functional type (PFT) than among different PFTs, indicating that the current paradigm in ecohydrogical models of specifying fixed parameters based solely on plant functional type (PFT) could potentially bias simulations. Although some recent modeling studies have attempted to incorporate this observed plant trait variability, many failed to consider uncertainties due to sparse global observation, or they omitted spatial and/or temporal variability in the traits. Here we present a stochastic parameterization for prognostic vegetation simulations that are stochastic in time and space in order to represent plant trait plasticity - the process by which trait differences arise. We have developed the new PFT parameterization within the Community Land Model 4.5 (CLM 4.5) and tested the method for a desert shrubland watershed in the Mojave Desert, where fixed parameterizations cannot represent acclimation to desert conditions. Spatiotemporally correlated plant trait parameters were first generated based on TRY statistics and were then used to implement ensemble runs for the study area. The new PFT parameterization was then further conditioned on field measurements of soil moisture and remotely sensed observations of leaf-area-index to constrain uncertainties in the sparse global database. Our preliminary results show that incorporating data-conditioned, variable PFT parameterizations strongly affects simulated soil moisture and water fluxes, compared with default simulations. The results also provide new insights about correlations among plant trait parameters and between traits and environmental conditions in the desert shrubland watershed. Our proposed stochastic PFT parameterization method for ecohydrological models has great potential in advancing our understanding of how terrestrial ecosystems are predicted to adapt to variable environmental conditions.
Hall, Carlton Raden
A major objective of remote sensing is determination of biochemical and biophysical characteristics of plant canopies utilizing high spectral resolution sensors. Canopy reflectance signatures are dependent on absorption and scattering processes of the leaf, canopy properties, and the ground beneath the canopy. This research investigates, through field and laboratory data collection, and computer model parameterization and simulations, the relationships between leaf optical properties, canopy biophysical features, and the nadir viewed above-canopy reflectance signature. Emphasis is placed on parameterization and application of an existing irradiance radiative transfer model developed for aquatic systems. Data and model analyses provide knowledge on the relative importance of leaves and canopy biophysical features in estimating the diffuse absorption a(lambda,m-1), diffuse backscatter b(lambda,m-1), beam attenuation alpha(lambda,m-1), and beam to diffuse conversion c(lambda,m-1 ) coefficients of the two-flow irradiance model. Data sets include field and laboratory measurements from three plant species, live oak (Quercus virginiana), Brazilian pepper (Schinus terebinthifolius) and grapefruit (Citrus paradisi) sampled on Cape Canaveral Air Force Station and Kennedy Space Center Florida in March and April of 1997. Features measured were depth h (m), projected foliage coverage PFC, leaf area index LAI, and zenith leaf angle. Optical measurements, collected with a Spectron SE 590 high sensitivity narrow bandwidth spectrograph, included above canopy reflectance, internal canopy transmittance and reflectance and bottom reflectance. Leaf samples were returned to laboratory where optical and physical and chemical measurements of leaf thickness, leaf area, leaf moisture and pigment content were made. A new term, the leaf volume correction index LVCI was developed and demonstrated in support of model coefficient parameterization. The LVCI is based on angle adjusted leaf
International Nuclear Information System (INIS)
Yoon, Sangcheol; Hwang, Inchan; Park, Byoungchoo
2015-01-01
The loss of photocurrent efficiency by space-charge effects in organic solar cells with energetic disorder was investigated to account for how energetic disorder incorporates space-charge effects, utilizing a drift-diffusion model with field-dependent charge-pair dissociation and suppressed bimolecular recombination. Energetic disorder, which induces the Poole–Frenkel behavior of charge carrier mobility, is known to decrease the mobility of charge carriers and thus reduces photovoltaic performance. We found that even if the mobilities are the same in the absence of space-charge effects, the degree of energetic disorder can be an additional parameter affecting photocurrent efficiency when space-charge effects occur. Introducing the field-dependence parameter that reflects the energetic disorder, the behavior of efficiency loss with energetic disorder can differ depending on which charge carrier is subject to energetic disorder. While the energetic disorder that is applied to higher-mobility charge carriers decreases photocurrent efficiency further, the efficiency loss can be suppressed when energetic disorder is applied to lower-mobility charge carriers. (paper)
A subgrid parameterization scheme for precipitation
Directory of Open Access Journals (Sweden)
S. Turner
2012-04-01
Full Text Available With increasing computing power, the horizontal resolution of numerical weather prediction (NWP models is improving and today reaches 1 to 5 km. Nevertheless, clouds and precipitation formation are still subgrid scale processes for most cloud types, such as cumulus and stratocumulus. Subgrid scale parameterizations for water vapor condensation have been in use for many years and are based on a prescribed probability density function (PDF of relative humidity spatial variability within the model grid box, thus providing a diagnosis of the cloud fraction. A similar scheme is developed and tested here. It is based on a prescribed PDF of cloud water variability and a threshold value of liquid water content for droplet collection to derive a rain fraction within the model grid. Precipitation of rainwater raises additional concerns relative to the overlap of cloud and rain fractions, however. The scheme is developed following an analysis of data collected during field campaigns in stratocumulus (DYCOMS-II and fair weather cumulus (RICO and tested in a 1-D framework against large eddy simulations of these observed cases. The new parameterization is then implemented in a 3-D NWP model with a horizontal resolution of 2.5 km to simulate real cases of precipitating cloud systems over France.
Anselmi, Pasquale; Stefanutti, Luca; de Chiusole, Debora; Robusto, Egidio
2017-11-01
The gain-loss model (GaLoM) is a formal model for assessing knowledge and learning. In its original formulation, the GaLoM assumes independence among the skills. Such an assumption is not reasonable in several domains, in which some preliminary knowledge is the foundation for other knowledge. This paper presents an extension of the GaLoM to the case in which the skills are not independent, and the dependence relation among them is described by a well-graded competence space. The probability of mastering skill s at the pretest is conditional on the presence of all skills on which s depends. The probabilities of gaining or losing skill s when moving from pretest to posttest are conditional on the mastery of s at the pretest, and on the presence at the posttest of all skills on which s depends. Two formulations of the model are presented, in which the learning path is allowed to change from pretest to posttest or not. A simulation study shows that models based on the true competence space obtain a better fit than models based on false competence spaces, and are also characterized by a higher assessment accuracy. An empirical application shows that models based on pedagogically sound assumptions about the dependencies among the skills obtain a better fit than models assuming independence among the skills. © 2017 The British Psychological Society.
Aerosol-Cloud-Precipitation Interactions in WRF Model:Sensitivity to Autoconversion Parameterization
Institute of Scientific and Technical Information of China (English)
解小宁; 刘晓东
2015-01-01
Cloud-to-rain autoconversion process is an important player in aerosol loading, cloud morphology, and precipitation variations because it can modulate cloud microphysical characteristics depending on the par-ticipation of aerosols, and aff ects the spatio-temporal distribution and total amount of precipitation. By applying the Kessler, the Khairoutdinov-Kogan (KK), and the Dispersion autoconversion parameterization schemes in a set of sensitivity experiments, the indirect eff ects of aerosols on clouds and precipitation are investigated for a deep convective cloud system in Beijing under various aerosol concentration backgrounds from 50 to 10000 cm−3. Numerical experiments show that aerosol-induced precipitation change is strongly dependent on autoconversion parameterization schemes. For the Kessler scheme, the average cumulative precipitation is enhanced slightly with increasing aerosols, whereas surface precipitation is reduced signifi-cantly with increasing aerosols for the KK scheme. Moreover, precipitation varies non-monotonically for the Dispersion scheme, increasing with aerosols at lower concentrations and decreasing at higher concentrations. These diff erent trends of aerosol-induced precipitation change are mainly ascribed to diff erences in rain wa-ter content under these three autoconversion parameterization schemes. Therefore, this study suggests that accurate parameterization of cloud microphysical processes, particularly the cloud-to-rain autoconversion process, is needed for improving the scientifi c understanding of aerosol-cloud-precipitation interactions.
Hoose, C.; Hande, L. B.; Mohler, O.; Niemand, M.; Paukert, M.; Reichardt, I.; Ullrich, R.
2016-12-01
Between 0 and -37°C, ice formation in clouds is triggered by aerosol particles acting as heterogeneous ice nuclei. At lower temperatures, heterogeneous ice nucleation on aerosols can occur at lower supersaturations than homogeneous freezing of solutes. In laboratory experiments, the ability of different aerosol species (e.g. desert dusts, soot, biological particles) has been studied in detail and quantified via various theoretical or empirical parameterization approaches. For experiments in the AIDA cloud chamber, we have quantified the ice nucleation efficiency via a temperature- and supersaturation dependent ice nucleation active site density. Here we present a new empirical parameterization scheme for immersion and deposition ice nucleation on desert dust and soot based on these experimental data. The application of this parameterization to the simulation of cirrus clouds, deep convective clouds and orographic clouds will be shown, including the extension of the scheme to the treatment of freezing of rain drops. The results are compared to other heterogeneous ice nucleation schemes. Furthermore, an aerosol-dependent parameterization of contact ice nucleation is presented.
Neutrino masses, scale-dependent growth, and redshift-space distortions
Energy Technology Data Exchange (ETDEWEB)
Hernández, Oscar F., E-mail: oscarh@physics.mcgill.ca [Marianopolis College, 4873 Westmount Ave., Westmount, QC H3Y 1X9 (Canada)
2017-06-01
Massive neutrinos leave a unique signature in the large scale clustering of matter. We investigate the wavenumber dependence of the growth factor arising from neutrino masses and use a Fisher analysis to determine the aspects of a galaxy survey needed to measure this scale dependence.
Axial and Radial Forces of Cross-Bridges Depend on Lattice Spacing
Williams, C. David; Regnier, Michael; Daniel, Thomas L.
2010-01-01
Nearly all mechanochemical models of the cross-bridge treat myosin as a simple linear spring arranged parallel to the contractile filaments. These single-spring models cannot account for the radial force that muscle generates (orthogonal to the long axis of the myofilaments) or the effects of changes in filament lattice spacing. We describe a more complex myosin cross-bridge model that uses multiple springs to replicate myosin's force-generating power stroke and account for the effects of lattice spacing and radial force. The four springs which comprise this model (the 4sXB) correspond to the mechanically relevant portions of myosin's structure. As occurs in vivo, the 4sXB's state-transition kinetics and force-production dynamics vary with lattice spacing. Additionally, we describe a simpler two-spring cross-bridge (2sXB) model which produces results similar to those of the 4sXB model. Unlike the 4sXB model, the 2sXB model requires no iterative techniques, making it more computationally efficient. The rate at which both multi-spring cross-bridges bind and generate force decreases as lattice spacing grows. The axial force generated by each cross-bridge as it undergoes a power stroke increases as lattice spacing grows. The radial force that a cross-bridge produces as it undergoes a power stroke varies from expansive to compressive as lattice spacing increases. Importantly, these results mirror those for intact, contracting muscle force production. PMID:21152002
International Nuclear Information System (INIS)
Comelli, D.; Riotto, A.
1995-06-01
Motivated by cosmological applications like electroweak baryogenesis, we develop a field theoretic approach to the computation of particle currents on a space-time dependent and CP-violating Higgs background. We consider the Standard Model model with two Higgs doublets and CP violation in the scalar sector, and compute both fermionic and Higgs currents by means of an expansion in the background fields. We discuss the gauge dependence of the results and the renormalization of the current operators, showing that in the limit of local equilibrium, no extra renormalization conditions are needed in order to specify the system completely. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Ho, C.-L. [Department of Physics, Tamkang University, Tamsui 25137, Taiwan (China); Lee, C.-C., E-mail: chieh.no27@gmail.com [Center of General Education, Aletheia University, Tamsui 25103, Taiwan (China)
2016-01-15
We consider solvability of the generalized reaction–diffusion equation with both space- and time-dependent diffusion and reaction terms by means of the similarity method. By introducing the similarity variable, the reaction–diffusion equation is reduced to an ordinary differential equation. Matching the resulting ordinary differential equation with known exactly solvable equations, one can obtain corresponding exactly solvable reaction–diffusion systems. Several representative examples of exactly solvable reaction–diffusion equations are presented.
A unified spectral parameterization for wave breaking: From the deep ocean to the surf zone
Filipot, J.-F.; Ardhuin, F.
2012-11-01
A new wave-breaking dissipation parameterization designed for phase-averaged spectral wave models is presented. It combines wave breaking basic physical quantities, namely, the breaking probability and the dissipation rate per unit area. The energy lost by waves is first explicitly calculated in physical space before being distributed over the relevant spectral components. The transition from deep to shallow water is made possible by using a dissipation rate per unit area of breaking waves that varies with the wave height, wavelength and water depth. This parameterization is implemented in the WAVEWATCH III modeling framework, which is applied to a wide range of conditions and scales, from the global ocean to the beach scale. Wave height, peak and mean periods, and spectral data are validated using in situ and remote sensing data. Model errors are comparable to those of other specialized deep or shallow water parameterizations. This work shows that it is possible to have a seamless parameterization from the deep ocean to the surf zone.
Statistical inference and visualization in scale-space for spatially dependent images
Vaughan, Amy; Jun, Mikyoung; Park, Cheolwoo
2012-01-01
SiZer (SIgnificant ZERo crossing of the derivatives) is a graphical scale-space visualization tool that allows for statistical inferences. In this paper we develop a spatial SiZer for finding significant features and conducting goodness-of-fit tests
Climate impacts of parameterized Nordic Sea overflows
Danabasoglu, Gokhan; Large, William G.; Briegleb, Bruce P.
2010-11-01
A new overflow parameterization (OFP) of density-driven flows through ocean ridges via narrow, unresolved channels has been developed and implemented in the ocean component of the Community Climate System Model version 4. It represents exchanges from the Nordic Seas and the Antarctic shelves, associated entrainment, and subsequent injection of overflow product waters into the abyssal basins. We investigate the effects of the parameterized Denmark Strait (DS) and Faroe Bank Channel (FBC) overflows on the ocean circulation, showing their impacts on the Atlantic Meridional Overturning Circulation and the North Atlantic climate. The OFP is based on the Marginal Sea Boundary Condition scheme of Price and Yang (1998), but there are significant differences that are described in detail. Two uncoupled (ocean-only) and two fully coupled simulations are analyzed. Each pair consists of one case with the OFP and a control case without this parameterization. In both uncoupled and coupled experiments, the parameterized DS and FBC source volume transports are within the range of observed estimates. The entrainment volume transports remain lower than observational estimates, leading to lower than observed product volume transports. Due to low entrainment, the product and source water properties are too similar. The DS and FBC overflow temperature and salinity properties are in better agreement with observations in the uncoupled case than in the coupled simulation, likely reflecting surface flux differences. The most significant impact of the OFP is the improved North Atlantic Deep Water penetration depth, leading to a much better comparison with the observational data and significantly reducing the chronic, shallow penetration depth bias in level coordinate models. This improvement is due to the deeper penetration of the southward flowing Deep Western Boundary Current. In comparison with control experiments without the OFP, the abyssal ventilation rates increase in the North
A parameterization of cloud droplet nucleation
International Nuclear Information System (INIS)
Ghan, S.J.; Chuang, C.; Penner, J.E.
1993-01-01
Droplet nucleation is a fundamental cloud process. The number of aerosols activated to form cloud droplets influences not only the number of aerosols scavenged by clouds but also the size of the cloud droplets. Cloud droplet size influences the cloud albedo and the conversion of cloud water to precipitation. Global aerosol models are presently being developed with the intention of coupling with global atmospheric circulation models to evaluate the influence of aerosols and aerosol-cloud interactions on climate. If these and other coupled models are to address issues of aerosol-cloud interactions, the droplet nucleation process must be adequately represented. Here we introduce a droplet nucleation parametrization that offers certain advantages over the popular Twomey (1959) parameterization
Cumulus parameterizations in chemical transport models
Mahowald, Natalie M.; Rasch, Philip J.; Prinn, Ronald G.
1995-12-01
Global three-dimensional chemical transport models (CTMs) are valuable tools for studying processes controlling the distribution of trace constituents in the atmosphere. A major uncertainty in these models is the subgrid-scale parametrization of transport by cumulus convection. This study seeks to define the range of behavior of moist convective schemes and point toward more reliable formulations for inclusion in chemical transport models. The emphasis is on deriving convective transport from meteorological data sets (such as those from the forecast centers) which do not routinely include convective mass fluxes. Seven moist convective parameterizations are compared in a column model to examine the sensitivity of the vertical profile of trace gases to the parameterization used in a global chemical transport model. The moist convective schemes examined are the Emanuel scheme [Emanuel, 1991], the Feichter-Crutzen scheme [Feichter and Crutzen, 1990], the inverse thermodynamic scheme (described in this paper), two versions of a scheme suggested by Hack [Hack, 1994], and two versions of a scheme suggested by Tiedtke (one following the formulation used in the ECMWF (European Centre for Medium-Range Weather Forecasting) and ECHAM3 (European Centre and Hamburg Max-Planck-Institut) models [Tiedtke, 1989], and one formulated as in the TM2 (Transport Model-2) model (M. Heimann, personal communication, 1992). These convective schemes vary in the closure used to derive the mass fluxes, as well as the cloud model formulation, giving a broad range of results. In addition, two boundary layer schemes are compared: a state-of-the-art nonlocal boundary layer scheme [Holtslag and Boville, 1993] and a simple adiabatic mixing scheme described in this paper. Three tests are used to compare the moist convective schemes against observations. Although the tests conducted here cannot conclusively show that one parameterization is better than the others, the tests are a good measure of the
Parameterization of MARVELS Spectra Using Deep Learning
Gilda, Sankalp; Ge, Jian; MARVELS
2018-01-01
Like many large-scale surveys, the Multi-Object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) was designed to operate at a moderate spectral resolution ($\\sim$12,000) for efficiency in observing large samples, which makes the stellar parameterization difficult due to the high degree of blending of spectral features. Two extant solutions to deal with this issue are to utilize spectral synthesis, and to utilize spectral indices [Ghezzi et al. 2014]. While the former is a powerful and tested technique, it can often yield strongly coupled atmospheric parameters, and often requires high spectral resolution (Valenti & Piskunov 1996). The latter, though a promising technique utilizing measurements of equivalent widths of spectral indices, has only been employed with respect to FKG dwarfs and sub-giants and not red-giant branch stars, which constitute ~30% of MARVELS targets. In this work, we tackle this problem using a convolution neural network (CNN). In particular, we train a one-dimensional CNN on appropriately processed PHOENIX synthetic spectra using supervised training to automatically distinguish the features relevant for the determination of each of the three atmospheric parameters – T_eff, log(g), [Fe/H] – and use the knowledge thus gained by the network to parameterize 849 MARVELS giants. When tested on the synthetic spectra themselves, our estimates of the parameters were consistent to within 11 K, .02 dex, and .02 dex (in terms of mean absolute errors), respectively. For MARVELS dwarfs, the accuracies are 80K, .16 dex and .10 dex, respectively.
Wang, Yuheng; Zhang, Yajie; Lu, Guanghao; Feng, Xiaoshan; Xiao, Tong; Xie, Jing; Liu, Xiaoyan; Ji, Jiahui; Wei, Zhixiang; Bu, Laju
2018-04-25
Photon absorption-induced exciton generation plays an important role in determining the photovoltaic properties of donor/acceptor organic solar cells with an inverted architecture. However, the reconstruction of light harvesting and thus exciton generation at different locations within organic inverted device are still not well resolved. Here, we investigate the film depth-dependent light absorption spectra in a small molecule donor/acceptor film. Including depth-dependent spectra into an optical transfer matrix method allows us to reconstruct both film depth- and energy-dependent exciton generation profiles, using which short-circuit current and external quantum efficiency of the inverted device are simulated and compared with the experimental measurements. The film depth-dependent spectroscopy, from which we are able to simultaneously reconstruct light harvesting profile, depth-dependent composition distribution, and vertical energy level variations, provides insights into photovoltaic process. In combination with appropriate material processing methods and device architecture, the method proposed in this work will help optimizing film depth-dependent optical/electronic properties for high-performance solar cells.
International Nuclear Information System (INIS)
Novoselov, G.M.; Litvinskij, L.L
2001-01-01
Different cross-section parameterization methods in the low-energy region are considered. It is shown that the potential scattering parameter value derived from analysis of experimental cross-section data is dependent essentially on the method used to take account of the nearest resonances. A formula describing this dependence is obtained. The results are verified by numerical model calculations. (author)
Scale-dependent Patterns in One-dimensional Fracture Spacing and Aperture Data
Roy, A.; Perfect, E.
2013-12-01
One-dimensional scanline data about fracture spacing and size attributes such as aperture or length are mostly considered in separate studies that compute the cumulative frequency of these attributes without regard to their actual spatial sequence. In a previous study, we showed that spacing data can be analyzed using lacunarity to identify whether fractures occur in clusters. However, to determine if such clusters also contain the largest fractures in terms of a size attribute such as aperture, it is imperative that data about the size attribute be integrated with information about fracture spacing. While for example, some researchers have considered aperture in conjunction with spacing, their analyses were either applicable only to a specific type of data (e.g. multifractal) or failed to characterize the data at different scales. Lacunarity is a technique for analyzing multi-scale non-binary data and is ideally-suited for characterizing scanline data with spacing and aperture values. We present a technique that can statistically delineate the relationship between size attributes and spatial clustering. We begin by building a model scanline that has complete partitioning of fractures with small and large apertures between the intercluster regions and clusters. We demonstrate that the ratio of lacunarity for this model to that of its counterpart for a completely randomized sequence of apertures can be used to determine whether large-aperture fractures preferentially occur next to each other. The technique is then applied to two natural fracture scanline datasets, one with most of the large apertures occurring in fracture clusters, and the other with more randomly-spaced fractures, without any specific ordering of aperture values. The lacunarity ratio clearly discriminates between these two datasets and, in the case of the first example, it is also able to identify the range of scales over which the widest fractures are clustered. The technique thus developed for
THERMOS, Space-Dependent Thermal Flux in 1-D Slab or Cylinder
International Nuclear Information System (INIS)
Honeck, Henry C.
2001-01-01
1 - Nature of physical problem solved: Computes the scalar thermal neutron spectrum as function of position in a one-dimensional slab (THERMOS-1) or cylindrical cell (THERMOS-2). Isotropic neutron scattering in the laboratory system is assumed. The slowing down source is computed from elastic scattering of the neutrons in a 1/E epithermal flux. Either a reflecting or vacuum boundary can be chosen. 2 - Method of solution: The velocity and space variables are replaced by discrete values. Scattering and collision probability matrices are computed and the neutron balance equation is solved by iterative techniques. A combination of a Gauss iteration, renormalization and extrapolation is used to accelerate convergence. 3 - Restrictions on the complexity of the problem: Maximum 30 velocity groups, 20 space points, 5 mixtures (assigned arbitrarily to the space points) composed of maximum 10 isotopes. An additional 10 isotopes can be specified for activation calculations and cross section averaging. The Library has received the 7090 version of this programme through the CETIS programmotheque. The 7040 version was written by the Universite libre de Bruxelles. ALGOL version was offered by Delft (Reactor Instituut Delft, Netherlands). A version for ICL computer was received from Central Research Institute for Physics of the Hungarian Academy of Sciences Budapest, Hungary
Pedestrian paths: why path-dependence theory leaves health policy analysis lost in space.
Brown, Lawrence D
2010-08-01
Path dependence, a model first advanced to explain puzzles in the diffusion of technology, has lately won allegiance among analysts of the politics of public policy, including health care policy. Though the central premise of the model--that past events and decisions shape options for innovation in the present and future--is indisputable (indeed path dependence is, so to speak, too shallow to be false), the approach, at least as applied to health policy, suffers from ambiguities that undercut its claims to illuminate policy projects such as managed care, on which this article focuses. Because path dependence adds little more than marginal value to familiar images of the politics of policy--incrementalism, for one--analysts might do well to put it on the back burner and pursue instead "thick descriptions" that help them to distinguish different degrees of openness to exogenous change among diverse policy arenas.
Generalized linear differential equations in a Banach space : continuous dependence on a parameter
Czech Academy of Sciences Publication Activity Database
Monteiro, G.A.; Tvrdý, Milan
2013-01-01
Roč. 33, č. 1 (2013), s. 283-303 ISSN 1078-0947 Institutional research plan: CEZ:AV0Z10190503 Keywords : generalized differential equations * continuous dependence * Kurzweil-Stieltjes integral Subject RIV: BA - General Mathematics Impact factor: 0.923, year: 2013 http://aimsciences.org/journals/displayArticlesnew.jsp?paperID=7615
Jha, Sanjeev Kumar
2015-07-21
A geostatistical framework is proposed to downscale daily precipitation and temperature. The methodology is based on multiple-point geostatistics (MPS), where a multivariate training image is used to represent the spatial relationship between daily precipitation and daily temperature over several years. Here, the training image consists of daily rainfall and temperature outputs from the Weather Research and Forecasting (WRF) model at 50 km and 10 km resolution for a twenty year period ranging from 1985 to 2004. The data are used to predict downscaled climate variables for the year 2005. The result, for each downscaled pixel, is daily time series of precipitation and temperature that are spatially dependent. Comparison of predicted precipitation and temperature against a reference dataset indicates that both the seasonal average climate response together with the temporal variability are well reproduced. The explicit inclusion of time dependence is explored by considering the climate properties of the previous day as an additional variable. Comparison of simulations with and without inclusion of time dependence shows that the temporal dependence only slightly improves the daily prediction because the temporal variability is already well represented in the conditioning data. Overall, the study shows that the multiple-point geostatistics approach is an efficient tool to be used for statistical downscaling to obtain local scale estimates of precipitation and temperature from General Circulation Models. This article is protected by copyright. All rights reserved.
Two-Dimensional Space-Time Dependent Multi-group Diffusion Equation with SLOR Method
International Nuclear Information System (INIS)
Yulianti, Y.; Su'ud, Z.; Waris, A.; Khotimah, S. N.
2010-01-01
The research of two-dimensional space-time diffusion equations with SLOR (Successive-Line Over Relaxation) has been done. SLOR method is chosen because this method is one of iterative methods that does not required to defined whole element matrix. The research is divided in two cases, homogeneous case and heterogeneous case. Homogeneous case has been inserted by step reactivity. Heterogeneous case has been inserted by step reactivity and ramp reactivity. In general, the results of simulations are agreement, even in some points there are differences.
Parameterizing Size Distribution in Ice Clouds
Energy Technology Data Exchange (ETDEWEB)
DeSlover, Daniel; Mitchell, David L.
2009-09-25
PARAMETERIZING SIZE DISTRIBUTIONS IN ICE CLOUDS David L. Mitchell and Daniel H. DeSlover ABSTRACT An outstanding problem that contributes considerable uncertainty to Global Climate Model (GCM) predictions of future climate is the characterization of ice particle sizes in cirrus clouds. Recent parameterizations of ice cloud effective diameter differ by a factor of three, which, for overcast conditions, often translate to changes in outgoing longwave radiation (OLR) of 55 W m-2 or more. Much of this uncertainty in cirrus particle sizes is related to the problem of ice particle shattering during in situ sampling of the ice particle size distribution (PSD). Ice particles often shatter into many smaller ice fragments upon collision with the rim of the probe inlet tube. These small ice artifacts are counted as real ice crystals, resulting in anomalously high concentrations of small ice crystals (D < 100 µm) and underestimates of the mean and effective size of the PSD. Half of the cirrus cloud optical depth calculated from these in situ measurements can be due to this shattering phenomenon. Another challenge is the determination of ice and liquid water amounts in mixed phase clouds. Mixed phase clouds in the Arctic contain mostly liquid water, and the presence of ice is important for determining their lifecycle. Colder high clouds between -20 and -36 oC may also be mixed phase but in this case their condensate is mostly ice with low levels of liquid water. Rather than affecting their lifecycle, the presence of liquid dramatically affects the cloud optical properties, which affects cloud-climate feedback processes in GCMs. This project has made advancements in solving both of these problems. Regarding the first problem, PSD in ice clouds are uncertain due to the inability to reliably measure the concentrations of the smallest crystals (D < 100 µm), known as the “small mode”. Rather than using in situ probe measurements aboard aircraft, we employed a treatment of ice
Building the nodal nuclear data dependences in a many-dimensional state-variable space
International Nuclear Information System (INIS)
Dufek, Jan
2011-01-01
Highlights: → The Abstract and Introduction are revised to reflect reviewers' comments. → Section is revised and simplified. → The third paragraph in Section is revised. → All typos are fixed. - Abstract: We present new methods for building the polynomial-regression based nodal nuclear data models. The data models can reflect dependences on a large number of state variables, and they can consider various history effects. Suitable multivariate polynomials that approximate the nodal data dependences are identified efficiently in an iterative manner. The history effects are analysed using a new sampling scheme for lattice calculations where the traditional base burnup and branch calculations are replaced by a large number of diverse burnup histories. The total number of lattice calculations is controlled so that the data models are built to a required accuracy.
Time-dependent transitions with time–space noncommutativity and its implications in quantum optics
International Nuclear Information System (INIS)
Chandra, Nitin
2012-01-01
We study the time-dependent transitions of a quantum-forced harmonic oscillator in noncommutative R 1,1 perturbatively to linear order in the noncommutativity θ. We show that the Poisson distribution gets modified, and that the vacuum state evolves into a ‘squeezed’ state rather than a coherent state. The time evolutions of uncertainties in position and momentum in vacuum are also studied and imply interesting consequences for modeling nonlinear phenomena in quantum optics. (paper)
Stoupel, Eliiyahu; Radishauskas, Richardas; Bernotiene, Gailute; Tamoshiunas, Abdonas; Virvichiute, Daiva
2018-02-05
Many biological processes are influenced by space weather activity components such as solar activity (SA), geomagnetic activity (GMA) and cosmic ray activity (CRA). Examples are total mortality, acute myocardial infarction (AMI), stroke (cerebrovascular accident), sudden cardiac death, some congenital maladies (congenital heart disease and Down syndrome), many events in neonatology, ophtalmology, blood pressure regulation, blood coagulation, inflammation, etc. The aim of this study was to check if the level of blood troponins (Tns) - markers of myocardial damage and recognized components of modern description of AMI - is connected with the mentioned space weather parameters. Patients admitted to a 3000-bed tertiary university hospital in Kaunas, Lithuania, with suspected AMI were the object of the study. Data for the time between 2008 and 2013 - 72 consecutive months - were studied. Of the patients, 1896 (1398 male, 498 female) had elevated troponin I (Tn I) or troponin T (Tn T, sensitive Tn) levels. Normal values were 0.00-0.03 ng/mL for Tn I and 0.00-14.00 ng/mL for Tn T. Monthly means and standard deviation of Tn I and Tn T were compared with monthly markers of SA, GMA and CRA. Pearson correlation coefficients and their probabilities were established (in addition to the consecutive graphs of both comparing physical and biological data). The cosmophysical data came from space service institutions in the United States, Russia and Finland. AMI was diagnosed in 1188 patients (62.66%), and intermediate coronary syndrome in 698 patients (36.81%). There were significant links of the Tn blood levels with four SA indices and CRA (neutron activity in imp/min); there was no significant correlation with GMA indices Ap and Cp (p=0.27 and p=0.235). Tn T levels significantly correlated with the GMA indices and not with the SA and CRA levels (Ap: r=0.77, p=0.0021; Cp: r=0.729, p=0.0047). First, the monthly level of blood Tn I in ACS is significantly correlated with the indices
''Free-space'' boundary conditions for the time-dependent wave equation
International Nuclear Information System (INIS)
Lindman, E.L.
1975-01-01
Boundary conditions for the discrete wave equation which act like an infinite region of free space in contact with the computational region can be constructed using projection operators. Propagating and evanescent waves coming from within the computational region generate no reflected waves as they cross the boundary. At the same time arbitrary waves may be launched into the computational region. Well known projection operators for one-dimensional waves may be used for this purpose in one dimension. Extensions of these operators to higher dimensions along with numerically efficient approximations to them are described for higher-dimensional problems. The separation of waves into ingoing and outgoing waves inherent in these boundary conditions greatly facilitates diagnostics
Temperature dependence of active photonic band gap in bragg-spaced quantum wells
International Nuclear Information System (INIS)
Hu Zhiqiang; Wang Tao; Yu Chunchao; Xu Wei
2011-01-01
A novel all-optical polarization switch of active photonic band gap structure based on non-resonant optical Stark effect bragg-spaced quantum wells was investigated and it could be compatible with the optical communication system. The theory is based on InGaAsP/InP Bragg-spaced quantum wells (BSQWs). Mainly through the design of the InGaAsP well layer component and InP barrier thickness to make the quantum-period cycle meet the bragg condition and the bragg frequency is equal to re-hole exciton resonance frequency. When a spectrally narrow control pulse is tuned within the forbidden gap, such BSQWs have been shown to exhibit large optical nonlinearities and ps recovery times, which can form T hz switch. However, the exciton binding energy of InGaAsP will be automatically separate at room temperature, so the effect of all-optical polarization switching of active photonic band gap bragg structure quantum wells can only be studied at low temperature. By a large number of experiments, we tested part of the material parameters of BSQWs in the temperature range 10-300K. On this basis, the InGaAsP and InP refractive index changes with wavelength, InP thermal expansion coefficient are studied and a relationship equation is established. Experimental results show that the bragg reflection spectra with temperature mainly is effected by InP refractive index changes with temperature. Our theoretical study and experiment are an instruction as a reference in the designs and experiments of future practical optical switches.
Temperature dependence of active photonic band gap in bragg-spaced quantum wells
Energy Technology Data Exchange (ETDEWEB)
Hu Zhiqiang; Wang Tao; Yu Chunchao; Xu Wei, E-mail: huzhiqianghzq@163.com [Wuhan National Laboratory for Optoelectronics, College of Optoelectronic Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, Hubei (China)
2011-02-01
A novel all-optical polarization switch of active photonic band gap structure based on non-resonant optical Stark effect bragg-spaced quantum wells was investigated and it could be compatible with the optical communication system. The theory is based on InGaAsP/InP Bragg-spaced quantum wells (BSQWs). Mainly through the design of the InGaAsP well layer component and InP barrier thickness to make the quantum-period cycle meet the bragg condition and the bragg frequency is equal to re-hole exciton resonance frequency. When a spectrally narrow control pulse is tuned within the forbidden gap, such BSQWs have been shown to exhibit large optical nonlinearities and ps recovery times, which can form T hz switch. However, the exciton binding energy of InGaAsP will be automatically separate at room temperature, so the effect of all-optical polarization switching of active photonic band gap bragg structure quantum wells can only be studied at low temperature. By a large number of experiments, we tested part of the material parameters of BSQWs in the temperature range 10-300K. On this basis, the InGaAsP and InP refractive index changes with wavelength, InP thermal expansion coefficient are studied and a relationship equation is established. Experimental results show that the bragg reflection spectra with temperature mainly is effected by InP refractive index changes with temperature. Our theoretical study and experiment are an instruction as a reference in the designs and experiments of future practical optical switches.
Reliability and parameterization of Romberg Test in people who have suffered a stroke
Perez Cruzado, David; Gonzalez Sanchez, Manuel; Cuesta-Vargas, Antonio
2014-01-01
AIM: To analyze the reliability and describe the parameterization with inertial sensors, of Romberg test in people who have had a stroke. METHODS: Romberg's Test was performed during 20 seconds in four different setting, depending from supporting leg and position of the eyes (opened eyes / dominant leg; closed eyes / dominant leg; opened eyes / non-dominant leg; closed eyes / non-dominant leg) in people who have suffered a stroke over a year ago. Two inertial sensors (sampli...
Robust H∞ Control for Singular Time-Delay Systems via Parameterized Lyapunov Functional Approach
Directory of Open Access Journals (Sweden)
Li-li Liu
2014-01-01
Full Text Available A new version of delay-dependent bounded real lemma for singular systems with state delay is established by parameterized Lyapunov-Krasovskii functional approach. In order to avoid generating nonconvex problem formulations in control design, a strategy that introduces slack matrices and decouples the system matrices from the Lyapunov-Krasovskii parameter matrices is used. Examples are provided to demonstrate that the results in this paper are less conservative than the existing corresponding ones in the literature.
Parameterized combinatorial geometry modeling in Moritz
International Nuclear Information System (INIS)
Van Riper, K.A.
2005-01-01
We describe the use of named variables as surface and solid body coefficients in the Moritz geometry editing program. Variables can also be used as material numbers, cell densities, and transformation values. A variable is defined as a constant or an arithmetic combination of constants and other variables. A variable reference, such as in a surface coefficient, can be a single variable or an expression containing variables and constants. Moritz can read and write geometry models in MCNP and ITS ACCEPT format; support for other codes will be added. The geometry can be saved with either the variables in place, for modifying the models in Moritz, or with the variables evaluated for use in the transport codes. A program window shows a list of variables and provides fields for editing them. Surface coefficients and other values that use a variable reference are shown in a distinctive style on object property dialogs; associated buttons show fields for editing the reference. We discuss our use of variables in defining geometry models for shielding studies in PET clinics. When a model is parameterized through the use of variables, changes such as room dimensions, shielding layer widths, and cell compositions can be quickly achieved by changing a few numbers without requiring knowledge of the input syntax for the transport code or the tedious and error prone work of recalculating many surface or solid body coefficients. (author)
Phenomenology of convection-parameterization closure
Directory of Open Access Journals (Sweden)
J.-I. Yano
2013-04-01
Full Text Available Closure is a problem of defining the convective intensity in a given parameterization. In spite of many years of efforts and progress, it is still considered an overall unresolved problem. The present article reviews this problem from phenomenological perspectives. The physical variables that may contribute in defining the convective intensity are listed, and their statistical significances identified by observational data analyses are reviewed. A possibility is discussed for identifying a correct closure hypothesis by performing a linear stability analysis of tropical convectively coupled waves with various different closure hypotheses. Various individual theoretical issues are considered from various different perspectives. The review also emphasizes that the dominant physical factors controlling convection differ between the tropics and extra-tropics, as well as between oceanic and land areas. Both observational as well as theoretical analyses, often focused on the tropics, do not necessarily lead to conclusions consistent with our operational experiences focused on midlatitudes. Though we emphasize the importance of the interplays between these observational, theoretical and operational perspectives, we also face challenges for establishing a solid research framework that is universally applicable. An energy cycle framework is suggested as such a candidate.
Stellar Atmospheric Parameterization Based on Deep Learning
Pan, Ru-yang; Li, Xiang-ru
2017-07-01
Deep learning is a typical learning method widely studied in the fields of machine learning, pattern recognition, and artificial intelligence. This work investigates the problem of stellar atmospheric parameterization by constructing a deep neural network with five layers, and the node number in each layer of the network is respectively 3821-500-100-50-1. The proposed scheme is verified on both the real spectra measured by the Sloan Digital Sky Survey (SDSS) and the theoretic spectra computed with the Kurucz's New Opacity Distribution Function (NEWODF) model, to make an automatic estimation for three physical parameters: the effective temperature (Teff), surface gravitational acceleration (lg g), and metallic abundance (Fe/H). The results show that the stacked autoencoder deep neural network has a better accuracy for the estimation. On the SDSS spectra, the mean absolute errors (MAEs) are 79.95 for Teff/K, 0.0058 for (lg Teff/K), 0.1706 for lg (g/(cm·s-2)), and 0.1294 dex for the [Fe/H], respectively; On the theoretic spectra, the MAEs are 15.34 for Teff/K, 0.0011 for lg (Teff/K), 0.0214 for lg(g/(cm · s-2)), and 0.0121 dex for [Fe/H], respectively.
1988-10-01
meteorologists’ rule-of-thumb that climatic drift manifests itself in periods greater than 30 years. For a fractionally-differenced model with our...estimates in a univariate ARIMA (p, d, q) with I d I< 0.5 has been derived by Li and McLrjd (1986). The model used by I-Iaslett an Raftery can be viewed as...Reply to the Discussion of "Space-time Modelling with Long-mnmory cDependence: Assessing Ireland’s Wind Resource" cJohn Haslett Department of
Hosseini, Kamyar; Mayeli, Peyman; Bekir, Ahmet; Guner, Ozkan
2018-01-01
In this article, a special type of fractional differential equations (FDEs) named the density-dependent conformable fractional diffusion-reaction (DDCFDR) equation is studied. Aforementioned equation has a significant role in the modelling of some phenomena arising in the applied science. The well-organized methods, including the \\exp (-φ (\\varepsilon )) -expansion and modified Kudryashov methods are exerted to generate the exact solutions of this equation such that some of the solutions are new and have been reported for the first time. Results illustrate that both methods have a great performance in handling the DDCFDR equation.
International Nuclear Information System (INIS)
Moeller, E.
1965-12-01
The use of the time dependent reaction rate method for the measurement of neutron slowing-down time distributions in hydrogen has been analyzed and applied to the case of sloping down in water. Neutrons with energies of about 1 MeV were slowed down, and the time-dependent neutron density at 1.46 eV and its space dependence was measured with a time resolution of 0.042 μs. The results confirm the well known theory for time-dependent slowing down in hydrogen. The space dependence of the distributions is well described by the P 1 -calculations by Claesson
Energy Technology Data Exchange (ETDEWEB)
Moeller, E
1965-12-15
The use of the time dependent reaction rate method for the measurement of neutron slowing-down time distributions in hydrogen has been analyzed and applied to the case of sloping down in water. Neutrons with energies of about 1 MeV were slowed down, and the time-dependent neutron density at 1.46 eV and its space dependence was measured with a time resolution of 0.042 {mu}s. The results confirm the well known theory for time-dependent slowing down in hydrogen. The space dependence of the distributions is well described by the P{sub 1}-calculations by Claesson.
On quaternion based parameterization of orientation in computer vision and robotics
Directory of Open Access Journals (Sweden)
G. Terzakis
2014-04-01
Full Text Available The problem of orientation parameterization for applications in computer vision and robotics is examined in detail herein. The necessary intuition and formulas are provided for direct practical use in any existing algorithm that seeks to minimize a cost function in an iterative fashion. Two distinct schemes of parameterization are analyzed: The first scheme concerns the traditional axis-angle approach, while the second employs stereographic projection from unit quaternion sphere to the 3D real projective space. Performance measurements are taken and a comparison is made between the two approaches. Results suggests that there exist several benefits in the use of stereographic projection that include rational expressions in the rotation matrix derivatives, improved accuracy, robustness to random starting points and accelerated convergence.
Current densities in a space-time-dependent and CP-violating Higgs background in the adiabatic limit
International Nuclear Information System (INIS)
Comelli, D.; Pietroni, M.; Riotto, A.
1996-01-01
Motivated by cosmological applications such as electroweak baryogenesis, we develop a field theoretic approach to the computation of particle currents on a space-time-dependent and CP-violating Higgs background in the adiabatic limit. We consider the standard model with two Higgs doublets and CP violation in the scalar sector, and compute both fermionic and Higgs currents by means of an expansion in the background fields describing the profile of the bubble wall. We discuss the gauge dependence of the results and the renormalization of the current operators, showing that in the limit of local equilibrium, no extra renormalization conditions are needed in order to specify the system completely. copyright 1996 The American Physical Society
PRO-Elicere: A Study for Create a New Process of Dependability Analysis of Space Computer Systems
da Silva, Glauco; Netto Lahoz, Carlos Henrique
2013-09-01
This paper presents the new approach to the computer system dependability analysis, called PRO-ELICERE, which introduces data mining concepts and intelligent mechanisms to decision support to analyze the potential hazards and failures of a critical computer system. Also, are presented some techniques and tools that support the traditional dependability analysis and briefly discusses the concept of knowledge discovery and intelligent databases for critical computer systems. After that, introduces the PRO-ELICERE process, an intelligent approach to automate the ELICERE, a process created to extract non-functional requirements for critical computer systems. The PRO-ELICERE can be used in the V&V activities in the projects of Institute of Aeronautics and Space, such as the Brazilian Satellite Launcher (VLS-1).
Marchenko, I. G.; Marchenko, I. I.; Zhiglo, A. V.
2018-01-01
We present a study of the diffusion enhancement of underdamped Brownian particles in a one-dimensional symmetric space-periodic potential due to external symmetric time-periodic driving with zero mean. We show that the diffusivity can be enhanced by many orders of magnitude at an appropriate choice of the driving amplitude and frequency. The diffusivity demonstrates abnormal (decreasing) temperature dependence at the driving amplitudes exceeding a certain value. At any fixed driving frequency Ω normal temperature dependence of the diffusivity is restored at low enough temperatures, T oscillation frequency at the potential minimum, the diffusivity is shown to decrease with Ω according to a power law, with the exponent related to the transient superdiffusion exponent. This behavior is found similar for the cases of sinusoidal in time and piecewise constant periodic ("square") driving.
Carbody structural lightweighting based on implicit parameterized model
Chen, Xin; Ma, Fangwu; Wang, Dengfeng; Xie, Chen
2014-05-01
Most of recent research on carbody lightweighting has focused on substitute material and new processing technologies rather than structures. However, new materials and processing techniques inevitably lead to higher costs. Also, material substitution and processing lightweighting have to be realized through body structural profiles and locations. In the huge conventional workload of lightweight optimization, model modifications involve heavy manual work, and it always leads to a large number of iteration calculations. As a new technique in carbody lightweighting, the implicit parameterization is used to optimize the carbody structure to improve the materials utilization rate in this paper. The implicit parameterized structural modeling enables the use of automatic modification and rapid multidisciplinary design optimization (MDO) in carbody structure, which is impossible in the traditional structure finite element method (FEM) without parameterization. The structural SFE parameterized model is built in accordance with the car structural FE model in concept development stage, and it is validated by some structural performance data. The validated SFE structural parameterized model can be used to generate rapidly and automatically FE model and evaluate different design variables group in the integrated MDO loop. The lightweighting result of body-in-white (BIW) after the optimization rounds reveals that the implicit parameterized model makes automatic MDO feasible and can significantly improve the computational efficiency of carbody structural lightweighting. This paper proposes the integrated method of implicit parameterized model and MDO, which has the obvious practical advantage and industrial significance in the carbody structural lightweighting design.
Parameterization-based tracking for the P2 experiment
Sorokin, Iurii
2017-08-01
The P2 experiment in Mainz aims to determine the weak mixing angle θW at low momentum transfer by measuring the parity-violating asymmetry of elastic electronproton scattering. In order to achieve the intended precision of Δ(sin2 θW)/sin2θW = 0:13% within the planned 10 000 hours of running the experiment has to operate at the rate of 1011 detected electrons per second. Although it is not required to measure the kinematic parameters of each individual electron, every attempt is made to achieve the highest possible throughput in the track reconstruction chain. In the present work a parameterization-based track reconstruction method is described. It is a variation of track following, where the results of the computation-heavy steps, namely the propagation of a track to the further detector plane, and the fitting, are pre-calculated, and expressed in terms of parametric analytic functions. This makes the algorithm extremely fast, and well-suited for an implementation on an FPGA. The method also takes implicitly into account the actual phase space distribution of the tracks already at the stage of candidate construction. Compared to a simple algorithm, that does not use such information, this allows reducing the combinatorial background by many orders of magnitude, down to O(1) background candidate per one signal track. The method is developed specifically for the P2 experiment in Mainz, and the presented implementation is tightly coupled to the experimental conditions.
DEFF Research Database (Denmark)
Miyagi, Haruhide; Madsen, Lars Bojer
We have developed a new theoretical framework for time-dependent many-electron problems named time-dependent restricted-active-space self-consistent field (TD-RASSCF) theory. The theory generalizes the multicongurational time-dependent Hartree-Fock (MCTDHF) theory by truncating the expansion...
Scale dependence of halo and galaxy bias: Effects in real space
International Nuclear Information System (INIS)
Smith, Robert E.; Scoccimarro, Roman; Sheth, Ravi K.
2007-01-01
We examine the scale dependence of dark matter halo and galaxy clustering on very large scales (0.01 -1 ] -1 ] -1 ], and only show amplification on smaller scales, whereas low mass haloes show strong, ∼5%-10%, suppression over the range 0.05 -1 ]<0.15. These results were primarily established through the use of the cross-power spectrum of dark matter and haloes, which circumvents the thorny issue of shot-noise correction. The halo-halo power spectrum, however, is highly sensitive to the shot-noise correction; we show that halo exclusion effects make this sub-Poissonian and a new correction is presented. Our results have special relevance for studies of the baryon acoustic oscillation features in the halo power spectra. Nonlinear mode-mode coupling: (i) damps these features on progressively larger scales as halo mass increases; (ii) produces small shifts in the positions of the peaks and troughs which depend on halo mass. We show that these effects on halo clustering are important over the redshift range relevant to such studies (0< z<2), and so will need to be accounted for when extracting information from precision measurements of galaxy clustering. Our analytic model is described in the language of the ''halo model.'' The halo-halo clustering term is propagated into the nonlinear regime using ''1-loop'' perturbation theory and a nonlinear halo bias model. Galaxies are then inserted into haloes through the halo occupation distribution. We show that, with nonlinear bias parameters derived from simulations, this model produces predictions that are qualitatively in agreement with our numerical results. We then use it to show that the power spectra of red and blue galaxies depend differently on scale, thus underscoring the fact that proper modeling of nonlinear bias parameters will be crucial to derive reliable cosmological constraints. In addition to showing that the bias on very large scales is not simply linear, the model also shows that the halo-halo and halo
International Nuclear Information System (INIS)
Hathaway, D.H.; Somerville, R.C.J.; National Solar Observatory, Sunspot, NM; California Univ., La Jolla)
1985-01-01
Three-dimensional, time-dependent convection in a plane layer of fluid, uniformly heated from below and subject to vertical shear and to rotation about an axis tilted from the vertical, was simulated by the numerical solution of the Boussinesq equations, including all Coriolis terms. Rotation about a vertical axis produces smaller convection cells with diminished heat fluxes and considerable vorticity. When the rotation axis is tilted from the vertical to represent tropical latitudes, the convection cells become elongated in a N-S direction. Imposed flows with constant vertical shear produce convective rolls aligned with the mean flow. When the rotation vector is tilted from the vertical, the competing effects due to rotation and shear can stabilize the convective motions. 15 references
DEFF Research Database (Denmark)
Gasiunas, Vaidas; Mezini, Mira; Ostermann, Klaus
2007-01-01
of dependent classes and a machine-checked type soundness proof in Isabelle/HOL [29], the first of this kind for a language with virtual classes and path-dependent types. [29] T.Nipkow, L.C. Poulson, and M. Wenzel. Isabelle/HOL -- A Proof Assistant for Higher-Order Logic, volume 2283 of LNCS, Springer, 2002......Virtual classes allow nested classes to be refined in subclasses. In this way nested classes can be seen as dependent abstractions of the objects of the enclosing classes. Expressing dependency via nesting, however, has two limitations: Abstractions that depend on more than one object cannot...... be modeled and a class must know all classes that depend on its objects. This paper presents dependent classes, a generalization of virtual classes that expresses similar semantics by parameterization rather than by nesting. This increases expressivity of class variations as well as the flexibility...
Space-time dependence between energy sources and climate related energy production
Engeland, Kolbjorn; Borga, Marco; Creutin, Jean-Dominique; Ramos, Maria-Helena; Tøfte, Lena; Warland, Geir
2014-05-01
The European Renewable Energy Directive adopted in 2009 focuses on achieving a 20% share of renewable energy in the EU overall energy mix by 2020. A major part of renewable energy production is related to climate, called "climate related energy" (CRE) production. CRE production systems (wind, solar, and hydropower) are characterized by a large degree of intermittency and variability on both short and long time scales due to the natural variability of climate variables. The main strategies to handle the variability of CRE production include energy-storage, -transport, -diversity and -information (smart grids). The three first strategies aim to smooth out the intermittency and variability of CRE production in time and space whereas the last strategy aims to provide a more optimal interaction between energy production and demand, i.e. to smooth out the residual load (the difference between demand and production). In order to increase the CRE share in the electricity system, it is essential to understand the space-time co-variability between the weather variables and CRE production under both current and future climates. This study presents a review of the literature that searches to tackle these problems. It reveals that the majority of studies deals with either a single CRE source or with the combination of two CREs, mostly wind and solar. This may be due to the fact that the most advanced countries in terms of wind equipment have also very little hydropower potential (Denmark, Ireland or UK, for instance). Hydropower is characterized by both a large storage capacity and flexibility in electricity production, and has therefore a large potential for both balancing and storing energy from wind- and solar-power. Several studies look at how to better connect regions with large share of hydropower (e.g., Scandinavia and the Alps) to regions with high shares of wind- and solar-power (e.g., green battery North-Sea net). Considering time scales, various studies consider wind
The Dependence of Water Permeability in Quartz Sand on Gas Hydrate Saturation in the Pore Space
Kossel, E.; Deusner, C.; Bigalke, N.; Haeckel, M.
2018-02-01
Transport of fluids in gas hydrate bearing sediments is largely defined by the reduction of the permeability due to gas hydrate crystals in the pore space. Although the exact knowledge of the permeability behavior as a function of gas hydrate saturation is of crucial importance, state-of-the-art simulation codes for gas production scenarios use theoretically derived permeability equations that are hardly backed by experimental data. The reason for the insufficient validation of the model equations is the difficulty to create gas hydrate bearing sediments that have undergone formation mechanisms equivalent to the natural process and that have well-defined gas hydrate saturations. We formed methane hydrates in quartz sand from a methane-saturated aqueous solution and used magnetic resonance imaging to obtain time-resolved, three-dimensional maps of the gas hydrate saturation distribution. These maps were fed into 3-D finite element method simulations of the water flow. In our simulations, we tested the five most well-known permeability equations. All of the suitable permeability equations include the term (1-SH)n, where SH is the gas hydrate saturation and n is a parameter that needs to be constrained. The most basic equation describing the permeability behavior of water flow through gas hydrate bearing sand is k = k0 (1-SH)n. In our experiments, n was determined to be 11.4 (±0.3). Results from this study can be directly applied to bulk flow analysis under the assumption of homogeneous gas hydrate saturation and can be further used to derive effective permeability models for heterogeneous gas hydrate distributions at different scales.
Carrete, Jesús; Vermeersch, Bjorn; Katre, Ankita; van Roekeghem, Ambroise; Wang, Tao; Madsen, Georg K. H.; Mingo, Natalio
2017-11-01
almaBTE is a software package that solves the space- and time-dependent Boltzmann transport equation for phonons, using only ab-initio calculated quantities as inputs. The program can predictively tackle phonon transport in bulk crystals and alloys, thin films, superlattices, and multiscale structures with size features in the nm- μm range. Among many other quantities, the program can output thermal conductances and effective thermal conductivities, space-resolved average temperature profiles, and heat-current distributions resolved in frequency and space. Its first-principles character makes almaBTE especially well suited to investigate novel materials and structures. This article gives an overview of the program structure and presents illustrative examples for some of its uses. PROGRAM SUMMARY Program Title:almaBTE Program Files doi:http://dx.doi.org/10.17632/8tfzwgtp73.1 Licensing provisions: Apache License, version 2.0 Programming language: C++ External routines/libraries: BOOST, MPI, Eigen, HDF5, spglib Nature of problem: Calculation of temperature profiles, thermal flux distributions and effective thermal conductivities in structured systems where heat is carried by phonons Solution method: Solution of linearized phonon Boltzmann transport equation, Variance-reduced Monte Carlo
Automatic Generation of Symbolic Model for Parameterized Synchronous Systems
Institute of Scientific and Technical Information of China (English)
Wei-Wen Xu
2004-01-01
With the purpose of making the verification of parameterized system more general and easier, in this paper, a new and intuitive language PSL (Parameterized-system Specification Language) is proposed to specify a class of parameterized synchronous systems. From a PSL script, an automatic method is proposed to generate a constraint-based symbolic model. The model can concisely symbolically represent the collections of global states by counting the number of processes in a given state. Moreover, a theorem has been proved that there is a simulation relation between the original system and its symbolic model. Since the abstract and symbolic techniques are exploited in the symbolic model, state-explosion problem in traditional verification methods is efficiently avoided. Based on the proposed symbolic model, a reachability analysis procedure is implemented using ANSI C++ on UNIX platform. Thus, a complete tool for verifying the parameterized synchronous systems is obtained and tested for some cases. The experimental results show that the method is satisfactory.
de Lavenne, Alban; Andréassian, Vazken
2018-03-01
This paper examines the hydrological impact of the seasonality of precipitation and maximum evaporation: seasonality is, after aridity, a second-order determinant of catchment water yield. Based on a data set of 171 French catchments (where aridity ranged between 0.2 and 1.2), we present a parameterization of three commonly-used water balance formulas (namely, Turc-Mezentsev, Tixeront-Fu and Oldekop formulas) to account for seasonality effects. We quantify the improvement of seasonality-based parameterization in terms of the reconstitution of both catchment streamflow and water yield. The significant improvement obtained (reduction of RMSE between 9 and 14% depending on the formula) demonstrates the importance of climate seasonality in the determination of long-term catchment water balance.
Elastic orthorhombic anisotropic parameter inversion: An analysis of parameterization
Oh, Juwon; Alkhalifah, Tariq Ali
2016-01-01
The resolution of a multiparameter full-waveform inversion (FWI) is highly influenced by the parameterization used in the inversion algorithm, as well as the data quality and the sensitivity of the data to the elastic parameters because the scattering patterns of the partial derivative wavefields (PDWs) vary with parameterization. For this reason, it is important to identify an optimal parameterization for elastic orthorhombic FWI by analyzing the radiation patterns of the PDWs for many reasonable model parameterizations. We have promoted a parameterization that allows for the separation of the anisotropic properties in the radiation patterns. The central parameter of this parameterization is the horizontal P-wave velocity, with an isotropic scattering potential, influencing the data at all scales and directions. This parameterization decouples the influence of the scattering potential given by the P-wave velocity perturbation fromthe polar changes described by two dimensionless parameter perturbations and from the azimuthal variation given by three additional dimensionless parameters perturbations. In addition, the scattering potentials of the P-wave velocity perturbation are also decoupled from the elastic influences given by one S-wave velocity and two additional dimensionless parameter perturbations. The vertical S-wave velocity is chosen with the best resolution obtained from S-wave reflections and converted waves, little influence on P-waves in conventional surface seismic acquisition. The influence of the density on observed data can be absorbed by one anisotropic parameter that has a similar radiation pattern. The additional seven dimensionless parameters describe the polar and azimuth variations in the P- and S-waves that we may acquire, with some of the parameters having distinct influences on the recorded data on the earth's surface. These characteristics of the new parameterization offer the potential for a multistage inversion from high symmetry
Elastic orthorhombic anisotropic parameter inversion: An analysis of parameterization
Oh, Juwon
2016-09-15
The resolution of a multiparameter full-waveform inversion (FWI) is highly influenced by the parameterization used in the inversion algorithm, as well as the data quality and the sensitivity of the data to the elastic parameters because the scattering patterns of the partial derivative wavefields (PDWs) vary with parameterization. For this reason, it is important to identify an optimal parameterization for elastic orthorhombic FWI by analyzing the radiation patterns of the PDWs for many reasonable model parameterizations. We have promoted a parameterization that allows for the separation of the anisotropic properties in the radiation patterns. The central parameter of this parameterization is the horizontal P-wave velocity, with an isotropic scattering potential, influencing the data at all scales and directions. This parameterization decouples the influence of the scattering potential given by the P-wave velocity perturbation fromthe polar changes described by two dimensionless parameter perturbations and from the azimuthal variation given by three additional dimensionless parameters perturbations. In addition, the scattering potentials of the P-wave velocity perturbation are also decoupled from the elastic influences given by one S-wave velocity and two additional dimensionless parameter perturbations. The vertical S-wave velocity is chosen with the best resolution obtained from S-wave reflections and converted waves, little influence on P-waves in conventional surface seismic acquisition. The influence of the density on observed data can be absorbed by one anisotropic parameter that has a similar radiation pattern. The additional seven dimensionless parameters describe the polar and azimuth variations in the P- and S-waves that we may acquire, with some of the parameters having distinct influences on the recorded data on the earth\\'s surface. These characteristics of the new parameterization offer the potential for a multistage inversion from high symmetry
Directory of Open Access Journals (Sweden)
Chan Jun Chun
2016-02-01
Full Text Available In this paper, we propose a new frequency-dependent amplitude panning method for stereophonic image enhancement applied to a sound source recorded using two closely spaced omni-directional microphones. The ability to detect the direction of such a sound source is limited due to weak spatial information, such as the inter-channel time difference (ICTD and inter-channel level difference (ICLD. Moreover, when sound sources are recorded in a convolutive or a real room environment, the detection of sources is affected by reverberation effects. Thus, the proposed method first tries to estimate the source direction depending on the frequency using azimuth-frequency analysis. Then, a frequency-dependent amplitude panning technique is proposed to enhance the stereophonic image by modifying the stereophonic law of sines. To demonstrate the effectiveness of the proposed method, we compare its performance with that of a conventional method based on the beamforming technique in terms of directivity pattern, perceived direction, and quality degradation under three different recording conditions (anechoic, convolutive, and real reverberant. The comparison shows that the proposed method gives us better stereophonic images in a stereo loudspeaker reproduction than the conventional method without any annoying effects.
Contribution to the stochastically studies of space-time dependable hydrological processes
International Nuclear Information System (INIS)
Kjaevski, Ivancho
2002-12-01
One of the fundaments of today's planning and water economy is Science of Hydrology. Science of Hydrology through the history had followed the development of the water management systems. Water management systems, during the time from single-approach evolved to complex and multi purpose systems. The dynamic and development of the today's society contributed for increasing the demand of clean water, and in the same time, the resources of clean water in the nature are reduced. In this kind of conditions, water management systems should resolve problems that are more complicated during managing of water sources. Solving the problems in water management, enable development and applying new methods and technologies in planning and management with water resources and water management systems like: systematical analyses, operational research, hierarchy decisions, expert systems, computer technology etc. Planning and management of water sources needs historical measured data for hydro metrological processes. In our country there are data of hydro metrological processes in period of 50-70, but in some Europe countries there are data more than 100 years. Water economy trends follow the hydro metrological trend research. The basic statistic techniques like sampling, probability distribution function, correlation and regression, are used about one intended and simple water management problems. Solving new problems about water management needs using of space-time stochastic technique, modem mathematical and statistical techniques during simulation and optimization of complex water systems. We need tree phases of development of the techniques to get secure hydrological models: i) Estimate the quality of hydro meteorological data, analyzing of their consistency, and homogeneous; ii) Structural analyze of hydro meteorological processes; iii) Mathematical models for modeling hydro meteorological processes. Very often, the third phase is applied for analyzing and modeling of hydro
Spectral cumulus parameterization based on cloud-resolving model
Baba, Yuya
2018-02-01
We have developed a spectral cumulus parameterization using a cloud-resolving model. This includes a new parameterization of the entrainment rate which was derived from analysis of the cloud properties obtained from the cloud-resolving model simulation and was valid for both shallow and deep convection. The new scheme was examined in a single-column model experiment and compared with the existing parameterization of Gregory (2001, Q J R Meteorol Soc 127:53-72) (GR scheme). The results showed that the GR scheme simulated more shallow and diluted convection than the new scheme. To further validate the physical performance of the parameterizations, Atmospheric Model Intercomparison Project (AMIP) experiments were performed, and the results were compared with reanalysis data. The new scheme performed better than the GR scheme in terms of mean state and variability of atmospheric circulation, i.e., the new scheme improved positive bias of precipitation in western Pacific region, and improved positive bias of outgoing shortwave radiation over the ocean. The new scheme also simulated better features of convectively coupled equatorial waves and Madden-Julian oscillation. These improvements were found to be derived from the modification of parameterization for the entrainment rate, i.e., the proposed parameterization suppressed excessive increase of entrainment, thus suppressing excessive increase of low-level clouds.
International Nuclear Information System (INIS)
Hebenstreit, F.; Alkofer, R.; Gies, H.
2010-01-01
The nonperturbative electron-positron pair production (Schwinger effect) is considered for space- and time-dependent electric fields E-vector(x-vector,t). Based on the Dirac-Heisenberg-Wigner formalism, we derive a system of partial differential equations of infinite order for the 16 irreducible components of the Wigner function. In the limit of spatially homogeneous fields the Vlasov equation of quantum kinetic theory is rediscovered. It is shown that the quantum kinetic formalism can be exactly solved in the case of a constant electric field E(t)=E 0 and the Sauter-type electric field E(t)=E 0 sech 2 (t/τ). These analytic solutions translate into corresponding expressions within the Dirac-Heisenberg-Wigner formalism and allow to discuss the effect of higher derivatives. We observe that spatial field variations typically exert a strong influence on the components of the Wigner function for large momenta or for late times.
International Nuclear Information System (INIS)
Pain, Christopher C.; Eaton, Matthew D.; Gomes, Jefferson L.M.A.; Oliveira, Cassiano R.E. de; Umpleby, Adrian P.; Ziver, Kemal; Ackroyd, Ron T.; Miles, Bryan; Goddard, Antony J.H.; Dam, H. van; Hagen, T.H.J.J. van der; Lathouwers, D.
2003-01-01
Previous work into the space-dependent kinetics of the conceptual nuclear fluidized bed has highlighted the sensitivity of fission power to particle movements within the bed. The work presented in this paper investigates a method of stabilizing the fission power by making it less sensitive to fuel particle movement. Steady-state neutronic calculations are performed to obtain a suitable design that is stable to radial and axial fuel particle movements in the bed. Detailed spatial/temporal simulations performed using the finite element transient criticality (FETCH) code investigate the dynamics of the new reactor design. A dual requirement of the design is that it has a moderate power output of ∼300 MW(thermal)
On parameterized deformations and unsupervised learning
DEFF Research Database (Denmark)
Hansen, Michael Sass
matrix. Spline approximations of functions and in particular image registration warp fields are discussed. It is shown how spline bases may be learned from the optimization process, i.e. image registration optimization, and how this may contribute with a reasonable prior, or regularization in the method...... on an unrestricted linear parameter space, where all derivatives are defined, is introduced. Furthermore, it is shown that L2-norm the parameter space introduces a reasonable metric in the actual space of modelled diffeomorphisms. A new parametrization of 3D deformation fields, using potentials and Helmholtz...... of the multivariate B-splines, the warp field is automatically refined in areas where it results in the minimization of the registration cost function....
Gholibeigian, Hassan; Amirshahkarami, Abdolazim; Gholibeigian, Kazem
2017-01-01
In special relativity theory, time dilates in velocity of near light speed. Also based on ``Substantial motion'' theory of Sadra, relative time (time flux); R = f (mv , σ , τ) , for each atom is momentum of its involved fundamental particles, which is different from the other atoms. In this way, for modification of the relativistic classical equation of string theory and getting more precise results, we should use effect of dilation and contraction of time in equation. So we propose to add two derivatives of the time's flux to the equation as follows: n.tp∂/R ∂ τ +∂2Xμ/(σ , τ) ∂τ2 = n .tp (∂/R ∂ σ ) +c2∂2Xμ/(σ , τ) ∂σ2 In which, Xμ is space-time coordinates of the string, σ & τ are coordinates on the string world sheet, respectively space and time along the string, string's mass m , velocity of string's motion v , factor n depends on geometry of each hidden extra dimension which relates to its own flux time, and tp is Planck's time. AmirKabir University of Technology, Tehran, Iran.
International Nuclear Information System (INIS)
Li, Gongsheng; Zhang, Dali; Jia, Xianzheng; Yamamoto, Masahiro
2013-01-01
This paper deals with an inverse problem of simultaneously identifying the space-dependent diffusion coefficient and the fractional order in the 1D time-fractional diffusion equation with smooth initial functions by using boundary measurements. The uniqueness results for the inverse problem are proved on the basis of the inverse eigenvalue problem, and the Lipschitz continuity of the solution operator is established. A modified optimal perturbation algorithm with a regularization parameter chosen by a sigmoid-type function is put forward for the discretization of the minimization problem. Numerical inversions are performed for the diffusion coefficient taking on different functional forms and the additional data having random noise. Several factors which have important influences on the realization of the algorithm are discussed, including the approximate space of the diffusion coefficient, the regularization parameter and the initial iteration. The inversion solutions are good approximations to the exact solutions with stability and adaptivity demonstrating that the optimal perturbation algorithm with the sigmoid-type regularization parameter is efficient for the simultaneous inversion. (paper)
Argüeso, D.; Hidalgo-Muñoz, J. M.; Gámiz-Fortis, S. R.; Esteban-Parra, M. J.; Castro-Díez, Y.
2009-04-01
An evaluation of MM5 mesoscale model sensitivity to different parameterizations schemes is presented in terms of temperature and precipitation for high-resolution integrations over Andalusia (South of Spain). As initial and boundary conditions ERA-40 Reanalysis data are used. Two domains were used, a coarse one with dimensions of 55 by 60 grid points with spacing of 30 km and a nested domain of 48 by 72 grid points grid spaced 10 km. Coarse domain fully covers Iberian Peninsula and Andalusia fits loosely in the finer one. In addition to parameterization tests, two dynamical downscaling techniques have been applied in order to examine the influence of initial conditions on RCM long-term studies. Regional climate studies usually employ continuous integration for the period under survey, initializing atmospheric fields only at the starting point and feeding boundary conditions regularly. An alternative approach is based on frequent re-initialization of atmospheric fields; hence the simulation is divided in several independent integrations. Altogether, 20 simulations have been performed using varying physics options, of which 4 were fulfilled applying the re-initialization technique. Surface temperature and accumulated precipitation (daily and monthly scale) were analyzed for a 5-year period covering from 1990 to 1994. Results have been compared with daily observational data series from 110 stations for temperature and 95 for precipitation Both daily and monthly average temperatures are generally well represented by the model. Conversely, daily precipitation results present larger deviations from observational data. However, noticeable accuracy is gained when comparing with monthly precipitation observations. There are some especially conflictive subregions where precipitation is scarcely captured, such as the Southeast of the Iberian Peninsula, mainly due to its extremely convective nature. Regarding parameterization schemes performance, every set provides very
The package PAKPDF 1.1 of parameterizations of parton distribution functions in the proton
International Nuclear Information System (INIS)
Charchula, K.
1992-01-01
A FORTRAN package containing parameterizations of parton distribution functions (PDFs) in the proton is described, allows an easy access to PDFs provided by several recent parameterizations and to some parameters characterizing particular parameterization. Some comments about the use of various parameterizations are also included. (orig.)
Parameterization analysis and inversion for orthorhombic media
Masmoudi, Nabil
2018-01-01
Accounting for azimuthal anisotropy is necessary for the processing and inversion of wide-azimuth and wide-aperture seismic data because wave speeds naturally depend on the wave propagation direction. Orthorhombic anisotropy is considered the most
Carleo, Giuseppe; Cevolani, Lorenzo; Sanchez-Palencia, Laurent; Holzmann, Markus
2017-07-01
We introduce the time-dependent variational Monte Carlo method for continuous-space Bose gases. Our approach is based on the systematic expansion of the many-body wave function in terms of multibody correlations and is essentially exact up to adaptive truncation. The method is benchmarked by comparison to an exact Bethe ansatz or existing numerical results for the integrable Lieb-Liniger model. We first show that the many-body wave function achieves high precision for ground-state properties, including energy and first-order as well as second-order correlation functions. Then, we study the out-of-equilibrium, unitary dynamics induced by a quantum quench in the interaction strength. Our time-dependent variational Monte Carlo results are benchmarked by comparison to exact Bethe ansatz results available for a small number of particles, and are also compared to quench action results available for noninteracting initial states. Moreover, our approach allows us to study large particle numbers and general quench protocols, previously inaccessible beyond the mean-field level. Our results suggest that it is possible to find correlated initial states for which the long-term dynamics of local density fluctuations is close to the predictions of a simple Boltzmann ensemble.
Self-consistent DFT +U method for real-space time-dependent density functional theory calculations
Tancogne-Dejean, Nicolas; Oliveira, Micael J. T.; Rubio, Angel
2017-12-01
We implemented various DFT+U schemes, including the Agapito, Curtarolo, and Buongiorno Nardelli functional (ACBN0) self-consistent density-functional version of the DFT +U method [Phys. Rev. X 5, 011006 (2015), 10.1103/PhysRevX.5.011006] within the massively parallel real-space time-dependent density functional theory (TDDFT) code octopus. We further extended the method to the case of the calculation of response functions with real-time TDDFT+U and to the description of noncollinear spin systems. The implementation is tested by investigating the ground-state and optical properties of various transition-metal oxides, bulk topological insulators, and molecules. Our results are found to be in good agreement with previously published results for both the electronic band structure and structural properties. The self-consistent calculated values of U and J are also in good agreement with the values commonly used in the literature. We found that the time-dependent extension of the self-consistent DFT+U method yields improved optical properties when compared to the empirical TDDFT+U scheme. This work thus opens a different theoretical framework to address the nonequilibrium properties of correlated systems.
Current state of aerosol nucleation parameterizations for air-quality and climate modeling
Semeniuk, Kirill; Dastoor, Ashu
2018-04-01
Aerosol nucleation parameterization models commonly used in 3-D air quality and climate models have serious limitations. This includes classical nucleation theory based variants, empirical models and other formulations. Recent work based on detailed and extensive laboratory measurements and improved quantum chemistry computation has substantially advanced the state of nucleation parameterizations. In terms of inorganic nucleation involving BHN and THN including ion effects these new models should be considered as worthwhile replacements for the old models. However, the contribution of organic species to nucleation remains poorly quantified. New particle formation consists of a distinct post-nucleation growth regime which is characterized by a strong Kelvin curvature effect and is thus dependent on availability of very low volatility organic species or sulfuric acid. There have been advances in the understanding of the multiphase chemistry of biogenic and anthropogenic organic compounds which facilitate to overcome the initial aerosol growth barrier. Implementation of processes influencing new particle formation is challenging in 3-D models and there is a lack of comprehensive parameterizations. This review considers the existing models and recent innovations.
Natarajan, Murali; Fairlie, T. Duncan; Dwyer Cianciolo, Alicia; Smith, Michael D.
2015-01-01
We use the mesoscale modeling capability of Mars Weather Research and Forecasting (MarsWRF) model to study the sensitivity of the simulated Martian lower atmosphere to differences in the parameterization of the planetary boundary layer (PBL). Characterization of the Martian atmosphere and realistic representation of processes such as mixing of tracers like dust depend on how well the model reproduces the evolution of the PBL structure. MarsWRF is based on the NCAR WRF model and it retains some of the PBL schemes available in the earth version. Published studies have examined the performance of different PBL schemes in NCAR WRF with the help of observations. Currently such assessments are not feasible for Martian atmospheric models due to lack of observations. It is of interest though to study the sensitivity of the model to PBL parameterization. Typically, for standard Martian atmospheric simulations, we have used the Medium Range Forecast (MRF) PBL scheme, which considers a correction term to the vertical gradients to incorporate nonlocal effects. For this study, we have also used two other parameterizations, a non-local closure scheme called Yonsei University (YSU) PBL scheme and a turbulent kinetic energy closure scheme called Mellor- Yamada-Janjic (MYJ) PBL scheme. We will present intercomparisons of the near surface temperature profiles, boundary layer heights, and wind obtained from the different simulations. We plan to use available temperature observations from Mini TES instrument onboard the rovers Spirit and Opportunity in evaluating the model results.
Impact of Physics Parameterization Ordering in a Global Atmosphere Model
Donahue, Aaron S.; Caldwell, Peter M.
2018-02-01
Because weather and climate models must capture a wide variety of spatial and temporal scales, they rely heavily on parameterizations of subgrid-scale processes. The goal of this study is to demonstrate that the assumptions used to couple these parameterizations have an important effect on the climate of version 0 of the Energy Exascale Earth System Model (E3SM) General Circulation Model (GCM), a close relative of version 1 of the Community Earth System Model (CESM1). Like most GCMs, parameterizations in E3SM are sequentially split in the sense that parameterizations are called one after another with each subsequent process feeling the effect of the preceding processes. This coupling strategy is noncommutative in the sense that the order in which processes are called impacts the solution. By examining a suite of 24 simulations with deep convection, shallow convection, macrophysics/microphysics, and radiation parameterizations reordered, process order is shown to have a big impact on predicted climate. In particular, reordering of processes induces differences in net climate feedback that are as big as the intermodel spread in phase 5 of the Coupled Model Intercomparison Project. One reason why process ordering has such a large impact is that the effect of each process is influenced by the processes preceding it. Where output is written is therefore an important control on apparent model behavior. Application of k-means clustering demonstrates that the positioning of macro/microphysics and shallow convection plays a critical role on the model solution.
International Nuclear Information System (INIS)
Belo, Thiago F.; Fiel, Joao Claudio B.
2015-01-01
Nuclear reactor core analysis involves neutronic modeling and the calculations require problem dependent nuclear data generated with few neutron energy groups, as for instance the neutron cross sections. The methods used to obtain these problem-dependent cross sections, in the reactor calculations, generally uses nuclear computer codes that require a large processing time and computational memory, making the process computationally very expensive. Presently, analysis of the macroscopic cross section, as a function of nuclear parameters, has shown a very distinct behavior that cannot be represented by simply using linear interpolation. Indeed, a polynomial representation is more adequate for the data parameterization. To provide the cross sections of rapidly and without the dependence of complex systems calculations, this work developed a set of parameterized cross sections, based on the Tchebychev polynomials, by fitting the cross sections as a function of nuclear parameters, which include fuel temperature, moderator temperature and density, soluble boron concentration, uranium enrichment, and the burn-up. In this study is evaluated the problem-dependent about fission, scattering, total, nu-fission, capture, transport and absorption cross sections for a typical PWR fuel element reactor, considering burn-up cycle. The analysis was carried out with the SCALE 6.1 code package. The results of comparison with direct calculations with the SCALE code system and also the test using project parameters, such as the temperature coefficient of reactivity and fast fission factor, show excellent agreements. The differences between the cross-section parameterization methodology and the direct calculations based on the SCALE code system are less than 0.03 percent. (author)
Energy Technology Data Exchange (ETDEWEB)
Belo, Thiago F.; Fiel, Joao Claudio B., E-mail: thiagofbelo@hotmail.com [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil)
2015-07-01
Nuclear reactor core analysis involves neutronic modeling and the calculations require problem dependent nuclear data generated with few neutron energy groups, as for instance the neutron cross sections. The methods used to obtain these problem-dependent cross sections, in the reactor calculations, generally uses nuclear computer codes that require a large processing time and computational memory, making the process computationally very expensive. Presently, analysis of the macroscopic cross section, as a function of nuclear parameters, has shown a very distinct behavior that cannot be represented by simply using linear interpolation. Indeed, a polynomial representation is more adequate for the data parameterization. To provide the cross sections of rapidly and without the dependence of complex systems calculations, this work developed a set of parameterized cross sections, based on the Tchebychev polynomials, by fitting the cross sections as a function of nuclear parameters, which include fuel temperature, moderator temperature and density, soluble boron concentration, uranium enrichment, and the burn-up. In this study is evaluated the problem-dependent about fission, scattering, total, nu-fission, capture, transport and absorption cross sections for a typical PWR fuel element reactor, considering burn-up cycle. The analysis was carried out with the SCALE 6.1 code package. The results of comparison with direct calculations with the SCALE code system and also the test using project parameters, such as the temperature coefficient of reactivity and fast fission factor, show excellent agreements. The differences between the cross-section parameterization methodology and the direct calculations based on the SCALE code system are less than 0.03 percent. (author)
Directory of Open Access Journals (Sweden)
Madeline R Carins Murphy
Full Text Available Producing leaves with closely spaced veins is a key innovation linked to high rates of photosynthesis in angiosperms. A close geometric link between veins and stomata in angiosperms ensures that investment in enhanced venous water transport provides the strongest net carbon return to the plant. This link is underpinned by "passive dilution" via expansion of surrounding cells. However, it is not known whether this 'passive dilution' mechanism is present in plant lineages other than angiosperms and is another key feature of the angiosperms' evolutionary success. Consequently, we sought to determine whether the 'passive dilution' mechanism is; (i exclusive to the angiosperms, (ii a conserved mechanism that evolved in the common ancestor of ferns and angiosperms, or (iii has evolved continuously over time. To do this we first we assessed the plasticity of vein and stomatal density and epidermal cell size in ferns in response to light environment. We then compared the relationships between these traits found among ferns with modelled relationships that assume vein and stomatal density respond passively to epidermal cell expansion, and with those previously observed in angiosperms. Vein density, stomatal density and epidermal cell size were linked in ferns with remarkably similar relationships to those observed in angiosperms, except that fern leaves had fewer veins per stomata. However, plasticity was limited in ferns and stomatal spacing was dependent on active stomatal differentiation as well as passive cell expansion. Thus, ferns (like angiosperms appear to coordinate vein and stomatal density with epidermal cell expansion to some extent to maintain a constant ratio between veins and stomata in the leaf. The different general relationships between vein density and stomatal density in ferns and angiosperms suggests the groups have different optimum balances between the production of vein tissue dedicated to water supply and stomatal tissue for gas
International Nuclear Information System (INIS)
Molique, H.; Dudek, J.
1997-01-01
A particle-number conserving approach is presented to solve the nuclear mean-field plus pairing Hamiltonian problem with a realistic deformed Woods-Saxon single-particle potential. The method is designed for the state-dependent monopole pairing Hamiltonian H pair =summation αβ G αβ c α † c bar α † c bar β c β with an arbitrary set of matrix elements G αβ . Symmetries of the Hamiltonians on the many-body level are discussed using the language of P symmetry introduced earlier in the literature and are employed to diagonalize the problem; the only essential approximation used is a many-body (Fock-space) basis cutoff. An optimal basis construction is discussed and the stability of the final result with respect to the basis cutoff is illustrated in details. Extensions of the concept of P symmetry are introduced and their consequences for an optimal many-body basis cutoff construction are exploited. An algorithm is constructed allowing to solve the pairing problems in the many-body spaces corresponding to p∼40 particles on n∼80 levels and for several dozens of lowest lying states with precision ∼(1 endash 2) % within seconds of the CPU time on a CRAY computer. Among applications, the presence of the low-lying seniority s=0 solutions, that are usually poorly described in terms of the standard approximations (BCS, HFB), is discussed and demonstrated to play a role in the interpretation of the spectra of rotating nuclei. copyright 1997 The American Physical Society
Development of a parameterization scheme of mesoscale convective systems
International Nuclear Information System (INIS)
Cotton, W.R.
1994-01-01
The goal of this research is to develop a parameterization scheme of mesoscale convective systems (MCS) including diabatic heating, moisture and momentum transports, cloud formation, and precipitation. The approach is to: Perform explicit cloud-resolving simulation of MCSs; Perform statistical analyses of simulated MCSs to assist in fabricating a parameterization, calibrating coefficients, etc.; Test the parameterization scheme against independent field data measurements and in numerical weather prediction (NWP) models emulating general circulation model (GCM) grid resolution. Thus far we have formulated, calibrated, implemented and tested a deep convective engine against explicit Florida sea breeze convection and in coarse-grid regional simulations of mid-latitude and tropical MCSs. Several explicit simulations of MCSs have been completed, and several other are in progress. Analysis code is being written and run on the explicitly simulated data
Parameterized Analysis of Paging and List Update Algorithms
DEFF Research Database (Denmark)
Dorrigiv, Reza; Ehmsen, Martin R.; López-Ortiz, Alejandro
2015-01-01
that a larger cache leads to a better performance. We also apply the parameterized analysis framework to list update and show that certain randomized algorithms which are superior to MTF in the classical model are not so in the parameterized case, which matches experimental results....... set model and express the performance of well known algorithms in terms of this parameter. This explicitly introduces parameterized-style analysis to online algorithms. The idea is that rather than normalizing the performance of an online algorithm by an (optimal) offline algorithm, we explicitly...... express the behavior of the algorithm in terms of two more natural parameters: the size of the cache and Denning’s working set measure. This technique creates a performance hierarchy of paging algorithms which better reflects their experimentally observed relative strengths. It also reflects the intuition...
Droplet Nucleation: Physically-Based Parameterizations and Comparative Evaluation
Directory of Open Access Journals (Sweden)
Steve Ghan
2011-10-01
Full Text Available One of the greatest sources of uncertainty in simulations of climate and climate change is the influence of aerosols on the optical properties of clouds. The root of this influence is the droplet nucleation process, which involves the spontaneous growth of aerosol into cloud droplets at cloud edges, during the early stages of cloud formation, and in some cases within the interior of mature clouds. Numerical models of droplet nucleation represent much of the complexity of the process, but at a computational cost that limits their application to simulations of hours or days. Physically-based parameterizations of droplet nucleation are designed to quickly estimate the number nucleated as a function of the primary controlling parameters: the aerosol number size distribution, hygroscopicity and cooling rate. Here we compare and contrast the key assumptions used in developing each of the most popular parameterizations and compare their performances under a variety of conditions. We find that the more complex parameterizations perform well under a wider variety of nucleation conditions, but all parameterizations perform well under the most common conditions. We then discuss the various applications of the parameterizations to cloud-resolving, regional and global models to study aerosol effects on clouds at a wide range of spatial and temporal scales. We compare estimates of anthropogenic aerosol indirect effects using two different parameterizations applied to the same global climate model, and find that the estimates of indirect effects differ by only 10%. We conclude with a summary of the outstanding challenges remaining for further development and application.
Parameterization of radiocaesium soil-plant transfer using soil characteristics
International Nuclear Information System (INIS)
Konoplev, A. V.; Drissner, J.; Klemt, E.; Konopleva, I. V.; Zibold, G.
1996-01-01
A model of radionuclide soil-plant transfer is proposed to parameterize the transfer factor by soil and soil solution characteristics. The model is tested with experimental data on the aggregated transfer factor T ag and soil parameters for 8 forest sites in Baden-Wuerttemberg. It is shown that the integral soil-plant transfer factor can be parameterized through radiocaesium exchangeability, capacity of selective sorption sites and ion composition of the soil solution or the water extract. A modified technique of (FES) measurement for soils with interlayer collapse is proposed. (author)
Directory of Open Access Journals (Sweden)
J. Tonttila
2013-08-01
Full Text Available A new method for parameterizing the subgrid variations of vertical velocity and cloud droplet number concentration (CDNC is presented for general circulation models (GCMs. These parameterizations build on top of existing parameterizations that create stochastic subgrid cloud columns inside the GCM grid cells, which can be employed by the Monte Carlo independent column approximation approach for radiative transfer. The new model version adds a description for vertical velocity in individual subgrid columns, which can be used to compute cloud activation and the subgrid distribution of the number of cloud droplets explicitly. Autoconversion is also treated explicitly in the subcolumn space. This provides a consistent way of simulating the cloud radiative effects with two-moment cloud microphysical properties defined at subgrid scale. The primary impact of the new parameterizations is to decrease the CDNC over polluted continents, while over the oceans the impact is smaller. Moreover, the lower CDNC induces a stronger autoconversion of cloud water to rain. The strongest reduction in CDNC and cloud water content over the continental areas promotes weaker shortwave cloud radiative effects (SW CREs even after retuning the model. However, compared to the reference simulation, a slightly stronger SW CRE is seen e.g. over mid-latitude oceans, where CDNC remains similar to the reference simulation, and the in-cloud liquid water content is slightly increased after retuning the model.
Baxley, Brian T.; Murdoch, Jennifer L.; Swieringa, Kurt A.; Barmore, Bryan E.; Capron, William R.; Hubbs, Clay E.; Shay, Richard F.; Abbott, Terence S.
2013-01-01
The predicted increase in the number of commercial aircraft operations creates a need for improved operational efficiency. Two areas believed to offer increases in aircraft efficiency are optimized profile descents and dependent parallel runway operations. Using Flight deck Interval Management (FIM) software and procedures during these operations, flight crews can achieve by the runway threshold an interval assigned by air traffic control (ATC) behind the preceding aircraft that maximizes runway throughput while minimizing additional fuel consumption and pilot workload. This document describes an experiment where 24 pilots flew arrivals into the Dallas Fort-Worth terminal environment using one of three simulators at NASA?s Langley Research Center. Results indicate that pilots delivered their aircraft to the runway threshold within +/- 3.5 seconds of their assigned time interval, and reported low workload levels. In general, pilots found the FIM concept, procedures, speeds, and interface acceptable. Analysis of the time error and FIM speed changes as a function of arrival stream position suggest the spacing algorithm generates stable behavior while in the presence of continuous (wind) or impulse (offset) error. Concerns reported included multiple speed changes within a short time period, and an airspeed increase followed shortly by an airspeed decrease.
Energy Technology Data Exchange (ETDEWEB)
Gharaei, R.; Hadikhani, A. [Hakim Sabzevari University, Department of Physics, Sciences Faculty, Sabzevar (Iran, Islamic Republic of)
2017-07-15
For the first time the influence of the surface energy coefficient γ and temperature T on the parameterization of the fusion barriers is systematically analyzed within the framework of the proximity formalism, namely proximity 1977, proximity 1988 and proximity 2010 models. A total of 114 fusion reactions with the condition 39 ≤ Z{sub 1}Z{sub 2} ≤ 1520 for the charge product of their participant nuclei have been studied. We present γ-dependent and T -dependent pocket formulas which reproduce the theoretical and empirical data of the fusion barrier height and position for our considered reactions with good accuracy. It is shown that the quality of the γ-dependent formula enhances by increasing the strength of the surface energy coefficient. Moreover, the obtained results confirm that imposing the thermal effects improves the agreement between the parameterized and empirical data of the barrier characteristics. (orig.)
Johnson, E. S.; Rupper, S.; Steenburgh, W. J.; Strong, C.; Kochanski, A.
2017-12-01
Climate model outputs are often used as inputs to glacier energy and mass balance models, which are essential glaciological tools for testing glacier sensitivity, providing mass balance estimates in regions with little glaciological data, and providing a means to model future changes. Climate model outputs, however, are sensitive to the choice of physical parameterizations, such as those for cloud microphysics, land-surface schemes, surface layer options, etc. Furthermore, glacier mass balance (MB) estimates that use these climate model outputs as inputs are likely sensitive to the specific parameterization schemes, but this sensitivity has not been carefully assessed. Here we evaluate the sensitivity of glacier MB estimates across the Indus Basin to the selection of cloud microphysics parameterizations in the Weather Research and Forecasting Model (WRF). Cloud microphysics parameterizations differ in how they specify the size distributions of hydrometeors, the rate of graupel and snow production, their fall speed assumptions, the rates at which they convert from one hydrometeor type to the other, etc. While glacier MB estimates are likely sensitive to other parameterizations in WRF, our preliminary results suggest that glacier MB is highly sensitive to the timing, frequency, and amount of snowfall, which is influenced by the cloud microphysics parameterization. To this end, the Indus Basin is an ideal study site, as it has both westerly (winter) and monsoonal (summer) precipitation influences, is a data-sparse region (so models are critical), and still has lingering questions as to glacier importance for local and regional resources. WRF is run at a 4 km grid scale using two commonly used parameterizations: the Thompson scheme and the Goddard scheme. On average, these parameterizations result in minimal differences in annual precipitation. However, localized regions exhibit differences in precipitation of up to 3 m w.e. a-1. The different schemes also impact the
Gherboudj, Imen; Beegum, S. Naseema; Marticorena, Beatrice; Ghedira, Hosni
2015-10-01
The mineral dust emissions from arid/semiarid soils were simulated over the MENA (Middle East and North Africa) region using the dust parameterization scheme proposed by Alfaro and Gomes (2001), to quantify the effect of the soil moisture and clay fraction in the emissions. For this purpose, an extensive data set of Soil Moisture and Ocean Salinity soil moisture, European Centre for Medium-Range Weather Forecasting wind speed at 10 m height, Food Agricultural Organization soil texture maps, MODIS (Moderate Resolution Imaging Spectroradiometer) Normalized Difference Vegetation Index, and erodibility of the soil surface were collected for the a period of 3 years, from 2010 to 2013. Though the considered data sets have different temporal and spatial resolution, efforts have been made to make them consistent in time and space. At first, the simulated sandblasting flux over the region were validated qualitatively using MODIS Deep Blue aerosol optical depth and EUMETSAT MSG (Meteosat Seciond Generation) dust product from SEVIRI (Meteosat Spinning Enhanced Visible and Infrared Imager) and quantitatively based on the available ground-based measurements of near-surface particulate mass concentrations (PM10) collected over four stations in the MENA region. Sensitivity analyses were performed to investigate the effect of soil moisture and clay fraction on the emissions flux. The results showed that soil moisture and soil texture have significant roles in the dust emissions over the MENA region, particularly over the Arabian Peninsula. An inversely proportional dependency is observed between the soil moisture and the sandblasting flux, where a steep reduction in flux is observed at low friction velocity and a gradual reduction is observed at high friction velocity. Conversely, a directly proportional dependency is observed between the soil clay fraction and the sandblasting flux where a steep increase in flux is observed at low friction velocity and a gradual increase is
Gravitational wave tests of general relativity with the parameterized post-Einsteinian framework
International Nuclear Information System (INIS)
Cornish, Neil; Sampson, Laura; Yunes, Nicolas; Pretorius, Frans
2011-01-01
Gravitational wave astronomy has tremendous potential for studying extreme astrophysical phenomena and exploring fundamental physics. The waves produced by binary black hole mergers will provide a pristine environment in which to study strong-field dynamical gravity. Extracting detailed information about these systems requires accurate theoretical models of the gravitational wave signals. If gravity is not described by general relativity, analyses that are based on waveforms derived from Einstein's field equations could result in parameter biases and a loss of detection efficiency. A new class of ''parameterized post-Einsteinian'' waveforms has been proposed to cover this eventuality. Here, we apply the parameterized post-Einsteinian approach to simulated data from a network of advanced ground-based interferometers and from a future space-based interferometer. Bayesian inference and model selection are used to investigate parameter biases, and to determine the level at which departures from general relativity can be detected. We find that in some cases the parameter biases from assuming the wrong theory can be severe. We also find that gravitational wave observations will beat the existing bounds on deviations from general relativity derived from the orbital decay of binary pulsars by a large margin across a wide swath of parameter space.
Vorobyov, E. I.
2010-01-01
We study numerically the applicability of the effective-viscosity approach for simulating the effect of gravitational instability (GI) in disks of young stellar objects with different disk-to-star mass ratios ξ . We adopt two α-parameterizations for the effective viscosity based on Lin and Pringle [Lin, D.N.C., Pringle, J.E., 1990. ApJ 358, 515] and Kratter et al. [Kratter, K.M., Matzner, Ch.D., Krumholz, M.R., 2008. ApJ 681, 375] and compare the resultant disk structure, disk and stellar masses, and mass accretion rates with those obtained directly from numerical simulations of self-gravitating disks around low-mass (M∗ ∼ 1.0M⊙) protostars. We find that the effective viscosity can, in principle, simulate the effect of GI in stellar systems with ξ≲ 0.2- 0.3 , thus corroborating a similar conclusion by Lodato and Rice [Lodato, G., Rice, W.K.M., 2004. MNRAS 351, 630] that was based on a different α-parameterization. In particular, the Kratter et al.'s α-parameterization has proven superior to that of Lin and Pringle's, because the success of the latter depends crucially on the proper choice of the α-parameter. However, the α-parameterization generally fails in stellar systems with ξ≳ 0.3 , particularly in the Classes 0 and I phases of stellar evolution, yielding too small stellar masses and too large disk-to-star mass ratios. In addition, the time-averaged mass accretion rates onto the star are underestimated in the early disk evolution and greatly overestimated in the late evolution. The failure of the α-parameterization in the case of large ξ is caused by a growing strength of low-order spiral modes in massive disks. Only in the late Class II phase, when the magnitude of spiral modes diminishes and the mode-to-mode interaction ensues, may the effective viscosity be used to simulate the effect of GI in stellar systems with ξ≳ 0.3 . A simple modification of the effective viscosity that takes into account disk fragmentation can somewhat improve
Trinh, Lan Anh; Ekström, Mikael; Cürüklü, Baran
2018-01-01
Recent industrial developments in autonomous systems, or agents, which assume that humans and the agents share the same space or even work in close proximity, open for new challenges in robotics, especially in motion planning and control. In these settings, the control system should be able to provide these agents a reliable path following control when they are working in a group or in collaboration with one or several humans in complex and dynamic environments. In such scenarios, these agents are not only moving to reach their goals, i.e., locations, they are also aware of the movements of other entities to find a collision-free path. Thus, this paper proposes a dependable, i.e., safe, reliable and effective, path planning algorithm for a group of agents that share their working space with humans. Firstly, the method employs the Theta * algorithm to initialize the paths from a starting point to a goal for a set of agents. As Theta * algorithm is computationally heavy, it only reruns when there is a significant change of the environment. To deal with the movements of the agents, a static flow field along the configured path is defined. This field is used by the agents to navigate and reach their goals even if the planned trajectories are changed. Secondly, a dipole field is calculated to avoid the collision of agents with other agents and human subjects. In this approach, each agent is assumed to be a source of a magnetic dipole field in which the magnetic moment is aligned with the moving direction of the agent. The magnetic dipole-dipole interactions between these agents generate repulsive forces to help them to avoid collision. The effectiveness of the proposed approach has been evaluated with extensive simulations. The results show that the static flow field is able to drive agents to the goals with a small number of requirements to update the path of agents. Meanwhile, the dipole flow field plays an important role to prevent collisions. The combination of
Directory of Open Access Journals (Sweden)
Lan Anh Trinh
2018-06-01
Full Text Available Recent industrial developments in autonomous systems, or agents, which assume that humans and the agents share the same space or even work in close proximity, open for new challenges in robotics, especially in motion planning and control. In these settings, the control system should be able to provide these agents a reliable path following control when they are working in a group or in collaboration with one or several humans in complex and dynamic environments. In such scenarios, these agents are not only moving to reach their goals, i.e., locations, they are also aware of the movements of other entities to find a collision-free path. Thus, this paper proposes a dependable, i.e., safe, reliable and effective, path planning algorithm for a group of agents that share their working space with humans. Firstly, the method employs the Theta* algorithm to initialize the paths from a starting point to a goal for a set of agents. As Theta* algorithm is computationally heavy, it only reruns when there is a significant change of the environment. To deal with the movements of the agents, a static flow field along the configured path is defined. This field is used by the agents to navigate and reach their goals even if the planned trajectories are changed. Secondly, a dipole field is calculated to avoid the collision of agents with other agents and human subjects. In this approach, each agent is assumed to be a source of a magnetic dipole field in which the magnetic moment is aligned with the moving direction of the agent. The magnetic dipole-dipole interactions between these agents generate repulsive forces to help them to avoid collision. The effectiveness of the proposed approach has been evaluated with extensive simulations. The results show that the static flow field is able to drive agents to the goals with a small number of requirements to update the path of agents. Meanwhile, the dipole flow field plays an important role to prevent collisions. The
Electron Cloud Parameterization Studies in the LHC
Dominguez, O; Baglin, V; Bregliozzi, G; Jimenez, J M; Metral, E; Rumolo, G; Schulte, D; Zimmermann, F
2011-01-01
During LHC beam commissioning with 150, 75 and 50-ns bunch spacing, important electron-cloud effects, like pressure rise, cryogenic heat load, beam instabilities or emittance growth, were observed. The main strategy to combat the LHC electron cloud, defined about ten years ago, relies on the surface conditioning arising from the chamber-surface bombardment with cloud electrons. In a standard model, the conditioning state of the beam-pipe surface is characterized by three parameters: 1. most importantly, the secondary emission yield δmax; 2. the incident electron energy at which the yield is maximum, ε_max; and 3. the probability of elastic reflection of low-energy primary electrons hitting the chamber wall, R. Since at the LHC no in-situ secondary-yield measurements are available, we compare the relative local pressure-rise measurements taken for different beam configurations against simulations in which surface parameters are scanned. This benchmarking of measurements and simulations is used to infer the s...
Impact of cloud microphysics and cumulus parameterization on ...
Indian Academy of Sciences (India)
2007-10-09
Oct 9, 2007 ... Bangladesh. Weather Research and Forecast (WRF–ARW version) modelling system with six dif- .... tem intensified rapidly into a land depression over southern part of ... Impact of cloud microphysics and cumulus parameterization on heavy rainfall. 261 .... tent and temperature and is represented as a sum.
Parameterization of planetary wave breaking in the middle atmosphere
Garcia, Rolando R.
1991-01-01
A parameterization of planetary wave breaking in the middle atmosphere has been developed and tested in a numerical model which includes governing equations for a single wave and the zonal-mean state. The parameterization is based on the assumption that wave breaking represents a steady-state equilibrium between the flux of wave activity and its dissipation by nonlinear processes, and that the latter can be represented as linear damping of the primary wave. With this and the additional assumption that the effect of breaking is to prevent further amplitude growth, the required dissipation rate is readily obtained from the steady-state equation for wave activity; diffusivity coefficients then follow from the dissipation rate. The assumptions made in the derivation are equivalent to those commonly used in parameterizations for gravity wave breaking, but the formulation in terms of wave activity helps highlight the central role of the wave group velocity in determining the dissipation rate. Comparison of model results with nonlinear calculations of wave breaking and with diagnostic determinations of stratospheric diffusion coefficients reveals remarkably good agreement, and suggests that the parameterization could be useful for simulating inexpensively, but realistically, the effects of planetary wave transport.
Stable Kernel Representations and the Youla Parameterization for Nonlinear Systems
Paice, A.D.B.; Schaft, A.J. van der
1994-01-01
In this paper a general approach is taken to yield a characterization of the class of stable plant controller pairs, which is a generalization of the Youla parameterization for linear systems. This is based on the idea of representing the input-output pairs of the plant and controller as elements of
A parameterization of nuclear track profiles in CR-39 detector
Azooz, A. A.; Al-Nia'emi, S. H.; Al-Jubbori, M. A.
2012-11-01
on any theory of liability, whether in contract, strict liability, or tort (including negligence or otherwise) arising in any way out of the use of this software, even if advised of the possibility of such damage. No. of lines in distributed program, including test data, etc.: 15598 No. of bytes in distributed program, including test data, etc.: 3933244 Distribution format: tar.gz Programming language: MATLAB. Computer: Any Desktop or Laptop. Operating system: Windows 1998 or above (with MATLAB R13 or above installed). RAM: 512 Megabytes or higher Classification: 17.5. Nature of problem: A new semispherical parameterization of charged particle tracks in CR-39 SSNTD is carried out in a previous paper. This parameterization is developed here into a MATLAB based software to calculate the track length and track profile for any proton or alpha particle energy or etching time. This software is intended to compete with the TRACK_TEST [1] and TRACK_VISION [2] software currently in use by all people working in the field of SSNTD. Solution method: Based on fitting of experimental results of protons and alpha particles track lengths for various energies and etching times to a new semispherical formula with four free fitting parameters, the best set of energy independent parameters were found. These parameters are introduced into the software and the software is programmed to solve the set of equations to calculate the track depth, track etching rate as a function of both time and residual range for particles of normal and oblique incidence, the track longitudinal profile at both normal and oblique incidence, and the three dimensional track profile at normal incidence. Running time: 1-8 s on Pentium (4) 2 GHz CPU, 3 GB of RAM depending on the etching time value References: [1] ADWT_v1_0 Track_Test Computer program TRACK_TEST for calculating parameters and plotting profiles for etch pits in nuclear track materials. D. Nikezic, K.N. Yu Comput. Phys. Commun. 174(2006)160 [2] AEAF
Energy Technology Data Exchange (ETDEWEB)
Markus Meier, H.E. [Swedish Meteorological and Hydrological Inst., Norrkoeping (Sweden). Rossby Centre
2000-09-01
As mixing plays a dominant role for the physics of an estuary like the Baltic Sea (seasonal heat storage, mixing in channels, deep water mixing), different mixing parameterizations for use in 3D Baltic Sea models are discussed and compared. For this purpose two different OGCMs of the Baltic Sea are utilized. Within the Swedish regional climate modeling program, SWECLIM, a 3D coupled ice-ocean model for the Baltic Sea has been coupled with an improved version of the two-equation k - {epsilon} turbulence model with corrected dissipation term, flux boundary conditions to include the effect of a turbulence enhanced layer due to breaking surface gravity waves and a parameterization for breaking internal waves. Results of multi-year simulations are compared with observations. The seasonal thermocline is simulated satisfactory and erosion of the halocline is avoided. Unsolved problems are discussed. To replace the controversial equation for dissipation the performance of a hierarchy of k-models has been tested and compared with the k - {epsilon} model. In addition, it is shown that the results of the mixing parameterization depend very much on the choice of the ocean model. Finally, the impact of two mixing parameterizations on Baltic Sea climate is investigated. In this case the sensitivity of mean SST, vertical temperature and salinity profiles, ice season and seasonal cycle of heat fluxes is quite large.
Directory of Open Access Journals (Sweden)
Weijian Guo
2015-05-01
Full Text Available Spatial variability plays an important role in nonlinear hydrologic processes. Due to the limitation of computational efficiency and data resolution, subgrid variability is usually assumed to be uniform for most grid-based rainfall-runoff models, which leads to the scale-dependence of model performances. In this paper, the scale effect on the Grid-Xinanjiang model was examined. The bias of the estimation of precipitation, runoff, evapotranspiration and soil moisture at the different grid scales, along with the scale-dependence of the effective parameters, highlights the importance of well representing the subgrid variability. This paper presents a subgrid parameterization method to incorporate the subgrid variability of the soil storage capacity, which is a key variable that controls runoff generation and partitioning in the Grid-Xinanjiang model. In light of the similar spatial pattern and physical basis, the soil storage capacity is correlated with the topographic index, whose spatial distribution can more readily be measured. A beta distribution is introduced to represent the spatial distribution of the soil storage capacity within the grid. The results derived from the Yanduhe Basin show that the proposed subgrid parameterization method can effectively correct the watershed soil storage capacity curve. Compared to the original Grid-Xinanjiang model, the model performances are quite consistent at the different grid scales when the subgrid variability is incorporated. This subgrid parameterization method reduces the recalibration necessity when the Digital Elevation Model (DEM resolution is changed. Moreover, it improves the potential for the application of the distributed model in the ungauged basin.
Biselli, Paolo; Fricke, Kathrin; Grote, Ludger; Braun, Andrew T; Kirkness, Jason; Smith, Philip; Schwartz, Alan; Schneider, Hartmut
2018-05-01
Nasal high flow (NHF) reduces minute ventilation and ventilatory loads during sleep but the mechanisms are not clear. We hypothesised NHF reduces ventilation in proportion to physiological but not anatomical dead space.11 subjects (five controls and six chronic obstructive pulmonary disease (COPD) patients) underwent polysomnography with transcutaneous carbon dioxide (CO 2 ) monitoring under a metabolic hood. During stable non-rapid eye movement stage 2 sleep, subjects received NHF (20 L·min -1 ) intermittently for periods of 5-10 min. We measured CO 2 production and calculated dead space ventilation.Controls and COPD patients responded similarly to NHF. NHF reduced minute ventilation (from 5.6±0.4 to 4.8±0.4 L·min -1 ; pspace ventilation (from 2.5±0.4 to 1.6±0.4 L·min -1 ; pspace ventilation correlated with baseline physiological dead space fraction (r 2 =0.36; pspace volume.During sleep, NHF decreases minute ventilation due to an overall reduction in dead space ventilation in proportion to the extent of baseline physiological dead space fraction. Copyright ©ERS 2018.
Directory of Open Access Journals (Sweden)
Ana Clara Mourão Moura
2013-05-01
Full Text Available The text discusses the state-of-the-art of GIS Technologies in planning and management processes of urban and architectural spaces. It presents latest’s evolution in GIS methodology and applications, discussing how these resources have changed our way of representing and projecting territory. It discusses contemporaneous values, in interventions into urban spaces. The paper also presents legislation’s role in data registers and infrastructure, favoring wide employment of geoprocessing. It announces the arrival of new territorial representation logics, among which is azimuth visualization, considering mental maps, the employment of BIM (Building Information Modeling and the process of parameterization. It points out tendencies and values, such as being inter- operational, creating interpretative portraits for reality, producing simulated scenarios, investing in visualizing and involvement with communities, and fully employing geo-technologies, as aids for decision making. It defends that we are living a new paradigm on territorial planning: the Parametric Modeling of Territorial Occupation.
International Nuclear Information System (INIS)
Hoffman, A. J.; Lee, J. C.
2013-01-01
A new time-dependent neutron transport method based on the method of characteristics (MOC) has been developed. Whereas most spatial kinetics methods treat time dependence through temporal discretization, this new method treats time dependence by defining the characteristics to span space and time. In this implementation regions are defined in space-time where the thickness of the region in time fulfills an analogous role to the time step in discretized methods. The time dependence of the local source is approximated using a truncated Taylor series expansion with high order derivatives approximated using backward differences, permitting the solution of the resulting space-time characteristic equation. To avoid a drastic increase in computational expense and memory requirements due to solving many discrete characteristics in the space-time planes, the temporal variation of the boundary source is similarly approximated. This allows the characteristics in the space-time plane to be represented analytically rather than discretely, resulting in an algorithm comparable in implementation and expense to one that arises from conventional time integration techniques. Furthermore, by defining the boundary flux time derivative in terms of the preceding local source time derivative and boundary flux time derivative, the need to store angularly-dependent data is avoided without approximating the angular dependence of the angular flux time derivative. The accuracy of this method is assessed through implementation in the neutron transport code DeCART. The method is employed with variable-order local source representation to model a TWIGL transient. The results demonstrate that this method is accurate and more efficient than the discretized method. (authors)
Harrington, J. Y.
2017-12-01
Parameterizing the growth of ice particles in numerical models is at an interesting cross-roads. Most parameterizations developed in the past, including some that I have developed, parse model ice into numerous categories based primarily on the growth mode of the particle. Models routinely possess smaller ice, snow crystals, aggregates, graupel, and hail. The snow and ice categories in some models are further split into subcategories to account for the various shapes of ice. There has been a relatively recent shift towards a new class of microphysical models that predict the properties of ice particles instead of using multiple categories and subcategories. Particle property models predict the physical characteristics of ice, such as aspect ratio, maximum dimension, effective density, rime density, effective area, and so forth. These models are attractive in the sense that particle characteristics evolve naturally in time and space without the need for numerous (and somewhat artificial) transitions among pre-defined classes. However, particle property models often require fundamental parameters that are typically derived from laboratory measurements. For instance, the evolution of particle shape during vapor depositional growth requires knowledge of the growth efficiencies for the various axis of the crystals, which in turn depends on surface parameters that can only be determined in the laboratory. The evolution of particle shapes and density during riming, aggregation, and melting require data on the redistribution of mass across a crystals axis as that crystal collects water drops, ice crystals, or melts. Predicting the evolution of particle properties based on laboratory-determined parameters has a substantial influence on the evolution of some cloud systems. Radiatively-driven cirrus clouds show a broader range of competition between heterogeneous nucleation and homogeneous freezing when ice crystal properties are predicted. Even strongly convective squall
Sepehry-Fard, F.; Coulthard, Maurice H.
1995-01-01
The objective of this publication is to introduce the enhancement methods for the overall reliability and maintainability methods of assessment on the International Space Station. It is essential that the process to predict the values of the maintenance time dependent variable parameters such as mean time between failure (MTBF) over time do not in themselves generate uncontrolled deviation in the results of the ILS analysis such as life cycle costs, spares calculation, etc. Furthermore, the very acute problems of micrometeorite, Cosmic rays, flares, atomic oxygen, ionization effects, orbital plumes and all the other factors that differentiate maintainable space operations from non-maintainable space operations and/or ground operations must be accounted for. Therefore, these parameters need be subjected to a special and complex process. Since reliability and maintainability strongly depend on the operating conditions that are encountered during the entire life of the International Space Station, it is important that such conditions are accurately identified at the beginning of the logistics support requirements process. Environmental conditions which exert a strong influence on International Space Station will be discussed in this report. Concurrent (combined) space environments may be more detrimental to the reliability and maintainability of the International Space Station than the effects of a single environment. In characterizing the logistics support requirements process, the developed design/test criteria must consider both the single and/or combined environments in anticipation of providing hardware capability to withstand the hazards of the International Space Station profile. The effects of the combined environments (typical) in a matrix relationship on the International Space Station will be shown. The combinations of the environments where the total effect is more damaging than the cumulative effects of the environments acting singly, may include a
Freitas, S.; Grell, G. A.; Molod, A.
2017-12-01
We implemented and began to evaluate an alternative convection parameterization for the NASA Goddard Earth Observing System (GEOS) global model. The parameterization (Grell and Freitas, 2014) is based on the mass flux approach with several closures, for equilibrium and non-equilibrium convection, and includes scale and aerosol awareness functionalities. Scale dependence for deep convection is implemented either through using the method described by Arakawa et al (2011), or through lateral spreading of the subsidence terms. Aerosol effects are included though the dependence of autoconversion and evaporation on the CCN number concentration.Recently, the scheme has been extended to a tri-modal spectral size approach to simulate the transition from shallow, congestus, and deep convection regimes. In addition, the inclusion of a new closure for non-equilibrium convection resulted in a substantial gain of realism in model simulation of the diurnal cycle of convection over the land. Also, a beta-pdf is employed now to represent the normalized mass flux profile. This opens up an additional venue to apply stochasticism in the scheme.
Advances in understanding, models and parameterizations of biosphere-atmosphere ammonia exchange
Flechard, C. R.; Massad, R.-S.; Loubet, B.; Personne, E.; Simpson, D.; Bash, J. O.; Cooter, E. J.; Nemitz, E.; Sutton, M. A.
2013-07-01
. Their level of complexity depends on their purpose, the spatial scale at which they are applied, the current level of parameterization, and the availability of the input data they require. State-of-the-art solutions for determining the emission/sink Γ potentials through the soil/canopy system include coupled, interactive chemical transport models (CTM) and soil/ecosystem modelling at the regional scale. However, it remains a matter for debate to what extent realistic options for future regional and global models should be based on process-based mechanistic versus empirical and regression-type models. Further discussion is needed on the extent and timescale by which new approaches can be used, such as integration with ecosystem models and satellite observations.
Advances in understanding, models and parameterizations of biosphere-atmosphere ammonia exchange
Directory of Open Access Journals (Sweden)
C. R. Flechard
2013-07-01
-chemical species schemes. Their level of complexity depends on their purpose, the spatial scale at which they are applied, the current level of parameterization, and the availability of the input data they require. State-of-the-art solutions for determining the emission/sink Γ potentials through the soil/canopy system include coupled, interactive chemical transport models (CTM and soil/ecosystem modelling at the regional scale. However, it remains a matter for debate to what extent realistic options for future regional and global models should be based on process-based mechanistic versus empirical and regression-type models. Further discussion is needed on the extent and timescale by which new approaches can be used, such as integration with ecosystem models and satellite observations.
Reyna, D.
2006-01-01
The designs of many neutrino experiments rely on calculations of the background rates arising from cosmic-ray muons at shallow depths. Understanding the angular dependence of low momentum cosmic-ray muons at the surface is necessary for these calculations. Heuristically, from examination of the data, a simple parameterization is proposed, based on a straighforward scaling variable. This in turn, allows a universal calculation of the differential muon intensity at the surface for all zenith an...
Parameterizing Coefficients of a POD-Based Dynamical System
Kalb, Virginia L.
2010-01-01
A method of parameterizing the coefficients of a dynamical system based of a proper orthogonal decomposition (POD) representing the flow dynamics of a viscous fluid has been introduced. (A brief description of POD is presented in the immediately preceding article.) The present parameterization method is intended to enable construction of the dynamical system to accurately represent the temporal evolution of the flow dynamics over a range of Reynolds numbers. The need for this or a similar method arises as follows: A procedure that includes direct numerical simulation followed by POD, followed by Galerkin projection to a dynamical system has been proven to enable representation of flow dynamics by a low-dimensional model at the Reynolds number of the simulation. However, a more difficult task is to obtain models that are valid over a range of Reynolds numbers. Extrapolation of low-dimensional models by use of straightforward Reynolds-number-based parameter continuation has proven to be inadequate for successful prediction of flows. A key part of the problem of constructing a dynamical system to accurately represent the temporal evolution of the flow dynamics over a range of Reynolds numbers is the problem of understanding and providing for the variation of the coefficients of the dynamical system with the Reynolds number. Prior methods do not enable capture of temporal dynamics over ranges of Reynolds numbers in low-dimensional models, and are not even satisfactory when large numbers of modes are used. The basic idea of the present method is to solve the problem through a suitable parameterization of the coefficients of the dynamical system. The parameterization computations involve utilization of the transfer of kinetic energy between modes as a function of Reynolds number. The thus-parameterized dynamical system accurately predicts the flow dynamics and is applicable to a range of flow problems in the dynamical regime around the Hopf bifurcation. Parameter
International Nuclear Information System (INIS)
Ruiz-Arias, J.A.; Pozo-Vasquez, D.; Sanchez-Sanchez, N.; Hayas-Barru, A.; Tovar-Pescador, J.; Montavez, J.P.
2008-01-01
We study the relative performance of two different MM5-PBL parametrizations (Blackadar and MRF) simulating hourly values of solar irradiance and temperature in the south-eastern part of the Iberian Peninsula. The evaluation was carried out throughout the different season of the year 2005 and for three different sky conditions: clear-sky, broken-clouds and overcast conditions. Two integrations, one per PBL parameterization, were carried out for every sky condition and season of the year and results were compared with observational data. Overall, the MM5 model, both using the Blackadar or MRF PBL parameterization, revealed to be a valid tool to estimate hourly values of solar radiation and temperature over the study area. The influence of the PBL parameterization on the model estimates was found to be more important for the solar radiation than for the temperature and highly dependent on the season and sky conditions. Particularly, a detailed analysis revealed that, during broken-clouds conditions, the ability of the model to reproduce hourly changes in the solar radiation strongly depends upon the selected PBL parameterization. Additionally, it was found that solar radiation RMSE values are about one order of magnitude higher during broken-clouds and overcast conditions compared to clear-sky conditions. For the temperature, the two PBL parameterizations provide very similar estimates. Only under overcast conditions and during the autumn, the MRF provides significantly better estimates.
submitter Data-driven RBE parameterization for helium ion beams
Mairani, A; Dokic, I; Valle, S M; Tessonnier, T; Galm, R; Ciocca, M; Parodi, K; Ferrari, A; Jäkel, O; Haberer, T; Pedroni, P; Böhlen, T T
2016-01-01
Helium ion beams are expected to be available again in the near future for clinical use. A suitable formalism to obtain relative biological effectiveness (RBE) values for treatment planning (TP) studies is needed. In this work we developed a data-driven RBE parameterization based on published in vitro experimental values. The RBE parameterization has been developed within the framework of the linear-quadratic (LQ) model as a function of the helium linear energy transfer (LET), dose and the tissue specific parameter ${{(\\alpha /\\beta )}_{\\text{ph}}}$ of the LQ model for the reference radiation. Analytic expressions are provided, derived from the collected database, describing the $\\text{RB}{{\\text{E}}_{\\alpha}}={{\\alpha}_{\\text{He}}}/{{\\alpha}_{\\text{ph}}}$ and ${{\\text{R}}_{\\beta}}={{\\beta}_{\\text{He}}}/{{\\beta}_{\\text{ph}}}$ ratios as a function of LET. Calculated RBE values at 2 Gy photon dose and at 10% survival ($\\text{RB}{{\\text{E}}_{10}}$ ) are compared with the experimental ones. Pearson's correlati...
Parameterized neural networks for high-energy physics
Energy Technology Data Exchange (ETDEWEB)
Baldi, Pierre; Sadowski, Peter [University of California, Department of Computer Science, Irvine, CA (United States); Cranmer, Kyle [NYU, Department of Physics, New York, NY (United States); Faucett, Taylor; Whiteson, Daniel [University of California, Department of Physics and Astronomy, Irvine, CA (United States)
2016-05-15
We investigate a new structure for machine learning classifiers built with neural networks and applied to problems in high-energy physics by expanding the inputs to include not only measured features but also physics parameters. The physics parameters represent a smoothly varying learning task, and the resulting parameterized classifier can smoothly interpolate between them and replace sets of classifiers trained at individual values. This simplifies the training process and gives improved performance at intermediate values, even for complex problems requiring deep learning. Applications include tools parameterized in terms of theoretical model parameters, such as the mass of a particle, which allow for a single network to provide improved discrimination across a range of masses. This concept is simple to implement and allows for optimized interpolatable results. (orig.)
Reliable control using the primary and dual Youla parameterizations
DEFF Research Database (Denmark)
Niemann, Hans Henrik; Stoustrup, J.
2002-01-01
Different aspects of modeling faults in dynamic systems are considered in connection with reliable control (RC). The fault models include models with additive faults, multiplicative faults and structural changes in the models due to faults in the systems. These descriptions are considered...... in connection with reliable control and feedback control with fault rejection. The main emphasis is on fault modeling. A number of fault diagnosis problems, reliable control problems, and feedback control with fault rejection problems are formulated/considered, again, mainly from a fault modeling point of view....... Reliability is introduced by means of the (primary) Youla parameterization of all stabilizing controllers, where an additional loop is closed around a diagnostic signal. In order to quantify the level of reliability, the dual Youla parameterization is introduced which can be used to analyze how large faults...
IR OPTICS MEASUREMENT WITH LINEAR COUPLING'S ACTION-ANGLE PARAMETERIZATION
International Nuclear Information System (INIS)
LUO, Y.; BAI, M.; PILAT, R.; SATOGATA, T.; TRBOJEVIC, D.
2005-01-01
A parameterization of linear coupling in action-angle coordinates is convenient for analytical calculations and interpretation of turn-by-turn (TBT) beam position monitor (BPM) data. We demonstrate how to use this parameterization to extract the twiss and coupling parameters in interaction regions (IRs), using BPMs on each side of the long IR drift region. The example of TBT BPM analysis was acquired at the Relativistic Heavy Ion Collider (RHIC), using an AC dipole to excite a single eigenmode. Besides the full treatment, a fast estimate of beta*, the beta function at the interaction point (IP), is provided, along with the phase advance between these BPMs. We also calculate and measure the waist of the beta function and the local optics
Firefly Algorithm for Polynomial Bézier Surface Parameterization
Directory of Open Access Journals (Sweden)
Akemi Gálvez
2013-01-01
reality, medical imaging, computer graphics, computer animation, and many others. Very often, the preferred approximating surface is polynomial, usually described in parametric form. This leads to the problem of determining suitable parametric values for the data points, the so-called surface parameterization. In real-world settings, data points are generally irregularly sampled and subjected to measurement noise, leading to a very difficult nonlinear continuous optimization problem, unsolvable with standard optimization techniques. This paper solves the parameterization problem for polynomial Bézier surfaces by applying the firefly algorithm, a powerful nature-inspired metaheuristic algorithm introduced recently to address difficult optimization problems. The method has been successfully applied to some illustrative examples of open and closed surfaces, including shapes with singularities. Our results show that the method performs very well, being able to yield the best approximating surface with a high degree of accuracy.
Parameterized neural networks for high-energy physics
International Nuclear Information System (INIS)
Baldi, Pierre; Sadowski, Peter; Cranmer, Kyle; Faucett, Taylor; Whiteson, Daniel
2016-01-01
We investigate a new structure for machine learning classifiers built with neural networks and applied to problems in high-energy physics by expanding the inputs to include not only measured features but also physics parameters. The physics parameters represent a smoothly varying learning task, and the resulting parameterized classifier can smoothly interpolate between them and replace sets of classifiers trained at individual values. This simplifies the training process and gives improved performance at intermediate values, even for complex problems requiring deep learning. Applications include tools parameterized in terms of theoretical model parameters, such as the mass of a particle, which allow for a single network to provide improved discrimination across a range of masses. This concept is simple to implement and allows for optimized interpolatable results. (orig.)
Parameterization of phase change of water in a mesoscale model
Energy Technology Data Exchange (ETDEWEB)
Levkov, L; Eppel, D; Grassl, H
1987-01-01
A parameterization scheme of phase change of water is suggested to be used in the 3-D numerical nonhydrostatic model GESIMA. The microphysical formulation follows the so-called bulk technique. With this procedure the net production rates in the balance equations for water and potential temperature are given both for liquid and ice-phase. Convectively stable as well as convectively unstable mesoscale systems are considered. With 2 figs..
Robust parameterization of elastic and absorptive electron atomic scattering factors
International Nuclear Information System (INIS)
Peng, L.M.; Ren, G.; Dudarev, S.L.; Whelan, M.J.
1996-01-01
A robust algorithm and computer program have been developed for the parameterization of elastic and absorptive electron atomic scattering factors. The algorithm is based on a combined modified simulated-annealing and least-squares method, and the computer program works well for fitting both elastic and absorptive atomic scattering factors with five Gaussians. As an application of this program, the elastic electron atomic scattering factors have been parameterized for all neutral atoms and for s up to 6 A -1 . Error analysis shows that the present results are considerably more accurate than the previous analytical fits in terms of the mean square value of the deviation between the numerical and fitted scattering factors. Parameterization for absorptive atomic scattering factors has been made for 17 important materials with the zinc blende structure over the temperature range 1 to 1000 K, where appropriate, and for temperature ranges for which accurate Debye-Waller factors are available. For other materials, the parameterization of the absorptive electron atomic scattering factors can be made using the program by supplying the atomic number of the element, the Debye-Waller factor and the acceleration voltage. For ions or when more accurate numerical results for neutral atoms are available, the program can read in the numerical values of the elastic scattering factors and return the parameters for both the elastic and absorptive scattering factors. The computer routines developed have been tested both on computer workstations and desktop PC computers, and will be made freely available via electronic mail or on floppy disk upon request. (orig.)
Parameterized Shower Simulation in Lelaps: a Comparison with Geant4
International Nuclear Information System (INIS)
Langeveld, Willy G.J.
2003-01-01
The detector simulation toolkit Lelaps[1] simulates electromagnetic and hadronic showers in calorimetric detector elements of high-energy particle detectors using a parameterization based on the algorithms originally developed by Grindhammer and Peters[2] and Bock et al.[3]. The primary motivations of the present paper are to verify the implementation of the parameterization, to explore regions of energy where the parameterization is valid and to serve as a basis for further improvement of the algorithm. To this end, we compared the Lelaps simulation to a detailed simulation provided by Geant4[4]. A number of different calorimeters, both electromagnetic and hadronic, were implemented in both programs. Longitudinal and radial shower profiles and their fluctuations were obtained from Geant4 over a wide energy range and compared with those obtained from Lelaps. Generally the longitudinal shower profiles are found to be in good agreement in a large part of the energy range, with poorer results at energies below about 300 MeV. Radial profiles agree well in homogeneous detectors, but are somewhat deficient in segmented ones. These deficiencies are discussed
Parameterizing the Spatial Markov Model From Breakthrough Curve Data Alone
Sherman, Thomas; Fakhari, Abbas; Miller, Savannah; Singha, Kamini; Bolster, Diogo
2017-12-01
The spatial Markov model (SMM) is an upscaled Lagrangian model that effectively captures anomalous transport across a diverse range of hydrologic systems. The distinct feature of the SMM relative to other random walk models is that successive steps are correlated. To date, with some notable exceptions, the model has primarily been applied to data from high-resolution numerical simulations and correlation effects have been measured from simulated particle trajectories. In real systems such knowledge is practically unattainable and the best one might hope for is breakthrough curves (BTCs) at successive downstream locations. We introduce a novel methodology to quantify velocity correlation from BTC data alone. By discretizing two measured BTCs into a set of arrival times and developing an inverse model, we estimate velocity correlation, thereby enabling parameterization of the SMM in studies where detailed Lagrangian velocity statistics are unavailable. The proposed methodology is applied to two synthetic numerical problems, where we measure all details and thus test the veracity of the approach by comparison of estimated parameters with known simulated values. Our results suggest that our estimated transition probabilities agree with simulated values and using the SMM with this estimated parameterization accurately predicts BTCs downstream. Our methodology naturally allows for estimates of uncertainty by calculating lower and upper bounds of velocity correlation, enabling prediction of a range of BTCs. The measured BTCs fall within the range of predicted BTCs. This novel method to parameterize the SMM from BTC data alone is quite parsimonious, thereby widening the SMM's practical applicability.
Air quality modeling: evaluation of chemical and meteorological parameterizations
International Nuclear Information System (INIS)
Kim, Youngseob
2011-01-01
The influence of chemical mechanisms and meteorological parameterizations on pollutant concentrations calculated with an air quality model is studied. The influence of the differences between two gas-phase chemical mechanisms on the formation of ozone and aerosols in Europe is low on average. For ozone, the large local differences are mainly due to the uncertainty associated with the kinetics of nitrogen monoxide (NO) oxidation reactions on the one hand and the representation of different pathways for the oxidation of aromatic compounds on the other hand. The aerosol concentrations are mainly influenced by the selection of all major precursors of secondary aerosols and the explicit treatment of chemical regimes corresponding to the nitrogen oxides (NO x ) levels. The influence of the meteorological parameterizations on the concentrations of aerosols and their vertical distribution is evaluated over the Paris region in France by comparison to lidar data. The influence of the parameterization of the dynamics in the atmospheric boundary layer is important; however, it is the use of an urban canopy model that improves significantly the modeling of the pollutant vertical distribution (author) [fr
Parameterizing the Spatial Markov Model from Breakthrough Curve Data Alone
Sherman, T.; Bolster, D.; Fakhari, A.; Miller, S.; Singha, K.
2017-12-01
The spatial Markov model (SMM) uses a correlated random walk and has been shown to effectively capture anomalous transport in porous media systems; in the SMM, particles' future trajectories are correlated to their current velocity. It is common practice to use a priori Lagrangian velocity statistics obtained from high resolution simulations to determine a distribution of transition probabilities (correlation) between velocity classes that govern predicted transport behavior; however, this approach is computationally cumbersome. Here, we introduce a methodology to quantify velocity correlation from Breakthrough (BTC) curve data alone; discretizing two measured BTCs into a set of arrival times and reverse engineering the rules of the SMM allows for prediction of velocity correlation, thereby enabling parameterization of the SMM in studies where Lagrangian velocity statistics are not available. The introduced methodology is applied to estimate velocity correlation from BTCs measured in high resolution simulations, thus allowing for a comparison of estimated parameters with known simulated values. Results show 1) estimated transition probabilities agree with simulated values and 2) using the SMM with estimated parameterization accurately predicts BTCs downstream. Additionally, we include uncertainty measurements by calculating lower and upper estimates of velocity correlation, which allow for prediction of a range of BTCs. The simulated BTCs fall in the range of predicted BTCs. This research proposes a novel method to parameterize the SMM from BTC data alone, thereby reducing the SMM's computational costs and widening its applicability.
A parameterization method and application in breast tomosynthesis dosimetry
Energy Technology Data Exchange (ETDEWEB)
Li, Xinhua; Zhang, Da; Liu, Bob [Division of Diagnostic Imaging Physics and Webster Center for Advanced Research and Education in Radiation, Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts 02114 (United States)
2013-09-15
Purpose: To present a parameterization method based on singular value decomposition (SVD), and to provide analytical parameterization of the mean glandular dose (MGD) conversion factors from eight references for evaluating breast tomosynthesis dose in the Mammography Quality Standards Act (MQSA) protocol and in the UK, European, and IAEA dosimetry protocols.Methods: MGD conversion factor is usually listed in lookup tables for the factors such as beam quality, breast thickness, breast glandularity, and projection angle. The authors analyzed multiple sets of MGD conversion factors from the Hologic Selenia Dimensions quality control manual and seven previous papers. Each data set was parameterized using a one- to three-dimensional polynomial function of 2–16 terms. Variable substitution was used to improve accuracy. A least-squares fit was conducted using the SVD.Results: The differences between the originally tabulated MGD conversion factors and the results computed using the parameterization algorithms were (a) 0.08%–0.18% on average and 1.31% maximum for the Selenia Dimensions quality control manual, (b) 0.09%–0.66% on average and 2.97% maximum for the published data by Dance et al. [Phys. Med. Biol. 35, 1211–1219 (1990); ibid. 45, 3225–3240 (2000); ibid. 54, 4361–4372 (2009); ibid. 56, 453–471 (2011)], (c) 0.74%–0.99% on average and 3.94% maximum for the published data by Sechopoulos et al. [Med. Phys. 34, 221–232 (2007); J. Appl. Clin. Med. Phys. 9, 161–171 (2008)], and (d) 0.66%–1.33% on average and 2.72% maximum for the published data by Feng and Sechopoulos [Radiology 263, 35–42 (2012)], excluding one sample in (d) that does not follow the trends in the published data table.Conclusions: A flexible parameterization method is presented in this paper, and was applied to breast tomosynthesis dosimetry. The resultant data offer easy and accurate computations of MGD conversion factors for evaluating mean glandular breast dose in the MQSA
A stochastic parameterization for deep convection using cellular automata
Bengtsson, L.; Steinheimer, M.; Bechtold, P.; Geleyn, J.
2012-12-01
Cumulus parameterizations used in most operational weather and climate models today are based on the mass-flux concept which took form in the early 1970's. In such schemes it is assumed that a unique relationship exists between the ensemble-average of the sub-grid convection, and the instantaneous state of the atmosphere in a vertical grid box column. However, such a relationship is unlikely to be described by a simple deterministic function (Palmer, 2011). Thus, because of the statistical nature of the parameterization challenge, it has been recognized by the community that it is important to introduce stochastic elements to the parameterizations (for instance: Plant and Craig, 2008, Khouider et al. 2010, Frenkel et al. 2011, Bentsson et al. 2011, but the list is far from exhaustive). There are undoubtedly many ways in which stochastisity can enter new developments. In this study we use a two-way interacting cellular automata (CA), as its intrinsic nature possesses many qualities interesting for deep convection parameterization. In the one-dimensional entraining plume approach, there is no parameterization of horizontal transport of heat, moisture or momentum due to cumulus convection. In reality, mass transport due to gravity waves that propagate in the horizontal can trigger new convection, important for the organization of deep convection (Huang, 1988). The self-organizational characteristics of the CA allows for lateral communication between adjacent NWP model grid-boxes, and temporal memory. Thus the CA scheme used in this study contain three interesting components for representation of cumulus convection, which are not present in the traditional one-dimensional bulk entraining plume method: horizontal communication, memory and stochastisity. The scheme is implemented in the high resolution regional NWP model ALARO, and simulations show enhanced organization of convective activity along squall-lines. Probabilistic evaluation demonstrate an enhanced spread in
Michelson, Sara A.; Bao, Jian-Wen; Grell, Evelyn D.
2017-04-01
Bulk microphysical parameterization schemes are popularly used in numerical weather prediction (NWP) models to simulate clouds and precpitation. These schemes are based on assumed number distribution functions for individual hydrometeor species, which are integratable over size distributions of diameters from zero to infinity. Typically, hydrometeor mass and number mixing ratios are predicted in these schemes. Some schemes also predict a third parameter of hydrometeor distribution characteristics. In this study, four commonly-used microphysics schemes of various complexity that are available in the Weather Research and Forecasting Model (WRF) are investigated and compared using numerical model simulations of an idealized 2-D squall line and microphysics budget analysis. Diagnoses of the parameterized pathways for hydrometeor production reveal that the differences related to the assumptions of hydrometeor size distributions between the schemes lead to the differences in the simulations due to the net effect of various microphysical processes on the interaction between latent heating/evaporative cooling and flow dynamics as the squall line develops. Results from this study also highlight the possibility that the advantage of double-moment formulations can be overshadowed by the uncertainties in the spectral definition of individual hydrometeor categories and spectrum-dependent microphysical processes. It is concluded that the major differences between the schemes investigated here are in the assumed hydrometeor size distributions and pathways for their production.
Evaluation of surface layer flux parameterizations using in-situ observations
Katz, Jeremy; Zhu, Ping
2017-09-01
Appropriate calculation of surface turbulent fluxes between the atmosphere and the underlying ocean/land surface is one of the major challenges in geosciences. In practice, the surface turbulent fluxes are estimated from the mean surface meteorological variables based on the bulk transfer model combined with the Monnin-Obukhov Similarity (MOS) theory. Few studies have been done to examine the extent to which such a flux parameterization can be applied to different weather and surface conditions. A novel validation method is developed in this study to evaluate the surface flux parameterization using in-situ observations collected at a station off the coast of Gulf of Mexico. The main findings are: (a) the theoretical prediction that uses MOS theory does not match well with those directly computed from the observations. (b) The largest spread in exchange coefficients is shown in strong stable conditions with calm winds. (c) Large turbulent eddies, which depend strongly on the mean flow pattern and surface conditions, tend to break the constant flux assumption in the surface layer.
Chekroun, Mickaël D; Wang, Shouhong
2015-01-01
In this second volume, a general approach is developed to provide approximate parameterizations of the "small" scales by the "large" ones for a broad class of stochastic partial differential equations (SPDEs). This is accomplished via the concept of parameterizing manifolds (PMs), which are stochastic manifolds that improve, for a given realization of the noise, in mean square error the partial knowledge of the full SPDE solution when compared to its projection onto some resolved modes. Backward-forward systems are designed to give access to such PMs in practice. The key idea consists of representing the modes with high wave numbers as a pullback limit depending on the time-history of the modes with low wave numbers. Non-Markovian stochastic reduced systems are then derived based on such a PM approach. The reduced systems take the form of stochastic differential equations involving random coefficients that convey memory effects. The theory is illustrated on a stochastic Burgers-type equation.
International Nuclear Information System (INIS)
Agazzi, A.; Gavazzi, C.; Vincenti, E.; Monterosso, R.
1964-01-01
1 - Nature of physical problem solved: The programme studies the spatial dynamics of reactor TESI, in the two group and one space dimension approximation. Only one group of delayed neutrons is considered. The programme simulates the vertical movement of the control rods according to any given movement law. The programme calculates the evolution of the fluxes and temperature and precursor concentration in space and time during the power excursion. 2 - Restrictions on the complexity of the problem: The maximum number of lattice points is 100
International Nuclear Information System (INIS)
Mansfeld, G.
1974-12-01
ZOCO VI is a computer code to investigate the time and space dependent pressure distribution in full pressure containment of water cooled nuclear power reactors following a loss-of-coolant accident, which is caused by the rupture of a main coolant or steam line. ZOCO VI is an improved version of the computer code ZOCO V with enlarged description of condensing events. (orig.) [de
Space and time dependent properties of the virtual cathode in a reflex-type pulsed ion diode
International Nuclear Information System (INIS)
Matsumoto, Yoshio; Kitamura, Akira; Yano, Syukuro
1981-01-01
Properties of a virtual cathode in a pulsed ion diode composed of and insulator-mesh anode and a metal-mesh cathode were studied experimentally at anode voltages below 35o kV. Potential distribution in the virtual cathode side was measured with an insulated electrostatic potential probe, and ion beam currents in virtual and real cathode sides were measured with biased ion collectors. Experimental results are given for the space and time behaviors of the anode plasma and the virtual cathode which starts to grow first from a region near a periphery of the metal anode frame and extends over the central region near the anode surface. A loss parameter for the electron current accompanied with the ion beam at the virtual cathode was evaluated from the measured electron current values by using relations derived from the one-dimensional Child-Langmuir theory applied to the reflex triode. The ion beam accompanies a considerable amount of electron current, and this influences the stability of the virtual cathode; this perturbation results in variations of ion current with time. Experimental results for space potentials in the emitted ion beam and the total current flowing in the space of the virtual cathode side are also given, suggesting an existence of high energy electrons of several keV accelerated by positive space potential of the ion beam. (author)
The functional half-life of an mRNA depends on the ribosome spacing in an early coding region
DEFF Research Database (Denmark)
Pedersen, Margit; Nissen, Søren; Mitarai, Namiko
2011-01-01
Bacterial mRNAs are translated by closely spaced ribosomes and degraded from the 5'-end, with half-lives of around 2 min at 37 °C in most cases. Ribosome-free or "naked" mRNA is known to be readily degraded, but the initial event that inactivates the mRNA functionally has not been fully described...
Shallow cumuli ensemble statistics for development of a stochastic parameterization
Sakradzija, Mirjana; Seifert, Axel; Heus, Thijs
2014-05-01
According to a conventional deterministic approach to the parameterization of moist convection in numerical atmospheric models, a given large scale forcing produces an unique response from the unresolved convective processes. This representation leaves out the small-scale variability of convection, as it is known from the empirical studies of deep and shallow convective cloud ensembles, there is a whole distribution of sub-grid states corresponding to the given large scale forcing. Moreover, this distribution gets broader with the increasing model resolution. This behavior is also consistent with our theoretical understanding of a coarse-grained nonlinear system. We propose an approach to represent the variability of the unresolved shallow-convective states, including the dependence of the sub-grid states distribution spread and shape on the model horizontal resolution. Starting from the Gibbs canonical ensemble theory, Craig and Cohen (2006) developed a theory for the fluctuations in a deep convective ensemble. The micro-states of a deep convective cloud ensemble are characterized by the cloud-base mass flux, which, according to the theory, is exponentially distributed (Boltzmann distribution). Following their work, we study the shallow cumulus ensemble statistics and the distribution of the cloud-base mass flux. We employ a Large-Eddy Simulation model (LES) and a cloud tracking algorithm, followed by a conditional sampling of clouds at the cloud base level, to retrieve the information about the individual cloud life cycles and the cloud ensemble as a whole. In the case of shallow cumulus cloud ensemble, the distribution of micro-states is a generalized exponential distribution. Based on the empirical and theoretical findings, a stochastic model has been developed to simulate the shallow convective cloud ensemble and to test the convective ensemble theory. Stochastic model simulates a compound random process, with the number of convective elements drawn from a
Trembach, Vera
2014-01-01
Space is an introduction to the mysteries of the Universe. Included are Task Cards for independent learning, Journal Word Cards for creative writing, and Hands-On Activities for reinforcing skills in Math and Language Arts. Space is a perfect introduction to further research of the Solar System.
Non-local PDEs with discrete state-dependent delays: Well-posedness in a metric space
Czech Academy of Sciences Publication Activity Database
Rezunenko, Oleksandr; Zagalak, Petr
2013-01-01
Roč. 33, č. 2 (2013), s. 819-835 ISSN 1078-0947 R&D Projects: GA ČR(CZ) GAP103/12/2431 Institutional support: RVO:67985556 Keywords : Partial differential equations with delay s * well-posedness * metric space Subject RIV: BC - Control Systems Theory Impact factor: 0.923, year: 2013 http://library.utia.cas.cz/separaty/2012/AS/zagalak-0381969.pdf
Coello, Yann; Quesque, François; Gigliotti, Maria-Francesca; Ott, Laurent; Bruyelle, Jean-Luc
2018-01-01
decreased amplitude of manual reaching actions was accompanied by an increase of peripersonal space representation, which was not due to the mere presence of a confederate (control experiment). We conclude that reward-dependent modulation of objects values in the environment modifies the representation of peripersonal space, when resulting from either self-generated motor actions or observation of motor actions performed by a confederate.
Model parameterization as method for data analysis in dendroecology
Tychkov, Ivan; Shishov, Vladimir; Popkova, Margarita
2017-04-01
There is no argue in usefulness of process-based models in ecological studies. Only limitations is how developed algorithm of model and how it will be applied for research. Simulation of tree-ring growth based on climate provides valuable information of tree-ring growth response on different environmental conditions, but also shares light on species-specifics of tree-ring growth process. Visual parameterization of the Vaganov-Shashkin model, allows to estimate non-linear response of tree-ring growth based on daily climate data: daily temperature, estimated day light and soil moisture. Previous using of the VS-Oscilloscope (a software tool of the visual parameterization) shows a good ability to recreate unique patterns of tree-ring growth for coniferous species in Siberian Russia, USA, China, Mediterranean Spain and Tunisia. But using of the models mostly is one-sided to better understand different tree growth processes, opposite to statistical methods of analysis (e.g. Generalized Linear Models, Mixed Models, Structural Equations.) which can be used for reconstruction and forecast. Usually the models are used either for checking of new hypothesis or quantitative assessment of physiological tree growth data to reveal a growth process mechanisms, while statistical methods used for data mining assessment and as a study tool itself. The high sensitivity of the model's VS-parameters reflects the ability of the model to simulate tree-ring growth and evaluates value of limiting growth climate factors. Precise parameterization of VS-Oscilloscope provides valuable information about growth processes of trees and under what conditions these processes occur (e.g. day of growth season onset, length of season, value of minimal/maximum temperature for tree-ring growth, formation of wide or narrow rings etc.). The work was supported by the Russian Science Foundation (RSF # 14-14-00219)
Systematic Parameterization of Lignin for the CHARMM Force Field
Energy Technology Data Exchange (ETDEWEB)
Vermaas, Joshua; Petridis, Loukas; Beckham, Gregg; Crowley, Michael
2017-07-06
Plant cell walls have three primary components, cellulose, hemicellulose, and lignin, the latter of which is a recalcitrant, aromatic heteropolymer that provides structure to plants, water and nutrient transport through plant tissues, and a highly effective defense against pathogens. Overcoming the recalcitrance of lignin is key to effective biomass deconstruction, which would in turn enable the use of biomass as a feedstock for industrial processes. Our understanding of lignin structure in the plant cell wall is hampered by the limitations of the available lignin forcefields, which currently only account for a single linkage between lignins and lack explicit parameterization for emerging lignin structures both from natural variants and engineered lignin structures. Since polymerization of lignin occurs via radical intermediates, multiple C-O and C-C linkages have been isolated , and the current force field only represents a small subset of lignin the diverse lignin structures found in plants. In order to take into account the wide range of lignin polymerization chemistries, monomers and dimer combinations of C-, H-, G-, and S-lignins as well as with hydroxycinnamic acid linkages were subjected to extensive quantum mechanical calculations to establish target data from which to build a complete molecular mechanics force field tuned specifically for diverse lignins. This was carried out in a GPU-accelerated global optimization process, whereby all molecules were parameterized simultaneously using the same internal parameter set. By parameterizing lignin specifically, we are able to more accurately represent the interactions and conformations of lignin monomers and dimers relative to a general force field. This new force field will enables computational researchers to study the effects of different linkages on the structure of lignin, as well as construct more accurate plant cell wall models based on observed statistical distributions of lignin that differ between
Multisite Evaluation of APEX for Water Quality: II. Regional Parameterization.
Nelson, Nathan O; Baffaut, Claire; Lory, John A; Anomaa Senaviratne, G M M M; Bhandari, Ammar B; Udawatta, Ranjith P; Sweeney, Daniel W; Helmers, Matt J; Van Liew, Mike W; Mallarino, Antonio P; Wortmann, Charles S
2017-11-01
Phosphorus (P) Index assessment requires independent estimates of long-term average annual P loss from fields, representing multiple climatic scenarios, management practices, and landscape positions. Because currently available measured data are insufficient to evaluate P Index performance, calibrated and validated process-based models have been proposed as tools to generate the required data. The objectives of this research were to develop a regional parameterization for the Agricultural Policy Environmental eXtender (APEX) model to estimate edge-of-field runoff, sediment, and P losses in restricted-layer soils of Missouri and Kansas and to assess the performance of this parameterization using monitoring data from multiple sites in this region. Five site-specific calibrated models (SSCM) from within the region were used to develop a regionally calibrated model (RCM), which was further calibrated and validated with measured data. Performance of the RCM was similar to that of the SSCMs for runoff simulation and had Nash-Sutcliffe efficiency (NSE) > 0.72 and absolute percent bias (|PBIAS|) 90%) and was particularly ineffective at simulating sediment loss from locations with small sediment loads. The RCM had acceptable performance for simulation of total P loss (NSE > 0.74, |PBIAS| < 30%) but underperformed the SSCMs. Total P-loss estimates should be used with caution due to poor simulation of sediment loss. Although we did not attain our goal of a robust regional parameterization of APEX for estimating sediment and total P losses, runoff estimates with the RCM were acceptable for P Index evaluation. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.
Burgess, K. D.; Stroud, R. M.
2018-03-01
The solar wind is an important driver of space weathering on airless bodies. Over time, solar wind exposure alters the physical, chemical, and optical properties of exposed materials and can also impart a significant amount of helium into the surfaces of these bodies. However, common materials on the surface of the Moon, such as glass, crystalline silicates, and oxides, have highly variable responses to solar wind irradiation. We used scanning transmission electron microscopy (STEM) with electron energy loss spectroscopy (EELS) to examine the morphology and chemistry of a single grain of lunar soil that includes silicate glass, chromite and ilmenite, all present and exposed along the same surface. The exposure of the silicate glass and oxides to the same space weathering conditions allows for direct comparisons of the responses of natural materials to the complex lunar surface environment. The silicate glass shows minimal effects of solar wind irradiation, whereas both the chromite and ilmenite exhibit defect-rich rims that currently contain trapped helium. Only the weathered rim in ilmenite is rich in nanophase metallic iron (npFe0) and larger vesicles that retain helium at a range of internal pressures. The multiple exposed surfaces of the single grain of ilmenite demonstrate strong crystallographic controls of planar defects and non-spherical npFe0. The direct spectroscopic identification of helium in the vesicles and planar defects in the oxides provides additional evidence of the central role of solar wind irradiation in the formation of some common space weathering features.
Parameterization models for solar radiation and solar technology applications
International Nuclear Information System (INIS)
Khalil, Samy A.
2008-01-01
Solar radiation is very important for the evaluation and wide use of solar renewable energy systems. The development of calibration procedures for broadband solar radiation photometric instrumentation and the improvement of broadband solar radiation measurement accuracy have been done. An improved diffuse sky reference and photometric calibration and characterization software for outdoor pyranometer calibrations are outlined. Parameterizations for direct beam, total hemispherical and diffuse sky radiation and solar radiation technology are briefly reviewed. The uncertainties for various broadband solar radiations of solar energy and atmospheric effects are discussed. The varying responsivities of solar radiation with meteorological, statistical and climatological parameters and possibility atmospheric conditions was examined
Parameterization models for solar radiation and solar technology applications
Energy Technology Data Exchange (ETDEWEB)
Khalil, Samy A. [National Research Institute of Astronomy and Geophysics, Solar and Space Department, Marsed Street, Helwan, 11421 Cairo (Egypt)
2008-08-15
Solar radiation is very important for the evaluation and wide use of solar renewable energy systems. The development of calibration procedures for broadband solar radiation photometric instrumentation and the improvement of broadband solar radiation measurement accuracy have been done. An improved diffuse sky reference and photometric calibration and characterization software for outdoor pyranometer calibrations are outlined. Parameterizations for direct beam, total hemispherical and diffuse sky radiation and solar radiation technology are briefly reviewed. The uncertainties for various broadband solar radiations of solar energy and atmospheric effects are discussed. The varying responsivities of solar radiation with meteorological, statistical and climatological parameters and possibility atmospheric conditions was examined. (author)
Parameterization of the dielectric function of semiconductor nanocrystals
Energy Technology Data Exchange (ETDEWEB)
Petrik, P., E-mail: petrik@mfa.kfki.hu
2014-11-15
Optical methods like spectroscopic ellipsometry are sensitive to the structural properties of semiconductor films such as crystallinity or grain size. The imaginary part of the dielectric function is proportional to the joint density of electronic states. Consequently, the analysis of the dielectric function around the critical point energies provides useful information about the electron band structure and all related parameters like the grain structure, band gap, temperature, composition, phase structure, and carrier mobility. In this work an attempt is made to present a selection of the approaches to parameterize and analyze the dielectric function of semiconductors, as well as some applications.
IR Optics Measurement with Linear Coupling's Action-Angle Parameterization
Luo, Yun; Pilat, Fulvia Caterina; Satogata, Todd; Trbojevic, Dejan
2005-01-01
The interaction region (IP) optics are measured with the two DX/BPMs close to the IPs at the Relativistic Heavy Ion Collider (RHIC). The beta functions at IP are measured with the two eigenmodes' phase advances between the two BPMs. And the beta waists are also determined through the beta functions at the two BPMs. The coupling parameters at the IPs are also given through the linear coupling's action-angle parameterization. All the experimental data are taken during the driving oscillations with the AC dipole. The methods to do these measurements are discussed. And the measurement results during the beta*
Parameterization of interatomic potential by genetic algorithms: A case study
Energy Technology Data Exchange (ETDEWEB)
Ghosh, Partha S., E-mail: psghosh@barc.gov.in; Arya, A.; Dey, G. K. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai-400085 (India); Ranawat, Y. S. [Department of Ceramic Engineering, Indian Institute of Technology (BHU), Varanasi-221005 (India)
2015-06-24
A framework for Genetic Algorithm based methodology is developed to systematically obtain and optimize parameters for interatomic force field functions for MD simulations by fitting to a reference data base. This methodology is applied to the fitting of ThO{sub 2} (CaF{sub 2} prototype) – a representative of ceramic based potential fuel for nuclear applications. The resulting GA optimized parameterization of ThO{sub 2} is able to capture basic structural, mechanical, thermo-physical properties and also describes defect structures within the permissible range.
Gao, Yang; Leung, L. Ruby; Zhao, Chun; Hagos, Samson
2017-03-01
Simulating summer precipitation is a significant challenge for climate models that rely on cumulus parameterizations to represent moist convection processes. Motivated by recent advances in computing that support very high-resolution modeling, this study aims to systematically evaluate the effects of model resolution and convective parameterizations across the gray zone resolutions. Simulations using the Weather Research and Forecasting model were conducted at grid spacings of 36 km, 12 km, and 4 km for two summers over the conterminous U.S. The convection-permitting simulations at 4 km grid spacing are most skillful in reproducing the observed precipitation spatial distributions and diurnal variability. Notable differences are found between simulations with the traditional Kain-Fritsch (KF) and the scale-aware Grell-Freitas (GF) convection schemes, with the latter more skillful in capturing the nocturnal timing in the Great Plains and North American monsoon regions. The GF scheme also simulates a smoother transition from convective to large-scale precipitation as resolution increases, resulting in reduced sensitivity to model resolution compared to the KF scheme. Nonhydrostatic dynamics has a positive impact on precipitation over complex terrain even at 12 km and 36 km grid spacings. With nudging of the winds toward observations, we show that the conspicuous warm biases in the Southern Great Plains are related to precipitation biases induced by large-scale circulation biases, which are insensitive to model resolution. Overall, notable improvements in simulating summer rainfall and its diurnal variability through convection-permitting modeling and scale-aware parameterizations suggest promising venues for improving climate simulations of water cycle processes.
Parameterization and evaluation of sulfate adsorption in a dynamic soil chemistry model
International Nuclear Information System (INIS)
Martinson, Liisa; Alveteg, Mattias; Warfvinge, Per
2003-01-01
Including sulfate adsorption improves the dynamic behavior of the SAFE model. - Sulfate adsorption was implemented in the dynamic, multi-layer soil chemistry model SAFE. The process is modeled by an isotherm in which sulfate adsorption is considered to be fully reversible and dependent on sulfate concentration as well as pH in soil solution. The isotherm was parameterized by a site-specific series of simple batch experiments at different pH (3.8-5.0) and sulfate concentration (10-260 μmol l -1 ) levels. Application of the model to the Lake Gaardsjoen roof covered site shows that including sulfate adsorption improves the dynamic behavior of the model and sulfate adsorption and desorption delay acidification and recovery of the soil. The modeled adsorbed pool of sulfate at the site reached a maximum level of 700 mmol/m 2 in the late 1980s, well in line with experimental data
Benilov, E. S.
2018-05-01
This paper examines quasigeostrophic flows in an ocean that can be subdivided into an upper active layer (AL) and a lower passive layer (PL), with the flow and density stratification mainly confined to the former. Under this assumption, an asymptotic model is derived parameterizing the effect of the PL on the AL. The model depends only on the PL's depth, whereas its Väisälä-Brunt frequency turns out to be unimportant (as long as it is small). Under an additional assumption-that the potential vorticity field in the PL is well-diffused and, thus, uniform-the derived model reduces to a simple boundary condition. This condition is to be applied at the AL/PL interface, after which the PL can be excluded from consideration.
The Markov chain method for solving dead time problems in the space dependent model of reactor noise
International Nuclear Information System (INIS)
Degweker, S.B.
1997-01-01
The discrete time Markov chain approach for deriving the statistics of time-correlated pulses, in the presence of a non-extending dead time, is extended to include the effect of space energy distribution of the neutron field. Equations for the singlet and doublet densities of follower neutrons are derived by neglecting correlations beyond the second order. These equations are solved by the modal method. It is shown that in the unimodal approximation, the equations reduce to the point model equations with suitably defined parameters. (author)
Energy Technology Data Exchange (ETDEWEB)
Parsons, Taylor; Guo, Yi; Veers, Paul; Dykes, Katherine; Damiani, Rick
2016-01-26
Software models that use design-level input variables and physics-based engineering analysis for estimating the mass and geometrical properties of components in large-scale machinery can be very useful for analyzing design trade-offs in complex systems. This study uses DriveSE, an OpenMDAO-based drivetrain model that uses stress and deflection criteria to size drivetrain components within a geared, upwind wind turbine. Because a full lifetime fatigue load spectrum can only be defined using computationally-expensive simulations in programs such as FAST, a parameterized fatigue loads spectrum that depends on wind conditions, rotor diameter, and turbine design life has been implemented. The parameterized fatigue spectrum is only used in this paper to demonstrate the proposed fatigue analysis approach. This paper details a three-part investigation of the parameterized approach and a comparison of the DriveSE model with and without fatigue analysis on the main shaft system. It compares loads from three turbines of varying size and determines if and when fatigue governs drivetrain sizing compared to extreme load-driven design. It also investigates the model's sensitivity to shaft material parameters. The intent of this paper is to demonstrate how fatigue considerations in addition to extreme loads can be brought into a system engineering optimization.
Directory of Open Access Journals (Sweden)
Mikkel Brydegaard
Full Text Available In recent years, the field of remote sensing of birds and insects in the atmosphere (the aerial fauna has advanced considerably, and modern electro-optic methods now allow the assessment of the abundance and fluxes of pests and beneficials on a landscape scale. These techniques have the potential to significantly increase our understanding of, and ability to quantify and manage, the ecological environment. This paper presents a concept whereby laser radar observations of atmospheric fauna can be parameterized and table values for absolute cross sections can be catalogued to allow for the study of focal species such as disease vectors and pests. Wing-beat oscillations are parameterized with a discrete set of harmonics and the spherical scatter function is parameterized by a reduced set of symmetrical spherical harmonics. A first order spherical model for insect scatter is presented and supported experimentally, showing angular dependence of wing beat harmonic content. The presented method promises to give insights into the flight heading directions of species in the atmosphere and has the potential to shed light onto the km-range spread of pests and disease vectors.
The parameterization of microchannel-plate-based detection systems
Gershman, Daniel J.; Gliese, Ulrik; Dorelli, John C.; Avanov, Levon A.; Barrie, Alexander C.; Chornay, Dennis J.; MacDonald, Elizabeth A.; Holland, Matthew P.; Giles, Barbara L.; Pollock, Craig J.
2016-10-01
The most common instrument for low-energy plasmas consists of a top-hat electrostatic analyzer (ESA) geometry coupled with a microchannel-plate-based (MCP-based) detection system. While the electrostatic optics for such sensors are readily simulated and parameterized during the laboratory calibration process, the detection system is often less well characterized. Here we develop a comprehensive mathematical description of particle detection systems. As a function of instrument azimuthal angle, we parameterize (1) particle scattering within the ESA and at the surface of the MCP, (2) the probability distribution of MCP gain for an incident particle, (3) electron charge cloud spreading between the MCP and anode board, and (4) capacitive coupling between adjacent discrete anodes. Using the Dual Electron Spectrometers on the Fast Plasma Investigation on NASA's Magnetospheric Multiscale mission as an example, we demonstrate a method for extracting these fundamental detection system parameters from laboratory calibration. We further show that parameters that will evolve in flight, namely, MCP gain, can be determined through application of this model to specifically tailored in-flight calibration activities. This methodology provides a robust characterization of sensor suite performance throughout mission lifetime. The model developed in this work is not only applicable to existing sensors but also can be used as an analytical design tool for future particle instrumentation.
Further study on parameterization of reactor NAA: Pt. 2
International Nuclear Information System (INIS)
Tian Weizhi; Zhang Shuxin
1989-01-01
In the last paper, Ik 0 method was proposed for fission interference corrections. Another important kind of interferences in reator NAA is due to threshold reaction induced by reactor fast neutrons. In view of the increasing importance of this kind of interferences, and difficulties encountered in using the relative comparison method, a parameterized method has been introduced. Typical channels in heavy water reflector and No.2 horizontal channel of Heavy Water Research Reactor in the Insitute of Atomic Energy have been shown to have fast neutron energy distributions (E>4 MeV) close to primary fission neutron spectrum, by using multi-threshold detectors. On this basis, Ti foil is used as an 'instant fast neutron flux monitor' in parameterized corrections for threshold reaction interferences in the long irradiations. Constant values of φ f /φ s = 0.70 ± 0.02% have been obtained for No.2 rabbit channel. This value can be directly used for threshold reaction inference correction in the short irradiations
Improving microphysics in a convective parameterization: possibilities and limitations
Labbouz, Laurent; Heikenfeld, Max; Stier, Philip; Morrison, Hugh; Milbrandt, Jason; Protat, Alain; Kipling, Zak
2017-04-01
The convective cloud field model (CCFM) is a convective parameterization implemented in the climate model ECHAM6.1-HAM2.2. It represents a population of clouds within each ECHAM-HAM model column, simulating up to 10 different convective cloud types with individual radius, vertical velocities and microphysical properties. Comparisons between CCFM and radar data at Darwin, Australia, show that in order to reproduce both the convective cloud top height distribution and the vertical velocity profile, the effect of aerodynamic drag on the rising parcel has to be considered, along with a reduced entrainment parameter. A new double-moment microphysics (the Predicted Particle Properties scheme, P3) has been implemented in the latest version of CCFM and is compared to the standard single-moment microphysics and the radar retrievals at Darwin. The microphysical process rates (autoconversion, accretion, deposition, freezing, …) and their response to changes in CDNC are investigated and compared to high resolution CRM WRF simulations over the Amazon region. The results shed light on the possibilities and limitations of microphysics improvements in the framework of CCFM and in convective parameterizations in general.
Rapid parameterization of small molecules using the Force Field Toolkit.
Mayne, Christopher G; Saam, Jan; Schulten, Klaus; Tajkhorshid, Emad; Gumbart, James C
2013-12-15
The inability to rapidly generate accurate and robust parameters for novel chemical matter continues to severely limit the application of molecular dynamics simulations to many biological systems of interest, especially in fields such as drug discovery. Although the release of generalized versions of common classical force fields, for example, General Amber Force Field and CHARMM General Force Field, have posited guidelines for parameterization of small molecules, many technical challenges remain that have hampered their wide-scale extension. The Force Field Toolkit (ffTK), described herein, minimizes common barriers to ligand parameterization through algorithm and method development, automation of tedious and error-prone tasks, and graphical user interface design. Distributed as a VMD plugin, ffTK facilitates the traversal of a clear and organized workflow resulting in a complete set of CHARMM-compatible parameters. A variety of tools are provided to generate quantum mechanical target data, setup multidimensional optimization routines, and analyze parameter performance. Parameters developed for a small test set of molecules using ffTK were comparable to existing CGenFF parameters in their ability to reproduce experimentally measured values for pure-solvent properties (<15% error from experiment) and free energy of solvation (±0.5 kcal/mol from experiment). Copyright © 2013 Wiley Periodicals, Inc.
Astitha, M.; Abdel Kader, M.; Pozzer, A.; Lelieveld, J.
2012-04-01
Atmospheric particulate matter and more specific desert dust has been the topic of numerous research studies in the past due to the wide range of impacts in the environment and climate and the uncertainty of characterizing and quantifying these impacts in a global scale. In this work we present two physical parameterizations of the desert dust production that have been incorporated in the atmospheric chemistry general circulation model EMAC (ECHAM5/MESSy2.41 Atmospheric Chemistry). The scope of this work is to assess the impact of the two physical parameterizations in the global distribution of desert dust and highlight the advantages and disadvantages of using either technique. The dust concentration and deposition has been evaluated using the AEROCOM dust dataset for the year 2000 and data from the MODIS and MISR satellites as well as sun-photometer data from the AERONET network was used to compare the modelled aerosol optical depth with observations. The implementation of the two parameterizations and the simulations using relatively high spatial resolution (T106~1.1deg) has highlighted the large spatial heterogeneity of the dust emission sources as well as the importance of the input parameters (soil size and texture, vegetation, surface wind speed). Also, sensitivity simulations with the nudging option using reanalysis data from ECMWF and without nudging have showed remarkable differences for some areas. Both parameterizations have revealed the difficulty of simulating all arid regions with the same assumptions and mechanisms. Depending on the arid region, each emission scheme performs more or less satisfactorily which leads to the necessity of treating each desert differently. Even though this is a quite different task to accomplish in a global model, some recommendations are given and ideas for future improvements.
International Nuclear Information System (INIS)
Lu, P.C.
1977-01-01
The use of intense ion beams as a heating source for the fusion reaction in pellets of D-T appears to have several potential advantages over the use of electron beams. If ion bunching can be accomplished, then existing technology can be used to achieve the required power, energy and time scales for pellet fusion. A scheme to be considered is that of a pre-formed nonuniform plasma adjacent to a partially transparent anode through which a space charge limited electron beam is injected from the terminals of a convergent spherical geometry with a finite (or zero) rise-time. At the instant of beam injection, the virtual cathode is formed. Due to the space charge fields set up by the beam, the plasma ions are accelerated towards the region beyond the virtual cathode. A self-consistent transient analysis of the interactions between the electron beam and the background plasma is performed. The numerical calculations show that by specifying the target plasma for perfect bunching the ions can be made to bunch nearly perfectly. Also, by considering the depletion of initial plasma and accounting for the fact that the virtual anode-virtual cathode gap region is moving opposite to the direction of the ions, one can considerably enhance the instantaneous power delivered to the target over that which is injected at the terminals of the device, even with a finite rise-time on the current pulse
DOT-IV two-dimensional discrete ordinates transport code with space-dependent mesh and quadrature
International Nuclear Information System (INIS)
Rhoades, W.A.; Simpson, D.B.; Childs, R.L.; Engle, W.W. Jr.
1979-01-01
DOT IV is designed to allow very large problems to be solved on a wide range of computers and memory arrangements. New flexibility in both space-mesh and directional-quadrature specification is allowed. For example, the radial mesh in an R-Z problem can vary with axial position. The directional quadrature can vary with both space and energy group. Several features improve performance on both deep penetration and criticality problems. The program has been checked and used extensively on several types of computers. All of the features have been insured operable except the following two, which must not be used: criticality searches and P/sub L/ variable by group or material. Diffusion theory problems must not use internal or external boundary sources, variable mesh, or variable quadrature. A diffusion iteration cannot produce internal boundary source output or ''angular flux tape.'' The P 1 module is very limited. The special geometries, INGEOM greater than or equal to 10, have not been completely checked and are not guaranteed. 7 figures, 1 table
The metric on field space, functional renormalization, and metric–torsion quantum gravity
International Nuclear Information System (INIS)
Reuter, Martin; Schollmeyer, Gregor M.
2016-01-01
Searching for new non-perturbatively renormalizable quantum gravity theories, functional renormalization group (RG) flows are studied on a theory space of action functionals depending on the metric and the torsion tensor, the latter parameterized by three irreducible component fields. A detailed comparison with Quantum Einstein–Cartan Gravity (QECG), Quantum Einstein Gravity (QEG), and “tetrad-only” gravity, all based on different theory spaces, is performed. It is demonstrated that, over a generic theory space, the construction of a functional RG equation (FRGE) for the effective average action requires the specification of a metric on the infinite-dimensional field manifold as an additional input. A modified FRGE is obtained if this metric is scale-dependent, as it happens in the metric–torsion system considered.
Directory of Open Access Journals (Sweden)
J.-I. Yano
2012-11-01
Full Text Available A generalized mass-flux formulation is presented, which no longer takes a limit of vanishing fractional areas for subgrid-scale components. The presented formulation is applicable to a~situation in which the scale separation is still satisfied, but fractional areas occupied by individual subgrid-scale components are no longer small. A self-consistent formulation is presented by generalizing the mass-flux formulation under the segmentally-constant approximation (SCA to the grid–scale variabilities. The present formulation is expected to alleviate problems arising from increasing resolutions of operational forecast models without invoking more extensive overhaul of parameterizations.
The present formulation leads to an analogy of the large-scale atmospheric flow with multi-component flows. This analogy allows a generality of including any subgrid-scale variability into the mass-flux parameterization under SCA. Those include stratiform clouds as well as cold pools in the boundary layer.
An important finding under the present formulation is that the subgrid-scale quantities are advected by the large-scale velocities characteristic of given subgrid-scale components (large-scale subcomponent flows, rather than by the total large-scale flows as simply defined by grid-box average. In this manner, each subgrid-scale component behaves as if like a component of multi-component flows. This formulation, as a result, ensures the lateral interaction of subgrid-scale variability crossing the grid boxes, which are missing in the current parameterizations based on vertical one-dimensional models, and leading to a reduction of the grid-size dependencies in its performance. It is shown that the large-scale subcomponent flows are driven by large-scale subcomponent pressure gradients. The formulation, as a result, furthermore includes a self-contained description of subgrid-scale momentum transport.
The main purpose of the present paper
Capturing the Interplay of Dynamics and Networks through Parameterizations of Laplacian Operators
2016-08-24
we describe an umbrella framework that unifies some of the well known measures, connecting the ideas of centrality , communities and dynamical processes...change of basis. Parameterized centrality also leads to the definition of parameterized volume for subsets of vertices. Parameterized conductance...behind this definition is to establish a direct connection between centrality and community measures, as we will later demonstrate with the notion of
A Coordinated Effort to Improve Parameterization of High-Latitude Cloud and Radiation Processes
International Nuclear Information System (INIS)
J. O. Pinto; A.H. Lynch
2004-01-01
The goal of this project is the development and evaluation of improved parameterization of arctic cloud and radiation processes and implementation of the parameterizations into a climate model. Our research focuses specifically on the following issues: (1) continued development and evaluation of cloud microphysical parameterizations, focusing on issues of particular relevance for mixed phase clouds; and (2) evaluation of the mesoscale simulation of arctic cloud system life cycles
International Nuclear Information System (INIS)
Maharjan, C M; Alnaser, A S; Litvinyuk, I; Ranitovic, P; Cocke, C L
2006-01-01
We have measured momentum-space images of low-energy electrons generated by the interaction of short intense laser pulses with argon atoms at high intensities. We have done this over a wavelength range from 400 to 800 nm. The spectra show considerable structure in both the energy and angular distributions of the electrons. Some, but not all, energy features can be identified as multi-photon resonances. The angular structure shows a regularity which transcends the resonant structure and may be due instead to diffraction. The complexity of the results defies easy model-dependent interpretations and invites full solutions to Schroedinger's equation for these systems
ANALYSIS OF PARAMETERIZATION VALUE REDUCTION OF SOFT SETS AND ITS ALGORITHM
Directory of Open Access Journals (Sweden)
Mohammed Adam Taheir Mohammed
2016-02-01
Full Text Available In this paper, the parameterization value reduction of soft sets and its algorithm in decision making are studied and described. It is based on parameterization reduction of soft sets. The purpose of this study is to investigate the inherited disadvantages of parameterization reduction of soft sets and its algorithm. The algorithms presented in this study attempt to reduce the value of least parameters from soft set. Through the analysis, two techniques have been described. Through this study, it is found that parameterization reduction of soft sets and its algorithm has yielded a different and inconsistency in suboptimal result.
Mahanthesh, B.; Gireesha, B. J.; Shashikumar, N. S.; Hayat, T.; Alsaedi, A.
2018-06-01
Present work aims to investigate the features of the exponential space dependent heat source (ESHS) and cross-diffusion effects in Marangoni convective heat mass transfer flow due to an infinite disk. Flow analysis is comprised with magnetohydrodynamics (MHD). The effects of Joule heating, viscous dissipation and solar radiation are also utilized. The thermal and solute field on the disk surface varies in a quadratic manner. The ordinary differential equations have been obtained by utilizing Von Kármán transformations. The resulting problem under consideration is solved numerically via Runge-Kutta-Fehlberg based shooting scheme. The effects of involved pertinent flow parameters are explored by graphical illustrations. Results point out that the ESHS effect dominates thermal dependent heat source effect on thermal boundary layer growth. The concentration and temperature distributions and their associated layer thicknesses are enhanced by Marangoni effect.
Parameterizing Urban Canopy Layer transport in an Lagrangian Particle Dispersion Model
Stöckl, Stefan; Rotach, Mathias W.
2016-04-01
The percentage of people living in urban areas is rising worldwide, crossed 50% in 2007 and is even higher in developed countries. High population density and numerous sources of air pollution in close proximity can lead to health issues. Therefore it is important to understand the nature of urban pollutant dispersion. In the last decades this field has experienced considerable progress, however the influence of large roughness elements is complex and has as of yet not been completely described. Hence, this work studied urban particle dispersion close to source and ground. It used an existing, steady state, three-dimensional Lagrangian particle dispersion model, which includes Roughness Sublayer parameterizations of turbulence and flow. The model is valid for convective and neutral to stable conditions and uses the kernel method for concentration calculation. As most Lagrangian models, its lower boundary is the zero-plane displacement, which means that roughly the lower two-thirds of the mean building height are not included in the model. This missing layer roughly coincides with the Urban Canopy Layer. An earlier work "traps" particles hitting the lower model boundary for a recirculation period, which is calculated under the assumption of a vortex in skimming flow, before "releasing" them again. The authors hypothesize that improving the lower boundary condition by including Urban Canopy Layer transport could improve model predictions. This was tested herein by not only trapping the particles, but also advecting them with a mean, parameterized flow in the Urban Canopy Layer. Now the model calculates the trapping period based on either recirculation due to vortex motion in skimming flow regimes or vertical velocity if no vortex forms, depending on incidence angle of the wind on a randomly chosen street canyon. The influence of this modification, as well as the model's sensitivity to parameterization constants, was investigated. To reach this goal, the model was
Improving Mixed-phase Cloud Parameterization in Climate Model with the ACRF Measurements
Energy Technology Data Exchange (ETDEWEB)
Wang, Zhien [Univ. of Wyoming, Laramie, WY (United States)
2016-12-13
Mixed-phase cloud microphysical and dynamical processes are still poorly understood, and their representation in GCMs is a major source of uncertainties in overall cloud feedback in GCMs. Thus improving mixed-phase cloud parameterizations in climate models is critical to reducing the climate forecast uncertainties. This study aims at providing improved knowledge of mixed-phase cloud properties from the long-term ACRF observations and improving mixed-phase clouds simulations in the NCAR Community Atmosphere Model version 5 (CAM5). The key accomplishments are: 1) An improved retrieval algorithm was developed to provide liquid droplet concentration for drizzling or mixed-phase stratiform clouds. 2) A new ice concentration retrieval algorithm for stratiform mixed-phase clouds was developed. 3) A strong seasonal aerosol impact on ice generation in Arctic mixed-phase clouds was identified, which is mainly attributed to the high dust occurrence during the spring season. 4) A suite of multi-senor algorithms was applied to long-term ARM observations at the Barrow site to provide a complete dataset (LWC and effective radius profile for liquid phase, and IWC, Dge profiles and ice concentration for ice phase) to characterize Arctic stratiform mixed-phase clouds. This multi-year stratiform mixed-phase cloud dataset provides necessary information to study related processes, evaluate model stratiform mixed-phase cloud simulations, and improve model stratiform mixed-phase cloud parameterization. 5). A new in situ data analysis method was developed to quantify liquid mass partition in convective mixed-phase clouds. For the first time, we reliably compared liquid mass partitions in stratiform and convective mixed-phase clouds. Due to the different dynamics in stratiform and convective mixed-phase clouds, the temperature dependencies of liquid mass partitions are significantly different due to much higher ice concentrations in convective mixed phase clouds. 6) Systematic evaluations
Energy Technology Data Exchange (ETDEWEB)
Obradovic, D; Petrovic, M [Institute of nuclear sciences Boris Kidric, Vinca, Beograd (Yugoslavia)
1966-11-15
This paper describes experimental study of space-time behaviour of nuclear reactors by local complex-periodic perturbation of the absorption cross section and by measuring the local reactor response to this perturbation. Perturbation was done by BOR-1 fast oscillator. Cross correlation between the response and the perturbation was done numerically after completing the measurement by using digital computer. Obtained experimental results are preliminary and are measured with significant errors which were analysed in this paper. Results show qualitative agreement with those obtained by theoretical model. This paper is the first progress report in this field in our country. U radu je opisan eksperimentalni prilaz proucavanju prostorno-vremenskog ponasanja nuklearnih reaktora, vrseci lokalnu slozeno-periodicnu perturbaciju apsorpcionog preseka i mereci lokalni odziv reaktora na tu perturbaciju. Perturbacija je vrsena brzim oscilatorom BOR-1. Kroskorelacija izmedju odziva i perturbacije vrsena je numericki posle obavljenog merenja upotrebom digitalne racunske masine. Dobijeni eksperimentalni rezultati imaju preliminarni karakter i odredjeni su sa znatnim eksperimentalnim greskama koje su, u radu analizirane. Izlozeni rezultati pokazuju kvalitativna slaganja sa teorijski dobijenim modelom. Ovaj rad predstavlja prvi izvestaj o napredovanju na ovoj problematici kod nas (author)
Energy Technology Data Exchange (ETDEWEB)
Robert Pincus
2011-05-17
This project focused on the variability of clouds that is present across a wide range of scales ranging from the synoptic to the millimeter. In particular, there is substantial variability in cloud properties at scales smaller than the grid spacing of models used to make climate projections (GCMs) and weather forecasts. These models represent clouds and other small-scale processes with parameterizations that describe how those processes respond to and feed back on the largescale state of the atmosphere.
Parameterization of ion channeling half-angles and minimum yields
Energy Technology Data Exchange (ETDEWEB)
Doyle, Barney L.
2016-03-15
A MS Excel program has been written that calculates ion channeling half-angles and minimum yields in cubic bcc, fcc and diamond lattice crystals. All of the tables and graphs in the three Ion Beam Analysis Handbooks that previously had to be manually looked up and read from were programed into Excel in handy lookup tables, or parameterized, for the case of the graphs, using rather simple exponential functions with different power functions of the arguments. The program then offers an extremely convenient way to calculate axial and planar half-angles, minimum yields, effects on half-angles and minimum yields of amorphous overlayers. The program can calculate these half-angles and minimum yields for 〈u v w〉 axes and [h k l] planes up to (5 5 5). The program is open source and available at (http://www.sandia.gov/pcnsc/departments/iba/ibatable.html).
A simple parameterization of aerosol emissions in RAMS
Letcher, Theodore
Throughout the past decade, a high degree of attention has been focused on determining the microphysical impact of anthropogenically enhanced concentrations of Cloud Condensation Nuclei (CCN) on orographic snowfall in the mountains of the western United States. This area has garnered a lot of attention due to the implications this effect may have on local water resource distribution within the Region. Recent advances in computing power and the development of highly advanced microphysical schemes within numerical models have provided an estimation of the sensitivity that orographic snowfall has to changes in atmospheric CCN concentrations. However, what is still lacking is a coupling between these advanced microphysical schemes and a real-world representation of CCN sources. Previously, an attempt to representation the heterogeneous evolution of aerosol was made by coupling three-dimensional aerosol output from the WRF Chemistry model to the Colorado State University (CSU) Regional Atmospheric Modeling System (RAMS) (Ward et al. 2011). The biggest problem associated with this scheme was the computational expense. In fact, the computational expense associated with this scheme was so high, that it was prohibitive for simulations with fine enough resolution to accurately represent microphysical processes. To improve upon this method, a new parameterization for aerosol emission was developed in such a way that it was fully contained within RAMS. Several assumptions went into generating a computationally efficient aerosol emissions parameterization in RAMS. The most notable assumption was the decision to neglect the chemical processes in formed in the formation of Secondary Aerosol (SA), and instead treat SA as primary aerosol via short-term WRF-CHEM simulations. While, SA makes up a substantial portion of the total aerosol burden (much of which is made up of organic material), the representation of this process is highly complex and highly expensive within a numerical
A stratiform cloud parameterization for General Circulation Models
International Nuclear Information System (INIS)
Ghan, S.J.; Leung, L.R.; Chuang, C.C.; Penner, J.E.; McCaa, J.
1994-01-01
The crude treatment of clouds in General Circulation Models (GCMs) is widely recognized as a major limitation in the application of these models to predictions of global climate change. The purpose of this project is to develop a paxameterization for stratiform clouds in GCMs that expresses stratiform clouds in terms of bulk microphysical properties and their subgrid variability. In this parameterization, precipitating cloud species are distinguished from non-precipitating species, and the liquid phase is distinguished from the ice phase. The size of the non-precipitating cloud particles (which influences both the cloud radiative properties and the conversion of non-precipitating cloud species to precipitating species) is determined by predicting both the mass and number concentrations of each species
A stratiform cloud parameterization for general circulation models
International Nuclear Information System (INIS)
Ghan, S.J.; Leung, L.R.; Chuang, C.C.; Penner, J.E.; McCaa, J.
1994-01-01
The crude treatment of clouds in general circulation models (GCMs) is widely recognized as a major limitation in applying these models to predictions of global climate change. The purpose of this project is to develop in GCMs a stratiform cloud parameterization that expresses clouds in terms of bulk microphysical properties and their subgrid variability. Various clouds variables and their interactions are summarized. Precipitating cloud species are distinguished from non-precipitating species, and the liquid phase is distinguished from the ice phase. The size of the non-precipitating cloud particles (which influences both the cloud radiative properties and the conversion of non-precipitating cloud species to precipitating species) is determined by predicting both the mass and number concentrations of each species
Sensitivity of tropical cyclone simulations to microphysics parameterizations in WRF
International Nuclear Information System (INIS)
Reshmi Mohan, P.; Srinivas, C.V.; Bhaskaran, R.; Venkatraman, B.; Yesubabu, V.
2018-01-01
Tropical cyclones (TC) cause storm surge along coastal areas where these storms cross the coast. As major nuclear facilities are usually installed in coastal region, the surge predictions are highly important for DAE. The critical TC parameters needed in estimating storm surge are intensity (winds, central pressure and radius of maximum winds) and storm tracks. The predictions with numerical models are generally made by representing the clouds and precipitation processes using convective and microphysics parameterization. At high spatial resolutions (1-3Km) microphysics can act as cloud resolving NWP model to explicitly resolve the convective precipitation without using convection schemes. Recent simulation studies using WRF on severe weather phenomena such as thunderstorms and hurricanes indicated large sensitivity of predicted rainfall and hurricane tracks to microphysics due to variation in temperature and pressure gradients which generate winds that determine the storm track. In the present study the sensitivity of tropical cyclone tracks and intensity to different microphysics schemes has been conducted
Relativistic quantum similarities in atoms in position and momentum spaces
International Nuclear Information System (INIS)
Maldonado, P.; Sarsa, A.; Buendia, E.; Galvez, F.J.
2011-01-01
A study of different quantum similarity measures and their corresponding quantum similarity indices is carried out for the atoms from H to Lr (Z=1-103). Relativistic effects in both position and momentum spaces have been studied by comparing the relativistic values to the non-relativistic ones. We have used the atomic electron density in both position and momentum spaces obtained within relativistic and non-relativistic numerical-parameterized optimized effective potential approximations. -- Highlights: → Quantum similarity measures and indices in electronic structure of atoms. → Position and momentum electronic densities. → Similarity of relativistic and non-relativistic densities. → Similarity of core and valence regions of different atoms. → Dependence with Z along the Periodic Table.
Examining Chaotic Convection with Super-Parameterization Ensembles
Jones, Todd R.
This study investigates a variety of features present in a new configuration of the Community Atmosphere Model (CAM) variant, SP-CAM 2.0. The new configuration (multiple-parameterization-CAM, MP-CAM) changes the manner in which the super-parameterization (SP) concept represents physical tendency feedbacks to the large-scale by using the mean of 10 independent two-dimensional cloud-permitting model (CPM) curtains in each global model column instead of the conventional single CPM curtain. The climates of the SP and MP configurations are examined to investigate any significant differences caused by the application of convective physical tendencies that are more deterministic in nature, paying particular attention to extreme precipitation events and large-scale weather systems, such as the Madden-Julian Oscillation (MJO). A number of small but significant changes in the mean state climate are uncovered, and it is found that the new formulation degrades MJO performance. Despite these deficiencies, the ensemble of possible realizations of convective states in the MP configuration allows for analysis of uncertainty in the small-scale solution, lending to examination of those weather regimes and physical mechanisms associated with strong, chaotic convection. Methods of quantifying precipitation predictability are explored, and use of the most reliable of these leads to the conclusion that poor precipitation predictability is most directly related to the proximity of the global climate model column state to atmospheric critical points. Secondarily, the predictability is tied to the availability of potential convective energy, the presence of mesoscale convective organization on the CPM grid, and the directive power of the large-scale.
Systematic Parameterization, Storage, and Representation of Volumetric DICOM Data.
Fischer, Felix; Selver, M Alper; Gezer, Sinem; Dicle, Oğuz; Hillen, Walter
Tomographic medical imaging systems produce hundreds to thousands of slices, enabling three-dimensional (3D) analysis. Radiologists process these images through various tools and techniques in order to generate 3D renderings for various applications, such as surgical planning, medical education, and volumetric measurements. To save and store these visualizations, current systems use snapshots or video exporting, which prevents further optimizations and requires the storage of significant additional data. The Grayscale Softcopy Presentation State extension of the Digital Imaging and Communications in Medicine (DICOM) standard resolves this issue for two-dimensional (2D) data by introducing an extensive set of parameters, namely 2D Presentation States (2DPR), that describe how an image should be displayed. 2DPR allows storing these parameters instead of storing parameter applied images, which cause unnecessary duplication of the image data. Since there is currently no corresponding extension for 3D data, in this study, a DICOM-compliant object called 3D presentation states (3DPR) is proposed for the parameterization and storage of 3D medical volumes. To accomplish this, the 3D medical visualization process is divided into four tasks, namely pre-processing, segmentation, post-processing, and rendering. The important parameters of each task are determined. Special focus is given to the compression of segmented data, parameterization of the rendering process, and DICOM-compliant implementation of the 3DPR object. The use of 3DPR was tested in a radiology department on three clinical cases, which require multiple segmentations and visualizations during the workflow of radiologists. The results show that 3DPR can effectively simplify the workload of physicians by directly regenerating 3D renderings without repeating intermediate tasks, increase efficiency by preserving all user interactions, and provide efficient storage as well as transfer of visualized data.
Timescale stretch parameterization of Type Ia supernova B-band light curves
International Nuclear Information System (INIS)
Goldhaber, G.; Groom, D.E.; Kim, A.; Aldering, G.; Astier, P.; Conley, A.; Deustua, S.E.; Ellis, R.; Fabbro, S.; Fruchter, A.S.; Goobar, A.; Hook, I.; Irwin, M.; Kim, M.; Knop, R.A.; Lidman, C.; McMahon, R.; Nugent, P.E.; Pain, R.; Panagia, N.; Pennypacker, C.R.; Perlmutter, S.; Ruiz-Lapuente, P.; Schaefer, B.; Walton, N.A.; York, T.
2001-01-01
R-band intensity measurements along the light curve of Type Ia supernovae discovered by the Cosmology Project (SCP) are fitted in brightness to templates allowing a free parameter the time-axis width factor w identically equal to s times (1+z). The data points are then individually aligned in the time-axis, normalized and K-corrected back to the rest frame, after which the nearly 1300 normalized intensity measurements are found to lie on a well-determined common rest-frame B-band curve which we call the ''composite curve.'' The same procedure is applied to 18 low-redshift Calan/Tololo SNe with Z < 0.11; these nearly 300 B-band photometry points are found to lie on the composite curve equally well. The SCP search technique produces several measurements before maximum light for each supernova. We demonstrate that the linear stretch factor, s, which parameterizes the light-curve timescale appears independent of z, and applies equally well to the declining and rising parts of the light curve. In fact, the B band template that best fits this composite curve fits the individual supernova photometry data when stretched by a factor s with chi 2/DoF ∼ 1, thus as well as any parameterization can, given the current data sets. The measurement of the data of explosion, however, is model dependent and not tightly constrained by the current data. We also demonstrate the 1 + z light-cure time-axis broadening expected from cosmological expansion. This argues strongly against alternative explanations, such as tired light, for the redshift of distant objects
Mirus, Benjamin B.
2015-01-01
Incorporating the influence of soil structure and horizons into parameterizations of distributed surface water/groundwater models remains a challenge. Often, only a single soil unit is employed, and soil-hydraulic properties are assigned based on textural classification, without evaluating the potential impact of these simplifications. This study uses a distributed physics-based model to assess the influence of soil horizons and structure on effective parameterization. This paper tests the viability of two established and widely used hydrogeologic methods for simulating runoff and variably saturated flow through layered soils: (1) accounting for vertical heterogeneity by combining hydrostratigraphic units with contrasting hydraulic properties into homogeneous, anisotropic units and (2) use of established pedotransfer functions based on soil texture alone to estimate water retention and conductivity, without accounting for the influence of pedon structures and hysteresis. The viability of this latter method for capturing the seasonal transition from runoff-dominated to evapotranspiration-dominated regimes is also tested here. For cases tested here, event-based simulations using simplified vertical heterogeneity did not capture the state-dependent anisotropy and complex combinations of runoff generation mechanisms resulting from permeability contrasts in layered hillslopes with complex topography. Continuous simulations using pedotransfer functions that do not account for the influence of soil structure and hysteresis generally over-predicted runoff, leading to propagation of substantial water balance errors. Analysis suggests that identifying a dominant hydropedological unit provides the most acceptable simplification of subsurface layering and that modified pedotransfer functions with steeper soil-water retention curves might adequately capture the influence of soil structure and hysteresis on hydrologic response in headwater catchments.
Directory of Open Access Journals (Sweden)
Andrew G. Slater
2011-05-01
Full Text Available The Community Land Model is the land component of the Community Climate System Model. Here, we describe a broad set of model improvements and additions that have been provided through the CLM development community to create CLM4. The model is extended with a carbon-nitrogen (CN biogeochemical model that is prognostic with respect to vegetation, litter, and soil carbon and nitrogen states and vegetation phenology. An urban canyon model is added and a transient land cover and land use change (LCLUC capability, including wood harvest, is introduced, enabling study of historic and future LCLUC on energy, water, momentum, carbon, and nitrogen fluxes. The hydrology scheme is modified with a revised numerical solution of the Richards equation and a revised ground evaporation parameterization that accounts for litter and within-canopy stability. The new snow model incorporates the SNow and Ice Aerosol Radiation model (SNICAR - which includes aerosol deposition, grain-size dependent snow aging, and vertically-resolved snowpack heating – as well as new snow cover and snow burial fraction parameterizations. The thermal and hydrologic properties of organic soil are accounted for and the ground column is extended to ~50-m depth. Several other minor modifications to the land surface types dataset, grass and crop optical properties, atmospheric forcing height, roughness length and displacement height, and the disposition of snow-capped runoff are also incorporated.Taken together, these augmentations to CLM result in improved soil moisture dynamics, drier soils, and stronger soil moisture variability. The new model also exhibits higher snow cover, cooler soil temperatures in organic-rich soils, greater global river discharge, and lower albedos over forests and grasslands, all of which are improvements compared to CLM3.5. When CLM4 is run with CN, the mean biogeophysical simulation is slightly degraded because the vegetation structure is prognostic rather
Using Remote Sensing Data to Parameterize Ice Jam Modeling for a Northern Inland Delta
Directory of Open Access Journals (Sweden)
Fan Zhang
2017-04-01
Full Text Available The Slave River is a northern river in Canada, with ice being an important component of its flow regime for at least half of the year. During the spring breakup period, ice jams and ice-jam flooding can occur in the Slave River Delta, which is of benefit for the replenishment of moisture and sediment required to maintain the ecological integrity of the delta. To better understand the ice jam processes that lead to flooding, as well as the replenishment of the delta, the one-dimensional hydraulic river ice model RIVICE was implemented to simulate and explore ice jam formation in the Slave River Delta. Incoming ice volume, a crucial input parameter for RIVICE, was determined by the novel approach of using MODIS space-born remote sensing imagery. Space-borne and air-borne remote sensing data were used to parameterize the upstream ice volume available for ice jamming. Gauged data was used to complement modeling calibration and validation. HEC-RAS, another one-dimensional hydrodynamic model, was used to determine ice volumes required for equilibrium jams and the upper limit of ice volume that a jam can sustain, as well as being used as a threshold for the volumes estimated by the dynamic ice jam simulations using RIVICE. Parameter sensitivity analysis shows that morphological and hydraulic properties have great impacts on the ice jam length and water depth in the Slave River Delta.
Directory of Open Access Journals (Sweden)
Hsiang Ling Chen
Full Text Available Anthropogenic infrastructure such as roads and non-native species are major causes of species endangerment. Understanding animal behavioral responses to roads and traffic provides insight into causes and mechanisms of effects of linear development on wildlife and aids effective mitigation and conservation. We investigated effects of roads and traffic on space use and movements of two forest-dwelling species: endemic, forest-dependent Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis and introduced, edge-tolerant Abert's squirrels (Sciurus aberti. To assess the effects of roads on space use and movement patterns, we compared the probability that a squirrel home range included roads and random lines in forests, and assessed effects of traffic intensity on rate of road crossing and movement patterns. Red squirrels avoided areas adjacent to roads and rarely crossed roads. In contrast, Abert's squirrels were more likely to include roads in their home ranges compared to random lines in forests. Both red squirrels and Abert's squirrels increased speed when crossing roads, compared to before and after road crossings. Increased hourly traffic volume reduced the rate of road crossings by both species. Behavioral responses of red squirrels to roads and traffic resemble responses to elevated predation risk, including reduced speed near roads and increased tortuosity of movement paths with increased traffic volume. In contrast, Abert's squirrels appeared little affected by roads and traffic with tortuosity of movement paths reduced as distance to roads decreased. We found that species with similar body size category (<1 kg but different habitat preference and foraging strategy responded to roads differently and demonstrated that behavior and ecology are important when considering effects of roads on wildlife. Our results indicate that roads restricted movements and space use of a native forest-dependent species while creating habitat preferred
Chen, Hsiang Ling; Koprowski, John L
2016-01-01
Anthropogenic infrastructure such as roads and non-native species are major causes of species endangerment. Understanding animal behavioral responses to roads and traffic provides insight into causes and mechanisms of effects of linear development on wildlife and aids effective mitigation and conservation. We investigated effects of roads and traffic on space use and movements of two forest-dwelling species: endemic, forest-dependent Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis) and introduced, edge-tolerant Abert's squirrels (Sciurus aberti). To assess the effects of roads on space use and movement patterns, we compared the probability that a squirrel home range included roads and random lines in forests, and assessed effects of traffic intensity on rate of road crossing and movement patterns. Red squirrels avoided areas adjacent to roads and rarely crossed roads. In contrast, Abert's squirrels were more likely to include roads in their home ranges compared to random lines in forests. Both red squirrels and Abert's squirrels increased speed when crossing roads, compared to before and after road crossings. Increased hourly traffic volume reduced the rate of road crossings by both species. Behavioral responses of red squirrels to roads and traffic resemble responses to elevated predation risk, including reduced speed near roads and increased tortuosity of movement paths with increased traffic volume. In contrast, Abert's squirrels appeared little affected by roads and traffic with tortuosity of movement paths reduced as distance to roads decreased. We found that species with similar body size category (roads differently and demonstrated that behavior and ecology are important when considering effects of roads on wildlife. Our results indicate that roads restricted movements and space use of a native forest-dependent species while creating habitat preferred by an introduced, edge-tolerant species.
Yang, Jintao; Zhang, Mingzhen; Chen, Hong; Chang, Yung; Chen, Zhan; Zheng, Jie
2014-08-11
Numerous biocompatible antifouling polymers have been developed for a wide variety of fundamental and practical applications in drug delivery, biosensors, marine coatings, and many other areas. Several antifouling mechanisms have been proposed, but the exact relationship among molecular structure, surface hydration property, and antifouling performance of antifouling polymers still remains elusive. Here this work strives to provide a better understanding of the structure-property relationship of poly(N-hydroxyalkyl acrylamide)-based materials. We have designed, synthesized, and characterized a series of polyHAAA brushes of various carbon spacer lengths (CSLs), that is, poly(N-hydroxymethyl acrylamide) (polyHMAA), poly(N-(2-hydroxyethyl)acrylamide) (polyHEAA), poly(N-(3-hydroxypropyl)acrylamide) (polyHPAA), and poly(N-(5-hydroxypentyl)acrylamide) (polyHPenAA), to study the structural dependence of CSLs on their antifouling performance. HMAA, HEAA, HPAA, and HPenAA monomers contained one, two, three, and five methylene groups between hydroxyl and amide groups, while the other groups in polymer backbones were the same as each other. The relation of such small structural differences of polymer brushes to their surface hydration and antifouling performance was studied by combined experimental and computational methods including surface plasmon resonance sensors, sum frequency generation (SFG) vibrational spectroscopy, cell adhesion assay, and molecular simulations. Antifouling results showed that all polyHAAA-based brushes were highly surface resistant to protein adsorption from single protein solutions, undiluted blood serum and plasma, as well as cell adhesion up to 7 days. In particular, polyHMAA and polyHEAA with the shorter CSLs exhibited higher surface hydration and better antifouling ability than polyHPMA and polyHPenAA. SFG and molecular simulations further revealed that the variation of CSLs changed the ratio of hydrophobicity/hydrophilicity of polymers
The CCPP-ARM Parameterization Testbed (CAPT): Where Climate Simulation Meets Weather Prediction
Energy Technology Data Exchange (ETDEWEB)
Phillips, T J; Potter, G L; Williamson, D L; Cederwall, R T; Boyle, J S; Fiorino, M; Hnilo, J J; Olson, J G; Xie, S; Yio, J J
2003-11-21
To significantly improve the simulation of climate by general circulation models (GCMs), systematic errors in representations of relevant processes must first be identified, and then reduced. This endeavor demands, in particular, that the GCM parameterizations of unresolved processes should be tested over a wide range of time scales, not just in climate simulations. Thus, a numerical weather prediction (NWP) methodology for evaluating model parameterizations and gaining insights into their behavior may prove useful, provied that suitable adaptations are made for implementation in climate GCMs. This method entails the generation of short-range weather forecasts by realistically initialized climate GCM, and the application of six-hourly NWP analyses and observations of parameterized variables to evaluate these forecasts. The behavior of the parameterizations in such a weather-forecasting framework can provide insights on how these schemes might be improved, and modified parameterizations then can be similarly tested. In order to further this method for evaluating and analyzing parameterizations in climate GCMs, the USDOE is funding a joint venture of its Climate Change Prediction Program (CCPP) and Atmospheric Radiation Measurement (ARM) Program: the CCPP-ARM Parameterization Testbed (CAPT). This article elaborates the scientific rationale for CAPT, discusses technical aspects of its methodology, and presents examples of its implementation in a representative climate GCM. Numerical weather prediction methods show promise for improving parameterizations in climate GCMs.
A shallow convection parameterization for the non-hydrostatic MM5 mesoscale model
Energy Technology Data Exchange (ETDEWEB)
Seaman, N.L.; Kain, J.S.; Deng, A. [Pennsylvania State Univ., University Park, PA (United States)
1996-04-01
A shallow convection parameterization suitable for the Pennsylvannia State University (PSU)/National Center for Atmospheric Research nonhydrostatic mesoscale model (MM5) is being developed at PSU. The parameterization is based on parcel perturbation theory developed in conjunction with a 1-D Mellor Yamada 1.5-order planetary boundary layer scheme and the Kain-Fritsch deep convection model.
Distance parameterization for efficient seismic history matching with the ensemble Kalman Filter
Leeuwenburgh, O.; Arts, R.
2012-01-01
The Ensemble Kalman Filter (EnKF), in combination with travel-time parameterization, provides a robust and flexible method for quantitative multi-model history matching to time-lapse seismic data. A disadvantage of the parameterization in terms of travel-times is that it requires simulation of
Directory of Open Access Journals (Sweden)
J. P. McCormack
2006-01-01
Full Text Available The new CHEM2D-Ozone Photochemistry Parameterization (CHEM2D-OPP for high-altitude numerical weather prediction (NWP systems and climate models specifies the net ozone photochemical tendency and its sensitivity to changes in ozone mixing ratio, temperature and overhead ozone column based on calculations from the CHEM2D interactive middle atmospheric photochemical transport model. We evaluate CHEM2D-OPP performance using both short-term (6-day and long-term (1-year stratospheric ozone simulations with the prototype high-altitude NOGAPS-ALPHA forecast model. An inter-comparison of NOGAPS-ALPHA 6-day ozone hindcasts for 7 February 2005 with ozone photochemistry parameterizations currently used in operational NWP systems shows that CHEM2D-OPP yields the best overall agreement with both individual Aura Microwave Limb Sounder ozone profile measurements and independent hemispheric (10°–90° N ozone analysis fields. A 1-year free-running NOGAPS-ALPHA simulation using CHEM2D-OPP produces a realistic seasonal cycle in zonal mean ozone throughout the stratosphere. We find that the combination of a model cold temperature bias at high latitudes in winter and a warm bias in the CHEM2D-OPP temperature climatology can degrade the performance of the linearized ozone photochemistry parameterization over seasonal time scales despite the fact that the parameterized temperature dependence is weak in these regions.
Sepehry-Fard, F.; Coulthard, Maurice H.
1995-01-01
The process of predicting the values of maintenance time dependent variable parameters such as mean time between failures (MTBF) over time must be one that will not in turn introduce uncontrolled deviation in the results of the ILS analysis such as life cycle costs, spares calculation, etc. A minor deviation in the values of the maintenance time dependent variable parameters such as MTBF over time will have a significant impact on the logistics resources demands, International Space Station availability and maintenance support costs. There are two types of parameters in the logistics and maintenance world: a. Fixed; b. Variable Fixed parameters, such as cost per man hour, are relatively easy to predict and forecast. These parameters normally follow a linear path and they do not change randomly. However, the variable parameters subject to the study in this report such as MTBF do not follow a linear path and they normally fall within the distribution curves which are discussed in this publication. The very challenging task then becomes the utilization of statistical techniques to accurately forecast the future non-linear time dependent variable arisings and events with a high confidence level. This, in turn, shall translate in tremendous cost savings and improved availability all around.
Identifiability of Model Properties in Over-Parameterized Model Classes
DEFF Research Database (Denmark)
Jaeger, Manfred
2013-01-01
Classical learning theory is based on a tight linkage between hypothesis space (a class of function on a domain X), data space (function-value examples (x, f(x))), and the space of queries for the learned model (predicting function values for new examples x). However, in many learning scenarios t...
Scale dependency of regional climate modeling of current and future climate extremes in Germany
Tölle, Merja H.; Schefczyk, Lukas; Gutjahr, Oliver
2017-11-01
A warmer climate is projected for mid-Europe, with less precipitation in summer, but with intensified extremes of precipitation and near-surface temperature. However, the extent and magnitude of such changes are associated with creditable uncertainty because of the limitations of model resolution and parameterizations. Here, we present the results of convection-permitting regional climate model simulations for Germany integrated with the COSMO-CLM using a horizontal grid spacing of 1.3 km, and additional 4.5- and 7-km simulations with convection parameterized. Of particular interest is how the temperature and precipitation fields and their extremes depend on the horizontal resolution for current and future climate conditions. The spatial variability of precipitation increases with resolution because of more realistic orography and physical parameterizations, but values are overestimated in summer and over mountain ridges in all simulations compared to observations. The spatial variability of temperature is improved at a resolution of 1.3 km, but the results are cold-biased, especially in summer. The increase in resolution from 7/4.5 km to 1.3 km is accompanied by less future warming in summer by 1 ∘C. Modeled future precipitation extremes will be more severe, and temperature extremes will not exclusively increase with higher resolution. Although the differences between the resolutions considered (7/4.5 km and 1.3 km) are small, we find that the differences in the changes in extremes are large. High-resolution simulations require further studies, with effective parameterizations and tunings for different topographic regions. Impact models and assessment studies may benefit from such high-resolution model results, but should account for the impact of model resolution on model processes and climate change.
A test harness for accelerating physics parameterization advancements into operations
Firl, G. J.; Bernardet, L.; Harrold, M.; Henderson, J.; Wolff, J.; Zhang, M.
2017-12-01
The process of transitioning advances in parameterization of sub-grid scale processes from initial idea to implementation is often much quicker than the transition from implementation to use in an operational setting. After all, considerable work must be undertaken by operational centers to fully test, evaluate, and implement new physics. The process is complicated by the scarcity of like-to-like comparisons, availability of HPC resources, and the ``tuning problem" whereby advances in physics schemes are difficult to properly evaluate without first undertaking the expensive and time-consuming process of tuning to other schemes within a suite. To address this process shortcoming, the Global Model TestBed (GMTB), supported by the NWS NGGPS project and undertaken by the Developmental Testbed Center, has developed a physics test harness. It implements the concept of hierarchical testing, where the same code can be tested in model configurations of varying complexity from single column models (SCM) to fully coupled, cycled global simulations. Developers and users may choose at which level of complexity to engage. Several components of the physics test harness have been implemented, including a SCM and an end-to-end workflow that expands upon the one used at NOAA/EMC to run the GFS operationally, although the testbed components will necessarily morph to coincide with changes to the operational configuration (FV3-GFS). A standard, relatively user-friendly interface known as the Interoperable Physics Driver (IPD) is available for physics developers to connect their codes. This prerequisite exercise allows access to the testbed tools and removes a technical hurdle for potential inclusion into the Common Community Physics Package (CCPP). The testbed offers users the opportunity to conduct like-to-like comparisons between the operational physics suite and new development as well as among multiple developments. GMTB staff have demonstrated use of the testbed through a
Mao, Baoguang; Guo, Donglei; Qin, Jinwen; Meng, Tao; Wang, Xin; Cao, Minhua
2018-01-08
Despite significant advancement in preparing various hollow structures by Ostwald ripening, one common problem is the intractable uncontrollability of initiating Ostwald ripening due to the complexity of the reaction processes. Here, a new strategy on Hansen solubility parameter (HSP)-guided solvent selection to initiate Ostwald ripening is proposed. Based on this comprehensive principle for solvent optimization, N,N-dimethylformamide (DMF) was screened out, achieving accurate synthesis of interior space-tunable MoSe 2 spherical structures (solid, core-shell, yolk-shell and hollow spheres). The resultant MoSe 2 structures exhibit architecture-dependent electrochemical performances towards hydrogen evolution reaction and sodium-ion batteries. This pre-solvent selection strategy can effectively provide researchers great possibility in efficiently synthesizing various hollow structures. This work paves a new pathway for deeply understanding Ostwald ripening. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Su, Jing-Jing; Gao, Yi-Tian
2018-03-01
Under investigation in this paper is a higher-order nonlinear Schrödinger equation with space-dependent coefficients, related to an optical fiber. Based on the self-similarity transformation and Hirota method, related to the integrability, the N-th-order bright and dark soliton solutions are derived under certain constraints. It is revealed that the velocities and trajectories of the solitons are both affected by the coefficient of the sixth-order dispersion term while the amplitudes of the solitons are determined by the gain function. Amplitudes increase when the gain function is positive and decrease when the gain function is negative. Furthermore, we find that the intensities of dark solitons are presented as a superposition of the solitons and stationary waves.
Yan, Peng; Zhang, Yangming
2018-06-01
High performance scanning of nano-manipulators is widely deployed in various precision engineering applications such as SPM (scanning probe microscope), where trajectory tracking of sophisticated reference signals is an challenging control problem. The situation is further complicated when rate dependent hysteresis of the piezoelectric actuators and the stress-stiffening induced nonlinear stiffness of the flexure mechanism are considered. In this paper, a novel control framework is proposed to achieve high precision tracking of a piezoelectric nano-manipulator subjected to hysteresis and stiffness nonlinearities. An adaptive parameterized rate-dependent Prandtl-Ishlinskii model is constructed and the corresponding adaptive inverse model based online compensation is derived. Meanwhile a robust adaptive control architecture is further introduced to improve the tracking accuracy and robustness of the compensated system, where the parametric uncertainties of the nonlinear dynamics can be well eliminated by on-line estimations. Comparative experimental studies of the proposed control algorithm are conducted on a PZT actuated nano-manipulating stage, where hysteresis modeling accuracy and excellent tracking performance are demonstrated in real-time implementations, with significant improvement over existing results.
Gim, Hyeon-Ju; Park, Seon Ki; Kang, Minseok; Thakuri, Bindu Malla; Kim, Joon; Ho, Chang-Hoi
2017-08-01
In the land surface models predicting vegetation growth and decay, representation of the seasonality of land surface energy and mass fluxes largely depends on how to describe the vegetation dynamics. In this study, we developed a new parameterization scheme to characterize allocation of the assimilated carbon to plant parts, including leaves and fine roots. The amount of carbon allocation in this scheme depends on the climatological net primary production (NPP) of the plants. The newly developed scheme is implemented in the augmented Noah land surface model with multiple parameterization options (Noah-MP) along with other biophysical processes related to variations in photosynthetic capacity. The scheme and the augmented biophysical processes are evaluated against tower measurements of vegetation from four forest sites in various regions—two for the deciduous broadleaf and two for the needleleaf evergreen forest. Results from the augmented Noah-MP showed good agreement with the observations and demonstrated improvements in representing the seasonality of leaf area index (LAI), gross primary production (GPP), ecosystem respiration (ER), and latent heat flux. In particular, significant improvements are found in simulating amplitudes and phase shift timing in the LAI seasonal cycle, and the amount of GPP and ER in the growing season. Furthermore, the augmented Noah-MP performed reasonably well in simulating the spatial distributions of LAI, GPP, and NPP in East Asia, consistent with the satellite observations.
Experimental continuously reinforced concrete pavement parameterization using nondestructive methods
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L. S. Salles
Full Text Available ABSTRACT Four continuously reinforced concrete pavement (CRCP sections were built at the University of São Paulo campus in order to analyze the pavement performance in a tropical environment. The sections short length coupled with particular project aspects made the experimental CRCP cracking be different from the traditional CRCP one. After three years of construction, a series of nondestructive testing were performed - Falling Weight Deflectometer (FWD loadings - to verify and to parameterize the pavement structural condition based on two main properties: the elasticity modulus of concrete (E and the modulus of subgrade reaction (k. These properties estimation was obtained through the matching process between real and EverFE simulated basins with the load at the slab center, between two consecutive cracks. The backcalculation results show that the lack of anchorage at the sections end decreases the E and k values and that the longitudinal reinforcement percentage provides additional stiffness to the pavement. Additionally, FWD loadings tangential to the cracks allowed the load transfer efficiency (LTE estimation determination across cracks. The LTE resulted in values above 90 % for all cracks.
Parameterization-based tracking for the P2 experiment
Energy Technology Data Exchange (ETDEWEB)
Sorokin, Iurii [Institut fuer Kernphysik and PRISMA Cluster of Excellence, Mainz (Germany); Collaboration: P2-Collaboration
2016-07-01
The P2 experiment at the new MESA accelerator in Mainz aims to determine the weak mixing angle by measuring the parity-violating asymmetry in elastic electron-proton scattering at low momentum transfer. To achieve an unprecedented precision an order of 10{sup 11} scattered electrons per second have to be acquired. %within the acceptance. Whereas the tracking system is not required to operate at such high rates, every attempt is made to achieve as high rate capability as possible. The P2 tracking system will consist of four planes of high-voltage monolithic active pixel sensors (HV-MAPS). With the present preliminary design one expects about 150 signal electron tracks and 20000 background hits (from bremsstrahlung photons) per plane in every 50 ns readout frame at the full rate. In order to cope with this extreme combinatorial background in on-line mode, a parameterization-based tracking is considered as a possible solution. The idea is to transform the hit positions into a set of weakly correlated quantities, and to find simple (e.g. polynomial) functions of these quantities, that would give the required characteristics of the track (e.g. momentum). The parameters of the functions are determined from a sample of high-quality tracks, taken either from a simulation, or reconstructed in a conventional way from a sample of low-rate data.
Factors influencing the parameterization of anvil clouds within GCMs
International Nuclear Information System (INIS)
Leone, J.M. Jr.; Chin, Hung-Neng.
1993-03-01
The overall goal of this project is to improve the representation of clouds and their effects within global climate models (GCMs). The authors have concentrated on a small portion of the overall goal, the evolution of convectively generated cirrus clouds and their effects on the large-scale environment. Because of the large range of time and length scales involved they have been using a multi-scale attack. For the early time generation and development of the cirrus anvil they are using a cloud-scale model with horizontal resolution of 1--2 kilometers; while for the larger scale transport by the larger scale flow they are using a mesoscale model with a horizontal resolution of 20--60 kilometers. The eventual goal is to use the information obtained from these simulations together with available observations to derive improved cloud parameterizations for use in GCMs. This paper presents results from their cloud-scale studies and describes a new tool, a cirrus generator, that they have developed to aid in their mesoscale studies
Influence of Ice Nuclei Parameterization Schemes on the Hail Process
Directory of Open Access Journals (Sweden)
Xiaoli Liu
2018-01-01
Full Text Available Ice nuclei are very important factors as they significantly affect the development and evolvement of convective clouds such as hail clouds. In this study, numerical simulations of hail processes in the Zhejiang Province were conducted using a mesoscale numerical model (WRF v3.4. The effects of six ice nuclei parameterization schemes on the macroscopic and microscopic structures of hail clouds were compared. The effect of the ice nuclei concentration on ground hailfall is stronger than that on ground rainfall. There were significant spatiotemporal, intensity, and distribution differences in hailfall. Changes in the ice nuclei concentration caused different changes in hydrometeors and directly affected the ice crystals, and, hence, the spatiotemporal distribution of other hydrometeors and the thermodynamic structure of clouds. An increased ice nuclei concentration raises the initial concentration of ice crystals with higher mixing ratio. In the developing and early maturation stages of hail cloud, a larger number of ice crystals competed for water vapor with increasing ice nuclei concentration. This effect prevents ice crystals from maturing into snow particles and inhibits the formation and growth of hail embryos. During later maturation stages, updraft in the cloud intensified and more supercooled water was transported above the 0°C level, benefitting the production and growth of hail particles. An increased ice nuclei concentration therefore favors the formation of hail.
Frozen soil parameterization in a distributed biosphere hydrological model
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L. Wang
2010-03-01
Full Text Available In this study, a frozen soil parameterization has been modified and incorporated into a distributed biosphere hydrological model (WEB-DHM. The WEB-DHM with the frozen scheme was then rigorously evaluated in a small cold area, the Binngou watershed, against the in-situ observations from the WATER (Watershed Allied Telemetry Experimental Research. First, by using the original WEB-DHM without the frozen scheme, the land surface parameters and two van Genuchten parameters were optimized using the observed surface radiation fluxes and the soil moistures at upper layers (5, 10 and 20 cm depths at the DY station in July. Second, by using the WEB-DHM with the frozen scheme, two frozen soil parameters were calibrated using the observed soil temperature at 5 cm depth at the DY station from 21 November 2007 to 20 April 2008; while the other soil hydraulic parameters were optimized by the calibration of the discharges at the basin outlet in July and August that covers the annual largest flood peak in 2008. With these calibrated parameters, the WEB-DHM with the frozen scheme was then used for a yearlong validation from 21 November 2007 to 20 November 2008. Results showed that the WEB-DHM with the frozen scheme has given much better performance than the WEB-DHM without the frozen scheme, in the simulations of soil moisture profile at the cold regions catchment and the discharges at the basin outlet in the yearlong simulation.
Test Driven Development of a Parameterized Ice Sheet Component
Clune, T.
2011-12-01
Test driven development (TDD) is a software development methodology that offers many advantages over traditional approaches including reduced development and maintenance costs, improved reliability, and superior design quality. Although TDD is widely accepted in many software communities, the suitability to scientific software is largely undemonstrated and warrants a degree of skepticism. Indeed, numerical algorithms pose several challenges to unit testing in general, and TDD in particular. Among these challenges are the need to have simple, non-redundant closed-form expressions to compare against the results obtained from the implementation as well as realistic error estimates. The necessity for serial and parallel performance raises additional concerns for many scientific applicaitons. In previous work I demonstrated that TDD performed well for the development of a relatively simple numerical model that simulates the growth of snowflakes, but the results were anecdotal and of limited relevance to far more complex software components typical of climate models. This investigation has now been extended by successfully applying TDD to the implementation of a substantial portion of a new parameterized ice sheet component within a full climate model. After a brief introduction to TDD, I will present techniques that address some of the obstacles encountered with numerical algorithms. I will conclude with some quantitative and qualitative comparisons against climate components developed in a more traditional manner.
Boundary layer parameterizations and long-range transport
International Nuclear Information System (INIS)
Irwin, J.S.
1992-01-01
A joint work group between the American Meteorological Society (AMS) and the EPA is perusing the construction of an air quality model that incorporates boundary layer parameterizations of dispersion and transport. This model could replace the currently accepted model, the Industrial Source Complex (ISC) model. The ISC model is a Gaussian-plume multiple point-source model that provides for consideration of fugitive emissions, aerodynamic wake effects, gravitational settling and dry deposition. A work group of several Federal and State agencies is perusing the construction of an air quality modeling system for use in assessing and tracking visibility impairment resulting from long-range transport of pollutants. The modeling system is designed to use the hourly vertical profiles of wind, temperature and moisture resulting from a mesoscale meteorological processor that employs four dimensional data assimilation (FDDA). FDDA involves adding forcing functions to the governing model equations to gradually ''nudge'' the model state toward the observations (12-hourly upper air observations of wind, temperature and moisture, and 3-hourly surface observations of wind and moisture). In this way it is possible to generate data sets whose accuracy, in terms of transport, precipitation, and dynamic consistency is superior to both direct interpolation of synoptic-scale analyses of observations and purely predictive mode model result. (AB) ( 19 refs.)
Pan, Wenyong; Innanen, Kristopher A.; Geng, Yu
2018-03-01
Seismic full-waveform inversion (FWI) methods hold strong potential to recover multiple subsurface elastic properties for hydrocarbon reservoir characterization. Simultaneously updating multiple physical parameters introduces the problem of interparameter tradeoff, arising from the covariance between different physical parameters, which increases nonlinearity and uncertainty of multiparameter FWI. The coupling effects of different physical parameters are significantly influenced by model parameterization and acquisition arrangement. An appropriate choice of model parameterization is critical to successful field data applications of multiparameter FWI. The objective of this paper is to examine the performance of various model parameterizations in isotropic-elastic FWI with walk-away vertical seismic profile (W-VSP) dataset for unconventional heavy oil reservoir characterization. Six model parameterizations are considered: velocity-density (α, β and ρ΄), modulus-density (κ, μ and ρ), Lamé-density (λ, μ΄ and ρ‴), impedance-density (IP, IS and ρ″), velocity-impedance-I (α΄, β΄ and I_P^'), and velocity-impedance-II (α″, β″ and I_S^'). We begin analyzing the interparameter tradeoff by making use of scattering radiation patterns, which is a common strategy for qualitative parameter resolution analysis. In this paper, we discuss the advantages and limitations of the scattering radiation patterns and recommend that interparameter tradeoffs be evaluated using interparameter contamination kernels, which provide quantitative, second-order measurements of the interparameter contaminations and can be constructed efficiently with an adjoint-state approach. Synthetic W-VSP isotropic-elastic FWI experiments in the time domain verify our conclusions about interparameter tradeoffs for various model parameterizations. Density profiles are most strongly influenced by the interparameter contaminations; depending on model parameterization, the inverted density
Parameterization of Fuel-Optimal Synchronous Approach Trajectories to Tumbling Targets
Directory of Open Access Journals (Sweden)
David Charles Sternberg
2018-04-01
Full Text Available Docking with potentially tumbling Targets is a common element of many mission architectures, including on-orbit servicing and active debris removal. This paper studies synchronized docking trajectories as a way to ensure the Chaser satellite remains on the docking axis of the tumbling Target, thereby reducing collision risks and enabling persistent onboard sensing of the docking location. Chaser satellites have limited computational power available to them and the time allowed for the determination of a fuel optimal trajectory may be limited. Consequently, parameterized trajectories that approximate the fuel optimal trajectory while following synchronous approaches may be used to provide a computationally efficient means of determining near optimal trajectories to a tumbling Target. This paper presents a method of balancing the computation cost with the added fuel expenditure required for parameterization, including the selection of a parameterization scheme, the number of parameters in the parameterization, and a means of incorporating the dynamics of a tumbling satellite into the parameterization process. Comparisons of the parameterized trajectories are made with the fuel optimal trajectory, which is computed through the numerical propagation of Euler’s equations. Additionally, various tumble types are considered to demonstrate the efficacy of the presented computation scheme. With this parameterized trajectory determination method, Chaser satellites may perform terminal approach and docking maneuvers with both fuel and computational efficiency.
The feasibility of parameterizing four-state equilibria using relaxation dispersion measurements
International Nuclear Information System (INIS)
Li Pilong; Martins, Ilídio R. S.; Rosen, Michael K.
2011-01-01
Coupled equilibria play important roles in controlling information flow in biochemical systems, including allosteric molecules and multidomain proteins. In the simplest case, two equilibria are coupled to produce four interconverting states. In this study, we assessed the feasibility of determining the degree of coupling between two equilibria in a four-state system via relaxation dispersion measurements. A major bottleneck in this effort is the lack of efficient approaches to data analysis. To this end, we designed a strategy to efficiently evaluate the smoothness of the target function surface (TFS). Using this approach, we found that the TFS is very rough when fitting benchmark CPMG data to all adjustable variables of the four-state equilibria. After constraining a portion of the adjustable variables, which can often be achieved through independent biochemical manipulation of the system, the smoothness of TFS improves dramatically, although it is still insufficient to pinpoint the solution. The four-state equilibria can be finally solved with further incorporation of independent chemical shift information that is readily available. We also used Monte Carlo simulations to evaluate how well each adjustable parameter can be determined in a large kinetic and thermodynamic parameter space and how much improvement can be achieved in defining the parameters through additional measurements. The results show that in favorable conditions the combination of relaxation dispersion and biochemical manipulation allow the four-state equilibrium to be parameterized, and thus coupling strength between two processes to be determined.
The parameterized post-Newtonian limit of bimetric theories of gravity
International Nuclear Information System (INIS)
Clifton, Timothy; Banados, Maximo; Skordis, Constantinos
2010-01-01
We consider the post-Newtonian limit of a general class of bimetric theories of gravity, in which both metrics are dynamical. The established parameterized post-Newtonian approach is followed as closely as possible, although new potentials are found that do not exist within the standard framework. It is found that these theories can evade solar system tests of post-Newtonian gravity remarkably well. We show that perturbations about Minkowski space in these theories contain both massless and massive degrees of freedom, and that in general there are two different types of massive mode, each with a different mass parameter. If both of these masses are sufficiently large then the predictions of the most general class of theories we consider are indistinguishable from those of general relativity, up to post-Newtonian order in a weak-field, low-velocity expansion. In the limit that the massive modes become massless, we find that these general theories do not exhibit a van Dam-Veltman-Zakharov-like discontinuity in their γ parameter, although there are discontinuities in other post-Newtonian parameters as the massless limit is approached. This smooth behaviour in γ is due to the discontinuities from each of the two different massive modes cancelling each other out. Such cancellations cannot occur in special cases with only one massive mode, such as the Isham-Salam-Strathdee theory.
Parameterized Linear Temporal Logics Meet Costs: Still not Costlier than LTL
Directory of Open Access Journals (Sweden)
Martin Zimmermann
2015-09-01
Full Text Available We continue the investigation of parameterized extensions of Linear Temporal Logic (LTL that retain the attractive algorithmic properties of LTL: a polynomial space model checking algorithm and a doubly-exponential time algorithm for solving games. Alur et al. and Kupferman et al. showed that this is the case for Parametric LTL (PLTL and PROMPT-LTL respectively, which have temporal operators equipped with variables that bound their scope in time. Later, this was also shown to be true for Parametric LDL (PLDL, which extends PLTL to be able to express all omega-regular properties. Here, we generalize PLTL to systems with costs, i.e., we do not bound the scope of operators in time, but bound the scope in terms of the cost accumulated during time. Again, we show that model checking and solving games for specifications in PLTL with costs is not harder than the corresponding problems for LTL. Finally, we discuss PLDL with costs and extensions to multiple cost functions.
Ferentinos, Konstantinos P
2005-09-01
Two neural network (NN) applications in the field of biological engineering are developed, designed and parameterized by an evolutionary method based on the evolutionary process of genetic algorithms. The developed systems are a fault detection NN model and a predictive modeling NN system. An indirect or 'weak specification' representation was used for the encoding of NN topologies and training parameters into genes of the genetic algorithm (GA). Some a priori knowledge of the demands in network topology for specific application cases is required by this approach, so that the infinite search space of the problem is limited to some reasonable degree. Both one-hidden-layer and two-hidden-layer network architectures were explored by the GA. Except for the network architecture, each gene of the GA also encoded the type of activation functions in both hidden and output nodes of the NN and the type of minimization algorithm that was used by the backpropagation algorithm for the training of the NN. Both models achieved satisfactory performance, while the GA system proved to be a powerful tool that can successfully replace the problematic trial-and-error approach that is usually used for these tasks.
Lightweight hull surface self-design vertical parameterization method based on NURBS
Directory of Open Access Journals (Sweden)
ZHANG Yanru
2017-10-01
Full Text Available [Objectives] At present, conventional design is limited to parent ship design space, and cannot drive ship hull design using as few parameters as possible. In order to solve the above problems, [Methods] by combining the draught function with NURBS, a ship hull surface self-design method based on vertical parameterization is proposed. In this method, the waterline is designated as the basic design unit; the bottom flat end line, designed waterline, stem and stern contours, side flat end line and maximum section line are designated as the characteristic constraints of the ship hull; and the draught function values corresponding to the characteristic parameters are designated as the design objectives. In this way, a waterline approximation model is built, and an evolutionary algorithm can be used to solve the approximation model. Finally, the ship hull surface is generated on the basis of the waterline using the NURBS skinning technique.[Results] The design examples of the characteristic curves of the full-scale ship hull surface indicate the practicable and advanced nature of this method.[Conclusions] The hull surface can be designed with as little data as possible using this method, making it much more suitable for the self-design of new ship forms.
Fienen, Michael N.; D'Oria, Marco; Doherty, John E.; Hunt, Randall J.
2013-01-01
The application bgaPEST is a highly parameterized inversion software package implementing the Bayesian Geostatistical Approach in a framework compatible with the parameter estimation suite PEST. Highly parameterized inversion refers to cases in which parameters are distributed in space or time and are correlated with one another. The Bayesian aspect of bgaPEST is related to Bayesian probability theory in which prior information about parameters is formally revised on the basis of the calibration dataset used for the inversion. Conceptually, this approach formalizes the conditionality of estimated parameters on the speciﬁc data and model available. The geostatistical component of the method refers to the way in which prior information about the parameters is used. A geostatistical autocorrelation function is used to enforce structure on the parameters to avoid overﬁtting and unrealistic results. Bayesian Geostatistical Approach is designed to provide the smoothest solution that is consistent with the data. Optionally, users can specify a level of ﬁt or estimate a balance between ﬁt and model complexity informed by the data. Groundwater and surface-water applications are used as examples in this text, but the possible uses of bgaPEST extend to any distributed parameter applications.
Vanegas, Carlos A; Aliaga, Daniel G; Benes, Bedrich; Waddell, Paul
2009-01-01
Urban simulation models and their visualization are used to help regional planning agencies evaluate alternative transportation investments, land use regulations, and environmental protection policies. Typical urban simulations provide spatially distributed data about number of inhabitants, land prices, traffic, and other variables. In this article, we build on a synergy of urban simulation, urban visualization, and computer graphics to automatically infer an urban layout for any time step of the simulation sequence. In addition to standard visualization tools, our method gathers data of the original street network, parcels, and aerial imagery and uses the available simulation results to infer changes to the original urban layout and produce a new and plausible layout for the simulation results. In contrast with previous work, our approach automatically updates the layout based on changes in the simulation data and thus can scale to a large simulation over many years. The method in this article offers a substantial step forward in building integrated visualization and behavioral simulation systems for use in community visioning, planning, and policy analysis. We demonstrate our method on several real cases using a 200 GB database for a 16,300 km2 area surrounding Seattle.
Rolinski, S.; Müller, C.; Lotze-Campen, H.; Bondeau, A.
2010-12-01
More than a quarter of the Earth’s land surface is covered by grassland, which is also the major part (~ 70 %) of the agricultural area. Most of this area is used for livestock production in different degrees of intensity. The dynamic global vegetation model LPJmL (Sitch et al., Global Change Biology, 2003; Bondeau et al., Global Change Biology, 2007) is one of few process-based model that simulates biomass production on managed grasslands at the global scale. The implementation of managed grasslands and its evaluation has received little attention so far, as reference data on grassland productivity are scarce and the definition of grassland extent and usage are highly uncertain. However, grassland productivity is related to large areas, and strongly influences global estimates of carbon and water budgets and should thus be improved. Plants are implemented in LPJmL in an aggregated form as plant functional types assuming that processes concerning carbon and water fluxes are quite similar between species of the same type. Therefore, the parameterization of a functional type is possible with parameters in a physiologically meaningful range of values. The actual choice of the parameter values from the possible and reasonable phase space should satisfy the condition of the best fit of model results and measured data. In order to improve the parameterization of managed grass we follow a combined procedure using model output and measured data of carbon and water fluxes. By comparing carbon and water fluxes simultaneously, we expect well-balanced refinements and avoid over-tuning of the model in only one direction. The comparison of annual biomass from grassland to data from the Food and Agriculture Organization of the United Nations (FAO) per country provide an overview about the order of magnitude and the identification of deviations. The comparison of daily net primary productivity, soil respiration and water fluxes at specific sites (FluxNet Data) provides
Natural Ocean Carbon Cycle Sensitivity to Parameterizations of the Recycling in a Climate Model
Romanou, A.; Romanski, J.; Gregg, W. W.
2014-01-01
Sensitivities of the oceanic biological pump within the GISS (Goddard Institute for Space Studies ) climate modeling system are explored here. Results are presented from twin control simulations of the air-sea CO2 gas exchange using two different ocean models coupled to the same atmosphere. The two ocean models (Russell ocean model and Hybrid Coordinate Ocean Model, HYCOM) use different vertical coordinate systems, and therefore different representations of column physics. Both variants of the GISS climate model are coupled to the same ocean biogeochemistry module (the NASA Ocean Biogeochemistry Model, NOBM), which computes prognostic distributions for biotic and abiotic fields that influence the air-sea flux of CO2 and the deep ocean carbon transport and storage. In particular, the model differences due to remineralization rate changes are compared to differences attributed to physical processes modeled differently in the two ocean models such as ventilation, mixing, eddy stirring and vertical advection. GISSEH(GISSER) is found to underestimate mixed layer depth compared to observations by about 55% (10 %) in the Southern Ocean and overestimate it by about 17% (underestimate by 2%) in the northern high latitudes. Everywhere else in the global ocean, the two models underestimate the surface mixing by about 12-34 %, which prevents deep nutrients from reaching the surface and promoting primary production there. Consequently, carbon export is reduced because of reduced production at the surface. Furthermore, carbon export is particularly sensitive to remineralization rate changes in the frontal regions of the subtropical gyres and at the Equator and this sensitivity in the model is much higher than the sensitivity to physical processes such as vertical mixing, vertical advection and mesoscale eddy transport. At depth, GISSER, which has a significant warm bias, remineralizes nutrients and carbon faster thereby producing more nutrients and carbon at depth, which
Tool-driven Design and Automated Parameterization for Real-time Generic Drivetrain Models
Directory of Open Access Journals (Sweden)
Schwarz Christina
2015-01-01
Full Text Available Real-time dynamic drivetrain modeling approaches have a great potential for development cost reduction in the automotive industry. Even though real-time drivetrain models are available, these solutions are specific to single transmission topologies. In this paper an environment for parameterization of a solution is proposed based on a generic method applicable to all types of gear transmission topologies. This enables tool-guided modeling by non- experts in the fields of mechanic engineering and control theory leading to reduced development and testing efforts. The approach is demonstrated for an exemplary automatic transmission using the environment for automated parameterization. Finally, the parameterization is validated via vehicle measurement data.
USING PARAMETERIZATION OF OBJECTS IN AUTODESK INVENTOR IN DESIGNING STRUCTURAL CONNECTORS
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Gabriel Borowski
2015-05-01
Full Text Available The article presents the parameterization of objects used for designing the type of elements as structural connectors and making modifications of their characteristics. The design process was carried out using Autodesk Inventor 2015. We show the latest software tools, which were used for parameterization and modeling selected types of structural connectors. We also show examples of the use of parameterization facilities in the process of constructing some details and making changes to geometry with holding of the shape the element. The presented method of Inventor usage has enabled fast and efficient creation of new objects based on sketches created.
Bioavailability of radiocaesium in soil: parameterization using soil characteristics
Energy Technology Data Exchange (ETDEWEB)
Syssoeva, A.A.; Konopleva, I.V. [Russian Institute of Agricultural Radiology and Agroecology, Obninsk (Russian Federation)
2004-07-01
It has been shown that radiocaesium availability to plants strongly influenced by soil properties. For the best evaluation of TFs it necessary to use mechanistic models that predict radionuclide uptake by plants based on consideration of sorption-desorption and fixation-remobilization of the radionuclide in the soil as well as root uptake processes controlled by the plant. The aim of the research was to characterise typical Russian soils on the basis of the radiocaesium availability. The parameter of the radiocaesium availability in soils (A) has been developed which consist on radiocaesium exchangeability; CF -concentration factor which is the ratio of the radiocaesium in plant to that in soil solution; K{sub Dex} - exchangeable solid-liquid distribution coefficient of radiocaesium. The approach was tested for a wide range of Russian soils using radiocaesium uptake data from a barley pot trial and parameters of the radiocaesium bioavailability. Soils were collected from the arable horizons in different soil climatic zones of Russia and artificially contaminated by {sup 137}Cs. The classification of soils in terms of the radiocaesium availability corresponds quite well to observed linear relationship between {sup 137}Cs TF for barley and A. K{sub Dex} is related to the soil radiocaesium interception potential (RIP), which was found to be positively and strongly related to clay and physical clay (<0,01 mm) content. The {sup 137}Cs exchangeability were found to be in close relation to the soil vermiculite content, which was estimated by the method of Cs{sup +} fixation. It's shown radiocaesium availability to plants in soils under study can be parameterized through mineralogical soil characteristics: % clay and the soil vermiculite content. (author)
Exploring the data constrained phase space of the last Antarctic glacial cycle
Lecavalier, Benoit; Tarasov, Lev
2017-04-01
The evolution of the Antarctic Ice Sheet over the last two glacial cycles is studied using the Glacial Systems Model (GSM). Glaciological modelling is an effective tool to generate continental-scale reconstructions over glacial cycles, but the models depend on parameterizations to account for the deficiencies (e.g., missing physics, unresolved sub-grid processes, uncertain boundary conditions) inherent in any numerical model. These parameters, considered together, form a parameter phase space from which sets of parameters can be sampled; each set corresponds to an ice sheet reconstruction. The GSM has been updated with a number of recent developments: hybrid SIA-SSA physics, Schoof grounding line parameterization, broadened degrees of freedom in the climate forcing, sub-shelf melt explicitly dependent on ocean temperatures, improved hydrofracturing, cliff failure at the margins, basal topographic uncertainties, impact of basal drag roughness and subgrid statistics, and first order geoidal corrections in the coupled glacial isostatic adjustment component. Parametric uncertainties are defined in the GSM using >36 ensemble parameters. Prior to conducting a full Bayesian calibration, one must first validate the ability of the GSM to simulate a broad range of responses. We attempt this by latin hypercube sampling of the parameter phase space and comparing the model predictions against our constraint database consisting of past elevation, extent and relative sea level observations and the present day geometry. We document the capability of the GSM to envelope the observational constraints given the parametric uncertainties and discuss the implications for the evolution of the Antarctic Ice Sheet.
Awatey, M. T.; Irving, J.; Oware, E. K.
2016-12-01
Markov chain Monte Carlo (McMC) inversion frameworks are becoming increasingly popular in geophysics due to their ability to recover multiple equally plausible geologic features that honor the limited noisy measurements. Standard McMC methods, however, become computationally intractable with increasing dimensionality of the problem, for example, when working with spatially distributed geophysical parameter fields. We present a McMC approach based on a sparse proper orthogonal decomposition (POD) model parameterization that implicitly incorporates the physics of the underlying process. First, we generate training images (TIs) via Monte Carlo simulations of the target process constrained to a conceptual model. We then apply POD to construct basis vectors from the TIs. A small number of basis vectors can represent most of the variability in the TIs, leading to dimensionality reduction. A projection of the starting model into the reduced basis space generates the starting POD coefficients. At each iteration, only coefficients within a specified sampling window are resimulated assuming a Gaussian prior. The sampling window grows at a specified rate as the number of iteration progresses starting from the coefficients corresponding to the highest ranked basis to those of the least informative basis. We found this gradual increment in the sampling window to be more stable compared to resampling all the coefficients right from the first iteration. We demonstrate the performance of the algorithm with both synthetic and lab-scale electrical resistivity imaging of saline tracer experiments, employing the same set of basis vectors for all inversions. We consider two scenarios of unimodal and bimodal plumes. The unimodal plume is consistent with the hypothesis underlying the generation of the TIs whereas bimodality in plume morphology was not theorized. We show that uncertainty quantification using McMC can proceed in the reduced dimensionality space while accounting for the
Parameterization of general Z-γ-Z' mixing in an electroweak chiral theory
International Nuclear Information System (INIS)
Zhang Ying; Wang Qing
2012-01-01
A new general parameterization with eight mixing parameters among Z, γ and an extra neutral gauge boson Z ' is proposed and subjected to phenomenological analysis. We show that in addition to the conventional Weinberg angle θ W , there are seven other phenomenological parameters, G ' , ξ, η, θ 1 , θ r , r and l, for the most general Z-γ-Z ' mixings, in which parameter G ' arises due to the presence of an extra Stueckelbergtype mass coupling. Combined with the conventional Z-Z ' mass mixing angle 0', the remaining six parameters, ξ, η, θ l -θ ' , θ r - θ ' , r and l, are caused by general kinetic mixing. In all eight phenomenological parameters, θ W , G ' , ξ, η, θ 1 , θ r , r and l, we can determine the Z-Z ' mass mixing angle θ ' and the mass ratio M Z /M Z ' . The Z-γ-Z ' mixing that we discuss are based on the model-independent description of the extended electroweak chiral Lagrangian (EWCL) previously proposed by us. In addition, we show that there are eight corresponding independent theoretical coefficients in our EWCL, which are fully fixed by our eight phenomenological mixing parameters. We further find that the experimental measurability of these eight parameters does not rely on the extended neutral current for Z ' , but depends on the Z-Z ' mass ratio. (authors)
Following the examination and evaluation of 12 nucleation parameterizations presented in part 1, 11 of them representing binary, ternary, kinetic, and cluster‐activated nucleation theories are evaluated in the U.S. Environmental Protection Agency Community Multiscale Air Quality ...
Nitrous Oxide Emissions from Biofuel Crops and Parameterization in the EPIC Biogeochemical Model
This presentation describes year 1 field measurements of N2O fluxes and crop yields which are used to parameterize the EPIC biogeochemical model for the corresponding field site. Initial model simulations are also presented.
Energy Technology Data Exchange (ETDEWEB)
Zhang, Guang J. [Univ. of California, San Diego, CA (United States)
2016-11-07
The fundamental scientific objectives of our research are to use ARM observations and the NCAR CAM5 to understand the large-scale control on convection, and to develop improved convection and cloud parameterizations for use in GCMs.
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D. Barahona
2009-01-01
Full Text Available We present a parameterization of cirrus cloud formation that computes the ice crystal number and size distribution under the presence of homogeneous and heterogeneous freezing. The parameterization is very simple to apply and is derived from the analytical solution of the cloud parcel equations, assuming that the ice nuclei population is monodisperse and chemically homogeneous. In addition to the ice distribution, an analytical expression is provided for the limiting ice nuclei number concentration that suppresses ice formation from homogeneous freezing. The parameterization is evaluated against a detailed numerical parcel model, and reproduces numerical simulations over a wide range of conditions with an average error of 6±33%. The parameterization also compares favorably against other formulations that require some form of numerical integration.
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N. Romano
2011-12-01
Full Text Available We investigate the potential impact of accounting for seasonal variations in the climatic forcing and using different methods to parameterize the soil water content at field capacity on the water balance components computed by a bucket model (BM. The single-layer BM of Guswa et al. (2002 is employed, whereas the Richards equation (RE based Soil Water Atmosphere Plant (SWAP model is used as a benchmark model. The results are analyzed for two differently-textured soils and for some synthetic runs under real-like seasonal weather conditions, using stochastically-generated daily rainfall data for a period of 100 years. Since transient soil-moisture dynamics and climatic seasonality play a key role in certain zones of the World, such as in Mediterranean land areas, a specific feature of this study is to test the prediction capability of the bucket model under a condition where seasonal variations in rainfall are not in phase with the variations in plant transpiration. Reference is made to a hydrologic year in which we have a rainy period (starting 1 November and lasting 151 days where vegetation is basically assumed in a dormant stage, followed by a drier and rainless period with a vegetation regrowth phase. Better agreement between BM and RE-SWAP intercomparison results are obtained when BM is parameterized by a field capacity value determined through the drainage method proposed by Romano and Santini (2002. Depending on the vegetation regrowth or dormant seasons, rainfall variability within a season results in transpiration regimes and soil moisture fluctuations with distinctive features. During the vegetation regrowth season, transpiration exerts a key control on soil water budget with respect to rainfall. During the dormant season of vegetation, the precipitation regime becomes an important climate forcing. Simulations also highlight the occurrence of bimodality in the probability distribution of soil moisture during the season when plants are
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P. Otero
2013-05-01
Full Text Available The estimation of sea–air CO2 fluxes is largely dependent on wind speed through the gas transfer velocity parameterization. In this paper, we quantify uncertainties in the estimation of the CO2 uptake in the Bay of Biscay resulting from the use of different sources of wind speed such as three different global reanalysis meteorological models (NCEP/NCAR 1, NCEP/DOE 2 and ERA-Interim, one high-resolution regional forecast model (HIRLAM-AEMet, winds derived under the Cross-Calibrated Multi-Platform (CCMP project, and QuikSCAT winds in combination with some of the most widely used gas transfer velocity parameterizations. Results show that net CO2 flux estimations during an entire seasonal cycle (September 2002–September 2003 may vary by a factor of ~ 3 depending on the selected wind speed product and the gas exchange parameterization, with the highest impact due to the last one. The comparison of satellite- and model-derived winds with observations at buoys advises against the systematic overestimation of NCEP-2 and the underestimation of NCEP-1. In the coastal region, the presence of land and the time resolution are the main constraints of QuikSCAT, which turns CCMP and ERA-Interim in the preferred options.
He, Cenlin; Liou, Kuo-Nan; Takano, Yoshi; Yang, Ping; Qi, Ling; Chen, Fei
2018-01-01
We quantify the effects of grain shape and multiple black carbon (BC)-snow internal mixing on snow albedo by explicitly resolving shape and mixing structures. Nonspherical snow grains tend to have higher albedos than spheres with the same effective sizes, while the albedo difference due to shape effects increases with grain size, with up to 0.013 and 0.055 for effective radii of 1,000 μm at visible and near-infrared bands, respectively. BC-snow internal mixing reduces snow albedo at wavelengths external mixing, internal mixing enhances snow albedo reduction by a factor of 1.2-2.0 at visible wavelengths depending on BC concentration and snow shape. The opposite effects on albedo reductions due to snow grain nonsphericity and BC-snow internal mixing point toward a careful investigation of these two factors simultaneously in climate modeling. We further develop parameterizations for snow albedo and its reduction by accounting for grain shape and BC-snow internal/external mixing. Combining the parameterizations with BC-in-snow measurements in China, North America, and the Arctic, we estimate that nonspherical snow grains reduce BC-induced albedo radiative effects by up to 50% compared with spherical grains. Moreover, BC-snow internal mixing enhances the albedo effects by up to 30% (130%) for spherical (nonspherical) grains relative to external mixing. The overall uncertainty induced by snow shape and BC-snow mixing state is about 21-32%.
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M. Zampieri
2005-01-01
Full Text Available The 'Montserrat-2000' severe flash flood event which occurred over Catalonia on 9 and 10 June 2000 is analyzed. Strong precipitation was generated by a mesoscale convective system associated with the development of a cyclone. The location of heavy precipitation depends on the position of the cyclone, which, in turn, is found to be very sensitive to various model characteristics and initial conditions. Numerical simulations of this case study using the hydrostatic BOLAM and the non-hydrostatic MOLOCH models are performed in order to test the effects of different formulations of the boundary layer parameterization: a modified version of the Louis (order 1 model and a custom version of the E-ℓ (order 1.5 model. Both of them require a diagnostic formulation of the mixing length, but the use of the turbulent kinetic energy equation in the E-ℓ model allows to represent turbulence history and non-locality effects and to formulate a more physically based mixing length. The impact of the two schemes is different in the two models. The hydrostatic model, run at 1/5 degree resolution, is less sensitive, but the quantitative precipitation forecast is in any case unsatisfactory in terms of localization and amount. Conversely, the non-hydrostatic model, run at 1/50 degree resolution, is capable of realistically simulate timing, position and amount of precipitation, with the apparently superior results obtained with the E-ℓ parameterization model.
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A. Endalamaw
2017-09-01
Full Text Available Modeling hydrological processes in the Alaskan sub-arctic is challenging because of the extreme spatial heterogeneity in soil properties and vegetation communities. Nevertheless, modeling and predicting hydrological processes is critical in this region due to its vulnerability to the effects of climate change. Coarse-spatial-resolution datasets used in land surface modeling pose a new challenge in simulating the spatially distributed and basin-integrated processes since these datasets do not adequately represent the small-scale hydrological, thermal, and ecological heterogeneity. The goal of this study is to improve the prediction capacity of mesoscale to large-scale hydrological models by introducing a small-scale parameterization scheme, which better represents the spatial heterogeneity of soil properties and vegetation cover in the Alaskan sub-arctic. The small-scale parameterization schemes are derived from observations and a sub-grid parameterization method in the two contrasting sub-basins of the Caribou Poker Creek Research Watershed (CPCRW in Interior Alaska: one nearly permafrost-free (LowP sub-basin and one permafrost-dominated (HighP sub-basin. The sub-grid parameterization method used in the small-scale parameterization scheme is derived from the watershed topography. We found that observed soil thermal and hydraulic properties – including the distribution of permafrost and vegetation cover heterogeneity – are better represented in the sub-grid parameterization method than the coarse-resolution datasets. Parameters derived from the coarse-resolution datasets and from the sub-grid parameterization method are implemented into the variable infiltration capacity (VIC mesoscale hydrological model to simulate runoff, evapotranspiration (ET, and soil moisture in the two sub-basins of the CPCRW. Simulated hydrographs based on the small-scale parameterization capture most of the peak and low flows, with similar accuracy in both sub
Parameterization of pion production and reaction cross sections at LAMPF energies
International Nuclear Information System (INIS)
Burman, R.L.; Smith, E.S.
1989-05-01
A parameterization of pion production and reaction cross sections is developed for eventual use in modeling neutrino production by protons in a beam stop. Emphasis is placed upon smooth parameterizations for proton energies up to 800 MeV, for all pion energies and angles, and for a wide range of materials. The resulting representations of the data are well-behaved and can be used for extrapolation to regions where there are no measurements. 22 refs., 16 figs., 2 tabs
A scheme for parameterizing ice cloud water content in general circulation models
Heymsfield, Andrew J.; Donner, Leo J.
1989-01-01
A method for specifying ice water content in GCMs is developed, based on theory and in-cloud measurements. A theoretical development of the conceptual precipitation model is given and the aircraft flights used to characterize the ice mass distribution in deep ice clouds is discussed. Ice water content values derived from the theoretical parameterization are compared with the measured values. The results demonstrate that a simple parameterization for atmospheric ice content can account for ice contents observed in several synoptic contexts.
Tsang, Yue-Kin; Vallis, Geoffrey K.
2018-01-01
In this paper we describe the construction of an efficient probabilistic parameterization that could be used in a coarse-resolution numerical model in which the variation of moisture is not properly resolved. An Eulerian model using a coarse-grained field on a grid cannot properly resolve regions of saturation---in which condensation occurs---that are smaller than the grid boxes. Thus, in the absence of a parameterization scheme, either the grid box must become saturated or condensation will ...
A parameterization for the absorption of solar radiation by water vapor in the earth's atmosphere
Wang, W.-C.
1976-01-01
A parameterization for the absorption of solar radiation as a function of the amount of water vapor in the earth's atmosphere is obtained. Absorption computations are based on the Goody band model and the near-infrared absorption band data of Ludwig et al. A two-parameter Curtis-Godson approximation is used to treat the inhomogeneous atmosphere. Heating rates based on a frequently used one-parameter pressure-scaling approximation are also discussed and compared with the present parameterization.
A simple parameterization for the rising velocity of bubbles in a liquid pool
Energy Technology Data Exchange (ETDEWEB)
Park, Sung Hoon [Dept. of Environmental Engineering, Sunchon National University, Suncheon (Korea, Republic of); Park, Chang Hwan; Lee, Jin Yong; Lee, Byung Chul [FNC Technology, Co., Ltd., Yongin (Korea, Republic of)
2017-06-15
The determination of the shape and rising velocity of gas bubbles in a liquid pool is of great importance in analyzing the radioactive aerosol emissions from nuclear power plant accidents in terms of the fission product release rate and the pool scrubbing efficiency of radioactive aerosols. This article suggests a simple parameterization for the gas bubble rising velocity as a function of the volume-equivalent bubble diameter; this parameterization does not require prior knowledge of bubble shape. This is more convenient than previously suggested parameterizations because it is given as a single explicit formula. It is also shown that a bubble shape diagram, which is very similar to the Grace's diagram, can be easily generated using the parameterization suggested in this article. Furthermore, the boundaries among the three bubble shape regimes in the E{sub o}–R{sub e} plane and the condition for the bypass of the spheroidal regime can be delineated directly from the parameterization formula. Therefore, the parameterization suggested in this article appears to be useful not only in easily determining the bubble rising velocity (e.g., in postulated severe accident analysis codes) but also in understanding the trend of bubble shape change due to bubble growth.
A review of the theoretical basis for bulk mass flux convective parameterization
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R. S. Plant
2010-04-01
Full Text Available Most parameterizations for precipitating convection in use today are bulk schemes, in which an ensemble of cumulus elements with different properties is modelled as a single, representative entraining-detraining plume. We review the underpinning mathematical model for such parameterizations, in particular by comparing it with spectral models in which elements are not combined into the representative plume. The chief merit of a bulk model is that the representative plume can be described by an equation set with the same structure as that which describes each element in a spectral model. The equivalence relies on an ansatz for detrained condensate introduced by Yanai et al. (1973 and on a simplified microphysics. There are also conceptual differences in the closure of bulk and spectral parameterizations. In particular, we show that the convective quasi-equilibrium closure of Arakawa and Schubert (1974 for spectral parameterizations cannot be carried over to a bulk parameterization in a straightforward way. Quasi-equilibrium of the cloud work function assumes a timescale separation between a slow forcing process and a rapid convective response. But, for the natural bulk analogue to the cloud-work function, the relevant forcing is characterised by a different timescale, and so its quasi-equilibrium entails a different physical constraint. Closures of bulk parameterizations that use a parcel value of CAPE do not suffer from this timescale issue. However, the Yanai et al. (1973 ansatz must be invoked as a necessary ingredient of those closures.
A simple parameterization for the rising velocity of bubbles in a liquid pool
International Nuclear Information System (INIS)
Park, Sung Hoon; Park, Chang Hwan; Lee, Jin Yong; Lee, Byung Chul
2017-01-01
The determination of the shape and rising velocity of gas bubbles in a liquid pool is of great importance in analyzing the radioactive aerosol emissions from nuclear power plant accidents in terms of the fission product release rate and the pool scrubbing efficiency of radioactive aerosols. This article suggests a simple parameterization for the gas bubble rising velocity as a function of the volume-equivalent bubble diameter; this parameterization does not require prior knowledge of bubble shape. This is more convenient than previously suggested parameterizations because it is given as a single explicit formula. It is also shown that a bubble shape diagram, which is very similar to the Grace's diagram, can be easily generated using the parameterization suggested in this article. Furthermore, the boundaries among the three bubble shape regimes in the E_o–R_e plane and the condition for the bypass of the spheroidal regime can be delineated directly from the parameterization formula. Therefore, the parameterization suggested in this article appears to be useful not only in easily determining the bubble rising velocity (e.g., in postulated severe accident analysis codes) but also in understanding the trend of bubble shape change due to bubble growth
Parameterized Disturbance Observer Based Controller to Reduce Cyclic Loads of Wind Turbine
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Raja M. Imran
2018-05-01
Full Text Available This paper is concerned with bump-less transfer of parameterized disturbance observer based controller with individual pitch control strategy to reduce cyclic loads of wind turbine in full load operation. Cyclic loads are generated due to wind shear and tower shadow effects. Multivariable disturbance observer based linear controllers are designed with objective to reduce output power fluctuation, tower oscillation and drive-train torsion using optimal control theory. Linear parameterized controllers are designed by using a smooth scheduling mechanism between the controllers. The proposed parameterized controller with individual pitch was tested on nonlinear Fatigue, Aerodynamics, Structures, and Turbulence (FAST code model of National Renewable Energy Laboratory (NREL’s 5 MW wind turbine. The closed-loop system performance was assessed by comparing the simulation results of proposed controller with a fixed gain and parameterized controller with collective pitch for full load operation of wind turbine. Simulations are performed with step wind to see the behavior of the system with wind shear and tower shadow effects. Then, turbulent wind is applied to see the smooth transition of the controllers. It can be concluded from the results that the proposed parameterized control shows smooth transition from one controller to another controller. Moreover, 3p and 6p harmonics are well mitigated as compared to fixed gain DOBC and parameterized DOBC with collective pitch.
Pincus, R.; Mlawer, E. J.
2017-12-01
Radiation is key process in numerical models of the atmosphere. The problem is well-understood and the parameterization of radiation has seen relatively few conceptual advances in the past 15 years. It is nonthelss often the single most expensive component of all physical parameterizations despite being computed less frequently than other terms. This combination of cost and maturity suggests value in a single radiation parameterization that could be shared across models; devoting effort to a single parameterization might allow for fine tuning for efficiency. The challenge lies in the coupling of this parameterization to many disparate representations of clouds and aerosols. This talk will describe RRTMGP, a new radiation parameterization that seeks to balance efficiency and flexibility. This balance is struck by isolating computational tasks in "kernels" that expose as much fine-grained parallelism as possible. These have simple interfaces and are interoperable across programming languages so that they might be repalced by alternative implementations in domain-specific langauges. Coupling to the host model makes use of object-oriented features of Fortran 2003, minimizing branching within the kernels and the amount of data that must be transferred. We will show accuracy and efficiency results for a globally-representative set of atmospheric profiles using a relatively high-resolution spectral discretization.
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E. S. Belenkaya
2007-06-01
Full Text Available We study the dependence of Saturn's magnetospheric magnetic field structure on the interplanetary magnetic field (IMF, together with the corresponding variations of the open-closed field line boundary in the ionosphere. Specifically we investigate the interval from 8 to 30 January 2004, when UV images of Saturn's southern aurora were obtained by the Hubble Space Telescope (HST, and simultaneous interplanetary measurements were provided by the Cassini spacecraft located near the ecliptic ~0.2 AU upstream of Saturn and ~0.5 AU off the planet-Sun line towards dawn. Using the paraboloid model of Saturn's magnetosphere, we calculate the magnetospheric magnetic field structure for several values of the IMF vector representative of interplanetary compression regions. Variations in the magnetic structure lead to different shapes and areas of the open field line region in the ionosphere. Comparison with the HST auroral images shows that the area of the computed open flux region is generally comparable to that enclosed by the auroral oval, and sometimes agrees in detail with its poleward boundary, though more typically being displaced by a few degrees in the tailward direction.
Mogensen, Ditte; Aaltonen, Hermanni; Aalto, Juho; Bäck, Jaana; Kieloaho, Antti-Jussi; Gierens, Rosa; Smolander, Sampo; Kulmala, Markku; Boy, Michael
2015-04-01
Volatile organic compounds (VOCs) are emitted from the biosphere and can work as precursor gases for aerosol particles that can affect the climate (e.g. Makkonen et al., ACP, 2012). VOC emissions from needles and leaves have gained the most attention, however other parts of the ecosystem also have the ability to emit a vast amount of VOCs. This, often neglected, source can be important e.g. at periods where leaves are absent. Both sources and drivers related to forest floor emission of VOCs are currently limited. It is thought that the sources are mainly due to degradation of organic matter (Isidorov and Jdanova, Chemosphere, 2002), living roots (Asensio et al., Soil Biol. Biochem., 2008) and ground vegetation. The drivers are biotic (e.g. microbes) and abiotic (e.g. temperature and moisture). However, the relative importance of the sources and the drivers individually are currently poorly understood. Further, the relative importance of these factors is highly dependent on the tree species occupying the area of interest. The emission of isoprene and monoterpenes where measured from the boreal forest floor at the SMEAR II station in Southern Finland (Hari and Kulmala, Boreal Env. Res., 2005) during the snow-free period in 2010-2012. We used a dynamic method with 3 automated chambers analyzed by Proton Transfer Reaction - Mass Spectrometer (Aaltonen et al., Plant Soil, 2013). Using this data, we have developed empirical parameterizations for the emission of isoprene and monoterpenes from the forest floor. These parameterizations depends on abiotic factors, however, since the parameterizations are based on field measurements, biotic features are captured. Further, we have used the 1D chemistry-transport model SOSAA (Boy et al., ACP, 2011) to test the seasonal relative importance of inclusion of these parameterizations of the forest floor compared to the canopy crown emissions, on the atmospheric reactivity throughout the canopy.
Parameterization of a ruminant model of phosphorus digestion and metabolism.
Feng, X; Knowlton, K F; Hanigan, M D
2015-10-01
The objective of the current work was to parameterize the digestive elements of the model of Hill et al. (2008) using data collected from animals that were ruminally, duodenally, and ileally cannulated, thereby providing a better understanding of the digestion and metabolism of P fractions in growing and lactating cattle. The model of Hill et al. (2008) was fitted and evaluated for adequacy using the data from 6 animal studies. We hypothesized that sufficient data would be available to estimate P digestion and metabolism parameters and that these parameters would be sufficient to derive P bioavailabilities of a range of feed ingredients. Inputs to the model were dry matter intake; total feed P concentration (fPtFd); phytate (Pp), organic (Po), and inorganic (Pi) P as fractions of total P (fPpPt, fPoPt, fPiPt); microbial growth; amount of Pi and Pp infused into the omasum or ileum; milk yield; and BW. The available data were sufficient to derive all model parameters of interest. The final model predicted that given 75 g/d of total P input, the total-tract digestibility of P was 40.8%, Pp digestibility in the rumen was 92.4%, and in the total-tract was 94.7%. Blood P recycling to the rumen was a major source of Pi flow into the small intestine, and the primary route of excretion. A large proportion of Pi flowing to the small intestine was absorbed; however, additional Pi was absorbed from the large intestine (3.15%). Absorption of Pi from the small intestine was regulated, and given the large flux of salivary P recycling, the effective fractional small intestine absorption of available P derived from the diet was 41.6% at requirements. Milk synthesis used 16% of total absorbed P, and less than 1% was excreted in urine. The resulting model could be used to derive P bioavailabilities of commonly used feedstuffs in cattle production. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
Povinelli, Daniel J.; Reaux, James E.; Frey, Scott H.
2010-01-01
Considerable attention has been devoted to behaviors in which tools are used to perform actions in extrapersonal space by extending the reach. Evidence suggests that these behaviors result in an expansion of the body schema and peripersonal space. However, humans often use tools to perform tasks within peripersonal space that cannot be…
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K. Zhang
2013-05-01
Full Text Available This study uses aircraft measurements of relative humidity and ice crystal size distribution collected during the SPARTICUS (Small PARTicles In CirrUS field campaign to evaluate and constrain ice cloud parameterizations in the Community Atmosphere Model version 5. About 200 h of data were collected during the campaign between January and June 2010, providing the longest aircraft measurements available so far for cirrus clouds in the midlatitudes. The probability density function (PDF of ice crystal number concentration (Ni derived from the high-frequency (1 Hz measurements features a strong dependence on ambient temperature. As temperature decreases from −35 °C to −62 °C, the peak in the PDF shifts from 10–20 L−1 to 200–1000 L−1, while Ni shows a factor of 6–7 increase. Model simulations are performed with two different ice nucleation schemes for pure ice-phase clouds. One of the schemes can reproduce a clear increase of Ni with decreasing temperature by using either an observation-based ice nuclei spectrum or a classical-theory-based spectrum with a relatively low (5–10% maximum freezing ratio for dust aerosols. The simulation with the other scheme, which assumes a high maximum freezing ratio (100%, shows much weaker temperature dependence of Ni. Simulations are also performed to test empirical parameters related to water vapor deposition and the autoconversion of ice crystals to snow. Results show that a value between 0.05 and 0.1 for the water vapor deposition coefficient, and 250 μm for the critical diameter that distinguishes ice crystals from snow, can produce good agreement between model simulation and the SPARTICUS measurements in terms of Ni and effective radius. The climate impact of perturbing these parameters is also discussed.
Rodó, Xavier; Rodríguez-Arias, Miquel-Àngel
2006-10-01
The study of transitory signals and local variability structures in both/either time and space and their role as sources of climatic memory, is an important but often neglected topic in climate research despite its obvious importance and extensive coverage in the literature. Transitory signals arise either from non-linearities, in the climate system, transitory atmosphere-ocean couplings, and other processes in the climate system evolving after a critical threshold is crossed. These temporary interactions that, though intense, may not last long, can be responsible for a large amount of unexplained variability but are normally considered of limited relevance and often, discarded. With most of the current techniques at hand these typology of signatures are difficult to isolate because the low signal-to-noise ratio in midlatitudes, the limited recurrence of the transitory signals during a customary interval of data considered. Also, there is often a serious problem arising from the smoothing of local or transitory processes if statistical techniques are applied, that consider all the length of data available, rather than taking into account the size of the specific variability structure under investigation. Scale-dependent correlation (SDC) analysis is a new statistical method capable of highlighting the presence of transitory processes, these former being understood as temporary significant lag-dependent autocovariance in a single series, or covariance structures between two series. This approach, therefore, complements other approaches such as those resulting from the families of wavelet analysis, singular-spectrum analysis and recurrence plots. A main feature of SDC is its high-performance for short time series, its ability to characterize phase-relationships and thresholds in the bivariate domain. Ultimately, SDC helps tracking short-lagged relationships among processes that locally or temporarily couple and uncouple. The use of SDC is illustrated in the present
Impact of cloud parameterization on the numerical simulation of a super cyclone
Energy Technology Data Exchange (ETDEWEB)
Deshpande, M.S.; Pattnaik, S.; Salvekar, P.S. [Indian Institute of Tropical Meteorology, Pune (India)
2012-07-01
This study examines the role of parameterization of convection and explicit moisture processes on the simulated track, intensity and inner core structure of Orissa super cyclone (1999) in Bay of Bengal (north Indian Ocean). Sensitivity experiments are carried out to examine the impact of cumulus parameterization schemes (CPS) using MM5 model (Version 3.7) in a two-way nested domain (D1 and D2) configuration at horizontal resolutions (45-15 km). Three different cumulus parameterization schemes, namely Grell (Gr), Betts-Miller (BM) and updated Kain Fritsch (KF2), are tested. It is noted that track and intensity both are very sensitive to CPS and comparatively, KF2 predicts them reasonably well. Particularly, the rapid intensification phase of the super cyclone is best simulated by KF2 compared to other CPS. To examine the effect of the cumulus parameterization scheme at high resolution (5 km), the three-domain configuration (45-15-5 km resolution) is utilized. Based on initial results, KF2 scheme is used for both the domains (D1 and D2). Two experiments are conducted: one in which KF2 is used as CPS and another in which no CPS is used in the third domain. The intensity is well predicted when no CPS is used in the innermost domain. The sensitivity experiments are also carried out to examine the impact from microphysics parameterization schemes (MPS). Four cloud microphysics parameterization schemes, namely mixed phase (MP), Goddard microphysics with Graupel (GG), Reisner Graupel (RG) and Schultz (Sc), are tested in these experiments. It is noted that the tropical cyclone tracks and intensity variation have considerable sensitivity to the varying cloud microphysical parameterization schemes. The MPS of MP and Sc could very well capture the rapid intensification phase. The final intensity is well predicted by MP, which is overestimated by Sc. The MPS of GG and RG underestimates the intensity. (orig.)
Loughner, Christopher P.; Allen, Dale J.; Zhang, Da-Lin; Pickering, Kenneth E.; Dickerson, Russell R.; Landry, Laura
2012-01-01
Urban heat island (UHI) effects can strengthen heat waves and air pollution episodes. In this study, the dampening impact of urban trees on the UHI during an extreme heat wave in the Washington, D.C., and Baltimore, Maryland, metropolitan area is examined by incorporating trees, soil, and grass into the coupled Weather Research and Forecasting model and an urban canopy model (WRF-UCM). By parameterizing the effects of these natural surfaces alongside roadways and buildings, the modified WRF-UCM is used to investigate how urban trees, soil, and grass dampen the UHI. The modified model was run with 50% tree cover over urban roads and a 10% decrease in the width of urban streets to make space for soil and grass alongside the roads and buildings. Results show that, averaged over all urban areas, the added vegetation decreases surface air temperature in urban street canyons by 4.1 K and road-surface and building-wall temperatures by 15.4 and 8.9 K, respectively, as a result of tree shading and evapotranspiration. These temperature changes propagate downwind and alter the temperature gradient associated with the Chesapeake Bay breeze and, therefore, alter the strength of the bay breeze. The impact of building height on the UHI shows that decreasing commercial building heights by 8 m and residential building heights by 2.5 m results in up to 0.4-K higher daytime surface and near-surface air temperatures because of less building shading and up to 1.2-K lower nighttime temperatures because of less longwave radiative trapping in urban street canyons.
3D surface parameterization using manifold learning for medial shape representation
Ward, Aaron D.; Hamarneh, Ghassan
2007-03-01
The choice of 3D shape representation for anatomical structures determines the effectiveness with which segmentation, visualization, deformation, and shape statistics are performed. Medial axis-based shape representations have attracted considerable attention due to their inherent ability to encode information about the natural geometry of parts of the anatomy. In this paper, we propose a novel approach, based on nonlinear manifold learning, to the parameterization of medial sheets and object surfaces based on the results of skeletonization. For each single-sheet figure in an anatomical structure, we skeletonize the figure, and classify its surface points according to whether they lie on the upper or lower surface, based on their relationship to the skeleton points. We then perform nonlinear dimensionality reduction on the skeleton, upper, and lower surface points, to find the intrinsic 2D coordinate system of each. We then center a planar mesh over each of the low-dimensional representations of the points, and map the meshes back to 3D using the mappings obtained by manifold learning. Correspondence between mesh vertices, established in their intrinsic 2D coordinate spaces, is used in order to compute the thickness vectors emanating from the medial sheet. We show results of our algorithm on real brain and musculoskeletal structures extracted from MRI, as well as an artificial multi-sheet example. The main advantages to this method are its relative simplicity and noniterative nature, and its ability to correctly compute nonintersecting thickness vectors for a medial sheet regardless of both the amount of coincident bending and thickness in the object, and of the incidence of local concavities and convexities in the object's surface.
Firl, G. J.; Randall, D. A.
2013-12-01
The so-called "assumed probability density function (PDF)" approach to subgrid-scale (SGS) parameterization has shown to be a promising method for more accurately representing boundary layer cloudiness under a wide range of conditions. A new parameterization has been developed, named the Two-and-a-Half ORder closure (THOR), that combines this approach with a higher-order turbulence closure. THOR predicts the time evolution of the turbulence kinetic energy components, the variance of ice-liquid water potential temperature (θil) and total non-precipitating water mixing ratio (qt) and the covariance between the two, and the vertical fluxes of horizontal momentum, θil, and qt. Ten corresponding third-order moments in addition to the skewnesses of θil and qt are calculated using diagnostic functions assuming negligible time tendencies. The statistical moments are used to define a trivariate double Gaussian PDF among vertical velocity, θil, and qt. The first three statistical moments of each variable are used to estimate the two Gaussian plume means, variances, and weights. Unlike previous similar models, plume variances are not assumed to be equal or zero. Instead, they are parameterized using the idea that the less dominant Gaussian plume (typically representing the updraft-containing portion of a grid cell) has greater variance than the dominant plume (typically representing the "environmental" or slowly subsiding portion of a grid cell). Correlations among the three variables are calculated using the appropriate covariance moments, and both plume correlations are assumed to be equal. The diagnosed PDF in each grid cell is used to calculate SGS condensation, SGS fluxes of cloud water species, SGS buoyancy terms, and to inform other physical parameterizations about SGS variability. SGS condensation is extended from previous similar models to include condensation over both liquid and ice substrates, dependent on the grid cell temperature. Implementations have been
Khan, Tanvir R.; Perlinger, Judith A.
2017-10-01
Despite considerable effort to develop mechanistic dry particle deposition parameterizations for atmospheric transport models, current knowledge has been inadequate to propose quantitative measures of the relative performance of available parameterizations. In this study, we evaluated the performance of five dry particle deposition parameterizations developed by Zhang et al. (2001) (Z01), Petroff and Zhang (2010) (PZ10), Kouznetsov and Sofiev (2012) (KS12), Zhang and He (2014) (ZH14), and Zhang and Shao (2014) (ZS14), respectively. The evaluation was performed in three dimensions: model ability to reproduce observed deposition velocities, Vd (accuracy); the influence of imprecision in input parameter values on the modeled Vd (uncertainty); and identification of the most influential parameter(s) (sensitivity). The accuracy of the modeled Vd was evaluated using observations obtained from five land use categories (LUCs): grass, coniferous and deciduous forests, natural water, and ice/snow. To ascertain the uncertainty in modeled Vd, and quantify the influence of imprecision in key model input parameters, a Monte Carlo uncertainty analysis was performed. The Sobol' sensitivity analysis was conducted with the objective to determine the parameter ranking from the most to the least influential. Comparing the normalized mean bias factors (indicators of accuracy), we find that the ZH14 parameterization is the most accurate for all LUCs except for coniferous forest, for which it is second most accurate. From Monte Carlo simulations, the estimated mean normalized uncertainties in the modeled Vd obtained for seven particle sizes (ranging from 0.005 to 2.5 µm) for the five LUCs are 17, 12, 13, 16, and 27 % for the Z01, PZ10, KS12, ZH14, and ZS14 parameterizations, respectively. From the Sobol' sensitivity results, we suggest that the parameter rankings vary by particle size and LUC for a given parameterization. Overall, for dp = 0.001 to 1.0 µm, friction velocity was one of
Directory of Open Access Journals (Sweden)
T. R. Khan
2017-10-01
Full Text Available Despite considerable effort to develop mechanistic dry particle deposition parameterizations for atmospheric transport models, current knowledge has been inadequate to propose quantitative measures of the relative performance of available parameterizations. In this study, we evaluated the performance of five dry particle deposition parameterizations developed by Zhang et al. (2001 (Z01, Petroff and Zhang (2010 (PZ10, Kouznetsov and Sofiev (2012 (KS12, Zhang and He (2014 (ZH14, and Zhang and Shao (2014 (ZS14, respectively. The evaluation was performed in three dimensions: model ability to reproduce observed deposition velocities, Vd (accuracy; the influence of imprecision in input parameter values on the modeled Vd (uncertainty; and identification of the most influential parameter(s (sensitivity. The accuracy of the modeled Vd was evaluated using observations obtained from five land use categories (LUCs: grass, coniferous and deciduous forests, natural water, and ice/snow. To ascertain the uncertainty in modeled Vd, and quantify the influence of imprecision in key model input parameters, a Monte Carlo uncertainty analysis was performed. The Sobol' sensitivity analysis was conducted with the objective to determine the parameter ranking from the most to the least influential. Comparing the normalized mean bias factors (indicators of accuracy, we find that the ZH14 parameterization is the most accurate for all LUCs except for coniferous forest, for which it is second most accurate. From Monte Carlo simulations, the estimated mean normalized uncertainties in the modeled Vd obtained for seven particle sizes (ranging from 0.005 to 2.5 µm for the five LUCs are 17, 12, 13, 16, and 27 % for the Z01, PZ10, KS12, ZH14, and ZS14 parameterizations, respectively. From the Sobol' sensitivity results, we suggest that the parameter rankings vary by particle size and LUC for a given parameterization. Overall, for dp = 0.001 to 1.0
White, Jeremy; Stengel, Victoria; Rendon, Samuel; Banta, John
2017-08-01
Computer models of hydrologic systems are frequently used to investigate the hydrologic response of land-cover change. If the modeling results are used to inform resource-management decisions, then providing robust estimates of uncertainty in the simulated response is an important consideration. Here we examine the importance of parameterization, a necessarily subjective process, on uncertainty estimates of the simulated hydrologic response of land-cover change. Specifically, we applied the soil water assessment tool (SWAT) model to a 1.4 km2 watershed in southern Texas to investigate the simulated hydrologic response of brush management (the mechanical removal of woody plants), a discrete land-cover change. The watershed was instrumented before and after brush-management activities were undertaken, and estimates of precipitation, streamflow, and evapotranspiration (ET) are available; these data were used to condition and verify the model. The role of parameterization in brush-management simulation was evaluated by constructing two models, one with 12 adjustable parameters (reduced parameterization) and one with 1305 adjustable parameters (full parameterization). Both models were subjected to global sensitivity analysis as well as Monte Carlo and generalized likelihood uncertainty estimation (GLUE) conditioning to identify important model inputs and to estimate uncertainty in several quantities of interest related to brush management. Many realizations from both parameterizations were identified as behavioral in that they reproduce daily mean streamflow acceptably well according to Nash-Sutcliffe model efficiency coefficient, percent bias, and coefficient of determination. However, the total volumetric ET difference resulting from simulated brush management remains highly uncertain after conditioning to daily mean streamflow, indicating that streamflow data alone are not sufficient to inform the model inputs that influence the simulated outcomes of brush management
On parameterization of the inverse problem for estimating aquifer properties using tracer data
International Nuclear Information System (INIS)
Kowalsky, M. B.; Finsterle, Stefan A.; Williams, Kenneth H.; Murray, Christopher J.; Commer, Michael; Newcomer, Darrell R.; Englert, Andreas L.; Steefel, Carl I.; Hubbard, Susan
2012-01-01
We consider a field-scale tracer experiment conducted in 2007 in a shallow uranium-contaminated aquifer at Rifle, Colorado. In developing a reliable approach for inferring hydrological properties at the site through inverse modeling of the tracer data, decisions made on how to parameterize heterogeneity (i.e., how to represent a heterogeneous distribution using a limited number of parameters that are amenable to estimation) are of paramount importance. We present an approach for hydrological inversion of the tracer data and explore, using a 2D synthetic example at first, how parameterization affects the solution, and how additional characterization data could be incorporated to reduce uncertainty. Specifically, we examine sensitivity of the results to the configuration of pilot points used in a geostatistical parameterization, and to the sampling frequency and measurement error of the concentration data. A reliable solution of the inverse problem is found when the pilot point configuration is carefully implemented. In addition, we examine the use of a zonation parameterization, in which the geometry of the geological facies is known (e.g., from geophysical data or core data), to reduce the non-uniqueness of the solution and the number of unknown parameters to be estimated. When zonation information is only available for a limited region, special treatment in the remainder of the model is necessary, such as using a geostatistical parameterization. Finally, inversion of the actual field data is performed using 2D and 3D models, and results are compared with slug test data.
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Koenigk, Torben; Caian, Mihaela; Doescher, Ralf; Wyser, Klaus [Swedish Meteorological and Hydrological Institute, Rossby Centre, Norrkoeping (Sweden); Koenig Beatty, Christof [Universite Catholique de Louvain, Louvain-la-Neuve (Belgium)
2012-06-15
Decadal prediction is one focus of the upcoming 5th IPCC Assessment report. To be able to interpret the results and to further improve the decadal predictions it is important to investigate the potential predictability in the participating climate models. This study analyzes the upper limit of climate predictability on decadal time scales and its dependency on sea ice albedo parameterization by performing two perfect ensemble experiments with the global coupled climate model EC-Earth. In the first experiment, the standard albedo formulation of EC-Earth is used, in the second experiment sea ice albedo is reduced. The potential prognostic predictability is analyzed for a set of oceanic and atmospheric parameters. The decadal predictability of the atmospheric circulation is small. The highest potential predictability was found in air temperature at 2 m height over the northern North Atlantic and the southern South Atlantic. Over land, only a few areas are significantly predictable. The predictability for continental size averages of air temperature is relatively good in all northern hemisphere regions. Sea ice thickness is highly predictable along the ice edges in the North Atlantic Arctic Sector. The meridional overturning circulation is highly predictable in both experiments and governs most of the decadal climate predictability in the northern hemisphere. The experiments using reduced sea ice albedo show some important differences like a generally higher predictability of atmospheric variables in the Arctic or higher predictability of air temperature in Europe. Furthermore, decadal variations are substantially smaller in the simulations with reduced ice albedo, which can be explained by reduced sea ice thickness in these simulations. (orig.)
International Nuclear Information System (INIS)
Ayala, Orlando; Rosa, Bogdan; Wang Lianping
2008-01-01
The effect of air turbulence on the geometric collision kernel of cloud droplets can be predicted if the effects of air turbulence on two kinematic pair statistics can be modeled. The first is the average radial relative velocity and the second is the radial distribution function (RDF). A survey of the literature shows that no theory is available for predicting the radial relative velocity of finite-inertia sedimenting droplets in a turbulent flow. In this paper, a theory for the radial relative velocity is developed, using a statistical approach assuming that gravitational sedimentation dominates the relative motion of droplets before collision. In the weak-inertia limit, the theory reveals a new term making a positive contribution to the radial relative velocity resulting from a coupling between sedimentation and air turbulence on the motion of finite-inertia droplets. The theory is compared to the direct numerical simulations (DNS) results in part 1, showing a reasonable agreement with the DNS data for bidisperse cloud droplets. For droplets larger than 30 μm in radius, a nonlinear drag (NLD) can also be included in the theory in terms of an effective inertial response time and an effective terminal velocity. In addition, an empirical model is developed to quantify the RDF. This, together with the theory for radial relative velocity, provides a parameterization for the turbulent geometric collision kernel. Using this integrated model, we find that turbulence could triple the geometric collision kernel, relative to the stagnant air case, for a droplet pair of 10 and 20 μm sedimenting through a cumulus cloud at R λ =2x10 4 and ε=600 cm 2 s -3 . For the self-collisions of 20 μm droplets, the collision kernel depends sensitively on the flow dissipation rate
A review of recent research on improvement of physical parameterizations in the GLA GCM
Sud, Y. C.; Walker, G. K.
1990-01-01
A systematic assessment of the effect of a series of improvements in physical parameterizations of the Goddard Laboratory for Atmospheres (GLA) general circulation model (GCM) are summarized. The implementation of the Simple Biosphere Model (SiB) in the GCM is followed by a comparison of SiB GCM simulations with that of the earlier slab soil hydrology GCM (SSH-GCM) simulations. In the Sahelian context, the biogeophysical component of desertification was analyzed for SiB-GCM simulations. Cumulus parameterization is found to be the primary determinant of the organization of the simulated tropical rainfall of the GLA GCM using Arakawa-Schubert cumulus parameterization. A comparison of model simulations with station data revealed excessive shortwave radiation accompanied by excessive drying and heating to the land. The perpetual July simulations with and without interactive soil moisture shows that 30 to 40 day oscillations may be a natural mode of the simulated earth atmosphere system.
Institute of Scientific and Technical Information of China (English)
PING Fan; TANG Xi-ba; YIN Lei
2016-01-01
According to the characteristics of organized cumulus convective precipitation in China,a cumulus parameterization scheme suitable for describing the organized convective precipitation in East Asia is presented and modified.The Kain-Fristch scheme is chosen as the scheme to be modified based on analyses and comparisons of simulated precipitation in East Asia by several commonly-used mesoscale parameterization schemes.A key dynamic parameter to dynamically control the cumulus parameterization is then proposed to improve the Kain-Fristch scheme.Numerical simulations of a typhoon case and a Mei-yu front rainfall case are carried out with the improved scheme,and the results show that the improved version performs better than the original in simulating the track and intensity of the typhoons,as well as the distribution of Mei-yu front precipitation.
Directory of Open Access Journals (Sweden)
D. Barahona
2009-08-01
Full Text Available This study presents a comprehensive ice cloud formation parameterization that computes the ice crystal number, size distribution, and maximum supersaturation from precursor aerosol and ice nuclei. The parameterization provides an analytical solution of the cloud parcel model equations and accounts for the competition effects between homogeneous and heterogeneous freezing, and, between heterogeneous freezing in different modes. The diversity of heterogeneous nuclei is described through a nucleation spectrum function which is allowed to follow any form (i.e., derived from classical nucleation theory or from observations. The parameterization reproduces the predictions of a detailed numerical parcel model over a wide range of conditions, and several expressions for the nucleation spectrum. The average error in ice crystal number concentration was −2.0±8.5% for conditions of pure heterogeneous freezing, and, 4.7±21% when both homogeneous and heterogeneous freezing were active. The formulation presented is fast and free from requirements of numerical integration.
An Analytical Finite-Strain Parameterization for Texture Evolution in Deformed Olivine Polycrystals
Ribe, N. M.; Castelnau, O.
2017-12-01
Current methods for calculating the evolution of flow-induced seismic anisotropy in the upper mantle describe crystal preferred orientation (CPO) using ensembles of 103-104 individual grains, and are too computationally expensive to be used in three-dimensional time-dependent convection models. We propose a much faster method based on the hypothesis that CPO of olivine polycrystals is a unique function of the finite strain. Our goal is then to determine how the CPO depends on the ratios r12 and r23 of the axes of the finite strain ellipsoid and on the two independent ratios p12 and p23 of the strengths (critical resolved shear stresses) of the three independent slip systems of olivine. To do this, we introduce a new analytical representation of olivine CPO in terms of three `structured basis functions' (SBFs) Fs(g, r12, r23) (s = 1, 2, 3), where g is the set of three Eulerian angles that describe the orientation of a crystal lattice relative to an external reference frame. Each SBF represents the virtual CPO that would be produced by the action of only one of the slip systems of olivine, and can be determined analytically to within an unknown time-dependent amplitude. The amplitudes are then determined by fitting the SBFs to the predictions of the second-order self-consistent (SOSC) model of Ponte-Castaneda (2002). To implement the SBF representation, we express the orientation distribution function (ODF) f(g) of the polycrystal approximately as a linear superposition of SBFs with weighting coefficients Cs. Substituting the superposition into the general evolution equation for the ODF and minimizing the residual error, we find that the weighting coefficients Cs(t) satisfy coupled evolution equations of the form αisCs + βisCs + γs = 0 where the coefficients αis, βis and γs can be calculated in advance from the expressions for the SBFs. These equations are solved numerically for different values of p12 and p23, yielding numerical values of Cs(r12, r23, p12, p23
Wang, Yu; Wu, Zhijun; Ma, Nan; Wu, Yusheng; Zeng, Limin; Zhao, Chunsheng; Wiedensohler, Alfred
2018-02-01
The take-up of water of aerosol particles plays an important role in heavy haze formation over North China Plain, since it is related with particle mass concentration, visibility degradation, and particle chemistry. In the present study, we investigated the size-resolved hygroscopic growth factor (HGF) of sub-micrometer aerosol particles (smaller than 350 nm) on a basis of 9-month Hygroscopicity-Tandem Differential Mobility Analyzer measurement in the urban background atmosphere of Beijing. The mean hygroscopicity parameter (κ) values derived from averaging over the entire sampling period for particles of 50 nm, 75 nm, 100 nm, 150 nm, 250 nm, and 350 nm in diameters were 0.14 ± 0.07, 0.17 ± 0.05, 0.18 ± 0.06, 0.20 ± 0.07, 0.21 ± 0.09, and 0.23 ± 0.12, respectively, indicating the dominance of organics in the sub-micrometer urban aerosols. In the spring, summer, and autumn, the number fraction of hydrophilic particles increased with increasing particle size, resulting in an increasing trend of overall particle hygroscopicity with enhanced particle size. Differently, the overall mean κ values peaked in the range of 75-150 nm and decreased for particles larger than 150 nm in diameter during wintertime. Such size-dependency of κ in winter was related to the strong primary particle emissions from coal combustion during domestic heating period. The number fraction of hydrophobic particles such as freshly emitted soot decreased with increasing PM2.5 mass concentration, indicating aged and internal mixed particles were dominant in the severe particulate matter pollution. Parameterization schemes of the HGF as a function of relative humidity (RH) and particle size between 50 and 350 nm were determined for different seasons and pollution levels. The HGFs calculated from the parameterizations agree well with the measured HGFs at 20-90% RH. The parameterizations can be applied to determine the hygroscopic growth of aerosol particles at ambient conditions for the area
International Nuclear Information System (INIS)
Yan, Y.T.
1996-11-01
A brief review of the Zlib development is given. Emphasized is the Zlib nerve system which uses the One-Step Index Pointers (OSIPs) for efficient computation and flexible use of the Truncated Power Series Algebra (TPSA). Also emphasized is the treatment of parameterized maps with an object-oriented language (e.g. C++). A parameterized map can be a Vector Power Series (Vps) or a Lie generator represented by an exponent of a Truncated Power Series (Tps) of which each coefficient is an object of truncated power series
Impact of model structure and parameterization on Penman-Monteith type evaporation models
Ershadi, A.; McCabe, Matthew; Evans, J.P.; Wood, E.F.
2015-01-01
Overall, the results illustrate the sensitivity of Penman-Monteith type models to model structure, parameterization choice and biome type. A particular challenge in flux estimation relates to developing robust and broadly applicable model formulations. With many choices available for use, providing guidance on the most appropriate scheme to employ is required to advance approaches for routine global scale flux estimates, undertake hydrometeorological assessments or develop hydrological forecasting tools, amongst many other applications. In such cases, a multi-model ensemble or biome-specific tiled evaporation product may be an appropriate solution, given the inherent variability in model and parameterization choice that is observed within single product estimates.
Feng, Xiaoqi; Astell-Burt, Thomas
2017-02-27
Recent reviews of the rapidly growing scientific literature on neighbourhood green space and health show strong evidence for protective and restorative effects on mental wellbeing. However, multiple informants are common when reporting mental wellbeing in studies of children. Do different informants lead to different results? This study utilised nationally representative data on Goodman's 25-item Strengths and Difficulties Questionnaire reported by 3083 children (aged 12-13 years old), and their parents and teachers. Multilevel models were used to investigate whether similar associations between child mental wellbeing (as measured using the total difficulties score and the internalising and externalising subscales) and neighbourhood green space quantity and quality are obtained regardless of the informant. After adjustment for confounders, higher green space quantity and quality were associated with consistently more favourable child mental wellbeing on all three measures, regardless of the informant. However, associations with green space quantity were statistically significant ( p health should acknowledge when different informants of outcomes could lead to different conclusions.
Energy Technology Data Exchange (ETDEWEB)
Henderson-Sellers, A. (Macquarie Univ., North Ryde, New South Wales (Australia))
1993-02-01
Land-surface schemes developed for incorporation into global climate models include parameterizations that are not yet fully validated and depend upon the specification of a large (20-50) number of ecological and soil parameters, the values of which are not yet well known. There are two methods of investigating the sensitivity of a land-surface scheme to prescribed values: simple one-at-a-time changes or factorial experiments. Factorial experiments offer information about interactions between parameters and are thus a more powerful tool. Here the results of a suite of factorial experiments are reported. These are designed (i) to illustrate the usefulness of this methodology and (ii) to identify factors important to the performance of complex land-surface schemes. The Biosphere-Atmosphere Transfer Scheme (BATS) is used and its sensitivity is considered (a) to prescribed ecological and soil parameters and (b) to atmospheric forcing used in the off-line tests undertaken. Results indicate that the most important atmospheric forcings are mean monthly temperature and the interaction between mean monthly temperature and total monthly precipitation, although fractional cloudiness and other parameters are also important. The most important ecological parameters are vegetation roughness length, soil porosity, and a factor describing the sensitivity of the stomatal resistance of vegetation to the amount of photosynthetically active solar radiation and, to a lesser extent, soil and vegetation albedos. Two-factor interactions including vegetation roughness length are more important than many of the 23 specified single factors. The results of factorial sensitivity experiments such as these could form the basis for intercomparison of land-surface parameterization schemes and for field experiments and satellite-based observation programs aimed at improving evaluation of important parameters.
Koskela, Harri; Anđelković, Boban
2017-10-01
The spectral parameters of selected nerve agent degradation products relevant to the Chemical Weapons Convention, namely, ethyl methylphosphonate, isopropyl methylphosphonate, pinacolyl methylphosphonate and methylphosphonic acid, were studied in wide range of pH conditions and selected temperatures. The pH and temperature dependence of chemical shifts and J couplings was parameterized using Henderson-Hasselbalch-based functions. The obtained parameters allowed calculation of precise chemical shifts and J coupling constants in arbitrary pH conditions and typical measurement temperatures, thus facilitating quantum mechanical simulation of reference spectra in the chosen magnetic field strength for chemical verification. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.
Doherty, John E.; Hunt, Randall J.; Tonkin, Matthew J.
2010-01-01
Analysis of the uncertainty associated with parameters used by a numerical model, and with predictions that depend on those parameters, is fundamental to the use of modeling in support of decisionmaking. Unfortunately, predictive uncertainty analysis with regard to models can be very computationally demanding, due in part to complex constraints on parameters that arise from expert knowledge of system properties on the one hand (knowledge constraints) and from the necessity for the model parameters to assume values that allow the model to reproduce historical system behavior on the other hand (calibration constraints). Enforcement of knowledge and calibration constraints on parameters used by a model does not eliminate the uncertainty in those parameters. In fact, in many cases, enforcement of calibration constraints simply reduces the uncertainties associated with a number of broad-scale combinations of model parameters that collectively describe spatially averaged system properties. The uncertainties associated with other combinations of parameters, especially those that pertain to small-scale parameter heterogeneity, may not be reduced through the calibration process. To the extent that a prediction depends on system-property detail, its postcalibration variability may be reduced very little, if at all, by applying calibration constraints; knowledge constraints remain the only limits on the variability of predictions that depend on such detail. Regrettably, in many common modeling applications, these constraints are weak. Though the PEST software suite was initially developed as a tool for model calibration, recent developments have focused on the evaluation of model-parameter and predictive uncertainty. As a complement to functionality that it provides for highly parameterized inversion (calibration) by means of formal mathematical regularization techniques, the PEST suite provides utilities for linear and nonlinear error-variance and uncertainty analysis in
Parameterization of ion-induced nucleation rates based on ambient observations
Directory of Open Access Journals (Sweden)
T. Nieminen
2011-04-01
Full Text Available Atmospheric ions participate in the formation of new atmospheric aerosol particles, yet their exact role in this process has remained unclear. Here we derive a new simple parameterization for ion-induced nucleation or, more precisely, for the formation rate of charged 2-nm particles. The parameterization is semi-empirical in the sense that it is based on comprehensive results of one-year-long atmospheric cluster and particle measurements in the size range ~1–42 nm within the EUCAARI (European Integrated project on Aerosol Cloud Climate and Air Quality interactions project. Data from 12 field sites across Europe measured with different types of air ion and cluster mobility spectrometers were used in our analysis, with more in-depth analysis made using data from four stations with concomitant sulphuric acid measurements. The parameterization is given in two slightly different forms: a more accurate one that requires information on sulfuric acid and nucleating organic vapor concentrations, and a simpler one in which this information is replaced with the global radiation intensity. These new parameterizations are applicable to all large-scale atmospheric models containing size-resolved aerosol microphysics, and a scheme to calculate concentrations of sulphuric acid, condensing organic vapours and cluster ions.
Evaluating parameterizations of aerodynamic resistance to heat transfer using field measurements
Directory of Open Access Journals (Sweden)
Shaomin Liu
2007-01-01
Full Text Available Parameterizations of aerodynamic resistance to heat and water transfer have a significant impact on the accuracy of models of land – atmosphere interactions and of estimated surface fluxes using spectro-radiometric data collected from aircrafts and satellites. We have used measurements from an eddy correlation system to derive the aerodynamic resistance to heat transfer over a bare soil surface as well as over a maize canopy. Diurnal variations of aerodynamic resistance have been analyzed. The results showed that the diurnal variation of aerodynamic resistance during daytime (07:00 h–18:00 h was significant for both the bare soil surface and the maize canopy although the range of variation was limited. Based on the measurements made by the eddy correlation system, a comprehensive evaluation of eight popularly used parameterization schemes of aerodynamic resistance was carried out. The roughness length for heat transfer is a crucial parameter in the estimation of aerodynamic resistance to heat transfer and can neither be taken as a constant nor be neglected. Comparing with the measurements, the parameterizations by Choudhury et al. (1986, Viney (1991, Yang et al. (2001 and the modified forms of Verma et al. (1976 and Mahrt and Ek (1984 by inclusion of roughness length for heat transfer gave good agreements with the measurements, while the parameterizations by Hatfield et al. (1983 and Xie (1988 showed larger errors even though the roughness length for heat transfer has been taken into account.
Madhulatha, A.; Rajeevan, M.
2018-02-01
Main objective of the present paper is to examine the role of various parameterization schemes in simulating the evolution of mesoscale convective system (MCS) occurred over south-east India. Using the Weather Research and Forecasting (WRF) model, numerical experiments are conducted by considering various planetary boundary layer, microphysics, and cumulus parameterization schemes. Performances of different schemes are evaluated by examining boundary layer, reflectivity, and precipitation features of MCS using ground-based and satellite observations. Among various physical parameterization schemes, Mellor-Yamada-Janjic (MYJ) boundary layer scheme is able to produce deep boundary layer height by simulating warm temperatures necessary for storm initiation; Thompson (THM) microphysics scheme is capable to simulate the reflectivity by reasonable distribution of different hydrometeors during various stages of system; Betts-Miller-Janjic (BMJ) cumulus scheme is able to capture the precipitation by proper representation of convective instability associated with MCS. Present analysis suggests that MYJ, a local turbulent kinetic energy boundary layer scheme, which accounts strong vertical mixing; THM, a six-class hybrid moment microphysics scheme, which considers number concentration along with mixing ratio of rain hydrometeors; and BMJ, a closure cumulus scheme, which adjusts thermodynamic profiles based on climatological profiles might have contributed for better performance of respective model simulations. Numerical simulation carried out using the above combination of schemes is able to capture storm initiation, propagation, surface variations, thermodynamic structure, and precipitation features reasonably well. This study clearly demonstrates that the simulation of MCS characteristics is highly sensitive to the choice of parameterization schemes.
Zedler, S. E.
2009-04-25
The drag coefficient parameterization of wind stress is investigated for tropical storm conditions using model sensitivity studies. The Massachusetts Institute of Technology (MIT) Ocean General Circulation Model was run in a regional setting with realistic stratification and forcing fields representing Hurricane Frances, which in early September 2004 passed east of the Caribbean Leeward Island chain. The model was forced with a NOAA-HWIND wind speed product after converting it to wind stress using four different drag coefficient parameterizations. Respective model results were tested against in situ measurements of temperature profiles and velocity, available from an array of 22 surface drifters and 12 subsurface floats. Changing the drag coefficient parameterization from one that saturated at a value of 2.3 × 10 -3 to a constant drag coefficient of 1.2 × 10-3 reduced the standard deviation difference between the simulated minus the measured sea surface temperature change from 0.8°C to 0.3°C. Additionally, the standard deviation in the difference between simulated minus measured high pass filtered 15-m current speed reduced from 15 cm/s to 5 cm/s. The maximum difference in sea surface temperature response when two different turbulent mixing parameterizations were implemented was 0.3°C, i.e., only 11% of the maximum change of sea surface temperature caused by the storm. Copyright 2009 by the American Geophysical Union.
Multi-sensor remote sensing parameterization of heat fluxes over heterogeneous land surfaces
Faivre, R.D.
2014-01-01
The parameterization of heat transfer by remote sensing, and based on SEBS scheme for turbulent heat fluxes retrieval, already proved to be very convenient for estimating evapotranspiration (ET) over homogeneous land surfaces. However, the use of such a method over heterogeneous landscapes (e.g.
Inclusion of Solar Elevation Angle in Land Surface Albedo Parameterization Over Bare Soil Surface.
Zheng, Zhiyuan; Wei, Zhigang; Wen, Zhiping; Dong, Wenjie; Li, Zhenchao; Wen, Xiaohang; Zhu, Xian; Ji, Dong; Chen, Chen; Yan, Dongdong
2017-12-01
Land surface albedo is a significant parameter for maintaining a balance in surface energy. It is also an important parameter of bare soil surface albedo for developing land surface process models that accurately reflect diurnal variation characteristics and the mechanism behind the solar spectral radiation albedo on bare soil surfaces and for understanding the relationships between climate factors and spectral radiation albedo. Using a data set of field observations, we conducted experiments to analyze the variation characteristics of land surface solar spectral radiation and the corresponding albedo over a typical Gobi bare soil underlying surface and to investigate the relationships between the land surface solar spectral radiation albedo, solar elevation angle, and soil moisture. Based on both solar elevation angle and soil moisture measurements simultaneously, we propose a new two-factor parameterization scheme for spectral radiation albedo over bare soil underlying surfaces. The results of numerical simulation experiments show that the new parameterization scheme can more accurately depict the diurnal variation characteristics of bare soil surface albedo than the previous schemes. Solar elevation angle is one of the most important factors for parameterizing bare soil surface albedo and must be considered in the parameterization scheme, especially in arid and semiarid areas with low soil moisture content. This study reveals the characteristics and mechanism of the diurnal variation of bare soil surface solar spectral radiation albedo and is helpful in developing land surface process models, weather models, and climate models.
Beretvas, S. Natasha; Cawthon, Stephanie W.; Lockhart, L. Leland; Kaye, Alyssa D.
2012-01-01
This pedagogical article is intended to explain the similarities and differences between the parameterizations of two multilevel measurement model (MMM) frameworks. The conventional two-level MMM that includes item indicators and models item scores (Level 1) clustered within examinees (Level 2) and the two-level cross-classified MMM (in which item…
Energy Technology Data Exchange (ETDEWEB)
Evans, J.L.; Frank, W.M.; Young, G.S. [Pennsylvania State Univ., University Park, PA (United States)
1996-04-01
Successful simulations of the global circulation and climate require accurate representation of the properties of shallow and deep convective clouds, stable-layer clouds, and the interactions between various cloud types, the boundary layer, and the radiative fluxes. Each of these phenomena play an important role in the global energy balance, and each must be parameterized in a global climate model. These processes are highly interactive. One major problem limiting the accuracy of parameterizations of clouds and other processes in general circulation models (GCMs) is that most of the parameterization packages are not linked with a common physical basis. Further, these schemes have not, in general, been rigorously verified against observations adequate to the task of resolving subgrid-scale effects. To address these problems, we are designing a new Integrated Cumulus Ensemble and Turbulence (ICET) parameterization scheme, installing it in a climate model (CCM2), and evaluating the performance of the new scheme using data from Atmospheric Radiation Measurement (ARM) Program Cloud and Radiation Testbed (CART) sites.
Accurate parameterization of reference evapotranspiration (ET0) is necessary for optimizing irrigation scheduling and avoiding costs associated with over-irrigation (water expense, loss of water productivity, energy costs, pollution) or with under-irrigation (crop stress and suboptimal yields or qua...
Efficient Parameterization for Grey-box Model Identification of Complex Physical Systems
DEFF Research Database (Denmark)
Blanke, Mogens; Knudsen, Morten Haack
2006-01-01
Grey box model identification preserves known physical structures in a model but with limits to the possible excitation, all parameters are rarely identifiable, and different parametrizations give significantly different model quality. Convenient methods to show which parameterizations are the be...... that need be constrained to achieve satisfactory convergence. Identification of nonlinear models for a ship illustrate the concept....
Toy, M. D.; Olson, J.; Kenyon, J.; Smirnova, T. G.; Brown, J. M.
2017-12-01
The accuracy of wind forecasts in numerical weather prediction (NWP) models is improved when the drag forces imparted on atmospheric flow by subgrid-scale orography are included. Without such parameterizations, only the terrain resolved by the model grid, along with the small-scale obstacles parameterized by the roughness lengths can have an effect on the flow. This neglects the impacts of subgrid-scale terrain variations, which typically leads to wind speeds that are too strong. Using statistical information about the subgrid-scale orography, such as the mean and variance of the topographic height within a grid cell, the drag forces due to flow blocking, gravity wave drag, and turbulent form drag are estimated and distributed vertically throughout the grid cell column. We recently implemented the small-scale gravity wave drag paramterization of Steeneveld et al. (2008) and Tsiringakis et al. (2017) for stable planetary boundary layers, and the turbulent form drag parameterization of Beljaars et al. (2004) in the High-Resolution Rapid Refresh (HRRR) NWP model developed at the National Oceanic and Atmospheric Administration (NOAA). As a result, a high surface wind speed bias in the model has been reduced and small improvement to the maintenance of stable layers has also been found. We present the results of experiments with the subgrid-scale orographic drag parameterization for the regional HRRR model, as well as for a global model in development at NOAA, showing the direct and indirect impacts.
Framework to parameterize and validate APEX to support deployment of the nutrient tracking tool
Guidelines have been developed to parameterize and validate the Agricultural Policy Environmental eXtender (APEX) to support the Nutrient Tracking Tool (NTT). This follow-up paper presents 1) a case study to illustrate how the developed guidelines are applied in a headwater watershed located in cent...
Hydrological models have become essential tools for environmental assessments. This study’s objective was to evaluate a best professional judgment (BPJ) parameterization of the Agricultural Policy and Environmental eXtender (APEX) model with soil-survey data against the calibrated model with either ...
A new albedo parameterization for use in climate models over the Antarctic ice sheet
Kuipers Munneke, P.|info:eu-repo/dai/nl/304831891; van den Broeke, M.R.|info:eu-repo/dai/nl/073765643; Lenaerts, J.T.M.|info:eu-repo/dai/nl/314850163; Flanner, M.G.; Gardner, A.S.; van de Berg, W.J.|info:eu-repo/dai/nl/304831611
2011-01-01
A parameterization for broadband snow surface albedo, based on snow grain size evolution, cloud optical thickness, and solar zenith angle, is implemented into a regional climate model for Antarctica and validated against field observations of albedo for the period 1995–2004. Over the Antarctic
Energy Technology Data Exchange (ETDEWEB)
X Qiu; D Rau; V Parsegian; L Fang; C Knobler; W Gelbart
2011-12-31
Using solution synchrotron x-ray scattering, we measure the variation of DNA-DNA d spacings in bacteriophage {lambda} with mono-, di-, and polyvalent salt concentrations, for wild-type [48.5 x 10{sup 3} base pairs (bp)] and short-genome-mutant (37.8 kbp) strains. From the decrease in d spacings with increasing salt, we deduce the relative contributions of DNA self-repulsion and bending to the energetics of packaged phage genomes. We quantify the DNA-DNA interaction energies within the intact phage by combining the measured d spacings in the capsid with measurements of osmotic pressure in DNA assemblies under the same salt conditions in bulk solution. In the commonly used Tris-Mg buffer, the DNA-DNA interaction energies inside the phage capsids are shown to be about 1 kT/bp, an order of magnitude larger than the bending energies.
Warm Bias and Parameterization of Boundary Upwelling in Ocean Models
Energy Technology Data Exchange (ETDEWEB)
Cessi, Paola; Wolfe, Christopher
2012-11-06
It has been demonstrated that Eastern Boundary Currents (EBC) are a baroclinic intensification of the interior circulation of the ocean due to the emergence of mesoscale eddies in response to the sharp buoyancy gradients driven by the wind-stress and the thermal surface forcing. The eddies accomplish the heat and salt transport necessary to insure that the subsurface flow is adiabatic, compensating for the heat and salt transport effected by the mean currents. The EBC thus generated occurs on a cross-shore scale of order 20-100 km, and thus this scale needs to be resolved in climate models in order to capture the meridional transport by the EBC. Our result indicate that changes in the near shore currents on the oceanic eastern boundaries are linked not just to local forcing, such as coastal changes in the winds, but depend on the basin-wide circulation as well.
Basarab, B.; Fuchs, B.; Rutledge, S. A.
2013-12-01
Predicting lightning activity in thunderstorms is important in order to accurately quantify the production of nitrogen oxides (NOx = NO + NO2) by lightning (LNOx). Lightning is an important global source of NOx, and since NOx is a chemical precursor to ozone, the climatological impacts of LNOx could be significant. Many cloud-resolving models rely on parameterizations to predict lightning and LNOx since the processes leading to charge separation and lightning discharge are not yet fully understood. This study evaluates predicted flash rates based on existing lightning parameterizations against flash rates observed for Colorado storms during the Deep Convective Clouds and Chemistry Experiment (DC3). Evaluating lightning parameterizations against storm observations is a useful way to possibly improve the prediction of flash rates and LNOx in models. Additionally, since convective storms that form in the eastern plains of Colorado can be different thermodynamically and electrically from storms in other regions, it is useful to test existing parameterizations against observations from these storms. We present an analysis of the dynamics, microphysics, and lightning characteristics of two case studies, severe storms that developed on 6 and 7 June 2012. This analysis includes dual-Doppler derived horizontal and vertical velocities, a hydrometeor identification based on polarimetric radar variables using the CSU-CHILL radar, and insight into the charge structure using observations from the northern Colorado Lightning Mapping Array (LMA). Flash rates were inferred from the LMA data using a flash counting algorithm. We have calculated various microphysical and dynamical parameters for these storms that have been used in empirical flash rate parameterizations. In particular, maximum vertical velocity has been used to predict flash rates in some cloud-resolving chemistry simulations. We diagnose flash rates for the 6 and 7 June storms using this parameterization and compare
Directory of Open Access Journals (Sweden)
J. Arteta
2009-09-01
Full Text Available The general objective of this series of papers is to evaluate long duration limited area simulations with idealised tracers as a tool to assess tracer transport in chemistry-transport models (CTMs. In this first paper, we analyse the results of six simulations using different convection closures and parameterizations. The simulations are using the Grell and Dévényi (2002 mass-flux framework for the convection parameterization with different closures (Grell = GR, Arakawa-Shubert = AS, Kain-Fritch = KF, Low omega = LO, Moisture convergence = MC and an ensemble parameterization (EN based on the other five closures. The simulations are run for one month during the SCOUT-O3 field campaign lead from Darwin (Australia. They have a 60 km horizontal resolution and a fine vertical resolution in the upper troposphere/lower stratosphere. Meteorological results are compared with satellite products, radiosoundings and SCOUT-O3 aircraft campaign data. They show that the model is generally in good agreement with the measurements with less variability in the model. Except for the precipitation field, the differences between the six simulations are small on average with respect to the differences with the meteorological observations. The comparison with TRMM rainrates shows that the six parameterizations or closures have similar behaviour concerning convection triggering times and locations. However, the 6 simulations provide two different behaviours for rainfall values, with the EN, AS and KF parameterizations (Group 1 modelling better rain fields than LO, MC and GR (Group 2. The vertical distribution of tropospheric tracers is very different for the two groups showing significantly more transport into the TTL for Group 1 related to the larger average values of the upward velocities. Nevertheless the low values for the Group 1 fluxes at and above the cold point level indicate that the model does not simulate significant overshooting. For stratospheric tracers
Colangelo, Antonio C.
2010-05-01
The central purpose of this work is to perform a reverse procedure in the mass movement conventional parameterization approach. The idea is to generate a number of synthetic mass movements by means of the "slope stability simulator" (Colangelo, 2007), and compeer their morphological and physical properties with "real" conditions of effective mass movements. This device is an integrated part of "relief unity emulator" (rue), that permits generate synthetic mass movements in a synthetic slope environment. The "rue" was build upon fundamental geomorphological concepts. These devices operate with an integrated set of mechanical, geomorphic and hydrological models. The "slope stability simulator" device (sss) permits to perform a detailed slope stability analysis in a theoretical three dimensional space, by means of evaluation the spatial behavior of critical depths, gradients and saturation levels in the "potential rupture surfaces" inferred along a set of slope profiles, that compounds a synthetic slope unity. It's a meta-stable 4-dimensional object generated by means of "rue", that represents a sequence evolution of a generator profile applied here, was adapted the infinite slope model for slope. Any slope profiles were sliced by means of finite element solution like in Bishop method. For the synthetic slope systems generated, we assume that the potential rupture surface occurs at soil-regolith or soil-rock boundary in slope material. Sixteen variables were included in the "rue-sss" device that operates in an integrated manner. For each cell, the factor of safety was calculated considering the value of shear strength (cohesion and friction) of material, soil-regolith boundary depth, soil moisture level content, potential rupture surface gradient, slope surface gradient, top of subsurface flow gradient, apparent soil bulk density and vegetation surcharge. The slope soil was considered as cohesive material. The 16 variables incorporated in the models were analyzed for
Ozonolysis of α-pinene: parameterization of secondary organic aerosol mass fraction
Directory of Open Access Journals (Sweden)
R. K. Pathak
2007-07-01
Full Text Available Existing parameterizations tend to underpredict the α-pinene aerosol mass fraction (AMF or yield by a factor of 2–5 at low organic aerosol concentrations (<5 µg m^{−3}. A wide range of smog chamber results obtained at various conditions (low/high NO_{x}, presence/absence of UV radiation, dry/humid conditions, and temperatures ranging from 15–40°C collected by various research teams during the last decade are used to derive new parameterizations of the SOA formation from α-pinene ozonolysis. Parameterizations are developed by fitting experimental data to a basis set of saturation concentrations (from 10^{−2} to 10^{4} µg m^{−3} using an absorptive equilibrium partitioning model. Separate parameterizations for α-pinene SOA mass fractions are developed for: 1 Low NO_{x}, dark, and dry conditions, 2 Low NO_{x}, UV, and dry conditions, 3 Low NO_{x}, dark, and high RH conditions, 4 High NO_{x}, dark, and dry conditions, 5 High NO_{x}, UV, and dry conditions. According to the proposed parameterizations the α-pinene SOA mass fractions in an atmosphere with 5 µg m^{−3} of organic aerosol range from 0.032 to 0.1 for reacted α-pinene concentrations in the 1 ppt to 5 ppb range.
Wang, Chao; Forget, François; Bertrand, Tanguy; Spiga, Aymeric; Millour, Ehouarn; Navarro, Thomas
2018-04-01
The origin of the detached dust layers observed by the Mars Climate Sounder aboard the Mars Reconnaissance Orbiter is still debated. Spiga et al. (2013, https://doi.org/10.1002/jgre.20046) revealed that deep mesoscale convective "rocket dust storms" are likely to play an important role in forming these dust layers. To investigate how the detached dust layers are generated by this mesoscale phenomenon and subsequently evolve at larger scales, a parameterization of rocket dust storms to represent the mesoscale dust convection is designed and included into the Laboratoire de Météorologie Dynamique (LMD) Martian Global Climate Model (GCM). The new parameterization allows dust particles in the GCM to be transported to higher altitudes than in traditional GCMs. Combined with the horizontal transport by large-scale winds, the dust particles spread out and form detached dust layers. During the Martian dusty seasons, the LMD GCM with the new parameterization is able to form detached dust layers. The formation, evolution, and decay of the simulated dust layers are largely in agreement with the Mars Climate Sounder observations. This suggests that mesoscale rocket dust storms are among the key factors to explain the observed detached dust layers on Mars. However, the detached dust layers remain absent in the GCM during the clear seasons, even with the new parameterization. This implies that other relevant atmospheric processes, operating when no dust storms are occurring, are needed to explain the Martian detached dust layers. More observations of local dust storms could improve the ad hoc aspects of this parameterization, such as the trigger and timing of dust injection.
Feng, Xiaoqi; Astell-Burt, Thomas
2017-01-01
Recent reviews of the rapidly growing scientific literature on neighbourhood green space and health show strong evidence for protective and restorative effects on mental wellbeing. However, multiple informants are common when reporting mental wellbeing in studies of children. Do different informants lead to different results? This study utilised nationally representative data on Goodman’s 25-item Strengths and Difficulties Questionnaire reported by 3083 children (aged 12–13 years old), and their parents and teachers. Multilevel models were used to investigate whether similar associations between child mental wellbeing (as measured using the total difficulties score and the internalising and externalising subscales) and neighbourhood green space quantity and quality are obtained regardless of the informant. After adjustment for confounders, higher green space quantity and quality were associated with consistently more favourable child mental wellbeing on all three measures, regardless of the informant. However, associations with green space quantity were statistically significant (p health should acknowledge when different informants of outcomes could lead to different conclusions. PMID:28264461
Ackerman, A. S.; Kelley, M.; Cheng, Y.; Fridlind, A. M.; Del Genio, A. D.; Bauer, S.
2017-12-01
Reduction in cloud-water sedimentation induced by increasing droplet concentrations has been shown in large-eddy simulations (LES) and direct numerical simulation (DNS) to enhance boundary-layer entrainment, thereby reducing cloud liquid water path and offsetting the Twomey effect when the overlying air is sufficiently dry, which is typical. Among recent upgrades to ModelE3, the latest version of the NASA Goddard Institute for Space Studies (GISS) general circulation model (GCM), are a two-moment stratiform cloud microphysics treatment with prognostic precipitation and a moist turbulence scheme that includes an option in its entrainment closure of a simple parameterization for the effect of cloud-water sedimentation. Single column model (SCM) simulations are compared to LES results for a stratocumulus case study and show that invoking the sedimentation-entrainment parameterization option indeed reduces the dependence of cloud liquid water path on increasing aerosol concentrations. Impacts of variations of the SCM configuration and the sedimentation-entrainment parameterization will be explored. Its impact on global aerosol indirect forcing in the framework of idealized atmospheric GCM simulations will also be assessed.
Calibration process of highly parameterized semi-distributed hydrological model
Vidmar, Andrej; Brilly, Mitja
2017-04-01
Hydrological phenomena take place in the hydrological system, which is governed by nature, and are essentially stochastic. These phenomena are unique, non-recurring, and changeable across space and time. Since any river basin with its own natural characteristics and any hydrological event therein, are unique, this is a complex process that is not researched enough. Calibration is a procedure of determining the parameters of a model that are not known well enough. Input and output variables and mathematical model expressions are known, while only some parameters are unknown, which are determined by calibrating the model. The software used for hydrological modelling nowadays is equipped with sophisticated algorithms for calibration purposes without possibility to manage process by modeler. The results are not the best. We develop procedure for expert driven process of calibration. We use HBV-light-CLI hydrological model which has command line interface and coupling it with PEST. PEST is parameter estimation tool which is used widely in ground water modeling and can be used also on surface waters. Process of calibration managed by expert directly, and proportionally to the expert knowledge, affects the outcome of the inversion procedure and achieves better results than if the procedure had been left to the selected optimization algorithm. First step is to properly define spatial characteristic and structural design of semi-distributed model including all morphological and hydrological phenomena, like karstic area, alluvial area and forest area. This step includes and requires geological, meteorological, hydraulic and hydrological knowledge of modeler. Second step is to set initial parameter values at their preferred values based on expert knowledge. In this step we also define all parameter and observation groups. Peak data are essential in process of calibration if we are mainly interested in flood events. Each Sub Catchment in the model has own observations group
International Nuclear Information System (INIS)
Matsumoto, Yoshio; Yano, Syukuro
1982-01-01
Properties of a virtual cathode in a pulsed ion diode composed of an insulator-mesh anode and a metal-mesh cathode were studied experimentally at anode voltages below 360kV. Potential distribution in the virtual cathode side was measured with an insulated electrostatic potential probe, and ion beam currents in virtual and real cathode sides were measured with biased ion collectors. A loss parameter for the electron current at the virtual cathode was evaluated from the measured electron current values by using relations derived from the one-dimensional Child-Langmuir theory applied to the reflex triode. The ion beam accompanies a considerable amount of electron current, and this influences the stability of the virtual cathode; this perturbation results in variations of ion current with time. Space potentials in the emitted ion beam are given, suggesting an existence of high energy electrons of several keV accelerated by positive space potential of the ion beam. (author)
Impact of model structure and parameterization on Penman-Monteith type evaporation models
Ershadi, A.
2015-04-12
The impact of model structure and parameterization on the estimation of evaporation is investigated across a range of Penman-Monteith type models. To examine the role of model structure on flux retrievals, three different retrieval schemes are compared. The schemes include a traditional single-source Penman-Monteith model (Monteith, 1965), a two-layer model based on Shuttleworth and Wallace (1985) and a three-source model based on Mu et al. (2011). To assess the impact of parameterization choice on model performance, a number of commonly used formulations for aerodynamic and surface resistances were substituted into the different formulations. Model response to these changes was evaluated against data from twenty globally distributed FLUXNET towers, representing a cross-section of biomes that include grassland, cropland, shrubland, evergreen needleleaf forest and deciduous broadleaf forest. Scenarios based on 14 different combinations of model structure and parameterization were ranked based on their mean value of Nash-Sutcliffe Efficiency. Results illustrated considerable variability in model performance both within and between biome types. Indeed, no single model consistently outperformed any other when considered across all biomes. For instance, in grassland and shrubland sites, the single-source Penman-Monteith model performed the best. In croplands it was the three-source Mu model, while for evergreen needleleaf and deciduous broadleaf forests, the Shuttleworth-Wallace model rated highest. Interestingly, these top ranked scenarios all shared the simple lookup-table based surface resistance parameterization of Mu et al. (2011), while a more complex Jarvis multiplicative method for surface resistance produced lower ranked simulations. The highly ranked scenarios mostly employed a version of the Thom (1975) formulation for aerodynamic resistance that incorporated dynamic values of roughness parameters. This was true for all cases except over deciduous broadleaf
Martínez-Castro, Daniel; Vichot-Llano, Alejandro; Bezanilla-Morlot, Arnoldo; Centella-Artola, Abel; Campbell, Jayaka; Giorgi, Filippo; Viloria-Holguin, Cecilia C.
2018-06-01
A sensitivity study of the performance of the RegCM4 regional climate model driven by the ERA Interim reanalysis is conducted for the Central America and Caribbean region. A set of numerical experiments are completed using four configurations of the model, with a horizontal grid spacing of 25 km for a period of 6 years (1998-2003), using three of the convective parameterization schemes implemented in the model, the Emanuel scheme, the Grell over land-Emanuel over ocean scheme and two configurations of the Tiedtke scheme. The objective of the study is to investigate the ability of each configuration to reproduce different characteristics of the temperature, circulation and precipitation fields for the dry and rainy seasons. All schemes simulate the general temperature and precipitation patterns over land reasonably well, with relatively high correlations compared to observation datasets, though in specific regions there are positive or negative biases, greater in the rainy season. We also focus on some circulation features relevant for the region, such as the Caribbean low level jet and sea breeze circulations over islands, which are simulated by the model with varied performance across the different configurations. We find that no model configuration assessed is best performing for all the analysis criteria selected, but the Tiedtke configurations, which include the capability of tuning in particular the exchanges between cloud and environment air, provide the most balanced range of biases across variables, with no outstanding systematic bias emerging.
Donlon, Kevan; Ninkov, Zoran; Baum, Stefi
2016-08-01
Interpixel capacitance (IPC) is a deterministic electronic coupling by which signal generated in one pixel is measured in neighboring pixels. Examination of dark frames from test NIRcam arrays corroborates earlier results and simulations illustrating a signal dependent coupling. When the signal on an individual pixel is larger, the fractional coupling to nearest neighbors is lesser than when the signal is lower. Frames from test arrays indicate a drop in average coupling from approximately 1.0% at low signals down to approximately 0.65% at high signals depending on the particular array in question. The photometric ramifications for this non-uniformity are not fully understood. This non-uniformity intro-duces a non-linearity in the current mathematical model for IPC coupling. IPC coupling has been mathematically formalized as convolution by a blur kernel. Signal dependence requires that the blur kernel be locally defined as a function of signal intensity. Through application of a signal dependent coupling kernel, the IPC coupling can be modeled computationally. This method allows for simultaneous knowledge of the intrinsic parameters of the image scene, the result of applying a constant IPC, and the result of a signal dependent IPC. In the age of sub-pixel precision in astronomy these effects must be properly understood and accounted for in order for the data to accurately represent the object of observation. Implementation of this method is done through python scripted processing of images. The introduction of IPC into simulated frames is accomplished through convolution of the image with a blur kernel whose parameters are themselves locally defined functions of the image. These techniques can be used to enhance the data processing pipeline for NIRcam.
Energy Technology Data Exchange (ETDEWEB)
Erokhin, A. N., E-mail: nerokhin@mx.iki.rssi.ru [People’s Friendship University of Russia (Russian Federation); Zol’nikova, N. N. [Russian Academy of Sciences, Space Research Institute (Russian Federation); Erokhin, N. S. [People’s Friendship University of Russia (Russian Federation)
2016-01-15
Based on the numerical solution of the nonlinear nonstationary second-order equation for the wave phase on the particle trajectory, the dynamics of surfatron acceleration of electrons by an electromagnetic wave propagating across the external magnetic field in space plasma is analyzed as a function of the electron momentum along the wave front. Numerical calculations show that, for strongly relativistic initial values of the electron momentum component along the wave front g{sub y}(0) (the other parameters of the problem being the same), electrons are trapped into the regime of ultrarelativistic surfatron acceleration within a certain interval of the initial wave phase Ψ(0) on the particle trajectory. It is assumed in the calculations that vertical bar Ψ(0) vertical bar ≤ π. For strongly relativistic values of g{sub y}(0), electrons are immediately trapped by the wave for 19% of the initial values of the phase Ψ(0) (favorable phases). For the rest of the values of Ψ(0), trapping does not occur even at long times. This circumstance substantially simplifies estimations of the wave damping due to particle acceleration in subsequent calculations. The dynamics of the relativistic factor and the components of the electron velocity and momentum under surfatron acceleration is also analyzed. The obtained results are of interest for the development of modern concepts of possible mechanisms of generation of ultrarelativistic particle fluxes in relatively calm space plasma, as well as for correct interpretation of observational data on the fluxes of such particles and explanation of possible reasons for the deviation of ultrarelativistic particle spectra detected in the heliosphere from the standard power-law scalings and the relation of these variations to space weather and large-scale atmospheric processes similar to tropical cyclones.
International Nuclear Information System (INIS)
Erokhin, A. N.; Zol’nikova, N. N.; Erokhin, N. S.
2016-01-01
Based on the numerical solution of the nonlinear nonstationary second-order equation for the wave phase on the particle trajectory, the dynamics of surfatron acceleration of electrons by an electromagnetic wave propagating across the external magnetic field in space plasma is analyzed as a function of the electron momentum along the wave front. Numerical calculations show that, for strongly relativistic initial values of the electron momentum component along the wave front g y (0) (the other parameters of the problem being the same), electrons are trapped into the regime of ultrarelativistic surfatron acceleration within a certain interval of the initial wave phase Ψ(0) on the particle trajectory. It is assumed in the calculations that vertical bar Ψ(0) vertical bar ≤ π. For strongly relativistic values of g y (0), electrons are immediately trapped by the wave for 19% of the initial values of the phase Ψ(0) (favorable phases). For the rest of the values of Ψ(0), trapping does not occur even at long times. This circumstance substantially simplifies estimations of the wave damping due to particle acceleration in subsequent calculations. The dynamics of the relativistic factor and the components of the electron velocity and momentum under surfatron acceleration is also analyzed. The obtained results are of interest for the development of modern concepts of possible mechanisms of generation of ultrarelativistic particle fluxes in relatively calm space plasma, as well as for correct interpretation of observational data on the fluxes of such particles and explanation of possible reasons for the deviation of ultrarelativistic particle spectra detected in the heliosphere from the standard power-law scalings and the relation of these variations to space weather and large-scale atmospheric processes similar to tropical cyclones
Directory of Open Access Journals (Sweden)
N. Kuba
2006-01-01
Full Text Available First, a hybrid cloud microphysical model was developed that incorporates both Lagrangian and Eulerian frameworks to study quantitatively the effect of cloud condensation nuclei (CCN on the precipitation of warm clouds. A parcel model and a grid model comprise the cloud model. The condensation growth of CCN in each parcel is estimated in a Lagrangian framework. Changes in cloud droplet size distribution arising from condensation and coalescence are calculated on grid points using a two-moment bin method in a semi-Lagrangian framework. Sedimentation and advection are estimated in the Eulerian framework between grid points. Results from the cloud model show that an increase in the number of CCN affects both the amount and the area of precipitation. Additionally, results from the hybrid microphysical model and Kessler's parameterization were compared. Second, new parameterizations were developed that estimate the number and size distribution of cloud droplets given the updraft velocity and the number of CCN. The parameterizations were derived from the results of numerous numerical experiments that used the cloud microphysical parcel model. The input information of CCN for these parameterizations is only several values of CCN spectrum (they are given by CCN counter for example. It is more convenient than conventional parameterizations those need values concerned with CCN spectrum, C and k in the equation of N=CSk, or, breadth, total number and median radius, for example. The new parameterizations' predictions of initial cloud droplet size distribution for the bin method were verified by using the aforesaid hybrid microphysical model. The newly developed parameterizations will save computing time, and can effectively approximate components of cloud microphysics in a non-hydrostatic cloud model. The parameterizations are useful not only in the bin method in the regional cloud-resolving model but also both for a two-moment bulk microphysical model and
Energy Technology Data Exchange (ETDEWEB)
Del Genio, Anthony D. [NASA Goddard Inst. for Space Studies (GISS), New York, NY (United States)
2016-03-11
Over this period the PI and his performed a broad range of data analysis, model evaluation, and model improvement studies using ARM data. These included cloud regimes in the TWP and their evolution over the MJO; M-PACE IOP SCM-CRM intercomparisons; simulations of convective updraft strength and depth during TWP-ICE; evaluation of convective entrainment parameterizations using TWP-ICE simulations; evaluation of GISS GCM cloud behavior vs. long-term SGP cloud statistics; classification of aerosol semi-direct effects on cloud cover; depolarization lidar constraints on cloud phase; preferred states of the winter Arctic atmosphere, surface, and sub-surface; sensitivity of convection to tropospheric humidity; constraints on the parameterization of mesoscale organization from TWP-ICE WRF simulations; updraft and downdraft properties in TWP-ICE simulated convection; insights from long-term ARM records at Manus and Nauru.
International Nuclear Information System (INIS)
Huang, Dong; Liu, Yangang
2014-01-01
Subgrid-scale variability is one of the main reasons why parameterizations are needed in large-scale models. Although some parameterizations started to address the issue of subgrid variability by introducing a subgrid probability distribution function for relevant quantities, the spatial structure has been typically ignored and thus the subgrid-scale interactions cannot be accounted for physically. Here we present a new statistical-physics-like approach whereby the spatial autocorrelation function can be used to physically capture the net effects of subgrid cloud interaction with radiation. The new approach is able to faithfully reproduce the Monte Carlo 3D simulation results with several orders less computational cost, allowing for more realistic representation of cloud radiation interactions in large-scale models. (letter)
Mesoscale model parameterizations for radiation and turbulent fluxes at the lower boundary
International Nuclear Information System (INIS)
Somieski, F.
1988-11-01
A radiation parameterization scheme for use in mesoscale models with orography and clouds has been developed. Broadband parameterizations are presented for the solar and the terrestrial spectral ranges. They account for clear, turbid or cloudy atmospheres. The scheme is one-dimensional in the atmosphere, but the effects of mountains (inclination, shading, elevated horizon) are taken into account at the surface. In the terrestrial band, grey and black clouds are considered. Furthermore, the calculation of turbulent fluxes of sensible and latent heat and momentum at an inclined lower model boundary is described. Surface-layer similarity and the surface energy budget are used to evaluate the ground surface temperature. The total scheme is part of the mesoscale model MESOSCOP. (orig.) With 3 figs., 25 refs [de
Huang, Dong; Liu, Yangang
2014-12-01
Subgrid-scale variability is one of the main reasons why parameterizations are needed in large-scale models. Although some parameterizations started to address the issue of subgrid variability by introducing a subgrid probability distribution function for relevant quantities, the spatial structure has been typically ignored and thus the subgrid-scale interactions cannot be accounted for physically. Here we present a new statistical-physics-like approach whereby the spatial autocorrelation function can be used to physically capture the net effects of subgrid cloud interaction with radiation. The new approach is able to faithfully reproduce the Monte Carlo 3D simulation results with several orders less computational cost, allowing for more realistic representation of cloud radiation interactions in large-scale models.
Mireles James, J. D.; Murray, Maxime
2017-12-01
This paper develops a Chebyshev-Taylor spectral method for studying stable/unstable manifolds attached to periodic solutions of differential equations. The work exploits the parameterization method — a general functional analytic framework for studying invariant manifolds. Useful features of the parameterization method include the fact that it can follow folds in the embedding, recovers the dynamics on the manifold through a simple conjugacy, and admits a natural notion of a posteriori error analysis. Our approach begins by deriving a recursive system of linear differential equations describing the Taylor coefficients of the invariant manifold. We represent periodic solutions of these equations as solutions of coupled systems of boundary value problems. We discuss the implementation and performance of the method for the Lorenz system, and for the planar circular restricted three- and four-body problems. We also illustrate the use of the method as a tool for computing cycle-to-cycle connecting orbits.
Application of a planetary wave breaking parameterization to stratospheric circulation statistics
Randel, William J.; Garcia, Rolando R.
1994-01-01
The planetary wave parameterization scheme developed recently by Garcia is applied to statospheric circulation statistics derived from 12 years of National Meteorological Center operational stratospheric analyses. From the data a planetary wave breaking criterion (based on the ratio of the eddy to zonal mean meridional potential vorticity (PV) gradients), a wave damping rate, and a meridional diffusion coefficient are calculated. The equatorward flank of the polar night jet during winter is identified as a wave breaking region from the observed PV gradients; the region moves poleward with season, covering all high latitudes in spring. Derived damping rates maximize in the subtropical upper stratosphere (the 'surf zone'), with damping time scales of 3-4 days. Maximum diffusion coefficients follow the spatial patterns of the wave breaking criterion, with magnitudes comparable to prior published estimates. Overall, the observed results agree well with the parameterized calculations of Garcia.
Parameterized entropy analysis of EEG following hypoxic-ischemic brain injury
International Nuclear Information System (INIS)
Tong Shanbao; Bezerianos, Anastasios; Malhotra, Amit; Zhu Yisheng; Thakor, Nitish
2003-01-01
In the present study Tsallis and Renyi entropy methods were used to study the electric activity of brain following hypoxic-ischemic (HI) injury. We investigated the performances of these parameterized information measures in describing the electroencephalogram (EEG) signal of controlled experimental animal HI injury. The results show that (a): compared with Shannon and Renyi entropy, the parameterized Tsallis entropy acts like a spatial filter and the information rate can either tune to long range rhythms or to short abrupt changes, such as bursts or spikes during the beginning of recovery, by the entropic index q; (b): Renyi entropy is a compact and predictive indicator for monitoring the physiological changes during the recovery of brain injury. There is a reduction in the Renyi entropy after brain injury followed by a gradual recovery upon resuscitation
Demuzere, M.; De Ridder, K.; van Lipzig, N. P. M.
2008-08-01
During the ESCOMPTE campaign (Experience sur Site pour COntraindre les Modeles de Pollution atmospherique et de Transport d'Emissions), a 4-day intensive observation period was selected to evaluate the Advanced Regional Prediction System (ARPS), a nonhydrostatic meteorological mesoscale model that was optimized with a parameterization for thermal roughness length to better represent urban surfaces. The evaluation shows that the ARPS model is able to correctly reproduce temperature, wind speed, and direction for one urban and two rural measurements stations. Furthermore, simulated heat fluxes show good agreement compared to the observations, although simulated sensible heat fluxes were initially too low for the urban stations. In order to improve the latter, different roughness length parameterization schemes were tested, combined with various thermal admittance values. This sensitivity study showed that the Zilitinkevich scheme combined with and intermediate value of thermal admittance performs best.
A Symbolic Computation Approach to Parameterizing Controller for Polynomial Hamiltonian Systems
Directory of Open Access Journals (Sweden)
Zhong Cao
2014-01-01
Full Text Available This paper considers controller parameterization method of H∞ control for polynomial Hamiltonian systems (PHSs, which involves internal stability and external disturbance attenuation. The aims of this paper are to design a controller with parameters to insure that the systems are H∞ stable and propose an algorithm for solving parameters of the controller with symbolic computation. The proposed parameterization method avoids solving Hamilton-Jacobi-Isaacs equations, and thus the obtained controllers with parameters are relatively simple in form and easy in operation. Simulation with a numerical example shows that the controller is effective as it can optimize H∞ control by adjusting parameters. All these results are expected to be of use in the study of H∞ control for nonlinear systems with perturbations.
Solvation of monovalent anions in formamide and methanol: Parameterization of the IEF-PCM model
International Nuclear Information System (INIS)
Boees, Elvis S.; Bernardi, Edson; Stassen, Hubert; Goncalves, Paulo F.B.
2008-01-01
The thermodynamics of solvation for a series of monovalent anions in formamide and methanol has been studied using the polarizable continuum model (PCM). The parameterization of this continuum model was guided by molecular dynamics simulations. The parameterized PCM model predicts the Gibbs free energies of solvation for 13 anions in formamide and 16 anions in methanol in very good agreement with experimental data. Two sets of atomic radii were tested in the definition of the solute cavities in the PCM and their performances are evaluated and discussed. Mean absolute deviations of the calculated free energies of solvation from the experimental values are in the range of 1.3-2.1 kcal/mol
Ishizawa, Yoshiki; Dobashi, Suguru; Kadoya, Noriyuki; Ito, Kengo; Chiba, Takahito; Takayama, Yoshiki; Sato, Kiyokazu; Takeda, Ken
2018-05-17
An accurate source model of a medical linear accelerator is essential for Monte Carlo (MC) dose calculations. This study aims to propose an analytical photon source model based on particle transport in parameterized accelerator structures, focusing on a more realistic determination of linac photon spectra compared to existing approaches. We designed the primary and secondary photon sources based on the photons attenuated and scattered by a parameterized flattening filter. The primary photons were derived by attenuating bremsstrahlung photons based on the path length in the filter. Conversely, the secondary photons were derived from the decrement of the primary photons in the attenuation process. This design facilitates these sources to share the free parameters of the filter shape and be related to each other through the photon interaction in the filter. We introduced two other parameters of the primary photon source to describe the particle fluence in penumbral regions. All the parameters are optimized based on calculated dose curves in water using the pencil-beam-based algorithm. To verify the modeling accuracy, we compared the proposed model with the phase space data (PSD) of the Varian TrueBeam 6 and 15 MV accelerators in terms of the beam characteristics and the dose distributions. The EGS5 Monte Carlo code was used to calculate the dose distributions associated with the optimized model and reference PSD in a homogeneous water phantom and a heterogeneous lung phantom. We calculated the percentage of points passing 1D and 2D gamma analysis with 1%/1 mm criteria for the dose curves and lateral dose distributions, respectively. The optimized model accurately reproduced the spectral curves of the reference PSD both on- and off-axis. The depth dose and lateral dose profiles of the optimized model also showed good agreement with those of the reference PSD. The passing rates of the 1D gamma analysis with 1%/1 mm criteria between the model and PSD were 100% for 4
Dmitriev, Egor V; Khomenko, Georges; Chami, Malik; Sokolov, Anton A; Churilova, Tatyana Y; Korotaev, Gennady K
2009-03-01
The absorption of sunlight by oceanic constituents significantly contributes to the spectral distribution of the water-leaving radiance. Here it is shown that current parameterizations of absorption coefficients do not apply to the optically complex waters of the Crimea Peninsula. Based on in situ measurements, parameterizations of phytoplankton, nonalgal, and total particulate absorption coefficients are proposed. Their performance is evaluated using a log-log regression combined with a low-pass filter and the nonlinear least-square method. Statistical significance of the estimated parameters is verified using the bootstrap method. The parameterizations are relevant for chlorophyll a concentrations ranging from 0.45 up to 2 mg/m(3).
Graphical Derivatives and Stability Analysis for Parameterized Equilibria with Conic Constraints
Czech Academy of Sciences Publication Activity Database
Mordukhovich, B. S.; Outrata, Jiří; Ramírez, H. C.
2015-01-01
Roč. 23, č. 4 (2015), s. 687-704 ISSN 1877-0533 R&D Projects: GA ČR(CZ) GAP201/12/0671 Institutional support: RVO:67985556 Keywords : Variational analysis and optimization * Parameterized equilibria * Conic constraints * Sensitivity and stability analysis * Solution maps * Graphical derivatives * Normal and tangent cones Subject RIV: BA - General Mathematics Impact factor: 0.973, year: 2015 http://library.utia.cas.cz/separaty/2015/MTR/outrata-0449259.pdf
Parameterizing correlations between hydrometeor species in mixed-phase Arctic clouds
Larson, Vincent E.; Nielsen, Brandon J.; Fan, Jiwen; Ovchinnikov, Mikhail
2011-01-01
Mixed-phase Arctic clouds, like other clouds, contain small-scale variability in hydrometeor fields, such as cloud water or snow mixing ratio. This variability may be worth parameterizing in coarse-resolution numerical models. In particular, for modeling multispecies processes such as accretion and aggregation, it would be useful to parameterize subgrid correlations among hydrometeor species. However, one difficulty is that there exist many hydrometeor species and many microphysical processes, leading to complexity and computational expense. Existing lower and upper bounds on linear correlation coefficients are too loose to serve directly as a method to predict subgrid correlations. Therefore, this paper proposes an alternative method that begins with the spherical parameterization framework of Pinheiro and Bates (1996), which expresses the correlation matrix in terms of its Cholesky factorization. The values of the elements of the Cholesky matrix are populated here using a "cSigma" parameterization that we introduce based on the aforementioned bounds on correlations. The method has three advantages: (1) the computational expense is tolerable; (2) the correlations are, by construction, guaranteed to be consistent with each other; and (3) the methodology is fairly general and hence may be applicable to other problems. The method is tested noninteractively using simulations of three Arctic mixed-phase cloud cases from two field experiments: the Indirect and Semi-Direct Aerosol Campaign and the Mixed-Phase Arctic Cloud Experiment. Benchmark simulations are performed using a large-eddy simulation (LES) model that includes a bin microphysical scheme. The correlations estimated by the new method satisfactorily approximate the correlations produced by the LES.
An explicit parameterization for casting constraints in gradient driven topology optimization
DEFF Research Database (Denmark)
Gersborg, Allan Roulund; Andreasen, Casper Schousboe
2011-01-01
From a practical point of view it is often desirable to limit the complexity of a topology optimization design such that casting/milling type manufacturing techniques can be applied. In the context of gradient driven topology optimization this work studies how castable designs can be obtained...... by use of a Heaviside design parameterization in a specified casting direction. This reduces the number of design variables considerably and the approach is simple to implement....
Framework of cloud parameterization including ice for 3-D mesoscale models
Energy Technology Data Exchange (ETDEWEB)
Levkov, L; Jacob, D; Eppel, D; Grassl, H
1989-01-01
A parameterization scheme for the simulation of ice in clouds incorporated into the hydrostatic version of the GKSS three-dimensional mesoscale model. Numerical simulations of precipitation are performed: over the Northe Sea, the Hawaiian trade wind area and in the region of the intertropical convergence zone. Not only some major features of convective structures in all three areas but also cloud-aerosol interactions have successfully been simulated. (orig.) With 19 figs., 2 tabs.
Multimodel Uncertainty Changes in Simulated River Flows Induced by Human Impact Parameterizations
Liu, Xingcai; Tang, Qiuhong; Cui, Huijuan; Mu, Mengfei; Gerten Dieter; Gosling, Simon; Masaki, Yoshimitsu; Satoh, Yusuke; Wada, Yoshihide
2017-01-01
Human impacts increasingly affect the global hydrological cycle and indeed dominate hydrological changes in some regions. Hydrologists have sought to identify the human-impact-induced hydrological variations via parameterizing anthropogenic water uses in global hydrological models (GHMs). The consequently increased model complexity is likely to introduce additional uncertainty among GHMs. Here, using four GHMs, between-model uncertainties are quantified in terms of the ratio of signal to noise (SNR) for average river flow during 1971-2000 simulated in two experiments, with representation of human impacts (VARSOC) and without (NOSOC). It is the first quantitative investigation of between-model uncertainty resulted from the inclusion of human impact parameterizations. Results show that the between-model uncertainties in terms of SNRs in the VARSOC annual flow are larger (about 2 for global and varied magnitude for different basins) than those in the NOSOC, which are particularly significant in most areas of Asia and northern areas to the Mediterranean Sea. The SNR differences are mostly negative (-20 to 5, indicating higher uncertainty) for basin-averaged annual flow. The VARSOC high flow shows slightly lower uncertainties than NOSOC simulations, with SNR differences mostly ranging from -20 to 20. The uncertainty differences between the two experiments are significantly related to the fraction of irrigation areas of basins. The large additional uncertainties in VARSOC simulations introduced by the inclusion of parameterizations of human impacts raise the urgent need of GHMs development regarding a better understanding of human impacts. Differences in the parameterizations of irrigation, reservoir regulation and water withdrawals are discussed towards potential directions of improvements for future GHM development. We also discuss the advantages of statistical approaches to reduce the between-model uncertainties, and the importance of calibration of GHMs for not only
Directory of Open Access Journals (Sweden)
P. Kumar
2009-04-01
Full Text Available Dust and black carbon aerosol have long been known to exert potentially important and diverse impacts on cloud droplet formation. Most studies to date focus on the soluble fraction of these particles, and overlook interactions of the insoluble fraction with water vapor (even if known to be hydrophilic. To address this gap, we developed a new parameterization that considers cloud droplet formation within an ascending air parcel containing insoluble (but wettable particles externally mixed with aerosol containing an appreciable soluble fraction. Activation of particles with a soluble fraction is described through well-established Köhler theory, while the activation of hydrophilic insoluble particles is treated by "adsorption-activation" theory. In the latter, water vapor is adsorbed onto insoluble particles, the activity of which is described by a multilayer Frenkel-Halsey-Hill (FHH adsorption isotherm modified to account for particle curvature. We further develop FHH activation theory to i find combinations of the adsorption parameters A_{FHH}, B_{FHH} which yield atmospherically-relevant behavior, and, ii express activation properties (critical supersaturation that follow a simple power law with respect to dry particle diameter.
The new parameterization is tested by comparing the parameterized cloud droplet number concentration against predictions with a detailed numerical cloud model, considering a wide range of particle populations, cloud updraft conditions, water vapor condensation coefficient and FHH adsorption isotherm characteristics. The agreement between parameterization and parcel model is excellent, with an average error of 10% and R^{2}~0.98. A preliminary sensitivity study suggests that the sublinear response of droplet number to Köhler particle concentration is not as strong for FHH particles.
Approaches to highly parameterized inversion-A guide to using PEST for groundwater-model calibration
Doherty, John E.; Hunt, Randall J.
2010-01-01
Highly parameterized groundwater models can create calibration difficulties. Regularized inversion-the combined use of large numbers of parameters with mathematical approaches for stable parameter estimation-is becoming a common approach to address these difficulties and enhance the transfer of information contained in field measurements to parameters used to model that system. Though commonly used in other industries, regularized inversion is somewhat imperfectly understood in the groundwater field. There is concern that this unfamiliarity can lead to underuse, and misuse, of the methodology. This document is constructed to facilitate the appropriate use of regularized inversion for calibrating highly parameterized groundwater models. The presentation is directed at an intermediate- to advanced-level modeler, and it focuses on the PEST software suite-a frequently used tool for highly parameterized model calibration and one that is widely supported by commercial graphical user interfaces. A brief overview of the regularized inversion approach is provided, and techniques for mathematical regularization offered by PEST are outlined, including Tikhonov, subspace, and hybrid schemes. Guidelines for applying regularized inversion techniques are presented after a logical progression of steps for building suitable PEST input. The discussion starts with use of pilot points as a parameterization device and processing/grouping observations to form multicomponent objective functions. A description of potential parameter solution methodologies and resources available through the PEST software and its supporting utility programs follows. Directing the parameter-estimation process through PEST control variables is then discussed, including guidance for monitoring and optimizing the performance of PEST. Comprehensive listings of PEST control variables, and of the roles performed by PEST utility support programs, are presented in the appendixes.
Energy Technology Data Exchange (ETDEWEB)
Tiancheng, Yi; Pengfei, Xiao; Yong, Zheng; Juan, Tang; Rong, Wang, E-mail: wangr@bnu.edu.cn
2016-03-01
The effects of irradiation of 1-MeV electrons on p{sup +}–n GaAs/Ge solar cells have been investigated by temperature-dependent photoluminescence (PL) measurements in the temperature range of 10–290 K. The temperature dependence of the PL peak energy agrees well with the Varnish relation, and the thermal quenching of the total integrated PL intensity is well explained by the thermal quenching theory. Meanwhile, the thermal quenching of temperature-dependent PL confirmed that there are two nonradiative recombination centers in the solar cells, and the thermal activation energies of these centers are determined by Arrhenius plots of the total integrated PL intensity. Furthermore, the nonradiative recombination center, as a primary defect, is identified as the H3 hole trap located at E{sub v} + 0.71 eV at room temperature and the H2 hole trap located at E{sub v} + 0.41 eV in the temperature range of 100–200 K, by comparing the thermal activation and ionization energies of the defects.
The relationship between a deformation-based eddy parameterization and the LANS-α turbulence model
Bachman, Scott D.; Anstey, James A.; Zanna, Laure
2018-06-01
A recent class of ocean eddy parameterizations proposed by Porta Mana and Zanna (2014) and Anstey and Zanna (2017) modeled the large-scale flow as a non-Newtonian fluid whose subgridscale eddy stress is a nonlinear function of the deformation. This idea, while largely new to ocean modeling, has a history in turbulence modeling dating at least back to Rivlin (1957). The new class of parameterizations results in equations that resemble the Lagrangian-averaged Navier-Stokes-α model (LANS-α, e.g., Holm et al., 1998a). In this note we employ basic tensor mathematics to highlight the similarities between these turbulence models using component-free notation. We extend the Anstey and Zanna (2017) parameterization, which was originally presented in 2D, to 3D, and derive variants of this closure that arise when the full non-Newtonian stress tensor is used. Despite the mathematical similarities between the non-Newtonian and LANS-α models which might provide insight into numerical implementation, the input and dissipation of kinetic energy between these two turbulent models differ.
A Heuristic Parameterization for the Integrated Vertical Overlap of Cumulus and Stratus
Park, Sungsu
2017-10-01
The author developed a heuristic parameterization to handle the contrasting vertical overlap structures of cumulus and stratus in an integrated way. The parameterization assumes that cumulus is maximum-randomly overlapped with adjacent cumulus; stratus is maximum-randomly overlapped with adjacent stratus; and radiation and precipitation areas at each model interface are grouped into four categories, that is, convective, stratiform, mixed, and clear areas. For simplicity, thermodynamic scalars within individual portions of cloud, radiation, and precipitation areas are assumed to be internally homogeneous. The parameterization was implemented into the Seoul National University Atmosphere Model version 0 (SAM0) in an offline mode and tested over the globe. The offline control simulation reasonably reproduces the online surface precipitation flux and longwave cloud radiative forcing (LWCF). Although the cumulus fraction is much smaller than the stratus fraction, cumulus dominantly contributes to precipitation production in the tropics. For radiation, however, stratus is dominant. Compared with the maximum overlap, the random overlap of stratus produces stronger LWCF and, surprisingly, more precipitation flux due to less evaporation of convective precipitation. Compared with the maximum overlap, the random overlap of cumulus simulates stronger LWCF and weaker precipitation flux. Compared with the control simulation with separate cumulus and stratus, the simulation with a single-merged cloud substantially enhances the LWCF in the tropical deep convection and midlatitude storm track regions. The process-splitting treatment of convective and stratiform precipitation with an independent precipitation approximation (IPA) simulates weaker surface precipitation flux than the control simulation in the tropical region.
De Meij, A.; Vinuesa, J.-F.; Maupas, V.
2018-05-01
The sensitivity of different microphysics and dynamics schemes on calculated global horizontal irradiation (GHI) values in the Weather Research Forecasting (WRF) model is studied. 13 sensitivity simulations were performed for which the microphysics, cumulus parameterization schemes and land surface models were changed. Firstly we evaluated the model's performance by comparing calculated GHI values for the Base Case with observations for the Reunion Island for 2014. In general, the model calculates the largest bias during the austral summer. This indicates that the model is less accurate in timing the formation and dissipation of clouds during the summer, when higher water vapor quantities are present in the atmosphere than during the austral winter. Secondly, the model sensitivity on changing the microphysics, cumulus parameterization and land surface models on calculated GHI values is evaluated. The sensitivity simulations showed that changing the microphysics from the Thompson scheme (or Single-Moment 6-class scheme) to the Morrison double-moment scheme, the relative bias improves from 45% to 10%. The underlying reason for this improvement is that the Morrison double-moment scheme predicts the mass and number concentrations of five hydrometeors, which help to improve the calculation of the densities, size and lifetime of the cloud droplets. While the single moment schemes only predicts the mass for less hydrometeors. Changing the cumulus parameterization schemes and land surface models does not have a large impact on GHI calculations.
Parameterized data-driven fuzzy model based optimal control of a semi-batch reactor.
Kamesh, Reddi; Rani, K Yamuna
2016-09-01
A parameterized data-driven fuzzy (PDDF) model structure is proposed for semi-batch processes, and its application for optimal control is illustrated. The orthonormally parameterized input trajectories, initial states and process parameters are the inputs to the model, which predicts the output trajectories in terms of Fourier coefficients. Fuzzy rules are formulated based on the signs of a linear data-driven model, while the defuzzification step incorporates a linear regression model to shift the domain from input to output domain. The fuzzy model is employed to formulate an optimal control problem for single rate as well as multi-rate systems. Simulation study on a multivariable semi-batch reactor system reveals that the proposed PDDF modeling approach is capable of capturing the nonlinear and time-varying behavior inherent in the semi-batch system fairly accurately, and the results of operating trajectory optimization using the proposed model are found to be comparable to the results obtained using the exact first principles model, and are also found to be comparable to or better than parameterized data-driven artificial neural network model based optimization results. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.
Exploring the potential of machine learning to break deadlock in convection parameterization
Pritchard, M. S.; Gentine, P.
2017-12-01
We explore the potential of modern machine learning tools (via TensorFlow) to replace parameterization of deep convection in climate models. Our strategy begins by generating a large ( 1 Tb) training dataset from time-step level (30-min) output harvested from a one-year integration of a zonally symmetric, uniform-SST aquaplanet integration of the SuperParameterized Community Atmosphere Model (SPCAM). We harvest the inputs and outputs connecting each of SPCAM's 8,192 embedded cloud-resolving model (CRM) arrays to its host climate model's arterial thermodynamic state variables to afford 143M independent training instances. We demonstrate that this dataset is sufficiently large to induce preliminary convergence for neural network prediction of desired outputs of SP, i.e. CRM-mean convective heating and moistening profiles. Sensitivity of the machine learning convergence to the nuances of the TensorFlow implementation are discussed, as well as results from pilot tests from the neural network operating inline within the SPCAM as a replacement to the (super)parameterization of convection.
Energy Technology Data Exchange (ETDEWEB)
Charles, T.K. [School of Physics and Astronomy, Monash University, Clayton, Victoria, 3800 (Australia); Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria, 3168 (Australia); Paganin, D.M. [School of Physics and Astronomy, Monash University, Clayton, Victoria, 3800 (Australia); Dowd, R.T. [Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria, 3168 (Australia)
2016-08-21
Intrinsic emittance is often the limiting factor for brightness in fourth generation light sources and as such, a good understanding of the factors affecting intrinsic emittance is essential in order to be able to decrease it. Here we present a parameterization model describing the proportional increase in emittance induced by cathode surface roughness. One major benefit behind the parameterization approach presented here is that it takes the complexity of a Monte Carlo model and reduces the results to a straight-forward empirical model. The resulting models describe the proportional increase in transverse momentum introduced by surface roughness, and are applicable to various metal types, photon wavelengths, applied electric fields, and cathode surface terrains. The analysis includes the increase in emittance due to changes in the electric field induced by roughness as well as the increase in transverse momentum resultant from the spatially varying surface normal. We also compare the results of the Parameterization Model to an Analytical Model which employs various approximations to produce a more compact expression with the cost of a reduction in accuracy.
Parameterization of a Hydrological Model for a Large, Ungauged Urban Catchment
Directory of Open Access Journals (Sweden)
Gerald Krebs
2016-10-01
Full Text Available Urbanization leads to the replacement of natural areas by impervious surfaces and affects the catchment hydrological cycle with adverse environmental impacts. Low impact development tools (LID that mimic hydrological processes of natural areas have been developed and applied to mitigate these impacts. Hydrological simulations are one possibility to evaluate the LID performance but the associated small-scale processes require a highly spatially distributed and explicit modeling approach. However, detailed data for model development are often not available for large urban areas, hampering the model parameterization. In this paper we propose a methodology to parameterize a hydrological model to a large, ungauged urban area by maintaining at the same time a detailed surface discretization for direct parameter manipulation for LID simulation and a firm reliance on available data for model conceptualization. Catchment delineation was based on a high-resolution digital elevation model (DEM and model parameterization relied on a novel model regionalization approach. The impact of automated delineation and model regionalization on simulation results was evaluated for three monitored study catchments (5.87–12.59 ha. The simulated runoff peak was most sensitive to accurate catchment discretization and calibration, while both the runoff volume and the fit of the hydrograph were less affected.
Tsunami damping by mangrove forest: a laboratory study using parameterized trees
Directory of Open Access Journals (Sweden)
A. Strusińska-Correia
2013-02-01
Full Text Available Tsunami attenuation by coastal vegetation was examined under laboratory conditions for mature mangroves Rhizophora sp. The developed novel tree parameterization concept, accounting for both bio-mechanical and structural tree properties, allowed to substitute the complex tree structure by a simplified tree model of identical hydraulic resistance. The most representative parameterized mangrove model was selected among the tested models with different frontal area and root density, based on hydraulic test results. The selected parameterized tree models were arranged in a forest model of different width and further tested systematically under varying incident tsunami conditions (solitary waves and tsunami bores. The damping performance of the forest models under these two flow regimes was compared in terms of wave height and force envelopes, wave transmission coefficient as well as drag and inertia coefficients. Unlike the previous studies, the results indicate a significant contribution of the foreshore topography to solitary wave energy reduction through wave breaking in comparison to that attributed to the forest itself. A similar rate of tsunami transmission (ca. 20% was achieved for both flow conditions (solitary waves and tsunami bores and the widest forest (75 m in prototype investigated. Drag coefficient C_{D} attributed to the solitary waves tends to be constant (C_{D} = 1.5 over the investigated range of the Reynolds number.
Parameterization of Mixed Layer and Deep-Ocean Mesoscales Including Nonlinearity
Canuto, V. M.; Cheng, Y.; Dubovikov, M. S.; Howard, A. M.; Leboissetier, A.
2018-01-01
In 2011, Chelton et al. carried out a comprehensive census of mesoscales using altimetry data and reached the following conclusions: "essentially all of the observed mesoscale features are nonlinear" and "mesoscales do not move with the mean velocity but with their own drift velocity," which is "the most germane of all the nonlinear metrics."� Accounting for these results in a mesoscale parameterization presents conceptual and practical challenges since linear analysis is no longer usable and one needs a model of nonlinearity. A mesoscale parameterization is presented that has the following features: 1) it is based on the solutions of the nonlinear mesoscale dynamical equations, 2) it describes arbitrary tracers, 3) it includes adiabatic (A) and diabatic (D) regimes, 4) the eddy-induced velocity is the sum of a Gent and McWilliams (GM) term plus a new term representing the difference between drift and mean velocities, 5) the new term lowers the transfer of mean potential energy to mesoscales, 6) the isopycnal slopes are not as flat as in the GM case, 7) deep-ocean stratification is enhanced compared to previous parameterizations where being more weakly stratified allowed a large heat uptake that is not observed, 8) the strength of the Deacon cell is reduced. The numerical results are from a stand-alone ocean code with Coordinated Ocean-Ice Reference Experiment I (CORE-I) normal-year forcing.
DEFF Research Database (Denmark)
Cramer, Christian N; Kelstrup, Christian D; Olsen, Jesper V
2017-01-01
bonds are present in complicated patterns. This includes the presence of disulfide bonds in nested patterns and closely spaced cysteines. Unambiguous mapping of such disulfide bonds typically requires advanced MS approaches. In this study, we exploited in-source reduction (ISR) of disulfide bonds during...... the electrospray ionization process to facilitate disulfide bond assignments. We successfully developed a LC-ISR-MS/MS methodology to use as an online and fully automated partial reduction procedure. Postcolumn partial reduction by ISR provided fast and easy identification of peptides involved in disulfide bonding......Mapping of disulfide bonds is an essential part of protein characterization to ensure correct cysteine pairings. For this, mass spectrometry (MS) is the most widely used technique due to fast and accurate characterization. However, MS-based disulfide mapping is challenged when multiple disulfide...
Kim, M.; Harman, C. J.; Troch, P. A. A.
2017-12-01
Hillslopes have been extensively explored as a natural fundamental unit for spatially-integrated hydrologic models. Much of this attention has focused on their use in predicting the quantity of discharge, but hillslope-based models can potentially be used to predict the composition of discharge (in terms of age and chemistry) if they can be parameterized terms of measurable physical properties. Here we present advances in the use of rank StorAge Selection (rSAS) functions to parameterize transport through hillslopes. These functions provide a mapping between the distribution of water ages in storage and in outfluxes in terms of a probability distribution over storage. It has previously been shown that rSAS functions are related to the relative partitioning and arrangement of flow pathways (and variabilities in that arrangement), while separating out the effect of changes in the overall rate of fluxes in and out. This suggests that rSAS functions should have a connection to the internal organization of flow paths in a hillslope.Using a combination of numerical modeling and theoretical analysis we examined: first, the controls of physical properties on internal spatial organization of age (time since entry), life expectancy (time to exit), and the emergent transit time distribution and rSAS functions; second, the possible parameterization of the rSAS function using the physical properties. The numerical modeling results showed the clear dependence of the rSAS function forms on the physical properties and relations between the internal organization and the rSAS functions. For the different rates of the exponential saturated hydraulic conductivity decline with depth the spatial organization of life expectancy varied dramatically and determined the rSAS function forms, while the organizaiton of the age showed less qualitative differences. Analytical solutions predicting this spatial organization and the resulting rSAS function were derived for simplified systems. These
Aguilar, M.; Ali Cavasonza, L.; Alpat, B.; Ambrosi, G.; Arruda, L.; Attig, N.; Aupetit, S.; Azzarello, P.; Bachlechner, A.; Barao, F.; Barrau, A.; Barrin, L.; Bartoloni, A.; Basara, L.; Başeǧmez-du Pree, S.; Battarbee, M.; Battiston, R.; Becker, U.; Behlmann, M.; Beischer, B.; Berdugo, J.; Bertucci, B.; Bindel, K. F.; Bindi, V.; de Boer, W.; Bollweg, K.; Bonnivard, V.; Borgia, B.; Boschini, M. J.; Bourquin, M.; Bueno, E. F.; Burger, J.; Burger, W. J.; Cadoux, F.; Cai, X. D.; Capell, M.; Caroff, S.; Casaus, J.; Castellini, G.; Cervelli, F.; Chae, M. J.; Chang, Y. H.; Chen, A. I.; Chen, G. M.; Chen, H. S.; Cheng, L.; Chou, H. Y.; Choumilov, E.; Choutko, V.; Chung, C. H.; Clark, C.; Clavero, R.; Coignet, G.; Consolandi, C.; Contin, A.; Corti, C.; Creus, W.; Crispoltoni, M.; Cui, Z.; Dadzie, K.; Dai, Y. M.; Datta, A.; Delgado, C.; Della Torre, S.; Demakov, O.; Demirköz, M. B.; Derome, L.; Di Falco, S.; Dimiccoli, F.; Díaz, C.; von Doetinchem, P.; Dong, F.; Donnini, F.; Duranti, M.; D'Urso, D.; Egorov, A.; Eline, A.; Eronen, T.; Feng, J.; Fiandrini, E.; Fisher, P.; Formato, V.; Galaktionov, Y.; Gallucci, G.; García-López, R. J.; Gargiulo, C.; Gast, H.; Gebauer, I.; Gervasi, M.; Ghelfi, A.; Giovacchini, F.; Gómez-Coral, D. M.; Gong, J.; Goy, C.; Grabski, V.; Grandi, D.; Graziani, M.; Guo, K. H.; Haino, S.; Han, K. C.; He, Z. H.; Heil, M.; Hoffman, J.; Hsieh, T. H.; Huang, H.; Huang, Z. C.; Huh, C.; Incagli, M.; Ionica, M.; Jang, W. Y.; Jia, Yi; Jinchi, H.; Kang, S. C.; Kanishev, K.; Khiali, B.; Kim, G. N.; Kim, K. S.; Kirn, Th.; Konak, C.; Kounina, O.; Kounine, A.; Koutsenko, V.; Kulemzin, A.; La Vacca, G.; Laudi, E.; Laurenti, G.; Lazzizzera, I.; Lebedev, A.; Lee, H. T.; Lee, S. C.; Leluc, C.; Li, H. S.; Li, J. Q.; Li, Q.; Li, T. X.; Li, Y.; Li, Z. H.; Li, Z. Y.; Lim, S.; Lin, C. H.; Lipari, P.; Lippert, T.; Liu, D.; Liu, Hu; Lordello, V. D.; Lu, S. Q.; Lu, Y. S.; Luebelsmeyer, K.; Luo, F.; Luo, J. Z.; Lyu, S. S.; Machate, F.; Mañá, C.; Marín, J.; Martin, T.; Martínez, G.; Masi, N.; Maurin, D.; Menchaca-Rocha, A.; Meng, Q.; Mikuni, V. M.; Mo, D. C.; Mott, P.; Nelson, T.; Ni, J. Q.; Nikonov, N.; Nozzoli, F.; Oliva, A.; Orcinha, M.; Palmonari, F.; Palomares, C.; Paniccia, M.; Pauluzzi, M.; Pensotti, S.; Perrina, C.; Phan, H. D.; Picot-Clemente, N.; Pilo, F.; Pizzolotto, C.; Plyaskin, V.; Pohl, M.; Poireau, V.; Quadrani, L.; Qi, X. M.; Qin, X.; Qu, Z. Y.; Räihä, T.; Rancoita, P. G.; Rapin, D.; Ricol, J. S.; Rosier-Lees, S.; Rozhkov, A.; Rozza, D.; Sagdeev, R.; Schael, S.; Schmidt, S. M.; Schulz von Dratzig, A.; Schwering, G.; Seo, E. S.; Shan, B. S.; Shi, J. Y.; Siedenburg, T.; Son, D.; Song, J. W.; Tacconi, M.; Tang, X. W.; Tang, Z. C.; Tescaro, D.; Ting, Samuel C. C.; Ting, S. M.; Tomassetti, N.; Torsti, J.; Türkoǧlu, C.; Urban, T.; Vagelli, V.; Valente, E.; Valtonen, E.; Vázquez Acosta, M.; Vecchi, M.; Velasco, M.; Vialle, J. P.; Vitale, V.; Vitillo, S.; Wang, L. Q.; Wang, N. H.; Wang, Q. L.; Wang, X.; Wang, X. Q.; Wang, Z. X.; Wei, C. C.; Weng, Z. L.; Whitman, K.; Wu, H.; Wu, X.; Xiong, R. Q.; Xu, W.; Yan, Q.; Yang, J.; Yang, M.; Yang, Y.; Yi, H.; Yu, Y. J.; Yu, Z. Q.; Zannoni, M.; Zeissler, S.; Zhang, C.; Zhang, F.; Zhang, J.; Zhang, J. H.; Zhang, S. W.; Zhang, Z.; Zheng, Z. M.; Zhuang, H. L.; Zhukov, V.; Zichichi, A.; Zimmermann, N.; Zuccon, P.; AMS Collaboration
2017-12-01
We report the observation of new properties of primary cosmic rays He, C, and O measured in the rigidity (momentum/charge) range 2 GV to 3 TV with 90 ×106 helium, 8.4 ×106 carbon, and 7.0 ×106 oxygen nuclei collected by the Alpha Magnetic Spectrometer (AMS) during the first five years of operation. Above 60 GV, these three spectra have identical rigidity dependence. They all deviate from a single power law above 200 GV and harden in an identical way.
Serva, Federico; Cagnazzo, Chiara; Riccio, Angelo
2016-04-01
The effects of the propagation and breaking of atmospheric gravity waves have long been considered crucial for their impact on the circulation, especially in the stratosphere and mesosphere, between heights of 10 and 110 km. These waves, that in the Earth's atmosphere originate from surface orography (OGWs) or from transient (nonorographic) phenomena such as fronts and convective processes (NOGWs), have horizontal wavelengths between 10 and 1000 km, vertical wavelengths of several km, and frequencies spanning from minutes to hours. Orographic and nonorographic GWs must be accounted for in climate models to obtain a realistic simulation of the stratosphere in both hemispheres, since they can have a substantial impact on circulation and temperature, hence an important role in ozone chemistry for chemistry-climate models. Several types of parameterization are currently employed in models, differing in the formulation and for the values assigned to parameters, but the common aim is to quantify the effect of wave breaking on large-scale wind and temperature patterns. In the last decade, both global observations from satellite-borne instruments and the outputs of very high resolution climate models provided insight on the variability and properties of gravity wave field, and these results can be used to constrain some of the empirical parameters present in most parameterization scheme. A feature of the NOGW forcing that clearly emerges is the intermittency, linked with the nature of the sources: this property is absent in the majority of the models, in which NOGW parameterizations are uncoupled with other atmospheric phenomena, leading to results which display lower variability compared to observations. In this work, we analyze the climate simulated in AMIP runs of the MAECHAM5 model, which uses the Hines NOGW parameterization and with a fine vertical resolution suitable to capture the effects of wave-mean flow interaction. We compare the results obtained with two
Yang, J.; Gonzalez-Benecke, C. A.; Teskey, R. O.; Martin, T.; Jokela, E. J.
2015-12-01
Loblolly pine (Pinus taeda L.) is one of the fastest growing pine species. It has been planted on more than 10 million ha in the southeastern U.S., and also been introduced into many countries. Using data from the literature and long-term productivity studies, we re-parameterized the 3-PG model for loblolly pine stands. We developed new functions for estimating NPP allocation dynamics, canopy cover and needlefall dynamics, effects of frost on production, density-independent and density-dependent tree mortality, biomass pools at variable starting ages, and the fertility rating. New functions to estimate merchantable volume partitioning were also included, allowing for economic analyses. The fertility rating was determined as a function of site index (mean height of dominant trees at age=25 years). We used the largest and most geographically extensive validation dataset for this species ever used (91 pots in 12 states in U.S. and 10 plots in Uruguay). Comparison of modeled to measured data showed robust agreement across the natural range in the U.S., as well as in Uruguay, where the species is grown as an exotic. Using the new set of functions and parameters with downscaled projections from twenty different climate models, the model was applied to assess the impact of future climate change scenarios on stand productivity in the southeastern U.S.
International Nuclear Information System (INIS)
Tronstad, Christian; Martinsen, Ørjan G; Grimnes, Sverre; Pischke, Soeren E; Holhjem, Lars; Tønnessen, Tor Inge
2010-01-01
For detection of cardiac ischemia based on regional pCO 2 measurement, sensor drift becomes a problem when monitoring over several hours. A real-time drift correction algorithm was developed based on utilization of the time-derivative to distinguish between physiological responses and the drift, customized by measurements from a myocardial infarction porcine model (6 pigs, 23 sensors). IscAlert(TM) conductometric pCO 2 sensors were placed in the myocardial regions supplied by the left anterior descending coronary artery (LAD) and the left circumflex artery (LCX) while the LAD artery was fully occluded for 1, 3, 5 and 15 min leading to ischemia in the LAD-dependent region. The measured pCO 2 , the drift-corrected pCO 2 (ΔpCO 2 ) and its time-derivative (TDpCO 2 ) were compared with respect to detection ability. Baseline stability in the ΔpCO 2 led to earlier, more accurate detection. The TDpCO 2 featured the earliest sensitivity, but with a lower specificity. Combining ΔpCO 2 and TDpCO 2 enables increased accuracy. Suggestions are given for the utilization of the parameters for an automated early warning and alarming system. In conclusion, early detection of cardiac ischemia is feasible using the conductometric pCO 2 sensor together with parameterization methods
Barone, Vincenzo; Cacelli, Ivo; De Mitri, Nicola; Licari, Daniele; Monti, Susanna; Prampolini, Giacomo
2013-03-21
The Joyce program is augmented with several new features, including the user friendly Ulysses GUI, the possibility of complete excited state parameterization and a more flexible treatment of the force field electrostatic terms. A first validation is achieved by successfully comparing results obtained with Joyce2.0 to literature ones, obtained for the same set of benchmark molecules. The parameterization protocol is also applied to two other larger molecules, namely nicotine and a coumarin based dye. In the former case, the parameterized force field is employed in molecular dynamics simulations of solvated nicotine, and the solute conformational distribution at room temperature is discussed. Force fields parameterized with Joyce2.0, for both the dye's ground and first excited electronic states, are validated through the calculation of absorption and emission vertical energies with molecular mechanics optimized structures. Finally, the newly implemented procedure to handle polarizable force fields is discussed and applied to the pyrimidine molecule as a test case.
The urban land use in the COSMO-CLM model: a comparison of three parameterizations for Berlin
Directory of Open Access Journals (Sweden)
Kristina Trusilova
2016-05-01
Full Text Available The regional non-hydrostatic climate model COSMO-CLM is increasingly being used on fine spatial scales of 1–5 km. Such applications require a detailed differentiation between the parameterization for natural and urban land uses. Since 2010, three parameterizations for urban land use have been incorporated into COSMO-CLM. These parameterizations vary in their complexity, required city parameters and their computational cost. We perform model simulations with the COSMO-CLM coupled to these three parameterizations for urban land in the same model domain of Berlin on a 1-km grid and compare results with available temperature observations. While all models capture the urban heat island, they differ in spatial detail, magnitude and the diurnal variation.
Sraj, Ihab; Zedler, Sarah E.; Knio, Omar; Jackson, Charles S.; Hoteit, Ibrahim
2016-01-01
The authors present a polynomial chaos (PC)-based Bayesian inference method for quantifying the uncertainties of the K-profile parameterization (KPP) within the MIT general circulation model (MITgcm) of the tropical Pacific. The inference
Directory of Open Access Journals (Sweden)
B. Croft
2010-02-01
Full Text Available A diagnostic cloud nucleation scavenging scheme, which determines stratiform cloud scavenging ratios for both aerosol mass and number distributions, based on cloud droplet, and ice crystal number concentrations, is introduced into the ECHAM5-HAM global climate model. This scheme is coupled with a size-dependent in-cloud impaction scavenging parameterization for both cloud droplet-aerosol, and ice crystal-aerosol collisions. The aerosol mass scavenged in stratiform clouds is found to be primarily (>90% scavenged by cloud nucleation processes for all aerosol species, except for dust (50%. The aerosol number scavenged is primarily (>90% attributed to impaction. 99% of this impaction scavenging occurs in clouds with temperatures less than 273 K. Sensitivity studies are presented, which compare aerosol concentrations, burdens, and deposition for a variety of in-cloud scavenging approaches: prescribed fractions, a more computationally expensive prognostic aerosol cloud processing treatment, and the new diagnostic scheme, also with modified assumptions about in-cloud impaction and nucleation scavenging. Our results show that while uncertainties in the representation of in-cloud scavenging processes can lead to differences in the range of 20–30% for the predicted annual, global mean aerosol mass burdens, and near to 50% for accumulation mode aerosol number burden, the differences in predicted aerosol mass concentrations can be up to one order of magnitude, particularly for regions of the middle troposphere with temperatures below 273 K where mixed and ice phase clouds exist. Different parameterizations for impaction scavenging changed the predicted global, annual mean number removal attributed to ice clouds by seven-fold, and the global, annual dust mass removal attributed to impaction by two orders of magnitude. Closer agreement with observations of black carbon profiles from aircraft (increases near to one order of magnitude for mixed phase clouds
Moshonkin, Sergey; Gusev, Anatoly; Zalesny, Vladimir; Diansky, Nikolay
2017-04-01
Series of experiments were performed with a three-dimensional, free surface, sigma coordinate eddy-permitting ocean circulation model for Atlantic (from 30°S) - Arctic and Bering sea domain (0.25 degrees resolution, Institute of Numerical Mathematics Ocean Model or INMOM) using vertical grid refinement in the zone of fully developed turbulence (40 sigma-levels). The model variables are horizontal velocity components, potential temperature, and salinity as well as free surface height. For parameterization of viscosity and diffusivity, the original splitting turbulence algorithm (STA) is used when total evolutionary equations for the turbulence kinetic energy (TKE) and turbulence dissipation frequency (TDF) split into the stages of transport-diffusion and generation-dissipation. For the generation-dissipation stage the analytical solution was obtained for TKE and TDF as functions of the buoyancy and velocity shift frequencies (BF and VSF). The proposed model with STA is similar to the contemporary differential turbulence models, concerning the physical formulations. At the same time, its algorithm has high enough computational efficiency. For mixing simulation in the zone of turbulence decay, the two kind numerical experiments were carried out, as with assimilation of annual mean climatic buoyancy frequency, as with variation of Prandtl number function dependence upon the BF, VSF, TKE and TDF. The CORE-II data for 1948-2009 were used for experiments. Quality of temperature T and salinity S structure simulation is estimated by the comparison of model monthly profiles T and S averaged for 1980-2009, with T and S monthly data from the World Ocean Atlas 2013. Form of coefficients in equations for TKE and TDF on the generation-dissipation stage makes it possible to assimilate annual mean climatic buoyancy frequency in a varying degree that cardinally improves adequacy of model results to climatic data in all analyzed model domain. The numerical experiments with modified
Uncertainties of parameterized surface downward clear-sky shortwave and all-sky longwave radiation.
Gubler, S.; Gruber, S.; Purves, R. S.
2012-06-01
As many environmental models rely on simulating the energy balance at the Earth's surface based on parameterized radiative fluxes, knowledge of the inherent model uncertainties is important. In this study we evaluate one parameterization of clear-sky direct, diffuse and global shortwave downward radiation (SDR) and diverse parameterizations of clear-sky and all-sky longwave downward radiation (LDR). In a first step, SDR is estimated based on measured input variables and estimated atmospheric parameters for hourly time steps during the years 1996 to 2008. Model behaviour is validated using the high quality measurements of six Alpine Surface Radiation Budget (ASRB) stations in Switzerland covering different elevations, and measurements of the Swiss Alpine Climate Radiation Monitoring network (SACRaM) in Payerne. In a next step, twelve clear-sky LDR parameterizations are calibrated using the ASRB measurements. One of the best performing parameterizations is elected to estimate all-sky LDR, where cloud transmissivity is estimated using measured and modeled global SDR during daytime. In a last step, the performance of several interpolation methods is evaluated to determine the cloud transmissivity in the night. We show that clear-sky direct, diffuse and global SDR is adequately represented by the model when using measurements of the atmospheric parameters precipitable water and aerosol content at Payerne. If the atmospheric parameters are estimated and used as a fix value, the relative mean bias deviance (MBD) and the relative root mean squared deviance (RMSD) of the clear-sky global SDR scatter between between -2 and 5%, and 7 and 13% within the six locations. The small errors in clear-sky global SDR can be attributed to compensating effects of modeled direct and diffuse SDR since an overestimation of aerosol content in the atmosphere results in underestimating the direct, but overestimating the diffuse SDR. Calibration of LDR parameterizations to local conditions
Uncertainties of parameterized surface downward clear-sky shortwave and all-sky longwave radiation.
Directory of Open Access Journals (Sweden)
S. Gubler
2012-06-01
Full Text Available As many environmental models rely on simulating the energy balance at the Earth's surface based on parameterized radiative fluxes, knowledge of the inherent model uncertainties is important. In this study we evaluate one parameterization of clear-sky direct, diffuse and global shortwave downward radiation (SDR and diverse parameterizations of clear-sky and all-sky longwave downward radiation (LDR. In a first step, SDR is estimated based on measured input variables and estimated atmospheric parameters for hourly time steps during the years 1996 to 2008. Model behaviour is validated using the high quality measurements of six Alpine Surface Radiation Budget (ASRB stations in Switzerland covering different elevations, and measurements of the Swiss Alpine Climate Radiation Monitoring network (SACRaM in Payerne. In a next step, twelve clear-sky LDR parameterizations are calibrated using the ASRB measurements. One of the best performing parameterizations is elected to estimate all-sky LDR, where cloud transmissivity is estimated using measured and modeled global SDR during daytime. In a last step, the performance of several interpolation methods is evaluated to determine the cloud transmissivity in the night.
We show that clear-sky direct, diffuse and global SDR is adequately represented by the model when using measurements of the atmospheric parameters precipitable water and aerosol content at Payerne. If the atmospheric parameters are estimated and used as a fix value, the relative mean bias deviance (MBD and the relative root mean squared deviance (RMSD of the clear-sky global SDR scatter between between −2 and 5%, and 7 and 13% within the six locations. The small errors in clear-sky global SDR can be attributed to compensating effects of modeled direct and diffuse SDR since an overestimation of aerosol content in the atmosphere results in underestimating the direct, but overestimating the diffuse SDR. Calibration of LDR parameterizations
International Nuclear Information System (INIS)
Mc Carthy, P.J.; Sengupta, A.; Geiger, J.; Werner, A.
2005-01-01
The W7-X stellarator, under construction at IPP-Greifswald, is being designed to demonstrate the steady state capability of fusion devices. Due to the pulse length involved, real time monitoring and control of the discharges is a crucial issue in steady state operations. For W7-X, we have planned a sequence of in-depth analyses of the magnetic configurations which, ultimately, will lead to a proper understanding of plasma equilibrium, stability and transport. It should also provide insight into the parameterization of the various plasma-related quantities which is important from the point of view of real time study. The first step in our sequence of analyses involved a study of the vacuum configuration, including the detectable magnetic islands, of W7-X. We now proceed to the scenario at finite beta considering full magnetohydrodynamic (MHD) equilibria based on vmec2000 calculations. A database of order 10000 equilibria was calculated on the same parameter space for the coil current ratios. The parameters which were varied randomly and independently consist of the external coil current ratios (6), the parameters of the profiles (as functions of normalised toroidal flux) of plasma pressure and toroidal current (4+4) and the plasma size (a eff ) which is required to vary the plasma volume. A statistical analysis, using Function Parametrization (FP), was performed on a sample of well-converged equilibria. The plasma parameters were varied to allow a good FP for the expected values in W7-X, i.e. volume-averaged up to 5% and toroidal net-current of up to ±50 kA for a mean field strength of about 2 T throughout the database. The profiles were chosen as a sequence of polynomials with the property that the addition of a higher order polynomial would not change the lower order volume-averaged moments of the resulting profile. The aim of this was to try to avoid cross correlations in the independent input parameters for the database generation. However, some restrictions
Alwood, Joshua S.; Tran, Luan H.; Schreurs, Ann-Sofie; Shirazi-Fard, Yasaman; Kumar, Akhilesh; Hilton, Diane; Tahimic, Candice G. T.; Globus, Ruth
2017-01-01
Exposure to space radiation may pose a risk to skeletal health during subsequent aging. Irradiation acutely stimulates bone remodeling in mice, although the long-term influence of space radiation on bone-forming potential (osteoblastogenesis) and possible adaptive mechanisms are not well understood. We hypothesized exposure to ionizing radiation impairs osteoblastogenesis in an ion-type specific manner, with low doses capable of modulating expression of redox-related genes. 16-week old, male, C57BL6/J mice were exposed to low linear-energy-transfer (LET) protons (150 mega electron volts per nucleon) or high-LET (sup 56) Fe ions (600 mega electron volts per nucleon) using either low (5 or 10 centigrays) or high (50 or 200 centigrays) doses at NASAs Space Radiation Lab at Brookhaven National Lab (NSRL/BNL). Tissues were harvested 5 weeks or 1 year after irradiation and bones were analyzed by microcomputed tomography for cancellous microarchitecture and cortical geometry. Marrow-derived, adherent cells were grown under osteoblastogenic culture conditions. Cell lysates were analyzed for select groups by RT-PCR (Reverse Transcription-Polymerase Chain Reaction) during the proliferative phase or the mineralizing phase, and differentiation was analyzed by imaging mineralized nodules (percentage surface area). Representative genes were selected for expression analyses, including cell proliferation (PCNA, Cdk2, p21, p53), differentiation (Runx2, Alpl, Bglap), oxidative metabolism (Catalase, GPX, MnSOD, CuZnSOD, iNos, Foxo1), DNA-damage repair (Gadd45), or apoptosis (Caspase 3). As expected, a high dose (200 centigrays), but not low doses, of either (sup 56) Fe or protons caused a loss of cancellous bone volume per total volume. Marrow cells produced mineralized nodules ex vivo regardless of radiation type or dose; (sup 56) Fe (200 centigrays) inhibited median nodule area by more than 90 percent at 5 weeks and 1 year post-irradiation, compared to controls. At 5 weeks post
Wong, J.; Barth, M. C.; Noone, D. C.
2012-12-01
Lightning-generated nitrogen oxides (LNOx) is an important precursor to tropospheric ozone production. With a meteorological time-scale variability similar to that of the ozone chemical lifetime, it can nonlinearly perturb tropospheric ozone concentration. Coupled with upper-air circulation patterns, LNOx can accumulate in significant amount in the upper troposphere with other precursors, thus enhancing ozone production (see attached figure). While LNOx emission has been included and tuned extensively in global climate models, its inclusions in regional chemistry models are seldom tested. Here we present a study that evaluates the frequently used Price and Rind parameterization based on cloud-top height at resolutions that partially resolve deep convection using the Weather Research and Forecasting model with Chemistry (WRF-Chem) over the contiguous United States. With minor modifications, the parameterization is shown to generate integrated flash counts close to those observed. However, the modeled frequency distribution of cloud-to-ground flashes do not represent well for storms with high flash rates, bringing into question the applicability of the intra-cloud/ground partitioning (IC:CG) formulation of Price and Rind in some studies. Resolution dependency also requires attention when sub-grid cloud-tops are used instead of the originally intended grid-averaged cloud-top. LNOx passive tracers being gathered by monsoonal upper tropospheric anticyclone.
Abdulsttar, Marwah M.; Al-Rubaiee, A. A.; Ali, Abdul Halim Kh.
2016-01-01
Cherenkov light lateral distribution function (CLLDF) simulation was fulfilled using CORSIKA code for configurations of Tunka EAS array of different zenith angles. The parameterization of the CLLDF was carried out as a function of the distance from the shower core in extensive air showers (EAS) and zenith angle on the basis of the CORSIKA simulation of primary proton around the knee region with the energy 3.10^15 eV at different zenith angles. The parameterized CLLDF is verified in comparison...
Quantum mechanics on space with SU(2) fuzziness
Energy Technology Data Exchange (ETDEWEB)
Fatollahi, Amir H.; Shariati, Ahmad; Khorrami, Mohammad [Alzahra University, Department of Physics, Tehran (Iran)
2009-04-15
Quantum mechanics of models is considered which are constructed in spaces with Lie algebra type commutation relations between spatial coordinates. The case is specialized to that of the group SU(2), for which the formulation of the problem via the Euler parameterization is also presented. SU(2)-invariant systems are discussed, and the corresponding eigenvalue problem for the Hamiltonian is reduced to an ordinary differential equation, as is the case with such models on commutative spaces. (orig.)
Quantum mechanics on space with SU(2) fuzziness
International Nuclear Information System (INIS)
Fatollahi, Amir H.; Shariati, Ahmad; Khorrami, Mohammad
2009-01-01
Quantum mechanics of models is considered which are constructed in spaces with Lie algebra type commutation relations between spatial coordinates. The case is specialized to that of the group SU(2), for which the formulation of the problem via the Euler parameterization is also presented. SU(2)-invariant systems are discussed, and the corresponding eigenvalue problem for the Hamiltonian is reduced to an ordinary differential equation, as is the case with such models on commutative spaces. (orig.)
Directory of Open Access Journals (Sweden)
Sun Chao
2011-03-01
Full Text Available Abstract In the adult visual system, functionally distinct retinal ganglion cells (RGCs within each eye project to discrete targets in the brain. In the ferret, RGCs encoding light increments or decrements project to independent On and Off sublaminae within each eye-specific layer of the dorsal lateral geniculate nucleus (dLGN. Here we report a manipulation of retinal circuitry that alters RGC action potential firing patterns during development and eliminates the anatomical markers of segregated On and Off sublaminae in the LGN, including the intersublaminar spaces and the expression of a glial-associated inhibitory molecule, ABAKAN, normally separating On and Off leaflets. Despite the absence of anatomically defined On and Off sublaminae, electrophysiological recordings in the dLGN reveal that On and Off dLGN cells are segregated normally. These data demonstrate a dissociation between normal anatomical sublamination and segregation of function in the dLGN and call into question a purported role for ABAKAN boundaries in the developing visual system.
Scherer, G F E; Pietrzyk, P
2014-01-01
Arabidopsis roots on 45° tilted agar in 1-g grow in wave-like figures. In addition to waves, formation of root coils is observed in several mutants compromised in gravitropism and/or auxin transport. The knockdown mutant ppla-I-1 of patatin-related phospholipase-A-I is delayed in root gravitropism and forms increased numbers of root coils. Three known factors contribute to waving: circumnutation, gravisensing and negative thigmotropism. In microgravity, deprivation of wild type (WT) and mutant roots of gravisensing and thigmotropism and circumnutation (known to slow down in microgravity, and could potentially lead to fewer waves or increased coiling in both WT and mutant). To resolve this, mutant ppla-I-1 and WT were grown in the BIOLAB facility in the International Space Station. In 1-g, roots of both types only showed waving. In the first experiment in microgravity, the mutant after 9 days formed far more coils than in 1-g but the WT also formed several coils. After 24 days in microgravity, in both types the coils were numerous with slightly more in the mutant. In the second experiment, after 9 days in microgravity only the mutant formed coils and the WT grew arcuated roots. Cell file rotation (CFR) on the mutant root surface in microgravity decreased in comparison to WT, and thus was not important for coiling. Several additional developmental responses (hypocotyl elongation, lateral root formation, cotyledon expansion) were found to be gravity-influenced. We tentatively discuss these in the context of disturbances in auxin transport, which are known to decrease through lack of gravity. © 2013 German Botanical Society and The Royal Botanical Society of the Netherlands.
Directory of Open Access Journals (Sweden)
Muthuraj R.
2012-01-01
Full Text Available A mathematical model is developed to examine the effect of chemical reaction on MHD mixed convective heat and mass transfer flow of a couple-stress fluid in vertical porous space in the presence of temperature dependent heat source with travelling thermal waves. The dimensionless governing equations are assumed to be made up of two parts: a mean part corresponding to the fully developed mean flow, and a small perturbed part, using amplitude as a small parameter. The analytical solution of perturbed part have been carried out by using the long-wave approximation. The expressions for the zeroth-order and the first order solutions are obtained and the results of the heat and mass transfer characteristics are presented graphically for various values of parameters entering into the problem. It is noted that velocity of the fluid increases with the increase of the couple stress parameter and increasing the chemical reaction parameter leads suppress the velocity of the fluid. Cross velocity decreases with an increase of the phase angle. The increase of the chemical reaction parameter and Schmidt number lead to decrease the fluid concentration. The hydrodynamic case for a non-porous space in the absence of the temperature dependent heat source for Newtonian fluid can be captured as a limiting case of our analysis by taking, and α1→0, Da→∞, a→∞.
Honeyager, Ryan
High frequency microwave instruments are increasingly used to observe ice clouds and snow. These instruments are significantly more sensitive than conventional precipitation radar. This is ideal for analyzing ice-bearing clouds, for ice particles are tenuously distributed and have effective densities that are far less than liquid water. However, at shorter wavelengths, the electromagnetic response of ice particles is no longer solely dependent on particle mass. The shape of the ice particles also plays a significant role. Thus, in order to understand the observations of high frequency microwave radars and radiometers, it is essential to model the scattering properties of snowflakes correctly. Several research groups have proposed detailed models of snow aggregation. These particle models are coupled with computer codes that determine the particles' electromagnetic properties. However, there is a discrepancy between the particle model outputs and the requirements of the electromagnetic models. Snowflakes have countless variations in structure, but we also know that physically similar snowflakes scatter light in much the same manner. Structurally exact electromagnetic models, such as the discrete dipole approximation (DDA), require a high degree of structural resolution. Such methods are slow, spending considerable time processing redundant (i.e. useless) information. Conversely, when using techniques that incorporate too little structural information, the resultant radiative properties are not physically realistic. Then, we ask the question, what features are most important in determining scattering? This dissertation develops a general technique that can quickly parameterize the important structural aspects that determine the scattering of many diverse snowflake morphologies. A Voronoi bounding neighbor algorithm is first employed to decompose aggregates into well-defined interior and surface regions. The sensitivity of scattering to interior randomization is then
Given a time series of potential evapotranspiration and rainfall data, there are at least two approaches for estimating vertical percolation rates. One approach involves solving Richards' equation (RE) with a plant uptake model. An alternative approach involves applying a simple soil moisture accoun...
Hanson-Heine, Magnus W. D.; George, Michael W.; Besley, Nicholas A.
2018-06-01
The restricted excitation subspace approximation is explored as a basis to reduce the memory storage required in linear response time-dependent density functional theory (TDDFT) calculations within the Tamm-Dancoff approximation. It is shown that excluding the core orbitals and up to 70% of the virtual orbitals in the construction of the excitation subspace does not result in significant changes in computed UV/vis spectra for large molecules. The reduced size of the excitation subspace greatly reduces the size of the subspace vectors that need to be stored when using the Davidson procedure to determine the eigenvalues of the TDDFT equations. Furthermore, additional screening of the two-electron integrals in combination with a reduction in the size of the numerical integration grid used in the TDDFT calculation leads to significant computational savings. The use of these approximations represents a simple approach to extend TDDFT to the study of large systems and make the calculations increasingly tractable using modest computing resources.
WRF model sensitivity to choice of parameterization: a study of the `York Flood 1999'
Remesan, Renji; Bellerby, Tim; Holman, Ian; Frostick, Lynne
2015-10-01
Numerical weather modelling has gained considerable attention in the field of hydrology especially in un-gauged catchments and in conjunction with distributed models. As a consequence, the accuracy with which these models represent precipitation, sub-grid-scale processes and exceptional events has become of considerable concern to the hydrological community. This paper presents sensitivity analyses for the Weather Research Forecast (WRF) model with respect to the choice of physical parameterization schemes (both cumulus parameterisation (CPSs) and microphysics parameterization schemes (MPSs)) used to represent the `1999 York Flood' event, which occurred over North Yorkshire, UK, 1st-14th March 1999. The study assessed four CPSs (Kain-Fritsch (KF2), Betts-Miller-Janjic (BMJ), Grell-Devenyi ensemble (GD) and the old Kain-Fritsch (KF1)) and four MPSs (Kessler, Lin et al., WRF single-moment 3-class (WSM3) and WRF single-moment 5-class (WSM5)] with respect to their influence on modelled rainfall. The study suggests that the BMJ scheme may be a better cumulus parameterization choice for the study region, giving a consistently better performance than other three CPSs, though there are suggestions of underestimation. The WSM3 was identified as the best MPSs and a combined WSM3/BMJ model setup produced realistic estimates of precipitation quantities for this exceptional flood event. This study analysed spatial variability in WRF performance through categorical indices, including POD, FBI, FAR and CSI during York Flood 1999 under various model settings. Moreover, the WRF model was good at predicting high-intensity rare events over the Yorkshire region, suggesting it has potential for operational use.
Singh, K. S.; Bonthu, Subbareddy; Purvaja, R.; Robin, R. S.; Kannan, B. A. M.; Ramesh, R.
2018-04-01
This study attempts to investigate the real-time prediction of a heavy rainfall event over the Chennai Metropolitan City, Tamil Nadu, India that occurred on 01 December 2015 using Advanced Research Weather Research and Forecasting (WRF-ARW) model. The study evaluates the impact of six microphysical (Lin, WSM6, Goddard, Thompson, Morrison and WDM6) parameterization schemes of the model on prediction of heavy rainfall event. In addition, model sensitivity has also been evaluated with six Planetary Boundary Layer (PBL) and two Land Surface Model (LSM) schemes. Model forecast was carried out using nested domain and the impact of model horizontal grid resolutions were assessed at 9 km, 6 km and 3 km. Analysis of the synoptic features using National Center for Environmental Prediction Global Forecast System (NCEP-GFS) analysis data revealed strong upper-level divergence and high moisture content at lower level were favorable for the occurrence of heavy rainfall event over the northeast coast of Tamil Nadu. The study signified that forecasted rainfall was more sensitive to the microphysics and PBL schemes compared to the LSM schemes. The model provided better forecast of the heavy rainfall event using the logical combination of Goddard microphysics, YSU PBL and Noah LSM schemes, and it was mostly attributed to timely initiation and development of the convective system. The forecast with different horizontal resolutions using cumulus parameterization indicated that the rainfall prediction was not well represented at 9 km and 6 km. The forecast with 3 km horizontal resolution provided better prediction in terms of timely initiation and development of the event. The study highlights that forecast of heavy rainfall events using a high-resolution mesoscale model with suitable representations of physical parameterization schemes are useful for disaster management and planning to minimize the potential loss of life and property.
A Parameterization of Dry Thermals and Shallow Cumuli for Mesoscale Numerical Weather Prediction
Pergaud, Julien; Masson, Valéry; Malardel, Sylvie; Couvreux, Fleur
2009-07-01
For numerical weather prediction models and models resolving deep convection, shallow convective ascents are subgrid processes that are not parameterized by classical local turbulent schemes. The mass flux formulation of convective mixing is now largely accepted as an efficient approach for parameterizing the contribution of larger plumes in convective dry and cloudy boundary layers. We propose a new formulation of the EDMF scheme (for Eddy DiffusivityMass Flux) based on a single updraft that improves the representation of dry thermals and shallow convective clouds and conserves a correct representation of stratocumulus in mesoscale models. The definition of entrainment and detrainment in the dry part of the updraft is original, and is specified as proportional to the ratio of buoyancy to vertical velocity. In the cloudy part of the updraft, the classical buoyancy sorting approach is chosen. The main closure of the scheme is based on the mass flux near the surface, which is proportional to the sub-cloud layer convective velocity scale w *. The link with the prognostic grid-scale cloud content and cloud cover and the projection on the non- conservative variables is processed by the cloud scheme. The validation of this new formulation using large-eddy simulations focused on showing the robustness of the scheme to represent three different boundary layer regimes. For dry convective cases, this parameterization enables a correct representation of the countergradient zone where the mass flux part represents the top entrainment (IHOP case). It can also handle the diurnal cycle of boundary-layer cumulus clouds (EUROCSARM) and conserve a realistic evolution of stratocumulus (EUROCSFIRE).
Modelling and parameterizing the influence of tides on ice-shelf melt rates
Jourdain, N.; Molines, J. M.; Le Sommer, J.; Mathiot, P.; de Lavergne, C.; Gurvan, M.; Durand, G.
2017-12-01
Significant Antarctic ice sheet thinning is observed in several sectors of Antarctica, in particular in the Amundsen Sea sector, where warm circumpolar deep waters affect basal melting. The later has the potential to trigger marine ice sheet instabilities, with an associated potential for rapid sea level rise. It is therefore crucial to simulate and understand the processes associated with ice-shelf melt rates. In particular, the absence of tides representation in ocean models remains a caveat of numerous ocean hindcasts and climate projections. In the Amundsen Sea, tides are relatively weak and the melt-induced circulation is stronger than the tidal circulation. Using a regional 1/12° ocean model of the Amundsen Sea, we nonetheless find that tides can increase melt rates by up to 36% in some ice-shelf cavities. Among the processes that can possibly affect melt rates, the most important is an increased exchange at the ice/ocean interface resulting from the presence of strong tidal currents along the ice drafts. Approximately a third of this effect is compensated by a decrease in thermal forcing along the ice draft, which is related to an enhanced vertical mixing in the ocean interior in presence of tides. Parameterizing the effect of tides is an alternative to the representation of explicit tides in an ocean model, and has the advantage not to require any filtering of ocean model outputs. We therefore explore different ways to parameterize the effects of tides on ice shelf melt. First, we compare several methods to impose tidal velocities along the ice draft. We show that getting a realistic spatial distribution of tidal velocities in important, and can be deduced from the barotropic velocities of a tide model. Then, we explore several aspects of parameterized tidal mixing to reproduce the tide-induced decrease in thermal forcing along the ice drafts.
Morphing methods to parameterize specimen-specific finite element model geometries.
Sigal, Ian A; Yang, Hongli; Roberts, Michael D; Downs, J Crawford
2010-01-19
Shape plays an important role in determining the biomechanical response of a structure. Specimen-specific finite element (FE) models have been developed to capture the details of the shape of biological structures and predict their biomechanics. Shape, however, can vary considerably across individuals or change due to aging or disease, and analysis of the sensitivity of specimen-specific models to these variations has proven challenging. An alternative to specimen-specific representation has been to develop generic models with simplified geometries whose shape is relatively easy to parameterize, and can therefore be readily used in sensitivity studies. Despite many successful applications, generic models are limited in that they cannot make predictions for individual specimens. We propose that it is possible to harness the detail available in specimen-specific models while leveraging the power of the parameterization techniques common in generic models. In this work we show that this can be accomplished by using morphing techniques to parameterize the geometry of specimen-specific FE models such that the model shape can be varied in a controlled and systematic way suitable for sensitivity analysis. We demonstrate three morphing techniques by using them on a model of the load-bearing tissues of the posterior pole of the eye. We show that using relatively straightforward procedures these morphing techniques can be combined, which allows the study of factor interactions. Finally, we illustrate that the techniques can be used in other systems by applying them to morph a femur. Morphing techniques provide an exciting new possibility for the analysis of the biomechanical role of shape, independently or in interaction with loading and material properties. Copyright 2009 Elsevier Ltd. All rights reserved.
Multisite Evaluation of APEX for Water Quality: I. Best Professional Judgment Parameterization.
Baffaut, Claire; Nelson, Nathan O; Lory, John A; Senaviratne, G M M M Anomaa; Bhandari, Ammar B; Udawatta, Ranjith P; Sweeney, Daniel W; Helmers, Matt J; Van Liew, Mike W; Mallarino, Antonio P; Wortmann, Charles S
2017-11-01
The Agricultural Policy Environmental eXtender (APEX) model is capable of estimating edge-of-field water, nutrient, and sediment transport and is used to assess the environmental impacts of management practices. The current practice is to fully calibrate the model for each site simulation, a task that requires resources and data not always available. The objective of this study was to compare model performance for flow, sediment, and phosphorus transport under two parameterization schemes: a best professional judgment (BPJ) parameterization based on readily available data and a fully calibrated parameterization based on site-specific soil, weather, event flow, and water quality data. The analysis was conducted using 12 datasets at four locations representing poorly drained soils and row-crop production under different tillage systems. Model performance was based on the Nash-Sutcliffe efficiency (NSE), the coefficient of determination () and the regression slope between simulated and measured annualized loads across all site years. Although the BPJ model performance for flow was acceptable (NSE = 0.7) at the annual time step, calibration improved it (NSE = 0.9). Acceptable simulation of sediment and total phosphorus transport (NSE = 0.5 and 0.9, respectively) was obtained only after full calibration at each site. Given the unacceptable performance of the BPJ approach, uncalibrated use of APEX for planning or management purposes may be misleading. Model calibration with water quality data prior to using APEX for simulating sediment and total phosphorus loss is essential. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.
Energy Technology Data Exchange (ETDEWEB)
Haubrock, J.
2007-12-13
Fuel cells are a very promising technology for energy conversion. For optimization purpose, useful simulation tools are needs. Simulation tools should simulate the static and dynamic electrical behaviour and the models should parameterized by measurment results which should be done easily. In this dissertation, a useful model for simulating a pem fuel cell is developed. the model should parametrizes by V-I curve measurment and by current step respond. The model based on electrical equivalent circuits and it is shown, that it is possible to simulate the dynamic behaviour of a pem fuel cell stack. The simulation results are compared by measurment results. (orig.)
DEFF Research Database (Denmark)
Yoon, Gil Ho; Kim, Y.Y.; Langelaar, M.
2008-01-01
The internal element connectivity parameterization (I-ECP) method is an alternative approach to overcome numerical instabilities associated with low-stiffness element states in non-linear problems. In I-ECP, elements are connected by zero-length links while their link stiffness values are varied....... Therefore, it is important to interpolate link stiffness properly to obtain stably converging results. The main objective of this work is two-fold (1) the investigation of the relationship between the link stiffness and the stiffness of a domain-discretizing patch by using a discrete model and a homogenized...
Magic neutrino mass matrix and the Bjorken-Harrison-Scott parameterization
International Nuclear Information System (INIS)
Lam, C.S.
2006-01-01
Observed neutrino mixing can be described by a tribimaximal MNS matrix. The resulting neutrino mass matrix in the basis of a diagonal charged lepton mass matrix is both 2-3 symmetric and magic. By a magic matrix, I mean one whose row sums and column sums are all identical. I study what happens if 2-3 symmetry is broken but the magic symmetry is kept intact. In that case, the mixing matrix is parameterized by a single complex parameter U e3 , in a form discussed recently by Bjorken, Harrison, and Scott
Physically sound parameterization of incomplete ionization in aluminum-doped silicon
Directory of Open Access Journals (Sweden)
Heiko Steinkemper
2016-12-01
Full Text Available Incomplete ionization is an important issue when modeling silicon devices featuring aluminum-doped p+ (Al-p+ regions. Aluminum has a rather deep state in the band gap compared to boron or phosphorus, causing strong incomplete ionization. In this paper, we considerably improve our recent parameterization [Steinkemper et al., J. Appl. Phys. 117, 074504 (2015]. On the one hand, we found a fundamental criterion to further reduce the number of free parameters in our fitting procedure. And on the other hand, we address a mistake in the original publication of the incomplete ionization formalism in Altermatt et al., J. Appl. Phys. 100, 113715 (2006.
Real-time image parameterization in high energy gamma-ray astronomy using transputers
International Nuclear Information System (INIS)
Punch, M.; Fegan, D.J.
1991-01-01
Recently, significant advances in Very-High-Energy gamma-ray astronomy have been made by parameterization