bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mediterranean Forecasting System: An improved assimilation scheme for sea‐level anomaly and its validation
Authors: Dobricic S. , Pinardi N. , Adani M. , Bonazzi A. , Fratianni C. , Tonani M. 
Published: August 2006

AbstractThe assimilation of satellite and in situ data in the Mediterranean Forecast System (MFS) is based on an optimal interpolation scheme which uses empirical orthogonal functions (EOFs) to represent vertical modes of the background‐error correlation matrix. In this study we present a new methodology to estimate, and the calculation of, these multivariate EOFs. The new EOFs are considered time and space varying (seasonal time‐scales and subregional). They examine the vertical‐error cross‐variance between temperature, salinity, barotropic stream function and sea‐level anomaly. These EOFs are used to assimilate four years of along‐track sea‐level anomaly data. The validation of MFS analyses and forecasts using the assimilation system diagnostics and the comparison with independent observations show that, in relation to an old operational scheme which was using only one EOF, the use of several multivariate EOFs significantly improves the accuracy of analyses and forecasts in the Mediterranean. Copyright © 2005 Royal Meteorological Society
Diagnosis of observation, background and analysis‐error statistics in observation space
Authors: Desroziers G. , Berre L. , Chapnik B. , Poli P. 
Published: August 2006

AbstractMost operational assimilation schemes rely on linear estimation theory. Under this assumption, it is shown how simple consistency diagnostics can be obtained for the covariances of observation, background and estimation errors in observation space. Those diagnostics are shown to be nearly cost‐free since they only combine quantities available after the analysis, i.e. observed values and their background and analysis counterparts in observation space. A first application of such diagnostics is presented on analyses provided by the French 4D‐Var assimilation. A procedure to refine background and observation‐error variances is also proposed and tested in a simple toy analysis problem. The possibility to diagnose cross‐correlations between observation errors is also investigated in this same simple framework. A spectral interpretation of the diagnosed covariances is finally presented, which allows us to highlight the role of the scale separation between background and observation errors. Copyright © 2005 Royal Meteorological Society
Issues in targeted observing
Authors: Langland Rolf H. 
Published: August 2006

AbstractThis paper summarizes successes and limitations of targeted observing field programmes starting from the Fronts and Atlantic Storm‐Track Experiment in 1997 through recent programmes targeting winter storms and tropical cyclones. These field programmes have produced average reductions in short‐range forecast errors of about 10 per cent over regional verification areas, and maximum forecast error reductions as large as 50 per cent in certain cases. The majority of targeting cases investigated so far involve sets of dropsondes and other observation data that provide partial coverage of target areas. The primary scientific challenges for targeting include the refinement of objective methods that can identify optimal times and locations for targeted observations, as well as identify the specific types of satellite and in situ measurements that are required for the improvement of numerical weather forecasts. The most advanced targeting procedures, at present, include: the ensemble transform Kalman Filter, Hessian singular vectors, and observation‐space targeting using the adjoint of a variational data assimilation procedure. Targeted observing remains an active research topic in numerical weather prediction, with plans for continued refinement of objective targeting procedures, and field tests of new satellite and in situ observing systems. Copyright © 2005 Royal Meteorological Society
Bias and data assimilation
Authors: Dee D. P. 
Published: August 2006

AbstractAll data assimilation systems are affected by biases, caused by problems with the data, by approximations in the observation operators used to simulate the data, by limitations of the assimilating model, or by the assimilation methodology itself. A clear symptom of bias in the assimilation is the presence of systematic features in the analysis increments, such as large persistent mean values or regularly recurring spatial structures. Bias can also be detected by monitoring statistics of observed‐minus‐background residuals for different instruments. Bias‐aware assimilation methods are designed to estimate and correct systematic errors jointly with the model state variables. Such methods require attribution of a bias to a particular source, and its characterization in terms of some well‐defined set of parameters. They can be formulated either in a variational or sequential estimation framework by augmenting the system state with the bias parameters. Copyright © 2005 Royal Meteorological Society
Data assimilation for marine monitoring and prediction: The MERCATOR operational assimilation systems and the MERSEA developments
Authors: Brasseur P. , Bahurel P. , Bertino L. , Birol F. , Brankart J.‐M. , Ferry N. , Losa S. , Remy E. , Schröter J. , Skachko S. , Testut C.‐E. , Tranchant B. , Van Leeuwen P. J. , Verron J. 
Published: August 2006

AbstractDuring the past 15 years, a number of initiatives have been undertaken at national level to develop ocean forecasting systems operating at regional and/or global scales. The co‐ordination between these efforts has been organized internationally through the Global Ocean Data Assimilation Experiment (GODAE). The French MERCATOR project is one of the leading participants in GODAE. The MERCATOR systems routinely assimilate a variety of observations such as multi‐satellite altimeter data, sea‐surface temperature and in situ temperature and salinity profiles, focusing on high‐resolution scales of the ocean dynamics.The assimilation strategy in MERCATOR is based on a hierarchy of methods of increasing sophistication including optimal interpolation, Kalman filtering and variational methods, which are progressively deployed through the Système d'Assimilation MERCATOR (SAM) series. SAM‐1 is based on a reduced‐order optimal interpolation which can be operated using ‘altimetry‐only’ or ‘multi‐data’ set‐ups; it relies on the concept of separability, assuming that the correlations can be separated into a product of horizontal and vertical contributions. The second release, SAM‐2, is being developed to include new features from the singular evolutive extended Kalman (SEEK) filter, such as three‐dimensional, multivariate error modes and adaptivity schemes. The third one, SAM‐3, considers variational methods such as the incremental four‐dimensional variational algorithm.Most operational forecasting systems evaluated during GODAE are based on least‐squares statistical estimation assuming Gaussian errors. In the framework of the EU MERSEA (Marine EnviRonment and Security for the European Area) project, research is being conducted to prepare the next‐generation operational ocean monitoring and forecasting systems. The research effort will explore nonlinear assimilation formulations to overcome limitations of the current systems. This paper provides an overview of the developments conducted in MERSEA with the SEEK filter, the Ensemble Kalman filter and the sequential importance re‐sampling filter. Copyright © 2005 Royal Meteorological Society
The transformation of earth‐system observations into information of socio‐economic value in GEOSS
Authors: Hollingsworth Anthony , Uppala Sakari , Klinker Ernst , Burridge David , Vitart Frederic , Onvlee Jeanette , Vries J. W. De , Roo Ad De , Pfrang Christian 
Published: August 2006

AbstractThe Group on Earth Observations System of Systems, GEOSS, is a co‐ordinated initiative by many nations to address the needs for earth‐system information expressed by the 2002 World Summit on Sustainable Development. We discuss the role of earth‐system modelling and data assimilation in transforming earth‐system observations into the predictive and status‐assessment products required by GEOSS, across many areas of socio‐economic interest. First we review recent gains in the predictive skill of operational global earth‐system models, on time‐scales of days to several seasons. We then discuss recent work to develop from the global predictions a diverse set of end‐user applications which can meet GEOSS requirements for information of socio‐economic benefit; examples include forecasts of coastal storm surges, floods in large river basins, seasonal crop yield forecasts and seasonal lead‐time alerts for malaria epidemics. We note ongoing efforts to extend operational earth‐system modelling and assimilation capabilities to atmospheric composition, in support of improved services for air‐quality forecasts and for treaty assessment. We next sketch likely GEOSS observational requirements in the coming decades. In concluding, we reflect on the cost of earth observations relative to the modest cost of transforming the observations into information of socio‐economic value. Copyright © 2005 Royal Meteorological Society
Stochastic modelling of model errors: a simulation study
Authors: Tsyrulnikov M. D. 
Published: August 2006

AbstractIn the setting with known ‘truth’, the spatio‐temporal structure of forecast‐model (tendency) errors is studied. The shallow‐water model is used as the ‘truth’ and the vorticity equation as a forecast model. It is found that state‐dependent model errors (MEs) are of primary importance. The residual state‐independent (stochastic) part of MEs can be modelled with the advection‐diffusion equation driven by the white noise. The ME effective advection velocity appears to be very different from the wind and resembles the Rossby‐wave phase velocity. Three versions of increasing complexity for the advection and diffusion operators are proposed. Ensemble‐based adequacy checks of the proposed ME model are presented. Sensitivity of the ensemble forecast‐error spatial and temporal structure to various aspects of the ME model used to create the ensemble is investigated. Copyright © 2005 Royal Meteorological Society
Why does 4D‐Var beat 3D‐Var?
Authors: Lorenc Andrew C. , Rawlins F. 
Published: August 2006

AbstractA set of four experiments is described which measure the expected beneficial aspects of incremental four‐dimensional variational (4D‐Var) compared to 3D‐Var data assimilation systems: allowing for the time of each observation in the full and increment fields with which it is compared, and using time‐evolved covariances. Judging each scheme by the overall accuracy of resulting numerical weather prediction forecasts compared to observations, each aspect is shown to provide benefit.On other measures of analysis quality, such as the fit of short‐period forecasts and analyses to observations, the benefits of 4D‐Var are less clear; it is sometimes worse. Perhaps 4D‐Var is improving the analysis of growing modes, which are more important for forecasts, without improving all aspects of the analysis.Our basic 4D‐Var was not provided with many observations distributed in time, and had very simple parametrizations. There is an expectation of enhanced benefits as these aspects are developed. Copyright © 2005 Royal Meteorological Society
The impact of ensemble filter definition on the assimilation of temperature profiles in the tropical Pacific
Authors: Leeuwenburgh O. , Evensen G. , Bertino L. 
Published: August 2006

AbstractThe traditional analysis scheme in the Ensemble Kalman Filter (EnKF) uses a stochastic perturbation or randomization of the measurements which ensures a correct variance in the updated ensemble. An alternative so‐called deterministic analysis algorithm is based on a square‐root formulation where the perturbation of measurements is avoided. Experiments with simple models have indicated that ensemble collapse is likely to occur when deterministic filters are applied to nonlinear problems. In this paper the properties of stochastic and deterministic ensemble analysis algorithms are evaluated in an identical‐twin experiment using an ocean general‐circulation model. In particular, the implications of the use of deterministic Ensemble Square‐Root Filters (EnSRF) for ensemble distribution are investigated. An explanation is presented for the observed collapse, and a simple solution based on randomization of the analysis ensemble anomalies is examined. A one‐year assimilation run with this improved EnSRF is found to produce Gaussian distributions, similar to the EnKF. Copyright © 2005 Royal Meteorological Society
Ionospheric nowcasting via assimilation of GPS measurements of ionospheric electron content in a global physics‐based time‐dependent model
Authors: Khattatov B. , Murphy M. , Gnedin M. , Sheffel J. , Adams J. , Cruickshank B. , Yudin V. , Fuller‐rowell T. , Retterer J. 
Published: August 2006

AbstractWe present the rationale for having accurate nowcast and forecast ionospheric conditions, and a brief overview of recent work on assimilation of ionospheric measurements in physics‐based models. This manuscript describes the results of a project aimed at generating accurate operational specifications of ionospheric electron content by the assimilation of Global Positioning System (GPS) ionospheric measurements in a relatively complex first‐principles forecast model. We describe: the overall design of the model, the implemented sequential data assimilation scheme, the specifics of GPS data processing, and the on‐line scheme for estimation of instrumental biases inherent in GPS measurements of ionospheric electron content. Performance of the designed ionospheric specification system is illustrated via common statistical tests, comparisons with data withheld from the assimilation process and comparisons with independent non‐GPS measurements. Web‐based access to the system results is provided athttp://fusionnumerics.com/ionosphere. Copyright © 2005 Royal Meteorological Society
Observed and Unobserved Preference Heterogeneity in Brand-Choice Models
Authors: Horsky Dan , Misra Sanjog , Nelson Paul 
Published: August 2006

This paper extends the scanner-based choice literature by explicitly incorporating individual-level brand-preference data. We illustrate our model using a unique data set that combines survey and scanner data collected from the same individuals.The addition of individual-specific brand-preference information significantly improves fit and prediction. Furthermore, this “observed” heterogeneity better explains choice than does “unobserved” heterogeneity in the standard scanner model’s parameters. More importantly, we find that the standard model underestimates the importance of consumers’ brand preferences and overestimates both brand loyalties and price sensitivities. Brand loyalty is overestimated because models without preference information confound state dependence, heterogeneity, and preference effects. Price sensitivities are inflated because the “average” preference-based consumer is implicitly assumed to be more willing to switch from his preferred brand than is the “real” preference-based consumer. Further, standard models overestimate the heterogeneity in price and loyalty sensitivities and misidentify both price- and loyalty-sensitive consumers.The managerial implications of our findings and the applicability of our methodology when survey data are collected infrequently and for only a subsample of consumers are pursued. We demonstrate that even under these circumstances better populationwide pricing and promotion decisions are identified and more accurate targeting results.
The Development of a Suction Control System for a Triaxial Apparatus
Authors: Jotisankasa A , Coop M , Ridley A 
Published: August 2006

Abstract
A new method of controlling suction in the triaxial apparatus is presented that consists of two subsystems: one each for drying and wetting that is used in combination with an independent measurement of suction. The drying system is based on a development by Cunningham et al _2003_, with improvements in the measurement of the current water content. The wetting system involves the staged circulation of air and water. This new technique enables continuous monitoring of all state variables during tests, including water content, degree of saturation, net stresses, suction, and the different components of strain. Some typical results from tests on a compacted silty clay are presented in order to demonstrate the capabilities of the system. The main advantage of the apparatus is that there is no need to raise the ambient air pressure as is required with the axis translation technique and tests may therefore be conducted at negative pore water pressure. The system may also be easily incorporated into other standard apparatus.
The Effects of Load Soak Control on the Wear of UHMWPE at Various Hydration Levels in a Joint Simulation Study
Authors: Liao Y-S , Hanes M 
Published: August 2006

Abstract
The study was to investigate the effects of various hydration levels on the wear of ultra-high molecular weight polyethylene (UHMWPE) in a hip simulation testing, and to assess the effect of load soak control on the implant wear rates. Three types of polyethylene liners (28 mm ID) made from GUR 1050 UHMWPE bars were evaluated: noncrosslinked (XL0), gamma irradiated (thermally-treated) at nominal doses of 5 and 10 Mrads (XL5 and XL10, respectively). Three hydration processes were applied: (1) presoaked in water for four weeks, i.e., standard protocol; (2) exposed in air for four weeks; and (3) presoaked in water at 900 psi (approximately 60 atm) in a pressurized chamber for three weeks. Six groups of interest were selected and tested on a hip simulator with load soak control stations. The group that was subjected to 900 psi pressure gained 11.9 ± 0.4 mg of water after three weeks, which was about eight times the groups that presoaked in water. After the wear simulation started, the highly hydrated group lost almost 10 mg during the first 0.5-million cycle interval, which was due to the pumping motion of the load soak stations. All soak control liners achieved similar hydration levels after one million cycles of testing. The overall wear rating was inversely related to the amount of crosslinking. Without load soak correction, the initial wear rate of XL5 with pressurized soaking was twice the corrected wear; however, the wear rate remained similar after one million cycles with or without corrections.
Effect of Magnetic Field on Fatigue Crack Propagation of Single-Edge Cracked Soft Ferromagnetic Specimens under Mode I Loading
Authors: Shindo Y , Shindo I , Narita F 
Published: August 2006

Abstract
The purpose of this paper is to investigate the effect of magnetic field on the fatigue crack growth behavior of nickel iron soft ferromagnetic materials under Mode I loading. Fatigue crack growth tests were conducted using single-edge cracked tension specimens in a magnetic field, and the effects of magnetic field and loading condition on the crack growth rates were examined. Magnetic field effect on the stress intensity factor range also was discussed for a single-edge cracked soft ferromagnetic strip. The fracture surfaces were examined by scanning electron microscopy to correlate with fatigue characteristics.
Schur and Schubert polynomials as Thom polynomials—cohomology of moduli spaces
Authors: Fehér László , Rimányi Richárd 
Published: August 2006

Abstract
The theory of Schur and Schubert polynomials is revisited in this paper from the point of view of generalized Thom polynomials. When we apply a general method to compute Thom polynomials for this case we obtain a new definition for (double versions of) Schur and Schubert polynomials: they will be solutions of interpolation problems.
On subadditive functions and ψ-additive mappings
Authors: Matkowski Janusz 
Published: August 2006

Abstract
In [4], assuming among others subadditivity and submultiplicavity of a function ψ: [0, ∞)→[0, ∞), the authors proved a Hyers-Ulam type stability theorem for “ψ-additive” mappings of a normed space into a normed space. In this note we show that the assumed conditions of the function ψ imply that ψ=0 and, consequently, every “ψ-additive” mapping must be additive
Quantum scattering near the lowest Landau threshold for a Schrödinger operator with a constant magnetic field
Authors: Melgaard Michael 
Published: August 2006

Abstract
For fixed magnetic quantum number m results on spectral properties and scattering theory are given for the three-dimensional Schrödinger operator with a constant magnetic field and an axisymmetrical electric potential V. In various, mostly singular settings, asymptotic expansions for the resolvent of the Hamiltonian H
m+Hom+V are deduced as the spectral parameter tends to the lowest Landau threshold. Furthermore, scattering theory for the pair (H
m, H
om) is established and asymptotic expansions of the scattering matrix are derived as the energy parameter tends to the lowest Landau threshold.
The closure diagram for nilpotent orbits of the split real form of E8
Authors: Đoković Dragomir 
Published: August 2006

Abstract
Let
$$\mathcal{O}_1 $$
and
$$\mathcal{O}_2 $$
be adjoint nilpotent orbits in a real semisimple Lie algebra. Write
$$\mathcal{O}_1 $$
≥
$$\mathcal{O}_2 $$
if
$$\mathcal{O}_2 $$
is contained in the closure of
$$\mathcal{O}_1 $$
. This defines a partial order on the set of such orbits, known as the closure ordering. We determine this order for the split real form of the simple complex Lie algebra, E
8. The proof is based on the fact that the Kostant-Sekiguchi correspondence preserves the closure ordering. We also present a comprehensive list of simple representatives of these orbits, and list the irreeducible components of the boundaries
$$\partial \mathcal{O}_1^i $$
and of the intersections
$$\overline {\mathcal{O}_l^i } \cap \overline {\mathcal{O}_l^j } $$
.
On quasistatic inelastic models of gradient type with convex composite constitutive equations
Authors: Chełmiński Krzysztof 
Published: August 2006

Abstract
This article defines and presents the mathematical analysis of a new class of models from the theory of inelastic deformations of metals. This new class, containing so called convex composite models, enlarges the class containing monotone models of gradient type defined in [1]. This paper starts to establish the existence theory for models from this new class; we restrict our investigations to the coercive and linear self-controlling case.
Thermodynamic non-additivity in disordered systems with extended phase space
Authors: Vakarin Eduard , Badiali Jean 
Published: August 2006

AbstractNon-additivity effects in coupled dynamic-stochastic systems are investigated. It is shown that there is a mapping of the replica approach to disordered systems with finite replica indexn on Tsallis non-extensive statistics, if the average thermodynamic entropy of the dynamic subsystem differs from the information entropy for the probability distribution in the stochastic subsystem. The entropic indexq is determined by the entropy difference ΔS. In the case of incomplete information, the entropic indexq=1−n is shown to be related to the degree of lost information.
Phase- and helicity-dependent effects in three-color ionization
Authors: Fifirig Magda , Stroe Marius 
Published: August 2006

AbstractWe study the two-photon ionization of the hydrogen atom from its ground state by a three-color electromagnetic field consisting of a superposition of an IR laser and two of its consecutive odd harmonics of order 2p−1 and 2p+1, withp a positive integer and constant relative phase difference. The ionization process due to the net absorption of the energy 2pħω (ω being the IR laser frequency) is considered. The influence of phase difference and helicity on the azimuthal angular distribution of the ejected photoelectrons is illustrated in the case in which the two harmonics have identical polarizations. Phase effect on the alignment of the differential ionization rate is also investigated.