scholarly journals Data-based stochastic subgrid-scale parametrization: an approach using cluster-weighted modelling

2012 ◽  
Vol 370 (1962) ◽  
pp. 1061-1086 ◽  
Author(s):  
Frank Kwasniok
Keyword(s):  
Clustering Algorithm ◽  
Prediction Models ◽  
Statistical Modelling ◽  
Scale Model ◽  
Ensemble Prediction ◽  
Subgrid Scale ◽  
New Approach ◽  
Lorenz 96 ◽  
The Impact

A new approach for data-based stochastic parametrization of unresolved scales and processes in numerical weather and climate prediction models is introduced. The subgrid-scale model is conditional on the state of the resolved scales, consisting of a collection of local models. A clustering algorithm in the space of the resolved variables is combined with statistical modelling of the impact of the unresolved variables. The clusters and the parameters of the associated subgrid models are estimated simultaneously from data. The method is implemented and explored in the framework of the Lorenz '96 model using discrete Markov processes as local statistical models. Performance of the cluster-weighted Markov chain scheme is investigated for long-term simulations as well as ensemble prediction. It clearly outperforms simple parametrization schemes and compares favourably with another recently proposed subgrid modelling scheme also based on conditional Markov chains.

A state-of-the-art review on wind power deterministic prediction

2020 ◽  
pp. 0309524X2094120 ◽  
Author(s):  
Zhongda Tian
Keyword(s):  
Wind Power ◽  
Prediction Method ◽  
Scale Model ◽  
Ensemble Prediction ◽  
Prediction Methods ◽  
Power Prediction ◽  
Continuous Growth ◽  
Advantages And Disadvantages ◽  
Wind Power Prediction ◽  
The Impact

With the continuous growth of wind power access capacity, the impact of intermittent and volatile wind power generation on the grid is becoming more and more obvious, so the research of wind power prediction method has been widely concerned. Accurate wind power prediction can provide necessary support for the power grid dispatching, combined operation of generating units, operation, and maintenance of wind farms. According to the existing wind power prediction methods, the wind power prediction methods are systematically classified according to the time scale, model object, and model principle of prediction. The physical methods, statistical methods include single and ensemble prediction methods related to wind power prediction are introduced in detail. The error evaluation indicator of the prediction method is analyzed, and the advantages and disadvantages of each prediction method and its applicable occasions are given. At the same time, in view of the existing problems in the wind power prediction method, the corresponding improvement plan is put forward. Finally, this article points out that the research is needed for wind power prediction in the future.

scholarly journals Noise characteristic analysis and sound sources identification for rod–airfoil interaction using different subgrid-scale models

2021 ◽  
Vol 233 ◽  
pp. 04036
Author(s):  
Chenghao Yang ◽  
Heying Feng ◽  
Yehui Peng
Keyword(s):  
Energy Transport ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Scale Model ◽  
Subgrid Scale ◽  
Characteristic Analysis ◽  
Sound Sources ◽  
Eddy Simulation ◽  
Scale Models ◽  
The Impact

Four subgrid-scale models based on large eddy simulation (LES), such as Smagorinsky–Lilly (SL), dynamic Smagorinsky–Lilly (DSL), wall-adapting local eddy-viscosity (WALE), and dynamic kinetic-energy transport (KET) were used and couple Ffowcs Williams–Hawkings equation to accurately analyze and identify the characteristics and position of the sound sources of rod–airfoil interaction. The results of four models were compared with experimental data. It was found that the DSL model was the optimal subgrid-scale model for the study of the interaction noise considering the calculation accuracy. Therefore, the DSL model was selected for analyzing and identifying the characteristics and location of the interaction noise source. During the calculation, solid and permeable data surfaces were used for acoustic integral surfaces. The results show that the impact of the quadrupole source is negligible at a low Mach number, and the dipole noise coming from the pressure fluctuations is dominant. Meanwhile, the dipole noise from the airfoil is louder than that from the rod; the leading edge of about 30% chord length of airfoil the is the main sound source of interference effect. Above results can provide guidance for research of blade-vortex interaction noise.

scholarly journals Dependence of skill and spread of the ensemble forecasts on the type of perturbation and its relationship with long-term norms of precipitation and temperature

2020 ◽  
Vol 68 (5) ◽  
pp. 1505-1528
Author(s):  
Grzegorz Duniec ◽  
Andrzej Mazur
Keyword(s):  
Ensemble Methods ◽  
Soil Surface ◽  
Ensemble Prediction ◽  
Operational Mode ◽  
Ensemble Forecasts ◽  
Ensemble Prediction System ◽  
Computing Power ◽  
The Impact ◽  
Priority Project

Abstract A new computing cluster has been operating since 2016 at the Institute of Meteorology and Water Management – National Research Institute. Increasing computing power enabled the implementation of ensemble prediction system forecasts in the operational mode and the use of a new computer for research purposes. As part of the priority project on “Study of Disturbances in the Representation of Modeling Uncertainty in Ensemble Development” and the earlier project entitled “COSMO Towards Ensemble in Km in Our Countries), implemented in the Working Group 7 (Predictability and Ensemble Methods) as part of the COSMO modeling consortium, specific studies were carried out to test ensemble forecasts. This research concerned the impact of variability of physical fields characterizing the soil surface (a selected parameter determining evaporation from the soil surface and soil surface temperature) using various methods of perturbation. Numerical experiments were completed for the warm period (from June to September) 2013.

LES of Wall-Bounded Flows Using a New Subgrid Scale Model Based on Energy Spectrum Dissipation

2008 ◽  
Vol 75 (2) ◽  
Author(s):  
I. Veloudis ◽  
Z. Yang ◽  
J. J. McGuirk
Keyword(s):  
Energy Spectrum ◽  
Kinetic Energy ◽  
Transport Equation ◽  
Scale Effects ◽  
Energy Content ◽  
Scale Model ◽  
Length Scale ◽  
Subgrid Scale ◽  
New Approach ◽  
Accurate Representation

A new one-equation subgrid scale (SGS) model that makes use of the transport equation for the SGS kinetic energy (kSGS) to calculate a representative velocity scale for the SGS fluid motion is proposed. In the kSGS transport equation used, a novel approach is developed for the calculation of the rate of dissipation of the SGS kinetic energy (ε). This new approach leads to an analytical computation of ε via the assumption of a form for the energy spectrum. This introduces a more accurate representation of the dissipation term, which is then also used for the calculation of a representative length scale for the SGS based on their energy content. Therefore, the SG length scale is not associated simply with the grid resolution or the largest of the SGS but with a length scale representative of the overall SGS energy content. The formulation of the model is presented in detail, and the new approach is tested on a series of channel flow test cases with Reynolds number based on friction velocity varying from 180 to 1800. The model is compared with the Smagorinsky model (1963, “General Circulation Experiments With the Primitive Equations: 1. The Basic Experiment,” Mon. Weather Rev., 91, pp. 90–164) and the one-equation model of Yoshizawa and Horiuti (1985, “A Statistically-Derived Subgrid Scale Kinetic Energy Model for the Large Eddy Simulation of Turbulent Flows,” J. Phys. Soc. Jpn., 54(8), pp. 2834–2839). The results indicate that the proposed model can provide, on a given mesh, a more accurate representation of the SG scale effects.

SINGLE-MARKET REGULATION AND INNOVATION IN EUROPE'S MEDICAL DEVICES INDUSTRY

2001 ◽  
Vol 17 (3) ◽  
pp. 421-432 ◽  
Author(s):  
Horst Steg ◽  
Nikolaus Thumm
Keyword(s):  
Medical Devices ◽  
Regulatory Framework ◽  
European Market ◽  
Market Regulation ◽  
Short Term ◽  
New Approach ◽  
Single European Market ◽  
The Impact ◽  
Total Impact

In this article we analyze the influence of the legal regulatory framework in Europe, established by the two directives on medical devices and active implantable devices, on the performance of innovation in a single European market. First, we describe in general the possible influence of a single European market on innovation and the institutional features of the particular harmonization approach (“New Approach”) we are looking at here. The empirical results presented derive from a survey investigation involving 150 firms that we defined as best innovators in the European medical devices industry from a pre-survey. The results confirm that the total impact of the New Approach regulation on firms' innovation in the long term is positive. However, it also becomes clear that the impact of regulation on innovation is limited if the factors are looked at individually and that there is a clear difference regarding short-term effects. To improve the regulatory framework, several policy actions are recommended.

scholarly journals Portuguese two-lane highways: modelling crash frequencies for different temporal and spatial aggregation of crash data

Transport ◽  
2015 ◽  
Vol 33 (1) ◽  
pp. 92-103 ◽  
Author(s):  
Jocilene Otilia da Costa ◽  
Alice Prudêncio Jacques Maria ◽  
Paulo António Alves Pereira ◽  
Elisabete Fraga Freitas ◽  
Francisco Emanuel Cunha Soares
Keyword(s):  
Traffic Safety ◽  
Prediction Models ◽  
Road Traffic ◽  
Statistical Modelling ◽  
Original Data ◽  
Northern Region ◽  
Contributing Factors ◽  
Road Traffic Safety ◽  
Contributory Factors ◽  
The Impact

The identification of contributory factors to crash frequencies observed in different highway facilities can aid transportation and traffic management agencies to improve road traffic safety. In spite of the strategic importance of the national Portuguese road network, there are no recent studies concerned with either the identification of contributory factors to road crashes or Crash Prediction Models (CPMs) for this type of roadway. This study presents an initial contribution to this problem by focusing on the national roads NR-14, NR-101 and NR-206, which are located in Northern region of Portugal. They are two-lane single carriageway rural roads. This study analysed the crash frequencies, Average Annual Daily Traffic (AADT) and geometric characteristics of 88 two-lane road segments. The selected segments were 200-m-long and did not cross through urbanized areas. The fixed length of 200 meters corresponds to the road length used in Portugal to define a critical point. Data regarding the annual crash frequency and the AADT were available from 1999 to 2010. Due to the high number of zero-crash records in the initial database, the data were explored to identify the best statistical modelling approach to be adopted. The Generalized Estimating Equations (GEE) procedure was applied to 10 distinctive databases formed by grouping the original data in time and space. The results show that the different observations within each road segment present an exchangeable correlation structure type. This paper also analyses the impact of the sample size on the model’s capability of identifying the contributing factors to crash frequencies. The major contributing factors identified for the two-lane highways studied were the traffic volume (expressed in AADT), lane width, vertical sinuosity, and Density of Access Points (DAP). Acceptable CPM was identified for the highways considered, which estimated the total number of crashes for 400-m-long segments for a cumulative period of two years.

scholarly journals Strategic Analysis of the External and Internal Environment of Sport Tourism at the “Banja Vrućica” Spa

2017 ◽  
Vol 24 (4) ◽  
pp. 252-258 ◽  
Author(s):  
Zoran Milinković ◽  
Slobodan Simović ◽  
Adriana Ljubojević ◽  
Jelena Jovanović ◽  
Kristina Pantelić Babić
Keyword(s):  
Swot Analysis ◽  
Strategic Analysis ◽  
Sport Tourism ◽  
Local Economies ◽  
New Approach ◽  
Average Impact ◽  
Swot Matrix ◽  
The Impact

Abstract Introduction. Numerous international and local organisations and agencies have in the past 15 years dealt with various issues and problems related to tourism in Bosnia and Herzegovina. Often, they have accentuated the large potential for tourism development and improvement, particularly when it comes to spa tourism. Although all elements necessary for development (tradition, accommodation capacities, natural resources, and traffic connections) are present, the “Banja Vrućica” spa is still unable to respond to modern tourism market demands so that it can contribute to the economic growth and development in the national and local economies. The successful running of a tourist destination requires the formulation of long-term goals and decisions, reached through a process of strategic management. The aim of this article is to use strategic analysis as a means of identifying the possibilities of introducing new sport-recreational offers with a higher quality of service provision aligned with consumer needs, which would help the Vrućica spa to become more attractive and profitable. Material and methods. After selecting factors of the internal and external environment which influence sport tourism at the spa, the intensity of the impact of each factor was determined through the use of SWOT analysis. Then, by multiplying the average impact of strengths, weaknesses, opportunities, and threats matched in the SWOT Matrix, a polygon SWOT analysis of the strategy was carried out. Conclusion. Having analysed the “Banja Vrućica” spa’s environment and having quantified the results, we reached the conclusion that the best solution is to form and implement a WO strategy with regard to sport tourism at the spa, meaning a shift in strategy aimed at keeping the existing activities and structures and developing new products and a new approach to the market.

scholarly journals Simulation Possibilites of the Post-Mining Goafs Impact on the Deformations Induced by Next Underground Mining Operations with Use of the Cellular Automata Method

2020 ◽  
Author(s):  
Sikora Paweł
Keyword(s):  
Rock Mass ◽  
Underground Mining ◽  
Mining Area ◽  
Mining Operations ◽  
New Approach ◽  
Upper Silesian Coal Basin ◽  
Under Construction ◽  
The Impact ◽  
Further Development

Abstract Underground mining operations in the area of a rock mass affected by previous exploitation may cause additional deformations to appear on the surface. The size of these deformations can be significant, and their character is often non-linear. The nature of these deformations cannot be justified solely by the impact of current mining operations. At the same time, the predictive method of S. Knothe, widely used in Poland, does not explicitly include these types of phenomena. In the area of intensive and long-term mining exploitation, such as the Upper Silesian Coal Basin, the practical possibility of simulating this occurrence may be helpful in the planning of new mining exploitation under construction objects. Today we are usually limited to numerical modelling methods like finite difference method (FDM). This one base on the principle of mechanical similarity. The theoretical usefulness of method (and its similar) has already been proven many times. The main impediment to its practical application is the lack of recognition of the rock mass in terms of its mechanical properties. The presented method is a new approach to the possibility of modelling the subject phenomenon. The method has not been used in practical forecasting mining area deformation caused by underground deposits mining. It’s characterized by a huge potential for further development.

scholarly journals Stochastic Nature of Physical Parameterizations in Ensemble Prediction: A Stochastic Convection Approach

2008 ◽  
Vol 136 (2) ◽  
pp. 483-496 ◽  
Author(s):  
João Teixeira ◽  
Carolyn A. Reynolds
Keyword(s):  
Prediction Models ◽  
Ensemble Prediction ◽  
Initial Condition ◽  
Moist Convection ◽  
Subgrid Scale ◽  
Ensemble Spread ◽  
Simplified Algorithm ◽  
Prediction Systems ◽  
The Tropics ◽  
Physical Parameterizations

Abstract In this paper it is argued that ensemble prediction systems can be devised in such a way that physical parameterizations of subgrid-scale motions are utilized in a stochastic manner, rather than in a deterministic way as is typically done. This can be achieved within the context of current physical parameterization schemes in weather and climate prediction models. Parameterizations are typically used to predict the evolution of grid-mean quantities because of unresolved subgrid-scale processes. However, parameterizations can also provide estimates of higher moments that could be used to constrain the random determination of the future state of a certain variable. The general equations used to estimate the variance of a generic variable are briefly discussed, and a simplified algorithm for a stochastic moist convection parameterization is proposed as a preliminary attempt. Results from the implementation of this stochastic convection scheme in the Navy Operational Global Atmospheric Prediction System (NOGAPS) ensemble are presented. It is shown that this method is able to generate substantial tropical perturbations that grow and “migrate” to the midlatitudes as forecast time progresses while moving from the small scales where the perturbations are forced to the larger synoptic scales. This stochastic convection method is able to produce substantial ensemble spread in the Tropics when compared with results from ensembles created from initial-condition perturbations. Although smaller, there is still a sizeable impact of the stochastic convection method in terms of ensemble spread in the extratropics. Preliminary simulations with initial-condition and stochastic convection perturbations together in the same ensemble system show a promising increase in ensemble spread and a decrease in the number of outliers in the Tropics.

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