scholarly journals Design and Simulation of Measurement-Based Correlation Models for Shadow Fading

2011 ◽  
Vol 1 (2) ◽  
Author(s):  
Matthias Pätzold ◽  
Nurilla Avazov ◽  
Van Duc Nguyen
Keyword(s):  
Simulation Model ◽  
Real World ◽  
Communication Systems ◽  
Goodness Of Fit ◽  
Model Parameters ◽  
Shadow Fading ◽  
Correlation Model ◽  
Lp Norm ◽  
Correlation Models ◽  
Average Duration Of Fades

This paper deals with the design of measurement-based correlation models for shadow fading. Based on the correlation model, we design a simulation model using the sum-of-sinusoids (SOS) method to enable the simulation of spatial lognormal processes characterizing real-world shadow fading scenarios. The model parameters of the simulation model are computed by applying the Lp-norm method (LPNM). This method facilitates an excellent fitting of the simulation model’s autocorrelation function (ACF) to that of measured channels. Our study includes an evaluation of all important statistical quantities of the proposed measurement-based simulation model, such as the probability density function (PDF), spatial ACF, decorrelation and coherence distance, as well as the level-crossing rate (LCR) and the average duration of fades (ADF). A comparison with the Gudmundson correlation model shows that the developed measurement-based correlation model outperforms the former one by far in terms of the goodness of fit to the measured data. The proposed measurement-based simulation model allows to study the effects of long-term fading on the performance of mobile communication systems under real-world shadow fading conditions.

scholarly journals An Improved Iterative Nonlinear Least Square Approximation Method for the Design of SISO Wideband Mobile Radio Channel Simulators

2012 ◽  
Vol 2 (1-2) ◽  
Author(s):  
Akmal Fayziyev ◽  
Matthias Pätzold
Keyword(s):  
Simulation Model ◽  
Communication Systems ◽  
Goodness Of Fit ◽  
Radio Channel ◽  
Least Square ◽  
Model Parameters ◽  
Frobenius Norm ◽  
Single Input Single Output ◽  
Time Frequency ◽  
Wideband Channel

In this paper, we present an improved version of the iterative nonlinear least square approximation (INLSA) method for designing measurement-based single-input single-output (SISO) wideband channel simulators. The proposed method aims to fit the time-frequency correlation function (TFCF) of the simulation model to that of a measured channel. The parameters of the simulation model are determined iteratively by minimizing the Frobenius norm, which serves as a measure for the fitting error. In contrast to the original INLSA method, the proposed approach provides a unique optimized set of model parameters, which guarantees a quasi-perfect fitting with respect to the TFCF. We analyze the performance of the proposed method in terms of the goodness of fit to the measured data. The investigations will be carried out with respect to the TFCF and the scattering function. We demonstrate that the proposed approach is a powerful tool for the design of measurement-based wideband channel simulators, which are important for the performance evaluation of mobile communication systems under real-world propagation conditions.

scholarly journals Parameter Optimization for Real-World ENSO Forecast in an Intermediate Coupled Model

2019 ◽  
Vol 147 (5) ◽  
pp. 1429-1445 ◽  
Author(s):  
Yuchu Zhao ◽  
Zhengyu Liu ◽  
Fei Zheng ◽  
Yishuai Jin
Keyword(s):  
Data Assimilation ◽  
Parameter Optimization ◽  
Real World ◽  
Climate Models ◽  
Coupled Model ◽  
Prediction Skill ◽  
Model Parameters ◽  
Real World Data ◽  
The Real ◽  
Advection Term

Abstract We performed parameter estimation in the Zebiak–Cane model for the real-world scenario using the approach of ensemble Kalman filter (EnKF) data assimilation and the observational data of sea surface temperature and wind stress analyses. With real-world data assimilation in the coupled model, our study shows that model parameters converge toward stable values. Furthermore, the new parameters improve the real-world ENSO prediction skill, with the skill improved most by the parameter of the highest climate sensitivity (gam2), which controls the strength of anomalous upwelling advection term in the SST equation. The improved prediction skill is found to be contributed mainly by the improvement in the model dynamics, and second by the improvement in the initial field. Finally, geographic-dependent parameter optimization further improves the prediction skill across all the regions. Our study suggests that parameter optimization using ensemble data assimilation may provide an effective strategy to improve climate models and their real-world climate predictions in the future.

scholarly journals Formulating the history matching problem with consistent error statistics

2021 ◽  
Author(s):  
Geir Evensen
Keyword(s):  
Simulation Model ◽  
Measurement Errors ◽  
History Matching ◽  
Critical Role ◽  
Bayes Theorem ◽  
Conditional Probability Density ◽  
Model Parameters ◽  
Rate Data ◽  
Matching Problem ◽  
Reservoir Prediction

AbstractIt is common to formulate the history-matching problem using Bayes’ theorem. From Bayes’, the conditional probability density function (pdf) of the uncertain model parameters is proportional to the prior pdf of the model parameters, multiplied by the likelihood of the measurements. The static model parameters are random variables characterizing the reservoir model while the observations include, e.g., historical rates of oil, gas, and water produced from the wells. The reservoir prediction model is assumed perfect, and there are no errors besides those in the static parameters. However, this formulation is flawed. The historical rate data only approximately represent the real production of the reservoir and contain errors. History-matching methods usually take these errors into account in the conditioning but neglect them when forcing the simulation model by the observed rates during the historical integration. Thus, the model prediction depends on some of the same data used in the conditioning. The paper presents a formulation of Bayes’ theorem that considers the data dependency of the simulation model. In the new formulation, one must update both the poorly known model parameters and the rate-data errors. The result is an improved posterior ensemble of prediction models that better cover the observations with more substantial and realistic uncertainty. The implementation accounts correctly for correlated measurement errors and demonstrates the critical role of these correlations in reducing the update’s magnitude. The paper also shows the consistency of the subspace inversion scheme by Evensen (Ocean Dyn. 54, 539–560 2004) in the case with correlated measurement errors and demonstrates its accuracy when using a “larger” ensemble of perturbations to represent the measurement error covariance matrix.

FE-basierte Analyse*/FE-based analysis of the influence of remachining on component characteristics adjusted by forming processes

2018 ◽  
Vol 108 (01-02) ◽  
pp. 41-46
Author(s):  
F. Vogel ◽  
M. Tiffe ◽  
M. Metzger ◽  
D. Prof. Biermann
Keyword(s):  
Simulation Model ◽  
Fe Analysis ◽  
Experimental Investigations ◽  
Model Parameters ◽  
Sequential Process ◽  
Process Chain ◽  
Innovative Material

Bei der Auslegung verknüpfter Prozessschritte zur Herstellung von Bauteilen mit gezielt eingestellten Eigenschaften finden vermehrt FE-basierte Simulationssysteme Anwendung, um den Aufwand experimenteller Untersuchungen insbesondere im Hinblick auf den gesteigerten Einsatz innovativer Werkstoffkonzepte gering zu halten. Im Folgenden wird die Ausarbeitung von Konzepten zur Anpassung von Parametern zur Materialmodellierung sowie zur Verknüpfung von Einzelsimulationen der Prozesskette erläutert.   Regarding the increased application of innovative material concepts in sequential process steps for manufacturing components with tailored properties, the FE-analysis can be used to reduce the effort of experimental investigations. In this article, the development of concepts for the adjustment of simulation model parameters and the conjunction of process chain single simulations are described.

APPLICATION OF A MULTIDIMENSIONAL DETERMINISTIC-STATISTICAL NUMERICAL CORRELATION MODEL TO REFINE THE STRUCTURE OF THE AS11 HORIZON OF THE ZAPADNO-KAMYNSKOYE FIELD

2021 ◽  
Vol 7 (3) ◽  
pp. 123-135
Author(s):  
Anatoly M. NIKASHKIN ◽  
Alexey A. KLIMOV
Keyword(s):  
Oil And Gas ◽  
Geological Structure ◽  
Correlation Model ◽  
Gas Reservoirs ◽  
Work Related ◽  
Correlation Models ◽  
Complex Geological Structure ◽  
Geophysical Information ◽  
Well Correlation ◽  
Clay Layers

One of the primary and significant tasks in the construction of geological models of oil and gas reservoirs and development facilities is the problem of correlation of productive layers. This task, as a rule, is reduced to the identification and areal tracing of presumably even-aged oil and gas strata, horizons, and layers characterized by clear boundaries between sand strata and clay layers overlapping them. The practice of work related to modeling the structure of oil and gas horizons, layers and strata indicates that the correlation is not always unambiguous. The ambiguity is especially noticeable when correlating strata characterized by a clinoform structure, one of the examples is the Achimov strata. The most reliable basis for well correlation is GIS materials and lithological features of the interlayers forming individual layers. Clay interlayers and clay strata separating productive deposits provide valuable information when choosing a correlation model in sedimentary sections. These interlayers are characterized by the greatest consistency in area and are most clearly displayed on geophysical diagrams by the nature of the drawings of GIS curves. However, even in this case, i. e. when using the entire accumulated volume of the most diverse lithological and field-geophysical information, the correlation models of the sections turn out to be different and often even opposite. In this paper, the authors had to face a similar situation when correlating the horizon AS11 of the Zapadno-Kamynskoye field. The paper describes a method for clarifying the position of the chops of the productive horizon of oil and gas deposits using a multidimensional deterministic-statistical numerical model of the correlation of sedimentary strata. The proposed approach allows us to uniquely determine the positions of the chops in the conditions of a complex geological structure of the object, high thin-layered heterogeneity. A concrete example shows the advantages of the proposed approach in comparison with the traditional one.

Simulation of calcium homeostasis: modeling and parameter estimation

1983 ◽  
Vol 245 (5) ◽  
pp. R664-R672 ◽  
Author(s):  
S. Hurwitz ◽  
S. Fishman ◽  
A. Bar ◽  
M. Pines ◽  
G. Riesenfeld ◽  
...  
Keyword(s):  
Simulation Model ◽  
Plasma Calcium ◽  
Model Parameters ◽  
Estimation Of Parameters ◽  
Designed Experiments ◽  
Calcium Loading ◽  
Infusion Experiment ◽  
Dose Model ◽  
Edta Infusion

The system that regulates plasma calcium in the bird has been formalized into a model based on a series of differential equations and solved by computer simulation. Bone, kidney, and intestine have been considered as the control subsystems, with parathyroid hormone and 1,25-dihydroxycholecalciferol as the regulating hormones. The parameters used in the simulation model have been computed either from published results or by specifically designed experiments described here. For the estimation of parameters, an iterative procedure has been developed that was designed to minimize the sum of square errors between observed and system-simulated values. Parameters of 1,25-dihydroxycholecalciferol metabolism were experimentally obtained from the kinetic behavior of the 3H-labeled hormone in rachitic birds after a single dose. Model parameters have been adjusted using the results of in vivo calcium loading and validated by an EDTA infusion experiment. The simulation model has been used to study the hierarchy of the activities of the three control subsystems and of the regulating hormones, at different calcium intakes. Positive or negative errors in plasma calcium resulted in an asymmetry in the activities of the controlling systems, bone and kidney, whereas the intestine is characterized by its relatively long response time.

scholarly journals Evaluating performances of simplified physically based models for landslide susceptibility

2015 ◽  
Vol 12 (12) ◽  
pp. 13217-13256 ◽  
Author(s):  
G. Formetta ◽  
G. Capparelli ◽  
P. Versace
Keyword(s):  
Landslide Susceptibility ◽  
Goodness Of Fit ◽  
Shallow Landslides ◽  
Model Parameters ◽  
Test Case ◽  
Susceptibility Analysis ◽  
Physically Based ◽  
Private And Public ◽  
Physically Based Models

Abstract. Rainfall induced shallow landslides cause loss of life and significant damages involving private and public properties, transportation system, etc. Prediction of shallow landslides susceptible locations is a complex task that involves many disciplines: hydrology, geotechnical science, geomorphology, and statistics. Usually to accomplish this task two main approaches are used: statistical or physically based model. Reliable models' applications involve: automatic parameters calibration, objective quantification of the quality of susceptibility maps, model sensitivity analysis. This paper presents a methodology to systemically and objectively calibrate, verify and compare different models and different models performances indicators in order to individuate and eventually select the models whose behaviors are more reliable for a certain case study. The procedure was implemented in package of models for landslide susceptibility analysis and integrated in the NewAge-JGrass hydrological model. The package includes three simplified physically based models for landslides susceptibility analysis (M1, M2, and M3) and a component for models verifications. It computes eight goodness of fit indices by comparing pixel-by-pixel model results and measurements data. Moreover, the package integration in NewAge-JGrass allows the use of other components such as geographic information system tools to manage inputs-output processes, and automatic calibration algorithms to estimate model parameters. The system was applied for a case study in Calabria (Italy) along the Salerno-Reggio Calabria highway, between Cosenza and Altilia municipality. The analysis provided that among all the optimized indices and all the three models, the optimization of the index distance to perfect classification in the receiver operating characteristic plane (D2PC) coupled with model M3 is the best modeling solution for our test case.

scholarly journals Estimation of baseflow parameters of variable infiltration capacity model with soil and topography properties for predictions in ungauged basins

2011 ◽  
Vol 8 (4) ◽  
pp. 7017-7053 ◽  
Author(s):  
Z. Bao ◽  
J. Liu ◽  
J. Zhang ◽  
G. Fu ◽  
G. Wang ◽  
...  
Keyword(s):  
Goodness Of Fit ◽  
Model Simulation ◽  
Parameters Estimation ◽  
Model Parameters ◽  
Ungauged Basins ◽  
Variable Infiltration Capacity ◽  
Infiltration Capacity ◽  
Ungauged Catchments ◽  
Vic Model ◽  
Predictions In Ungauged Basins

Abstract. Equifinality is unavoidable when transferring model parameters from gauged catchments to ungauged catchments for predictions in ungauged basins (PUB). A framework for estimating the three baseflow parameters of variable infiltration capacity (VIC) model, directly with soil and topography properties is presented. When the new parameters setting methodology is used, the number of parameters needing to be calibrated is reduced from six to three, that leads to a decrease of equifinality and uncertainty. This is validated by Monte Carlo simulations in 24 hydro-climatic catchments in China. Using the new parameters estimation approach, model parameters become more sensitive and the extent of parameters space will be smaller when a threshold of goodness-of-fit is given. That means the parameters uncertainty is reduced with the new parameters setting methodology. In addition, the uncertainty of model simulation is estimated by the generalised likelihood uncertainty estimation (GLUE) methodology. The results indicate that the uncertainty of streamflow simulations, i.e., confidence interval, is lower with the new parameters estimation methodology compared to that used by original calibration methodology. The new baseflow parameters estimation framework could be applied in VIC model and other appropriate models for PUB.

scholarly journals Analytical and Numerical Connections between Fractional Fickian and Intravoxel Incoherent Motion Models of Diffusion MRI

Mathematics ◽  
2021 ◽  
Vol 9 (16) ◽  
pp. 1963
Author(s):  
Jingting Yao ◽  
Muhammad Ali Raza Anjum ◽  
Anshuman Swain ◽  
David A. Reiter
Keyword(s):  
Skeletal Muscle ◽  
Goodness Of Fit ◽  
Numerical Models ◽  
Tissue Perfusion ◽  
Parametric Models ◽  
Intravoxel Incoherent Motion ◽  
Fickian Diffusion ◽  
Model Parameters ◽  
Mathematical Framework ◽  
Stretched Exponential

Impaired tissue perfusion underlies many chronic disease states and aging. Diffusion-weighted imaging (DWI) is a noninvasive MRI technique that has been widely used to characterize tissue perfusion. Parametric models based on DWI measurements can characterize microvascular perfusion modulated by functional and microstructural alterations in the skeletal muscle. The intravoxel incoherent motion (IVIM) model uses a biexponential form to quantify the incoherent motion of water molecules in the microvasculature at low b-values of DWI measurements. The fractional Fickian diffusion (FFD) model is a parsimonious representation of anomalous superdiffusion that uses the stretched exponential form and can be used to quantify the microvascular volume of skeletal muscle. Both models are established measures of perfusion based on DWI, and the prognostic value of model parameters for identifying pathophysiological processes has been studied. Although the mathematical properties of individual models have been previously reported, quantitative connections between IVIM and FFD models have not been examined. This work provides a mathematical framework for obtaining a direct, one-way transformation of the parameters of the stretched exponential model to those of the biexponential model. Numerical simulations are implemented, and the results corroborate analytical results. Additionally, analysis of in vivo DWI measurements in skeletal muscle using both biexponential and stretched exponential models is shown and compared with analytical and numerical models. These results demonstrate the difficulty of model selection based on goodness of fit to experimental data. This analysis provides a framework for better interpreting and harmonizing perfusion parameters from experimental results using these two different models.

scholarly journals Flight crew diagnostic using aviation simulator training data

2016 ◽  
Vol 9 (3) ◽  
pp. 118-137
Author(s):  
L.S. Kuravsky ◽  
P.A. Marmalyuk ◽  
G.A. Yuryev ◽  
O.B. Belyaeva ◽  
O.Yu. Prokopieva
Keyword(s):  
Continuous Time ◽  
Goodness Of Fit ◽  
Training Data ◽  
Simulator Training ◽  
Model Parameters ◽  
Flight Crew ◽  
Advantages And Disadvantages ◽  
Goodness Of Fit Tests ◽  
Flight Simulators ◽  
Discrete States

This paper describes a new concept of flight crew assessment based on flight simulators training result. It is based on representation of pilot gaze movement with the aid of continuous-time Markov processes with discrete states. Considered are both the procedure of model parameters identification provided with goodness-of-fit tests in use and the classifier-building technique, which makes it possible to estimate degree of correspondence between the observed gaze motion distribution under study and reference distributions identified for different diagnosed groups. The final assessing criterion is formed on the basis of integrated diagnostic parameters, which are determined by the parameters of the identified models. The article provides a description of the experiment, illustrations, and results of studies aimed at assessing the reliability of the developed models and criteria, as well as conclusions about the applicability of the approach, its advantages and disadvantages.

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