A sequential method for selecting parameter values in the Barcelona basic model

2010 ◽  
Vol 47 (11) ◽  
pp. 1175-1186 ◽  
Author(s):  
Domenico Gallipoli ◽  
Francesca D’Onza ◽  
Simon J. Wheeler
Keyword(s):  
Laboratory Tests ◽  
Degrees Of Freedom ◽  
Sequential Method ◽  
Multiple Parameters ◽  
Basic Model ◽  
Specific Order ◽  
Iterative Procedures ◽  
Key Aspects ◽  
Soil Behaviour ◽  
Parameter Values

The popularity of the Barcelona basic model (BBM) has grown steadily since its publication in 1990, due to its ability to capture key aspects of unsaturated soil behaviour. Nevertheless, the BBM is still rarely employed by practitioners, partly because of the absence of simple and objective methods for selecting parameter values from laboratory tests. One difficulty is that, in the BBM, individual aspects of the isotropic virgin behaviour are controlled by multiple parameters, while at the same time a single parameter controls more than one aspect of soil behaviour. This has led to iterative procedures where parameter values are adjusted in turn to match experiments, which requires significant experience and can lead to the selection of widely varying parameter values depending on the user. The proposed method streamlines parameter selection with a view to increasing the appeal of the BBM for practitioners. The method adopts a “sequential” procedure where the five parameters governing isotropic virgin behaviour are matched to degrees of freedom in the BBM, which are then fixed one at a time, in a specific order, without any assumption about other parameters. The simplicity and reduced subjectivity of the method in comparison with iterative procedures is demonstrated by selecting parameter values from laboratory tests.

Effect of a Planetary Gearbox on the Dynamics of a Rotor System

2018 ◽  
Author(s):  
Ali Tatar ◽  
Christoph W. Schwingshackl
Keyword(s):  
Degrees Of Freedom ◽  
Dynamic Behaviour ◽  
Rotor System ◽  
Mode Shapes ◽  
Rotating System ◽  
Planetary Gearbox ◽  
Finite Element Software ◽  
Gyroscopic Effects ◽  
The Masses ◽  
Parameter Values

The dynamic analysis of rotors with bladed disks has been investigated in detail over many decades and is reasonably well understood today. In contrast, the dynamic behaviour of two rotors that are coupled via a planetary gearbox is much less well understood. The planetary gearbox adds inertia, mass, stiffness, damping and gyroscopic moments to the system and can strongly affect the modal properties and the dynamic behaviour of the global rotating system. The main objective of this paper is to create a six degrees of freedom numerical model of a rotor system with a planetary gearbox and to investigate its effect on the coupled rotor system. The analysis is based on the newly developed finite element software “GEAROT” which provides axial, torsional and lateral deflections of the two shafts at different speeds via Timoshenko beam elements and also takes gyroscopic effects into account. The disks are currently considered as rigid and the bearings are modelled with isotropic stiffness elements in the translational and rotational directions. A novel planetary gearbox model has been developed, which takes the translational and rotational stiffness and the damping of the gearbox, as well as the masses and inertias of the sun gear, ring gear, planet gears and carrier into account. A rotating system with a planetary gearbox has been investigated with GEAROT. The gearbox mass and stiffness parameters are identified as having a significant effect on the modal behaviour of the rotor system, affecting its natural frequencies and mode shapes. The higher frequency modes are found to be more sensitive to the parameter changes as well as the modes which have a higher deflection at the location of the gearbox on the rotor system. Compared with a single shaft system, the presence of a gearbox introduces new global modes to the rotor system and decouples the mode shapes of the two shafts. The introduction of a planetary gearbox may also lead to an increase or a reduction of the frequency response of the rotor system based on gear parameter values.

scholarly journals A New Approach to Newton-Type Polynomial Interpolation with Parameters

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Le Zou ◽  
Liangtu Song ◽  
Xiaofeng Wang ◽  
Thomas Weise ◽  
Yanping Chen ◽  
...  
Keyword(s):  
Polynomial Interpolation ◽  
Information Matrix ◽  
Divided Differences ◽  
Mathematical Representation ◽  
Interpolation Algorithm ◽  
New Approach ◽  
Multiple Parameters ◽  
Parameter Values ◽  
The Given ◽  
Interpolation Functions

Newton’s interpolation is a classical polynomial interpolation approach and plays a significant role in numerical analysis and image processing. The interpolation function of most classical approaches is unique to the given data. In this paper, univariate and bivariate parameterized Newton-type polynomial interpolation methods are introduced. In order to express the divided differences tables neatly, the multiplicity of the points can be adjusted by introducing new parameters. Our new polynomial interpolation can be constructed only based on divided differences with one or multiple parameters which satisfy the interpolation conditions. We discuss the interpolation algorithm, theorem, dual interpolation, and information matrix algorithm. Since the proposed novel interpolation functions are parametric, they are not unique to the interpolation data. Therefore, its value in the interpolant region can be adjusted under unaltered interpolant data through the parameter values. Our parameterized Newton-type polynomial interpolating functions have a simple and explicit mathematical representation, and the proposed algorithms are simple and easy to calculate. Various numerical examples are given to demonstrate the efficiency of our method.

scholarly journals Gravitational theory of cosmology, galaxies and galaxy clusters

2020 ◽  
Vol 80 (10) ◽  
Author(s):  
J. W. Moffat
Keyword(s):  
Power Spectrum ◽  
Galaxy Clusters ◽  
Degrees Of Freedom ◽  
Galaxy Cluster ◽  
Gravitational Theory ◽  
Baryon Density ◽  
Late Time ◽  
Matter Power Spectrum ◽  
The Galaxy ◽  
Parameter Values

AbstractA modified gravitational theory explains early universe and late time cosmology, galaxy and galaxy cluster dynamics. The modified gravity (MOG) theory extends general relativity (GR) by three extra degrees of freedom: a scalar field G, enhancing the strength of the Newtonian gravitational constant $$G_N$$ G N , a gravitational, spin 1 vector graviton field $$\phi _\mu $$ ϕ μ , and the effective mass $$\mu $$ μ of the ultralight spin 1 graviton. For $$t < t_\mathrm{rec}$$ t < t rec , where $$t_\mathrm{rec}$$ t rec denotes the time of recombination and re-ionization, the density of the vector graviton $$\rho _\phi > \rho _b$$ ρ ϕ > ρ b , where $$\rho _b$$ ρ b is the density of baryons, while for $$t > t_\mathrm{rec}$$ t > t rec we have $$\rho _b > \rho _\phi $$ ρ b > ρ ϕ . The matter density is parameterized by $$\Omega _M=\Omega _b+\Omega _\phi +\Omega _r$$ Ω M = Ω b + Ω ϕ + Ω r where $$\Omega _r=\Omega _\gamma +\Omega _\nu $$ Ω r = Ω γ + Ω ν . For the cosmological parameter values obtained by the Planck Collaboration, the CMB acoustical oscillation power spectrum, polarization and lensing data can be fitted as in the $$\Lambda $$ Λ CDM model. When the baryon density $$\rho _b$$ ρ b dominates the late time universe, MOG explains galaxy rotation curves, the dynamics of galaxy clusters, galaxy lensing and the galaxy clusters matter power spectrum without dominant dark matter.

scholarly journals Comparison of different algorithms for simultaneous estimation of multiple parameters in kinetic metabolic models

2010 ◽  
Vol 7 (3) ◽  
Author(s):  
Syed Murtuza Baker ◽  
Kai Schallau ◽  
Björn H. Junker
Keyword(s):  
Parameter Estimation ◽  
Computational Models ◽  
Optimization Methods ◽  
Optimization Techniques ◽  
Simultaneous Estimation ◽  
Multiple Parameters ◽  
Reliable Parameter ◽  
Metabolic Models ◽  
Parameter Values

SummaryComputational models in systems biology are usually characterized by a lack of reliable parameter values. This is especially true for kinetic metabolic models. Experimental data can be used to estimate these missing parameters. Different optimization techniques have been explored to solve this challenging task but none has proved to be superior to the other. In this paper we review the problem of parameter estimation in kinetic models. We focus on the suitability of four commonly used optimization techniques of parameter estimation in biochemical pathways and make a comparison between those methods. The suitability of each technique is evaluated based on the ability of converging to a solution within a reasonable amount of time. As most local optimization methods fail to arrive at a satisfactory solution we only considered the global optimization techniques. A case study of the upper part of Glycolysis consisting 15 parameters is taken as the benchmark model for evaluating these methods.

Simulations of a logistic-type model with delays for Chagas disease with insecticide spraying

2017 ◽  
Vol 10 (03) ◽  
pp. 1750033 ◽  
Author(s):  
Nofe Al-Asuoad ◽  
Tyler Pleasant ◽  
Meir Shillor ◽  
Hrishikesh Munugala ◽  
Daniel J. Coffield ◽  
...  
Keyword(s):  
Chagas Disease ◽  
Rural Areas ◽  
Type Model ◽  
Time Lags ◽  
Disease Dynamics ◽  
Vector Equation ◽  
Basic Model ◽  
Two Delays ◽  
Delay Differential ◽  
Parameter Values

This work studies and numerically simulates a logistic-type model for the dynamics of Chagas disease, which is caused by the parasite T. cruzi and affects millions of humans and domestic mammals throughout rural areas in Central and South America. A basic model for the disease dynamics that includes insecticide spraying was developed in Spagnuolo et al. (2010) [27] and consists of a delay-differential equation for the vectors and three nonlinear ordinary differential equations for the populations of the infected vectors, infected humans and infected domestic mammals. In this work, the vector equation is modified by using a logistic term with zero, one or two delays or time lags. The aim of this study is three-fold: to numerically study the effects of using different numbers of delays on the model behavior; to find if twice yearly insecticide spraying schedules improve vector control; and to study the sensitivity of the system to the delays in the case of two delays, by introducing randomness in the delays. It is found that the vector equation with different number of delays has very different solutions. The “best” day of spraying is the middle of Spring and twice annual sprayings cause only minor improvements in disease control. Finally, the model is found to be insensitive to the values of the delays, when the delays are randomly distributed within rather narrow intervals or ranges centered on the parameter values used in Coffield et al. (2014) [8].

scholarly journals Practical Challenges and Methodological Flexibility in Prior Elicitation

2019 ◽  
Author(s):  
Angelika Stefan ◽  
Nathan J. Evans ◽  
Eric-Jan Wagenmakers
Keyword(s):  
Degrees Of Freedom ◽  
Expert Knowledge ◽  
Bayesian Analyses ◽  
Prior Distributions ◽  
Prior Elicitation ◽  
Statistical Framework ◽  
Elicitation Process ◽  
Parameter Values ◽  
Structured Approach ◽  
Decision Paths

The Bayesian statistical framework requires the specification of prior distributions, which reflect pre-data knowledge about the relative plausibility of different parameter values. As prior distributions influence the results of Bayesian analyses, it is important to specify them with care. Prior elicitation has frequently been proposed as a principled method for deriving prior distributions based on expert knowledge. Although prior elicitation provides a theoretically satisfactory method of specifying prior distributions, there are several implicit decisions that researchers need to make at different stages of the elicitation process, each of them constituting important researcher degrees of freedom. Here, we discuss some of these decisions and group them into three categories: decisions about (1) the setup of the prior elicitation; (2) the core elicitation process; and (3) combination of elicited prior distributions from different experts. Importantly, different decision paths could result in greatly varying priors elicited from the same experts. Hence, researchers who wish to perform prior elicitation are advised to carefully consider each of the practical decisions before, during, and after the elicitation process. By explicitly outlining the consequences of these practical decisions, we hope to raise awareness for methodological flexibility in prior elicitation and provide researchers with a more structured approach to navigate the decision paths in prior elicitation. Making the decisions explicit also provides the foundation for further research that can identify evidence-based best practices that may eventually reduce the methodologically flexibility in prior elicitation.

Steep channel freezeup processes: understanding complexity with statistical and physical models

2015 ◽  
Vol 42 (9) ◽  
pp. 622-633 ◽  
Author(s):  
Mathieu Dubé ◽  
Benoit Turcotte ◽  
Brian Morse
Keyword(s):  
Degrees Of Freedom ◽  
Heat Budget ◽  
Morphological Characteristics ◽  
Large Data ◽  
Quantitative Information ◽  
Single Step ◽  
Physical Models ◽  
Data Set ◽  
Multiple Parameters ◽  
Physically Based

The development of ice dams in steep channels dictates water level variations and influences flow rates and habitat conditions. Despite the dominance of ice dam development in cold region gravel bed channels, practicing engineers and scientists have access to very little quantitative information describing this complex freezeup process. This paper aims to fill this gap by presenting a large data set on the process. The substantial variations observed in formation and melting rates from one site to the next and from one year to the next at the same site are explained with a physically-based numerical model that includes a complete heat budget applied to single step-pool sequence. The model successfully simulates the entire development of an ice dam and shows that the process depends on multiple parameters, or degrees of freedom. It also reveals that morphological characteristics greatly influence ice dam dynamics.

Ergonomic Level Improving of Armoured Fighting Vehicle Crew

2017 ◽  
Vol 68 (1) ◽  
pp. 33
Author(s):  
N. V. Ramamurthy ◽  
B. K. Vinayagam ◽  
Roopchand J.
Keyword(s):  
Degrees Of Freedom ◽  
Ride Comfort ◽  
Equations Of Motion ◽  
Research Work ◽  
Composite Model ◽  
Seat Suspension ◽  
Lumped Parameter ◽  
Vibration Responses ◽  
Suspension Model ◽  
Parameter Values

<p class="p1">The armoured fighting vehicle (AFV)-occupant composite system is modelled as a lumped parameter system, in this paper, wherein the 4 degrees of freedom (dof) biodynamic occupant model is integrated with 10 dof in-plane AFV model including the crew seat, thus leading to the 14 dof vehicle-occupant composite model and the governing equations of motion are obtained. The composite model is subjected to idealised road input simulating the ground reaction forces. Natural frequencies and the frequency domain vibration responses of various masses of model are obtained. The natural frequency of chassis thus obtained is compared with the result established by an earlier research work, to validate the model. The study is focused on crew seat location. A 2 dof occupant-seat suspension model is formulated and validated through case study. The optimised values of seat suspension parameters for ride comfort are obtained using the said model, through two methods of Invariant points theory and genetic algorithm toolbox of Matlab 2014a software. Acceleration responses of body for the current and optimised parameter values obtained illustrate that comfort of crew is improved with optimised values through minimization in the acceleration responses.</p>

scholarly journals ANALYSIS OF THE LOW-ENERGY π-p CHARGE-EXCHANGE DATA

2013 ◽  
Vol 28 (12) ◽  
pp. 1350039 ◽  
Author(s):  
E. MATSINOS ◽  
G. RASCHE
Keyword(s):  
Charge Exchange ◽  
Degrees Of Freedom ◽  
Scattering Amplitude ◽  
Heavy Baryon ◽  
Phase Shifts ◽  
Low Energy ◽  
Nucl Phys ◽  
Hadronic Phase ◽  
Parameter Values ◽  
Exchange Data

We analyze the charge-exchange (CX) measurements π-p→π0n below pion laboratory kinetic energy of 100 MeV. After the removal of five degrees of freedom from the initial database, we combine it with the truncated π+p database [E. Matsinos and G. Rasche, J. Mod. Phys.3, 1369 (2012)] and fit the ETH model [P. F. A. Goudsmit, H. J. Leisi, E. Matsinos, B. L. Birbrair and A. B. Gridnev, Nucl. Phys. A575, 673 (1994)] to the resulting data. The set of the parameter values of the ETH model, as well as the predictions derived on their basis for the hadronic phase shifts and for the low-energy πN constants, are significantly different from the results obtained in the analysis of the truncated π±p elastic-scattering databases. The main difference in the hadronic phase shifts occurs in [Formula: see text]. We discuss the implications of these findings in terms of the violation of the isospin invariance in the hadronic part of the πN interaction. The effect observed amounts to the level of 7–8% in the CX scattering amplitude below 70 MeV. The results and conclusions of this study agree well with those obtained in the mid 1990s, when the isospin invariance was first tested by using πN experimental data, and disagree with the predictions obtained within the framework of the heavy-baryon Chiral-Perturbation Theory.

scholarly journals The new IVD Regulation 2017/746: a case study at a large university hospital laboratory in Belgium demonstrates the need for clarification on the degrees of freedom laboratories have to use lab-developed tests to improve patient care

2021 ◽  
Vol 59 (1) ◽  
pp. 101-106
Author(s):  
Pieter. Vermeersch ◽  
Tobias Van Aelst ◽  
Elisabeth M.C. Dequeker
Keyword(s):  
Flow Cytometry ◽  
Laboratory Tests ◽  
Degrees Of Freedom ◽  
Improve Patient Care ◽  
University Hospital ◽  
Molecular Testing ◽  
The European Union ◽  
Off Label ◽  
The Impact

AbstractObjectivesThe new European In Vitro Diagnostic (IVD) Regulation 2017/746 (IVDR) restricts the use of lab-developed tests (LDT) after 26th May 2022. There are no data on the impact of the IVDR on laboratories in the European Union.MethodsLaboratory tests performed in UZ Leuven were divided in four groups: core laboratory, immunology, special chemistry, and molecular microbiology testing. Each test was classified as Conformité Européenne (CE)-IVD, modified/off-label CE-IVD, commercial Research Use Only (RUO) or LDT. Each matrix was considered a separate test.ResultsWe found that 97.6% of the more than 11.5 million results/year were generated with a CE-IVD method. Of the 922 different laboratory tests, however, only 41.8% were CE-IVD, 10.8% modified/off-label CE-IVD, 0.3% RUO, and 47.1% LDT. Off-label CE-IVD was mainly used to test alternative matrices not covered by the claim of the manufacturer (e.g., pleural or peritoneal fluid). LDTs were mainly used for special chemistry, flow cytometry, and molecular testing. Excluding flow cytometry, the main reasons for the use of 377 LDTs were lack of a CE-IVD method (71.9%), analytical requirements (14.3%), and the fact the LDT was in use before CE-IVD available (11.9%).ConclusionsWhile the large majority of results (97.6%) were generated with a CE-IVD method, only 41.8% of laboratory tests were CE-IVD. There is currently no alternative on the market for 71.5% of the 537 LDTs performed in our laboratory which do not fall within the scope of the current IVD directive (IVDD). Compliance with the IVDR will require a major investment of time and effort.

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