Fitted Parameter Values Research Articles

Enhanced 3D parameterization for integrated shape synthesis by fitting parameter values to point sets

Enhanced single-patch NURBS (Non-uniform rational B-splines) parameterization is developed based on fitting parameter values, capable of handling dynamically changing shapes. With respect to NURBS and T-splines, the proposed single-patch parameterizations results in lower dimensionality enabling optimizers to operate on geometric parameters. Avoiding subdivision surfaces and continuity problems for piecewise NURBS and reparameterizations for T-splines accelerates optimization. This parameterization may be an approximation or initial solution for piecewise NURBS and T-splines. These numerical benefits are accomplished using a multi-stage methodology. An augmented set of fitting variables is formulated beyond the weight factors and control points with parameter values of data points. This augmented set is structured to possess reasonable dimensionality. The developed non-linear fitting includes gradient-based minimization with respect to the augmented set and evolutionary error minimization using external functions. The benefits and potential difficulties of the procedure are evaluated thoroughly. The methodology is tested on engineering objects of high shape complexity and demonstrated to provide superior single- patch fitting performance compared to standard linear fitting methods. The developed numerical approach provides for the aspired main objective which is sufficiently accurate and numerically efficient dynamic shape parameterizaton using a compact set of shape parameters.

The potential impact of a prophylactic vaccine for Ebola in Sierra Leone.

The 2014 outbreak of Ebola virus disease (EVD) in West Africa was multinational and of an unprecedented scale primarily affecting the countries of Guinea, Liberia, and Sierra Leone. One of the qualities that makes EVD of high public concern is its potential for extremely high mortality rates (up to 90%). A prophylactic vaccine for ebolavirus (rVSV-ZEBOV) has been developed, and clinical trials show near-perfect efficacy. We have developed an ordinary differential equations model that simulates an EVD epidemic and takes into account (1) transmission through contact with infectious EVD individuals and deceased EVD bodies, (2) the heterogeneity of the risk of becoming infected with EVD, and (3) the increased survival rate of infected EVD patients due to greater access to trained healthcare providers. Using fitted parameter values that closely simulate the dynamics of the 2014 outbreak in Sierra Leone, we utilize our model to predict the potential impact of a prophylactic vaccine for the ebolavirus using various vaccination strategies including ring vaccination. Our results show that an rVSV-ZEBOV vaccination coverage as low as 40% in the general population and 95% in healthcare workers will prevent another catastrophic outbreak like the 2014 outbreak from occurring.

Comparing three models to estimate transpiration of desert shrubs

The role of environmental variables in controlling transpiration (Ec) is an important, but not well-understood, aspect of transpiration modeling in arid desert regions. Taking three dominant desert shrubs, Haloxylon ammodendron, Nitraria tangutorum, and Calligonum mongolicum, as examples, we aim to evaluate the applicability of three transpiration models, i.e. the modified Jarvis-Stewart model (MJS), the simplified process-based model (BTA), and the artificial neural network model (ANN) at different temporal scales. The stem sap flow of each species was monitored using the stem heat balance approach over both the 2014 and 2015 main growing seasons. Concurrent environmental variables were also measured with an automatic weather station. The ANN model generally produced better simulations of Ec than the MJS and BTA models at both hourly and daily scales, indicating its advantage in solving complicated, nonlinear problems between transpiration rate and environmental driving forces. The solar radiation and vapor pressure deficit were crucial variables in modeling Ec for all three species. The performance of the MJS and ANN models was significantly improved by incorporating root-zone soil moisture. We also found that the difference between hourly and daily fitted parameter values was considerable for the MJS and BTA models. Therefore, these models need to be recalibrated when applied at different temporal scales. This study provides insights regarding the application and performance of current transpiration models in arid desert regions, and thus provides a deeper understanding of eco-hydrological processes and sustainable ecosystem management at the study site.

Distinguishing physical mechanisms using GISAXS experiments and linear theory: the importance of high wavenumbers

In this work we analyze GISAXS measurements of the structure factor of Si surfaces evolving during 1 keV Ar+ ion bombardment. Using newly-developed methods sensitive to the full range of experimentally-available wavenumbers q, we extract the linear amplification rate R(q) governing surface stability over a range of wavenumbers 4–5 times larger than has previously been obtained. Comparing with theoretical models also retaining full wavenumber-dependence, we find an excellent fit of the experimental data over the full range of irradiation angles and wavenumbers. Moreover, the fitted parameter values represent experimental evaluation of the magnitudes of most physical mechanisms currently believed to be important to the pattern-formation process. In all cases, the extracted values agree well with direct observations or atomistic simulations of the same quantities, suggesting that GISAXS analysis may allow more powerful comparison between experiment and theory than had previously been thought.

Utilization of the bootstrap method for determining confidence intervals of parameters for a model of MAP1B protein transport in axons

This paper develops a model of axonal transport of MAP1B protein. The problem of determining parameter values for the proposed model utilizing limited available experimental data is addressed. We used a global minimum search algorithm to find parameter values that minimize the discrepancy between model predictions and published experimental results. By analyzing the best fit parameter values it was established that some processes can be dropped from the model without losing accuracy, thus a simplified version of the model was formulated. In particular, our analysis suggests that reversals in MAP1B transport are infrequent and can be neglected. The detachment of anterogradely-biased MAP1B from microtubules (MTs) and the attachment of retrogradely-biased MAP1B to MTs can also be neglected. An analytical solution for the simplified model was obtained. Confidence intervals for the determined parameters were found by bootstrapping model residuals. The resultant analysis heavily constrained the values of some parameters while showing that some could vary without significantly impacting model error. For example, our analysis suggests that, above a certain threshold value, the kinetic constant determining the rate of MAP1B transition from the retrograde pausing state to the off-track state has little impact on model error. On the contrary, the kinetic constant describing MAP1B transition from a pausing to a running state has great impact on model error.

A simple correlation for prediction of thermal conductivity of liquid hydrocarbons and aromatics

Thermal conductivity is one of the most important properties of materials especially liquids. Thermal conductivity is highly interesting since it is the main parameter required for most heat-transfer calculations or design of industrial equipments such as heat exchangers. Unfortunately, thermal conductivity is extremely hard to be experimentally measured due to some operational issues which shifted the researchers’ interest toward proposing a correlation to predict this property. In the light of this limitation, in the current study, a four-parameter correlation based on critical temperature ([Formula: see text], critical pressure ([Formula: see text] and acentric factor ([Formula: see text] of substances is proposed to predict thermal conductivity of liquids. In this way, 956 experimental data points collected from previously published literatures were divided into two different subsets, namely training and testing subsets, in the first stage and then used to find the optimum values of fitting parameters of the proposed correlation. Based on the obtained results of error analysis, it can be concluded that the proposed correlation has capability of both extrapolating and correlating the thermal conductivity of liquids.

Stochastic model for simulation of near‐fault ground motions

SummaryA parameterized stochastic model of near‐fault ground motion in two orthogonal horizontal directions is developed. The major characteristics of recorded near‐fault ground motions are represented. These include near‐fault effects of directivity and fling step; temporal and spectral non‐stationarity; intensity, duration, and frequency content characteristics; directionality of components; and the natural variability of ground motions. Not all near‐fault ground motions contain a forward directivity pulse, even when the conditions for such a pulse are favorable. The proposed model accounts for both pulse‐like and non‐pulse‐like cases. The model is fitted to recorded near‐fault ground motions by matching important characteristics, thus generating an ‘observed’ set of model parameters for different earthquake source and site characteristics. A method to generate and post‐process synthetic motions for specified model parameters is also presented. Synthetic ground motion time series are generated using fitted parameter values. They are compared with corresponding recorded motions to validate the proposed model and simulation procedure. The use of synthetic motions in addition to or in place of recorded motions is desirable in performance‐based earthquake engineering applications, particularly when recorded motions are scarce or when they are unavailable for a specified design scenario. Copyright © 2016 John Wiley & Sons, Ltd.

Dynamic regulation of auxin oxidase and conjugating enzymes AtDAO1 and GH3 modulates auxin homeostasis

The hormone auxin is a key regulator of plant growth and development, and great progress has been made understanding auxin transport and signaling. Here, we show that auxin metabolism and homeostasis are also regulated in a complex manner. The principal auxin degradation pathways in Arabidopsis include oxidation by Arabidopsis thaliana gene DIOXYGENASE FOR AUXIN OXIDATION 1/2 (AtDAO1/2) and conjugation by Gretchen Hagen3s (GH3s). Metabolic profiling of dao1-1 root tissues revealed a 50% decrease in the oxidation product 2-oxoindole-3-acetic acid (oxIAA) and increases in the conjugated forms indole-3-acetic acid aspartic acid (IAA-Asp) and indole-3-acetic acid glutamic acid (IAA-Glu) of 438- and 240-fold, respectively, whereas auxin remains close to the WT. By fitting parameter values to a mathematical model of these metabolic pathways, we show that, in addition to reduced oxidation, both auxin biosynthesis and conjugation are increased in dao1-1 Transcripts of AtDAO1 and GH3 genes increase in response to auxin over different timescales and concentration ranges. Including this regulation of AtDAO1 and GH3 in an extended model reveals that auxin oxidation is more important for auxin homoeostasis at lower hormone concentrations, whereas auxin conjugation is most significant at high auxin levels. Finally, embedding our homeostasis model in a multicellular simulation to assess the spatial effect of the dao1-1 mutant shows that auxin increases in outer root tissues in agreement with the dao1-1 mutant root hair phenotype. We conclude that auxin homeostasis is dependent on AtDAO1, acting in concert with GH3, to maintain auxin at optimal levels for plant growth and development.

Rate-equation modelling and ensemble approach to extraction of parameters for viral infection-induced cell apoptosis and necrosis.

We develop a theoretical approach that uses physiochemical kinetics modelling to describe cell population dynamics upon progression of viral infection in cell culture, which results in cell apoptosis (programmed cell death) and necrosis (direct cell death). Several model parameters necessary for computer simulation were determined by reviewing and analyzing available published experimental data. By comparing experimental data to computer modelling results, we identify the parameters that are the most sensitive to the measured system properties and allow for the best data fitting. Our model allows extraction of parameters from experimental data and also has predictive power. Using the model we describe interesting time-dependent quantities that were not directly measured in the experiment and identify correlations among the fitted parameter values. Numerical simulation of viral infection progression is done by a rate-equation approach resulting in a system of "stiff" equations, which are solved by using a novel variant of the stochastic ensemble modelling approach. The latter was originally developed for coupled chemical reactions.

Creep analysis of silicone for podiatry applications

Purpose. This work shows an effective methodology to characterize the creep–recovery behavior of silicones before their application in podiatry. The aim is to characterize, model and compare the creep–recovery properties of different types of silicone used in podiatry orthotics.Methods. Creep–recovery phenomena of silicones used in podiatry orthotics is characterized by dynamic mechanical analysis (DMA). Silicones provided by Herbitas are compared by observing their viscoelastic properties by Functional Data Analysis (FDA) and nonlinear regression. The relationship between strain and time is modeled by fixed and mixed effects nonlinear regression to compare easily and intuitively podiatry silicones.Results. Functional ANOVA and Kohlrausch–Willians–Watts (KWW) model with fixed and mixed effects allows us to compare different silicones observing the values of fitting parameters and their physical meaning. The differences between silicones are related to the variations of breadth of creep–recovery time distribution and instantaneous deformation-permanent strain. Nevertheless, the mean creep-relaxation time is the same for all the studied silicones. Silicones used in palliative orthoses have higher instantaneous deformation-permanent strain and narrower creep–recovery distribution.Conclusions. The proposed methodology based on DMA, FDA and nonlinear regression is an useful tool to characterize and choose the proper silicone for each podiatry application according to their viscoelastic properties.

Dielectric properties and electromagnetic interference shielding effectiveness of graphene-based biodegradable nanocomposites

Graphene nanoplatelets (GNPs) were dispersed in poly lactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) via melt-mixing. Effect of GNP incorporation on electromagnetic properties and electromagnetic interference shielding effectiveness (SE) of PLA and PBAT was investigated and the two systems were systematically compared. Furthermore, applicability of Sihvola's mixing rule of complex electrical permittivity to these nanocomposites was studied. GNP addition significantly enhanced permittivity of both polymers. Dielectric constants of PLA and PBAT nanocomposites had comparable values. However, above 6wt% GNPs, PLA nanocomposites showed significantly higher dielectric loss than PBAT nanocomposites, even though pure PLA had lower dielectric loss than pure PBAT. This was attributed to the dispersion state of GNPs in the two matrices, detected in morphological studies. SE of both polymers increased with GNP addition due to enhancement of their dielectric properties. The difference in dielectric loss of the two systems was revealed in their ability to attenuate the radiation by absorption. At 15wt% GNPs, 1mm-thick PLA/GNP nanocomposite had an effective absorbance of 70%. This value was only 43% for PBAT/GNP nanocomposite. Variations of polymers' permittivities with GNPs were successfully modelled by Sihvola's rule. While both systems returned close values for model's fitting parameters, it better fitted PBAT/GNP nanocomposites.

P.072 The spectrotemporal characteristics of NMDA receptor encephalitis

Background: NMDA receptor encephalitis (NMDA-RE) is an autoimmune disorder caused by antibodies to the NR1-NR2B heterodimer of the NMDA receptor. Currently, disease status is tracked primarily by the presence of auto-antibodies in the cerebrospinal fluid (CSF) and serum. Using serological and CSF markers along with clinical parameters to track disease progress can be challenging since patient symptoms and disease progress can vary widely. Methods: EEGs were reviewed in a 31 year old male patient with proven NMDA-RE. EEG data were sampled from various times before and after diagnosis, as well as during various stages of treatment. All analyses were performed using Matlab (Mathworks). Results: We showed that using a simple 1/f model of spectral behaviour (Buzsaki and Draguhn, 2004), we could fit the power spectra of the raw data at various instances during routine EEGs. We have demonstrated that the values of specific fitting parameters vary in relationship to the patient’s clinical status across various stages of illness. Conclusions: The aim of this project was to explore the potential utility of EEG as a complement to the usual clinical metrics used in monitoring NMDA-RE. The analysis techniques presented here highlight the use of EEG as a practical, minimaly-invasive tool to monitor progress and potentially aid in clinical decision making.

Dimensional analysis and extended hydrodynamic theory applied to long-rod penetration of ceramics

Abstract Principles of dimensional analysis are applied in a new interpretation of penetration of ceramic targets subjected to hypervelocity impact. The analysis results in a power series representation – in terms of inverse velocity – of normalized depth of penetration that reduces to the hydrodynamic solution at high impact velocities. Specifically considered are test data from four literature sources involving penetration of confined thick ceramic targets by tungsten long rod projectiles. The ceramics are AD-995 alumina, aluminum nitride, silicon carbide, and boron carbide. Test data can be accurately represented by the linear form of the power series, whereby the same value of a single fitting parameter applies remarkably well for all four ceramics. Comparison of the present model with others in the literature (e.g., Tate's theory) demonstrates a target resistance stress that depends on impact velocity, linearly in the limiting case. Comparison of the present analysis with recent research involving penetration of thin ceramic tiles at lower typical impact velocities confirms the importance of target properties related to fracture and shear strength at the Hugoniot Elastic Limit (HEL) only in the latter. In contrast, in the former (i.e., hypervelocity and thick target) experiments, the current analysis demonstrates dominant dependence of penetration depth only by target mass density. Such comparisons suggest transitions from microstructure-controlled to density-controlled penetration resistance with increasing impact velocity and ceramic target thickness.

Photoluminescence and Energy Transfer Between Sm <sup>3+</sup> Ions in LaF<sub>3</sub> Nanocrystals Prepared by Hydrothermal Method

The aim of this research is to study photoluminescent properties and particularly energy transfer between Sm3+ ions in LaF3 nanocrystals because the energy transfer process has a significant effect on the luminescence efficiency and lifetime. Sm3+-doped LaF3 nanocrystals with 0.1, 0.2, 0.3, 1.0, 2.0, 3.0, 4.0 and 5.0 mol% Sm3+ have been prepared by hydrothermal method. The obtained nanocrystals were characterized by X-ray diffraction, transmission electron microscopy, photoluminescence and luminescence decay measurement. The results showed that the LaF3:Sm3+ nanocrystals possess hexagonal structure with <img width="29" height="16" src="http://article.sciencepublishinggroup.com/journal/123/1231229/image001.png" /> space group. The room temperature photoluminescence and photoluminescence excitation spectra of LaF3:Sm3+ were investigated in detail and interpreted by optical intra-configurational f–f transitions within Sm3+ ions. When Sm3+ ion concentration in the nanocrystals is increased, the excitation energy is transferred from the “bulk” Sm3+ ions to the surface Sm3+ ions followed by non-radiative recombination at centers at the surface of the nanocrystals. The photoluminescence decay curves of 593 nm peak in the LaF3 nanocrystals doped with 1.0-5.0 mol% Sm3+ were best fitted to the Inokuti-Hirayama model with the dominant dipole-quadrupole interaction (S = 8). The values of fitting parameters for the energy transfer process were determined.

Estimating Important Electrode Parameters of High Temperature PEM Fuel Cells by Fitting a Model to Polarisation Curves and Impedance Spectra

A high temperature PEM (HTPEM) fuel cell model capable of simulating both steady state and dynamic operation is presented. The purpose is to enable extraction of unknown parameters from sets of impedance spectra and polarisation curves. The model is fitted to two polarisation curves and four impedance spectra measured on a Dapozol 77 MEA. The model is capable of achieving good agreement with the recorded curves. Except at OCV, where the voltage is overpredicted, the simulated polarisation curves deviate maximum 3.0% from the measurements. The impedance spectra deviate maximum 3.7%. The fitted parameter values are within the range reported in literature. The only exception is the catalyst layer acid content, which is an order of magnitude lower. This may derive from acid migration. The model is used to illustrate the effect of reactant dynamics on the impedance spectrum. The model can aid in the analysis of data from degradation tests.

The fourth spectrum of iridium (Ir IV)

The spectrum of three times ionized iridium, Ir IV, was investigated in the 650–2045 Å wavelength region. The analysis has led to the determination of the 5d6, 5d56s and 5d56p configurations. Twenty-nine of 34 theoretically possible 5d6 levels, 44 of 74 possible 5d56s levels and 150 of 214 possible 5d56p levels have been established. The levels are based on 1348 classified spectral lines. The level structure and transition probabilities were calculated using the orthogonal operators technique. The energy parameters have been determined by the least squares fit to the observed levels. Calculated energy values and LS-compositions obtained from the fitted parameter values are given. The level optimization procedure and the determination of uncertainties of the obtained energy level values are discussed.

The fourth spectrum of platinum (Pt IV): Determination of the [formula omitted], [formula omitted] and [formula omitted] configurations

The spectrum of three times ionized platinum, Pt IV, was investigated in the 530–1800 Å wavelength region. The analysis has resulted in the determination of the 5d7, 5d66s and 5d66p configurations. Seventeen of 19 theoretically possible 5d7 levels, 58 of 63 possible 5d66s levels and 162 of 180 possible 5d66p levels have been established. The levels are based on 1478 classified spectral lines. The level structure and transition probabilities were calculated by means of the orthogonal operators method. The energy parameters have been determined by the least squares fit to the observed levels. Calculated energy values and LS-compositions, as well as gA values obtained from the fitted parameter values are presented.

The Potential Distribution and Risk Assessment of Pratylenchus zeae on Maize in Belgium and The Netherlands

A pest risk assessment (PRA) was carried out on Pratylenchus zeae on maize as host in Belgium and the Netherlands as the pest risk assessment areas where the organism is yet to be reported owing to potential phytosanitary concerns that its introduction to this areas might cause economically. To assess the potential geographic distribution of the pest in the study areas and other areas in Europe out of its current areas of occurrence, two tools were used for the study; CLIMEX, a computer simulation model and the European and Mediterranean Plant Protection Organization PRA guidelines to see if the pests can be introduced and established in the pest risk assessment areas. Geographic distribution data for P. zeae in its current locations were used to fit parameter values in the CLIMEX program. The CLIMEX analysis suggests that P. zeae can potentially become introduced in one of the study area and other parts of Europe and other climatically suitable regions of the world. The conclusion from the study was based on the combination of the results from both CLIMEX and the PRA guidelines since the use of only one may not give very reliable results. CLIMEX works mainly with climatological data while the PRA guidelines involve the use of biological data for which most are not available for the organisms. The analysis of Pratylenchus zeae which in Europe was only reported in Bulgaria and most recently in Slovenia, Austria, Croatia and Turkey, shows that the pest can become established upon introduction through plant and plant materials moving in trade in Belgium and not in the Netherlands although its effect on crop yield maybe low due to cooler climates obtainable in this areas. Because of its very low impact after introduction, the pest does not have the characteristics of a quarantine organism.

Photocatalytic odor abatement by platinized TiO2 under optically transmitted LED–UV light

Combined use of platinized titania and light emitting diode (LED) ultraviolet (UV) illumination was explored for photocatalytic odor abatement with carbon disulfide (CS2) as model odorant. Noble metal deposition on anatase titanium dioxide (TiO2) surface was achieved by UV assisted photoreduction of platinum (Pt). Solid-state and elemental analyses show that surface platinized (Pt/TiO2) and bare (TiO2) titania, while of comparable bulk structural properties, differ in light absorption and surface characteristics as a result of the photodeposited Pt. The effect of distance and collimation was modeled to predict the impact of position of UV source and collimation on UV radiation intensity and distribution on photocatalyst surface. Increased radiation intensity due to minimized divergence with collimated LED–UV has improved output beam intensity, resulting in enhanced photoreaction rates regardless of photocatalyst used. Fitting of batch experimental data into classical Langmuir–Hinshelwood (L–H) kinetic model yielded higher model parameter values with Pt/TiO2 than TiO2 as well as the calcined counterparts. Lower number of surface OH groups and better charge carrier separation in calcined and/or Pt surface treated titania were proposed as main factors underpinning enhanced reaction rates and photonic efficiencies. Data fitting into a pseudo-steady-state L–H kinetic model has returned higher optimized fit parameter values with Pt/TiO2 than TiO2 while showing a nonlinear power law relationship between irradiation intensity and reaction rate. Results of fluorescence excitation-emission (EEM) spectroscopy and infrared (IR) thermography corroborate the occurrence of localized surface plasmon resonance (LSPR) effects such as subdued fluorescence and localized heating. By employing plasmonic photocatalysts and innovative delivery of photoradiation, this study has presented a case of a straightforward approach to environmental odor abatement based on affordable and widely available UV–LEDs and titania support.

Theoretical calculations of energies, and radiative rates for parity-forbidden transitions within the 4f3 configuration in La-like ions Pr2+ and Nd3+

The observed 4f3 energy levels of La isoelectronic sequence ions Pr2+ and Nd3+ were analyzed using a standard f-shell free-ion Hamiltonian. The root mean square (rms) deviation of 13.54cm−1, 6.17cm−1 between calculated and observed energies was obtained from the fit of 16 free-ion parameters to 38 levels for Pr2+, and to the complete set of 41 levels for Nd3+, respectively. Then, the fitted values of free-ion parameters were used to compute wavelengths, oscillator strengths, and transition rates for the forbidden magnetic dipole and electric quadrupole transitions between the 4f3 levels in Pr2+ and Nd3+ La-like ions. Detailed comparisons with other available theoretical data are also reported and discussed in this work.