Optimal Design of Biaxial Tests for Structural Material Characterization of Flat Tissues

1996 ◽  
Vol 118 (1) ◽  
pp. 41-47 ◽  
Author(s):  
Y. Lanir ◽  
O. Lichtenstein ◽  
O. Imanuel
Keyword(s):  
Optimal Design ◽  
Material Characterization ◽  
Structural Model ◽  
Optimal Designs ◽  
Model Parameters ◽  
Optimal Sampling ◽  
Material Symmetry ◽  
Wide Range ◽  
Biaxial Tests

A rational methodology is developed for optimal design of biaxial stretch tests intended for estimating material parameters of flat tissues. It is applied to a structural model with a variety of constitutive equations and test protocols, and for a wide range of parameter levels. The results show nearly identical optimal designs under all circumstances. Optimality is obtained with two uniaxial stretch tests at mutually normal directions inclined by 22.5 deg to the axes of material symmetry. Protocols which include additional equibiaxial tests provide superior estimation with lower variance of estimates. Tests performed at angles 0, 45, and 90 deg to the axes of material symmetry provide unreliable estimates. The optimal sampling is variable and depends on the protocols and model parameters. In conclusion, the results indicate that biaxial tests can be improved over presently common procedures and show that this conclusion applies for a variety of circumstances.

scholarly journals Testing parallelism for the four-parameter logistic model with D-optimal design

2020 ◽  
Vol 15 (3) ◽  
pp. 273-284
Author(s):  
Lin Ying ◽  
Hyun Seung Won
Keyword(s):  
Optimal Design ◽  
Logistic Model ◽  
Test Preparation ◽  
Test Sample ◽  
Optimal Designs ◽  
Model Parameters ◽  
Reference Standard ◽  
Response Curves ◽  
Classical Design ◽  
Intersection Union Test

In order to determine the potency of the test preparation relative to the standard preparation, it is often important to test parallelism between a pair of dose-response curves of reference standard and test sample. Optimal designs are known to be more powerful in testing parallelism as compared to classical designs. In this study, D-optimal design was implemented to study the parallelism and compare+ its performance with a classical design. We modified D-optimal design to test the parallelism in the four-parameter logistic (4PL) model using Intersection-Union Test (IUT). IUT method is appropriate when the null hypothesis is expressed as a union of sets, and by using this method complicated tests involving several parameters are easily constructed. Since D-optimal design minimizes the variances of model parameters, it can bring more power to the IUT test. A simulation study will be presented to compare the empirical properties of the two different designs.

Holistic Characterization of Carbon Nanotube Membrane for Capacitive Deionization Electrodes Application

2015 ◽  
Vol 1752 ◽  
pp. 125-130 ◽  
Author(s):  
Yamila M. Omar ◽  
Carlo Maragliano ◽  
Chia-Yun Lai ◽  
Francesco Lo Iacono ◽  
Nicolas Bologna ◽  
...  
Keyword(s):  
Thin Film ◽  
Material Characterization ◽  
Capacitive Deionization ◽  
Carbon Nanostructure ◽  
Rate Dependent ◽  
Wide Range ◽  
Materials Used ◽  
Multiwall Carbon ◽  
Mechanical Surface

ABSTRACTOne of the main areas of improvement in capacitive deionization technologies is the materials used for electrodes which have very specific requirements. In the present work, a wide range of material characterization techniques are employed to determine the suitability of a multiwall carbon nanostructure thin film as electrode material. The electrical, mechanical, surface and wetting characteristics are studied proving the membrane highly conductive (σ=7.25 103 S/m), having competitive electro-sorption capacity (11.7 F/g at 10 mV/s) and surface area (149 m2/g), strain rate dependent mechanical properties and hydrophobic wetting behavior.

SQUID NDE Apparatus and Magnetic Calibration to Detect Degradation in Duplex Stainless Steel

1992 ◽  
Vol 114 (1) ◽  
pp. 41-45 ◽  
Author(s):  
S. Evanson ◽  
M. Otaka ◽  
K. Hasegawa
Keyword(s):  
Magnetic Material ◽  
Stainless Steel ◽  
Magnetic Permeability ◽  
Material Characterization ◽  
Residual Magnetization ◽  
Duplex Steel ◽  
Wide Range ◽  
Remote Measurements ◽  
Steel Grades

We report on apparatus for the magnetic material characterization of a wide range of steel grades of high and low magnetic permeability. The instrument has been used to detect thermal aging in Duplex steel by the measurement of the residual magnetization (Br) of test specimens. A method to estimate the value of Br by remote measurements up to 200 mm from a specimen is described. The results are compared with data from conventional hysteresis loop measurements.

scholarly journals Structural characterization of ice XIX as the second polymorph related to ice VI

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tobias M. Gasser ◽  
Alexander V. Thoeny ◽  
A. Dominic Fortes ◽  
Thomas Loerting
Keyword(s):  
High Resolution ◽  
Structural Characterization ◽  
Structural Model ◽  
Neutron Powder Diffraction ◽  
Ex Situ ◽  
Nucleation Kinetics ◽  
Icy Moons ◽  
First Order ◽  
Wide Range

AbstractIce polymorphs usually appear as hydrogen disorder-order pairs. Ice VI has a wide range of thermodynamic stability and exists in the interior of Earth and icy moons. Our previous work suggested ice β-XV as a second polymorph deriving from disordered ice VI, in addition to ice XV. Here we report thermal and structural characterization of the previously inaccessible deuterated polymorph using ex situ calorimetry and high-resolution neutron powder diffraction. Ice β-XV, now called ice XIX, is shown to be partially antiferroelectrically ordered and crystallising in a √2×√2×1 supercell. Our powder data recorded at subambient pressure fit best to the structural model in space group $$P\bar 4$$ P 4 ¯ . Key to the synthesis of deuterated ice XIX is the use of a DCl-doped D2O/H2O mixture, where the small H2O fraction enhances ice XIX nucleation kinetics. In addition, we observe the transition from ice XIX to its sibling ice XV upon heating, which proceeds via a transition state (ice VI‡) containing a disordered H-sublattice. To the best of our knowledge this represents the first order-order transition known in ice physics.

New frontiers in infrared microspectroscopy

1992 ◽  
Vol 50 (2) ◽  
pp. 1522-1523
Author(s):  
M. A. Harthcock ◽  
M. L. McKelvy ◽  
R. J. Pell
Keyword(s):  
Spatial Resolution ◽  
Material Characterization ◽  
Functional Group ◽  
Analysis Techniques ◽  
Infrared Microspectroscopy ◽  
System Composition ◽  
Wide Range ◽  
Common Technique ◽  
Experimental Technology

Infrared microspectroscopy has become a common technique for the microanalysis of material. Characterization of spatially specific areas using infrared spectroscopy has been applied to a wide range of materials/systems including, for example, multi-layer films, silicon wafer contamination and inclusions in a variety of systems, surface contamination, orientation in single fibers. In addition, infrared microspectroscopy mapping experiments have been used to obtain images of materials based on functional group absorptions that characterize system composition.The spatial resolution of the technique is limited to approximately 10-20 micrometers experimentally, due to diffraction limitations. Infrared ultra-microspectroscopy has been mentioned by Messerschmidt as a technique to achieve resolution below the diffraction limit of the radiation (e.g. 5 micrometers). However, in the absence of experimental technology to routinely increase the spatial resolution from which unique infrared spectra can be obtained, we have applied factor analysis techniques to effectively increase the spatial resolution from which an infrared spectrum could be obtained.

scholarly journals Optimal Sampling Regimes for Estimating Population Dynamics

Stats ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 291-307
Author(s):  
Rebecca E. Atanga ◽  
Edward L. Boone ◽  
Ryad A. Ghanam ◽  
Ben Stewart-Koster
Keyword(s):  
Population Growth ◽  
Monte Carlo Sampling ◽  
Optimal Designs ◽  
Logistic Growth ◽  
Model Parameters ◽  
Optimal Sampling ◽  
Ecological Data ◽  
Time Frequency ◽  
Regular Time ◽  
Expensive Process

Ecologists are interested in modeling the population growth of species in various ecosystems. Specifically, logistic growth arises as a common model for population growth. Studying such growth can assist environmental managers in making better decisions when collecting data. Traditionally, ecological data is recorded on a regular time frequency and is very well-documented. However, sampling can be an expensive process due to available resources, money and time. Limiting sampling makes it challenging to properly track the growth of a population. Thus, this design study proposes an approach to sampling based on the dynamics associated with logistic growth. The proposed method is demonstrated via a simulation study across various theoretical scenarios to evaluate its performance in identifying optimal designs that best estimate the curves. Markov Chain Monte Carlo sampling techniques are implemented to predict the probability of the model parameters using Bayesian inference. The intention of this study is to demonstrate a method that can minimize the amount of time ecologists spend in the field, while maximizing the information provided by the data.

scholarly journals Optimal Sampling Schedule Design for Populations of Patients

2003 ◽  
Vol 47 (9) ◽  
pp. 2888-2891 ◽  
Author(s):  
Vincent H. Tam ◽  
Sandra L. Preston ◽  
G. L. Drusano
Keyword(s):  
Optimal Design ◽  
Pharmacokinetic Parameter ◽  
Design Theory ◽  
Population Pharmacokinetic Analysis ◽  
Posteriori Probability ◽  
Pharmacokinetic Analysis ◽  
Population Pharmacokinetic ◽  
Optimal Sampling ◽  
Wide Range ◽  
Parameter Values

ABSTRACT Generation of pharmacodynamic relationships in the clinical arena requires estimation of pharmacokinetic parameter values for individual patients. When the target population is severely ill, the ability to obtain traditional intensive blood sampling schedules is curtailed. Population modeling guided by optimal sampling theory has provided robust estimates of individual patient pharmacokinetic parameter values. Because of the wide range of parameter values seen in this circumstance, it is important to know how the range of parameter values in the population affects the timing of the optimal samples. We describe a new, simple technique to obtain optimal samples for a population of patients. This technique uses the nonparametric distribution associated with a nonparametric adaptive grid population pharmacokinetic analysis. We used the distribution from an analysis of 58 patients receiving levofloxacin for nosocomial pneumonia at a dose of 750 mg. The collection of parameter vectors and their associated probabilities were entered into a D-optimal design evaluation by using ADAPT II. The sampling times, weighted for their probabilities, were displayed in a frequency histogram (an expression of how system information varies with time for the population). Such an explicit expression of the time distribution of information allows rational sampling design that is robust not only for the population mean vector, as in traditional D-optimal design theory, but also for large portions of the total population. For levofloxacin, one reasonable six-sample design would be 1.5, 2, 2.25, 4, 4.75, and 24 h after starting a 90-min infusion. Such sampling designs allow informative population pharmacokinetic analysis with precise and unbiased estimates after the maximal a posteriori probability Bayesian step. This allows the highest probability of delineating a pharmacodynamic relationship.

Time-Dependent Mechanical Behavior of Sheep Digital Tendons, Including the Effects of Preconditioning

2001 ◽  
Vol 124 (1) ◽  
pp. 78-84 ◽  
Author(s):  
A. Sverdlik ◽  
Y. Lanir
Keyword(s):  
Mechanical Properties ◽  
Material Characterization ◽  
Predictive Power ◽  
Structural Model ◽  
Strain Level ◽  
Time Dependent ◽  
Model Data ◽  
Reference Length ◽  
Good Agreement

The time-dependent mechanical properties of sheep digital extensor tendons were studied by sequences of stress-relaxation tests. The results exhibited irreversible preconditioning and reversible viscoelasticity. Preconditioning effects were manifested by stress decay during consecutive stretch cycles to the same strain level, accompanied by elongation of the tendon’s reference length. They intensified with increased strain level, and were reduced or became negligible as the strain decreased. The significance of intrinsic response mechanisms was studied via a structural model that includes viscoelasticity, preconditioning, and morphology of the tendon’s collagen fibers. Model/data comparisons showed good agreement and good predictive power, suggesting that preconditioning can be integrated into comprehensive material characterization of tendons.

Strongly Coupled Redox-Linked Conformational Switching at the Active Site of the Non-Heme Iron-Dependent Dioxygenase, TauD

2019 ◽  
Author(s):  
Christopher John ◽  
Greg M. Swain ◽  
Robert P. Hausinger ◽  
Denis A. Proshlyakov
Keyword(s):  
Active Site ◽  
Structural Model ◽  
Heme Iron ◽  
Chemical Transformations ◽  
Experimental Conditions ◽  
Strongly Coupled ◽  
Non Heme Iron ◽  
Reversible Redox ◽  
Wide Range ◽  
Complex Structural

2-Oxoglutarate (2OG)-dependent dioxygenases catalyze C-H activation while performing a wide range of chemical transformations. In contrast to their heme analogues, non-heme iron centers afford greater structural flexibility with important implications for their diverse catalytic mechanisms. We characterize an <i>in situ</i> structural model of the putative transient ferric intermediate of 2OG:taurine dioxygenase (TauD) by using a combination of spectroelectrochemical and semi-empirical computational methods, demonstrating that the Fe (III/II) transition involves a substantial, fully reversible, redox-linked conformational change at the active site. This rearrangement alters the apparent redox potential of the active site between -127 mV for reduction of the ferric state and 171 mV for oxidation of the ferrous state of the 2OG-Fe-TauD complex. Structural perturbations exhibit limited sensitivity to mediator concentrations and potential pulse duration. Similar changes were observed in the Fe-TauD and taurine-2OG-Fe-TauD complexes, thus attributing the reorganization to the protein moiety rather than the cosubstrates. Redox difference infrared spectra indicate a reorganization of the protein backbone in addition to the involvement of carboxylate and histidine ligands. Quantitative modeling of the transient redox response using two alternative reaction schemes across a variety of experimental conditions strongly supports the proposal for intrinsic protein reorganization as the origin of the experimental observations.

Q-optimal experimental designs and close to them experimental designs for polynomial regression on the interval

2020 ◽  
Vol 86 (5) ◽  
pp. 65-72
Author(s):  
Yu. D. Grigoriev
Keyword(s):  
Optimal Design ◽  
Polynomial Regression ◽  
Direct Consequence ◽  
Experimental Designs ◽  
Optimal Designs ◽  
Software Systems ◽  
General Character ◽  
Support Points ◽  
Optimal Weights ◽  
Universal Expression

The problem of constructing Q-optimal experimental designs for polynomial regression on the interval [–1, 1] is considered. It is shown that well-known Malyutov – Fedorov designs using D-optimal designs (so-called Legendre spectrum) are other than Q-optimal designs. This statement is a direct consequence of Shabados remark which disproved the Erdős hypothesis that the spectrum (support points) of saturated D-optimal designs for polynomial regression on a segment appeared to be support points of saturated Q-optimal designs. We present a saturated exact Q-optimal design for polynomial regression with s = 3 which proves the Shabados notion and then extend this statement to approximate designs. It is shown that when s = 3, 4 the Malyutov – Fedorov theorem on approximate Q-optimal design is also incorrect, though it still stands for s = 1, 2. The Malyutov – Fedorov designs with Legendre spectrum are considered from the standpoint of their proximity to Q-optimal designs. Case studies revealed that they are close enough for small degrees s of polynomial regression. A universal expression for Q-optimal distribution of the weights pi for support points xi for an arbitrary spectrum is derived. The expression is used to tabulate the distribution of weights for Malyutov – Fedorov designs at s = 3, ..., 6. The general character of the obtained expression is noted for Q-optimal weights with A-optimal weight distribution (Pukelsheim distribution) for the same problem statement. In conclusion a brief recommendation on the numerical construction of Q-optimal designs is given. It is noted that in this case in addition to conventional numerical methods some software systems of symbolic computations using methods of resultants and elimination theory can be successfully applied. The examples of Q-optimal designs considered in the paper are constructed using precisely these methods.

Sign in / Sign up

Export Citation Format

Share Document