scholarly journals Nonlinear mixed model approaches to estimating merchantable bole volume for Pinus occidentalis

2012 ◽  
Vol 5 (1) ◽  
pp. 247-254 ◽  
Author(s):  
S Bueno-López ◽  
E Bevilacqua
Keyword(s):  
Mixed Model ◽  
Nonlinear Mixed Model ◽  
Pinus Occidentalis

scholarly journals Skill Transference of a Probe-Tube Placement Training Simulator

2020 ◽  
Vol 31 (01) ◽  
pp. 040-049 ◽  
Author(s):  
Robert W. Koch ◽  
Hasan Saleh ◽  
Paula Folkeard ◽  
Sheila Moodie ◽  
Conner Janeteas ◽  
...  
Keyword(s):  
Mixed Model ◽  
Tracking System ◽  
Optical Tracking ◽  
Tube Placement ◽  
Control Group ◽  
Educational Settings ◽  
Training Simulator ◽  
Nonlinear Mixed Model ◽  
Optical Tracking System ◽  
Clinical Scenarios

AbstractProbe-tube placement is a necessary step in hearing aid verification which needs ample hands-on experience and confidence before performing in clinic. To improve the methods of training in probe-tube placement, a manikin-based training simulator was developed consisting of a 3D-printed head, a flexible silicone ear, and a mounted optical tracking system. The system is designed to provide feedback to the user on the depth and orientation of the probe tube, and the time required to finish the task. Although a previous validation study was performed to determine its realism and teachability with experts, further validation is required before implementation into educational settings.This study aimed to examine the skill transference of a newly updated probe-tube placement training simulator to determine if skills learned on this simulator successfully translate to clinical scenarios.All participants underwent a pretest in which they were evaluated while performing a probe-tube placement and real-ear-to-coupler difference (RECD) measurement on a volunteer. Participants were randomized into one of two groups: the simulator group or the control group. During a two-week training period, all participants practiced their probe-tube placement according to their randomly assigned group. After two weeks, each participant completed a probe-tube placement on the same volunteer as a posttest scenario.Twenty-five novice graduate-level student clinicians.Participants completed a self-efficacy questionnaire and an expert observer completed a questionnaire evaluating each participant’s performance during the pre- and posttest sessions. RECD measurements were taken after placing the probe tube and foam tip in the volunteer’s ear. Questionnaire results were analyzed through nonparametric t-tests and analysis of variance, whereas RECD results were analyzed using a nonlinear mixed model method.Results suggested students in the simulator group were less likely to contact the tympanic membrane when placing a probe tube, appeared more confident, and had better use of the occluding foam tip, resulting in more improved RECD measurements.The improved outcomes for trainees in the simulator group suggest that supplementing traditional training with the simulator provides useful benefits for the trainees, thereby encouraging its usage and implementation in educational settings.

scholarly journals Reaction rate coefficient k20 and temperature coefficient Θ in organic waste thermal disintegration

2018 ◽  
Vol 23 ◽  
pp. 00026
Author(s):  
Sylwia Myszograj
Keyword(s):  
Activated Sludge ◽  
Mixed Model ◽  
Heating Temperature ◽  
Treatment Plant ◽  
Oxygen Demand ◽  
Rate Of Change ◽  
Waste Activated Sludge ◽  
Nonlinear Mixed Model ◽  
The Difference ◽  
Reaction Speed

It was described the test of sewage sludge and organic fraction of municipal mixed solid waste thermal disintegration process. The waste activated sludge used during the tests was collected from the secondary settlement tank in a mechanical-biological wastewater treatment plant. The biowaste used in the studies was collected from an area of new buildings. It was noticed from means values of Soluble Chemical Oxygen Demand (SCOD) plot that both heating temperature and time, influence the amount of dissolved COD. The observations indicate that changes of SCOD can be described by an increasing, differentiable function of time and the rate of change of the soluble COD in the hydrolysates, in time is proportional to the difference of the maximum values of SCOD and its value in time, which leads to the relationship of the first-order ordinary differential equation. The process effectiveness depending on the temperature was described with the mathematical model including Van't Hoff-Arrhenius equation. Inspection of the data and some preliminary fits indicates, that for the description of changes in SCOD terms of time and temperature were adopted the form of nonlinear mixed model. Values of k20 indicator and Θ parameter depend on the substrate type. For waste activated sludge thermal disintegration, value of reaction speed indicator k20 was 0.028 h-1 (0,67 d-1), and value of temperature indicator equalled Θ = 1.024. For thermal disintegration of biological waste, value of reaction speed indicator k20 was 0.016 h-1 (0,38 d-1), and value of temperature indicator equalled Θ = 1.016.

scholarly journals Comparison of growth curves of two genotypes of dairy goats using nonlinear mixed models

2013 ◽  
Vol 152 (5) ◽  
pp. 829-842 ◽  
Author(s):  
J. G. L. REGADAS FILHO ◽  
L. O. TEDESCHI ◽  
M. T. RODRIGUES ◽  
L. F. BRITO ◽  
T. S. OLIVEIRA
Keyword(s):  
Random Effects ◽  
Growth Curve ◽  
Mixed Model ◽  
Growth Curves ◽  
Growth Patterns ◽  
Dairy Goat ◽  
Residual Variance ◽  
Nonlinear Mixed Model ◽  
Error Structure ◽  
Mixed Model Methodology

SUMMARYThe objective of the current study was to assess the use of nonlinear mixed model methodology to fit the growth curves (weightv.time) of two dairy goat genotypes (Alpine, +A and Saanen, +S). The nonlinear functions evaluated included Brody, Von Bertalanffy, Richards, Logistic and Gompertz. The growth curve adjustment was performed using two steps. First, random effectsu1,u2andu3were linked to the asymptotic body weight (β1), constant of integration (β2) and rate constant of growth (β3) parameters, respectively. In addition to a traditional fixed-effects model, four combinations of models were evaluated using random variables: all parameters associated with random effects (u1,u2andu3), onlyβ1andβ2(u1andu2), onlyβ1andβ3(u1andu3) and onlyβ1(u1). Second, the fit of the best adjusted model was refined by using the power variance and modelling the error structure. Residual variance ($\sigma _e^2 $) and the Akaike information criterion were used to evaluate the models. After the best fitting model was chosen, the genotype curve parameters were compared. The residual variance was reduced in all scenarios for which random effects were considered. The Richards (u1andu3) function had the best fit to the data. This model was reparameterized using two isotropic error structures for unequally spaced data, and the structure known in the literature as SP(MATERN) proved to be a better fit. The growth curve parameters differed between the two genotypes, with the exception of the constant that determines the proportion of the final size at which the inflection point occurs (β4). The nonlinear mixed model methodology is an efficient tool for evaluating growth curve features, and it is advisable to assign biologically significant parameters with random effects. Moreover, evaluating error structure modelling is recommended to account for possible correlated errors that may be present even when using random effects. Different Richard growth curve parameters should be used for the predominantly Alpine and Saanen genotypes because there are differences in their growth patterns.

Individual differences in adjustment to spousal loss: A nonlinear mixed model analysis

2007 ◽  
Vol 31 (4) ◽  
pp. 405-415 ◽  
Author(s):  
Christopher T. Burke ◽  
Patrick E. Shrout ◽  
Niall Bolger
Keyword(s):  
Individual Differences ◽  
Mixed Model ◽  
Multilevel Models ◽  
Broad Class ◽  
Regulatory System ◽  
Well Being ◽  
Model Analysis ◽  
Adjustment Process ◽  
Nonlinear Mixed Model ◽  
Mixed Model Analysis

The study of within-person change lies at the core of developmental research. Theory and empirical data suggest that many of these developmental processes are not linear. We describe a broad class of multilevel models that allows for nonlinear change — nonlinear mixed models. To demonstrate the utility of these models, we present a nonlinear mixed model analysis of adjustment to conjugal loss. Coming from a perspective of the individual as a regulatory system, our model predicts a faster rate of adjustment immediately following the loss and diminished adjustment as time since the loss increases, approaching an equilibrium level of well-being. This model allows us to estimate various aspects of the adjustment trajectory and individual differences in these trajectories, including multiple ways that pre- and post-loss factors can explain variability in the adjustment process. The model provides new insights into an important phenomenon that cannot be gleaned from linear models and other methods of trajectory analysis. We discuss the strengths and limitations of this type of analysis relative to other methods.

scholarly journals Update on the College of American Pathologists Experience With High-Risk Human Papillomavirus Proficiency Testing for Cytology

2016 ◽  
Vol 140 (12) ◽  
pp. 1371-1374 ◽  
Author(s):  
Mohiedean Ghofrani ◽  
Chengquan Zhao ◽  
Diane D. Davey ◽  
Fang Fan ◽  
Mujtaba Husain ◽  
...  
Keyword(s):  
Human Papillomavirus ◽  
Proficiency Testing ◽  
Mixed Model ◽  
Clinical Laboratory ◽  
Becton Dickinson ◽  
Nonlinear Mixed Model ◽  
Molecular Systems ◽  
Hybrid Capture 2 ◽  
Testing Medium ◽  
Commercial Kits

Context.— Since 2008, the College of American Pathologists has provided the human papillomavirus for cytology laboratories (CHPV) proficiency testing program to help laboratories meet the requirements of the Clinical Laboratory Improvement Amendments of 1988. Objectives.— To provide an update on trends in proficiency testing performance in the College of American Pathologists CHPV program during the 4-year period from 2011 through 2014 and to compare those trends with the preceding first 3 years of the program. Design.— Responses of laboratories participating in the CHPV program from 2011 through 2014 were analyzed using a nonlinear mixed model to compare different combinations of testing medium and platform. Results.— In total, 818 laboratories participated in the CHPV program at least once during the 4 years, with participation increasing during the study period. Concordance of participant responses with the target result was more than 98% (38 280 of 38 892). Overall performance with all 3 testing media—ThinPrep (Hologic, Bedford, Massachusetts), SurePath (Becton, Dickinson and Company, Franklin Lakes, New Jersey), or Digene (Qiagen, Valencia, California)—was equivalent (P = .51), and all 4 US Food and Drug Administration (FDA)–approved platforms—Hybrid Capture 2 (Qiagen), Cervista (Hologic), Aptima (Hologic), and cobas (Roche Molecular Systems, Pleasanton, California)—outperformed laboratory-developed tests, unspecified commercial kits, and other (noncommercial) methods in ThinPrep medium (P < .001). However, certain off-label combinations of platform and medium, most notably Cervista with SurePath, demonstrated suboptimal performance (P < .001). Conclusions.— Laboratories demonstrated proficiency in using various combinations of testing media and platforms offered in the CHPV program, with statistically significant performance differences in certain combinations. These observations may be relevant in the current discussions about FDA oversight of laboratory-developed tests.

Application of the First Order Generalized-α Method to the Solution of an Intrinsic Geometrically Exact Model of Rotor Blade Systems

2008 ◽  
Vol 4 (1) ◽  
Author(s):  
F. Khouli ◽  
F. F. Afagh ◽  
R. G. Langlois
Keyword(s):  
Rotor Blade ◽  
Mixed Model ◽  
Transient Behavior ◽  
Mathematical Structure ◽  
Weak Form ◽  
Integration Scheme ◽  
State Variables ◽  
Nonlinear Mixed Model ◽  
First Order ◽  
Blade System

An energy decaying integration scheme for an intrinsic, geometrically exact, multibody dynamics model with composite, dimensionally reducible, active beamlike structures is proposed. The scheme is based on the first order generalized-α method that was proposed and successfully applied to various nonlinear dynamics models. The similarities and the differences between the mathematical structure of the nonlinear intrinsic model and a parallel nonlinear mixed model of chains are highlighted to demonstrate the effect of the form of the governing equation on the stability of the integration scheme. Simple C° shape functions are used in the spatial discretization of the state variables owing to the weak form of the model. Numerical solution of the transient behavior of multibody systems, representative of various rotor blade system configurations, is presented to highlight the advantages and the drawbacks of the integration scheme. Simulation predictions are compared against experimental results whenever the latter is available to verify the implementation. The suitability and the robustness of the proposed integration scheme are then established based on satisfying two conservational laws derived from the intrinsic model, which demonstrate the retained energy decaying characteristic of the scheme and its unconditional stability when applied to the intrinsic nonlinear problem, and the dependance of its success on the form of the governing equations.

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