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Full-Text Articles in Physical Sciences and Mathematics
Comparing Correlated Parameter Estimates For Nonlinear Pet Model, J. Wu, A. Parkhurst, K. Eskridge, D. Travnicek, T. Brown-Brandi, R. Eigenberg, G. L. Hahn, J. Nienaber, T. Mader, D. Spiers
Comparing Correlated Parameter Estimates For Nonlinear Pet Model, J. Wu, A. Parkhurst, K. Eskridge, D. Travnicek, T. Brown-Brandi, R. Eigenberg, G. L. Hahn, J. Nienaber, T. Mader, D. Spiers
Conference on Applied Statistics in Agriculture
The nonlinear PET model based on Newton's law of cooling can be used to estimate body temperature in cattle, T b challenged by hot cyclic chamber temperatures, T a . The PET model has four biologically meaningful parameters: K, the thermal constant; Δ, the difference between T b and adjusted T a ; Υ the proportion of variation in T b comparable to variation in Ta ; T bini, the initial body temperature. The two parameters Y and Δ are highly correlated in the current version of the model. This study looks at other ways to parameterize …
Using Nonlinear Fixed And Mixed Models To Study Acclimation To Heat Stress In Cattle, L. Lan, A. M. Parkhurst, D. A. Spiers, K. M. Eskridge, G. L. Hahn
Using Nonlinear Fixed And Mixed Models To Study Acclimation To Heat Stress In Cattle, L. Lan, A. M. Parkhurst, D. A. Spiers, K. M. Eskridge, G. L. Hahn
Conference on Applied Statistics in Agriculture
Researchers studying acclimation of cattle to heat stress want to know if exposure to heat stress in controlled chambers will help cattle adjust to climatic conditions in the field. The four parameter nonlinear PET model is used to study the relationship between core body temperature and ambient temperature. This model works well when cattle are challenged by heat stress but the model is less useful for thermoneutral conditions. Both proc Nlin and Nlmixed are used to compare and contrast the field parameters between the controlled and the potentially acclimated group. Simulation studies were used to compare the effectiveness of proc …
Comparison Of Sas Proc Nlin And Nlmixed For Parameter Estimation In Pet Model, Y. Xie, A. M. Parkhurst, T. L. Mader, J. B. Gaughan
Comparison Of Sas Proc Nlin And Nlmixed For Parameter Estimation In Pet Model, Y. Xie, A. M. Parkhurst, T. L. Mader, J. B. Gaughan
Conference on Applied Statistics in Agriculture
Cattle body temperatures were measured under semi-controlled hot cyclic chamber temperatures. The four-parameter nonlinear PET model, is used to estimate body temperature in cattle challenged by heat stress. For each steer, the parameters can be estimated by the Nlin procedure and the sensitivity of each animal can be studied. It is also desirable to generalize the results by using the Nlmixed procedure to combine both the fixed and random effects. When comparing the results from the two procedures, we found heterogeneity among animals and/or days caused convergence problems for proc Nlmixed. Simulation studies were used to study how deviations from …