4 research outputs found
Bounds and phase diagram of efficiency at maximum power for tight-coupling molecular motors
The efficiency at maximum power (EMP) for tight-coupling molecular motors is
investigated within the framework of irreversible thermodynamics. It is found
that the EMP depends merely on the constitutive relation between the
thermodynamic current and force. The motors are classified into four generic
types (linear, superlinear, sublinear, and mixed types) according to the
characteristics of the constitutive relation, and then the corresponding ranges
of the EMP for these four types of molecular motors are obtained. The exact
bounds of the EMP are derived and expressed as the explicit functions of the
free energy released by the fuel in each motor step. A phase diagram is
constructed which clearly shows how the region where the parameters (the load
distribution factor and the free energy released by the fuel in each motor
step) are located can determine whether the value of the EMP is larger or
smaller than 1/2. This phase diagram reveals that motors using ATP as fuel
under physiological conditions can work at maximum power with higher efficiency
() for a small load distribution factor ().Comment: 5 pages, 4 figure
Model confidence sets and forecast combination: an application to age-specific mortality
Background: Model averaging combines forecasts obtained from a range of models, and it often produces more accurate forecasts than a forecast from a single model.
Objective: The crucial part of forecast accuracy improvement in using the model averaging lies in the determination of optimal weights from a finite sample. If the weights are selected sub-optimally, this can affect the accuracy of the model-averaged forecasts. Instead of choosing the optimal weights, we consider trimming a set of models before equally averaging forecasts from the selected superior models. Motivated by Hansen et al. (2011), we apply and evaluate the model confidence set procedure when combining mortality forecasts.
Data & Methods: The proposed model averaging procedure is motivated by Samuels and Sekkel (2017) based on the concept of model confidence sets as proposed by Hansen et al. (2011) that incorporates the statistical significance of the forecasting performance. As the model confidence level increases, the set of superior models generally decreases. The proposed model averaging procedure is demonstrated via national and sub-national Japanese mortality for retirement ages between 60 and 100+.
Results: Illustrated by national and sub-national Japanese mortality for ages between 60 and 100+, the proposed model-average procedure gives the smallest interval forecast errors, especially for males. Conclusion: We find that robust out-of-sample point and interval forecasts may be obtained from the trimming method. By robust, we mean robustness against model misspecification