A modified von Bertalanffy growth model dependent on temperature and body size.

Fish growth models are widely used in fisheries as well in aquacultures and ecology. Water temperature is one of the most important factors determining the growth of fish. In the present study, we propose a growth model that includes the effect of water temperature on the growth in the von Bertalanffy growth model. Our model was applied to fit the growth data of bullhead (Cottus gobio), brown trout (Salmo trutta L.), juvenile salmon (Salmo salar), and Araucanian herring (Strangomera bentincki). The model reproduces the growth patterns of each species and fits a set of appropriate parameter values for each species. Moreover, the model reflects the seasonal growth rates quite well.

A fractional-order model for MINMOD Millennium.

MINMOD Millennium has been widely used to estimate insulin sensitivity (SI) in glucose-insulin dynamics. In order to explain the rheological behavior of glucose-insulin we attempt to modify MINMOD Millennium with fractional-order differentiation of order α ∈ (0, 1]. We show that the new modified model has non-negative, bounded solutions and a stable equilibrium point. Quasi-optimal fractional orders and parameters are estimated by using a nonlinear weighted least-squares method, the Levenberg-Marquardt algorithm, and the fractional Adams-Bashforth-Moulton method for several subjects (normal subjects and type 2 diabetic patients). The numerical results confirm that SI is significantly lower in diabetics than in non-diabetics. In addition, we explain the new factor (τ(1 - α)) determining glucose tolerance and the relation between SI and τ(1 - α).

An efficient ray tracing algorithm for the simulation of light trapping effects in Si solar cells with textured surfaces.

Optimizing the design of the surface texture is an essential aspect of Si solar cell technology as it can maximize the light trapping efficiency of the cells. The proper simulation tools can provide efficient means of designing and analyzing the effects of the texture patterns on light confinement in an active medium. In this work, a newly devised algorithm termed Slab-Outline, based on a ray tracing technique, is reported. The details of the intersection searching logic adopted in Slab-Outline algorithm are also discussed. The efficiency of the logic was tested by comparing the computing time between the current algorithm and the Constructive Solid Geometry algorithm, and its superiority in computing speed was proved. The validity of the new algorithm was verified by comparing the simulated reflectance spectra with the measured spectra from a textured Si surface.

A hybrid numerical method to compute erythrocyte TMP in low-frequency electric fields.

This paper presents a coupling method of the finite element method and the boundary element method to compute the transmembrane potential (TMP) of an erythrocyte in a low-frequency electric field. We compute an in vitro erythrocyte's TMP induced by external electric fields by this hybrid method. It takes advantage of the homogeneous characteristics from both intracellular region and extracellular region. Moreover, we may use a fine three-dimensional (3-D) mesh around the thin membrane and avoid 3-D meshes in other regions. Numerical results of a spherical cell show that the hybrid method is accurate. The computed threshold of the applied electric field for membrane electric breakdown agrees well with those experimental results. Numerical results can also guide us to locate the maximum induced TMP on the erythrocyte membrane in various electric fields. Some further applications of the hybrid method are also discussed.