In this paper, we propose several algorithms for computing parameterizations of NURBS domains (surfaces and volumes) which are motivated by the recent research in isogeometric analysis. We describe methods for finding parameterizations of planar NURBS domains bounded by either a given closed NURBS curve, or four NURBS curves fulfilling compatibility conditions. Further, parameterizations of NURBS volumes of revolution based on two different parameterizations of a disc are presented. The main result of the paper is the formulation of an algorithm for computing parameterizations of the so-called generalized NURBS volumes of revolution. and Obsahuje seznam literatury
A portable open gas-exchange system (Li-6400, Li-Cor, Inc., Lincoln, NE, USA) has been widely used for the measurement of net gas exchanges and calibration/parameterization of leaf models. Measurement errors due to diffusive leakage rates of water vapor (LW) and CO2 (LC) between inside and outside of the leaf chamber, and the inward dark transpiration rate (DW) and dark respiration rate (DC) released from the leaf under the gasket, can be significant. Rigorous model-based approaches were developed for estimating leakage coefficients of water vapor (KW) and CO2 (KC) and correcting for the combination of these errors. Models were based on mass balance equations and the Dusty Gas Model for a ternary gas mixture of water vapor, CO2, and dry air. Experiments were conducted using two Li-6400 systems with potato and soybean leaves. Results indicated that models were reliable for estimating KW and KC, and the values varied with instrument, chamber size, gasket condition, and leaf structure. A thermally killed leaf should be used for this determination. Measurement error effects on parameterization of the Farquhar et al. (1980) model as determined by PN/C i curves were substantial and each parameter had its own sensitivity to measurement errors. Results also indicated that all four error sources should be accounted for when correcting measurements., Q. Wang ... [et al.]., and Obsahuje bibliografii a dodatky