Search results for "System model"

Global distributions of diazotrophs Gamma-A nifH genes abundance - Depth integrated values computed from a collection of source datasets - Contributi…

2013

The MAREDAT atlas covers 11 types of plankton, ranging in size from bacteria to jellyfish. Together, these plankton groups determine the health and productivity of the global ocean and play a vital role in the global carbon cycle. Working within a uniform and consistent spatial and depth grid (map) of the global ocean, the researchers compiled thousands and tens of thousands of data points to identify regions of plankton abundance and scarcity as well as areas of data abundance and scarcity. At many of the grid points, the MAREDAT team accomplished the difficult conversion from abundance (numbers of organisms) to biomass (carbon mass of organisms). The MAREDAT atlas provides an unprecedente…

Age-related changes in the human visual system and prevalence of refractive conditions in patients attending an eye clinic.

2008

PURPOSE: To retrospectively report the trends of change in several parameters of the human visualsystem over a wide age range in patients attending an eye clinic. SETTING: University of Valencia, Valencia, Spain. METHODS: The clinical records of 2654 patients were retrospectively reviewed, and the age, sex, spherocylindrical refraction, visual acuity, keratometry, and intraocular pressure were obtained. Descriptive values for each parameter and the correlations with age and between different parameters were calculated. Vectorial components of refraction, including blur, were also derived from clinical refractive data and then analyzed. RESULTS: Several parameters changed significantly with …

Discrete-timeH −  ∕ H ∞ sensor fault detection observer design for nonlinear systems with parameter uncertainty

2013

SUMMARY This work concerns robust sensor fault detection observer (SFDO) design for uncertain and disturbed discrete-time Takagi–Sugeno (T–S) systems using H −  ∕ H ∞ criterion. The principle of the proposed approach is based on simultaneously minimizing the perturbation effect and maximizing the fault effect on the residual vector. Furthermore, by introducing slack decision matrices and taking advantage of the descriptor formulation, less conservative sufficient conditions are proposed leading to easier linear matrix inequalities (LMIs). Moreover, the proposed (SFDO) design conditions allow dealing with unmeasurable premise variables. Finally, a numerical example and a truck–trailer system…

Time-Dependent Multiple Depot Vehicle Routing Problem on Megapolis Network under Wardrop's Traffic Flow Assignment

2018

In this work multiple depot vehicle routing problem is considered in case of variable travel times between nodes on a metropolis network. This variant of the classic multiple depot vehicle routing problem is motivated by the fact that in urban contexts variable traffic conditions play an essential role and can not be ignored in order to perform a realistic optimization. Time-travel matrices corresponding to each period of planning horizon were formed by solving the traffic assignment problem in conjunction with shortest path problem. Routing problem instances include from 20 to 100 customers randomly chosen from a road network of Saint-Petersburg. The results demonstrate that taking into ac…

Bayesian calibration of the nitrous oxide emission module of an agro-ecosystem model

2008

1. NitroEurope Open Science Conference on Reactive Nitrogen and the European Greenhouse Gas Balance ; Ghent (Belgique) - (2008-02-20 - 2008-02-21) / Conférence; Nitrous oxide (N2O) is the main biogenic greenhouse gas contributing to the global warming potential (GWP) of agro-ecosystems. Evaluating the impact of agriculture on climate therefore requires a capacity to predict N2O emissions in relation to environmental conditions and crop management. Biophysical models simulating the dynamics of carbon and nitrogen in agro-ecosystems have a unique potential to explore these relationships, but are fraught with high uncertainties in their parameters due to their variations over time and space. H…

MARIOLA: a model for calculating the response of mediterranean bush ecosystem to climatic variations

1995

Abstract The paper summarizes the bush ecosystem model developed for assessing the effects of climatic change on the behaviour of mediterranean bushes assuming that temperature, humidity and rain-fall are the basic dimensions of the niche occupied by shrub species. In this context, changes in the monthly weather pattern serve only to outline the growth conditions due to the nonlinearity of response of shrubs to climatic factors. The plant-soil-atmosphere system is described by means of ordinary non-linear differential equations for the state variables: green biomass, woody biomass, the residues of green and woody biomasses, faecal detritus of mammals on the soil, and the total organic matte…

Study on the transient characteristic in the human visual system using masking experiments

1979

In this paper the visual masking effect is interpreted on the basic of the transient characteristic in two dimensional neuronal networks. The study investigates the suitability of the effect for use as a measurement method. It is shown that the stimulus distribution in space can be scanned at different points in time and that various dynamic characteristic values of the system can be measured.

Technical and economical comparison between different topologies of PV plant under mismatch effect

2014

This paper presents a technical and economical comparative analysis between two topology of photovoltaic plant. In particular the performances of series-parallel (SP) and total cross tied (TCT), topologies are taken into account, referring to a partially shaded photovoltaic plant. Thanks to a simulation model developed, in the paper the mismatch effects due to three different shading conditions, for SP and TCT topology plant, are quantified. Since the TCT solution, even though increase the energy production, raise the complexity of plants as well as their costs, an evaluation of the individual costs of each component of a SP and TCT plant topology, as PV modules, support structure, inverter…

2013

The motion energy sensor has been shown to account for a wide range of physiological and psychophysical results in motion detection and discrimination studies. It has become established as the standard computational model for retinal movement sensing in the human visual system. Adaptation effects have been extensively studied in the psychophysical literature on motion perception, and play a crucial role in theoretical debates, but the current implementation of the energy sensor does not provide directly for modelling adaptation-induced changes in output. We describe an extension of the model to incorporate changes in output due to adaptation. The extended model first computes a space-time r…

A Hybrid Model for an E-learning System Which Develops Metacognitive Skills at Students

2013

One of the goals of academic education is to train students in view of acquiring metacognitive skills, thus becoming self-regulated learners prepared for for lifelong learning. The research in this area has proved that metacognition can be taught and learned and that self-regulation behavior can be guided and constrained by the features of the learning environment. In order to become an educational environment, attractive and at the same time efficient for the students and which would enable students to develop their metacognitive skills, the e-learning system needs continuous improvments. This paper presents a hybrid model of an e-learning system, MEM - Metacognitive E-learning system Mode…