			Home About us Contact

Model Incorporated (model + incorporated)

Distribution by Scientific Domains

Life Sciences	40%

Selected Abstracts

Core loss estimation in three-phase transformer using vector hysteresis model and classical loss model incorporated in 2D magnetodynamics

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 2 2003
O. Deblecker
This paper deals with the computation of the magnetic field and core loss in a three-phase three-limb transformer at no-load. The computational algorithm consists of the vector hysteresis model incorporated in 2D magneto-dynamics via the differential reluctivity tensor. The hysteretic nonlinearity is handled by a simple iteration scheme. The eddy-current losses in the laminated steel core are accounted for by considering an additional conductivity matrix in the FE equations. The magnetisation-dependant vector Preisach model with an analytical expression for the distribution function is adopted for describing the hysteretic constitutive law in the rolling and transverse directions of the laminations. The parameters and mean field term are fitted on the basis of a set of BH-symmetric (quasistatic) loops. Numerical results are presented that confirm the effectiveness of the proposed method for the no-load simulation of the transformer in the transient and the steady-states. [source]

Comparing strategies for controlling an African pest rodent: an empirically based theoretical study

JOURNAL OF APPLIED ECOLOGY, Issue 5 2001
Nils Chr.
Summary 1Small rodents in general and the multimammate rat Mastomys natalensis in particular cause major economic losses in Africa through damage to crops. Attempts to develop dynamic population models for this and other pest rodents are ongoing. 2Demographic estimates from a capture,mark,recapture (CMR) study in Tanzania were used to parameterize a population model for this species. This model incorporated three functional age categories (juveniles, subadults and adults) of both sexes and used density-dependent and density-independent factors, the latter represented by rainfall. 3The model was used to analyse the effect of rodent control on the population dynamics and resulting number of rats. Control measures affecting survival as well as reproduction were considered. 4The model showed that control measures reducing survival will only have long-term effects on population size if they are also applied when rodent densities are low. Control measures applied only when rodent densities are high will not have persistent effects, even at high mortality rates. 5The model demonstrated that control measures reducing reproduction are likely to prevent Mastomys outbreaks, but will keep densities low over a long period only when the contraceptive effect is strong (> 75% reduction). 6Provided that CMR data are available, we recommend developing Leslie-type population models for rodent pests on the basis of CMR-estimated demographic schedules. Such models have great potential in rodent management and allow the evaluation of different strategies. 7Besides improving the ecological basis of the population modelling, economic considerations need to be incorporated into decisions about rodent control. We suggest that appropriate population models will provide important input into such decision making. [source]

The cost-effectiveness of cervical screening in Australia: what is the impact of screening at different intervals or over a different age range?

AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH, Issue 1 2008
Rob Anderson
Abstract Objective: To estimate the cost-effectiveness of altering the currently recommended interval and age range for cervical screening of Australian women. Methods: The cost and effectiveness estimates of alternative screening strategies were generated using an established decision model. This model incorporated a Markov model (of the natural history of cervical cancer and pre-cancerous lesions) and decision trees which: ,mapped' the various pathways to cervical cancer screening; the follow-up of abnormal Pap test results; and the management of confirmed lesions. The model simulated a hypothetical large cohort of Australian women from age 15 to age 85 and calculated the accumulated costs and life-years under each screening strategy. Results: Our model estimated that moving from the current two-yearly screening strategy to annual screening (over the same age range) would cost $379,300 per additional life-year saved. Moving from the current strategy to three-yearly screening would yield $117,100 of savings per life-year lost (costs and effects both discounted at 5% per year), with a relatively modest (<5%) reduction in the total number of life-years saved by the program. Conclusions: Although moving to annual screening would save some additional lives, it is not a cost-effective strategy. Consideration should be given to increasing the recommended interval for cervical screening. However, the net value of any such shift to less effective (e.g. less frequent) and less costly screening strategies will require better evidence about the cost-effectiveness of strategies that encourage non-screeners or irregular screeners to have a Pap test more regularly. [source]

A multikinetic model approach to predict gluconic acid production in an airlift bioreactor

BIOTECHNOLOGY JOURNAL, Issue 5 2007
Mukesh Mayani
Abstract This paper uses a multikinetic approach to predict gluconic acid (GA) production performance in a 4.5 L airlift bioreactor (ALBR). The mathematical model consists of a set of simultaneous firstorder ordinary differential equations obtained from material balances of cell biomass, GA, glucose, and dissolved oxygen. Multikinetic models, namely, logistic and contois equations constitute kinetic part of the main model. The main model also takes into account the hydrodynamic and mass transfer parameters. These equations were solved using ODE solver of MATLAB v6.5 software. The mathematical model was validated with the experimental data available in the literature and is used to predict the effect of change in initial biomass and air sparging rate on the GA production. It is concluded that the mathematical model incorporated with multikinetic approach would be more efficient to predict the change in operating parameters on overall bioprocess of GA production in an ALBR. [source]