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Model Uses (model + use)
Selected AbstractsA critical review of appropriate conceptual models for use by coronary care nursesINTERNATIONAL NURSING REVIEW, Issue 1 2008F. Timmins bns ffnrcsi nfesc rnt rgn phd msc bsc Background:, There is little evidence of the extent of conceptual model use within cardiovascular nursing. Concern exists within nursing that nursing theory and conceptual model use within practice is less than optimal. It is further suggested that there is little evidence of nursing theory occupying its true position as the central tenet of nursing practice and cardiovascular nurses have been challenged to reconsider this aspect of practice. Aim:, The aim of this review is to explore the effectiveness of conceptual models used within cardiovascular nursing to further explore their potential benefit. Methods:, Using key terms, a search was conducted using electronic databases CINAHL and PUBMED; yielding seven papers that fulfilled selection criteria. Findings:, Few papers related to research studies in the area. However, of those identified significant examination and testing of concepts emerged within the studies. Rather than merely using concepts as an organizing framework or a component of the study, theories alluded to were scrutinized and consistently applied. Although studies identified mostly referred to specific testing and examination of aspects of conceptual models, the notion of self-care and support for clients emerges as a strong theme within the review. The relationship between nurse and client seemed to be pivotal in any noted improvements. Conclusions:, The findings have limited application to practice. In the absence of large-scale longitudinal studies, only selected aspects of conceptual models or theory were scrutinized. Further research is required in this area to identify conceptual models of nursing that are most appropriate for cardiovascular nursing care. [source] Market response models and marketing practiceAPPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 4-5 2005Dominique M. Hanssens Abstract Market response models are intended to help scholars and managers understand how consumers individually and collectively respond to marketing activities, and how competitors interact. Appropriately estimated effects constitute a basis for improved decision making in marketing. We review the demand and supply of market response models and we highlight areas of future growth. We discuss two characteristics that favour model use in practice, viz. the supply of standardized models and the availability of empirical generalizations. Marketing as a discipline and market response models as a technology may often not receive top management attention. In order to have enhanced relevance for senior management, we argue that marketing models should be cross-functional, include short- and long-term effects, and be considerate of capital markets. We also identify emerging opportunities for marketing model applications in areas such as public policy and litigation. Copyright © 2005 John Wiley & Sons, Ltd. [source] Probabilistic Neural Network for Reliability Assessment of Oil and Gas PipelinesCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2002Sunil K. Sinha A fuzzy artificial neural network (ANN),based approach is proposed for reliability assessment of oil and gas pipelines. The proposed ANN model is trained with field observation data collected using magnetic flux leakage (MFL) tools to characterize the actual condition of aging pipelines vulnerable to metal loss corrosion. The objective of this paper is to develop a simulation-based probabilistic neural network model to estimate the probability of failure of aging pipelines vulnerable to corrosion. The approach is to transform a simulation-based probabilistic analysis framework to estimate the pipeline reliability into an adaptable connectionist representation, using supervised training to initialize the weights so that the adaptable neural network predicts the probability of failure for oil and gas pipelines. This ANN model uses eight pipe parameters as input variables. The output variable is the probability of failure. The proposed method is generic, and it can be applied to several decision problems related with the maintenance of aging engineering systems. [source] A new biodegradation prediction model specific to petroleum hydrocarbonsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2005Philip Howard Abstract A new predictive model for determining quantitative primary biodegradation half-lives of individual petroleum hydrocarbons has been developed. This model uses a fragment-based approach similar to that of several other biodegradation models, such as those within the Biodegradation Probability Program (BIOWIN) estimation program. In the present study, a half-life in days is estimated using multiple linear regression against counts of 31 distinct molecular fragments. The model was developed using a data set consisting of 175 compounds with environmentally relevant experimental data that was divided into training and validation sets. The original fragments from the Ministry of International Trade and Industry BIOWIN model were used initially as structural descriptors and additional fragments were then added to better describe the ring systems found in petroleum hydrocarbons and to adjust for nonlinearity within the experimental data. The training and validation sets had r2 values of 0.91 and 0.81, respectively. [source] A porous-matrix sensor to measure the matric potential of soil water in the fieldEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2007W. R. Whalley Summary The matric potential of soil water is probably the most useful assessment of soil water status. However, the water-filled tensiometer (the benchmark instrument for measuring matric potential) typically only operates in the range 0 to ,85 kPa. In this paper, we report the development of a porous-matrix sensor to measure matric potential in the approximate range ,50 to ,300 kPa. The sensor uses a dielectric probe to measure the water content of a ceramic material with known water retention characteristics. The calculation of matric potential takes into account hysteresis through the application of an appropriate model to measured wetting and drying loops. It is important that this model uses closed, rather than open, scanning loops. The calibrated sensors were tested in the field and the output compared with data from water-filled tensiometers and dielectric measurements of soil water content. These comparisons indicated that conventional tensiometers gave stable but false readings of matric potential when soil dried to matric potentials more negative than ,80 kPa. The porous-matrix sensors appeared to give reliable readings of matric potential in soil down to ,300 kPa and also responded appropriately to repeated wetting and drying. This porous-matrix sensor has considerable potential to help understand plant responses to drying soil. [source] A 3-D non-hydrostatic pressure model for small amplitude free surface flowsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2006J. W. Lee Abstract A three-dimensional, non-hydrostatic pressure, numerical model with k,, equations for small amplitude free surface flows is presented. By decomposing the pressure into hydrostatic and non-hydrostatic parts, the numerical model uses an integrated time step with two fractional steps. In the first fractional step the momentum equations are solved without the non-hydrostatic pressure term, using Newton's method in conjunction with the generalized minimal residual (GMRES) method so that most terms can be solved implicitly. This method only needs the product of a Jacobian matrix and a vector rather than the Jacobian matrix itself, limiting the amount of storage and significantly decreasing the overall computational time required. In the second step the pressure,Poisson equation is solved iteratively with a preconditioned linear GMRES method. It is shown that preconditioning reduces the central processing unit (CPU) time dramatically. In order to prevent pressure oscillations which may arise in collocated grid arrangements, transformed velocities are defined at cell faces by interpolating velocities at grid nodes. After the new pressure field is obtained, the intermediate velocities, which are calculated from the previous fractional step, are updated. The newly developed model is verified against analytical solutions, published results, and experimental data, with excellent agreement. Copyright © 2005 John Wiley & Sons, Ltd. [source] A Global Model for Forecasting Political InstabilityAMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 1 2010Jack A. Goldstone Examining onsets of political instability in countries worldwide from 1955 to 2003, we develop a model that distinguishes countries that experienced instability from those that remained stable with a two-year lead time and over 80% accuracy. Intriguingly, the model uses few variables and a simple specification. The model is accurate in forecasting the onsets of both violent civil wars and nonviolent democratic reversals, suggesting common factors in both types of change. Whereas regime type is typically measured using linear or binary indicators of democracy/autocracy derived from the 21-point Polity scale, the model uses a nonlinear five-category measure of regime type based on the Polity components. This new measure of regime type emerges as the most powerful predictor of instability onsets, leading us to conclude that political institutions, properly specified, and not economic conditions, demography, or geography, are the most important predictors of the onset of political instability. [source] Assimilation of radar-derived rain rates into the convective-scale model COSMO-DE at DWDTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 634 2008K. Stephan Abstract To improve very-short-range forecasts particularly in convective situations, a version of the COSMO-Model (formerly known as LM) which simulates deep convection explicitly (horizontal grid length: 2.8 km) has been developed and is now run operationally at DWD. This model uses a prognostic type of precipitation scheme accounting for the horizontal drift of falling hydrometeors. To initialise convective-scale events, the latent heat nudging (LHN) approach has been adopted for the assimilation of surface precipitation rates derived from radar reflectivity data. It is found that a conventional LHN scheme designed for larger-scale models with diagnostic treatment of precipitation does not perform well and leads to strong overestimation of precipitation when applied to the convective-scale model with a prognostic treatment of precipitation. As illustrated here, surface precipitation and vertically integrated latent heating are far less correlated horizontally and temporally in such a model than with diagnostic precipitation, and this implies a violation of the basic assumption of LHN. Several revisions to the LHN scheme have therefore been developed in view of the characteristic model behaviour so as to re-enhance the validity of the basic assumption and to reduce greatly the overestimation of precipitation during assimilation. With the revised scheme, the model is able to simulate the precipitation patterns in good agreement with radar observations during the assimilation and the first hours of the forecast. The scheme also has a positive impact on screen-level parameters and on the longer-term climatology of the model. Extending the temporal impact of the radar observations further into the free forecast will be the focus of future research. Copyright © 2008 Royal Meteorological Society [source] Turbulent stresses as a function of shear rate in a local disk modelASTRONOMISCHE NACHRICHTEN, Issue 1 2009A.J. Liljeström Abstract We present local numerical models of accretion disk turbulence driven by the magnetorotational instability with varying shear rate. The resulting turbulent stresses are compared with predictions of a closure model in which triple correlations are modelled in terms of quadratic correlations. This local model uses five nondimensional parameters to describe the properties of the flow. We attempt to determine these closure parameters for our simulations and find that the model does produce qualitatively correct behaviour. In addition, we present results concerning the shear rate dependency of the magnetic to kinetic energy ratio. We find both the turbulent stress ratio and the total stress to be strongly dependent on the shear rate (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||