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Dynamic Approach (dynamic + approach)
Selected AbstractsTHE EFFECTS OF ITQ IMPLEMENTATION: A DYNAMIC APPROACHNATURAL RESOURCE MODELING, Issue 4 2000LEE G. ANDERSON ABSTRACT. This paper investigates the intertemporal effects of introducing Individual Transferable Quota, ITQ, fishery management programs on stock size, fleet size and composition, and returns to quota holders and to vessel operators. Theoretical analysis is conducted using a specific version of a general dynamic model of a regulated fishery. It is demonstrated that the effects will differ depending upon the prevailing regulation program, current stock size, and existing fleet size, composition and mobility and upon how the stock and fleet change over time after the switch to ITQs. The paper expands upon previous works by modeling the dynamics of change in fleet and stock size and by allowing for changes in the TAC as stock size changes, by comparing ITQs to different regulations, and by allowing the status quo before ITQ implementation to be something other than a bioeconomic equilibrium. Specific cases are analyzed using a simulation model. The analysis shows that the annual return per unit harvest to quota owners can increase or decrease over the transition period due to counteracting effects of changes in stock and fleet size. With ITQs denominated as a percentage of the TAC, the current annual value of a quota share depends upon the annual return per unit of harvest and the annual amount of harvest rights. Because the per unit value can increase or decrease over time, it is also possible that the total value can do the same. Distribution effects are also studied and it is shown that while the gains from quota share received are the present value of a potentially infinite stream of returns, potential losses are the present value of a finite stream, the length of which depends upon the remaining life of the vessel and the expected time it will continue to operate. [source] Dynamic analyte introduction and focusing in plastic microfluidic devices for proteomic analysisELECTROPHORESIS, Issue 1-2 2003Yan Li Abstract Isoelectric focusing (IEF) separations, in general, involve the use of the entire channel filled with a solution mixture containing protein/peptide analytes and carrier ampholytes for the creation of a pH gradient. Thus, the preparative capabilities of IEF are inherently greater than most microfluidics-based electrokinetic separation techniques. To further increase sample loading and therefore the concentrations of focused analytes, a dynamic approach, which is based on electrokinetic injection of proteins/peptides from solution reservoirs, is demonstrated in this study. The proteins/peptides continuously migrate into the plastic microchannel and encounter a pH gradient established by carrier ampholytes originally present in the channel for focusing and separation. Dynamic sample introduction and analyte focusing in plastic microfluidic devices can be directly controlled by various electrokinetic conditions, including the injection time and the applied electric field strength. Differences in the sample loading are contributed by electrokinetic injection bias and are affected by the individual analyte's electrophoretic mobility. Under the influence of 30 min electrokinetic injection at constant electric field strength of 500 V/cm, the sample loading is enhanced by approximately 10,100 fold in comparison with conventional IEF. [source] Estimating annual N2O emissions from agricultural soils in temperate climatesGLOBAL CHANGE BIOLOGY, Issue 10 2005Caroline Roelandt Abstract The Kyoto protocol requires countries to provide national inventories for a list of greenhouse gases including N2O. A standard methodology proposed by the Intergovernmental Panel on Climate Change (IPCC) estimates direct N2O emissions from soils as a constant fraction (1.25%) of the nitrogen input. This approach is insensitive to environmental variability. A more dynamic approach is needed to establish reliable N2O emission inventories and to propose efficient mitigation strategies. The objective of this paper is to develop a model that allows the spatial and temporal variation in environmental conditions to be taken into account in national inventories of direct N2O emissions. Observed annual N2O emission rates are used to establish statistical relationships between N2O emissions, seasonal climate and nitrogen-fertilization rate. Two empirical models, MCROPS and MGRASS, were developed for croplands and grasslands. Validated with an independent data set, MCROPS shows that spring temperature and summer precipitation explain 35% of the variance in annual N2O emissions from croplands. In MGRASS, nitrogen-fertilization rate and winter temperature explain 48% of the variance in annual N2O emissions from grasslands. Using long-term climate observations (1900,2000), the sensitivity of the models with climate variability is estimated by comparing the year-to-year prediction of the model to the precision obtained during the validation process. MCROPS is able to capture interannual variability of N2O emissions from croplands. However, grassland emissions show very small interannual variations, which are too small to be detectable by MGRASS. MCROPS and MGRASS improve the statistical reliability of direct N2O emissions compared with the IPCC default methodology. Furthermore, the models can be used to estimate the effects of interannual variation in climate, climate change on direct N2O emissions from soils at the regional scale. [source] Urban Polycentricity and the Costs of Commuting: Evidence from Italian Metropolitan AreasGROWTH AND CHANGE, Issue 3 2010PAOLO VENERI ABSTRACT Polycentricity at the metropolitan scale is perhaps the model of spatial organisation that needs to be investigated more thoroughly as regards its effects on travel. The aim of this paper is to test the role of polycentricity,as well as other spatial characteristics, such as compactness, functional diversification and size,in the costs of commuting, taking into account an external cost component (per-capita CO2 emissions) and a private cost component (time spent on travelling). The degree of urban polycentricity has been measured by adopting a dynamic approach based on commuting flows and on social network analysis tools. The analysis is carried out using a database of 82 Italian metropolitan areas (MAs). Results show that MAs with a higher degree of polycentricity are more virtuous both in terms of private and external costs of mobility, while the degree of compactness is associated with lower environmental costs but with higher private costs. Size is associated with both higher external and private costs, while the role of functional diversification turns out to be statistically insignificant. Socio-demographics also play a role. [source] A dynamic approach for evaluating parameters in a numerical methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2005A. A. Oberai Abstract A new methodology for evaluating unknown parameters in a numerical method for solving a partial differential equation is developed. The main result is the identification of a functional form for the parameters which is derived by requiring the numerical method to yield ,optimal' solutions over a set of finite-dimensional function spaces. The functional depends upon the numerical solution, the forcing function, the set of function spaces, and the definition of the optimal solution. It does not require exact or approximate analytical solutions of the continuous problem, and is derived from an extension of the variational Germano identity. This methodology is applied to the one-dimensional, linear advection,diffusion problem to yield a non-linear dynamic diffusivity method. It is found that this method yields results that are commensurate to the SUPG method. The same methodology is then used to evaluate the Smagorinsky eddy viscosity for the large eddy simulation of the decay of homogeneous isotropic turbulence in three dimensions. In this case the resulting method is found to be more accurate than the constant-coefficient and the traditional dynamic versions of the Smagorinsky model. Copyright © 2004 John Wiley & Sons, Ltd. [source] Modelling the growth of Weissella cibaria as a function of fermentation conditionsJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2009A. Ricciardi Abstract Aims:, To investigate the effect of pH, water activity (aw) and temperature on the growth of Weissella cibaria DBPZ1006, a lactic acid bacterium isolated from sourdoughs. Methods and Results:, The kinetics of growth of W. cibaria DBPZ1006 was investigated during batch fermentations as a function of pH (4·0,8·0), aw (0·935,0·994) and temperature (10,45°C) in a rich medium. The growth curve parameters (lag time, growth rate and asymptote) were estimated using the dynamic model of Baranyi and Roberts (1994. A dynamic approach to predicting bacterial growth in food. Int J Food Microbiol23, 277,294). The effect of pH, aw and temperature on maximum specific growth rate (,max) were estimated by fitting a cardinal model. ,max under optimal conditions (pH = 6·6, aw = 0·994, T = 36·3°C) was estimated to be 0·93 h,1. Minimum and maximum estimated pH and temperature for growth were 3·6 and 8·15, and 9·0°C and 47·8°C, respectively, while minimum aw was 0·918 (equivalent to 12·2% w/v NaCl). Conclusions:,Weissella cibaria DBPZ1006 is a fast-growing heterofermentative strain, which could be used in a mixed starter culture for making bread. Significance and Impact of the Study:, This is the first study reporting the modelling of the growth of W. cibaria, a species that is increasingly being used as a starter in sourdough and vegetable fermentations. [source] Crisis Management in France: Trends, Shifts and PerspectivesJOURNAL OF CONTINGENCIES AND CRISIS MANAGEMENT, Issue 4 2002Patrick Lagadec The object of this article is to give an idea of crisis management in France. I will look at two principal axes: firstly, a simplified outline of the system as it has evolved over the years and with regard to the major changes it is undergoing today; secondly, an overview of the efforts recently made by the most progressive actors in the field. Traditionally, all analyses of this type have concentrated on the French exception, that is, a centralised country answering to a strong state, largely influenced by past references, doctrines, hierarchical rules, and technical dispositions. Although this image is still very accurate in many respects, France has been progressively losing its ,classicism'. This has come about as a result, first and foremost, of the growing number of crises which contradict the logic of long,standing references. Uncertainties, multiplicity of actors, masses of information, major surprises, cross,over events and abrupt changes are but some of the elements which are increasingly difficult to absorb within pre,established historical models. With the profusion of new actors and networks of people unaware of former royal or Napoleonic regulations, the cards are largely being dealt between the public and the private, the central and the local, the national and the international, and so on. Transformation is continuously occurring by the accumulation of new laws (e.g. decentralisation) or specific adjustments (e.g. critical infrastructures). International markets and new information technologies also play a key role in this transformation. But perhaps the most powerful motor for change are crises. More often than not, crises lead to a loss of faith in yet unquestioned references, with regard to legitimacy, credibility and responsibility. France offers a highly contrasted scene as a country still resisting inevitable change. Although there is growing disorder, new opportunities are arising. Wishing to take a dynamic approach to these questions rather than a descriptive one, I have sought to distinguish the main themes and their interactions. I will particularly look at: problems raised by new crises in complex societies; the means necessary for ensuring progress (Boin; Lagadec 2000); resistance to these measures; and, finally, some of the most promising initiatives. The vocation of the European Crisis Management Academy is to share past experience as well as questions and answers in an area of great instability and critical stakes. [source] MONTE CARLO SIMULATION OF FAR INFRARED RADIATION HEAT TRANSFER: THEORETICAL APPROACHJOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2006F. TANAKA ABSTRACT We developed radiation heat transfer models with the combination of the Monte Carlo (MC) method and computational fluid dynamic approach and two-dimensional heat transfer models based on the fundamental quantum physics of radiation and fluid dynamics. We investigated far infrared radiation (FIR) heating in laminar and buoyancy airflow. A simple prediction model in laminar airflow was tested with an analytical solution and commercial software (CFX 4). The adequate number of photon tracks for MC simulation was established. As for the complex designs model, the predicted results agreed well with the experimental data with root mean square error of 3.8 K. Because food safety public concerns are increasing, we applied this model to the prediction of the thermal inactivation level by coupling with the microbial kinetics model. Under buoyancy airflow condition, uniformity of FIR heating was improved by selecting adequate wall temperature and emissivity. [source] Pension Valuation Under Uncertainties: Implementation of a Stochastic and Dynamic Monitoring SystemJOURNAL OF RISK AND INSURANCE, Issue 2 2002Shih-Chieh Chang Financial soundness and funding stability are two critical issues in pension fund management. First, we construct a generalized stochastic model to monitor the solvency risk and cash flow dynamics of the defined benefit pension plan. A semi-Markov process proposed by Dominicis et al. (1991) and Janssen and Manca (1997) is employed in structuring the transition pattern of the plan's population, and the economic-based factors are generated through plausible stochastic processes. Modifications according to classification and movements of the plan member and the plan's turnover pattern are also employed to improve its practical usefulness. Then the actuarial valuations, cash flow analyses, and workforce projection are performed and investigated. Second, we explicitly formulate the plan dynamics and implement the proposed mechanism into a risk management framework for pension management. By employing the stochastic and dynamic approach, the cost factors can be monitored throughout the valuation process. Third, we outline the procedure of implementing the proposed methodology into a monitoring system. Finally, the Taiwan Public Employees Retirement System is simplified to illustrate techniques in achieving risk management goals. [source] The economics of land-use regulation in the presence of an externality: a dynamic approachOPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 1 2007Renan U. Goetz Abstract Land-use restrictions are frequently applied to separate non-polluting from polluting activities. In contrast to the existing literature, we simultaneously incorporate spatial and intertemporal aspects of the problem and endogenously determine the border of the zones. Intensity-orientated instruments alone, such as a spatially differentiated tax on inputs or outputs, are not able to support the socially optimal outcome and need to be complemented by instruments that affect choices at the extensive margin such as positive or negative land-use taxes or land zoning. The necessary changes required to transform a spatially optimal, yet static, environmental policy into an intertemporally and spatially optimal environmental policy are presented and discussed. Copyright © 2006 John Wiley & Sons, Ltd. [source] Carotenoids in evolutionary ecology: re-evaluating the antioxidant roleBIOESSAYS, Issue 10 2009Lorenzo Pérez-Rodríguez Abstract The antioxidant role of carotenoids in the living organism was proposed as a possible basis for the honesty of carotenoid-based signals. However, recent studies have questioned the relevance of carotenoids as powerful antioxidants in vivo. Current evidence does not seem to support the "antioxidant role" hypothesis, but it does not allow us to reject it either. This paper proposes some steps to solve this controversy, such as taking a dynamic approach to antioxidant responses, designing protocols that expose individuals to oxidative challenges, analyzing tissues other than blood, and obtaining measures of antioxidant capacity and oxidative damage simultaneously. However, it should be considered that, irrespective of their antioxidant potential, carotenoids might still give information on oxidative stress levels if they are particularly sensitive to free radicals. Finally, lumping together the immunostimulatory and antioxidant roles of carotenoids should be avoided as these functions are not necessarily associated. [source] Growth rules based on the modularity of the Canarian Aeoniwm (Crassulaceae) and their phylogenetic valueBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2000TOVE H. JORGENSEN Growth forms of 22 species of Aeonium (Crassulaceae) were quantified. Since all species are simple in their modular construction, models were developed to predict module length, branching mode and flowering probability using linear and logistic regression. When combined, the parameters of these models are species specific. A discriminant analysis generates a statistically significant separation of species at the level of phylogenetic sections. The results therefore demonstrate the phylogenetic value of growth rules in plants. This dynamic approach strongly contrasts with the traditional static view on forms in systematics and morphology. It also leaves scope for predicting the evolutionary pathways of morphological change which have caused the great diversity of growth forms in the genus Aeonium. [source] Conditional OLS minimum variance hedge ratiosTHE JOURNAL OF FUTURES MARKETS, Issue 10 2004Joëlle Miffre The paper presents a new methodology to estimate time dependent minimum variance hedge ratios. The so-called conditional OLS hedge ratio modifies the static OLS approach to incorporate conditioning information. The ability of the conditional OLS hedge ratio to minimize the risk of a hedged portfolio is compared to conventional static and dynamic approaches, such as the naďve hedge, the roll-over OLS hedge, and the bivariate GARCH(1,1) model. The paper concludes that, both in-sample and out-of-sample, the conditional OLS hedge ratio reduces the basis risk of an equity portfolio better than the alternatives conventionally used in risk management. © 2004 Wiley Periodicals, Inc. Jrl Fut Mark 24:945,964, 2004 [source] What Do We Know About Long,run Equilibrium Real Exchange Rates?AUSTRALIAN ECONOMIC PAPERS, Issue 4 2002PPPs vs Macroeconomic Approaches Despite the fact that the presence of non tradable goods is one of the most frequently advanced reasons for the failure of PPP, the empirical analysis conducted in this paper shows that it explains only a very small portion of the long run behaviour of real exchange rates (RERs) in developed countries: in most cases, there appears to be a very strong long run relationship between RERs calculated on price indexes for tradables and non tradables. As a consequence, deviations from PPP usually appear to be as large for both kinds of goods. To a certain extent, this stylised fact is also verified in the case of the yen/dollar RER, yet formerly known as a typical illustration of the so,called Balassa,Samuelson effect. In this context, so,called macroeconomic approaches of ERERs may be viewed as an alternative to all versions of PPP. We develop a model which combines the contributions of the most fruitful dynamic approaches, namely the NATREX and the BEER. An estimate of this model shows that the main long run determinants of the dollar/euro RER are the rate of consumption and the level of technical progress of the euro area relative to the US. [source] | ||||||||||||||||