Journal articles on the topic 'Modelling options and assumptions'
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1
Broekaert, Jan, Irina Basieva, Pawel Blasiak, and Emmanuel M. Pothos. "Quantum-like dynamics applied to cognition: a consideration of available options." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 375, no. 2106 (October 2, 2017): 20160387. http://dx.doi.org/10.1098/rsta.2016.0387.
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Quantum probability theory (QPT) has provided a novel, rich mathematical framework for cognitive modelling, especially for situations which appear paradoxical from classical perspectives. This work concerns the dynamical aspects of QPT, as relevant to cognitive modelling. We aspire to shed light on how the mind's driving potentials (encoded in Hamiltonian and Lindbladian operators) impact the evolution of a mental state. Some existing QPT cognitive models do employ dynamical aspects when considering how a mental state changes with time, but it is often the case that several simplifying assumptions are introduced. What kind of modelling flexibility does QPT dynamics offer without any simplifying assumptions and is it likely that such flexibility will be relevant in cognitive modelling? We consider a series of nested QPT dynamical models, constructed with a view to accommodate results from a simple, hypothetical experimental paradigm on decision-making. We consider Hamiltonians more complex than the ones which have traditionally been employed with a view to explore the putative explanatory value of this additional complexity. We then proceed to compare simple models with extensions regarding both the initial state (e.g. a mixed state with a specific orthogonal decomposition; a general mixed state) and the dynamics (by introducing Hamiltonians which destroy the separability of the initial structure and by considering an open-system extension). We illustrate the relations between these models mathematically and numerically. This article is part of the themed issue ‘Second quantum revolution: foundational questions’.
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De La Peña, Victor H., Rustam Ibragimov, and Steve Jordan. "Option bounds." Journal of Applied Probability 41, A (2004): 145–56. http://dx.doi.org/10.1239/jap/1082552196.
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In this paper, we obtain sharp estimates for the expected payoffs and prices of European call options on an asset with an absolutely continuous price in terms of the price density characteristics. These techniques and results complement other approaches to the derivative pricing problem. Exact analytical solutions to option-pricing problems and to Monte-Carlo techniques make strong assumptions on the underlying asset's distribution. In contrast, our results are semi-parametric. This allows the derivation of results without knowing the entire distribution of the underlying asset's returns. Our results can be used to test different modelling assumptions. Finally, we derive bounds in the multiperiod binomial option-pricing model with time-varying moments. Our bounds reduce the multiperiod setup to a two-period setting, which is advantageous from a computational perspective.
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De La Peña, Victor H., Rustam Ibragimov, and Steve Jordan. "Option bounds." Journal of Applied Probability 41, A (2004): 145–56. http://dx.doi.org/10.1017/s0021900200112264.
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In this paper, we obtain sharp estimates for the expected payoffs and prices of European call options on an asset with an absolutely continuous price in terms of the price density characteristics. These techniques and results complement other approaches to the derivative pricing problem. Exact analytical solutions to option-pricing problems and to Monte-Carlo techniques make strong assumptions on the underlying asset's distribution. In contrast, our results are semi-parametric. This allows the derivation of results without knowing the entire distribution of the underlying asset's returns. Our results can be used to test different modelling assumptions. Finally, we derive bounds in the multiperiod binomial option-pricing model with time-varying moments. Our bounds reduce the multiperiod setup to a two-period setting, which is advantageous from a computational perspective.
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MacLeod, N. D., B. S. Nelson, J. G. McIvor, and J. P. Corfield. "Wet season resting - economic insights from scenario modelling." Rangeland Journal 31, no. 1 (2009): 143. http://dx.doi.org/10.1071/rj08043.
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Pasture degradation, particularly that attributable to overgrazing, is a significant problem across the northern Australian rangelands. Although grazing studies have identified the scope for wet season resting strategies to be used to rehabilitate degraded pastures, the economic outcome of these strategies has not been extensively demonstrated. An exploratory study of the prospective economic value of wet season resting is presented using an economic simulation model of a 28 000 ha beef enterprise located in the Charters Towers region of north-eastern Australia to explore seven hypothetical scenarios centred on the projected performance of a wet season resting strategy. A series of 20-year simulations for a range of pasture recovery profiles, stocking capacity, animal productivity responses, beef prices and agistment options are compared with a baseline scenario of taking no action. Estimates of the net present value of the 20-year difference in total enterprise gross margins between the various resting options and the ‘do nothing’ option identify that wet season resting can offer a positive economic return for the range of scenarios examined, although this is contingent on the assumptions that are made concerning the trajectories of change in carrying capacity and animal productivity. Some implications for management and policy making to support the practical implementation of wet season resting strategies are discussed.
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VIET, A. F., C. FOURICHON, and H. SEEGERS. "Review and critical discussion of assumptions and modelling options to study the spread of the bovine viral diarrhoea virus (BVDV) within a cattle herd." Epidemiology and Infection 135, no. 5 (November 17, 2006): 706–21. http://dx.doi.org/10.1017/s095026880600745x.
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SUMMARYRelevance of epidemiological models depends on assumptions on the population structure and dynamics, on the biology of the host–parasite interaction, and on mathematical modelling. In this paper we reviewed published models of the bovine viral diarrhoea virus (BVDV) spread within a herd. Modelling options and assumptions on herd dynamics and BVDV transmission were discussed. A cattle herd is a population with a controlled size. Animals are separated into subgroups according to their age or their physiological status inducing heterogeneity of horizontal transmission. Complexity of models results from: (1) horizontal and vertical virus transmission, (2) birth of persistently infected animals, (3) excretion by transiently and persistently infected animals. Areas where there was a lack of knowledge were identified. Assumptions on the force of infection used to model the horizontal virus transmission were presented and discussed. We proposed possible ways of improving models (e.g. force of infection, validation) and essential model features for further BVDV models.
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Soust-Verdaguer, B., E. Hoxha, C. Llatas, and A. Passer. "How Transport Modelling affects the building Life Cycle Assessment (LCA) results: A Case Study Analysis." IOP Conference Series: Earth and Environmental Science 1078, no. 1 (September 1, 2022): 012096. http://dx.doi.org/10.1088/1755-1315/1078/1/012096.
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Abstract The Life Cycle Assessment (LCA) of a building involves the use of various types of information about the building, including the products, processes, and services related to the building throughout its life cycle. The modelling of the transport process can be complex and may be performed based on a variety of approaches and assumptions. With existing approaches, the most accurate results those closest to the real scenario, are calculated once the building has already been built. Other approaches are based on estimations at the design stage using generic scenarios and data sources. The variation of the LCA results when employing different modelling options for transport modules is studied herein. To this end, and to identify the possible errors or dispersion of the LCA results related to the various transport modelling options, transport impacts are calculated using a case study, whereby five different modelling options are compared. The results show that the transport impact difference between the lowest values (the real scenario) and the highest values (normalised detailed scenario) is approximately 30%. To conclude, efforts should be made to better define the default scenarios, especially regarding transport distances and the correction for volumetric capacity of the transport vessels, adapted to the real scenario.
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Bianco Mauthe Degerfeld, Franz, Giovanna De Luca, Ilaria Ballarini, and Vincenzo Corrado. "Modelling of heat generators: technical standards vs detailed dynamic simulation tools." E3S Web of Conferences 343 (2022): 04005. http://dx.doi.org/10.1051/e3sconf/202234304005.
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In the last years, international technical standards have introduced several procedures for modelling the heat generation sub-system, both providing new calculation methods and updating the old ones. A still open issue concerns the modelling of these sub-systems, by adapting the standard procedure – usually founded on simplified assumptions – to the structure of a detailed dynamic simulation tool. In this paper, the main procedures introduced by the international technical standards issued under the Mandate M/480 EN of 2010 on the heat generation sub-systems are presented, with a focus on combustion systems, chillers, and heat pumps. Simplifications and assumptions are analysed, by pointing out the limits related to the simplified modelling based on empirical correlations and tabulated values. The heat generation standardised models are compared with the ones used in detailed simulation tools, such as EnergyPlus. The main differences in the input data and in the model options are presented, and advices for the completion of the information commonly found in technical data sheets are provided. The paper is aimed both at promoting an effective application of the standards in the building design field and at contributing to the standardisation activity for the achievement of more accurate calculation models.
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Geer, Alan J. "Physical characteristics of frozen hydrometeors inferred with parameter estimation." Atmospheric Measurement Techniques 14, no. 8 (August 6, 2021): 5369–95. http://dx.doi.org/10.5194/amt-14-5369-2021.
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Abstract. Frozen hydrometeors are found in a huge range of shapes and sizes, with variability on much smaller scales than those of typical model grid boxes or satellite fields of view. Neither models nor in situ measurements can fully describe this variability, so assumptions have to be made in applications including atmospheric modelling and radiative transfer. In this work, parameter estimation has been used to optimise six different assumptions relevant to frozen hydrometeors in passive microwave radiative transfer. This covers cloud overlap, convective water content and particle size distribution (PSD), the shapes of large-scale snow and convective snow, and an initial exploration of the ice cloud representation (particle shape and PSD combined). These parameters were simultaneously adjusted to find the best fit between simulations from the European Centre for Medium-range Weather Forecasts (ECMWF) assimilation system and near-global microwave observations covering the frequency range 19 to 190 GHz. The choices for the cloud overlap and the convective particle shape were particularly well constrained (or identifiable), and there was even constraint on the cloud ice PSD. The practical output is a set of improved assumptions to be used in version 13.0 of the Radiative Transfer for TOVS microwave scattering package (RTTOV-SCATT), taking into account newly available particle shapes such as aggregates and hail, as well as additional PSD options. The parameter estimation explored the full parameter space using an efficient assumption of linearly additive perturbations. This helped illustrate issues such as multiple minima in the cost function, and non-Gaussian errors, that would make it hard to implement the same approach in a standard data assimilation system for weather forecasting. Nevertheless, as modelling systems grow more complex, parameter estimation is likely to be a necessary part of the development process.
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Xu, Weijun, Guifang Liu, and Xiaojian Yu. "A Binomial Tree Approach to Pricing Vulnerable Option in a Vague World." International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems 26, no. 01 (January 31, 2018): 143–62. http://dx.doi.org/10.1142/s0218488518500083.
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The aim of this paper is pricing the vulnerable options in a vague world. Due to the vulnerability of financial markets and the economy environment in the real world, investors cannot always have precise information about firm value and default recovery rate in vulnerable option pricing. Therefore, following the framework of Klein in 1996, a fuzzy binomial tree pricing model is derived by modelling the firm value and default recovery rate as fuzzy numbers. The numerical results show that the precise information assumption about the firm value and recovery rate in Klein model may lead to underestimate the credit risk on the values of vulnerable options. This study aims to provide insights for future research on defaultable options pricing under imprecise market information.
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Webb, William. "Modelling small cell deployments within a macrocell." Digital Policy, Regulation and Governance 20, no. 1 (January 8, 2018): 14–22. http://dx.doi.org/10.1108/dprg-07-2017-0038.
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Purpose Small cells, or microcells, are often seen as a way to substantially enhance the capacity of cellular networks. Previous assumptions have been that by deploying a dense layer of small cells within a macrocell, capacity can be improved by an order of magnitude or more. However, there are complexities such as the need to share frequencies between macrocell and small cells, varying patterns of users, the balance between indoor and outdoor subscribers and the different options available within 4G for balancing loading. The purpose of this study is to understand the impact these real-world constraints have on the capacity enhancements that small cells can provide. Design/methodology/approach This paper describes a model that simulates the impact of small cell deployments in macrocells in a typical 4G network. Findings It shows that, in some cases, small cells can actually reduce capacity, while in the best case, maximum capacity gains are less than 100 per cent. Originality/value It shows that, in some cases, small cells can actually reduce capacity contrary to perceived wisdom.
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Shestakov, Dmytro. "The Hypotheses Testing Method for Evaluation of Startup Projects." Journal of Economics and Management Sciences 4, no. 4 (December 6, 2021): p47. http://dx.doi.org/10.30560/jems.v4n4p47.
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This paper suggests new perspective to evaluating innovation projects and understanding the nature of startup risks. Author consider five principal hypotheses that underlie every innovative project that comprise a bunch of respective assumptions to manage startup risks in a proactive manner. Suggested approach spots the light on a project’s uncertainties and risks, embedded investment and managerial options, and enables more comprehensive and accurate evaluation of innovation. The Hypotheses Testing Method enables to estimate risks and attractiveness of a startup project in a clear and fast manner. It replaces unclear traditional techniques like NPV and DCF, avoiding heavy cash flow modelling.
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Wang, Wansheng, Mengli Mao, and Zheng Wang. "An efficient variable step-size method for options pricing under jump-diffusion models with nonsmooth payoff function." ESAIM: Mathematical Modelling and Numerical Analysis 55, no. 3 (May 2021): 913–38. http://dx.doi.org/10.1051/m2an/2021012.
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We develop an implicit–explicit midpoint formula with variable spatial step-sizes and variable time step to solve parabolic partial integro-differential equations with nonsmooth payoff function, which describe the jump-diffusion option pricing model in finance. With spatial differential operators being treated by using finite difference methods and the jump integral being computed by using the composite trapezoidal rule on a non-uniform space grid, the proposed method leads to linear systems with tridiagonal coefficient matrices, which can be solved efficiently. Under realistic regularity assumptions on the data, the consistency error and the global error bounds for the proposed method are obtained. The stability of this numerical method is also proved by using the Von Neumann analysis. Numerical results illustrate the effectiveness of the proposed method for European options under jump-diffusion models.
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Bonetti, Daniel, Dorival Leão, Alberto Ohashi, and Vinícius Siqueira. "A General Multidimensional Monte Carlo Approach for Dynamic Hedging under Stochastic Volatility." International Journal of Stochastic Analysis 2015 (February 8, 2015): 1–21. http://dx.doi.org/10.1155/2015/863165.
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We propose a feasible and constructive methodology which allows us to compute pure hedging strategies with respect to arbitrary square-integrable claims in incomplete markets. In contrast to previous works based on PDE and BSDE methods, the main merit of our approach is the flexibility of quadratic hedging in full generality without a priori smoothness assumptions on the payoff. In particular, the methodology can be applied to multidimensional quadratic hedging-type strategies for fully path-dependent options with stochastic volatility and discontinuous payoffs. In order to demonstrate that our methodology is indeed applicable, we provide a Monte Carlo study on generalized Föllmer-Schweizer decompositions, locally risk minimizing, and mean variance hedging strategies for vanilla and path-dependent options written on local volatility and stochastic volatility models.
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Dickson, A., and K. Noble. "EASTERN AUSTRALIA'S GAS SUPPLY AND DEMAND BALANCE." APPEA Journal 43, no. 2 (2003): 137. http://dx.doi.org/10.1071/aj02071.
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Concerns have been raised about the capacity for Australia’s natural gas supplies to keep pace with growing demand, particularly in eastern Australia. Specifically, it has been suggested that unless significant infrastructure investment is undertaken now the demand/supply balance situation in eastern Australia will deteriorate quickly as natural gas resources are depleted in the face of strongly growing demand.The purpose of this study is to examine whether and when supplies in eastern Australia are likely to fall short of growing demand.A modelling framework was developed by ABARE to examine these issues at a regional level, building on ABARE’s MARKAL model of the Australian energy system. The modelling framework includes representations of potential sources of natural gas and coal seam methane in Australia by basin, existing and proposed pipeline options and regional gas demands. A number of alternative supply side assumptions were also examined to evaluate their impact on the final results, including annual production rates from various basins and the availability of commercial and non-commercial reserves.
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Andrianov, Andrei A., Olga N. Andrianova, Ilya S. Kuptsov, Leonid I. Svetlichny, and Tatyana V. Utianskaya. "A scenario study on the transition to a closed nuclear fuel cycle using the nuclear energy system modelling application package (NESAPP)." EPJ Nuclear Sciences & Technologies 8 (2022): 2. http://dx.doi.org/10.1051/epjn/2021029.
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The paper presents the results of a case study on evaluating performance and sustainability metrics for Russian nuclear energy deployment scenarios with thermal and sodium-cooled fast reactors in a closed nuclear fuel cycle. Ten possible scenarios are considered which differ in the shares of thermal and sodium-cooled fast reactors, including options involving the use of mixed uranium-plutonium oxide fuel in thermal reactors. The evolution of the following performance and sustainability metrics is estimated for the period from 2020 to 2100 based on the considered assumptions: annual and cumulative uranium consumption, needs for uranium enrichment capacities, fuel fabrication and reprocessing capacities, spent fuel stocks, radioactive wastes, amounts of plutonium in the nuclear fuel cycle, amounts of accumulated depleted uranium, and the levelised electricity generation cost. The results show that the sustainability of the Russian nuclear energy system can be significantly enhanced through the intensive deployment of sodium-cooled fast reactors and the transition to a closed nuclear fuel cycle. The authors have highlighted some issues for further considerations, which will lead to more rigorous conclusions regarding the preferred options for the development of the national nuclear energy system.
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Wang, Chao, Shengwu Zhou, and Jingyuan Yang. "The Pricing of Vulnerable Options in a Fractional Brownian Motion Environment." Discrete Dynamics in Nature and Society 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/579213.
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Under the assumption of the stock price, interest rate, and default intensity obeying the stochastic differential equation driven by fractional Brownian motion, the jump-diffusion model is established for the financial market in fractional Brownian motion setting. With the changes of measures, the traditional pricing method is simplified and the general pricing formula is obtained for the European vulnerable option with stochastic interest rate. At the same time, the explicit expression for it comes into being.
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Plagányi, Éva E., Johann D. Bell, Rodrigo H. Bustamante, Jeffrey M. Dambacher, Darren M. Dennis, Cathy M. Dichmont, Leo X. C. Dutra, et al. "Modelling climate-change effects on Australian and Pacific aquatic ecosystems: a review of analytical tools and management implications." Marine and Freshwater Research 62, no. 9 (2011): 1132. http://dx.doi.org/10.1071/mf10279.
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Climate change presents significant challenges to modelling and managing aquatic resources. Equilibrium assumptions common in many modelling approaches need to be replaced by formulations that allow for changing baselines and integration of ongoing changes and adaptations by species, ecosystems and humans. As ecosystems change, so will the ways humans use, monitor and manage them. Consequently, adaptive management loops and supporting tools deserve more prominence in the management toolbox. Models are critical tools for providing an early understanding of the challenges to be faced by integrating observations and examining possible solutions. We review modelling tools currently available to incorporate the effect of climate change on marine and freshwater ecosystems, and the implications for management of natural resources. System non-linearity can confound interpretations and hence adaptive management responses are needed that are robust to unexpected outcomes. An improvement in the ability to model the effects of climate change from a social and economic perspective is necessary. The outputs from ‘end-to-end’ and socio-ecological models can potentially inform planning, in both Australia and the Pacific region, about how best to build resilience to climate change. In this context, the importance of well directed data-collection programs is also emphasised. Lessons from this region, which is advanced with regard to modelling approaches, can guide increased use of models to test options for managing aquatic resources worldwide.
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Pérez-Escudero, Alfonso, and Gonzalo G. de Polavieja. "Adversity magnifies the importance of social information in decision-making." Journal of The Royal Society Interface 14, no. 136 (November 2017): 20170748. http://dx.doi.org/10.1098/rsif.2017.0748.
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Decision-making theories explain animal behaviour, including human behaviour, as a response to estimations about the environment. In the case of collective behaviour, they have given quantitative predictions of how animals follow the majority option. However, they have so far failed to explain that in some species and contexts social cohesion increases when conditions become more adverse (i.e. individuals choose the majority option with higher probability when the estimated quality of all available options decreases). We have found that this failure is due to modelling simplifications that aided analysis, like low levels of stochasticity or the assumption that only one choice is the correct one. We provide a more general but simple geometric framework to describe optimal or suboptimal decisions in collectives that gives insight into three different mechanisms behind this effect. The three mechanisms have in common that the private information acts as a gain factor to social information: a decrease in the privately estimated quality of all available options increases the impact of social information, even when social information itself remains unchanged. This increase in the importance of social information makes it more likely that agents will follow the majority option. We show that these results quantitatively explain collective behaviour in fish and experiments of social influence in humans.
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Jonker, Willem, Alan Colin Brent, Josephine Kaviti Musango, and Imke De Kock. "Implications of biofuel production in the Western Cape province, South Africa: A system dynamics modelling approach of South Africa: A system dynamics modelling approach." Journal of Energy in Southern Africa 28, no. 1 (March 23, 2017): 1. http://dx.doi.org/10.17159/2413-3051/2017/v28i1a1457.
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The national government instated a mandatory blending policy to facilitate the uptake and establishment of a biofuels sector in South Africa. Uncertainty exists, however, regarding the implications and effects of producing biofuels within the Western Cape province, as part of a strategy of the province to transition to a green economy. This investigation was carried out as an effort to simulate the biofuel production within the Western Cape under certain project and policy considerations. A system dynamics model was developed to identify key strategic intervention points that could strengthen the business case of biofuel production. The model showed a feasible business case for bioethanol production, with the best case showing an internal rate of return of 23% (without government subsidy), and an emissions reduction of 63% when compared with coal. It is recommended that special consideration be given to the location of bioethanol production facilities, as operational costs can be minimised by incorporating invasive alien land-clearing schemes as part of the bioethanol production. The model further showed that medium-to-large-scale biodiesel production in the province is not feasible under the given model assumptions, as the positive effects of local biodiesel production do not justify the required government subsidy of ZAR 4.30 per litre. It is recommended that a different approach be investigated, where multiple on-site small-scale biodiesel production facilities are used, thus utilising multiple feedstock options and minimising capital expenditure.Keywords: green economy; transportation; blending; uncertainty; complexity
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Zhang, Guoyi. "Optimal Geometric Mean Returns of Stocks and Their Options." International Journal of Stochastic Analysis 2012 (December 24, 2012): 1–8. http://dx.doi.org/10.1155/2012/498050.
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The optimal geometric mean return is an important property of an asset. As a derivative of the underlying asset, the option also has this property. In this paper, we show that the optimal geometric mean returns of a stock and its option are the same from Kelly criterion. It is proved by using binomial option pricing model and continuous stochastic models with self-financing assumption. A simulation study reveals the same result for the continuous option pricing model.
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Ormerod, R. "Improving odour assessment by using better dispersion models: some examples." Water Science and Technology 44, no. 9 (November 1, 2001): 149–56. http://dx.doi.org/10.2166/wst.2001.0528.
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A critical aspect of odour assessments is modelling to define exposure characteristics in affected communities, and to examine the effects of odour control options. In many cases, odour dispersion is influenced by complex or non steady-state meteorology that cannot be represented by the commonly used dispersion models, such as ISC3 and AUSPLUME. These models are based on a steady-state Gaussian plume assumption, which is often inaccurate. Recent developments in modelling of local meteorology and plume dispersion have enabled far more realistic predictions of odour dispersion. Three-dimensional models have been successfully applied to improve the predictions of odour impact and to better define the parameters for odour control options. These models more accurately represent features such as drainage flows along valley floors and around hills, and strong wind shear that can develop in stable conditions. Such conditions are often critical for a proper assessment of odour impact. Second-by-second fluctuations in odour concentrations can now be simulated using the KSP model developed by Yamartino et al. This model avoids the use of arbritrary methods of determining peak-to-mean ratios. New models can also provide detailed microscale wind fields, suitable for odour modelling in urban areas where odour dispersion is affected by very complex flows.
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Kachel, Stanisław. "The Parametric Optimization of Structure Mass of Swept Wing in Compliance to Stiffness and Strength Boundary Conditions." Solid State Phenomena 198 (March 2013): 692–97. http://dx.doi.org/10.4028/www.scientific.net/ssp.198.692.
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The paper presents the method suitable for optimization of parameters and applied to design aircraft subassemblies on the example of a swept wing. It outlines the assumptions that are necessary to develop a mathematical model and describes constraints that served as the basis to develop an algorithm and describe the corresponding procedures in the GRIP (Graphics Interactive Programming) language that is a part of the CAD/CAM/CAE Unigraphics system. The further part of the study comprises discussion how the wing parameters and the mass functional are affected by rigidity constraints and strength constraints. The algorithm for designing of aircraft components was finally developed with inputs to the multi-criteria design process Web Modelling [ of an aircraft body. The study also included initial assumptions to algorithms originally developed by the author and dedicated to modelling of components incorporated into aircraft structures.
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Petrou, Giorgos, Anna Mavrogianni, Phil Symonds, Anastasia Mylona, Dane Virk, Rokia Raslan, and Mike Davies. "Can the choice of building performance simulation tool significantly alter the level of predicted indoor overheating risk in London flats?" Building Services Engineering Research and Technology 40, no. 1 (August 2, 2018): 30–46. http://dx.doi.org/10.1177/0143624418792340.
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The accurate prediction of building indoor overheating risk is critical in order to mitigate its possible consequences on occupant health and wellbeing. The Chartered Institution of Building Services Engineers issued Technical Memorandum 59 (TM59) with the aim of achieving consistency in the modelling processes followed for the prediction of overheating risk in new dwellings. However, as each tool’s prediction may depend on its inherent assumptions, an inter-model comparison procedure was used to assess whether the choice of building performance simulation tool influences the overheating assessment. The predictions of two popular tools, IES VE and EnergyPlus, were compared for nine variations of a naturally ventilated, purpose built, London flat archetype, modelled under the default algorithm options. EnergyPlus predicted a high overheating risk according to TM59 criteria in seven out of the nine model variants, contrary to the low risk of all the IES VE variants. Analysis of heat transfer processes revealed that wind-driven ventilation and surface convection algorithms were the main sources of the observed discrepancies. The choice of simulation tool could thus influence the overheating risk assessment in flats, while the observed discrepancies in the simulation of air and heat transfer could have implications on other modelling applications. Practical application:Technical Memorandum 59 issued by the Chartered Institution of Building Services Engineers may be widely adopted within the industry to assist the prediction of overheating risk in new dwellings. This work suggests that the choice of building performance simulation tool can greatly influence the predicted overheating risk. Furthermore, the differences identified in the modelling of heat transfer processes could also impact other modelling applications. Following these results, the need for detailed empirical validation studies of naturally ventilated homes has been highlighted.
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Evangelopoulou, Vita, Zazias, and Capros. "Energy System Modelling of Carbon-Neutral Hydrogen as an Enabler of Sectoral Integration within a Decarbonization Pathway." Energies 12, no. 13 (July 2, 2019): 2551. http://dx.doi.org/10.3390/en12132551.
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This paper explores the alternative roles hydrogen can play in the future European Union (EU) energy system, within the transition towards a carbon-neutral EU economy by 2050, following the latest policy developments after the COP21 agreement in Paris in 2015. Hydrogen could serve as an end-use fuel, a feedstock to produce carbon-neutral hydrocarbons and a carrier of chemical storage of electricity. We apply a model-based energy system analysis to assess the advantages and drawbacks of these three roles of hydrogen in a decarbonized energy system. To this end, the paper quantifies projections of the energy system using an enhanced version of the PRIMES energy system model, up to 2050, to explore the best elements of each role under various assumptions about deployment and maturity of hydrogen-related technologies. Hydrogen is an enabler of sectoral integration of supply and demand of energy, and hence an important pillar in the carbon-neutral energy system. The results show that the energy system has benefits both in terms of CO2 emission reductions and total system costs if hydrogen technology reaches high technology readiness levels and economies of scale. Reaching maturity requires a significant investment, which depends on the positive anticipation of market development. The choice of policy options facilitating visibility by investors is the focus of the modelling in this paper.
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Hao, Ryan, and Ning Xiang. "Diffusion equation modelling for energy flow analysis in reverberation chambers." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 1 (August 1, 2021): 5637–42. http://dx.doi.org/10.3397/in-2021-3197.
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Noise is a growing concern in the built environment. Sound absorbers are a viable option for noise treatment. However, the characterization of their absorption coefficient in standardized measurement chambers still show challenges for high accuracy as required in practice. In recent years, experimental analysis has shown that assumptions of diffuse sound fields made in well-known reverberation chambers are unfulfilled. Specifically, that sound intensities in chamber-based measurement methods are presumed to be isotropic or diffuse. Diffusion equation models have shown dramatic changes in energy flow in the presence of highly absorptive materials under test. This has been attributed to well-documented inconsistencies reported from reverberation chamber measurements across different laboratories. This work will demonstrate that the diffusion equation model is proving to be a computationally efficient and viable method for predicting sound energy flows, garnering an increasing amount of interest from the acoustical community.
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Kramers, G., J. C. van Dam, C. J. Ritsema, F. Stagnitti, K. Oostindie, and L. W. Dekker. "A new modelling approach to simulate preferential flow and transport in water repellent porous media: Parameter sensitivity, and effects on crop growth and solute leaching." Soil Research 43, no. 3 (2005): 371. http://dx.doi.org/10.1071/sr04098.
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A modified version of the popular agrohydrological model SWAP has been used to evaluate modelling of soil water flow and crop growth at field situations in which water repellency causes preferential flow. The parameter sensitivity in such situations has been studied. Three options to model soil water flow within SWAP are described and compared: uniform flow, the classical mobile-immobile concept, and a recent concept accounting for the dynamics of finger development resulting from unstable infiltration. Data collected from a severely water-repellent affected soil located in Australia were used to compare and evaluate the usefulness of the modelling options for the agricultural management of such soils. The study shows that an assumption of uniform flow in a water-repellent soil profile leads to an underestimation of groundwater recharge and an overestimation of plant transpiration and crop production. The new concept of modelling taking finger dynamics into account provides greater flexibility and can more accurately model the observed effects of preferential flow compared with the classical mobile–immobile concept. The parameter analysis indicates that the most important factor defining the presence and extremity of preferential flow is the critical soil water content. Comparison of the modelling results with the Australian field data showed that without the use of a preferential flow module, the effects of the clay amendments to the soil were insufficiently reproduced in the dry matter production results. This means that the physical characteristics of the soil alone are not sufficient to explain the measured increase in production on clay amended soils. However, modelling with the module accounting for finger dynamics indicated that the preferential flow in water repellent soils that had not been treated with clay caused water stress for the crops, which would explain the decrease in production.
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EDMUNDS, W. J., N. J. GAY, M. KRETZSCHMAR, R. G. PEBODY, and H. WACHMANN. "The pre-vaccination epidemiology of measles, mumps and rubella in Europe: implications for modelling studies." Epidemiology and Infection 125, no. 3 (December 2000): 635–50. http://dx.doi.org/10.1017/s0950268800004672.
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Data on the pre-vaccination patterns of infection for measles, mumps and rubella are collated from a number of European countries in order to compare the epidemiology of the three viruses. Key epidemiological parameters, such as the age-specific force of infection and the basic reproduction number (R0) are estimated from case notification or serological data using standard techniques. A method is described to compare force of infection estimates derived from serological data. Analysis suggests that the pre-vaccination patterns of measles and mumps infection in the different countries were similar. In contrast, the epidemiology of rubella was highly variable between countries. This suggests that it may be acceptable to use parameter values estimated from other countries to model measles and mumps transmission, but that this approach to modelling rubella transmission requires more caution. Estimates of R0 depend on underlying mixing assumptions. Constraints were placed on R0 estimates by utilising knowledge of likely mixing patterns. The estimates for R0 were highest for measles, intermediate for mumps, and generally lowest for rubella. Analysis of within- and between-age-group transmission rates suggested that mumps transmission tends to be more concentrated within young children than the other two viruses. The implications for the design of immunization programmes are that mumps may be the easiest to control via infant immunization since it is predominantly transmitted between the very young and the variability in rubella epidemiology requires that careful consideration of the possible effects of vaccination options should be made using local data when planning rubella immunization programmes.
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Acciaio, Beatrice, Alexander M. G. Cox, and Martin Huesmann. "Model-independent pricing with insider information: a skorokhod embedding approach." Advances in Applied Probability 53, no. 1 (March 2021): 30–56. http://dx.doi.org/10.1017/apr.2020.50.
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AbstractIn this paper we consider the pricing and hedging of financial derivatives in a model-independent setting, for a trader with additional information, or beliefs, on the evolution of asset prices. In particular, we suppose that the trader wants to act in a way which is independent of any modelling assumptions, but that she observes market information in the form of the prices of vanilla call options on the asset. We also assume that both the payoff of the derivative, and the insider’s information or beliefs, which take the form of a set of impossible paths, are time-invariant. In this way we accommodate drawdown constraints, as well as information/beliefs on quadratic variation or on the levels hit by asset prices. Our setup allows us to adapt recent work of [12] to prove duality results and a monotonicity principle. This enables us to determine geometric properties of the optimal models. Moreover, for specific types of information, we provide simple conditions for the existence of consistent models for the informed agent. Finally, we provide an example where our framework allows us to compute the impact of the information on the agent’s pricing bounds.
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Nalbantis, I., A. Efstratiadis, E. Rozos, M. Kopsiafti, and D. Koutsoyiannis. "Holistic versus monomeric strategies for hydrological modelling of modified hydrosystems." Hydrology and Earth System Sciences Discussions 7, no. 5 (October 20, 2010): 8265–308. http://dx.doi.org/10.5194/hessd-7-8265-2010.
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Abstract. The modelling of modified basins that are inadequately measured constitutes a challenge for hydrological science. Often, models for such systems are detailed and hydraulics-based for only one part of the system while for other parts oversimplified models or rough assumptions are used. This is typically a bottom-up approach, which seeks to exploit knowledge of hydrological processes at the micro-scale at some components of the system. Also, it is a monomeric approach in two ways: first, essential interactions among system components may be poorly represented or even omitted; second, differences in the level of detail of process representation can lead to uncontrolled errors. Additionally, the calibration procedure merely accounts for the reproduction of the observed responses using typical fitting criteria. The paper aims to raise some critical issues, regarding the entire modelling approach for such hydrosystems. For this, two alternative modelling strategies are examined that reflect two modelling approaches or philosophies: a dominant bottom-up approach, which is also monomeric and very often, based on output information and a top-down and holistic approach based on generalized information. Critical options are examined, which codify the differences between the two strategies: the representation of surface, groundwater and water management processes, the schematization and parameterization concepts and the parameter estimation methodology. The first strategy is based on stand-alone models for surface and groundwater processes and for water management, which are employed sequentially. For each model, a different (detailed or coarse) parameterization is used, which is dictated by the hydrosystem schematization. The second strategy involves model integration for all processes, parsimonious parameterization and hybrid manual-automatic parameter optimization based on multiple objectives. A test case is examined in a hydrosystem in Greece with high complexities, such as extended surface-groundwater interactions, ill-defined boundaries, sinks to the sea and anthropogenic intervention with unmeasured abstractions both from surface and groundwater. Criteria for comparison are the physical consistency of parameters, the reproduction of runoff hydrographs at multiple sites within the basin, the likelihood of uncontrolled model outputs, the required amount of computational effort and the performance within a stochastic simulation setting.
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Stanford, Jon. "Electricity generation in a carbon constrained world: the role for gas." APPEA Journal 49, no. 2 (2009): 576. http://dx.doi.org/10.1071/aj08049.
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In March 2009, the Australian government published draft legislation for its proposed emissions trading scheme—the Carbon Pollution Reduction Scheme (CPRS). The CPRS is the main instrument that will be employed to achieve Australia’s stated objective of greenhouse gas mitigation, together with the new renewable energy target (RET) mandating that 20% of Australia’s electricity will be provided by renewable energy by 2020. The stated objective is to achieve a 5% reduction in emissions from the year 2000–2020. The objective of a 5% reduction in emissions (identified as CPRS-5 in the Treasury modelling undertaken for Garnaut and the Australian Government) is a more modest target than scientific opinion tells us is required to achieve temperature stabilisation at a level around two degrees higher than the average level now. Yet this target has been selected on the assumption that the rest of the world does not take more substantial action. If Australia seeks to achieve more than the rest of the world there will be a negligible impact on global emissions while we will export investments and jobs to less ambitious countries. In any case, a 5% reduction in emissions from 2000 levels will be difficult to achieve in the absence of major technological change being realised before 2020. It represents a reduction from the year 2000’s levels of 25% in per capita terms, and around 25% from projections of emissions under business-as-usual assumptions. Stationary energy, mainly power generation, is responsible for about half of Australia’s greenhouse gas emissions. Because this is also a sector where low emissions technologies are already available, it is expected that much of the heavy-lifting in regard to greenhouse gas mitigation will have to come from this sector. Much of the new investment in the power generation sector to 2020 will come from renewables so as to meet the RET, which equates to around 45,000 GWh of renewable generation by 2020. But what of base load generation? Apart from geothermal, that has yet to be technically and commercially proven in Australia, renewables are generally ill-suited to base load generation. Base load power in Australia has traditionally been provided by black and brown coal and with its high emissions it is unlikely to be seen as a future option in a carbon-constrained world. Lower emissions options for base load generation include: coal with carbon capture and storage (CCS); geothermal energy; nuclear energy; and, combined cycle gas turbine (CCGT). The first three options are all problematic in Australia, and would not be able to provide significant generation capacity before 2020.
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Lacy, RC. "VORTEX: a computer simulation model for population viability analysis." Wildlife Research 20, no. 1 (1993): 45. http://dx.doi.org/10.1071/wr9930045.
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Population Viability Analysis (PVA) is the estimation of extinction probabilities by analyses that incorporate identifiable threats to population survival into models of the extinction process. Extrinsic forces, such as habitat loss, over-harvesting, and competition or predation by introduced species, often lead to population decline. Although the traditional methods of wildlife ecology can reveal such deterministic trends, random fluctuations that increase as populations become smaller can lead to extinction even of populations that have, on average, positive population growth when below carrying capacity. Computer simulation modelling provides a tool for exploring the viability of populations subjected to many complex, interacting deterministic and random processes. One such simulation model, VORTEX, has been used extensively by the Captive Breeding Specialist Group (Species Survival Commission, IUCN), by wildlife agencies, and by university classes. The algorithms, structure, assumptions and applications of VORTEX are described in this paper. VORTEX models population processes as discrete, sequential events, with probabilistic outcomes. VORTEX simulates birth and death processes and the transmission of genes through the generations by generating random numbers to determine whether each animal lives or dies, to determine the number of progeny produced by each female each year, and to determine which of the two alleles at a genetic locus are transmitted from each parent to each offspring. Fecundity is assumed to be independent of age after an animal reaches reproductive age. Mortality rates are specified for each pre-reproductive age-sex class and for reproductive-age animals. Inbreeding depression is modelled as a decrease in viability in inbred animals. The user has the option of modelling density dependence in reproductive rates. As a simple model of density dependence in survival, a carrying capacity is imposed by a probabilistic truncation of each age class if the population size exceeds the specified carrying capacity. VORTEX can model linear trends in the carrying capacity. VORTEX models environmental variation by sampling birth rates, death rates, and the carrying capacity from binomial or normal distributions. Catastrophes are modelled as sporadic random events that reduce survival and reproduction for one year. VORTEX also allows the user to supplement or harvest the population, and multiple subpopulations can be tracked, with user-specified migration among the units. VORTEX outputs summary statistics on population growth rates, the probability of population extinction, the time to extinction, and the mean size and genetic variation in extant populations. VORTEX necessarily makes many assumptions. The model it incorporates is most applicable to species with low fecundity and long lifespans, such as mammals, birds and reptiles. It integrates the interacting effects of many of the deterministic and stochastic processes that have an impact on the viability of small populations, providing opportunity for more complete analysis than is possible by other techniques. PVA by simulation modelling is an important tool for identifying populations at risk of extinction, determining the urgency of action, and evaluating options for management.
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Kachel, Stanisław. "Control Curves Method of Airframe Geometry Modeling." Solid State Phenomena 199 (March 2013): 279–84. http://dx.doi.org/10.4028/www.scientific.net/ssp.199.279.
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The paper presents the methodological approach to development of curves by selection of driving parameters with the application of the method to designing and reproduction of aircraft surfaces on the examples of both newly designed aircrafts and the ones that are already in service. The major assumptions are outlined that are necessary to develop the mathematical model of driving curves and surfaces, these assumptions served as the basis to draw up the relevant algorithms and to convert them to routines of the GRIP (Graphics Interactive Programming) language that is a part of the CAD/CAM/CAE Unigraphics system. These algorithms include the newly developed tool dedicated to design aircraft components and provided with inputs to the multi-criteria synthesis of the aerodynamic profiles of aircrafts. The study comprises also the assumptions to the newly developed algorithms dedicated to modelling of components incorporated into aircraft structures, these algorithms have been successfully implemented by the author.
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Ibaibarriaga, Leire, Carmen Fernández, Andrés Uriarte, and Beatriz A. Roel. "A two-stage biomass dynamic model for Bay of Biscay anchovy: a Bayesian approach." ICES Journal of Marine Science 65, no. 2 (March 1, 2008): 191–205. http://dx.doi.org/10.1093/icesjms/fsn002.
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Abstract Ibaibarriaga, L., Fernández, C., Uriarte, A., and Roel, B. A. 2008. A two-stage biomass dynamic model for Bay of Biscay anchovy: a Bayesian approach. – ICES Journal of Marine Science, 65: 191–205. A two-stage biomass-based state-space model with stochastic recruitment processes and deterministic dynamics was developed for the Bay of Biscay anchovy population. It is fitted in a Bayesian context with posterior computations carried out using Markov chain Monte Carlo techniques. The model is tested first on a simulated dataset and the effects of different modelling assumptions and of missing values evaluated. Then, it is applied to a real historical series of commercial catch and survey data from 1987 to 2006. Results are compared with those obtained by the standard assessment model for this stock, integrated catch-at-age analysis (ICA). From the posterior distribution of biomass in the latest year (2006), the distribution of unexploited biomass in 2007 can be derived assuming the distribution of recruitment in 2007 to be a mixture of the posterior distributions of past series recruitment. Hence, the effect of different catch options on future biomass levels can be quantified in probabilistic terms. Finally, directions for possible further improvements are indicated.
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Vieira, Victor Hugo Argentino de Morais, and Dácio Roberto Matheus. "Environmental assessments of biological treatments of biowaste in life cycle perspective: A critical review." Waste Management & Research 37, no. 12 (October 18, 2019): 1183–98. http://dx.doi.org/10.1177/0734242x19879222.
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Municipal biowaste is a major environmental issue. Life-cycle assessment is a valuable tool to assess recycling options, and anaerobic digestion and composting have performed adequately. However, reviews indicate several discrepancies between studies. Thus, we critically review 25 life-cycle assessments of the composting and anaerobic digestion of municipal biowaste. Our objective is to identify decisive factors, methodological gaps and processes that affect environmental performance. We generally identified methodological gaps in expanding systems borders. In energy systems, the replaced energy source did not consider power generation or dynamic regulation. All studies adopted mixed energy sources or marginal approaches. Agroecosystems included the carbon sequestration potential and compensation for the production of synthetic fertilizers only. A limited range of scientifically proven benefits of compost use has been reported. In general, studies provided a limited account of the effects of use on land emissions, but contradictory assumptions emerged, mainly in modelling synthetic fertilizer compensation. Only three studies compensated direct emissions from the use of synthetic fertilizers, and none included indirect emissions. Further studies should include an analysis of the additional benefits of compost use, compensate for the effects of emissions from synthetic fertilizer use on land and mix attributional and consequential approaches in energy system expansion.
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Schäffer, Jürgen, Klaus von Wilpert, and Edgar Kublin. "Analysis of fine rooting below skid trails using linear and generalized additive models." Canadian Journal of Forest Research 39, no. 11 (November 2009): 2047–58. http://dx.doi.org/10.1139/x09-125.
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Soil compaction caused by forest machinery changes the basic conditions for root propagation below skid trails. In consequence, lower fine-root densities have to be expected under wheel tracks compared with other skid trail strata that experience no direct traffic. Explorative data analysis of fine-root densities below a skid trail revealed that the fundamental assumptions for linear modelling were violated. Using a generalized linear model following a Poisson distribution with a log link function for the predictor variables together with an exponential covariance function to cope with spatial autocorrelation, the formal model criteria were met. In contrast to the linear models, generalized additive models provide flexible surface estimators that enable us to model continuous response surfaces. In addition, generalized additive models allow for the calculation of confidence intervals for the estimated density surface and for the use of inferential statistics, such as comparisons between depth gradients of fine rooting at distinct transect locations or depth layers. These model characteristics improve the possibility to recognize differences and to evaluate fine-root disturbances below skid trails without integrating uncertain strata information. They also enhance the options for determining the duration of time that is necessary to restore the rooting capacity on formerly compacted soils.
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Hux, Margaret, Denise Zou, Esprit Ma, Peter Sajosi, Andreas Engstrom, Selby Ross, Eugene Benson, Andrew Briggs, and Vijayveer Bonthapally. "A Cost-effectiveness Analysis of Brentuximab Vedotin in Relapsed or Refractory Systemic Anaplastic Large Cell Lymphoma." Journal of Health Economics and Outcomes Research 4, no. 2 (October 26, 2016): 188–203. http://dx.doi.org/10.36469/9820.
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Objective: To evaluate the cost-effectiveness of brentuximab vedotin in patients with R/R sALCL from a UK NHS perspective. Methods: A partitioned survival model used clinical outcomes for brentuximab vedotin from the pivotal phase-2 single-arm trial of brentuximab vedotin in 58 patients with R/R sALCL (SG035-0004; NCT00866047), over a lifetime (30-year) time horizon. Comparison with conventional chemotherapy was based on data from the Canadian British Columbia Cancer Agency registry from 40 patients starting salvage chemotherapy after front-line treatment between 1980 and 2012. Survival was extrapolated using parametric distributions, with brentuximab vedotin risk after the trial period assumed equal to conventional chemotherapy. Other modelling assumptions were based on a systematic literature review and clinical expert opinion. Results: Based on statistical extrapolation, brentuximab vedotin was associated with 3.1 years longer duration in the progression-free survival health state and an overall survival improvement of 5.4 years, prior to discounting. In addition, brentuximab vedotin was associated with 2.5 quality-adjusted life years (QALYs) gained at a total incremental cost of £88 556, resulting in an incremental cost-effectiveness ratio (ICER) of approximately £35 400. Sensitivity analyses of alternative model assumptions provided ICERs ranging from approximately £28 100 to £61 900. Comparing only first-line salvage patients reduced the ICER to £26 800 per QALY gained. Conversely, considering only patients with Eastern Corporative Oncology Group performance status of 0 or 1 increased the ICER to approximately £38 200. At a willingness-to-pay threshold of £50 000, the estimated probability that brentuximab vedotin is cost-effective compared with conventional chemotherapy was 86.5%. Conclusion: Compared to conventional chemotherapy, and considering the full survival period, brentuximab vedotin may provide a valuable treatment choice for patients with R/R sALCL, a population with limited therapeutic options.
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Smaizys, A., E. Narkunas, V. Rudychev, and Y. Rudychev. "Analysis of Some Computer Codes Used for Evaluation of Spent Nuclear Fuel Radiation Parameters." Nuclear and Radiation Safety, no. 3(83) (September 30, 2019): 44–50. http://dx.doi.org/10.32918/nrs.2019.3(83).05.
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The radiation parameters such as radionuclide content and activities, fluxes and energy spectrum of gamma and neutrons of spent nuclear fuel are essential when planning further spent fuel management options – interim wet or dry storage or disposal into a geological repository. Radiation parameters determine the design of a storage or disposal facility, what materials, structures and thicknesses of structures should be used to provide adequate biological shielding.
Experimental measurements of spent fuel radiation parameters are rather complicated and expensive, therefore numerical methods are widely used. Various computer codes (APOLLO, BOXER, CASMO, FISPACT, ORIGEN-S, WIMS, etc.) have been developed to simulate the irradiation processes of nuclear fuel and to obtain resulting radiation parameters. Irrespective of the used computer code, the input data firstly must be entered into that code. When simulating nuclear fuel irradiation and burn-up in the reactor core, the geometrical parameters of the fuel assembly, materials’ data (chemical compositions, densities), the operating parameters of the reactor (power, operation time, coolant parameters, etc.) shall be entered into the program as initial data. Fairly often approximations of the input data are performed, for example, fuel rods in a fuel assembly are homogenized and geometrically described as a solid cylinder, the reactor operation time is assumed as continuous and at constant power. The particularity of the input data and accepted assumptions depend on what initial information is available and on the capabilities of the computer code. The modelled spent fuel radiation parameters depend not only on the input data and assumptions, but also on the cross-section databases that are used in computer codes. Computer codes TRITON, ORIGEN-S and FISPACT have been used to model the concentration of actinides and fission products in the spent fuel from the RBMK-1000 reactor. The obtained results are compared and possible reasons for the differences in the modelling results are discussed.
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Gu, Yunfei, and Martin Kunc. "Using hybrid modelling to simulate and analyse strategies." Journal of Modelling in Management 15, no. 2 (November 16, 2019): 459–90. http://dx.doi.org/10.1108/jm2-02-2019-0039.
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Purpose This paper aims to explore the applicability and strengths of proposing the three-paradigm hybrid simulation (HS) approach to developing and analysing strategies. The objective of the modelling effort is to conceptually illustrate its use in strategic planning by combining with the threat-opportunity-weakness-strength (TOWS) matrix, which builds a bridge between strategic management with the operations research community. The authors also aim to introduce a modelling framework to help model designers to apply HS to their own business issues. Design/methodology/approach The paper presents a process to develop a HS model associated with the development of strategies using the TOWS matrix. Findings After developing the model and testing four strategies, the best option for the supermarket to increase market share and sales is implementing the strength–opportunity strategy, which involves online shopping to adapt to the digital world. Research limitations/implications First, some modelling assumptions are used to simplify the development process, but they need further validation. Second, the real data collection is limited. Third, the personal learning edition of the simulation software is not a comprehensive version and has some limitations. Practical implications The hybrid model and the scenario planning introduced, in this study, could allow decision makers to rehearse the potential strategy before actual implementation. The framework is easy to implement to other business and industry. Originality/value This study links HS with strategic management, which has not been performed previously and evaluates the capability of HS in strategic planning. The functionality of the modelling platform has been tested for simulating a completely dynamic system.
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Nalbantis, I., A. Efstratiadis, E. Rozos, M. Kopsiafti, and D. Koutsoyiannis. "Holistic versus monomeric strategies for hydrological modelling of human-modified hydrosystems." Hydrology and Earth System Sciences 15, no. 3 (March 4, 2011): 743–58. http://dx.doi.org/10.5194/hess-15-743-2011.
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Abstract. The modelling of human-modified basins that are inadequately measured constitutes a challenge for hydrological science. Often, models for such systems are detailed and hydraulics-based for only one part of the system while for other parts oversimplified models or rough assumptions are used. This is typically a bottom-up approach, which seeks to exploit knowledge of hydrological processes at the micro-scale at some components of the system. Also, it is a monomeric approach in two ways: first, essential interactions among system components may be poorly represented or even omitted; second, differences in the level of detail of process representation can lead to uncontrolled errors. Additionally, the calibration procedure merely accounts for the reproduction of the observed responses using typical fitting criteria. The paper aims to raise some critical issues, regarding the entire modelling approach for such hydrosystems. For this, two alternative modelling strategies are examined that reflect two modelling approaches or philosophies: a dominant bottom-up approach, which is also monomeric and, very often, based on output information, and a top-down and holistic approach based on generalized information. Critical options are examined, which codify the differences between the two strategies: the representation of surface, groundwater and water management processes, the schematization and parameterization concepts and the parameter estimation methodology. The first strategy is based on stand-alone models for surface and groundwater processes and for water management, which are employed sequentially. For each model, a different (detailed or coarse) parameterization is used, which is dictated by the hydrosystem schematization. The second strategy involves model integration for all processes, parsimonious parameterization and hybrid manual-automatic parameter optimization based on multiple objectives. A test case is examined in a hydrosystem in Greece with high complexities, such as extended surface-groundwater interactions, ill-defined boundaries, sinks to the sea and anthropogenic intervention with unmeasured abstractions both from surface water and aquifers. Criteria for comparison are the physical consistency of parameters, the reproduction of runoff hydrographs at multiple sites within the studied basin, the likelihood of uncontrolled model outputs, the required amount of computational effort and the performance within a stochastic simulation setting. Our work allows for investigating the deterioration of model performance in cases where no balanced attention is paid to all components of human-modified hydrosystems and the related information. Also, sources of errors are identified and their combined effect are evaluated.
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Carotenuto, F., A. J. Tetarenko, and S. Corbel. "Modelling the kinematics of the decelerating jets from the black hole X-ray binary MAXI J1348–630." Monthly Notices of the Royal Astronomical Society 511, no. 4 (February 8, 2022): 4826–41. http://dx.doi.org/10.1093/mnras/stac329.
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ABSTRACT Black hole low mass X-ray binaries (BH LMXBs) can launch powerful outflows in the form of discrete ejecta. Observing the entire trajectory of these ejecta allows us to model their motion with great accuracy and this is essential for measuring their physical properties. In particular, observing the final deceleration phase, often poorly sampled, is fundamental to obtain a reliable estimate of the jet’s energy. During its 2019/2020 outburst, the BH LMXB MAXI J1348–630 launched a single-sided radio-emitting jet that was detected at large scales after a strong deceleration due to the interaction with the interstellar medium (ISM). We successfully modelled the jet motion with a dynamical external shock model, which allowed us to constrain the jet initial Lorentz factor $\Gamma _0 = 1.85^{+0.15}_{-0.12}$, inclination angle $\theta = {29.3 }_{-3.2}^{+2.7 }$ deg, and ejection date $t_{\rm ej} = 21.5_{-3.0}^{+1.8}$ (MJD–58500). Under simple assumptions on the jet opening angle and on the external ISM density, we find that the jet has a large initial kinetic energy $E_0 = 4.6^{+20.0}_{-3.4} \times 10^{46}$ erg, far greater than what commonly measured for LMXBs from the jet’s synchrotron emission. This implies that discrete ejecta radiate away only a small fraction of their total energy, which is instead transferred to the environment. The jet power estimate is larger than the simultaneous available accretion power, and we present several options to mitigate this discrepancy. We infer that MAXI J1348–630 is likely embedded in an ISM cavity with internal density $n = 0.0010^{+0.0005}_{-0.0003}$ cm−3 and radius $R_{\rm c} = 0.61^{+0.11}_{-0.09}$ pc, which could have been produced by the system’s previous activity, as proposed for other BH LMXBs.
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Рудольф Александрович, Вирц,, and Папин, Александр Алексеевич. "Modelling the storage of carbon dioxide in viscoelastic porous medium." Вычислительные технологии, no. 6 (December 23, 2022): 4–18. http://dx.doi.org/10.25743/ict.2022.27.6.002.
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Предложена математическая модель фильтрации газа в среде с переменной пористостью. В двумерном случае определяющая система уравнений в предположении малости скорости твердой фазы сведена к параболическому уравнению для эффективного давления среды и уравнению первого порядка для пористости. Проведено численное исследование полученной начально-краевой задачи. Исследовано несколько вариантов параметров нагнетания углекислого газа в пласт с малой начальной пористостью. В ходе численных расчетов определены оптимальные варианты нагнетания газа для его хранения в геологической среде в долгосрочной перспективе. Purpose. This paper presents a model that describes gas filtration in a poroelastic medium. The initial-boundary problem describing carbon dioxide injection into a geological environment is formulated. The purpose of the research is numerical solution of the initial-boundary value problem and the analysis of results of the presented numerical simulation. Methodology. The assumption that the solid phase velocity is small allows reducing the original system of constitutive two-dimensional equations to two equations for the effective pressure and porosity. For numerical implementation, the scheme of alternating directions and the Runge - Kutta method of the fourth order of accuracy are used. A parabolic equation for the effective pressure was solved using the stabilizing correction scheme and the explicit scheme for the heat equation. Grid convergence is tested by a series of computational experiments on sequences of refined grids. Findings. Several options for gas injection are considered. Optimal parameters for storing carbon dioxide in geological formations in the long term have been found. Originality/value. Taking into account the poroelastic properties and the assumption of the deformability of the solid phase of the medium allows making new predictions of the distribution of carbon dioxide in geological media. The research results can be useful for improving existing carbon dioxide storage models and for developing new ones.
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Rößiger, Gerhard, Ladislav Kulla, and Michal Bošeľa. "Changes in growth caused by climate change and other limiting factors in time affect the optimal equilibrium of close-to-nature forest management." Central European Forestry Journal 65, no. 3-4 (September 1, 2019): 180–90. http://dx.doi.org/10.2478/forj-2019-0023.
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Abstract Historical radial increment data based on tree ring analyses from the close-to-nature experimental forest management unit Smolnícka Osada in Central Slovakia were used for retrospective modelling of changes in forest dynamics to estimate the sensitivity of management planning goals under climate change. Four example years representing historical periods with typically different species-specific patterns of radial increment in mixed beech-fir-spruce forest (1910, 1950, 1980, and 2014) served as virtual starting points for the modelling. An advanced density-dependent matrix transition model was utilised for modelling stand dynamics. An integrated tool for nonlinear financial optimisation searched for an optimal management equilibrium. In addition to transition probabilities adjusted from increment data, some assumptions for changes in ingrowth and mortality related to the increment, as well as a case study concerning the reduced ingrowth changed by game browsing intensity, were tested for modelling more realistic historical ecological conditions. The sensitivity study revealed changes in the optimal management equilibrium represented by optimal basal area, tree species composition, diameter distribution and target harvest diameter over time due to the adapted ecological modelling. The main lesson of the past for the future is to avoid placing too much trust in the simple extrapolation of current trends, such as the observed continual decline in spruce related to climate change, but to be aware of temporal and possibly reversible processes, such as the observed extensive fir recovery after the reduction of air pollution. Tree species diversity appears to be the best option for the uncertain future.
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Kirschner, A., K. Ohya, D. Borodin, R. Ding, D. Matveev, V. Philipps, and U. Samm. "Prediction of long-term tritium retention in the divertor of ITER: influence of modelling assumptions on retention rates." Physica Scripta T138 (December 2009): 014011. http://dx.doi.org/10.1088/0031-8949/2009/t138/014011.
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Varga, Liz, Fatih Camci, Joby Boxall, Amir Toossi, John Machell, Phil T. Blythe, and Colin Taylor. "Transforming Critical Infrastructure." International Journal of E-Planning Research 2, no. 3 (July 2013): 38–49. http://dx.doi.org/10.4018/ijepr.2013070104.
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The application of complexity science to policy for critical infrastructure systems has never been more important. A number of issues highlight the need for policy to match the complexity of the co-evolving environment: increasing interdependency between utilities, uncontrolled demand leading to over use of diminishing resources, diverse technological opportunities with unclear investment choices, governance at different scales, public-private ownership differences and emerging business models. Systems are now so complex that people do not understand the interdependencies. Individual utilities are optimised with limited redundancy so that even minor failures can lead to major impacts throughout the whole infrastructure environment. This article proposes an ontology of critical infrastructure in which the points of conversion in the system are the generic units of analysis. Each conversion point has a set of properties representing its real world description. This ontological perspective highlights the inter-disciplinary nature of critical infrastructure systems. It also allows, through the adoption of an agent-based modelling approach, the simulation of different environmental constraints, such as those of resource availability. Methodologically, such modelling provides an abstracted view of infrastructure systems that simplifies the real world but allows policy options to be tested based on assumptions about behaviour in response to exogenous changes. Epistemologically, it focuses on a dynamic, co-evolutionary understanding of the system transition over time by examining holistic, systemic outcomes, connecting micro behaviours with macro structures. A case study of critical infrastructure in Yorkshire in the UK provides an exemplar of complexity in the real world. The model, a metaphysical representation, demonstrates how policy can be connected with the real world. This paper focuses on the infrastructure in the UK but the principles will apply to other countries.
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Ammer, Christian, and Sven Wagner. "Problems and options in modelling fine-root biomass of single mature Norway spruce trees at given points from stand data." Canadian Journal of Forest Research 32, no. 4 (April 1, 2002): 581–90. http://dx.doi.org/10.1139/x01-229.
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In a 75-year-old Norway spruce (Picea abies (L.) Karst.) stand, three different single-tree models were tested to predict the fine-root biomass of root samples. This approach is based on the assumption that the fine-root biomass at a given point determines the availability of belowground resources as, for example, soil water. All models assume a monotonously decreasing function describing the distribution of the fine-root biomass of a subject tree depending on the distance to the trunk of the tree. To the contrary, the models differ in the maximum distance from the stem where roots can be found. There were high correlations between the observed and the predicted fine-root biomasses for all models in a part of the stand where the trees are distributed less uniformly and where root biomasses are most heterogeneous. In a section with medium stand density, the model of diameter at breast height dependent root spread yields higher correlation coefficients compared with the fixed-distance approach of the two other models. Significant correlations between model predictions of root distributions and measured soil water potential supported the validity of the models. The results of the model estimations imply differences in the maximum distance of lateral root spread dependent on stand density.
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Szota, Piotr, Sebastian Mróz, Andrzej Stefanik, and Henryk Dyja. "Numerical Modelling of Ploughshares Rolling Process from Scrapped Railway Rail." Solid State Phenomena 199 (March 2013): 472–77. http://dx.doi.org/10.4028/www.scientific.net/ssp.199.472.
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In this work, a rolling schedule has been developed, which allows the scrapped S60 railway rail to be used for further processing into semi-finished or finished products. The main purpose of the investigations was to develop the shape and dimensions the rolling grooves and to select the strains in various passes in the ploughshare rolling process. The main problem during roll pass design was the ploughshare shape which is asymmetric and has a varying thickness along the width. The developed roll pass design consist of five passes: one open shape pass, one edging pass and three closed shape passes. The first open shape pass is characterized by an unusual shape which tends to reduce the band asymmetricality in the horizontal axis in such a manner as to prevent the formation of lapping in the sharp corner areas resulting from cutting. Based on the numerical modelling it has been found that the developed roll pass design allows the production of a ploughshare of dimensions conforming to the dimensional assumptions. For the numerical modelling of the rolling process, the Forge2008® computer program was employed.
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SAUERLAND, S., R. LEFERING, T. BAYER-SANDOW, P. BRÜSER, and E. A. M. NEUGEBAUER. "Fingers, Hands or Patients? the Concept of Independent Observations." Journal of Hand Surgery 28, no. 2 (April 2003): 102–5. http://dx.doi.org/10.1016/s0266-7681(02)00360-1.
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In hand surgery trials, it is often possible to take several measurements from the same patient, because many disorders here affect bilateral or multiple structures, such as the hand itself, the finger joints or the tendons. Most conventional statistical analyses that take place on the level of hands, digit rays or joints rather than patients violate the assumption that observations should be independent. Furthermore, ignoring the multiplicity of data inflates sample size and thus may lead to spurious significance. This article describes three options to deal with such problems. First, the analysis can simply be restricted to only one measurement per patient. Second, a self-controlled design may be advantageous for conditions that usually have a bilateral pattern. Third, complex statistical modelling (involving generalized estimating equations) can be used to analyse all available measurements with adjustment for data dependency.
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Pessoa da Silva, Karina Alessandra. "Tarefas que Emergem em Atividades de Modelagem Matemática em um Ambiente Educacional de Cálculo Diferencial e Integral." Jornal Internacional de Estudos em Educação Matemática 10, no. 1 (September 13, 2017): 23. http://dx.doi.org/10.17921/2176-5634.2017v10n1p23-40.
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As reflexões apresentadas neste artigo são resultados de uma pesquisa em que identificamos tarefas que emergem em aulas com modelagem matemática quando desenvolvidas em uma disciplina de Cálculo Diferencial e Integral. Para isso, nos fundamentamos nos pressupostos teóricos da modelagem matemática compreendida como uma alternativa pedagógica cujos encaminhamentos seguem as fases da modelagem e nas abordagens de tarefas enquanto ações para o desenvolvimento de uma atividade. Analisamos atividades de modelagem matemática desenvolvidas por três turmas do curso de Licenciatura em Química de uma universidade federal do Paraná. A opção metodológica para as análises e a codificação dos dados é de cunho qualitativo e segue encaminhamentos propostos na Teoria Fundamentada. A partir da codificação e análise dos dados consideramos agrupamentos realizados no que diz respeito a tarefas que emergem das atividades desenvolvidas concluindo que estas se relacionam com a situação em estudo, com a matemática que dela emerge e com o uso da tecnologia, configurando uma teoria fundamentada.Palavras-chave: Educação Matemática. Modelagem Matemática. Cálculo Diferencial e Integral. Tarefas.AbstractThe reflections presented in this article are results of a research in which we identify tasks that emerge in classes with mathematical modelling when developed in a discipline of Integral and Differential Calculus. For this, we based ourselves on the theoretical assumptions of mathematical modelling understood as a pedagogical alternative whose routing follows the phases of modelling and in the approaches of tasks as actions for the development of an activity. We analyzed mathematical modelling activities developed by three classes of the degree course in Chemistry of a federal university of Paraná. The methodological option for the analysis and the codification of the data is of qualitative character and follows directions proposed in the Grounded Theory. From the codification and analysis of the data, we consider groupings carried out with respect to tasks that emerge from the activities developed, concluding that they relate to the situation under study, to the mathematics that emerges from it and to the use of technology, forming a grounded theory.Keywords: Mathematics Education. Mathematical Modelling. Integral and Differential Calculus. Tasks.
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Xie, H., P. Millard, and T. J. Chaussalet. "A Closed Queueing Network Approach to the Analysis of Patient Flow in Health Care Systems." Methods of Information in Medicine 45, no. 05 (2006): 492–97. http://dx.doi.org/10.1055/s-0038-1634109.
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Summary Objectives: To model patient flow in health care systems with bed capacity constraints in order to provide a useful decision aid for health service managers. Methods: We model the patient flow of health care systems using a closed queueing network framework with the assumption that the system is always full. Key performance measures of the health care system are also derived. Results: Using parameters taken from a study of a geriatric department in the UK, we show that the model is useful in helping service managers to gain better understanding of the behaviour of the system. In addition, we demonstrate that the model could help improving decision-making by allowing managers to explore different options and evaluate their impacts on performance. Our findings highlight the importance of policy makers taking into account the interactions between different phases of care. Conclusions: We have developed a novel approach to modelling the flow of patients through health care systems with constrained bed capacity.
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Lednicka, Barbara, Zbigniew Otremba, and Jacek Piskozub. "Light Penetrating the Seawater Column as the Indicator of Oil Suspension—Monte Carlo Modelling for the Case of the Southern Baltic Sea." Sensors 23, no. 3 (January 19, 2023): 1175. http://dx.doi.org/10.3390/s23031175.
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The strong need to control investments related to oil extraction and the growing demand for offshore deep-water exploration are the reasons for looking for tools to make up a global underwater monitoring system. Therefore, the current study analyses the possibility of revealing the existence of oil-in-water emulsions in the water column, based on the modelling of the downwelling radiance detected by a virtual underwater sensor. Based on the Monte Carlo simulation for the large numbers of solar photons in the water, the analyses were carried out for eight wavelengths ranging from 412 to 676 nm using dispersed oil with a concentration of 10 ppm. The optical properties of the seawater were defined as typical for the southern Baltic Sea, while the oil emulsion model was based on the optical properties of crude oil extracted in this area. Based on the above-mentioned assumptions and modelling, a spectral index was obtained, with the most favourable combination of 555/412 nm, whose value is indicative of the presence of an oil emulsion in the water.