Dealing with Multiple Models in System Dynamics

2014 ◽  
Vol 3 (4) ◽  
pp. 17-35 ◽  
Author(s):  
Willem L. Auping ◽  
Erik Pruyt ◽  
Jan H. Kwakkel
Keyword(s):  
System Dynamics ◽  
Simulation Models ◽  
Dynamics Simulation ◽  
Multiple Models ◽  
Top Down ◽  
Bottom Up ◽  
New Approach ◽  
Behavioural Patterns ◽  
Copper Availability

This paper introduces an approach to compare simulation runs from multiple System Dynamics simulation models. Three dynamic hypotheses regarding the uncertain evolutions of long-term copper availability are introduced and used to illustrate the new approach. They correspond to three different perspectives on the copper system (global top-down, global bottom-up, and regional top-down). Although each of these models allows to generate a wealth of behavioural patterns, the focus in this paper is on the differences in trajectories caused by different models for identical values of shared parameters and identical settings of other assumptions, not on differences in behavioural patterns caused by each of the models. Hence, differences in trajectories between the three models are identified, quantified, and classified based on a quantified measure of difference. For these models, small differences between the trajectories are only found in stable runs, while the alternative perspectives are largely responsible for medium to large differences. Hence, it is concluded that multiple dynamic hypotheses may have to be modelled when dealing with uncertain issues.

scholarly journals Decision making in reverse logistics using system dynamics

2004 ◽  
Vol 14 (2) ◽  
pp. 259-272 ◽  
Author(s):  
P. Georgiadis ◽  
D. Vlachos
Keyword(s):  
Decision Making ◽  
System Dynamics ◽  
Reverse Logistics ◽  
Closed Loop ◽  
System Modeling ◽  
New Approach ◽  
Helpful Tool ◽  
Starting Point ◽  
Decision Making Tool

Reverse logistics is a modern field of consideration, research and study, providing helpful information on the operation of the closed-loop supply chain. Although the starting point of this field is traced back to the early 90?s, no standard method has been suggested, neither prevailed. The purpose of this paper is to introduce a new approach on the study of reverse logistics. It is actually a review on how System Dynamics (SD) can be a helpful tool when it is used in the reverse logistics field. The paper explains the basic theory of the system modeling and next it utilizes the reverse logistics model. Finally, an illustrative example shows how SD modeling can be used to produce a powerful long-term decision-making tool.

A System Dynamics Model for Cocaine Prevalence Estimation and Trend Projection

1993 ◽  
Vol 23 (2) ◽  
pp. 251-279 ◽  
Author(s):  
Jack B. Homer
Keyword(s):  
System Dynamics ◽  
Crack Cocaine ◽  
Simulation Models ◽  
Policy Implications ◽  
Dynamics Simulation ◽  
Prevalence Estimation ◽  
National Indicator ◽  
Sensitivity Tests ◽  
Indicator Data ◽  
Alternative Scenarios

In this article the author presents a system dynamics simulation model that reproduces a variety of national indicator data reflecting cocaine use and supply over a fifteen-year period and provides detailed estimates of underlying prevalence. Sensitivity tests are conducted that clarify observed trends such as growth in the compulsive use of crack cocaine and decline in the casual use of cocaine powder. Alternative scenarios with possible policy implications are simulated and projected through the year 2002 and the results are assessed. Researchers and decisionmakers hoping to understand and anticipate the dynamics of illicit drug use may benefit from simulation models that are realistic in detail and broad in scope.

Key factors affecting long-term penetration of global onshore wind energy integrating top-down and bottom-up approaches

2016 ◽  
Vol 85 ◽  
pp. 19-30 ◽  
Author(s):  
Hancheng Dai ◽  
Diego Silva Herran ◽  
Shinichiro Fujimori ◽  
Toshihiko Masui
Keyword(s):  
Wind Energy ◽  
Key Factors ◽  
Top Down ◽  
Bottom Up ◽  
Onshore Wind ◽  
Factors Affecting

e-Den goes down under

2017 ◽  
Vol 8 (1) ◽  
pp. 34-35
Author(s):  
Paul Brunton
Keyword(s):  
Undergraduate Education ◽  
Dental Education ◽  
Daily Basis ◽  
Dental School ◽  
Top Down ◽  
Self Directed Learning ◽  
Bottom Up ◽  
Directed Learning ◽  
The Way

Change is a constant in our profession, and we are familiar with this on a daily basis, as we constantly change how we practise. But consider how the way we learn and the very structure of our profession has changed in recent years. If I think back, I attended a traditional dental school and had, in my view, an excellent undergraduate education. Compare that top-down approach to the approach today, with its self-directed learning and student-led clinics – to give a couple of examples of a bottom-up model of providing effective dental education. The net result of this, in my view, is that today’s graduates are a little different in many respects, both when they graduate and in their long-term career ambitions.

Style-Dependency of Melodic Expectation

2015 ◽  
Vol 33 (1) ◽  
pp. 110-128 ◽  
Author(s):  
Zuzana Cenkerová ◽  
Richard Parncutt
Keyword(s):  
Learning Process ◽  
Auditory Scene Analysis ◽  
Scene Analysis ◽  
Top Down ◽  
Bottom Up ◽  
Gestalt Principles ◽  
Auditory Scene ◽  
Similar Organization ◽  
Melodic Expectation

In theories of auditory scene analysis and melodic implication/realization, melodic expectation results from an interaction between top-down processes (assumed to be learned and schema-based) and bottom-up processes (assumed innate, based on Gestalt principles). If principles of melodic expectation are partly acquired, it should be possible to manipulate them – to condition listeners' expectations. In this study, the resistance of three bottom-up expectation principles to learning was tested experimentally. In Experiment 1, expectations for stepwise motion (pitch proximity) were manipulated by conditioning listeners to large melodic leaps; preference for small intervals was reduced after a brief exposure. In Experiment 2, expectations for leaps to rise and steps to fall (step declination) were manipulated by exposing listeners to melodies comprising rising steps and falling leaps; this reduced preferences for descending seconds and thirds. Experiment 3 did not find and hence failed to alter the expectation for small intervals to be followed by an interval in the same direction (step inertia). The results support the theory that bottom-up principles of melodic perception are partly learned from exposure to pitch patterns in music. The long-term learning process could be reinforced by exposure to speech based on similar organization principles.

scholarly journals ANEMI3: An updated tool for global change analysis

PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0251489
Author(s):  
Patrick A. Breach ◽  
Slobodan P. Simonovic
Keyword(s):  
Climate Change ◽  
Water Quality ◽  
Surface Water ◽  
Water Resources ◽  
Global Change ◽  
System Dynamics ◽  
Global Economy ◽  
Dynamics Simulation ◽  
Earth System

The ANEMI model is an integrated assessment model of global change that emphasizes the role of water resources. The model is based on the principles of system dynamics simulation to analyze changes in the Earth system using feedback processes. Securing water resources for the future is a key issue of global change, and ties into global systems of population growth, climate change, carbon cycle, hydrologic cycle, economy, energy production, land use and pollution generation. Here the third iteration of the model–ANEMI3 is described, along with the methods used for parameter estimation and model testing. The main differences between ANEMI3 and previous versions include: (i) implementation of the energy-economy system based on the principles of system dynamics simulation; (ii) incorporation of water supply as an additional sector in the global economy that parallels the production of energy; (iii) inclusion of climate change effects on land yield and potentially arable land for food production, and (iv) addition of nitrogen and phosphorus based nutrient cycles as indicators of global water quality, which affect the development of surface water supplies. The model is intended for analyzing long-term global feedbacks which drive global change. Because of this, there are limitations related to the spatial scale that is used. However, the model’s simplicity can be considered a strength, as it allows for the driving feedbacks to be more easily identified. The model in its current form allows for a variety of scenarios to be created to address global issues such as climate change from an integrated perspective, or to examine the change in one model sector on Earth system behaviour. The endogenous structure of the model allows for global change to be driven entirely by model structure rather than exogenous inputs. The new additions to the ANEMI3 model are found to capture long term trends associated with global change, while allowing for the development of water supplies to be represented using an integrated approach considering global economy and surface water quality.

scholarly journals The Rule of Two: A Star Wars Edict or a Method of Reproducibility and Quality?

2018 ◽  
Author(s):  
Steven Forrester
Keyword(s):  
Shared Knowledge ◽  
Top Down ◽  
Manuscript Review ◽  
New Approach ◽  
Star Wars ◽  
The Individual ◽  
Biomedical Investigation ◽  
Scientific Workforce ◽  
Collective Thinking

In recent years, biomedical research has faced increased scrutiny over issues related to reproducibility and quality in scientific findings(1-3). In response to this scrutiny, funding institutions and journals have implemented top-down policies for grant and manuscript review. While a positive step forward, the long-term merit of these policies is questionable given their emphasis on completing a check-list of items instead of a fundamental re-assessment of how scientific investigation is conducted. Moreover, the top-down style of management used to institute these policies can be argued as being ineffective in engaging the scientific workforce to act upon these issues. To meet current and future biomedical needs, new investigative methods that emphasize collective-thinking, teamwork, shared knowledge and cultivate change from the bottom-up are warranted. Here, a perspective on a new approach to biomedical investigation within the individual laboratory that emphasizes collaboration and quality is discussed.

scholarly journals One or many normativities?

2019 ◽  
Vol 54 (1) ◽  
pp. 5
Author(s):  
Michał Piekarski
Keyword(s):  
Philosophy Of Science ◽  
Contemporary Philosophy ◽  
Top Down ◽  
Bottom Up ◽  
New Approach

The aim of the present investigation is to sketch a new approach to analysing normativity. First (§1–2) I locate the problem of normativity in the landscape of contemporary philosophy and focus on the dispute between naturalism and antinaturalism. Then (§3) I discuss the so-called top-down approach to studying normativity, to which I oppose the bottom-up approach inspired by contemporary philosophy of science (§4). I see the integration of these approaches as enabling investigations of normative phenomena that do not reduce them to just one type of normativity (e.g. morality).

scholarly journals REASSESSMENT OF UNCERTAINTY EXPANSION BY LINEAR ADDITION OF LONG-TERM COMPONENTS FROM TOP-DOWN INFORMATION

Radiocarbon ◽  
2021 ◽  
pp. 1-15
Author(s):  
G Salazar ◽  
S Szidat
Keyword(s):  
Mass Spectrometry ◽  
Measurement Uncertainty ◽  
High Precision ◽  
Accelerator Mass Spectrometry ◽  
Expanded Uncertainty ◽  
Top Down ◽  
Bottom Up ◽  
Linear Addition

ABSTRACT Since radiocarbon accelerator mass spectrometry (14C AMS) is considered a high-precision technique, reassessment of the measurement uncertainty has been a topic of interest. Scientists from analytical and metrological fields have developed the top-down and bottom-up measurement of uncertainty approaches. The 14C quoted error should approximate the uncertainty of long-term repetitions of the top-down approach in order to be realistic. The novelty of this paper is that the uncertainty of both approaches were approximated to each other. Furthermore, we apportioned the graphitization, instrumentation, and bias components in order to additively expand the quoted error. Our results are comparable to error multipliers and to long-term repeatability studies reported by other laboratories. Our laboratory was established in late 2012 with N2 as stripper gas and 7 years later, we changed to helium stripper. Thus, we were able to compare both gases, and demonstrate that helium is a better stripper gas. In absolute F14C units, the ranges of graphitization+bias combined uncertainties were (0.7 to 4.1) × 10–3 for N2 and (0.7–3.0) × 10–3 for He depending on the standard 14C content. The error multiplier for He defined as the expanded uncertainty over quoted error, in average, was 1.7; while without the bias, the multiplier was 1.3.

Trends in Scenario Development Methodologies and Integration in NUMO’s Approach

2010 ◽  
Author(s):  
Takeshi Ebashi ◽  
Katsuhiko Ishiguro ◽  
Keiichiro Wakasugi ◽  
Hideki Kawamura ◽  
Irina Gaus ◽  
...  
Keyword(s):  
Safety Assessment ◽  
International Workshop ◽  
Assessment Process ◽  
Scenario Development ◽  
Top Down ◽  
Initial State ◽  
Bottom Up ◽  
Starting Point ◽  
Consistent Treatment

The development of scenarios for quantitative or qualitative analysis is a key element of the assessment of the safety of geological disposal systems. As an outcome of an international workshop attended by European and the Japanese implementers, a number of features common to current methodologies could be identified, as well as trends in their evolution over time. In the late nineties, scenario development was often described as a bottom-up process, whereby scenarios were said to be developed in essence from FEP databases. Nowadays, it is recognised that, in practice, the approaches actually adopted are better described as top-down or “hybrid”, taking as their starting point an integrated (top-down) understanding of the system under consideration including uncertainties in initial state, sometimes assisted by the development of “storyboards”. A bottom-up element remains (hence the term “hybrid”) to the extent that FEP databases or FEP catalogues (including interactions) are still used, but the focus is generally on completeness checking, which occurs parallel to the main assessment process. Recent advances focus on the consistent treatment of uncertainties throughout the safety assessment and on the integration of operational safety and long term safety.

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