Time‐Varying Sensitivity Analysis Reveals Relationships Between Watershed Climate and Variations in Annual Parameter Importance in Regions with Strong Inter‐Annual Variability

2020 ◽  
Author(s):  
R. Basijokaite ◽  
C. Kelleher
Keyword(s):  
Sensitivity Analysis ◽  
Time Varying ◽  
Annual Variability

scholarly journals A Simple Time-Varying Sensitivity Analysis (TVSA) for Assessment of Temporal Variability of Hydrological Processes

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2463 ◽  
Author(s):  
Yelena Medina ◽  
Enrique Muñoz
Keyword(s):  
Sensitivity Analysis ◽  
Temporal Variability ◽  
Time Windows ◽  
Computational Cost ◽  
Time Varying ◽  
Moving Window ◽  
Time Sensitivity ◽  
Annual Time ◽  
Low Computational Cost ◽  
High Computational Cost

Time-varying sensitivity analysis (TVSA) allows sensitivity in a moving window to be estimated and the time periods in which the specific components of a model can affect its performance to be identified. However, one of the disadvantages of TVSA is its high computational cost, as it estimates sensitivity in a moving window within an analyzed series, performing a series of repetitive calculations. In this article a function to implement a simple TVSA with a low computational cost using regional sensitivity analysis is presented. As an example of its application, an analysis of hydrological model results in daily, monthly, and annual time windows is carried out. The results show that the model allows the time sensitivity of a model with respect to its parameters to be detected, making it a suitable tool for the assessment of temporal variability of processes in models that include time series analysis. In addition, it is observed that the size of the moving window can influence the estimated sensitivity; therefore, analysis of different time windows is recommended.

scholarly journals Our Specific Approach on Mastering Uncertainty

2021 ◽  
pp. 43-111
Author(s):  
Peter F. Pelz ◽  
Robert Feldmann ◽  
Christopher M. Gehb ◽  
Peter Groche ◽  
Florian Hoppe ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Uncertainty Propagation ◽  
Main Topic ◽  
Time Varying ◽  
Robust Optimisation ◽  
Specific Approach ◽  
Process Chains ◽  
Technical Systems ◽  
The Difference ◽  
Dynamic Time

AbstractThis chapter serves as an introduction to the main topic of this book, namely to master uncertainty in technical systems. First, the difference of our approach to previous ones is highlighted. We then discuss process chains as an important type of technical systems, in which uncertainty propagates along the chain. Five different approaches to master uncertainty in process chains are presented: uncertainty identification, uncertainty propagation, robust optimisation, sensitivity analysis and model adaption. The influence of the process on uncertainty and methods depends on whether it is dynamic/time-varying and/or active. This brings us to the main strategies for mastering uncertainty: robustness, flexibility and resilience. Finally, three different concrete technical systems that are used to demonstrate our methods are presented.

The Automobile Tension Bar Time-Varying Reliability Sensitivity Analysis

2014 ◽  
Vol 620 ◽  
pp. 143-147
Author(s):  
Shu Sen Liu ◽  
Bo Qiang Shi ◽  
Wen Yu Zhang ◽  
Xue Jie Fu ◽  
Yue Wei Wu
Keyword(s):  
Sensitivity Analysis ◽  
Optimal Design ◽  
Optimization Design ◽  
Design Parameters ◽  
Time Varying ◽  
Reliability Sensitivity ◽  
Reliability Sensitivity Analysis ◽  
Robust Optimal Design ◽  
Robust Optimization Design ◽  
The Impact

In this paper, the design of a automobile tension bar analysis example, the use of sensitivity analysis of time-varying reliability robust optimal design tension bar design parameters for reliability sensitivity analysis shows that the reliability of the impact of the strength of the material and rod diameter is positive, and the reliability of the impact of the load and rod diameter is negative. Correct application of time-varying reliability robust optimal design of mechanical parts when variant reliability robust optimization design, design service at any time during the period were not sensitive to changes of the design parameters of the reliability of the parts, and improve the parts reliability soundness.

Sensitivity Analysis of Dynamic Models to Uncertainties in Inputs Data With Time-Varying Variances

Technometrics ◽  
2006 ◽  
Vol 48 (1) ◽  
pp. 74-87 ◽  
Author(s):  
Nacim Ramdani ◽  
Yves Candau ◽  
Gilles Guyon ◽  
Christophe Dalibart
Keyword(s):  
Sensitivity Analysis ◽  
Dynamic Models ◽  
Time Varying

scholarly journals Coordination and control – limits in standard representations of multi-reservoir operations in hydrological modeling

2021 ◽  
Vol 25 (3) ◽  
pp. 1365-1388
Author(s):  
Charles Rougé ◽  
Patrick M. Reed ◽  
Danielle S. Grogan ◽  
Shan Zuidema ◽  
Alexander Prusevich ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Water Balance ◽  
River Basins ◽  
Unintended Consequences ◽  
Water Balance Model ◽  
Low Flow ◽  
Balance Model ◽  
Time Varying ◽  
Reservoir Operations ◽  
Balance Dynamics

Abstract. Major multi-reservoir cascades represent a primary mechanism for dealing with hydrologic variability and extremes within institutionally complex river basins worldwide. These coordinated management processes fundamentally reshape water balance dynamics. Yet, multi-reservoir coordination processes have been largely ignored in the increasingly sophisticated representations of reservoir operations within large-scale hydrological models. The aim of this paper is twofold, namely (i) to provide evidence that the common modeling practice of parameterizing each reservoir in a cascade independently from the others is a significant approximation and (ii) to demonstrate potential unintended consequences of this independence approximation when simulating the dynamics of hydrological extremes in complex reservoir cascades. We explore these questions using the Water Balance Model, which features detailed representations of the human infrastructure coupled to the natural processes that shape water balance dynamics. It is applied to the Upper Snake River basin in the western US and its heavily regulated multi-reservoir cascade. We employ a time-varying sensitivity analysis that utilizes the method of Morris factor screening to explicitly track how the dominant release rule parameters evolve both along the cascade and in time according to seasonal high- and low-flow events. This enables us to address aim (i) by demonstrating how the progressive and cumulative dominance of upstream releases significantly dampens the ability of downstream reservoir rules' parameters to influence flow conditions. We address aim (ii) by comparing simulation results with observed reservoir operations during critical low-flow and high-flow events in the basin. Our time-varying parameter sensitivity analysis with the method of Morris clarifies how independent single-reservoir parameterizations and their tacit assumption of independence leads to reservoir release behaviors that generate artificial water shortages and flooding, whereas the observed coordinated cascade operations avoided these outcomes for the same events. To further explore the role of (non-)coordination in the large deviations from the observed operations, we use an offline multi-reservoir water balance model in which adding basic coordination mechanisms drawn from the observed emergency operations is sufficient to correct the deficiencies of the independently parameterized reservoir rules from the hydrological model. These results demonstrate the importance of understanding the state–space context in which reservoir releases occur and where operational coordination plays a crucial role in avoiding or mitigating water-related extremes. Understanding how major infrastructure is coordinated and controlled in major river basins is essential for properly assessing future flood and drought hazards in a changing world.

Abstract P210: Cardiovascular Safety of Dementia Drugs Among Medicare Beneficiaries

2011 ◽  
Vol 4 (suppl_2) ◽  
Author(s):  
Emil L Fosbol ◽  
Eric D Peterson ◽  
Yinghong Zhang ◽  
Lesley H Curtis ◽  
Isao Iwata ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Cardiovascular Events ◽  
Heart Association ◽  
Time Varying ◽  
Cardiovascular Safety ◽  
Medicare Beneficiaries ◽  
Intention To Treat ◽  
Increased Risk ◽  
One Year ◽  
The Individual

Background: A recent randomized clinical trial raised a concern about the safety of rivastigmine, one of the drugs used to treat dementia. We examined the comparative cardiovascular safety of dementia medications in a sample of Medicare patients. Methods: We identified a cohort of new-users of dementia medications (donepezil, galantamine, rivastigmine, or memantine) aged 65 years or more in the national 5% Medicare sample (July 1, 2006 to December 31, 2007). We assessed the association between use of dementia drugs and subsequent myocardial infarction (MI), heart failure (HF), or atrioventricular (AV) block/syncope hospitalizations Patients were censored at death or at the end of the study period; Cox proportional hazard model was used to compare cardiovascular events among users of the individual dementia medications on an intention-to-treat approach. We also conducted a sensitivity analysis using a time-varying exposure approach. Results: Overall, 19,844 initiators of dementia drugs were identified; donepezil (n= 13,179), galantamine (n=709), rivastigmine (n=1,030), memantine (n=3578), or a combination of these (n= 1348). Median age was 82 years (interquartile range [IQR] 77-87); most patients were women (74%) and Caucasian (80%). During a median follow-up of 230 days (IQR: 112-355), 741 CV composite events were identified. The initiation of rivastigmine was not associated with increased CV risk relative to initiating donepezil (adjusted hazard ratio [HR] 0.89, 95% confidence interval [CI]: 0.62-1.27). Similarly, initiation of galantamine (HR 0.70, CI: 0.45-1.09), memantine (HR 0.84, CI: 0.69-1.02), or a combination (HR 1.19; CI: 0.91-1.55) was not associated with increased CV events relative to donepezil. The results were similar among subgroups of patients with HF or MI and in the sensitivity analysis modeling time-varying exposure. Conclusions: In a large cohort of Medicare beneficiaries, we observed no increased risk of cardiovascular events in patients who initiated rivastigmine. All currently marketed dementia drugs had a similar cardiovascular safety within one year of their initiation. Further long-term monitoring of these agents is indicated.Funding(This research has received full or partial funding support from the American Heart Association, National Center)

scholarly journals Coordination of Time-Varying Price Supply Chain with Inequity-Averse Retailers

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Shuanjun Song ◽  
Sheng Hu
Keyword(s):  
Sensitivity Analysis ◽  
Supply Chain ◽  
Response Time ◽  
Decision Model ◽  
Inequity Aversion ◽  
Model Parameters ◽  
Time Varying ◽  
Market Demand ◽  
Cooperative System ◽  
Buy Back

In order to coordinate time-varying price supply chain with inequity-averse retailers, this paper proposes a cooperative system decision model based on buy-back contract. The model concentratedly takes the market demand, manufacturers’ order response time, retailers’ inequity aversion, and time-varying price into consideration. Through sensitivity analysis of model parameters, the influence of inequity aversion characteristics of retailers on contract parameters is analyzed by a numerical example. The result reveals that the cooperative system based on buy-back contract can coordinate such supply chains. And it shows that when the retailer has disadvantageous inequity aversion, the buy-back contract is beneficial to the manufacturer; when the retailer has advantageous inequity aversion, the buy-back contract is beneficial to the retailer.

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