scholarly journals Short-Term Reliability Assessment for Islanded Microgrid Based on Time-Varying Probability Ordered Tree Screening Algorithm

IEEE Access ◽  
2019 ◽  
Vol 7 ◽  
pp. 37324-37333 ◽  
Author(s):  
Yingcong Guo ◽  
Shuaihu Li ◽  
Canbing Li ◽  
Hanmei Peng
BMC Medicine ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Sahamoddin Khailaie ◽  
Tanmay Mitra ◽  
Arnab Bandyopadhyay ◽  
Marta Schips ◽  
Pietro Mascheroni ◽  
...  

Abstract Background SARS-CoV-2 has induced a worldwide pandemic and subsequent non-pharmaceutical interventions (NPIs) to control the spread of the virus. As in many countries, the SARS-CoV-2 pandemic in Germany has led to a consecutive roll-out of different NPIs. As these NPIs have (largely unknown) adverse effects, targeting them precisely and monitoring their effectiveness are essential. We developed a compartmental infection dynamics model with specific features of SARS-CoV-2 that allows daily estimation of a time-varying reproduction number and published this information openly since the beginning of April 2020. Here, we present the transmission dynamics in Germany over time to understand the effect of NPIs and allow adaptive forecasts of the epidemic progression. Methods We used a data-driven estimation of the evolution of the reproduction number for viral spreading in Germany as well as in all its federal states using our model. Using parameter estimates from literature and, alternatively, with parameters derived from a fit to the initial phase of COVID-19 spread in different regions of Italy, the model was optimized to fit data from the Robert Koch Institute. Results The time-varying reproduction number (Rt) in Germany decreased to <1 in early April 2020, 2–3 weeks after the implementation of NPIs. Partial release of NPIs both nationally and on federal state level correlated with moderate increases in Rt until August 2020. Implications of state-specific Rt on other states and on national level are characterized. Retrospective evaluation of the model shows excellent agreement with the data and usage of inpatient facilities well within the healthcare limit. While short-term predictions may work for a few weeks, long-term projections are complicated by unpredictable structural changes. Conclusions The estimated fraction of immunized population by August 2020 warns of a renewed outbreak upon release of measures. A low detection rate prolongs the delay reaching a low case incidence number upon release, showing the importance of an effective testing-quarantine strategy. We show that real-time monitoring of transmission dynamics is important to evaluate the extent of the outbreak, short-term projections for the burden on the healthcare system, and their response to policy changes.


Author(s):  
Daniele Bianchi ◽  
Matthias Büchner ◽  
Andrea Tamoni

Abstract We show that machine learning methods, in particular, extreme trees and neural networks (NNs), provide strong statistical evidence in favor of bond return predictability. NN forecasts based on macroeconomic and yield information translate into economic gains that are larger than those obtained using yields alone. Interestingly, the nature of unspanned factors changes along the yield curve: stock- and labor-market-related variables are more relevant for short-term maturities, whereas output and income variables matter more for longer maturities. Finally, NN forecasts correlate with proxies for time-varying risk aversion and uncertainty, lending support to models featuring both channels.


2020 ◽  
Vol 10 (6) ◽  
pp. 2038 ◽  
Author(s):  
Yanpeng Wang ◽  
Leina Zhao ◽  
Shuqing Li ◽  
Xinyu Wen ◽  
Yang Xiong

Short-term traffic flow prediction is important to realize real-time traffic instruction. However, due to the existing strong nonlinearity and non-stationarity in short-term traffic volume data, it is hard to obtain a satisfactory result through the traditional method. To this end, this paper develops an innovative hybrid method based on the time varying filtering based empirical mode decomposition (TVF-EMD) and least square support vector machine (LSSVM). Specifically, TVF-EMD is firstly used to deal with the implied non-stationarity in the original data by decomposing them into several different subseries. Then, the LSSVM models are established for each subseries to capture the linear and nonlinear characteristics embedded in the original data, and the corresponding prediction results are superimposed to obtain the final one. Finally, case studies based on two groups of data measured from an arterial road intersection are employed to evaluate the performance of the proposed method. The experimental results indicate it outperforms the other involved models. For example, compared with the LSSVM model, the average improvements by the proposed method in terms of the indexes of mean absolute error, mean relative percentage error, root mean square error and root mean square relative error are 7.397, 15.832%, 10.707 and 24.471%, respectively.


2019 ◽  
Vol 76 (Suppl 1) ◽  
pp. A12.1-A12
Author(s):  
Sally Picciotto ◽  
Andreas Neophytou ◽  
Mark Cullen ◽  
Ellen Eisen

IntroductionShort-term disability leave can be considered as a measure of not being well enough to work. The American Manufacturing Cohort, followed 1996–2013, consists of employees of a light-metal company that provided short-term disability insurance to all employees: coverage to replace wages for up to 6 months of work absence due to medical issues. We hypothesized that since brief short-term disability leave allows workers time to recover from illness or injury without losing their jobs, it should be protective against employment termination.MethodsWe analyzed 18 386 (83% male, 80% white) hourly employees. We censored workers once their accumulated disability leave exceeded 6 weeks because longer time spent on short-term disability leave suggests more serious illness or injury that may prevent return to work. To analyze the effect of short-term disability leave on employment termination, we applied a marginal structural pooled logistic model that allowed for a time-varying hazard function. We adjusted for time-varying confounding by occupational exposures and health-related variables using inverse probability weighting. Using the estimated coefficients, we compared the predicted probabilities (by person-month) of terminating employment with the corresponding counterfactual probabilities if the worker had never taken disability leave. These probabilities yielded estimated survival curves under the two scenarios.ResultsThe average worker was followed for 5.5 years. Approximately 42% of the workers took at least one day of disability leave, and 48% terminated employment during follow-up. We estimated that 1058 (29%) more workers would have terminated employment within 5 years from cohort entry if the company had had no disability leave benefit than were predicted under the natural course.ConclusionShort-term disability leave is a potentially relevant health variable for occupational epidemiologists. This analysis suggests that short-term disability leave can help employees retain their jobs when a temporary health issue prevents them from working.


2020 ◽  
Vol 9 (3) ◽  
pp. 146-156
Author(s):  
Peterson Owusu Junior ◽  
Imhotep Alagidede ◽  
George Tweneboah

We explore interdependence and contagion in the top 9 emerging markets and the US equities using a novel time-varying GLD-based Baruník & Křehlík (2018) (BK18) spillover technique. The GLD accounts for the extreme returns while the BK18 capture the nonlinear, nonstationary, asymmetric, and time-dependent comovements in higher moments. We find dominance of some emerging markets instead of the US in the frequency-dependent spillovers. We also establish shape shift-contagion in emerging markets equities in the short-term. Our results shed new light on the sources of connectedness and contagion through the shape parameters of equity returns.


2021 ◽  
pp. 1-80
Author(s):  
Momme C. Hell ◽  
Bruce D. Cornuelle ◽  
Sarah T. Gille ◽  
Nicholas J. Lutsko

AbstractSouthern Ocean (SO) surface winds are essential for ventilating the upper ocean by bringing heat and CO2 to the ocean interior. The relationships between mixed-layer ventilation, the Southern Annular Mode (SAM), and the storm tracks remain unclear because processes can be governed by short-term wind events as well as long-term means.In this study, observed time-varying 5-day probability density functions (PDFs) of ERA5 surface winds and stresses over the SO are used in a singular value decomposition to derive a linearly independent set of empirical basis functions. The first modes of wind (72% of the total wind variance) and stress (74% of the total stress variance) are highly correlated with a standard SAM index (r = 0.82) and reflect SAM’s role in driving cyclone intensity and, in turn, extreme westerly winds. This Joint PDFs of zonal and meridional wind show that southerly and less westerly winds associated with strong mixed-layer ventilation are more frequent during short and distinct negative SAM phases. The probability of these short-term events might be related to mid-latitude atmospheric circulation. The second mode describes seasonal changes in the wind variance (16% of the total variance) that are uncorrelated with the first mode.The analysis produces similar results when repeated using 5-day PDFs from a suite of scatterometer products. Differences between wind product PDFs resemble the first mode of the PDFs. Together, these results show a strong correlation between surface stress PDFs and the leading modes of atmospheric variability, suggesting that empirical modes can serve as a novel pathway for understanding differences and variability of surface stress PDFs.


Sign in / Sign up

Export Citation Format

Share Document