Academic literature on the topic 'BACK-TESTING ANALYSIS'

To solve the problem about prototype development of electrical-excited power conversion system of large-scale direct-driven wind turbine and the test challenges during mass-production, advance technology solutions by full power back-to-back testing, focusing on the electrical topology including the key technologies and the working modes. Finally, introduce the relevant standards and the test methods in pilot project, listing part of test results and their analysis.

Purpose The purpose of the paper is to back-test value-at-risk (VaR) models for conditional distributions belonging to a Generalized Hyperbolic (GH) family of Lévy processes – Variance Gamma, Normal Inverse Gaussian, Hyperbolic distribution and GH – and compare their risk-management features with a traditional unconditional extreme value (EV) approach using data from future contracts return data of S&P500, FTSE100, DAX, HangSeng and Nikkei 225 indices. Design/methodology/approach The authors apply tail-based and Lévy-based calibration to estimate the parameters of the models as part of the initial data analysis. While the authors utilize the peaks-over-threshold approach for generalized Pareto distribution, the conditional maximum likelihood method is followed in case of Lévy models. As the Lévy models do not have closed form expressions for VaR, the authors follow a bootstrap method to determine the VaR and the confidence intervals. Finally, for back-testing, they use both static calibration (on the entire data) and dynamic calibration (on a four-year rolling window) to test the unconditional, independence and conditional coverage hypotheses implemented with 95 and 99 per cent VaRs. Findings Both EV and Lévy models provide the authors with a conservative proportion of violation for VaR forecasts. A model targeting tail or fitting the entire distribution has little effect on either VaR calculation or a VaR model’s back-testing performance. Originality/value To the best of the authors’ knowledge, this is the first study to explore the back-testing performance of Lévy-based VaR models. The authors conduct various calibration and bootstrap techniques to test the unconditional, independence and conditional coverage hypotheses for the VaRs.

Following detection of the first 100 confirmed cases of COVID-19 in early April, Bangladesh stepped up its efforts to strengthen testing capacity in order to curb the spread of the disease across the country. This paper sheds light on the position of Bangladesh in relation to its South Asian neighbors India and Pakistan with respect to testing capacity and ability to detect cases with increased testing. It also analyzes recent data on case counts and testing numbers in Bangladesh, to provide an idea regarding the number of extra tests needed to detect a substantial number of cases within a short period of time. Findings indicate that compared to India and Pakistan, Bangladesh was able to detect more cases by increasing testing levels and expand its testing capacity by performing more per capita tests. In spite of these achievements, the rate of reported cases per 100 tests was consistently higher for Bangladesh compared to India, which suggests that in addition to increased testing, other factors, such as, effective enforcement of social distancing and efficient contact tracing are just as important in curbing the spread of the disease. The analysis reveals that current testing levels in Bangladesh are not adequate. Based on the findings, we recommend a 30-50\% growth of the current test rate in the next few days so that by detecting and isolating more cases, Bangladesh could, in effect, contain the spread of new infections. The challenge, however, is to mobilize resources necessary to expand geographical coverage and improve testing quality while enforcing social distancing and performing efficient contact tracing.

This paper proposes slip line fields for bending of unequally grooved specimens that has a sharp crack in one side and a sharp V-notch in the other side. Depending on the back angle, two slip line fields are proposed, from which the limit moment and crack tip stress fields are obtained as a function of the back angle. Excellent agreements between slip line field solutions with those from detailed finite element limit analysis based on non-hardening plasticity provide confidence in the proposed slip line fields. Based on these results, possibility of designing a new toughness testing specimen with varying crack tip constraint is discussed.