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The use of hybrid methods for change points and trends detection in rainfall series of northern Algeria

Zerouali Bilel, Chettih Mohamed, Abda Zaki, Mesbah Mohamed, Djemai Mohammed

Acta Geophysica

2020

Vol. 68, no. 5

1443--1460

The aim of this research is to assess relatively new hybrid methods for changes points and trends detection on rainfall series: Dynamic Programming Bayesian Change Point Approach (BA), Şen’s innovative trend method (ITM) and its double (D-ITM) and triple (T-ITM) version using the multi-scale analysis of the discrete wavelet transform (DWT) as a coupling method. Three representatives rainfall stations of northern Algeria were analysed at annual scale during the period 1920–2011. Moreover, correlation and spectral analysis (CSA) was applied for periodicity analysis. The CSA indicates the dominance of interannual to multidecadal rainfall periodicity fuctuations (2-years, 5-years and 20-years) characterising long term structured processes. Moreover, an abrupt downward trend with signifcant probability was detected from the 1970s with a relatively wet period between the periods 1950–1970 and 2001–2011. The latter is observed in particular in the central and eastern stations, well-explained by the BA-DWT. The results showed that the comparison results from diferent modelling approaches found that the hybrid models (BA-DWT, ITM-DWT, D-ITM-DWT, T-ITM-DWT) often perform better than the conventional approach (BA, ITM, D-ITM, T-ITM), where the computation time is very reasonable. The analysis revealed that information stemming from discrete wavelet spectrums signifcantly increased the accuracy of the methods for detecting hidden change points and trends.

A study of Optimal Testing Resource Allocation Problem for Modular Software with Change Point

Kaur G., Aggarwal A. G., Kedia A.

Annals of Computer Science and Information Systems

2018

Vol. 14

77--84

For evolving trustworthy software, engrossing on uncovering process of fault in software is central. Nevertheless, during testing, modifications in the testing routine, defect gravity or testing-skill maturity and working environment, there can be notable change in fault detection rate. When this sort of pattern is observed in testing time it is called change point. In this article, we inquire a resource distribution problem that optimally distributes software developing resources among modules such that the total software development cost is minimized. In this problem the effect of chief circumstantial element of change-point is considered in each module. The constraint of pulling off the desired reliability level for every individual module is also incorporated in the formulation of the problem. An algorithm based on Karush Kuhn Tucker (KKT) optimality conditions is presented to solve the resulting non-linear optimization problem. A simulated numerical illustration has been analyzed to reflect the formulation of the case and its solution by the algorithm proposed.