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Conference Name: 2021 IEEE International Conference on Software Analysis, Evolution and Reengineering (SANER) Date of Conference: 9-12 March 2021 Bug handling is an essential part of the software development process. Ideally, in a bug tracking system, bugs are reported, fixed, verified, and closed. In some cases, bugs have to be reopened mostly due to an incorrect fix. However, instead of reopening the existing bug report, users may submit a new report on a previously reported bug, which causes duplicate bug reports. Additionally, users might report duplicate bugs if they are unable to reopen the previously reported bugs due to the bug being unresolved (i.e., in progress) and when they miss previously reported bug reports. These duplicate bug reports may cost extra maintenance efforts in triaging and fixing bugs.There have been several studies on characterizing reopened bugs and duplicate bug reports, however, to the best of our knowledge, there has been no prior work on understanding the dynamics of their intersection, which is missed reopen bugs. Our study is based on analyzing the differences between duplicate and non-duplicate bugs, and further categorizing the duplicated bugs. In this regard, we categorize duplicate bugs according to their creation time with respect to their master's resolution status as Master-Unresolved bugs and Master-Resolved (Missed Reopen bugs) to distinguish their properties. We compare these two different types of bugs in terms of various aspects such as their relationships to their master bugs, bug surface time, bug fix time, bug's severity, and the number of users involved. We perform case studies using the Eclipse and Mozilla projects' bug repositories that include more than 165,500 and 394,000 bug reports respectively.

© 2018 The Authors The current study systematically analyzes the impact of solidity (σ) and number of blades (n) on the aerodynamic performance of 2-, 3- and 4-bladed Darrieus H-type vertical axis wind turbines (VAWTs). Solidity varies within the wide range of 0.09–0.36. A large number of operational parameters, i.e., tip speed ratio (λ), Reynolds number (Re), turbulence intensity and reduced frequency (K) are investigated to provide a deeper insight into the impact of σ and n on the dynamic loads on blades, the turbine performance and the wake. High-fidelity unsteady Reynolds-averaged Navier-Stokes (URANS) simulations, extensively validated with experiments, are employed. The results show that the turbine optimal tip speed ratio (λopt) is invariant to a newly-introduced parameter ‘σλ3’ regardless of the turbine geometrical and operational characteristics. In addition, a new correlation is derived to estimate λopt as a function of σ which can also be employed to predict the optimal σ for a turbine with a given λ. It is also found that: (i) for constant-speed urban VAWTs, which due to the low mean wind speed in the urban environment, frequently operate at moderate to high λ a relatively-low σ is optimal; (ii) an optimal VAWT is a moderately-high-solidity variable-speed rotor maintaining a relatively-low λ where due to the large blade chord length the resulting Re and K are favorably high; (iii) within the turbine optimal operational range, turbine power coefficient (CP) is almost independent of n. The present findings support the optimal aerodynamic design of small-to large-scale VAWTs. ispartof: ENERGY vol:165 pages:1129-1148 status: published

The main purpose of most spam e-mail messages distributed on Internet today is to entice recipients into visiting World Wide Web pages that are advertised through spam. In essence, e-mail spamming is a campaign that advertises URL addresses at a massive scale and at minimum cost for the advertisers and those advertised. Nevertheless, the characteristics of URL addresses and of web sites advertised through spam have not been studied extensively. In this paper, we investigate the properties of URL-dissemination through spam e-mail, and the characteristics of URL addresses disseminated through spam. We conclude that spammers advertise URL addresses non-repetitively and that spam-advertised URLs are short-lived, elusive, and therefore hard to detect and filter. We also observe that reputable URL addresses are sometimes used as decoys against e-mail users and spam filters. These observations can be valuable for the configuration of spam filters and in order to drive the development of new techniques to fight spam. © 2007 Elsevier Ltd. All rights reserved. 31 4 966 985