Tunis University

About: Tunis University is a education organization based out in Tunis, Tunisia. It is known for research contribution in the topics: Population & Thin film. The organization has 11745 authors who have published 15400 publications receiving 154900 citations. The organization is also known as: University of Tunis & UT.

Advanced Diagnosis of Outer Cage Damage in Double-Squirrel-Cage Induction Motors Under Time-Varying Conditions Based on Wavelet Analysis

Abstract: It is known that classical fast-Fourier-transform-based steady-state spectrum analysis, such as motor current signature analysis, may fail to detect outer cage damage in double-squirrel-cage induction motors. This is because the magnitude of the rotor fault frequency components (RFFCs) in the current spectrum of faulty motors is small, due to the low-magnitude current circulation in the outer cage under a steady-state operation. The probability of misdetection is higher in time-varying load applications, such as conveyor belts, pulverizers, etc., for which double-cage motors are frequently employed. In case of load variation, the small RFFCs are spread in a bandwidth proportional to the speed variation, which makes them even more difficult to detect. A diagnosis method based on discrete wavelet transform and optimized for sensitive detection under transient operating conditions is proposed in this paper. An experimental study on a custom-built fabricated Cu double-cage-rotor induction motor shows that the proposed method can provide improved detection of outer cage faults particularly used in time-varying load applications.

Genetic diversity of Acacia tortilis ssp. raddiana rhizobia in Tunisia assessed by 16S and 16S-23S rDNA genes analysis.

Abstract: Aims: In order to understand the genetic diversity of Acacia tortilis ssp. raddiana-rhizobia in Tunisia, isolates from nine geographical locations were obtained and analysed. Methods and Results: Characterization using restriction fragment length polymorphism analysis (RFLP) of PCR-amplified 16S rRNA gene and the intergenic spacer (IGS) between the 16S and 23S rRNA genes was undertaken. Symbiotic efficiency of the strains was also estimated. Analysis of the 16S rRNA by PCR-RFLP showed that the isolates were phylogenetically related to Ensifer ssp., Rhizobium tropicii-IIA, and Rhizobium tumefaciens species. Analysis of 16S-23S spacer by PCR-RFLP showed a high diversity of these rhizobia and revealed eleven additional groups, which indicates that these strains are genetically very diverse. Full 16S rRNA gene-sequencing showed that the majority of strains form a new subdivion inside the genera Ensifer, with Ensifer meliloti being its nearest neighbour. Nodulation test performed on the plant host demonstrated differences in the infectivity among the strains. Conclusion: Rhizobial populations that nodulate specifically and efficiently Acacia tortilis ssp. raddiana in representative soils of Tunisia is dominated by E. meliloti-like genomospecies. Significance and Impact of the Study: This paper provides the first clear characterization and symbiotic efficiency data of rhizobia strains nodulating A. tortilis in Tunisia.