Principal Component Analysis of the start-up transient and Hidden Markov Modeling for broken rotor bar fault diagnosis in asynchronous machines

This article presents a novel computational method for the diagnosis of broken rotor bars in three phase asynchronous machines. The proposed method is based on Principal Component Analysis (PCA) and is applied to the stator s three phase start-up current. The fault detection is easier in the start-up transient because of the increased current in the rotor circuit, which amplifies the effects of the fault in the stator s current independently of the motor s load. In the proposed fault detection methodology, PCA is initially utilized to extract a characteristic component, which reflects the rotor asymmetry caused by the broken bars. This component can be subsequently processed using Hidden Markov Models (HMMs). Two schemes, a multiclass and a one-class approach are proposed. The efficiency of the novel proposed schemes is evaluated by multiple experimental test cases. The results obtained indicate that the suggested approaches based on the combination of PCA and HMMs, can be successfully utilized not only for identifying the presence of a broken bar but also for estimating the severity (number of broken bars) of the fault.Georgoulas, G.; Mustafa, M.; Tsoumas, I.; Antonino Daviu, JA.; Climente Alarcón, V.; Stylios, C.; Nikolakopoulos, G. (2013). Principal Component Analysis of the start-up transient and Hidden Markov Modeling for broken rotor bar fault diagnosis in asynchronous machines. Expert Systems with Applications. 40(17):7024-7033. doi:10.1016/j.eswa.2013.06.006S70247033401

An Approach to Hotel Services Dynamic Pricing Based on the Delphi Method and Fuzzy Cognitive Maps

Part 12: First Workshop on Fuzzy Cognitive Maps Theory and Applications (FCMTA 2013)International audienceE-tourism services open up new opportunities for businesses to expand and when possible to gain completive advantage. Dynamic pricing is an area of interest for both researchers and professionals. It’s the process of price specification in a way that best suits a tourism organization under certain circumstances that reflect its competitive environment. Many research studies have addressed dynamic pricing from different perspectives. This study suggests that the use of a hybrid approach that combines Delphi method and fuzzy cognitive maps is suitable for it introduces fuzzy logic in order to capture the subjectivity and vagueness involved into evaluating the business settings, but it also provides for the necessary flexibility in analyzing the assumptions and the implications of different pricing scenarios