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Unlike common rotating machines, shipborne antennas always work under variable loads and suffer from extreme ocean conditions, which makes monitoring their condition and early fault identification necessary and challenging. However, extracting weak fault characteristics from vibration signals accurately and efficiently is difficult because of multi...
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Organizations security suffer from the insider attacker, which is an employee (person) with an authorized access to resources and data of an organization then used the access to harm the organization. In reality, the number of malicious events is very small in relation to the number of normal events of the employee, so it was necessary to use a met...
Citations
... Yu et al [17] proposed a selectable weighted multi-scale MF and demonstrated its powerful capability in bearing fault diagnosis. Therefore, the MF methods above have successfully applied to rotating machinery fault diagnosis and show that MF has excellent feature extraction capability [18][19][20][21]. ...
Mechanical compound fault diagnosis is a thorny issue in the industry. To overcome this problem, a method named morphological filter - recursive least squares (MF-RLS) is proposed in this paper. In the proposed method, MF-RLS is used to sequentially separate the different fault impulse features by decomposing the observed signal into a series of iterative morphological filtering components (IMFCs). First, the measured signal is decomposed into different scales by the multi-scale morphological filter. Then, the product of kurtosis and envelope harmonic-to-noise ratio (PKEHNR) index is used to select the best IMFC. Finally, the IMFC is input to RLS to separate other fault features. After continuous iterations, the separation and extraction of the compound fault impulse features are achieved. The simulation and experiment of the mechanical compound fault have verified the effectiveness of the proposed method.
... As a compromise between their physical dimensions, electrical properties, and performances, manufacturers use some standard solutions-tuning the antenna's circuit into a resonant state when the capacitive and inductive reactances cancel each other out. Thus, the antenna must be equipped with a coil [25][26][27][28]. ...
A helicopter in flight can be considered an unstable dynamic system with many unwanted vibrations originating from multiple sources, such as the operation of the engines and individual components. These vibrations cause the degradation of the structural and functional components of a helicopter, thereby generally reducing the utility and technical efficiency of the aircraft. During the analysis of frequently recurring errors of medium-heavy helicopters, partial damage to antenna elements with vertical polarisation was detected. These damages provided the basis for the presented research, based on which supplementary vibrations caused by unwanted electromagnetic oscillations were revealed. These oscillations were detected in the process of communication between the helicopter crew and the ground ATC (air traffic control) station. This phenomenon's existence and negative influence were confirmed via measurements and modal analysis, based on which an exact synergy between harmonic frequencies of the helicopter's normal vibrations was discovered. The obtained results serve as a theoretical and practical basis for the future monitoring of this phenomenon, especially in the process of determining the "health status" of medium-heavy helicopters.
