•Sol-gel method was applied for the preparation of substituted Y3-xLnxFe5O12 garnets.•The substitution effect of the first 4 lanthanides (La, Ce, Pr, Nd) in YIG was investigated.•The substitutional ...level depends very much on the nature of lanthanide element.•Different magnitudes of magnetization depending on the composition were determined.•The contributions of perovskite and hematite in the samples was easily distinguished.
FTIR spectra and powder XRD patterns of Y3−xNdxFe5O12 samples with different neodymium substitutional level. Display omitted
In this study, the substitution effects of the first four lanthanides (La, Ce, Pr and Nd) in yttrium iron garnet (Y3Fe5O12, YIG) have been investigated for the first time to the best our knowledge. The Ln-substituted yttrium iron garnets (Y3−xLnxFe5O12, where Ln = La, Ce, Pr and Nd; x = 0.0; 0.75, 1.5, 2.25, 3.0) were prepared by an aqueous sol–gel method. The phase purity and structure of synthesized Y3−xLnxFe5O12 specimens were estimated using XRD analysis, FTIR spectroscopy and Mössbauer spectroscopy. It was demonstrated that substitutional level in the sol-gel derived Y3−x LnxFe5O12 (Ln = La, Ce, Pr and Nd) systems depends very much on the nature of lanthanide element. For example, the 25% substitution of Y by La small amount of side perovskite LaFeO3 phase have formed. With increasing substitutional level of La the amount of perovskite phase also increased and, consequently, the amount of garnet phase monotonically decreased. In the case of Y3−xCexFe5O12 system, the formation of monophasic garnet did not proceed in whole substitutional range. On the other hand, the monophasic Y1.5Pr1.5Fe5O12 and Y1.5Nd1.5Fe5O12 garnets have been synthesized using sol-gel chemistry approach. Only negligible amount of perovskite phase was formed in the case when 75% of yttrium was replaced by praseodymium. However, in the case of neodymium the synthesis product with such substitutional level still was monophasic garnet. The SEM analysis results revealed that the most particles were formed in the range of 0.5–40 µm showing rather broad particle size distribution. Magnetic properties were also determined by magnetization measurements.
Currently available jaw motion tracking methods require large accessories mounted on a patient and are utilized in controlled environments, for short-time examinations only. In some cases, especially ...in the evaluation of bruxism, a non-restrictive, 24-h jaw tracking method is needed. Bruxism oriented, electromyography (EMG)-based devices and sensor-enhanced occlusal splints are able to continuously detect masticatory activity but are uninformative in regards to movement trajectories and kinematics. This study explores a possibility to use a permanent magnet and a 3-axial magnetometer to track the mandible's spatial position in relation to the maxilla. An algorithm for determining the sensor's coordinates from magnetic field values was developed, and it was verified via analytical and finite element modeling and by using a 3D positioning system. Coordinates of the cubic test trajectory (a = 10 mm) were determined with root-mean-square error (RMSE) of 0.328±0.005 mm. Possibility for teeth impact detection by accelerometry was verified. Test on a 6 degrees-of-freedom (DOF), hexapod-based jaw motion simulator moving at natural speed confirmed the system's ability to simultaneously detect jaw position and the impacts of teeth. Small size of MEMS sensors is suitable for a wearable intra-oral system that could allow visualization of continuous jaw movement in 3D models and could enable new research on parafunctional jaw activities.
This paper focuses on the investigation of the diagnostic system for health monitoring and defects, detecting in composite structures using a piezoelectric sensor. A major overview of structural ...defects in composite materials that have an influence on product performance as well as material strength is presented. Particularly, the proposed diagnostic (health monitoring) system enables to monitor the composite material plate defects during the exploitation in real-time. The investigated health monitoring system can indicate the material structure defects when the periodic test input signal is provided to excite the plate. Especially, the diagnostic system is useful when the defect placement is hard to be identified. In this work, several various numerical and experimental studies were carried out. Particularly, during the first study, the piezoelectric transducer was used to produce mechanical excitation to the composite plate when the impact response is measured with another piezoelectric sensor. The second study focuses on the defect identification algorithms of the raw hologram data consisting of the recorded oscillation modes of the affected composite plate. The main paper results obtained in both studies enable us to determine whether the composite material is characterized by mechanical defects occurring during the response to the periodic excitation. In case of damage, the observed response amplitude was decreased by 70%. Finally, using the time-domain experimental results, the frequency response functions (FRFs) are applied to damage detection assessment and to obtain extra damage information.
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