Search Results (3)

With the widespread use and increasing importance of few-mode fibers (FMFs), comprehensive dispersion measurement for FMFs with large mode numbers is in urgent demand. Among existing methods, spatially and spectrally resolved (S²) imaging technique offers distinct advantages for measuring differential mode group delay (DMGD) and chromatic dispersion (CD) parameters. However, it suffers from several limitations such as uncontrollable mode excitation and an inability to measure absolute CD. In this study, we enhance the traditional S² method, making it possible to effectively measure the complete dispersion for high-mode-count FMFs. By introducing a mode multiplexer (MMUX), selectively and proportionally mode excitation can be realized. Combined with a tunable delay line array, the misalignment of the MMUX’s fiber pigtail lengths is canceled. Additionally, with the help of a reference path capable of generating planar light, the measurement of the absolute CD is enabled. Based on the enhanced MMUX-assisted S², a simultaneous DMGD and absolute CD measurement for an FMF supporting up to six LP modes is conducted, which has not been previously demonstrated with a single S²-based system. The proposed paradigm significantly expands the mode number of FMF measurable by S², enriches the parameters that S² can cover, and even has great inspiration for other measurement methods. Full article

Mosquitoes are one of the most important disease vectors from a medical viewpoint in that they transmit several diseases such as malaria, filariasis, yellow and Dengue fever. Mosquito vector control and personal protection from mosquito bites are currently the most efficient ways to prevent these diseases. Several synthetic repellents such as DEET, ethyl butylacetylaminopropionate (IR3535) and 1-(1-methylpropoxycarbonyl)-2-(2-hydroxyethyl)piperidine) (Picaridin), have been widely used to prevent humans from receiving mosquito bites. However, the use of synthetic repellents has raised several environment and health concerns. Therefore, essential oils (EOs) as natural alternatives receive our attention. In order to discover highly effective mosquito repellents from natural sources, the repellent activity of 60 commercial EOs against Ae. albopictus was screened in this study. Eight EOs including cinnamon, marjoram, lemongrass, bay, chamomile, jasmine, peppermint2, and thyme, showed a suitable repellent rate (>40%) at the tested dose of 10 μg/cm². Then, their main constituents were analyzed by GC-MS, and the active constituents were identified. The most active compounds including cinnamaldehyde, citral and terpinen-4-ol, exhibited an 82%, 65% and 60% repellent rate, respectively. Moreover, the nanoemulsions of the three active compounds were prepared and characterized. In the arm-in-cage assay, the protection times of the nanoemulsions of cinnamaldehyde and citral were significantly extended compared with their normal solutions. This study provides several lead compounds to develop new mosquito repellents, and it suggests that nanoemulsification is an effective method for improving the duration of the activity of natural repellents. Full article

Sparse decomposition has been widely used in gear local fault diagnosis due to its outstanding performance in feature extraction. The extraction results depend heavily on the similarity between dictionary atoms and fault feature signal. However, the transient impact signal aroused by gear local defect is usually submerged in meshing harmonics and noise. It is still a challenging task to construct high-quality impact dictionary for complex actual signal. To handle this issue, a novel impact feature extraction method based on Empirical Mode Decomposition (EMD) and sparse decomposition is proposed in this paper. Firstly, EMD is employed to adaptively decompose the original signal into several Intrinsic Mode Functions (IMFs). The high-frequency resonance component is separated from meshing harmonics and part of the noise. Then, the IMF with the prominent impact features is selected as the Main Intrinsic Mode Function (MIMF) based on the kurtosis. Accordingly, the modal parameters required for impact dictionary are identified from the MIMF by correlation filtering. Finally, the transient impact component is extracted from the original signal by Match Pursuit (MP). The proposed method was adequately evaluated by a gear local fault simulation signal, and the single-stage gearbox and five-speed transmission experiments. The effectiveness and superiority of the proposed method is validated by comparison with other feature extraction techniques. Full article