Remaining Useful Life Prediction of Rolling Bearings Based on Multi-Scale Attention Residual Network.

The remaining useful life (RUL) prediction of rolling bearings based on vibration signals has attracted widespread attention. It is not satisfactory to adopt information theory (such as information entropy) to realize RUL prediction for complex vibration signals. Recent research has used more deep learning methods based on the automatic extraction of feature information to replace traditional methods (such as information theory or signal processing) to obtain higher prediction accuracy. Convolutional neural networks (CNNs) based on multi-scale information extraction have demonstrated promising effectiveness. However, the existing multi-scale methods significantly increase the number of model parameters and lack efficient learning mechanisms to distinguish the importance of different scale information. To deal with the issue, the authors of this paper developed a novel feature reuse multi-scale attention residual network (FRMARNet) for the RUL prediction of rolling bearings. Firstly, a cross-channel maximum pooling layer was designed to automatically select the more important information. Secondly, a lightweight feature reuse multi-scale attention unit was developed to extract the multi-scale degradation information in the vibration signals and recalibrate the multi-scale information. Then, end-to-end mapping between the vibration signal and the RUL was established. Finally, extensive experiments were used to demonstrate that the proposed FRMARNet model can improve prediction accuracy while reducing the number of model parameters, and it outperformed other state-of-the-art methods.

Practical method for dynamic color holographic display.

A practical method for dynamic color holographic display by using a computer-generated hologram (CGH) with a high space-bandwidth product is proposed, and a dynamic color holographic display system is designed by a space-division method. First, three primary color CGHs of different frames from a color movie are fabricated on holographic recording material by a self-made CGH microfilming system. Secondly, the CGH is fixed on an X-Y moving stage, which is controlled by the system in order to bring the CGH to the appointed position. Thirdly, three primary color lasers are used to reconstruct the CGH. The switch of the lasers is controlled by the system synchronous with the X-Y moving stage. The color video with high quality can be obtained after filtering the three primary color reconstructed wavefronts. The experimental results demonstrate that the proposed dynamic color holographic display method is effective. It has practical application value in high-quality CGH display.

Annular arrayed-Airy beams carrying vortex arrays.

We propose and experimentally demonstrate annular arrayed-Airy beams (AAABs) carrying vortex arrays by combining multiple beams. The propagation dynamics and abrupt autofocusing property are studied. The focal intensity can be greatly increased by two orders of magnitude by increasing vortex array number. Furthermore, the autofocusing property is also enhanced significantly. This tightly autofocusing property would be advantageous for the generation of high intensity laser, optical manipulation, medical treatments, and nonlinear effects.

Effect of IgY on Periodontitis and Halitosis Induced by Fusobacterium nucleatum.

Fusobacterium nucleatum is a morbific agent in periodontitis and halitosis. Egg yolk antibody (IgY) was obtained from egg yolks from chickens stimulated with F. nucleatum. This study was to assess the effectiveness of IgY on periodontitis and halitosis caused by F. nucleatum in vitro and in vivo. The growth of F. nucleatum was inhibited (p <0. 05) by different concentrations of IgY in vitro and the results of a Halimeter show volatile sulfur compounds (VSCs) were reduced to 904 ± 57 ppb at a concentration 40 mg/ml of IgY. The changes of fatty acids of F. nucleatum were determined using GC-MS. The scores for odor index of rat saliva were decreased. The major constituent of volatile organic compounds (VOCs) including short-chain acids decreased 46.2% in 10 mg/ml IgY, ammonia decreased 70% in 40 mg/ml IgY, while aldehydes and olefine ketones were almost unchanged. The ELISA assay revealed that IL-6 and TNF-α were decreased after 4 weeks' IgY treatment. Morphometric (X-ray) and histological analyses (HE) showed that IgY reduced alveolar bone loss and collagen fibers became orderly in rat models. As a result, IgY may have the potential to treat periodontitis and halitosis.

Intensity-symmetric accelerating caustic beams.

We construct and generate symmetric accelerating caustic beams (ACBs) by using 3/2-order phase-only masks with elliptical contour based on optical caustics and diffraction theory. The symmetric ACBs are a type of bimodal accelerating caustic beam with two quasi-constant intensity peaks, very similar to the combination of two face-to-face Airy-like beams judging by appearance. Their fundamental optical morphology and force properties of particles in ACBs are subsequently provided. The unique optical properties of ACBs can be exploited for practical uses, such as accelerating electrons and clearing micrometer-sized particles as a laser micrometer-sized "water pump" instead of a laser micrometer-sized "snowblower" of accelerating Airy beams.

Symmetric form-invariant dual Pearcey beams.

We introduce another type of Pearcey beam, namely, dual Pearcey (DP) beams, based on the Pearcey function of catastrophe theory. DP beams are experimentally generated by applying Fresnel diffraction of bright elliptic rings. Form-invariant Bessel distribution beams can be regarded as a special case of DP beams. Subsequently, the basic propagation characteristics of DP beams are identified. DP beams are the result of the interference of two half DP beams instead of two classical Pearcey beams. Moreover, we also verified that half DP beams (including special-case parabolic-like beams) generated by half elliptical rings (circular rings) are a new member of the family of form-invariant beams.

Hiding scattering layers for noninvasive imaging of hidden objects.

The ability to noninvasive image through turbid media has long been a major scientific and technological goal in many disciplines. A breakthrough has been made to observe objects that were completely hidden behind an opaque scattering layer. However, such approach needs not only to scan both illumination light and detector but further off-line procedures to numerically retrieve the image of the objects. Here, we report a distant invisibility-based noninvasive method that can hide scattering layers and allows to directly image objects behind. By recording holograms of the objects through a ground glass and then using the holograms produced time-reversal lights to re-illuminate the objects, we implemented to observe objects with feature size ranging from 39 µm to 80 µm that were hidden behind a 3 mm thick ground glass. Of importance, our approach opens a door towards real-time, high speed biomedical imaging and in-site inspection of integrated devices.

Directionally hiding objects and creating illusions above a carpet-like device by reflection holography.

Realization of a perfect invisibility cloak still challenges the current fabricating technologies. Most experiments, if not all, are hence focused on carpet cloaks because of their relatively low requirements to material properties. Nevertheless, present invisibility carpets are used to hide beneath objects. Here, we report a carpet-like device to directionally conceal objects and further to create illusions above it. The device is fabricated through recording a reflection hologram of objects and is used to produce a time-reversed signal to compensate for the information of the objects and further to create light field of another object so as to realize both functions of hiding the objects and creating illusions, respectively. The carpet-like device can work for macroscopic objects at visible wavelength as the distance between objects and device is at decimeter scale. Our carpet-like device to realizing invisibility and creating illusions may provide a robust way for crucial applications of magic camouflaging and anti-detection etc.

Production of accelerating quad Airy beams and their optical characteristics.

Based on a geometric caustic argument and diffraction catastrophe theory, we generate a novel form of accelerating beams using a symmetric 3/2 phase-only pattern. Such beams can be called accelerating quad Airy beams (AQABs) because they look very much like four face-to-face combined Airy beams. Optical characteristics of AQABs are subsequently investigated. The research results show that the beams have axial-symmetrical and centrosymmetrical transverse intensity patterns and quasi-diffraction-free propagation features for their four main lobes while undergoing transverse shift along parabolic trajectories. Moreover, we also demonstrate that AQABs possess self-construction ability when local areas are blocked. The unique optical properties of these beams will make them useful tools for future scientific applications.

Directionally hiding objects and creating illusions at visible wavelengths by holography.

Invisibility devices have attracted considerable attentions in the last decade. In addition to invisibility cloaks, unidirectional invisibility systems such as carpet-like cloaks and parity-time symmetric structures are also inspiring some specific researching interests due to their relatively simplifying design. However, unidirectional invisibility systems worked generally in just one certain illumination direction. Here, based on time-reversal principle, we present the design and fabrication of a kind of all-dielectric device that could directionally cancel objects and create illusions as the illuminating light was from different directions. Our devices were experimentally realized through holographic technology and could work for macroscopic objects with any reasonable size at visible wavelengths, and hence may take directional invisibility technology a big step towards interesting applications ranging from magic camouflaging, directional detection to super-resolution biomedical imaging.

Propagation characteristics of Airy-Bessel wave packets in free space.

Airy-Bessel configuration wave packets are believed to be exotic localized linear light bullets (LLBs) without spatiotemporal spread during propagation in free space. By carefully studying the propagation of ideal Airy-Bessel wave packets (ABWs) in free space, several new results were obtained. Cubic spatially induced dispersion (SID) slightly broadens Airy pulses while quadratic SID cannot temporally change ABWs transmission modes. Hence, ABWs, although remaining as superior localized linear wave packets, cannot be regarded as absolute LLBs. Moreover, cubic SID also decreases the longitudinal acceleration of the Airy pulse peak during propagation.

Color transmission analysis of color computer-generated holography.

A color transmission approach between a computer display and a color computer-generated holography (CCGH) colorimetric system is proposed based on color matching theory. Firstly, the conversion between color quantities of a computer display and a CCGH colorimetric system is discussed based on color matching theory. Secondly, the isochromatic transfer relationship of color quantity and amplitude of the object light field is proposed. Thirdly, the color object light field was encoded into a hologram, and then the hologram was reconstructed numerically. The simulation results demonstrate that our novel approach is feasible.

Spatially induced spatiotemporally nonspreading Airy-Bessel wave packets.

By studying the effect of spatially induced group velocity dispersion (SIGVD) during the propagation of ultrashort pulsed Bessel beams in free space, we numerically prove that third-order SIGVD can temporally cause Gaussian distribution of pulsed Bessel beams to gradually evolve as unsymmetrical trailing oscillatory structures. The pulse shape is confirmed to be temporal Airy distributions on the basis of the cross-correlation function. Therefore, it is demonstrated that the scheme of generating spatiotemporally nonspreading Airy-Bessel wave packets in free space is possible by using a precompensating second-order SIGVD. The results of numerical simulation show that the quasi-Airy pulses induced by third-order SIGVD are temporally nonspreading during propagation in dispersive media. The reasons for nonspreading of such Airy distribution pulses are phenomenologically analyzed by a time-frequency Wigner distribution function of the pulse.

Practical method for color computer-generated rainbow holograms of real-existing objects.

A novel method for computer-generated rainbow holograms (CGRHs) of full-color objects is proposed. First, a new algorithm for fabricating full-color CGRHs of real-existing objects is proposed based on the interrelationship between coding of a CGRH and reconstruction of the hologram. Second, a color rainbow hologram for a real-existing object is generated by combining the proposed algorithm and computer-generated hologram generating system. Finally, the hologram is outputted by an auto-microfilming system. The principle of the algorithm, the process of hologram calculation, and the hologram generating system for real-existing objects and experimental results are presented. The experimental results demonstrate that the new method is feasible.