RESUMEN
Due to the substantial reflection information of the surrounding environment, it is difficult for a conventional camera to directly capture the distinct image behind without interference from the reflected virtual image through semi-reflective media such as an acrylic plate, glass, or water. Traditional reflective artifact removal methods either demand a major commitment of calculations or constrained photography conditions such as the use of a polarizer, which often degrades the performance of the reflection removal process and imposes a limitation on the application area. A different reflection removal method is investigated, where the interfering light rays can be attenuated effectively based on a differential calculation with a Fourier single-pixel imaging method. Experiments show that this method eliminates the interference caused by reflection from interfering objects and obtains clear images through an acrylic plate (with thicknesses of 1 mm, 2 mm, and 3 mm), glass (5 mm), and even transparent water (100 mm). Another experiment has been carried out to effectively image the target by removing the reflection through the glasses, which have the same thickness (1.1 mm) but different reflectivity (20%, 30%, 40%, and 50%).
RESUMEN
As an Mn+1AXn phase ternary layered carbide, Ti3SiC2 possesses the advantages of both excellent stability and high electrical conductivity, which are considered to be promising electrode materials for supercapacitors. Ti3SiC2/Carbon nanofiber composites with one-dimensional nanostructures were successfully synthesized via electrospinning. Systematic electrochemical tests showed that the Ti3SiC2/Carbon composite possesses a large specific capacitance of 133.1 F/g at the current density of 1 A/g, high rate capability of 113.7% capacitance retention from 1 to 10 A/g, and low resistance of 1.07 Ω. After assembling the asymmetrical supercapacitor, Ti3SiC2/Carbon provides the energy density of 7.02 Wh/kg at the power density of 140 W/kg. In addition, Ti3SiC2/Carbon composite is highly stable, with 74.6% capacity retention after 4000 cycles. Ti3SiC2/Carbon's superior electrochemical properties are ascribed to the 1D nanowire structure and the high specific surface area. Ti3SiC2/Carbon is a prospective electrode material for future supercapacitors.
RESUMEN
The compound eye of insects has many excellent characteristics. Directional navigation is one of the important features of compound eye, which is able to quickly and accurately determine the orientation of an objects. Therefore, bionic curved compound eye have great potential in detecting the orientation of the target. However, there is a serious non-linear relationship between the orientation of the target and the image obtained by the curved compound eye in wide field of view (FOV), and an effective model has not been established to detect the orientation of target. In this paper, a method for detecting the orientation of the target is proposed, which combines a virtual cylinder target with a neural network. To verify the feasibility of the method, a fiber-optic compound eye that is inspired by the structure of the bee's compound eye and that fully utilizes the transmission characteristics and flexibility of optical fibers is developed. A verification experiment shows that the proposed method is able to realize quantitative detection of orientations using a prototype of the fiber-optic compound eye. The average errors between the ground truth and the predicted values of the horizontal and elevation angles of a target are 0.5951 ° and 0.6748°, respectively. This approach has great potential for target tracking, obstacle avoidance by unmanned aerial vehicles, and directional navigation control.
RESUMEN
A pulse-width multiplexing method for reducing the nuisance-alarm rate of a phase-sensitive optical time-domain reflectometer ( Ï -OTDR) is described. In this method, light pulses of different pulse-widths are injected into the sensing fiber; the data acquired at different pulse-widths are regarded as the outputs of different sensors; and these data are then processed by a multisensor data fusion algorithm. In laboratory tests with a sensing fiber on a vibrating table, the effects of pulse-width on the signal-to-noise ratio (SNR) of the Ï -OTDR data are observed. Furthermore, by utilizing the SNR as the feature in a feature-layer algorithm based on Dempsterâ»Shafer evidential theory, a four-pulse-width multiplexing Ï -OTDR system is constructed, and the nuisance-alarm rate is reduced by about 70%. These experimental results show that the proposed method has great potential for perimeter protection, since the nuisance-alarm rate is significantly reduced by using a simple configuration.
RESUMEN
The planar compound eye has the advantages of simple structure and no requirement for complex relay optical elements, but the field of view (FOV) is very difficult to expand. Overcoming the limitation of FOV, especially with simple structures, is a great challenge for the development of planar compound eyes. Different from the existing designs that only considering refraction, this article proposes a catadioptric planar compound eye based on the reflection and refraction to expand the FOV. In the proposed design, the incident light from a large angle is reflected into the lenslet array by two rotationally symmetric mirrors whose surface equations are optimized by mathematical and optical softwares. The FOV of the proposed catadioptric planar compound eye theoretically can reach 96.6°, which is much wider than the opening record of 70°. Moreover, no distortion of the imaging system can be obtained theoretically in this design. Simulation results show a linearity of better than 99% for the most of the incident angles. The verification experiments show that the FOV of the proposed device can reach 90.7° while the FOV of the corresponding planar compound eye without mirrors is 41.6°. The proposed catadioptric planar compound eye has the great potential in monitoring, detection and virtual reality since the FOV has been widen significantly.