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Inspired by the human eye retina, foveated single-pixel imaging employs an iterative algorithm, which, unfortunately, poses a challenge for real-time imaging due to its time-consuming nature. To address this issue, we present a non-iterative foveated single-pixel imaging method based on a computationally fast algorithm, reducing time consumption by five orders of magnitude. The fast algorithmic transform facilitates the acquisition of foveated reconstructions. In addition to mimicking human saccadic eye movements, the foveated strategy adapts to motion tracking through the foveal gaze control method. During high-resolution imaging in the fovea area, the maximum sensing area expands 3.14 times, similar to human vision. The proposed retina-like single-pixel imaging has great potential in future applications with the advantages of avoiding complex optics design, low time consumption, and wider vision field. [ABSTRACT FROM AUTHOR]

The security of liveness detection in face recognition is a crucial issue, but many attacks can spoof current face feature techniques. To enhance the security of liveness detection, a method is proposed to extract human physiological components from the object and classify the properties. The proposed method, different from traditional camera-based methods that require specific movement of the human face, separates the heart rate (HR) components from the computational ghost imaging (CGI) signal and achieves liveness detection by capturing only one image rather than image sequences. The correct rate reaches 96.0% against picture attacks and mask attacks. The average error is only 3.57% compared to commercial contact HR measuring devices. Meanwhile, this method is found resolution-independent and can work in low-resolution conditions, which is experimentally verified at a resolution of 32 × 32 pixels. This method can enhance the security of liveness detection and provide a fresh framework for physiological measurements. [ABSTRACT FROM AUTHOR]

Traditional imaging technology is basically a "what you see is what you get" imaging method, providing images that resemble human vision for post-information acquisition and interpretation. This Letter proposes a feature single-pixel imaging technique that allows for direct imaging of specific features without the need for traditional image processing methods. This approach enables the imaging of a single feature at a remarkable ultra-low sampling ratio of 2% with a resolution of up to 128 × 128 pixels, operating at a frequency of 67 Hz, even in dynamic environments where the location of the target or background features may change. Additionally, the proposed method demonstrates the ability to selectively image defects on an integrated circuit wafer. This research offers a significant advancement in the development of single-pixel imaging for feature information acquisition and has immense potential for applications in various industries and daily life scenarios. [ABSTRACT FROM AUTHOR]

The realization of bidirectional deformation function is an important symbol of most natural creatures and intelligent flexible robots. Currently, most soft actuators are developed on the basis of transition between two different states, which means difficulties of control during the whole movement. In this work, variable distribution positions of hard magnetorheological elastomers (H‐MREs) in the matrix are used to achieve different magnetic force distributions. The programmable force distribution promotes different deformations of the magnetic actuators, which enlarges the deformation range by 51.69% under the same magnetic field. Pre‐magnetizing the H‐MREs makes them have a certain residual magnetization. Due to the residual magnetization property of H‐MREs, the magnetized actuator can not only be attracted but also be repelled by the applied magnetic field. This bidirectional deformation capability gives the actuators a wider deformation range and greater clamping force, such as the smart gripper for pinching up object. In addition, the actuators are integrated with a flexible sensing layer with high resolution and strong stability for self‐sensing. This kind of force distribution programmable technology and self‐sensing performance have the potential to broaden the application of actuators in medical equipment requiring high control accuracy. [ABSTRACT FROM AUTHOR]

Soft magnetorheological elastomers (s-MRE) is a kind of smart material mainly fabricated by embedding soft magnetic particles into an elastomer matrix. It can be categorized as isotropic and transversely isotropic, depending on the arrangement of internal magnetic particles. In isotropic s-MRE, magnetic particles are randomly distributed, while transversely isotropic s-MRE forms chain structures for the magnetic particles. Compared with isotropic s-MRE, transversely isotropic s-MRE exhibits more significant magnetically-enhanced mechanical properties, making it highly applicable in the vibration control area. While past theoretical work has mainly focused on the magneto-mechanical coupling behaviour of isotropic s-MRE, less attention has been given to modelling the magneto-mechanical coupling behaviour of transversely isotropic s-MRE. Specifically, understanding the impact of different particle chain-magnetic field spatial locations on the magnetization and magnetic-enhanced viscoelastic behaviour of transversely isotropic s-MRE remains an open topic. To address this research gap, we characterize the quasi-static, viscoelastic and magnetization performance of transversely isotropic s-MRE under different particle chain-magnetic field spatial locations. Subsequently, we develop a novel constitutive model for transversely isotropic s-MRE, integrating magneto-hyperelasticity, magneto-viscoelasticity and magnetization. We then implement the magneto-mechanical coupled model for transversely isotropic s-MRE at a finite element level. Following model calibration and validation, we conduct a case study to demonstrate the model's ability to predict the magneto-mechanical coupling performance of a transversely isotropic s-MRE-based laminated isolator. This model is a valuable tool for predicting the magneto-mechanical performance of transversely isotropic s-MRE-based smart devices, thereby facilitating the design and advancement of transversely isotropic s-MRE in vibration control. • Transversely isotropic s-MRE shows notable magnetic enhanced mechanical properties. • Despite transversely isotropic s-MRE shows a high potential in vibration control area. • There is a lack in modelling its magnetic enhanced viscoelasticity. • We propose a new magneto-mechanical coupled viscoelastic model to fill this gap. • The model reflects the particle chain contribution to its magnetization and mechanics. [ABSTRACT FROM AUTHOR]

A computational ghost imaging encryption and watermarking method with a small key storage space is proposed. This method uses the Arnold transform to rearrange the measurement matrix in the computational ghost imaging (CGI), using the parameters in the transform as encryption/decryption keys. To reduce the risk of key leakage, the independent component analysis (ICA) method is introduced to analyze the CGI signals, making them statistically independent from each other and further increasing the difficulty of cracking. Two watermarking strategies are proposed that can identify illegal data tampering by verifying the integrity of the watermark. The feasibility of this method is verified by both numerical simulations and optical experiments. The research results represent an optical imaging encryption and watermarking technique with multi-images and multi-user characteristics. As its key storage requirements are small, it can be applied to confidential channels with low speeds, such as quantum cryptography. • The method has multi-image, multi-user encryption, and watermarking abilities. • The length of the key is small compared to existing methods. • Illegally tampered signal can be detected without damaging the original image. [ABSTRACT FROM AUTHOR]

Degradation of imaging quality due to noise sources is one of the most essential problems for single-pixel imaging (SPI). This paper presents a method that separates, identifies, and reduces noise from the 1-D signal of the SPI before reconstructing the image. The proposed method raises the quality of the picture significantly, for example, PSNR from 9.14 dB to 30.29 dB and SSIM from 5.55% to 91.99% when SNR is -15 dB in simulation. This method has a strong robustness to a variety of noise types compared to the traditional filtering methods. The experimental results verified the proposed method's feasibility and improved the image's quality from a chaotic state to an acceptable stage. The method proposed in this paper can separate, identify and remove the noise component from the sources in SPI, which may open a branch by removing noise from sources rather than post-processing. • A method to separate, identify, and reduce noise in single-pixel imaging. • Robust to a variety of noise types compared to the traditional filtering methods. • Enhance the imaging quality and expand application of SPI in noisy conditions. [ABSTRACT FROM AUTHOR]

• A deep-hole imaging method by using MMF is proposed. • Wavelet polarization fusion is applied to deep-hole image reconstruction. • The method achieves reconstruction with a maximum spatial resolution of 3.18 lp/mm. Conventional deep hole imaging uses a camera array as the imaging device, with the lens entering the deep hole to obtain spatial light information for reconstruction. The lens often determines the size of the imaging aperture and it is hard to adapt to different sizes of deep holes, especially elongated ones. This paper proposes a method of the multimode fiber(MMF) deep hole imaging based on wavelet polarization fusion, completed with fiber single-pixel imaging(FSPI) and fiber polarization single-pixel imaging(FPSPI). The system completes three different sizes of deep holes imaging, respectively 8mm × 8mm, 5mm × 5mm, 3mm × 3mm. In addition, the information entropy of each 32 pixels image increases 12.26 % and 11.78 % relative to the original image, which is higher than that of 64 pixels images of the same class, with the spatial resolution of 3.18 lp/mm. The proposed deep hole imaging method based MMF is expected to be applied in pipeline sidewall imaging and deep hole 3D imaging. [ABSTRACT FROM AUTHOR]

With the development of the integration and miniaturization of sensing devices, the concept of self-sensing devices has been proposed. A motion state is self-sensed via the structure or integration of an actuator in the construction of a sensing unit. This device is then used to capture the perception and measurement of states such as position, displacement, and speed. A triboelectric nanogenerator converts mechanical energy into electrical energy through the coupling effect of contact generation and electrostatic induction, which represents one of the reliable ways through which to realize integrated sensing. In this world, the power generation technology of the TENG is applied to a sensing device. The sensing characteristics of a grid-like TENG are designed and analyzed in freestanding triboelectric mode. Firstly, a relation model of displacement, velocity, voltage, and charge is established. The charge-transfer increment and current amounts are linearly related to the velocity. The open-circuit voltage has a positive relationship with the displacement. The maximum open-circuit voltage and the maximum charge transfer are fixed values, and they are only related to the inherent parameters of a triboelectric nanogenerator. Next, the sensor model is constructed using COMSOL Multiphysics 6.0. The simulation results show that the relationships between output voltage and charge transfer, as well as those between the increments of charge transfer, velocity, and displacement, are consistent with the results derived from the formula. Finally, a performance test of the designed sensor is carried out, and the results are consistent with the theoretical deduction and simulation. After analysis and processing of the output electrical signal by the host computer, it can feedback the frequency and speed value of the measured object. In addition, the output signal is stable, and there is no large fluctuation or attenuation during the 521-s vibration test. Because the working unit of the sensor is thin filmed, it is small in size, easy to integrate, and has no external power supply; moreover, it can be integrated into a device to realize the self-sensing of a motion state. [ABSTRACT FROM AUTHOR]

The displacement–strain transformation is essential for revealing the internal mechanics of structures and developing strain measurement methods. This transformation typically depends on the environment of the structure. In contrast to the traditional invariant transformation, this paper proposes a method to obtain a variable displacement–strain transformation by self-learning of the modal parameters of the structure in operation. The beam experimental results demonstrate that the transformation is able to take account of different forms of excitation and to obtain strain measurements under sinusoidal and random excitation with up to 99.82% and 99.70% accuracy, respectively. Moreover, these results indicate that the proposed displacement–strain transformation is able to take account of the environmental conditions encountered in practical situations more consistently than conventional approaches. The introduction of a modal-learning displacement–strain transformation in the proposed approach provides a welcome boost to the development of strain measurement methods. [ABSTRACT FROM AUTHOR]

Single-pixel imaging (SPI), which is generally based on computational imaging, has the advantages of a wide bandwidth and the ability to image objects beyond the visual field. However, the major challenge in developing SPI is the large number of illumination patterns that are required. Unlike traditional SPI that relies on random measurement patterns, the SPI method proposed in this letter involves a two-step phase shift that reduces greatly the required number of illumination patterns. Theoretical analysis shows that 6724 illumination patterns are required to reconstruct a 128 × 128-pixel image whose peak signal-to-noise ratio exceeds 30, and these can be projected in 0.3362 s with a digital micromirror device working at full speed. Compared to SPI with a four-step phase shift, half the number of illumination patterns are required. Verification experiments show that the reconstructed images can be obtained even at a sampling ratio of 20%. The proposed SPI with a two-step phase shift is an effective means of requiring fewer illumination patterns and has great potential in dynamic detection. [ABSTRACT FROM AUTHOR]

Harvesting sustainable mechanical energy is the ultimate objective of nonlinear energy harvesters. However, overcoming potential barriers, especially without the use of extra excitations, poses a great challenge for the development of nonlinear generators. In contrast to the existing methods, which typically modify the barrier height or utilize additional excitations, this letter proposes a seesaw-type approach to facilitate escape from potential wells by transfer of internal energy, even under low-intensity excitation. This approach is adopted in the design of a seesaw-type nonlinear piezoelectric energy harvester and the energy transfer process is analyzed by deriving expressions for the energy to reveal the working mechanism. Comparison experiments demonstrate that this approach improves energy harvesting in terms of an increase in the working frequency bandwidth by a factor of 60.14 and an increase in the maximum output voltage by a factor of 5.1. Moreover, the output power is increased by a factor of 51.3, which indicates that this approach significantly improves energy collection efficiency. This seesaw-type approach provides a welcome boost to the development of renewable energy collection methods by improving the efficiency of harvesting of low-intensity ambient mechanical energy. [ABSTRACT FROM AUTHOR]

Vibrational energy harvesters, which are generally based on a single cantilever beam, are mainly effective for excitations perpendicular to the beam. However, typical ambient vibrations are of multifrequency and are multidirectional. To achieve full harvesting of multifrequency vibrational energy in multiple directions, this letter proposes a multidirectional vibrational energy harvester utilizing multimodal vibrations of a double-branched beam that has four natural frequencies below 22 Hz. Comparison experiments in different directions demonstrate an improvement of energy harvesting when this double-branched beam is used. Under horizontal excitation, the maximum open-circuit voltage is increased to 1845%. Under vertical excitation, the average power density is increased over 3800 times. The experimental results indicate that this structural design significantly improves the energy collection efficiency in both horizontal and vertical directions, even with a lighter structural weight. [ABSTRACT FROM AUTHOR]

A recently proposed absolute phase unwrapping method using geometric constraints of the structured light system significantly improves the measurement speed and the robustness. The most important step of this method is to create a minimum phase map as the phase unwrapping reference. Current method usually selects the closest plane as the minimum phase map. However, we found that the position of the minimum phase map is direction-determined and it may induce a fatal error to phase unwrapping under certain circumstances. This letter analyzes the direction-determined phase increasing phenomenon and presents a direction-determined phase unwrapping technique, which includes a new establishment method for the minimum phase map and corresponding phase unwrapping procedures. [ABSTRACT FROM AUTHOR]

Phase-shift profilometry (PSP) holds great promise for high-precision 3D shape measurements. However, in the case of measuring moving objects, as PSP requires multiple images to calculate the phase, the movement of the object causes artifacts in the measurement, which in turn has a significant impact on the accuracy of the 3D surface measurement. Therefore, we propose a method to reduce motion artifacts using feature information in the image and simulate it using the six-step term shift method as a case study. The simulation results show that the phase of the object is greatly affected when the object is in motion and that the phase shift due to motion can be effectively reduced using this method. Finally, artifact optimization was carried out by way of specific copper tube vibration experiments at a measurement frequency of 320 Hz. The experimental results prove that the method is well implemented. [ABSTRACT FROM AUTHOR]

A novel phase unwrapping method with five composite fringe patterns and phase-shifting method was proposed for three-dimensional information detection. The composite fringe patterns were composed of phase-shifted sinusoidal and stair phase-coding fringe patterns. The fringe patterns are five step phase-shifted. The relative phase and the stair code-words can be obtained simultaneously based on the five step phase-shifting algorithm. The monochrome composite structure has the improvement on the measurement speed and has the potential of solving the problem of color coupling and color imbalance. Combined with the modified minimum phase map theory, this method can provide more code-words for the full field measurement. Simulation and experimental results were presented in the final part to verify the flexibility and feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents a low-frequency micro-vibration absorber based on a beam with designable nonlinear stiffness. The material and dimension parameters of the nonlinear characteristics of the beam are discussed by the finite element method (FEM). Based on the nonlinear stiffness characteristics of the beam, the designed micro-vibration absorber has a low-frequency vibration absorption effect and multiple working modes in multiple directions. The effects of structural parameters on the stiffness characteristics of the designed beam are discussed to explore the low-frequency performance. The results of FEM analysis are verified by vibration absorption experiments, and the effectiveness of the low-frequency vibration absorbers is verified by aerospace micro-vibration experiments. [ABSTRACT FROM AUTHOR]

Measurement uncertainty is as important as measurement in metrology and industry. The GUM and its supplements provide a widely accepted framework for evaluating measurement uncertainty; but don't provide a reasonable assessment method for some special circumstances, especially for dynamic measurement. Several emerging methodologies with different mathematical approaches are used for evaluating the dynamic uncertainty in a specific application, such as knowing the characteristics of data. To expand the applicability, a self-adaptive method is proposed. This method evaluates measurement uncertainty by analyzing the compositions of dynamic data, regardless of linearity, stationarity, or stochasticity. Information entropy on spectra combined with EDM algorithms is presented to divide dynamic data into deterministic and stochastic components; and then a Bayesian model and a time-varying auto-regression model are used to analyze decomposed components, respectively. Synthetic noisy signals and experimental data from a double-rotor table are utilized to demonstrate the effectiveness of the proposed method. • A self-adaptive method for evaluating dynamic measurement uncertainty is developed. • A criterion is presented to separate deterministic component from stochastic component. • The developed method can be used to improve the precision of dynamic measurement. [ABSTRACT FROM AUTHOR]

• An image-free method for monitoring microfluidics device is proposed. • The data throughput of the proposed method is extremely low. • Real-time processing is available for the method. • The method achieves both high frame rate and long duration monitoring. Currently image-based optical measurement methods are the main approaches for detecting and tracking the movements of droplets or particles in microfluidic devices. However, the massive image data throughput and high computational consumption of image processing have become challenges to achieve real-time and long-term monitoring. Here a single-pixel tracking system is proposed to monitor the microfluidic device on the basis of single-pixel imaging and microscope technology without image reconstruction. The experimental results of tracking droplet in microfluidic device demonstrate that the proposed system have unique potential advantages in dynamic tracking for microfluidic devices. The data throughput of the proposed method is 1/792 of image-based methods and can reach an equivalent frame rate of 312.5 Hz with a low computational consumption of 89.3 μs per frame. The proposed image-free tracking method provides a welcomed boost to the further development of microfluidic device monitoring and indicates a potential way to real-time and long-term monitoring without image processing. [ABSTRACT FROM AUTHOR]

The modal-learning displacement–strain transformation has been proved to be able to predict the strain of the typical uniform beam. However, as the complexity of the structure increases, for example, the shape of the beam cross-section changes. The typical displacement–strain transformation is no longer applicable due to the unknown mode function. To further explore this issue, the hypergeometric and Meijer-G functions are used to establish the mode shape function with good structural adaptability. A displacement–strain transformation method based on the hypergeometric and Meijer-G functions is proposed to predict the dynamic strain of the variable cross-section beam. Experiment results demonstrate that the proposed method can solve the problem of full-field strain prediction for beams with variable sections and boost the displacement–strain transformation's theoretical calculation accuracy. Under sinusoidal excitation and random excitation, the strain prediction accuracy reaches 99.69% and 99.25%, respectively. This approach simplifies the preprocessing of the structure, and provides a welcome boost to developing the displacement–strain transformation method in full-field strain measurement. • A displacement-strain transformation method is proposed to predict the full-field dynamic strain of variable cross-section beams. • The mode function of the variable cross-section beam with good structural adaptability is established. [ABSTRACT FROM AUTHOR]

• This array achieves increasing the number of stable states exponentially. • It widens the working frequency bands and enhances the power density significantly. • It obviously improved the harvesting efficiency in non-resonant frequency bands. • The poly-stable method can be applied to other harvesters in engineering structures. [Display omitted] Harvesting the ambient broadband vibrational energy is the ultimate objective of multi-stable vibration energy harvesters. The potential energy of a multi-stable system has more potential wells corresponding stable equilibrium states than a linear energy harvester, and the lower excitation energy is required to overcome the potential barriers to broaden the working bandwidth. However, for traditional multi-stable harvesters, increasing the number of stable equilibrium states to improve energy harvesting efficiency in random frequency bands is difficult. Without the need of external magnets generating static magnetic field, we propose an annularly-distributed poly-stable array which makes stable equilibrium states grow exponentially in maximum number. The experiments indicate that, comparing with a corresponding linear energy harvester, the working frequency bandwidth widened to 283%, the power density increased by a factor of 577 and the electric field energy raised to 133%. The proposed array shows the superiority in broadband vibrational energy harvesting and provides a solution collecting the abundant energy renewable in nature. [ABSTRACT FROM AUTHOR]

• A novel approach to balance the speed and accuracy of the reconstruction of Fringe Projector Profilometry (FPP). • The approach is realized by the speckle matching function designed instead of phase unwrapping to improve the matching speed. • Through the cyclic method, it is equivalent to achieve reconstruction with one picture High-speed and high-accuracy measurement is the ultimate objective of fringe projection profilometry(FPP). However, improving measurement speed, especially without the reduce of measurement accuracy, poses a great challenge for the development of FPP. In contrast to the existing methods, which typically use phase unwrapping method, this paper proposes a high-speed and high-accuracy FPP without phase unwrapping. This approach is a specially designed speckle matching function based on digital image correlation, instead of phase unwrapping, to improve the matching speed. At the same time, the binary defocusing method can speed up the projection speed and the cyclic method can reduce the total number of gratings needed for reconstruction. In order to improve the accuracy, six-step phase shift method is used instead of the three-step phase shift method. Dynamic 3D measurement experiments demonstrate that this approach realizes high-speed measurement by 320 fps and high-accuracy measurement by a mean standard deviation of approximately 45 μ m. This approach provides a welcome boost to the development of high-speed and high-accuracy FPP. [ABSTRACT FROM AUTHOR]

• This paper proposes an approach that uses single pixel imaging to obtain images with light interference removed for improving OCR recognition rate without image post-processing. • It is the first time that single pixel imaging is proposed to remove light interference for improving the character recognition rate to the best of the authors' knowledge. • When the character recognition rate of the picture obtained by traditional imaging is 0% by adding a serious interference pattern, the counterpart by single pixel imaging is 95.45%. Optical Character Recognition (OCR), which is generally based on figure recognition, is mainly effective for extracting text from pictures. However, it is a challenge to maintain a high recognition rate without being affected by light interference in a complicated environment. To reduce the light interference for improving the OCR recognition rate, this article proposes a method utilizing single-pixel imaging to obtain images without light interference for character recognition. Unlike the traditional CCD/CMOS-based imaging relying on image post-processing to eliminate interference, the method proposed without the need of any image post-processing which is a cumbersome process and often leads to a deterioration in the quality of the obtained images. Theoretical analysis shows that single-pixel imaging can eliminate the light interference in certain conditions completely. The verification experiments demonstrate that single-pixel imaging can only image the target and ignore an introduced highlighted stripe, whereas traditional CCD/CMOS-based imaging can not eliminate the effects of the stripe without image post-processing. Comparison experiments in contrast with the character recognition rate of the picture obtained from traditional imaging demonstrate the counterpart obtained from single-pixel imaging increased from 88.64% to 97.73%. The evaluation index of correlation and image quality illustrates that the picture obtained by single-pixel imaging has a higher correlation with the target picture and better image quality than the counterpart of the picture obtained from traditional imaging. When the character recognition rate of the picture obtained by traditional imaging is 0% by adding a serious interference pattern from a projector, the counterpart by single-pixel imaging is 95.45%. This approach provides a welcome boost to the development of the application of single-pixel imaging in character recognition by reducing the light interference, which provides a potential direction for the development of OCR to obtain higher recognition success rate under a complex environment. [ABSTRACT FROM AUTHOR]

Microscopic imaging is of great significance for medical diagnosis. However, due to the strong scattering and absorption of tissue, the implementation of non-invasive microscopic imaging is very difficult. Traditional single-pixel microscopes, based on reflective optical systems, provide an alternative solution for scattering media imaging. Here, the single-pixel microscope with transmissive liquid crystal modulation is proposed. The microscopic ability of the proposed microscope is calibrated. The multi-spectral microscopic imaging of the object is demonstrated. The transmissive imaging of the object behind the scattering media is analyzed. The proposed prototype of the transmissive single-pixel microscope is expected to be applied in microscopic imaging through scattering media and medical imaging. [ABSTRACT FROM AUTHOR]

• An in-situ self-calibration method for full-field strain measurement is proposed. • The proposed method is also applicable to other displacement measurement methods. • The full-field displacement and strain information can be obtained simultaneously. Online calibration is important for strain measurement especially for non-contact full-field strain measurement. A self-calibration method based on modal expansion and strain–displacement relationships is developed for full-field strain measurement. The proposed method has the capability to calibrate the in–situ measured data with ground truths continuously without shutting down the test equipment. To validate the methodology for strain calibration, a simulated beam, and a cantilever beam under sinusoidal and random excitations are investigated. The post-calibrated strain of the simulated beam is better agreement with ground truths, and the TRAC ε at three points are greater than 99%. The post-calibrated strain the by videometric method, is consistent with measured data using strain gauges. And the accuracy of post-calibrated strain under sinusoidal or random excitation, is higher than that of the pre-calibrated strain. The results of experiments indicate that the proposed method is effective for calibrating strain obtained by visual measurement methods. [ABSTRACT FROM AUTHOR]

Real-time computational ghost imaging (CGI) has received significant attention in recent years to overcome the trade-off between long acquisition time and high reconstructed image quality of CGI. Inspired by compound eyes, we propose a parallel computational ghost imaging with modulation patterns multiplexing and permutation to achieve a faster and high-resolution CGI. With modulation patterns multiplexing and permutation, several small overlapping fields-of-view can be obtained; meanwhile, the difficulty in alignment of illumination light field and multiple detectors can be well resolved. The method combining compound eyes with multi-detectors to capture light intensity can resolve the issue of a gap between detector units in the array detector. Parallel computation facilitates significantly reduced acquisition time, while maintaining reconstructed quality without compromising the sampling ratio. Experiments indicate that using m × m detectors reduce modulation pattern count, projector storage, and projection time to around 1/m2 of typical CGI methods, while increasing image resolution to m2 times. This work greatly promotes the practicability of parallel computational ghost imaging and provides optional solution for real-time computational ghost imaging. [ABSTRACT FROM AUTHOR]

Distributed energy sources, for example the ambient broadband vibrations, are of great importance for the development of the Internet of Things. However, for multistable vibrational energy harvesters, increasing the number of stable equilibrium states to broaden working frequency bands is very difficult. Here we present a poly-stable vibrational energy harvesting approach capable of achieving an exponentially growing maximum number of stable equilibrium states. Unlike the traditional multistable harvesters relying on an external static magnetic field, the nonlinear dynamical behaviours achieved by the proposed approach are synergetic poly-stable motions without the need of external magnets. Comparison experiments in contrast with a linear harvester demonstrate the working bandwidth widened by a factor of 41.0, the power density increased to 760% and the electricity generation raised to 178%. This demonstration of new multistable energy harvester expands the approach to achieving multistable motion and provides a new design philosophy for nonlinear vibrational energy harvesters. Vibration is a promising source of renewable energy, but to be of use it must be efficiently converted into electrical energy. In this paper, the authors propose a poly-stable energy harvesting approach for achieving synergetic multistable vibration which does not rely on external magnetic fields. [ABSTRACT FROM AUTHOR]

Capturing details of objects beyond the focal plane is challenging due to the limited depth-of-field (DoF) of optical systems. Here, we report a computational refocusing ghost Imaging (CRGI) method to extend the DoF of computational ghost imaging (CGI) systems. An ultra-fast and in situ point spread function (PSF) estimation method is put forward utilizing the optical characterization of the system and compressive sensing modulation. The PSF distribution is measured with in situ compressive sensing algorithm according to reciprocity property using the same CGI system. The convolution of PSFs of various depths with modulation patterns is reshaped into measurement matrices to computationally refocus objects at different depths. From one measurement, CRGI can rebuild distinct and well-focused images of multiple objects at different depths. According to experiments, CRGI can nearly quadruple the DoF of typical CGI methods. CRGI represents a significant advancement in CGI domain by computationally surpassing the optical DoF limitations. This discovery enables recording object features beyond the focus plane using extended depth-of-field. [ABSTRACT FROM AUTHOR]

The global health crisis of bacterial resistance to antibiotics requires innovative antibacterial strategies. One promising solution is the exploitation of multifunctional nanoplatforms based on non-resistant antibacterial mechanisms. This work reports a novel Fe3O4@Au/polydopamine (PDA) nanodurian with excellent photothermal-magnetomechanic synergistic antibacterial effects. The one-step formed Au/PDA hybrid shell provides good photothermal properties and spiky surfaces for enhanced magnetomechanic effects. Upon near-infrared (NIR) irradiation, the Fe3O4@Au/PDA nanodurian (200 μg mL−1) achieved nearly 100% antibacterial effect against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The efficiency of photothermal antimicrobial activity was further enhanced by the application of a rotating magnetic field (RMF), with the sterilization efficiency being increased by up to more than a half compared to the action alone. Interestingly, the size of the nanodurian has a significant impact on the synergistic sterilization effect, with larger particles showing a superior performance due to stronger chain-like structures in the magnetic field. Finally, the Fe3O4@Au/PDA nanodurian also demonstrates effective biofilm removal, with larger particles exhibiting the best eradication effect under the photothermal-magnetomechanic treatment. Overall, this magnetic field enhanced photothermal antibacterial strategy provides a promising broad-spectrum antimicrobial solution to combat bacterial infections. Thus, it possesses great potential in future nanomedicine and pollution treatment. [ABSTRACT FROM AUTHOR]

A robust and rapid camera calibration method is essential in vision measurement. This paper proposes a camera calibration method using a 2.5-D coding target that requires just a single captured image and is capable of identifying the intrinsic and extrinsic parameters of a camera system simultaneously. The calibration target consists of four fixed planes to which coded patterns are attached. The fixed planes of the target prevent the ill condition that arises in Zhang’s method, and they provide four different homography matrices at the same time. The extrinsic parameters of the cameras are calculated using the geometric constraints of the feature circles on each plane. The coded pattern allows the four planes to be distinguished automatically. The proposed method is first verified by comparison experiments with three classical calibration methods. The results confirm that the proposed method has the greatest accuracy and smallest variance of errors. The influences on the calibration results of geometric parameters such as the dihedral angle and the area ratio of the feature circles are then investigated by systematic experiments. This proposed camera calibration method using a single captured image represents a breakthrough in a camera calibration technology and has a broad potential for application to machine vision and vision measurement. [ABSTRACT FROM AUTHOR]

Considered the promising anode material for next‐generation high‐energy lithium‐ion batteries, SiOx has been slow to commercialize due to its low initial Coulombic efficiency (ICE) and unstable solid electrolyte interface (SEI) layer, which leads to reduced full‐cell energy density, short cycling lives, and poor rate performance. Herein, a novel strategy is proposed to in situ construct an artificial hybrid SEI layer consisting of LiF and Li3Sb on a prelithiated SiOx anode via spontaneous chemical reaction with SbF3. In addition to the increasing ICE (94.5%), the preformed artificial SEI layer with long‐term cycle stability and enhanced Li+ transport capability enables a remarkable improvement in capacity retention and rate capability for modified SiOx. Furthermore, the full cell using Li(Ni0.8Co0.1Mn0.1)O2 and a pre‐treated anode exhibits high ICE (86.0%) and capacity retention (86.6%) after 100 cycles at 0.5 C. This study provides a fresh insight into how to obtain stable interface on a prelithiated SiOx anode for high energy and long lifespan lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

In practical application environments, objects are rarely stationary, which makes it difficult to image dynamic objects with conventional single-pixel imaging (SI) techniques. In this paper, a rotationally synchronized single-pixel imaging (RS-SI) method is proposed to image a dynamic object in rotation. The modulation pattern rotates in sync with the rapidly rotating object, and the center of object rotation is ensured to be in line with the center of the illumination pattern. Then, RS-SI reconstruction algorithm is used to reconstruct the image of the rotating object by collecting the light reflected from the object's surface. This method does not require advanced knowledge of the object rotation speed to complete the imaging. Simulation and experimental results confirm that the RS-SI can reconstruct images of an object at rotational speeds up to 422.0 rpm and can also complete imaging of a variable-speed rotating object. Imaging results of 128 × 128 pixels at a sampling rate of 27.47% can be obtained with high fidelity. The proposed RS-SI is a method for imaging an object in rotation, providing insights for future applications of single-pixel imaging technology for defect detection in rotating parts. [ABSTRACT FROM AUTHOR]

The code-based method is one of the frequently adopted fringe projection profilometry techniques because of its robustness and high speed. However, the abnormal jump errors caused by the misalignment between the wrapped phase and the fringe order impact the phase unwrapping quality and are more serious in binary defocusing measurement with significant defocusing. This paper proposes a self-alignment technique (SAT) with high speed, no additional patterns, and no accuracy loss to eliminate such jump errors. After analyzing the relation between the grating changes and the misalignment, we designed an assist-code that can perfectly align with the wrapped phase even in significant defocusing. After that, this assist-code is used to adjust the misalignment and eliminate the jump errors. The comparison between the median filter and the proposed SAT method in simulations and experiments demonstrates that the proposed SAT method has the ability to completely remove jump errors for complex textures and step-height objects, even in significant defocusing, indicating its potential to be applied to other phase unwrapping fields, e.g., color-based methods with color coupling problems. [ABSTRACT FROM AUTHOR]

Soft actuators with good flexibility, high stability, and excellent controllability have attracted extensive attention. However, dual‐modal smart self‐perception actuator with contact and noncontact actuating mode remains a challenge. Notably, soft actuators with in situ self‐sensing monitoring capabilities have gained increasing attention in smart flexible devices. This work reports a smart actuator composed of polydimethylsiloxane (PDMS)/magnetorheological elastomer (MRE)/Ag/ polyimide (PI) (PMAP), which can not only well respond to bending stimuli but also be actuated by electromagnetic dual‐modal actuation. Benefiting from the nanowire–nanoflake coupling structure of conductive Ag layer, the PMAP film exhibits excellent electrical sensing and electro‐heat generation behavior. The ΔR/R0 of PMAP film increases from 5.1% to 24.7% during the bending test. Moreover, the PMAP film realizes contact electrothermal actuation due to the mismatch of thermal expansion coefficient between PDMS matrix and PI tape. Under applying a 16 s of 2 V electrothermal actuation, the bending angle of PMAP film can increase from 31.1° to 219.3°. Moreover, MRE matrix endows the PMAP film with noncontact magnetic deformation characteristic. This multifunctional smart flexible device integrated with in situ sensing perception and contact and noncontact dual‐modal actuation performances possess high potential in electronic devices and robots. [ABSTRACT FROM AUTHOR]

• An lens-flare-free computational imaging method is proposed. • The data throughput of the proposed method is low. • Video frame-rate imaging is available for the method. Lens flare, the photographic artifact produced by reflecting and scattering a powerful incident light within a camera lens group, can severely degrade image quality and mislead the image-based processing task. Existing solutions typically depend on sophisticated optics design or complex image postprocessing algorithms to reduce lens flare. This paper demonstrates a direct reconstruction of the target feature by single-pixel imaging with a simple optics design and no image postprocessing. A novel sampling strategy is proposed for spacecraft docking, which utilizes Fourier single-pixel imaging methods to capture a specific feature at an ultralow sampling ratio. Simulation and experiments demonstrate that the proposed method can image the feature with a sampling ratio of 4.8% at a video frame rate while almost eliminating the impact of the ring effect. This paper provides a new perspective for achieving lens-flare-free, video-framerate and low-data-throughput imaging in space tasks, which has potential in many imaging-based applications. [ABSTRACT FROM AUTHOR]

Inspired by creatures reducing impact damage, a novel semi‐active protection strategy to enhance impact resistance through structural adjustment is proposed. The heat‐activated shape memory composites (PCLE) consisting of polycaprolactone (PCL) and shear stiffening elastomer are first prepared. The PCLE with 50 wt.% PCL (PCLE‐50%) presents tensile strength of 0.46 MPa, fracture strain of 148%, high shape fixity and recovery rates (97.9% and 91.1%), and stable shape‐memory repeatability. Furthermore, various PCLE‐50%‐based structures are fabricated, which show reinforced anti‐impact performance after shape‐shifting. Loading from 300 mm, the maximum drop hammer impact force of no protection, PCLE‐50%, and deformed assembled single‐branch structure are 3.98 kN, 1.75 kN, and 0.93 kN, respectively. Additionally, assembled complex structures also exhibit exceptional energy absorption properties. Ultimately, intelligent clothing is successfully manufactured. Besides good anti‐impact effect, the clothing shows excellent thermal insulation capabilities whose surface temperature is 31.7 °C after heating for 600 s at 42 °C. This study provides an innovative means to develop deformable, wearable, and intelligent protective devices. [ABSTRACT FROM AUTHOR]

We obtained three types of particles with different surface characteristics, including solid silica with smooth surface and no surface group (SiO 2), mesoporous silica with rough surface and no surface group (M−SiO 2) and mesoporous silica with rough surface and surface silicon hydroxyl groups (M−SiO 2 (–OH)). Compared with SiO 2 , M−SiO 2 and M−SiO 2 (–OH) have higher friction between particles due to rough surfaces, and there is adhesion force between M−SiO 2 (–OH) particles due to the presence of hydroxyl groups on the surface. The schematic phase diagram of the ϕ - γ ̇ for three types of particles shows the difference of rheological property. [Display omitted] • The influence of surface characteristics on the suspensions was explored. • The roles of friction and adhesion forces on the suspensions were evaluated. • The ϕ - γ ̇ phase diagram was present to demonstrate the rheological difference. The surface characteristic of suspended nanoparticle is an extremely important property for the non-Newtonian behavior of shear thickening suspensions. Easy access to distinct surface characteristics and a deep understanding of the role of friction and adhesion forces remains challenging yet critical to study the suspension performance. In this work, by synthesizing mesoporous silica with different surface roughness and groups, the influence of surface characteristics on the non-Newtonian behavior of suspension is comprehensively explored. The results show that the suspensions containing particles with rough surface and hydroxyl groups on the surface have higher shear thickening power, lower critical shear rate, lower discontinuous shear thickening transition fraction and lower jamming fraction. Furthermore, the test of the first normal stress difference N 1 shows that the interparticle friction and adhesion both reduce the critical volume fraction of the transition from fluid lubrication dominance to frictional contact dominance in the suspension. This finding deepens the understanding of phase transformation mechanism, and open an approach to accelerate the advanced shear thickening suspensions design for next-generation intelligent materials. [ABSTRACT FROM AUTHOR]

Kirigami structures are increasingly popular in wearable devices due to their exceptional properties. However, their mechanical robustness and anti-impact properties during structural deformation have been overlooked. This study addresses this issue by introducing defects on the surface of composites, mimicking pangolin scales to produce negative Poisson's ratio deformation during tensile strain. Kevlar, conductive shear stiffening elastomer (c-SSE), and PET are combined (Kiri-Kevlar). When subjected to impact, the subconscious rapid response of humans leads to bending arms or curling up, causing Kiri-Kevlar assembled at joints to stretch and undergo structural deformation. The Kiri-Kevlar deformation and high energy dissipation characteristics of c-SSE effectively resist external impact. In summary, a functional-integrated wearable device is developed based on a bionic kirigami structure, realizing efficient anti-impact and providing ideas for a new generation of human-computer interactive intelligent protection devices. When the pangolin assumes a defensive posture, the scales on its body unfold like pine cones. When the human body falls and subconsciously makes a defense, the strain of the joints can deform the paper-cut structure, so as to effectively resist the impact. [Display omitted] • Kevlar, shear stiffening elastomer and PET are combined by hot pressing method. • Based on pangolin bionics, composite with anti-impact property was developed. • The structural deformation of composite occurs with body under subconsciousness. • Structured composite can efficiently dissipate impact force to provide protection. • Human-computer interaction is realized through electromechanical performance. [ABSTRACT FROM AUTHOR]

The solar cell is key photovoltaic (PV) device that converts light energy into electricity, and its surface defects are the main reason for the decrease in the efficiency of PV systems. Conventional solar cell defect detection methods are often interfered with by cell substrates and are difficult to detect under high reflection, especially the overlap of substrates and defects. A solar cell defect detection method based on Fourier single-pixel imaging (FSI) is proposed to distinguish periodic substrates and defects in reconstruction by projecting illumination patterns with Fourier fringes, in which the removal of substrates reaches 100%. Meanwhile, for the high reflection present on the solar cell surface, the solar cell is directly treated as a single-pixel detector, which is free from interference from ambient light. The experiment adopts the solar cell itself as an imaging device under highly reflective conditions and removes the interference of the cell substrate by a 4-step phase-shifted FSI reconstruction algorithm to achieve the extraction of four types of defects, each of which is located in a different position of the solar cell substrate, at 10%, 50%, and 100% sampling rates. The method described here complements existing solar cell defect detection approaches and may be applied to enhance photovoltaic testers that rely on real-time correlation measurements, with promising applications in chip inspection and medical cell imaging. • Fourier single-pixel imaging(FSI) method for solar cells defect detection. • By using the solar cell as a photodetector(PD) to avoid the interference of high reflections. • Periodic substrate removal by 4-step phase-shift-based FSI reaches 100% in four different types of defects. [ABSTRACT FROM AUTHOR]

Although high-resolution single-pixel imaging (SPI) can be achieved by under-sampling, low sampling ratio (SR) strategies often result in a loss of image details and lower image quality. Due to the limited memory of the spatial light modulator (SLM) and the time necessary to load such vast numbers of patterns, high-resolution SPI at high sampling rates has not yet been realized. In this work, we propose a one-dimensional single-pixel imaging (1D-SPI) technique to reconstruct high-quality images that can even surpass the full resolution of the SLM at 100% sampling ratio with extremely low data throughput. Only nearly one-thousandth as many modulation patterns as traditional 2D modulation methods are required, which significantly reduces the demand for massive memory capacity and the time to load these patterns. A 1540 × 1024 resolution SPI image is successfully demonstrated experimentally, indicating its tremendous promise in applications such as industrial inspection and satellite remote sensing. • A SPI method that can exceed resolution of spatial light modulators is proposed. • A High-resolution SPI is realized with very low data throughput. • High-quality SPI results are reconstructed at 100% sampling ratio. [ABSTRACT FROM AUTHOR]

Soft magnetic actuators with programmable structure design and controllable deformation ability based on 3D printing technology have attracted extensive attention. In this paper, a novel 3D printing strategy is developed to manufacture the ultraflexible magnetic actuator, in which the printed material is composed of magnetic particles and thermoplastic rubber materials. Different from the traditional fused deposition printing, this printing strategy introduces screw extrusion technology to the heating components of the printer to overcome the problem of filament buckling in the flexible material. Thus, the tensile modulus of the printed products can be reduced to as low as ≈2 MPa. Based on the above method, biomimetic magnetic actuators of the sucker and the pump are constructed for adhering and releasing object and pumping liquid. The contraction performance of the magnetic actuator is studied via a series of experiments and the magnetic field‐induced deformation is analyzed by the multiphysics‐based finite element model. This work proves that ultraflexible magnetic actuators fabricated by this 3D printing strategy show broad prospects in the fields of soft robotics and bionics. [ABSTRACT FROM AUTHOR]

A multifunctional shear thickening gel (MSTG) with both shear thickening performance and magnetorheological effect was prepared by dispersing the carbonyl iron powder into shear stiffening polymer matrix. Upon varying the mass ratio of pyroboric acid to polydimethylsiloxane from 0 to 0.6, the relative shear thickening effect of MSTG first increases and then decreases, demonstrating an excellent shear thickening property between the ratio within 0.2–0.4. A molecular chain model of the cross-linked bond was proposed to illustrate the shear thickening mechanism, and verified by the impact test of MSTG with different proportions. It is believed that more cross-linked bonds were formed at a higher external impact velocity due to the stimuli-response performance of MSTG. [Display omitted] • Variation rules of ST effect and chain model of MSTG were put forward. • The chain model was verified by the impact test of MSTG. • An optimization method was proposed to obtain higher shear thickening effect. • Energy dissipation values of MSTG at distinct impact velocities were simulated. [ABSTRACT FROM AUTHOR]

By encapsulating shear thickening fluid (STF) in Ecoflex-0030, a kind of composite structure with excellent anti-impact and high energy absorption properties was obtained. The drop hammer tests indicated that the increase of STF concentration could improve the anti-impact and energy absorption capacity of STF/Ecoflex. Furthermore, the loss rate of impact energy of STF/Ecoflex was 63.6% and 36.6% higher than that of aluminum alloy and Kevlar materials, respectively. Numerical simulation was used to explore the mechanism. It was found that the shear thickening effect of STF was enhanced with the increase of STF concentration, which could lead to the increase of the stress level of STF and the energy dissipated by friction and viscosity, thereby the anti-impact performance of the composite was improved. Then, the C-STF/Ecoflex was prepared by adding carbon nanotubes (CNTs) to STF, which had excellent impact sensing function and could be combined with Kevlar for multi-functional wearable devices with anti-impact properties. • The STF/Ecoflex composites with excellent anti-impact and high energy absorption properties were prepared. • The effects of STF concentration on energy absorption and impact resistance of STF/Ecoflex were analyzed. • The anti-impact mechanism for STF on the STF/Ecoflex was revealed by the finite element analysis (FEA). • The C-STF/Ecoflex with good impact sensing function was obtained, which could be used for wearable devices. [ABSTRACT FROM AUTHOR]

• We propose a single-pixel superposition compound eye (SPSCE) that deploys a photodetector which has no spatial resolution and imitates the rhabdom in natural organisms to deliver super-resolution imaging signal, which creates a new branch for the compound eyes. • SPSCE has the capacity to improve the imaging resolution two orders of magnitude than the number of ommatidia without subsequent image processing. • SPSCE has the unique super-robust character to capture whole acceptable images even if almost one-third of ommatidia are not working, and obtain images beyond the actual visual field of the target without observing directly. Deep understanding of biological superposition compound eye provides great opportunities in developing imaging systems with features beyond current planar detector array based imaging devices. However, artificial superposition compound eyes are designed on the basis of a planar detector array and that subsequently leads to the complex optical design and degradation of imaging quality inevitably. We propose a single-pixel superposition compound eye (SPSCE), whose imaging resolution has been improved two orders of magnitude than the number of ommatidia without subsequent image processing. SPSCE has the ability to capture the whole acceptable image of objects even if almost one-third of ommatidia at random positions are not working, which makes it possible to operate reliably even in the damaged state. SPSCE has the capacity to image beyond the actual visual field of the target without observing directly. With only one lateral sub-eye working and deviating from the visual field of the target by 20. 41 ∘ , SPSCE obtains the complete and recognizable image of the target independently through the diffuse reflection optical information of the surrounding environment. The unique super-robust character of SPSCE with its super-resolution property contributes to developing anti-interference artificial compound eyes, unlocking the limit toward development of much higher imaging resolution artificial superposition compound eyes. [ABSTRACT FROM AUTHOR]

Single-pixel imaging technology is popular with invisible wavelengths and low light environments. However, the time-consuming steps hindered the development of single-pixel imaging technology. To improve imaging efficiency, a high-efficiency one-step single-pixel imaging method based on the discrete Hartley transform is proposed. The proposed method does not require a large number of fringe patterns and only requires a real-number calculation. The number of fringe patterns required for the proposed method is only half of that required for the four-step phase-shift Fourier method at the same sampling rate. Although a one-step method, it also uses the idea of differential measurements and adds upsampling processing strategies, which simultaneously improve the signal-to-noise ratio of the recovered image. The simulation shows that the peak signal-to-noise ratio and structural similarity index of the recovered target scene exceed 20 dB and 80%, respectively, when the sampling rate is 30%. Only 20 164 patterns are needed to reconstruct a (256 × 256)-pixel image. After defocusing the gray stripe pattern into a binary pattern, it only takes milliseconds to project these patterns into the target. It can be seen that the experimental results of the proposed method are significantly better than those of the two-step phase-shift method under dramatical noise interference. With the rapid development of advanced equipment, this method will represent significant progress in the real-time reconstruction of single-pixel imaging. [ABSTRACT FROM AUTHOR]

High nuisance alarm rates and missing alarm rates in phase-sensitive optical time-domain reflectometer (ϕ -OTDR) greatly restrict their practical application. In this paper, an asynchronous sampling pulse width multiplexing ϕ -OTDR is proposed to reduce both of these rates. Intersection and inclusion relationships among multiple positioning intervals are used to optimize the positioning accuracy. We construct an eight-pulse-width multiplexed ϕ -OTDR system and adopt a multisensor information fusion algorithm to verify the feasibility of the method. The experimental results show that this method can reduce the missing alarm rate by 93% and the number of nuisance alarms by 97%. The average positioning accuracy of the system is 21.4 m, which is equivalent to the spatial resolution level corresponding to the minimum pulse width in the optical pulse sequence. The positioning accuracy of some groups was as low as 6.4 m, far less than 20m. The proposed method provides a simple and feasible new approach for reducing nuisance alarm and missing alarm rates and optimizing the positioning accuracy of ϕ -OTDR. • A pulse width multiplexing Φ -OTDR with asynchronous sampling structure is proposed. • The nuisance and missing alarm rates of Φ -OTDR can be reduced by 93% and 97%. • The average accuracy of asynchronous sampling PWM Φ -OTDR can be optimized to 21.4 m. • The accuracy is determined by the relationships among multiple positioning intervals. [ABSTRACT FROM AUTHOR]

Vibrations often cause visual fatigue for drivers, and measuring the relative motion between the driver and the display is important for evaluating this visual fatigue. This paper proposes a non-contact videometric measurement method for studying the three-dimensional trajectories of the driver's eyes based on stereo vision. The feasibility of this method is demonstrated by dynamic calibration. A high-speed dual-camera image acquisition system is used to obtain high-definition images of the face, and the relative trajectories between the eyes and the display are obtained by a set of robust algorithms. The trajectories of the eyes in three-dimensional space are then reconstructed during the vehicle driving process. This new approach provides three-dimensional information and is effective for assessing how vibration affects human visual performance. [ABSTRACT FROM AUTHOR]

A pulse-width multiplexing method for reducing the nuisance-alarm rate of a phase-sensitive optical time-domain reflectometer (ϕ -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 ϕ -OTDR data are observed. Furthermore, by utilizing the SNR as the feature in a feature-layer algorithm based on Dempster–Shafer evidential theory, a four-pulse-width multiplexing ϕ -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. [ABSTRACT FROM AUTHOR]

The limited load capacity and power resources of small-scale fixed-wing drones mean that it is difficult to employ internal high-precision inertial navigation devices to assist with the landing procedure. As an alternative, this paper proposes an attitude measurement system based on a monocular camera. The attitude angles are obtained from a single captured image containing five coded landmark points using the radial constraint method and three-dimensional coordinate transformations. The landing procedure is simulated for pitch angles from −15 ∘ to −40 ∘ , roll angles from −15 ∘ to +15 ∘ and yaw angles from −15 ∘ to +15 ∘ . For roll and pitch angles of approximately 0 ∘ and −25 ∘ , respectively, the accuracy of the method reaches 0.01 ∘ and 0.04 ∘ . This UAV attitude measurement system obtains an attitude angle by a single captured image, which has great potential for assisting with the landing of small-scale fixed-wing UAVs. [ABSTRACT FROM AUTHOR]

Multimode fiber (MMF) imaging based on compressive sensing (CS) is a promising technique for ultrathin endoscopic applications due to its advantages such as small size, low cost, and high speed. However, how to choose the most suitable MMF in the application has not been analyzed in detail. In this paper, the influences of fiber core diameter on the quality of CS MMF imaging are investigated theoretically and experimentally. Firstly, the relationship between the core diameter of MMF and the speckle size of its output speckle patterns is established. Then the speckle patterns with different speckle sizes are synthesized to explore their impact on imaging quality. Results show that a MMF with a larger core diameter yields better image quality in ideal conditions, while the most suitable core diameter decreases with the increasing noise or/and declining sampling rate. Finally, an experimental platform is built to verify the simulation, the same trends between experimental results and simulation results validate the feasibility of the simulation method. This paper provides a reference on how to choose a more suitable MMF to obtain a high-quality image in practical applications. • Impact of core diameter on the quality of multimode fiber (MMF) imaging is studied. • In ideal conditions, MMF with a larger core diameter yields better image quality. • With the increasing noise, the optimal core diameter of MMF decreases. • With the declining sampling rate, the optimal core diameter of MMF decreases. • The study provides a reference on selecting suitable MMF for ultrathin endoscopes. [ABSTRACT FROM AUTHOR]