Output End Research Articles

Acquiring sequentially time-resolved two-dimensional images with parallel multi-group sampling strategy

A method of acquiring sequentially time-resolved two-dimensional images with parallel multi-group sampling strategy has been developed. In this technique, the two-dimensional image was sampled and transferred by a fiber bundle, the fibers of which were arranged in two-dimensional arrays in the input end and rearranged in four one dimensional lines in the output end. The output four groups of one-dimensional images were parallelly detected by a streak camera. The recorded images of the streak camera were then reconstructed according to the spatial relationship of the fibers between the input and output ends to obtain sequentially time-resolved two-dimensional images. The fiber bundle was composed of 64 × 64 pixels in the input end and four columns of 1 × 1024 pixels in the output end. Each pixel consisted of 4 × 4 fibers. The imaging system with about 10 ps temporal resolution has been applied for observing the flight of light, indicating that this technique can be a promising tool for investigating ultrafast phenomena.

Insight into the acceleration effect of current-carrying condition on copper conductor atmospheric corrosion

Copper is widely used as conductive components in transmission lines, facing severe corrosion risks. The current passing through copper conductors will significantly affect its corrosion process, yet there is a lack of detailed study on the corrosion mechanism under this specific condition. Thus, this study investigated the effect of direct current current-carrying (DC C-C) conditions on the atmospheric corrosion behavior of copper conductors under thin electrolyte layer (TEL) through electrochemical measurements and corrosion exposure experiments. Results revealed that the presence of DC C-C significantly hastened the corrosion process of copper conductors in the TEL, leading to distinct corrosion patterns at the input and output ends. Furthermore, both the extent of corrosion acceleration and the unevenness of corrosion were positively correlation with the DC C-C level. The above phenomenon was attributed to the special motion of charged particles and paramagnetic substances in TEL under the self-generated magnetic field.

Kilowatt-level supercontinuum generation employing a homemade taper-shaped ytterbium-doped fiber amplifier.

A simple generation method of high-power supercontinuum (SC) based on a homemade long ytterbium-doped taper fiber (T-YDF) amplifier has been demonstrated experimentally and analyzed in this work. The power and spectra of the obtained SC are made adjustable by changing the seed pulse repetition rates. Under a 7.5 MHz seed pulse repetition rate, a SC output is obtained with a spectral range of 1000 nm-1650 nm, maximum output power of 1066 W, and conversion efficiency of 75.7%. The core/clad diameters of the homemade T-YDF are ∼20/400 µm and ∼30/600 µm at the input and output ends, respectively, and the total length is 25 m. Such a long taper fiber can further enhance the properties of the SC while ensuring high power and good beam quality. To the best of the authors' knowledge, this is the first report of directly generating a high average power SC based on the T-YDF amplifier, which provides a proof-of-concept experiment to achieve a high average power SC source and greatly improves the potential application value of the SC source.

Investigation of a cascaded piezoelectric transducer with cone horn for multi-mode power ultrasound application

To meet the ultrasonic application requirement of high power intensity and large mechanical displacement, a new theoretical method is used to study the multi-mode characteristic of the cascaded piezoelectric transducer with cone horn in this paper. Based on equivalent circuit and Kirchhoff’s law to obtain the frequency equation and vibration velocity expression of the transducer, then the resonance frequency and effective electromechanical coupling coefficient can be calculated, the velocity amplification ratio can be obtained in the meantime. This method is distinguish from traditional theoretical analysis, which avoids complex transformation of the multi-excitation sources in cascaded structure, and can calculate more performance parameters. The relationships between these performance parameters and the excitation position of the piezoelectric stack, the length and output end radius of the cone horn are analyzed and compared with the numerical simulation, and the optimized parameters of the transducer size are given. A transducer is manufactured for experimental test, the results show that the experimental value is in good agreement with theoretical calculation and finite element simulation. This work is expected to be used in the optimal analysis of the multi-mode transducer in high power ultrasonic field.

The laser screen imaging measurement system based on arrayed fibers

This paper presents a laser screen imaging measurement system (LSIMS) based on arrayed fibers to measure the velocity and dimension of a flying object. A laser diode is connected to the emission module of the laser screen via a single-mode fiber, then the emitted light beam is collimated into a parallel beam with a lens, this structure is arrayed to form the laser screen. The receiving module of the laser screen employs a cylindrical lens array to converge the collimated beams into a focal line. The input ends of the plastic fibers are arrayed along this focal line, while the output ends are imaged on the sensor of a line scan camera (LSC) through a lens. The LSIMS effectively modulates the process of a flying object passing through the laser screen into the light intensity change in the plastic fibers. The velocity and dimension of the flying object are subsequently measured through the analysis of the image obtained by the LSC. The timing accuracy of the LSIMS is verified through experiments. The velocity and diameter of pellets launched by a slingshot are measured and analyzed for errors.

Recognition of precession angles of non-cooperative targets based on deep learning with privileged information

With an increasing number of countries engaging in space activities worldwide, space non-cooperative target tracking and identification technology has become a prerequisite for safely conducting space operations. In order to the identify distant non-cooperative targets performing complex motions, this paper proposes a method to recognize difficult parameters by using easily available signal labels as privileged information, which is named Pi-FcResNet. The privileged information is connected to the output end of the network through a fully connected network and coupled with the linear layer of the main network. Through testing, our network achieved a recognition accuracy of 94.45 % for precession angles under high signal-to-noise ratio conditions. After incorporating the Convolutional Block Attention Module (CBAM), our method demonstrates fast fitting speed and robust performance. Testing on experimental data shows that, compared to traditional methods, our approach offers better stability and reproducibility in recognizing micro-motion parameters. This approach of using known information as additional information for deep learning networks holds great potential in the field of feature extraction for space non-cooperative targets undergoing complex motions.

Sustainability assessments of commercial urban agriculture – a scoping review

The field of urban agriculture has seen an increase in development and attention in recent years, with a large share of literature addressing whether urban agriculture may pose a solution for food insecurity and combat environmental impacts. However, few studies have examined the many sustainability claims of urban agriculture systems, especially for urban farms intended for larger output and commercial ends. In this study, we analyze sustainability assessments of urban agriculture for commercial implementation. We do this by exploring the methods employed for conducting sustainability analyses, outlining the different urban agriculture cultivation systems, analyzing which sustainability aspects are considered, looking into what the sustainability analyses conclude, and studying how authors anticipate the knowledge gained from their sustainability assessments can be used. Environmental aspects of sustainability were more often assessed than other sustainability aspects, and LCA research practice was used for the majority of environmental assessments. Some studies compared the environmental benefits of different types of urban agriculture systems, but this was not conclusive overall as to what systems would be more environmentally beneficial. This suggests that urban agriculture’s sustainability cannot be universally categorized but should be assessed in relation to specific environmental conditions and urban contexts. Future research should aim to develop more nuanced frameworks for evaluating the environmental, social, economic and governance impacts of urban agriculture.

Polarity-controllable magnetic skyrmion filter

Abstract The skyrmion generator is one of the indispensable components for the future functional skyrmion devices, but the process of generating skyrmion cannot avoid mixing with other magnetic textures, such as skyrmionium and nested skyrmion bags. These mixed magnetic textures will inevitably lead to the blockage of skyrmion transport and even the distortion of data information. Therefore, the design of an efficient skyrmion filter is of great significance for the development of skyrmion-based spintronic devices. In this work, a skyrmion filter scheme is proposed, and the high-efficiency filtering function is demonstrated by micromagnetic simulations. The results show that the filtering effect of the scheme depends on the structure geometry and the spin current density that drives the skyrmion. Based on this scheme, the polarity of the filtered skyrmion can be controlled by switching the magnetization state at the output end, and the “cloning” of the skyrmion can be realized by geometric optimization of the structure. We believe that in the near future, the skyrmion filter will become one of the important components of skyrmion-based spintronic devices in the future.

Study on Gas-Liquid Coaxial Jet Foam Generator and Its Foaming Characteristics.

In order to solve the difficulty of the existing compressed air foam system with low FER and difficult in having both the FER and range. A new type of foam generator for CAFS was designed, an air-liquid coaxial foam generator, which produces foam with high FER (the ratio of the foam volume to the volume of the foam solution) and large output momentum. In this paper, experiments on the foam production performance of a gas-liquid coaxial jet foam generator were carried out with different parameters, such as liquid flow rate, gas flow rate, and foam output end diameter. The variation of FER, foam half-life, range, foam volume, and compressed air utilization rate with the experimental parameters were analyzed. The results show that the foaming performance of the foam generator tends to rise in the range of 8-12.4 m3/h at a fixed gas flow rate, the FER and foam half-life are negatively related to it, and the foaming performance tends to decrease in the range of 12.4-18 m3/h. The best foaming performance was achieved when the liquid volume of the foam generator was 12.4 m3/h. For the liquid volume value in different intervals, the foaming performance varies with the air supply volume. When the liquid volume is higher than 12.4 m3/h, increasing the air supply volume is beneficial to improve the foaming performance, and when the liquid volume is lower than 12.4 m3/h, increasing the air volume does not improve the foaming performance. The effect of the diameter of the foaming chamber on the foaming performance is not monotonic, and an optimum value exists. Compared with similar devices, the gas-liquid coaxial jet foam generator has strong advantages in FER and range and has better application prospects for fire control in restricted spaces.

Design and application of bidirectional soft actuator with multiangle chambers

PurposeThis study aims to introduce a novel bidirectional soft actuator as an enhancement to conventional pneumatic network actuators. This improvement involves integrating air chambers positioned at specific angles to improve stability, adaptability and grasping efficiency in various environments.Design/methodology/approachThe design approach incorporates air chambers positioned at a 45° angle relative to the horizontal direction at the actuator's terminus, along with additional chambers at a 90° angle. Mathematical models are developed for longitudinal and transverse bending, as well as for obliquely connected cavities, based on the assumption of piecewise constant curvature. Analyses are conducted on output forces, bending characteristics and end contact areas for both transverse and longitudinal ends.FindingsThe proposed soft actuator surpasses traditional pneumatic network actuators in gripping area due to the inclusion of a diagonal air cavity and a transverse pneumatic network structure at the terminus. As a result, it provides torsion and gripping force in both directions. Testing on a dedicated platform with two variants of grippers demonstrates superior gripping force capability and performance in complex environments.Practical implicationsThrough the design of multiangle chambers, the soft actuator exhibits diverse driving angles and morphological variations, offering innovative design perspectives for industrial grasping.Social implicationsThe design of multiangle chambers facilitates personalized configurations of soft actuators by researchers, enabling tailored angles for specific interaction environments to achieve desired functionalities. This approach offers novel insights into soft actuator design, addressing more prevalent industrial grasping challenges.Originality/valueThis study introduces a novel soft actuator design that significantly enhances gripping capabilities in comparison to conventional pneumatic network actuators. The incorporation of specific air chamber configurations and mathematical modeling provides valuable insights for the development of adaptable and efficient robotic grippers for industrial and household applications.

Defect recognition of photovoltaic panels based on adaptive dimensional feature aggregation convolutional neural network

Abstract Under the policy framework of achieving carbon neutrality goals and addressing climate change, the importance of photovoltaic power generation will become more prominent, therefore the detection of defects in photovoltaic panels will become increasingly important. In order to accurately detect defects in photovoltaic panels, this paper proposes an adaptive dimensional feature aggregation algorithm that combines Deformable Convolutional (DCN) and C3 convolutional layers to form C3_ DCN module enhances the generalization ability of convolutional kernels; By incorporating the Cross Modal Transformer Attention Mechanism (CoTAttention) and Context Enhancement Module (CAM) at the output end, the model has the ability to adaptively allocate computing resources and enhance the ability to detect small targets; Using Focal EIoU as the loss function reduces the slow convergence speed and inaccurate results of known box regression methods. The experimental results show that for the PVEL-AD industrial detection dataset, the improved model has an average accuracy of 91.8%, which is 1.5% higher than the original model.

Research on Overvoltage at the Wind Turbine Terminal

Abstract This article provides an in-depth analysis of the causes of overvoltage at the generator end and the existing overvoltage protection circuits. Due to the long cable connection between the generator and the converter, voltage reflection occurs during the power transmission process, resulting in overvoltage at the output end of the generator and the input end of the converter. A mathematical model and simulation model have been established to address this issue. Firstly, the transmission line theory is used to analyze the characteristics of PWM pulse transmission in long cables. The reasons for overvoltage at the generator end and the influence of cable distribution parameters on overvoltage are analyzed; Secondly, conduct theoretical calculations; Finally, establish a simulation model using Matlab/Simulink, and analyze the harm of motor terminal overvoltage to the wind power generation system through simulation.

Design and control of variable stiffness joint based on magnetic flux adjustment mechanism

PurposeThis study aims to improve the robot’s performance during interactions with human and uncertain environments.Design/methodology/approachA joint stiffness model was established according to the molecular current method and the virtual displacement method. The position and stiffness coordination controller and fuzzy adaptive controller of variable stiffness joint are designed, and the principle prototype of variable stiffness joint is built. The position step and trajectory tracking performance of the variable stiffness joint are verified through experiments.FindingsExperimental test shows that the joint stiffness can be quickly adjusted. The accuracy of position and trajectory tracking of the joint increases with higher stiffness and decreases with increasing frequency. The fuzzy adaptive controller performed better than the position and stiffness coordination controller in controlling the position step and trajectory tracking of the variable stiffness joint.Originality/valueA hybrid flux adjustment mechanism is proposed for the components of variable stiffness robot joints, which reduces the mass of the output end of variable stiffness joints and the speed of joint stiffness adjustment. Aiming at the change of system controller performance caused by the change of joint stiffness, a fuzzy adaptive controller is proposed to improve the position step and trajectory tracking characteristics of variable stiffness joints.

Noise filtering options for conically scanning Doppler lidar measurements with low pulse accumulation

Abstract. Doppler lidar (DL) applications with a focus on turbulence measurements sometimes require measurement settings with a relatively small number of accumulated pulses per ray in order to achieve high sampling rates. Low pulse accumulation comes at the cost of the quality of DL radial velocity estimates and increases the probability of outliers, also referred to as “bad” estimates or noise. Careful filtering is therefore the first important step in a data processing chain that begins with radial velocity measurements as DL output variables and ends with turbulence variables as the target variable after applying an appropriate retrieval method. It is shown that commonly applied filtering techniques have weaknesses in distinguishing between “good” and “bad” estimates with the sensitivity needed for a turbulence retrieval. For that reason, new ways of noise filtering have been explored, taking into account that the DL background noise can differ from generally assumed white noise. It is shown that the introduction of a new coordinate frame for a graphical representation of DL radial velocities from conical scans offers a different perspective on the data when compared to the well-known velocity–azimuth display (VAD) and thus opens up new possibilities for data analysis and filtering. This new way of displaying DL radial velocities builds on the use of a phase-space perspective. Following the mathematical formalism used to explain a harmonic oscillator, the VAD’s sinusoidal representation of the DL radial velocities is transformed into a circular arrangement. Using this kind of representation of DL measurements, bad estimates can be identified in two different ways: either in a direct way by singular point detection in subsets of radial velocity data grouped in circular rings or indirectly by localizing circular rings with mostly good radial velocity estimates by means of the autocorrelation function. The improved performance of the new filter techniques compared to conventional approaches is demonstrated through both a direct comparison of unfiltered with filtered datasets and a comparison of retrieved turbulence variables with independent measurements.

The study of thermal-structural coupling deformation analysis for flexible space manipulator in orbit

Abstract The space manipulator can assist astronauts to accomplish space activities, including docking, fixing, and grasping. It is subjected to thermal radiation and produces thermal deformation during orbit operation, which makes the operation of the space manipulator deviate from the predetermined trajectory and further affects its positioning accuracy. Therefore, to solve the problem of bidirectional coupling thermal-structure deformation analysis and positioning accuracy for space manipulator, based on the thermal-structural bidirectional coupling deformation analysis, a method of its thermal deformation on the output positioning accuracy of space flexible manipulator is proposed. It analyzes the bidirectional coupling relationship between the temperature and its thermal deformation for the manipulators. Then, the influence of thermal deformation on the output joint error and end positioning accuracy of the space manipulator are analyzed. Finally, the validity of this method is verified by numerical analysis. Compared with the unidirectional coupling model, the bidirectional coupling model comprehensively considers the structure, deformation and temperature of manipulators. It is closer to the real system. Thermal deformation will reduce the reliable runtime of the space manipulator in orbit. The study provides a theoretical basis for its thermal design and control.

Femtosecond-laser-inscribed cladding waveguides in KTiOPO4 crystal for second-harmonic generation and Y-branch splitters

In this study, the fabrication of straight- and Y-branch-cladding waveguides in KTiOPO4 crystals using femtosecond laser-direct writing is described. The second-harmonic generation (SHG) of green light through the cladding waveguides was realized using a pulsed-wave pump at 1,064 nm. The guiding properties of straight-cladding waveguides fabricated by varying the laser-writing conditions were investigated. The minimum insertion loss was approximately 2.0 dB at 1,064 nm. Confocal micro-Raman spectroscopy was used to investigate the lattice micro-modifications. The maximum SHG conversion efficiency of the straight-cladding waveguide reached 31.4% with a maximum output power of 79.29 mW from an input power of 252.6 mW. The performances of the Y-branch splitters with splitting angles ranging from 0.5° to 2.6° were characterized at 1,064 nm, showing excellent properties, including symmetrical output ends and approximately equal splitting ratios. An SHG conversion efficiency of 13.4% and maximum output power of 33.63 mW were achieved in the Y-branch splitter with a splitting angle of 1.0°. These findings support potential applications in constructing compact-frequency converters by using femtosecond laser-written KTiOPO4 depressed-cladding waveguides.

Simultaneous polarization and wavelength merging for efficient fiber coupling system using a designed one-mirror prism

The difference in beam quality between the fast-axis and slow-axis directions of semiconductor lasers limits its wide application. Conventional development methods for solving this problem require a large number of optical components. A one-mirror prism shaping scheme based on wavelength combination and polarization combination techniques is proposed to simultaneously halve the optical width in the slow-axis direction and fill in the dark region in the fast-axis direction to improve and equalize the beam quality. Compared with the traditional beam shaping scheme, the design does not use the cutting-translation-rearrangement of prism technology to avoid uneven spot distribution at the same time, the use of the design of a single prism can achieve several functions to improve the efficiency of prism utilization, to avoid the use of prism stacks, the whole system is simple and compact, easy to implement The design couples two laser stacks, both consisting of 10 cm-bars, into the target fiber with a fiber characteristic of 400 μm, 0.22. An output power of 1415.8 W is obtained from the output end of the fiber, and the coupling efficiency is calculated to be 88.5%.

Development of a recycling machine for constructing synthetic yarn from plastic waste

A major challenge in plastic recycling is to convert plastic waste into a useful product. For this transformation, sustainable technologies such as plastic recycling machines are required. Current technological concepts of plastic recycling are fairly similar. This study aims to develop a small and economical plastic recycling machine to enhance microenterprise by supplying simple equipment for recycling locally processed plastic waste into thread. Starting with a hopper at the input end, the machine incorporates an auger inside a barrel, which is then linked to a metallic perforated mold at the output end. With the help of the system, the plastic flakes melting process is facilitated by maintaining temperatures between 170 °C to 211 °C at equispaced locations of a uniform barrel, while the auger spin enables the flow of molten plastic forward towards the mold.The mold reshapes the liquid plastic into strings of thread. The machine exhibits higher efficiency, reaching approximately 75 % at a decreased screw speed, as low as 28 rpm. It also achieves an average throughput of 156 gm/hour at the lowest specific mechanical energy (SME) consumption. The prototype consumes 1.5 kW for an hour operation. The entire system requires minimal space, making it appealing to individuals with limited financial resources to start a new business venture.•A sustainable technology to recycle plastic waste into plastic thread.•This optimized, portable and robust system ensures safety and lower operating costs.•This system does not require prior knowledge for operation, hence encouraging small entrepreneurs.

Design and characterization of a self-matching photonic lantern for all few-mode fiber laser systems

We model and demonstrate a self-matching photonic lantern (SMPL) device, which is designed to address the constraint of limited transverse modes generated by fiber lasers. The SMPL incorporates a FMF into the array at the input end of a traditional photonic lantern. The few-mode fiber at the output end is specifically configured to align with the few-mode fiber at the input, therefore named as SMPL. This paper details the design and fabrication of the SMPL device, validated by both simulation and experiment. The 980nm fundamental mode, injected via 980nm single-mode fibers, selectively excites corresponding higher-order modes at the few-mode port of the SMPL. Additionally, 1550nm fundamental and higher-order modes injected at the input end into the SMPL device demonstrates mode preservation and low-loss transmission characteristics. The SMPL is well-suited for developing a ring laser system, enabling selective excitation of 980nm pump light modes and facilitating closed-loop oscillation and transmission of 1550nm laser.

Research on Surface Defect Detection of Strip Steel Based on Improved YOLOv7.

Surface defect detection of strip steel is an important guarantee for improving the production quality of strip steel. However, due to the diverse types, scales, and texture structures of surface defects on strip steel, as well as the irregular distribution of defects, it is difficult to achieve rapid and accurate detection of strip steel surface defects with existing methods. This article proposes a real-time and high-precision surface defect detection algorithm for strip steel based on YOLOv7. Firstly, Partial Conv is used to replace the conventional convolution blocks of the backbone network to reduce the size of the network model and improve the speed of detection; Secondly, The CA attention mechanism module is added to the ELAN module to enhance the ability of the network to extract detect features and improve the effectiveness of detect detection in complex environments; Finally, The SPD convolution module is introduced at the output end to improve the detection performance of small targets with surface defects on steel. The experimental results on the NEU-DET dataset indicate that the mean average accuracy (mAP@IoU = 0.5) is 80.4%, which is 4.0% higher than the baseline network. The number of parameters is reduced by 8.9%, and the computational load is reduced by 21.9% (GFLOPs). The detection speed reaches 90.9 FPS, which can well meet the requirements of real-time detection.