Explore the vast range of titles available.

In the present study, we analyzed negative electricity released from insects captured by an electric field (EF)-producing apparatus. Adult houseflies (Musca domestica) were used as the model insect. The EF producer consisted of a negatively charged polyvinyl chloride membrane-insulated iron plate (N-PIP) and a non-insulated grounded iron plate (GIP) paralleled with the N-PIP. An EF was formed in the space between the plates. A housefly placed on the GIP was physically attracted to the N-PIP, and electricity released from the fly was detected as a specific transient electric current at the time of attraction and during subsequent confinement of the fly to the N-PIP. The magnitude of the insect-derived electric current became larger as the voltage applied to the N-PIP increased. We determined the total amount of electric current and confinement time within the apparatus necessary to kill all captured flies. These results demonstrate the insecticidal function and insect-capturing ability of the EF-producing apparatus.

It is well known that path planning has always been an important study area for intelligent ships, especially for unmanned surface vehicles (USVs). Therefore, it is necessary to study the path-planning algorithm for USVs. As one of the basic algorithms for USV path planning, the rapidly-exploring random tree (RRT) is popular due to its simple structure, high speed and ease of modification. However, it also has some obvious drawbacks and problems. Designed to perfect defects of the basic RRT and improve the performance of USVs, an enhanced algorithm of path planning is proposed in this study, called the adaptive hybrid dynamic stepsize and target attractive force-RRT(AHDSTAF-RRT). The ability to pass through a narrow area and the forward speed in open areas of USVs are improved by adopting the AHDSTAF-RRT in comparison to the basic RRT algorithm. The improved algorithm is also applied to an actual gulf map for simulation experiments, and the experimental data is collected and organized. Simulation experiments show that the proposed AHDSTAF-RRT in this paper outperforms several existing RRT algorithms, both in terms of path length and calculating speed.

Electromagnetic attractive forming (EMAF), as an emerging branch of electromagnetic forming (EMF), has attracted increasing attention due to its unique capacity to shape workpieces toward the coil, offering distinct advantages in forming small-diameter tubes, repairing surface dents, and strengthening hole fasteners. This review systematically classifies and elaborates on the two main approaches for generating electromagnetic attractive force: (1) methods based on dual-frequency discharge and (2) methods based on low-frequency discharge. For each category, the working principles, key technological configurations, experimental verifications, and application scenarios are comprehensively discussed. The dual-frequency discharge approach, implemented through sequential dual-capacitor, dual-coil, and novel single-power circuits, enables controllable attractive forces for sheet/tube forming and hole-fastener strengthening. The low-frequency discharge approach, utilizing ferromagnetic effects, attractive screen, or current-phase-difference mechanisms, extends EMAF to ferromagnetic and non-ferromagnetic materials. Finally, the existing challenges and future research directions are outlined, aiming to provide clear research guidance for the in-depth development and practical engineering application of EMAF technology.

Electromagnetic forming (EMF) is a technology that uses Lorentz force to drive the deformation of light alloy. In the processing of small metal pipe fittings, attraction forming is beneficial to reduce the design requirements of forming coils and the application cost of actual tooling. However, the attractive dual-frequency current method requires strict matching between currents. This will lead to difficulty in controlling and changing the attractive force, thus reducing the uniformity of the deformation of the workpiece. To solve this problem, a field shaper is introduced to optimize the distribution of electromagnetic force and improve the uniformity of pipe forming. The finite element model including circuit field, electromagnetic field, and structure field was established, and the bulging of an aluminum alloy pipe fitting with a radius of 10 mm and a length of 40 mm under the action of 9-kV power supply was simulated. The results show that the deformation uniformity is increased by 15% and the degree of shape change is increased by 8.9% with the addition of field shaper. It is proved that field shaper can improve the uniformity of pipe fitting.

The ability to generate an attractive force for electromagnetic forming is an interesting and challenging issue, compared with conventional electromagnetic repulsion processes. This work presents a discharge system with two sets of power supplies and a timing control system for the production of a dual-frequency discharge current in a single coil. The discharge current can be employed to generate an attractive force between the coil and the workpiece in the forming process. The effectiveness of the system was verified both by numerical simulations and by a series of experiments of sheet metal forming. Our results show that an AA 1060 aluminum alloy sheet with a thickness of 1 mm, at a distance of 9 mm from the coil bottom, can be attracted towards the coil with a maximum deformation of about 4.7 mm. We also demonstrate that there is an optimum value for deformation depth, which is related to the initial discharge voltage of the fast discharge system. The presented method and results can be helpful in designing electromagnetic forming systems and widening their applications.

This study proposes an electromagnetic balance-based structural design and shim plate application to improve the response characteristics of an electromagnetic brake. Electromagnetic brakes typically experience response delay due to inductive effects and residual magnetic flux after power-off. To address this issue, the inner and outer thicknesses of the stator were parameterized to achieve balanced magnetic flux distribution, and a non-magnetic shim plate (SUS 304) was applied to reduce residual flux within the electromagnet. Finite element analysis (FEA) was conducted to evaluate the influence of structural parameters on the magnetic flux balance and attractive force. The optimized stator geometry provided a stable electromagnetic balance, and the shim plate effectively reduced the response delay and improved the overall response performance compared with the conventional design. These findings demonstrate that the proposed electromagnetic balance design combined with shim plate application is an effective approach to enhance the reliability and control responsiveness of electromagnetic brakes, with potential applicability to robotic and industrial actuator systems.

As throat radius decrease to micro-nanoscale, seepage in unconventional reservoirs such as ultra-low permeability and tight reservoirs differs from conventional ones. Flow experiment in micropores is a promising approach to study characteristics of microflow. In this paper, a visual experimental device was established. Water flow through micropores with radius of 1.38–10.03  μ m was investigated, under 0.033–16 MPa/m. The results showed that in microscale, water flow did not agree with Poiseuille equation. Flow rate was lower than theoretical value and showed nonlinear characteristics. In the near wall area, due to the attraction of solid wall, a stagnant fluid layer was formed. It occupied flow space and thus lowered flow rate. Its thickness declined with pressure gradient increasing, which led to nonlinear flow characteristics. When the pressure gradient was very high, the thickness stopped declining and kept constant. Afterward, the flow transited to linear. In pores with smaller radius, the steady stagnant layer was thinner, but took a larger proportion of the flow space. For tubes of r = 1.38 , 4.81 , 10.03 μ m , the thickness of steady stagnant layer was 0.11, 0.23, 0.27  μ m , respectively.

Accurate dynamic modeling is the basis for achieving high-precision motion control of a wheeled wall-climbing robot. In a dynamic model, the magnetic attractive force is one of the important influencing forces. In this study, to quickly obtain the attractive force of the magnetic wheel under different wall structure and attitude, the equivalent magnetic circuit method is combined with an analytical approach to construct attractive force models on the flat wall, the 90° concave corner, and the 90° convex corner, respectively. By establishing the geometric relations of the air gap, the reluctance is calculated to analyze the effects of changes in wall structure and relative attitude. The formula for calculating the attractive force is obtained based on this analysis. The proposed model’s accuracy was confirmed by comparing it to finite element analysis (FEA) results. These models enable rapid calculation of the dynamic attractive force, providing a foundation for establishing a high-precision dynamic model for a wheeled wall-climbing robot.

This paper discusses a permanent-magnet electromagnetic brake for the semiconductor process of hollow integrated modules. This permanent-magnet electromagnetic brake is characterized by permanent magnets arranged at the bottom of the stator and coils positioned in the middle portion of the stator. The attractive force is generated by the magnetic energy from the permanent magnet, and to counteract the holding force, a current must be applied to the coils. In the case of a permanent-magnet electromagnetic brake, the maximum holding force that can be generated is fixed by the permanent magnet inserted at the bottom, and even if the load conditions vary, the holding force cannot be altered. This study investigated a method to secure an additional holding force by inducing iron losses at the moment when the holding force is required through improvements in the structure of both the stator and rotor of a permanent-magnet electromagnetic brake. To validate the feasibility of this study, prototypes of permanent-magnet brakes were fabricated, and dynamometer tests were conducted.

General analytical expressions are derived for the light pressure force that acts on a spherical particle of arbitrary size and material composition (dielectric, metal) located in the interference field of two arbitrary monochromatic vector Bessel beams. For identical beams on orders of m = 0 and 1, the light pressure force is examined for the case of two parallel and copropagating beams and the case of intersection of the beam axes near a dielectric particle. It is shown that the presence of interference leads to a complex motion of a particle located in a plane perpendicular to the parallel beams. It is also demonstrated that with a change in the angle formed by the intersection of the axes of Bessel beams in the center of the particle, the light pressure force changes nonmonotonically, passing through maxima and minima, the number of which increases with increasing particle size. When the particle is displaced from the intersection point of the axes along a straight line located symmetrically between the beams, the light pressure force oscillates with a change in sign and with a gradually decreasing amplitude.