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The utilization of 3D cell culture for spheroid formation holds significant implications in cancer research, contributing to a fundamental understanding of the disease and aiding drug development. Conventional methods such as the hanging drop technique and other alternatives encounter limitations due to smaller drop volumes, leading to nutrient starvation and restricted culture duration. In this study, we present a straightforward approach to creating superhydrophobic paper cones capable of accommodating large volumes of culture media drops. These paper cones have sterility, autoclavability, and bacterial repellent properties. Leveraging these attributes, we successfully generate large spheroids of ovarian cancer cells and, as a proof of concept, conduct drug screening to assess the impact of carboplatin. Thus, our method enables the preparation of flexible superhydrophobic surfaces for laboratory applications in an expeditious manner, exemplified here through spheroid formation and drug screening demonstrations. [ABSTRACT FROM AUTHOR]

Partial Discharges (PDs) are a significant factor in reducing the insulation life of traction transformers. In recent years, the Acoustic Emission (AE) method has become the most advanced method for detecting PD signals in transformers. The AE method utilizes AE sensors placed on the transformer tank to detect ultrasonic signals emitted by PD and determine the Time Of Arrival (TOA) of the head wave. The windings and cores of a traction transformer consist mainly of metal, which greatly affects the propagation of PD ultrasonic waves. This paper establishes a 110 kV "pressure acoustic, transient" physical field model of the traction transformer with dimensions of 4.63 × 1.48 × 2.84 m3. The model is used to carry out the PD pressure acoustic physical field simulation study of the traction transformer, to clarify the physical characteristics of the ultrasound of the PD defects, and to establish observation points on the transformer tanks to receive ultrasonic time-domain waveforms for PD detection. The simulation results indicate that PD ultrasonic waves exhibit complex propagation characteristics, including reflection, refraction, and reverberation, as they pass through the windings and cores to the observation points. The TOA of the head wave in the ultrasound time-domain waveform is indicated by the first maximum value of the wave crest line. Finally, this paper proposes a multi-level localization method based on the AE method to determine which winding generates the PD in the large-scale traction transformer using only four dynamically moving observation points. [ABSTRACT FROM AUTHOR]

Solvent-pumped evaporation-driven concentration of an initial distribution of solutes on a porous substrate is considered in one and two dimensions. Approximate analytic solutions to the isotropic advection–dispersion equations are first found for a Gaussian kernel and an infinite domain, following the smoothed particle approximation. Analytic solutions for more general initial distributions are then found as sums of Gaussians, and comparison is made with numerical solutions. In each case, initial distributions are advected toward the stagnation point and concentrated. Two-dimensional analysis is then extended to describe anisotropy in permeability and diffusion, and hydrodynamic dispersion. Radial-flow experiments are performed using filter papers and water-soluble dyes. Diffusion coefficients, temperature and humidity profiles, and the evolution of spot distributions are measured. The results confirm minor anisotropy in permeability and diffusion, limited hydrodynamic dispersion, and largely uniform evaporation. Péclet numbers over 2500 are demonstrated. Evaporation-driven concentration provides a mechanism for solute transport over long timescales. Potential applications lie in the design of paper spray microanalytical devices operating by solvent pumping rather than capillary flow. [ABSTRACT FROM AUTHOR]

The regular operation of transformers is significantly impacted by the insulation effectiveness of the transformer insulation oil–paper. In order to explore the mechanism of the influence of an electric field on the thermal decomposition performance of insulating oil–paper, this paper simulated the process of electrothermal coupling decomposition of insulating oil–paper from the micro-level based on molecular dynamics. It was determined that the insulating oil is made up of three 16-carbon hydrocarbon molecules, while the insulating paper is made up of 30 fibrous disaccharide molecules. Using the molecular dynamics simulation approach, the pyrolysis of the insulating oil and insulating paper under various electric field strengths was simulated, and the lysis of reactants and the distribution of products were statistically examined. This paper also studied how the electric field affected the microscopic process of the insulating oil–paper pyrolysis. The findings demonstrate that under the influence of electrothermal coupling, the big molecules of the insulating oil and insulating paper are pyrolyzed to produce a variety of tiny molecules. For the insulating oil, it is easily subject to electron displacement polarization under the influence of an external electric field since it contains non-polar molecules, especially impacted by an electric field of 100 V/m. For the insulating paper, its polar nature, on the other hand, makes itself a good candidate for guiding polarization when exposed to an external electric field. So, the greater the electric field strength is, the greater the impact on the thermal decomposition of the insulating paper is. [ABSTRACT FROM AUTHOR]

As an important high-voltage electrical equipment in the substation, the performance stability of high-voltage current transformers is directly related to the safe operation of the power grid. The insulating medium of the traditional oil-immersed current transformer is an oil-immersed paper structure. When the oil-immersed current transformer malfunctions, it is easy to cause fire and explosion, resulting in very serious consequences. If the transformer with the epoxy resin impregnated paper insulation medium is used, there is no oil and gas inside; thus, it has high reliability, which greatly reduces the risk of fire and explosion. Based on this, considering the application research on the high-voltage current transformers epoxy resin impregnated paper technology, this paper mainly analyzes some precautions for the application of epoxy resin impregnated paper technology to the high-voltage current transformers from three aspects: the research on the insulation performance of the epoxy resin impregnated paper transformers, the research on the mechanical properties, and the research on the relevant experimental methods of the epoxy resin impregnated paper technology application to the high-voltage current transformers. [ABSTRACT FROM AUTHOR]

Paper-based evaporation concentrators with linear and radial geometries are compared. A new method of finding approximate analytic solutions of the advection–dispersion equation is proposed, based on the behavior of concentrators with infinite sources. Analytic approximations are compared with numerical solutions, and the advantage of radial concentration is highlighted: linear concentration rates scale with the square root of the Péclet number Pe while radial rates scale with Pe itself, leading to faster radial concentration beyond a critical value. Experiments are performed with Brilliant Blue FCF dye, using optical transmission and the Beer–Lambert law for quantitation. Dye concentrations are chosen for operation in the linear absorbance regime. Radial concentration is demonstrated under ambient conditions on filter paper disks with 60 mm diameter evaporation areas fed from a perimeter source, in a reverse of the well-known "coffee stain" experiment. Airflow enhanced concentration in strips and wedges is compared directly, using laser-patterned chromatography paper. The advantage of radial concentration is confirmed (and enhanced by diversion of concentrate to the corners of strips) and concentration factors greater than ∼ 500 (the dynamic range of measurement) are obtained in ∼2 h using 30 mm long columns. [ABSTRACT FROM AUTHOR]

We report a liquid metal microstrip antenna on a printing paper whose resonant frequency was tunable by folding the paper. The gallium-based alloy was used as liquid metal, which is instantly oxidized in ambient air. The oxidized liquid metal is easily wettable on printing paper surfaces, while it is non-wettable on laser-printed toner surfaces. An antenna with a 3 mm wide and 39 mm long copper-liquid metal overlapped-feedline linked to the liquid metal microstrip rectangle-shaped patch (40 × 31 mm2) was designed. The antenna pattern was printed on a printing paper using a laser printer. A liquid metal soaked roller was rolled on the antenna pattern printed paper, resulting in a liquid metal pattern where there was no toner. The resonant frequency of the liquid metal on the paper microstrip patch antenna was 2.88 GHz with −18.5 dB S11. The measured characteristics of the antenna were in good agreement with the simulation results. When the antenna was folded, the resonant frequency was changed to 2.68 GHz (x-axis folding) or 2.72 GHz (y-axis folding). Liquid metal on paper fabrication is simple but effective for creating custom-designed antennas that are easily re-designed and fabricated in the field. [ABSTRACT FROM AUTHOR]

Frequency Domain Spectroscopy (FDS) is widely used to estimate oil–paper insulation. The high moisture and long aging change the FDS characteristics of the insulating oil–paper, so normalization processing is required. Still, the choice of single activation energy needs further research. This paper studies the FDS characteristic of oil–paper insulation samples with different moisture and aging degrees and improves the traditional temperature correction method. The enhanced Arrhenius model uses the segmented activation energy to make the normalized FDS curve coincide better with the target curve, and the error is reduced. In addition, to verify the method's effectiveness, this paper proposes an iterative correction process. It corrects the tan δ-f curve of the bushing with an aging time of 800 h based on segmented activation energy, and the overall normalization effect is improved. [ABSTRACT FROM AUTHOR]

Paper has attracted significant attention recently as a microfluidic component and platform, especially in passive pumping devices due to its porous and uniform absorbing nature. Many investigations on 1D and 2D fluid flows were carried out. However, no experimental work has been reported on the three-dimensional effect in porous geometry to improve pumping characteristics in microchannels. Therefore, in this study, the fluid flow in 3D paper-based passive pumps was investigated in microchannels using cylindrical pumps. The effect of pump diameter, porosity, and programmability was investigated to achieve desired flow variations. The results indicated that the flow rate of water increased with an increase in the diameter and porosity of paper pumps. Maximum flow rates achieved for 14 mm diameter pumps of 0.5 and 0.7 porosities were 5.29 mm3/s (317.4 μl/min) and 6.97 mm3/s (418.2 μl/min), respectively. The total volume of fluid imbibition ranged between 266 and 567 μl for 8 and 14 mm diameter pumps, respectively. Moreover, 3D passive pumps can transport larger volumes of liquid with an improved flow rate, programmability, and control, in addition to being inexpensive and simple to design and fabricate. Most importantly, a single 3D paper pump showed an increasing, decreasing, and constant flow rate all in a single microchannel. With these benefits, the passive pumps can further improve the pumping characteristics of microfluidic platforms enabling a cost effective and programmable point-of-care diagnostic device. [ABSTRACT FROM AUTHOR]

The parameter of tensile strength for transformer bushing insulating paper occupies an important position in the structural design and life evaluation of transformer bushing. In order to precisely achieve the effect of aging time and moisture content on the tensile strength of transformer bushing paper, transformer insulating paper samples with a thickness of 0.13 mm were prepared for tensile strength and dielectric strength testing under different moisture contents and aging states. The results show that the tensile strength (MPa) of insulating paper decreases linearly in the range of 0–648 h under accelerated thermal aging at 130 °C. However, there is a more serious exponential decline in the tensile strength (MPa) of insulation paper with its moisture content is boosted. The moisture content in insulation paper is the most important factor for insulation paper deterioration in oil-impregnated paper insulation equipment, which could accelerate the end of insulation service life. The value of capacitance increment ΔC of the insulation paper samples displayed closely linear growth with a moisture content from 0.5% to 5.9%. Strictly controlling the moisture content by monitoring the ΔC value of transformer insulation paper is of significance for prolonging its service life. [ABSTRACT FROM AUTHOR]

Microfluidics approaches have gained popularity in the field of directed cell migration, enabling control of the extracellular environment and integration with live-cell microscopy; however, technical hurdles remain. Among the challenges are the stability and predictability of the environment, which are especially critical for the observation of fibroblasts and other slow-moving cells. Such experiments require several hours and are typically plagued by the introduction of bubbles and other disturbances that naturally arise in standard microfluidics protocols. Here, we report on the development of a passive pumping strategy, driven by the high capillary pressure and evaporative capacity of paper, and its application to study fibroblast chemotaxis. The paper pumps—flowvers (flow + clover)—are inexpensive, compact, and scalable, and they allow nearly bubble-free operation, with a predictable volumetric flow rate on the order of μl/min, for several hours. To demonstrate the utility of this approach, we combined the flowver pumping strategy with a Y-junction microfluidic device to generate a chemoattractant gradient landscape that is both stable (6+ h) and predictable (by finite-element modeling calculations). Integrated with fluorescence microscopy, we were able to recapitulate previous, live-cell imaging studies of fibroblast chemotaxis to platelet derived growth factor (PDGF), with an order-of-magnitude gain in throughput. The increased throughput of single-cell analysis allowed us to more precisely define PDGF gradient conditions conducive for chemotaxis; we were also able to interpret how the orientation of signaling through the phosphoinositide 3-kinase pathway affects the cells' sensing of and response to conducive gradients. [ABSTRACT FROM AUTHOR]

Blood can be a window to health, and as a result, is the most intensively studied human biofluid. Blood tests can diagnose diseases, monitor therapeutic drugs, and provide information about the health of an individual. Rapid response blood tests are becoming increasingly essential, especially when subsequent treatment is required. Toward this need, paper-based devices have been excellent tools for performing blood tests due to their ability to conduct rapid and low-cost diagnostics and analyses in a non-laboratory environment. In this Perspective, we review recent advances in paper-based blood tests, particularly focusing on the specific techniques and assays applied. Additionally, we discuss the future of these paper-based devices, such as how the signal intensity can be enhanced and how the in situ synthesis of nanomaterials can be used to improve the sensitivity, functionality, and operational simplicity. With these advances, paper-based devices are becoming increasingly valuable tools for point-of-care blood tests in various practical scenarios. [ABSTRACT FROM AUTHOR]

Because of the overly averaged element sensitivity in the topological optimization of an irregular structure with a grid independent filter, a topological optimization model was built for the structural domain. The maximization of stiffness was first taken as the goal for the topological optimization of irregular structure stiffness. Subsequently, an element size filter was proposed to address the overly averaged local element sensitivity with the grid independent filter when the designed domain element size varied dramatically. Finally, the element sensitivity of the objective function was derived under the given constraints. A case study was then conducted on a naval gun mount with the maximization of structural flexibility as the objective function and the volume of structural material as a constraint. A stiffness optimization model based on the bi-directional evolutionary structural optimization algorithm was adopted for the topological optimization of the gun mount. Structural optimization was conducted for the gun mount with different shooting angles to realize its optimal stiffness and strength under the constraint of consistent material volume. The optimization results proved that the element independent filter proposed in this paper could be effectively applied in the topological optimization of an irregular structure and used to explore the topological optimization of the supporting structure under impact. [ABSTRACT FROM AUTHOR]

We extend the parametric method developed for the van der Waals model by Lekner [Am. J. Phys. 50(2), 161–163 (1982)] to other equations of state, particularly the Berthelot model, thereby making the testing of these equations of state much faster and simpler. We systematically investigate important properties of first-order phase transitions in the Berthelot model. Thermodynamic properties near the critical point are discussed and the predictions of the Berthelot and van der Waals models are compared with experimental data. The Berthelot equation affords an improved fit to the density–temperature coexistence curve for many substances when compared to the van der Waals equation. A failure of the Berthelot model is its prediction of latent heat and heat capacities that are convex functions at lower temperatures. We also examine two modifications of the Berthelot equation of state that, like the van der Waals model, are also solvable by the parameter method. These, which we call the cPF and dPF models, reduce to the van der Waals and Berthelot models in different limits of their parameters. They give improved fits to the experimental data away from the critical point but involve an additional fitting parameter. Editor's note: While the van der Waals equation of state provides a simple model for phase transitions, it fails to achieve a good quantitative fit for properties near phase transitions in most substances. A closely related model, the Berthelot model, still has only two free parameters, but it allows the attraction between molecules to depend not only on volume but also on temperature. This paper builds on the parametric expressions for the van der Waals gas derived in a 1982 paper in this journal by John Lekner. It shows that similar expressions derived from the Berthelot model provide a much better fit to the data. This derivation could be shared with students in intermediate or advanced thermodynamics courses. [ABSTRACT FROM AUTHOR]

In this work, we convert a common verification lab in the physics curriculum, measuring the charge-to-mass ratio of the electron (e/m), into an investigative lab on systematic uncertainty. The Bainbridge apparatus, commonly used to measure e/m, can have significant systematic uncertainties, leading to large discrepancies with the accepted value. Students were asked to quantify possible systematic uncertainties in the apparatus and correct them. Building upon each other's work from semester to semester, students characterized multiple sources of systematic uncertainty. Not only did the students learn about uncertainty analysis techniques that reveal systematic uncertainties, but they also dramatically improved the accuracy of the apparatus, reducing the discrepancy from 15% to 0.5%. This paper describes a pedagogical approach to exploring unknown systematic uncertainties in an intermediate laboratory setting and the student-learning benefits of such an approach. In addition, it provides detailed information about untangling and correcting the sources of systematic uncertainty in the Bainbridge apparatus. Editor's Note: This work will be very interesting to two audiences. Its most obvious audience is those who teach the e/m experiment. These readers may have observed that the statistical measurement uncertainties are seldom large enough to make the result consistent with the accepted value. This paper explains these deviations. The paper may be even more useful to the less obvious audience: those who teach upper-level laboratories or projects. This paper may inspire these instructors to involve their students in extended investigations into this and other classic experiments. [ABSTRACT FROM AUTHOR]

The Bloch Sphere visualization of the possible states of a single qubit serves as a useful pedagogical and conceptual tool, offering a one-to-one map between qubit states and points in a 3D space. However, understanding many important concepts of quantum mechanics, such as entanglement, requires developing intuitions about states with a minimum of two qubits, which map one-to-one to unvisualizable spaces of six dimensions and higher. In this paper, we circumvent this visualization issue by creating maps of subspaces of 1- and 2-qubit systems that quantitatively and qualitatively encode properties of these states in their geometries. For the 1-qubit case, the subspace approach allows one to visualize how mixed states relate to different choices of measurement in a basis-independent way and how to read off the entries in a density matrix representation of these states from lengths in a simple diagram. For the 2-qubit case, a toroidal map of 2-qubit states illuminates the non-trivial topology of the state space while allowing one to simultaneously read off, in distances and angles, the level of entanglement in the 2-qubit state and the mixed-state properties of its constituent qubits. By encoding states and their evolutions through quantum logic gates with little to no need of mathematical formalism, these maps may prove particularly useful for understanding fundamental concepts of quantum mechanics and quantum information at the introductory level. Editor's Note: While single qubit states can be visualized with a Block Sphere, 2-qubit states are much more challenging to visualize. This paper presents a new way to visualize these states using toroids. While the representation is limited to states with real coefficients, it can illustrate both separable and entangled states, allowing students to develop intuition for their use in quantum information. This representation can be used in introductory classes in a quantum information curriculum but will also be valuable in more standard quantum mechanics courses at a variety of levels. [ABSTRACT FROM AUTHOR]

A common belief is that any closed, counterclockwise cycle on a pV diagram represents a refrigerator or heat pump. It has been established that this is not the case, but previous papers on this topic have made unnecessary assumptions about the temperatures of the energy reservoirs and about how the system exchanges energy with the reservoirs. Relaxing these assumptions leads to a wide array of unexpected behaviors. In some cases, the same pV cycle can be a heat pump, a cold pump, or a Joule pump simply by changing how the system is connected to the reservoirs. This paper explores the strange world of counterclockwise cycles. Editor's note: In this paper, author Randall Knight explores the rich behavior of counterclockwise thermodynamic cycles. A counterclockwise cycle can function as a heat pump or refrigerator, but this is not the only possibility. The choice of thermal reservoirs and the choice of which reservoir heat is absorbed from and exhausted to during the cycle affect the coefficient of performance and even the basic function of the device. The author illustrates these possibilities through an analysis of counterclockwise Carnot, Kelvin, Brayton, and Stirling cycles. The analysis includes interesting possibilities, such as a cycle that operates with a single reservoir, as well as practical applications like the role of heat exchangers. The surprising results of this analysis will likely be of interest to anyone who has studied thermodynamics, and the material can easily be incorporated into any course that includes thermodynamics, from introductory physics to graduate study. [ABSTRACT FROM AUTHOR]

This article presents an unpublished manuscript by Alfred M. Bork that was written in 1976 as an introduction to a collection of Maxwell's papers on electromagnetism which was never published. It provides encouragement to the reader to study the original works of Maxwell on electromagnetism, and this encouragement is as timely today as in 1976. Editor's note: Maxwell's papers on electromagnetism are foundational to physics, and modern physicists have much to learn from reading them. This paper shares a nearly 50-year-old introduction to the papers written by Alfred Bork but never published. The manuscript was transcribed and edited by Kirk McDonald, who also added extensive footnotes and citations. The paper will help both students and faculty who wish to read and learn from Maxwell's original papers. [ABSTRACT FROM AUTHOR]

Narrowband laser sources are used in applications that require high-precision or stable optical frequency. Such applications include high-resolution spectroscopy, long-distance measurement, and coherent optical communication. The linewidth of a laser is a direct measure of the laser's stability; therefore, characterization of laser linewidth is essential. In practice, however, determining a laser's linewidth is not a trivial task and typically requires expensive equipment or a complex experimental arrangement. This paper presents a straightforward, low-cost method based on unbalanced interferometry, which allows us to determine the visibility of fringe patterns as a function of the optical path difference and, consequently, the linewidth of the laser. As a test laser, we use a tunable external cavity laser source at around 780 nm, where an interference filter is employed for wavelength selection. Data obtained by applying the interferometric technique to this laser and the analysis of these data, along with the resulting linewidth value, are presented. Given that the described measurement setup is inexpensive, straightforward, and pedagogically accessible, it is well-suited for an instructional physics laboratory experiment and will also be of interest to laboratory researchers. Editor's Note: This paper presents a low-cost interferometric technique for measuring the linewidth of a laser. The author first provides context for the interferometric technique by giving a comprehensive, clear, and detailed description of other techniques that can be used to measure a laser's linewidth, including the benefits and drawbacks of each. The principle behind the interferometric method is then presented, and the required experimental setup is explained. Data obtained by applying the interferometric technique to an external cavity laser are presented, and the analysis of these data, along with the resulting linewidth value, are given. This work provides a well-suited experiment for an advanced instructional physics laboratory or optics/laser course. It will also hold appeal as a cost-effective tool for laser linewidth measurement in laboratory research. [ABSTRACT FROM AUTHOR]

This paper develops the approach to special relativity put forward by John S. Bell. The classical dynamics of an electron orbiting a nucleus in uniform motion is solved analytically and compared to numerical simulations for an accelerated nucleus. The relativistic phenomena of length contraction and time dilation are shown to result from the electric and magnetic forces on the electron when its motion is analyzed in a single frame of reference. The relevance of these results for understanding the theory of special relativity is discussed. In this paper, the author explores a suggestion by John Bell for teaching special relativity: to introduce length contraction and time dilation as dynamical phenomena arising from the laws of motion, without reference to the Lorentz transformations. The paper provides historical and philosophical insight into the development of special relativity alongside an analysis of electron orbits in a classical model of an atom. Using only the Lorentz force law, the author illustrates the deformation of orbits of moving and accelerating atoms with approximate, exact, and numerical calculations that reveal time dilation and length contraction. Instructors may find these derivations useful in teaching courses on modern physics, relativity, classical mechanics, electrodynamics, or numerical methods. [ABSTRACT FROM AUTHOR]

Designing advanced combustors that operate at high temperatures and produce little pollution, especially in the absence of primary and dilution holes, is a difficult task that may bring significant challenges. In this regard, this paper introduces a Kriging surrogate model approach to optimize the outlet temperature distribution of the combustor to achieve such advanced low-pollution combustors. Building upon previous research, this study explores the effects of the swirler blade installation angle on the outlet temperature distribution of the combustor without primary or dilution holes. Traditional methods, such as the control variable method using computational fluid dynamics (CFD) for numerical simulation, are limited in application due to the complex coupling of flow, heat transfer, mass transfer, and combustion processes. In contrast, surrogate models, especially the Kriging model, offer a rapid and efficient alternative to extensive CFD simulations that provide accurate predictions and error estimates for the solution of the problem. In summary, this paper details the process of generating sample points through three-dimensional numerical simulations, develops a Kriging surrogate model through Latin hypercube sampling, and optimizes the model to identify the most uniform outlet temperature distribution achievable by adjusting the installation angle of the swirl blade. The optimal design parameters, which are quickly obtained through the Kriging model, showed a significant reduction in the overall temperature distribution function and the radial temperature distribution function by 21% and 27.14%, respectively. [ABSTRACT FROM AUTHOR]

Potential transfer is an essential link in equipotential live-line work (EPLW), which has a potential safety hazard. To ensure the safety of the linemen, this paper conducted experimental research on this process. First, to investigate the discharge characteristics of the potential transfer gap in EPLW, this paper developed a simplified experimental platform to examine the relationship between the transfer voltage and gap distance, as well as the electrode structure, during the potential transfer process. Second, to explore the discharge development process of potential transfer, this paper built a discharge observation experimental platform to observe the discharge process and explore the effects of gap distance and type of the floating electrode on the discharge development process and potential transfer current. The research results are valuable for practical projects and linemen safety. [ABSTRACT FROM AUTHOR]

Friction plays a key role in the assessment of the safety and stability of mechanical systems (such as superconducting magnet quench explosion, aerospace vehicle bearing wear, etc.). Due to the closeness of the interfaces in engineering structures and the randomness of the contact surfaces, existing methods for measuring static friction force are unable to measure it at the contact interfaces of engineering structures under service conditions. In this paper, a new method for measuring the static friction force at the interface based on electrical signals is proposed. This method enables the measurement of the static friction force at interfaces of complex engineering structures under service conditions solely through electrical signals. The results indicate that the contact resistance gradually decreases with the increase in tangential load during the static friction stage until a monotonic behavior of macroscopic sliding occurs. The evolution of contact resistance is linked to the evolution of the real contact area, and this monotonic behavior can be explained as the deformation form of contact points. The accuracy of the proposed electrical measurement method is verified by comparison with experimental results (with an error of less than 9%). The indirect measurement method of friction force proposed in this paper can effectively measure the static friction force at the interfaces of engineering structures under service conditions, and it is expected to be applied to the detection of friction performance at engineering structure interfaces in extreme service environments. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to study the adaptability and enhancement methods of ignition chips in complex electromagnetic environments. In this paper, combined with simulation and calculation technology, we first establish the electromagnetic–electrical–thermal coupling simulation model of ignition chips and analyze the influence of two electromagnetic environments, continuous electromagnetic wave and nuclear electromagnetic pulse, on the electrical–thermal coupling in the bridge area of the ignition chip. The results show that a continuous electromagnetic wave field strength of 1200 V/m, irradiated for 5 s, a nuclear electromagnetic pulse with a rise time of 5 ns, a half-height width of 24 ns, and a leg wire length of 350 mm will cause the ignition chip to fire accidently. In order to suppress its accidental firing, the electromagnetic protection is enhanced by using parallel Transient Voltage Suppressor (TVS) diodes. It has been shown that parallel TVS diodes provide good protection against both continuous electromagnetic waves and nuclear electromagnetic pulses. In particular, the peak induced current decreases by more than 64.7% during the action of continuous electromagnetic waves, and the maximum temperature in the bridge area decreases by 54.34% during the action of nuclear electromagnetic pulses. [ABSTRACT FROM AUTHOR]

The high temperature superconductors enhanced magnetoplasmadynamic thruster is a promising device for various space mission scenarios. However, a critical issue hindering the enhancement of the thruster's performance is the problem of anode power deposition. Previous studies have identified the anode fall voltage as a major contributor to this power deposition. This paper introduces an approximate analytical formula for calculating anode power deposition resulting from anode fall voltage. The paper further analyzes and calculates the variation of anode fall voltage with an applied magnetic field and discharge current. The findings reveal a direct correlation between applied magnetic field and both anode fall voltage and power, indicating an increase with higher magnetic field values. In contrast, while the anode fall voltage experiences a slight decline with increased discharge current, the anode power deposition remains elevated due to the transition from field ionization to thermal ionization. To gain a comprehensive understanding of anode power deposition, an experiment was conducted to obtain measurements under different operating conditions, involving varying levels of applied magnetic field and discharge current. The experimental results align with the theoretical predictions. These insights have the potential to serve as a valuable reference for enhancing the efficiency of magnetoplasmadynamic thrusters, bringing us closer to unlocking the full potential of these remarkable propulsion systems in the realm of space exploration. [ABSTRACT FROM AUTHOR]

A rod fastened rotor (RFR), which contains serial disks, rods (or a rod), and a torque tube, is the main form of heavy duty gas turbines and light duty aero engines. The roughness of the interface is the main parameter affecting the bending stiffness of RFR, and the jumpiness of the disks is the intuitive representation of the unbalance of the rotor. In this paper, a multi-optimization algorithm, NSGA-Ⅱ, was used to improve the vibration behavior of the RFR-bearing system. First, the quantitative relation between the bending stiffness of the rotor and the roughness of the interface was set up by combining the Persson contact theory and the Greenwood–Williamson model, and the nondimensional bending stiffness (NS) was proposed as the optimization objective of roughness. Then, the optimization objective of the jumpiness of the disk, (A + B), was rendered based on the minimum unbalance force. Finally, the multi-optimization on the roughness and jumpiness of the RFR was carried out, and the vibration behavior was improved greatly. In addition, this multi-optimization method was applied to a practical RFR, and the experimental results showed that the vibration amplitude was reduced by about 82%. The work in this paper can provide the guidance for vibration reduction of the rotor system. [ABSTRACT FROM AUTHOR]

Magnesium alloy shows promise of becoming a new generation of degradable biomaterials because of its good biocompatibility and mechanical properties. This paper details the preparation of magnesium alloy by adding calcium and zinc elements to pure magnesium at a specific ratio and strengthened by solid solution treatment and extrusion. The magnesium alloy is subjected to micro-motion wear testing, in vitro degradation product analysis, and in vitro biocompatibility testing and demonstrates excellent performance. The study demonstrates that the prepared Mg-2.0Zn-1.6Ca alloy friction ring has an elliptical shape with a low friction coefficient, which notably enhances the wear resistance of the material. Furthermore, the corrosion of magnesium alloy products in simulated body fluids does not adversely affect the human body. This is because the surface of the magnesium alloy favors cell growth and has excellent antimicrobial properties. The purpose of this paper is to enhance the preparation, surface friction properties, and biocompatibility of magnesium alloys and to provide theoretical and practical guidance for the preparation, processing, and application of high-performance medical magnesium alloys. [ABSTRACT FROM AUTHOR]

In order to obtain a flexible strain sensor with higher sensitivity, a resistive flexible strain sensor based on the AgNWs-graphene-PDMS sensitive layer is prepared in this paper. This paper presents the preparation of a flexible sensitive layer, the preparation and encapsulation of the flexible strain sensor, and the performance tests of the sensor prepared with AgNWs-graphene (AgNWs-Gr) mixtures at different concentrations. The test results indicate that the prepared sensor has a wide detection range with a maximum stretchable length of 118%. The flexible strain sensor prepared with the AgNWs-Gr mixture at a concentration of 5% has the highest sensitivity and the maximum strain sensitivity of up to 236. It also has good repeatability, stability, and rapid response, and it has been tested for practical applications. The results show that the flexible strain sensor has a broad application prospect in fields such as wearable devices and intelligent robots. [ABSTRACT FROM AUTHOR]

To enhance the utilization of clean energy sources, such as wind power and photovoltaic within virtual power plants, and mitigate carbon emissions, this paper proposes a virtual power plant participation in the electricity carbon joint market optimization operation model based on ensemble empirical mode decomposition–improved bat algorithm (IBA)–Markov chain new energy output prediction. First, complementary set empirical mode decomposition is performed on historical data to construct a Markov chain based wind power and photovoltaic prediction model optimized by IBA. Second, this prediction model is used to predict the daily generation power of wind power and photovoltaic power. Finally, with the optimization goals of maximizing the benefits and minimizing the carbon costs of virtual power plants, a virtual power plant system participating in the electricity carbon joint market model based on wind power and photovoltaic output prediction results is constructed. At the same time, demand response factors are introduced and solved using the NSGA-II algorithm. Taking a certain park as an example for simulation analysis, the research results show that the combined effect of carbon market and demand response can achieve 99.82% of new energy consumption in virtual power plants without significantly reducing profits, basically achieving complete new energy consumption, demonstrating the effectiveness of the proposed model in this paper. [ABSTRACT FROM AUTHOR]

The lack of representational diversity and role models in physics, including in our textbooks and curricular materials, is an oft-cited contributing factor to the continuing dramatic under-representation of women and people of color in physics. In this work, we develop an automated, Python-based tool for identifying the names and demographics of scientists who are mentioned in indices and chapters of physics textbooks, enabling authors, publishers, and users of physics textbooks to rapidly analyze the demographics of these texts. We quantitatively validate the automated tool using standard machine learning metrics, attaining high accuracy, precision, recall, and F1 scores. The tool is then used to demonstrate two of the many potential applications: examining whose work is mentioned in the entire collection of textbooks used in a representative four-year undergraduate physics major curriculum as well as an analysis of the demographics of scientists mentioned in a selection of ten introductory physics textbooks. Both of the sample analyses result in a similar portrait, showing that the undergraduate physics textbooks examined in this work focus overwhelmingly on work attributed to White men of European, British, and North American descent. This work points to an urgent need for the physics education community, including textbook publishers, authors, and adopters, to work together to broaden our portrayals of physics to reflect the vast diversity of scientists, both historically and contemporaneously, who are working in this field. Motivated by a desire for textbooks to describe the work of scientists from more diverse backgrounds, the authors of this paper developed a simple tool to characterize the backgrounds of scientists whose work appears in textbooks. The paper describes the methodology and algorithm, as well as the results from testing a range of textbooks. The tool is freely available, with the goal of helping authors develop more representative textbooks as well as helping students and instructors analyze existing textbooks. [ABSTRACT FROM AUTHOR]

The channel vocoder has become a useful tool to understand the impact of specific forms of auditory degradation—particularly the spectral and temporal degradation that reflect cochlear-implant processing. Vocoders have many parameters that allow researchers to answer questions about cochlear-implant processing in ways that overcome some logistical complications of controlling for factors in individual cochlear implant users. However, there is such a large variety in the implementation of vocoders that the term "vocoder" is not specific enough to describe the signal processing used in these experiments. Misunderstanding vocoder parameters can result in experimental confounds or unexpected stimulus distortions. This paper highlights the signal processing parameters that should be specified when describing vocoder construction. The paper also provides guidance on how to determine vocoder parameters within perception experiments, given the experimenter's goals and research questions, to avoid common signal processing mistakes. Throughout, we will assume that experimenters are interested in vocoders with the specific goal of better understanding cochlear implants. [ABSTRACT FROM AUTHOR]

A method of delaying the aging of natural ester oil-paper insulation systems by adding glyceryl triacetate is proposed in this work. A study was conducted on the thermal aging performance of soybean insulating oil mixed with glyceryl triacetate at a volume fraction of 7.5%. Through a 42-day accelerated thermal aging experiment, it was found that the addition of glyceryl triacetate effectively delayed the increase in kinematic viscosity of the insulating oil and reduced the generation of aging products such as moisture and acid. However, the polar compounds in glyceryl triacetate reduced the breakdown voltage of the mixed oil and made the dielectric loss factor higher than that of pure oil. In addition, tests were conducted on the insulating paper immersed in two types of oil, and it was found that the addition of glyceryl triacetate helps to distribute mixed oil molecules on the surface of insulating paper, which effectively helped absorb moisture from the paper, weakening the hydrolysis reaction of cellulose and delaying the aging of insulating paper. In addition, the insulating paper immersed in the mixed oil maintains good power frequency breakdown voltage and dielectric properties throughout the thermal aging experiment. [ABSTRACT FROM AUTHOR]

The "Klemens channel" formalism is commonly used in interpretations of experimental results on the lifetime of longitudinal optic (LO) phonons and Fröhlich polarons (FPs) in polar bulk, polycrystalline, and nanostructured solids. Here, in Paper I of this bipartite article, the two-particle vibrational DOS function(s) for spatially confined longitudinal acoustic and LO phonons is implemented at evaluation on FP decay probability via the "Klemens channel" and its lifetime for the case of FPs confined within InAs quantum dots. This approach yields a convincing elucidation of the earlier experimental data. An alternative model based on the idea of diabatic thermally activated excitation of FP charge carriers and consecutive lattice "depolarization" will be discussed in detail and implemented at simulations on FP lifetime in Paper II [V. Ligatchev, "On thermal stability of Fröhlich polarons in bulk and nano-structured polar solids II: Diabatic ionization and depolarization," AIP Adv. 14, (2024)]. [ABSTRACT FROM AUTHOR]

This is a companion paper to the previous work [P. H. Yoon, Phys. Plasmas 31, 032309 (2024)] in which the nonlinear susceptibilities of weakly turbulent magnetized plasma are derived under a simplifying assumption of electrostatic interaction. The present paper extends the analysis to a general situation of electromagnetic interaction. The main novelty of the previous and present papers is that by employing the Bessel function addition theorem, the mathematical definitions for the susceptibilities are substantially simplified, a procedure that has not been discussed in the existing literature. In the present paper, a full set of Maxwell's equations are considered in conjunction with the nonlinear Vlasov equation, which is solved by a perturbative method. The result is a fully general nonlinear susceptibility, given in tensorial form, which is applicable for weakly turbulent magnetized plasmas. [ABSTRACT FROM AUTHOR]

The star sensor is the most accurate measurement instrument in the spacecraft attitude measurement system, and the accurate centroid of the star point is the basis for ensuring the performance of the star sensor. Currently, the centroid of the gray method is the most widely used centroid extraction method in practice. Systematic errors caused by the centroid of the gray method and random noise in the detector imaging process are the main factors contributing to the deviation of the star centroiding coordinates. Considering the relationship between the point spread function and the pixel gray value, this paper proposes a centroiding method to reduce the star point centroiding error by fusing a priori information and energy distribution. The star charts are first preprocessed using a curvature filter and Gaussian blur to reduce the random noise. Then the complexity of the point spread function is considered, and the pixel gray values are corrected based on a priori information and gray value fuzzy processing. Finally, the symmetry of the one-dimensional energy distribution is used to quickly determine the sub-pixel deviation to get the star centroid coordinates. Through simulation and physical simulation experiments, the method was verified to be effective, and the extraction accuracy met the requirements of high-precision star sensors. The night sky observation test results demonstrate that the method in this paper can improve the measurement accuracy of the star sensors. [ABSTRACT FROM AUTHOR]

With the increasing demand for the resilient capacity of transformers in high-proportion renewable energy grids, the overload capacity of transformers and the thermal conductivity of winding insulation materials have been put forward as important requirements. In response to these requirements, a novel ceramic high temperature tolerance insulation winding is proposed in this paper and is applied in a ceramic insulated winding transformer. A combination of simulation and experimentation is used to analyze the thermal-flow characteristics of this transformer. The temperature and flow field distribution characteristics of transformers with both winding insulation methods (ceramic and Nomex paper) are compared. The internal mechanism of reflux near the iron core and high voltage winding under forced air cooling is clarified. A superior outside cooling condition is obtained. A prototype ceramic insulated winding transformer is developed and tested to verify the accuracy of the simulation model. The results show that the hotspot temperature of the ceramic insulated winding transformer under natural cooling is 10.7% lower than that of the Nomex paper insulated winding transformer. With forced air cooling of 2, 3, 4, 5, and 6 m/s applied at the bottom, the hotspot temperature of the ceramic insulated winding transformer is 11.4%, 10.5%, 9.7%, 14.0%, and 17.8% lower than that of the Nomex paper insulation winding transformer, respectively. Under forced air cooling, a reflux phenomenon is observed in both transformers in the vicinity of the iron core and high voltage winding due to the formation of adverse pressure gradient region and wall viscous force blocking. The strength of the reflux is affected by the magnitude of the forced air cooling flow velocity and the construction of the transformer. The optimal range of the external cooling flow velocity for the ceramic insulated winding transformer is 3–4 m/s. The errors between the simulated temperature and the measured temperature at the nine monitoring points of the prototype are all less than 5%, which verifies the effectiveness of the simulation model. The experimental and theoretical basis for the design and application of resilient capacity dry type transformers is provided by this research. [ABSTRACT FROM AUTHOR]

As a conventional control approach, the skyhook damping control algorithm can respond to changes in road circumstances but not to those in load circumstances. The skyhook inertance control algorithm, a newly developed control approach, may adapt to changes in load circumstances rather than in road circumstances. The recent introduction of double-skyhook control algorithms has allowed vehicle suspension systems to accomplish both load and road adaptation. This paper presents an experimental investigation contrasting the performance of the double-skyhook configuration to that of the traditional skyhook damper configuration and the skyhook inerter configuration. By integrating the double-skyhook control strategy with semi-active devices with variable inertance and damping, the paper proposes two strategies for coordinating skyhook inertance and skyhook damping control. A controller using the double-skyhook control strategy is designed to employ the Development to Production rapid control prototyping platform. The controller mode is adjusted using MotoTune software to implement control methods. Three tests were conducted under various road conditions, load conditions, and impact conditions for semi-active suspension. Test results indicate that the double-skyhook configuration considerably enhances driving comfort compared to the single-skyhook configuration. Moreover, the greater the deterioration of road conditions and the decrease in load, the more pronounced the enhancement. [ABSTRACT FROM AUTHOR]

A surface defect detection method for hot-rolled steel strips was proposed to address the challenges of detecting small target defects, significant differences in morphology, and unclear defect characteristics. This method is based on multiscale feature perception and adaptive feature fusion. First, based on the spatial distribution characteristics of the steel strip image, redundant background interference is removed using automatic gamma correction and Otsu thresholding. Second, based on the characteristics of surface defects in steel strips, this paper proposes TDB-YOLO (YOLO with a small target detection layer), a Bidirectional Feature Pyramid Network (BiFPN), and Double Cross Stage Partial (CSP) Bottleneck with three convolutions (DC3). To detect small object defects, a small target detection layer with a smaller receptive field focuses on fine-grained features, reducing the model's probability of missed detection. In terms of feature extraction, DC3 enhances the interaction of feature information from different spatial scales, enabling the model to effectively handle features of varying scales. In terms of feature fusion, the BiFPN is used to adaptively fuse deep-level and shallow-level feature information, enhancing the semantic richness of the feature information. Ultimately, the proposed model in this paper achieved an accuracy of 90.3% and a recall rate of 88.0% for surface defects in steel strips. The mean average precision was 90.4%, and the frames per second was 33. The detection performance of this model outperformed those of other detection models, demonstrating its ability to effectively meet the real-time detection requirements of surface defects in industrial scenarios on steel strips. [ABSTRACT FROM AUTHOR]

This Review explores the transformative impact of artificial intelligence (AI) on the early detection of skin cancer, with a specific focus on melanoma, a potentially lethal form of the disease. Beginning with an overview of traditional diagnostic methods and their limitations, this paper delves into the evolution of AI within dermatology, emphasizing its application in image analysis and pattern recognition. A comprehensive examination of AI algorithms for melanoma detection, including machine learning and deep learning models, is provided. This Review critically assesses the performance metrics, training datasets, and comparative analyses with traditional methods. Addressing challenges such as data quality, interpretability, and ethical considerations, this paper outlines future directions, emphasizing ongoing research, algorithm improvements, and integration with clinical practices. Case studies and success stories highlight the real-world impact of AI in dermatology. This Review concludes by summarizing key findings and underlining the pivotal role of AI in revolutionizing early melanoma detection, with implications for personalized medicine and enhanced patient outcomes. [ABSTRACT FROM AUTHOR]

Recent developments on the electron optics simulator (EOS) are reported in this paper. The EOS is a finite element two-dimensional (2D) and three-dimensional (3D) electrostatic particle steady-state trajectory code that has been widely used for beam optics modeling of vacuum electronic devices. To extend the application scope and improve the computation efficiency, four significant advances have been made and are presented in this paper. First, the code is reprogrammed to consider physical models that contain dielectrics and to support charge excitation. Second, more primary particle emission models are added in EOS to meet the needs for simulating electron and ion optics devices for diverse applications. For the precise simulation of the secondary electron emission, the Vaughan model is improved, and the Furman model is newly added in EOS. Finally, the algebraic multigrid algorithm has been embedded in EOS, which can significantly improve the computation efficiency for problems with large-scale matrices. For these developments, the necessary principles and corresponding performance are shown in detail in this paper. [ABSTRACT FROM AUTHOR]

In this paper, we use tracked vehicles as an example to study complex systems and surrogate model building method. Due to the high cost and long development cycle associated with the traditional development approach, involving static design and experimental verification, there is an urgent need to explore an effective dynamic optimization design method to enhance vibration reduction performance. This paper introduces a methodology for constructing a model of complex equipment surrogate, aimed at streamlining subsequent parameter optimization processes. The dynamics model of the tracked vehicle is utilized, and the root-mean-square value of plumb vertical acceleration at the center of mass is selected as the dynamic performance index. The impact of structure parameters on dynamic performance is analyzed, and a range of design parameters are determined. The optimal Latin hypercube experimental design method is employed to generate sample data. A radial basis function neural network, optimized by particle swarm optimization, is used to construct a dynamic surrogate model for the tracked vehicle. The surrogate model constructed in this paper greatly reduces the time cost in optimizing complex equipment parameters. In the past, parameter optimization required conducting numerous simulations to collect data, with each simulation taking about 700 s. However, the surrogate model introduced in this paper only requires ∼100 s for completion. This significant reduction in time not only saves costs but also maintains a high level of accuracy. [ABSTRACT FROM AUTHOR]

The subsurface defects (SSD) of optical elements have a significant impact on the service life and laser damage threshold of the inertial confinement nuclear fusion optical system. Due to the optical diffraction limit, fluorescence microscopy has limited image resolution for detecting SSD in optical elements, making it challenging to meet the requirements for precision detection. A super-resolution method is proposed in this paper for detecting SSD in optical elements based on the fluorescence polarization characteristics of CdSe/ZnS quantum dots fluorescence dichroism. By enhancing the imaging sparsity of adjacent fluorophores through a polarization modulated excitation laser and utilizing the fluorescence polarization modulation algorithm, the resolution is achieved beyond the optical diffraction limit. The results demonstrate that the proposed method in this paper can obtain super-resolution images of SSD in optical elements with at least a two-fold increase in lateral resolution. This approach effectively improves detection accuracy for SSD and holds significant guiding significance. In addition, it also has application value for assessing the quality of high-precision optical elements. [ABSTRACT FROM AUTHOR]

With the goal of "carbon peak and carbon neutrality," the need for environmentally friendly gases to replace SF6, a high greenhouse effect gas, is urgent. C4F7N, as an environmentally friendly gas with the greatest potential to replace SF6 as an arc extinguishing medium in circuit breakers, can be mixed with CO2 to greatly improve the shortcomings of its high liquefaction temperature, and the calculation of the physical parameters of the mixed gas plasma is a prerequisite for the computational simulation of the arc process in the opening of circuit breakers. Because solving the physical parameters is expensive, based on the system of differential equations, this paper adopts several machine learning algorithms by mining the relationship between the data using the known physical parameter data to predict the results of the physical parameters to be solved under certain conditions, which greatly reduces the cost of computation. The machine learning algorithms used in this paper are K-nearest-neighbor regression, decision tree, random forest, support vector machine, and gradient boosting regression, of which for the support vector machine, hyperparameters find it difficult to determine the problem of optimization using the gray wolf algorithm. The prediction results of several algorithms show that they are more accurate and that the problem can be solved better by using the method of machine learning. Finally, the comparison results show that the support vector machine exhibits better performance in most cases and that the gray wolf algorithm can make the results of the support vector machine more accurate. [ABSTRACT FROM AUTHOR]

Understanding the flow behavior of non-Newtonian fluids from an industrial standpoint is crucial. Many industrial and technical activities, such as the extrusion of polymer sheets, the manufacturing of paper, and the development of photographic films, require non-Newtonian fluids. Heat and mass transport have various manufacturing uses. However, classical heat and mass transfer theories (Fourier and Fick laws) cannot anticipate thermal and solute relaxation time occurrences. The purpose of this investigation is to apply the modified Ohm law to the heat and mass transportation systems, which are established by generalized Fourier and Fick's equations, respectively. A three-dimensional Darcy–Forchheimer flow through a porous medium integrating Hall and ion slip effects is studied for a non-Newtonian fluid known as a "Casson nanofluid" with mixed convection across a stretched surface. To investigate heat transfer augmentation, the modified Buongiorno model for nanofluids is used. It covers practical nanofluid properties as well as the mechanics of random motion and thermo-migration in nanoparticles. These groups of Partial Differential Equations (PDEs) that represent the mathematical model are combined with the proper similarity transformations to create an ordinary differential equations system, which is then resolved using the power of the Lobatto IIIA method. Examples of numerical and graphical data are given to show how various physical constraints affect the variation for velocities, temperatures, mass transfer, dimensionless shear stress, as well as Nusselt and Sherwood numbers. It turns out that lowering the Casson fluid parameters' values reduces the velocity in the spatial coordinates (x, y). A rise in the Hall parameter's values ultimately leads to an improvement in the fluid. This paper sheds light on useful applications including power generation, conservation of energy, friction elimination, and nanofluidics. Nonetheless, the work highlights an important point: by carefully adjusting the Casson parameter, thermophoresis parameter, and Brownian motion parameter, the flow of a Casson fluid, including nanoparticles, may be controlled. [ABSTRACT FROM AUTHOR]

The injection of the Direct Current (DC) bias component will lead to oversaturation of the transformer core and affect its safe operation. In this paper, the vector magnetic potential A and winding current I are used as the variables solved in the time-step finite element method to simulate the nonlinear transient magnetization characteristics of the transformer under DC bias, and the fixed-point reluctivity is introduced to deal with the nonlinear iterative problem. The field-circuit coupling relationship is established through the electromagnetic induction law, and the two-dimensional time-step finite element model of the transformer core is found. The dynamic J–A hysteresis model is used to deal with the hysteresis effect of iron cores. The fixed-point reluctivity of difference form is introduced to solve the problem of uneven transition and multi-value of magnetization curve with hysteresis in the iterative process. The determination scheme for the equivalent thickness of the core model and the initial iterative value are discussed. A laminated core transformer is made for experiments, and the accuracy and applicability of the model proposed in this paper are verified by comparing the calculation and experimental results. The influence of different voltages and different DC bias components on the electromagnetic characteristics of the transformer is analyzed. [ABSTRACT FROM AUTHOR]

The paper presents a simple yet rigorous analysis of the transient of the spatial distribution of the kinetic energy of a classical ideal monoatomic dilute gas that passes from non-equilibrium to equilibrium. The proposed approach is event-based, in the sense that the evolution of the system is analyzed as a function of the random number of collisions in a given time interval. Taking a very simple yet realistic model of collision, the paper shows that collisions between atoms lead exponentially to energy equipartition. [ABSTRACT FROM AUTHOR]

Truncation resonances are resonant frequencies that occur within bandgaps and are a prominent feature of finite phononic crystals. While recent studies have shed light on the existence conditions and modal characteristics of truncation resonances in discrete systems, much remains to be understood about their behavior in continuous structures. To address this knowledge gap, this paper investigates the existence and modal characteristics of truncation resonances in periodic bilayer beams, both numerically and experimentally. Specifically, the effect of symmetry of the unit cells, boundary conditions, material/geometric properties, and the number of unit cells are studied. To this end, we introduce impedance and phase velocity ratios based on the material and geometric properties and show how they affect the existence of truncation resonances, relative location of the truncation resonances within the bandgap, and spatial attenuation or degree of localization of the truncation resonance mode shapes. Finally, the existence and mode shapes of truncation resonances are experimentally validated for both longitudinal and flexural cases using three-dimensional (3D) printed periodic beams. This paper highlights the potential impact of these results on the design of finite phononic crystals for various applications, including energy harvesting and passive flow control. [ABSTRACT FROM AUTHOR]

The orbital angular momentum (OAM) wave has shown great potential for improving radar imaging and underwater communication performance due to its helical wavefront phase and infinite orthogonal modes. However, there are currently no known applications of this technology in underwater imaging. In this paper, we employed acoustic OAM wave for underwater imaging and established transceiver signal models using the uniform circular array. We concurrently achieved two-dimensional imaging of azimuth and elevation angles, which differs from radar imaging. We proposed a matching process for the echo signal in the modal domain, the OAM wave beam image's sidelobe decreased by 7.9 dB in the elevation direction and 6.1 dB in the azimuth direction compared to the plane wave, with the mainlobe decreased by 0.2° in the elevation direction and 0.4° in the azimuth direction. Furthermore, this paper introduced OAM wave high-resolution image reconstruction based on the orthogonal matching pursuit (OMP) algorithm. Finally, we implemented broadband acoustic OAM wave for underwater imaging and introduced an image reconstruction method based on the modal domain OMP algorithm. Simulation results demonstrate that the use of OAM wave in underwater imaging is feasible, and the proposed scheme can achieve high-resolution imaging. [ABSTRACT FROM AUTHOR]

Timely and accurate assessment of battlefield strikes can improve the utilization of firepower resources and achieve optimal combat effectiveness. However, due to the complexity and uncertainty of the environment in actual war, it is difficult to obtain accurate target damage information, which can be expressed as uncertain, incomplete, or fuzzy decision information in mathematics. In this paper, the stochastic multi-criteria acceptability analysis method is used to evaluate the damage level of the target under an uncertain environment. We establish a set of characteristic indicators for the target damage effect and use the tracking results of maneuvering targets to determine the degree of target damage. Aiming at the uncertainty of the target data, the upper and lower limit dataset of uncertainty is established, and the membership function of the damage characteristic index is given. Combined with the probability density function, the comprehensive membership function of the damage effect is given, the acceptability index of each damage grade is compared, and the damage effect evaluation with uncertain weight information is given. Based on target vulnerability characteristics and combined with multiple damage elements, a target damage assessment model with multiple damage parameters is established, and the damage results are fitted. We study the relationship between target damage efficiency and various damage parameters. For the optimization strike problem of maximum damage to targets with multiple random incomplete information, a maximum damage optimization model is established using the objective function of maximizing damage probability and the missile firepower coverage area as constraint conditions. Experimental results show that the algorithm used in this paper can effectively solve the damage assessment problem under the condition of random incomplete information. [ABSTRACT FROM AUTHOR]