Bottom Center Research Articles

How a co-actor’s (Un-) reliability modulates goal selection in a novel joint goal-setting paradigm

Sociomotor theory – an extension of ideomotor theory – suggests that actions can also be represented in terms of the effects they elicit from others. But what if those others violate one’s action effect anticipations? Here, we introduce a novel joint goal-setting paradigm to investigate effects of co-actors’ occasional and overall unreliability on an individual’s goal selection. In a first step, the participant moved a target halfway from the bottom center to the top left or right corner of the computer screen. In the second step, the co-actor moved the target to its final left or right position. In a learning block, the co-actor always continued the participant’s target movements. In the test block(s), the co-actor produced congruent action effects in 50% (unreliable) vs. 80% (reliable co-actor) of the trials. Experiment 1 consisted of one (between-participants), Experiment 2 and 3 of two (within-participants) test blocks; in Experiment 3, the co-actor changed between blocks. Results of Experiments 1 and 3 reveal that participants repeated their corner choice more often after incongruent trials, but only when the co-actor was generally reliable. Implications in terms of sociomotor action control and joint action are discussed.

Experimental and numerical studies on corrosion-resistant aluminium foam sandwich panel subject to low-velocity impact

Aluminium foam sandwich panels (AFSPs) have a high impact resistance and are suitable for a wide range of engineering applications. To improve corrosion resistance, this paper proposes an anti-corrosion sandwich panel with stainless steel as the upper sheet. Drop hammer impact tests were performed on a total of ten AFSPs to investigate their dynamic response and failure patterns. To assess the deformation performance of AFSPs, a laser displacement meter was used to obtain the bottom centre displacement. The effects of the impact energy and the thickness of each component of AFSPs on the peak impact force and deformation performance were studied. Test results showed that the thickness of each component had notable effects on the impactor and bottom displacements. In addition, the effect of the unit mass of the components in AFSPs on decreasing the bottom displacement was discussed. Compared to increasing the aluminium foam and lower sheet thicknesses, increasing the upper sheet thickness was more effective in decreasing the bottom displacement. A finite element model of AFSPs was developed to conduct parameter analysis, indicating that impactors with larger diameters resulted in higher peak forces and reduced deformation of AFSPs.

Seismic Response of Foundation Settlement for Liquid Storage Structure in Collapsible Loess Areas

To investigate the impact of foundation settlement in loess areas on the dynamic response of liquid storage structure (LSS) under seismic motion, a finite element analysis model of the liquid–solid coupling of LSS was established using ADINA V9.6 software. By analyzing the dynamic response patterns of LSS under seismic motion with foundation failure, this study examines the effects of foundation failure and the direction of seismic wave incidence on the equivalent stress, maximum shear stress, wall displacement, and liquid sloshing wave height of the structure. The results indicate that among the three foundation failure scenarios, foundation failure at the center of the tank bottom has the least impact on the structural dynamic response. In contrast, foundation failure affecting one-fourth of the tank base has the greatest impact. Furthermore, compared to seismic motion along the X-axis, the dynamic response of the structure is more significantly affected when seismic motion co-occurs along the X-Z-axis.

Numerical Study on the Impact of the Richardson Number on Convection in an Enclosure, with Moving Sidewalls for Three Aspect Ratios: A = 1, 2 and 0.5

Using mathematical models, this research investigation seeks to explore how varying aspect ratios and the Richardson number impact the mixing effectiveness, fluid flow velocity, and heat transfer characteristics in a rectangle-shaped space where cooling occurs along the sides and warm with a steady temperature exists throughout the 80% of the bottom section's center. Discretizing the governing equations through the finite volume approach, we solved them iteratively using the Tri-diagonal Matrix Algorithm, where pressure-velocity coupling was successfully implemented via the SIMPLER procedure. Innovative approaches for convection and diffusion terms involved employing a power-law difference scheme alongside a central differential scheme. In various simulations with specified parameters (Re = 100, Pr = 0.71), we visualized results in forms like streamlines, isothermal lines, and temperature/velocity profiles, along with local and average Nusselt numbers. We observe five unique structure formations during flow behavior by analyzing how Richardson numbers impact heat transmission within a specific geometric configuration (enclosure size A = 1). A change in aspect ratio leads to improved control over fluid movement while minimizing structural distortion. A subtle rise in heat transmission emerged as the average Nusselt number and Richardson number intersection strengthened force convection's domination while experiencing significant escalation under conditions conductive to natural convection. Decreasing the aspect ratio increased heat transfer efficiency when the Richardson number rose.

Four new earthworm species of the genera Amynthas and Metaphire (Oligochaeta, Megascolecidae) from Hunan and Anhui provinces, China.

This paper describes four new species earthworms from Hunan and Anhui provinces, China, Amynthasxiangtanensis Qiu & Jin, sp. nov., Amynthastaoyuanensis Qiu & Jin, sp. nov., Amynthasxuanchengensis Jin & Li, sp. nov. and Metaphiredonganensis Jin & Jiang, sp. nov. Amynthasxiangtanensis sp. nov., and A.taoyuanensis sp. nov. belong to the Amynthascorticis group. Both have four pairs of intersegmental spermathecal pores in 5/6-8/9; male pores in segment XVIII, separated by 1/3 of body circumference, each on top of a slightly raised porophore, surrounded by several tiny genital papillae. Amynthastaoyuanensis sp. nov. prostate glands are degenerated. Amynthasxuanchengensis sp. nov. belongs to the Amynthasmorrisi group, it has two pairs of spermathecal pores in 5/6 and 6/7; male pores in XVIII, separated by 1/3 of body circumference, each on top of a slightly raised, circular porophore. Metaphiredonganensis sp. nov. belongs to the Metaphirehoulleti group. It has three pairs of spermathecal pores in 6/7-8/9; male pores in XVIII, separated by 1/3 of body circumference, each on the bottom center of the longitudinal copulatory chamber.

Multi-scale approach to hydrogen susceptibility based on pipe-forming deformation history

Hydrogen-induced-cracking initiates without external loading due to residual stresses. Pipe manufacturing process composed of crimping, U-ing, O-ing, and expansion has a major impact on local hydrogen concentration, as strain pattern evolves from one forming step to another, causing residual stresses that serve as driving force for hydrogen diffusion. The novelty of the presented work lies in the development of a multi-scale approach that links the residual stresses from the macroscopic pipe-forming process with locally dissolved hydrogen atoms in microstructure under the consideration of microstructural heterogeneities to identify areas susceptible to hydrogen-induced-cracking. First, a 3d-pipe-forming-model was built. Second, representative volume elements with lattice defects were generated to analyze hydrogen trapping in microstructure. Third, representative volume elements were placed in the pipe via sub-modeling, so that local loading history of the pipe was assigned to microstructure models. At the end of the pipe-forming process, representative volume elements were loaded with hydrogen on the surface and final hydrogen concentration was simulated based on residual stresses, considering microstructural effects such as grain size/shape, crystallographic texture and hydrogen traps, e.g. dislocations, voids and inclusions. On meso-/macroscale, a combined isotropic–kinematic hardening material model was implemented, while on microscale, a phenomenological crystal-plasticity-hydrogen-diffusion model was coded. According to the multi-scale simulations under the consideration of microstructural effects the bottom center position in the pipe was detected to be critical to hydrogen-induced-cracking as the maximum local hydrogen concentration was predicted at that location. Based on the loading history hydrogen-induced-cracking susceptibility increases from voids to hard and soft non-metallic inclusions.

RESULTS OF ANALYTICAL RESEARCH OF THE SEED PROCESSOR OF THE IMPROVED SOWING SECTION OF THE PNEUMATIC SEEDER

According to preliminary research, the primary factor influencing the accuracy of seed placement by pneumatic seeders is the process of transferring seeds from the metering device to the point of direct entry into the furrow formed by the coulter in the soil. The first factor is related to the high velocity of the air stream, which increases the risk of seed dislodgement from the seed boot and its placement outside the furrow. This problem can be addressed by installing a seed retarder above the seed boot. The second factor lies in the imperfect shape of the seed channel in the seed boot. Seeder developers, aiming to create an "ideal" seed bed in the soil, often underestimate the importance of the shape of the seed channel. Due to the high speeds at which modern pneumatic seeders operate (1.5–4.2 m/s) and their constant vibration, seeds in the seed channel of the seed boot constantly collide with its walls, leading to changes in direction and speed of movement. This chaotic seed movement results in decreased seeding accuracy. The third factor is the complete absence or incorrect installation of a seed retarder, which should prevent seed dislodgement from the bottom of the furrow. As a result of the analytical studies, the kinematics of seed motion after ejection from the seed boot and rebound from the furrow bottom and seed retarder were considered. The obtained dependencies include the maximum height of the parabolic seed trajectory y3`, the difference in distance between the points of rebound from the ground surface and the distance traveled by the seeder Δx from the initial seed velocity Vp0, the angle of their ejection α, the height of the seed retarder placement Hu, and the angle of its inclination β. By satisfying the conditions and for the obtained dependencies in Wolfram Cloud, the following rational parameters were obtained: α = 47°, β = 0°, Hu < 0.134 m. To ensure consistent seed placement at the center of the furrow bottom after rebounding from the seed retarder with a slight trajectory deviation (± 0.01 m), the profile shape of its working surface should be parabolic with the focus at point pf = 0.134 m.

“The Anamorphic Journey”: Jean‐Luc Marion on Revelation

AbstractIn part four of D'ailleurs, la Révélation (2020) Jean‐Luc Marion evokes the state of being seized by a saturated phenomenon, whether divinely revelatory or not, which guides one “across the desert on an anamorphic journey [parcours d'anamorphose].” The figure of anamorphosis is well‐known to anyone familiar with sixteenth‐century art, visual or literary; it comes directly from experiments with mirrors or perspective, giving rise with the latter to examples of affine transformation. Undoubtedly, Hans Holbein the Younger's double portrait “The Ambassadors” (1533) is the best‐known visual example: if one looks directly at the canvas in the National Gallery in London, one sees a diagonal blur across its bottom center, beneath Jean de Dinteville (1504‐1555), French Ambassador to London, and Georges de Selve (1508‐1541), Bishop of Lavaur and French Ambassador to the Republic of Venice. Only when one views the blur from a particular point—either low on the left‐hand side or high on the right‐hand side—can one see that it is a skull. The vanity of human achievement or, worse, human pride, is made manifest only when the artwork is viewed from a perspective that one is constrained to adopt. The sole sign of hope is a crucifix in the top left of the canvas.

A methodology for laser tool setters calibration and its precise mathematical model

On-machine tool setting is a pivotal approach in achieving intelligent manufacturing, and laser tool setters have become a crucial component of smart machine tools. Laser tool setters play a crucial role in precisely measuring the dimensions of cutting tools during the part machining process, focusing on tool length and diameter. As a measuring instrument, the positions of the laser axis of the laser tool setter need to be accurately calibrated before use. However, in actual calibration scenarios, traditional calibration methods face challenges due to installation errors in the tool setter and geometric errors in the measuring rod. To address this issue, this study proposes a novel calibration method. Initially, the calibration mechanism of the laser beam axis is established. Based on the accurate mathematical model of the laser beam and the measuring rod, and using the polygon clipping algorithm, the mathematical mechanism of the laser tool setter's work is established. Then, a novel method is introduced to calculate the compensation distance between the laser beam reference point and the rod bottom center point at each moment during calibration. Furthermore, by utilizing the kinematic chain of the tool setter calibration system, a new calibration method is developed to accurately calibrate the position of the laser beam axis in the machine tool coordinate system. Finally, the accuracy of the calibration method is verified through simulation experiments and calibration tests. This method improves the calibration accuracy of the tool setter, and the mathematical model of the laser tool setter can be extended to the measurement of tools, thereby improving the precision of tool measurements. This research significantly improves the efficient production performance of smart machine tools.

Effects of solar radiation and tree planting on photochemical reaction kinetics in urban street canyon

The investigation of the impact of tree planting on photochemical reaction kinetics and dispersion characteristics of reactive pollutants in street canyons under actual solar radiation remains a pertinent subject for research. The numerical models were employed and validated through wind-tunnel experiments to investigate the dynamic and thermodynamic effects of tree planting (LAD = 4.77) on turbulent flow, heat transfer, and NOx-O3 photochemical reaction in urban street canyons. The effects of solar radiation at three local solar times (LST0900, LST1200 and LST1500) and three background O3 concentrations (20 ppb, 100 ppb and 200 ppb) were considered. The ozone depletion rate (dO3) was defined to measure the photochemical reaction equilibrium. The results show that the presence of trees can offset the impact of varying LST solar radiation and promote greater stability in flow structures within street canyons. Specifically, a stable clockwise main vortex is observed in the upper part, while multiple smaller vortices form more regularly in the lower part. Compared with no trees, planting trees can effectively reduce the temperature by about 5 K in the lower part of street canyon through the shading and transpiration cooling effects. In conjunction with its dynamic effects, the tree planting can also effectively reduce the average concentration of pollutants before the reaction. It results in a predominant accumulation of NOx near the pollution source at the bottom center, thereby mitigating their detrimental impacts on both windward and leeward sides. Additionally, under the same background O3 concentration, tree planting can also influence the equilibrium process of photochemical reactions and enhance their reverse reaction leading to ozone depletion. The findings of this study contribute to a deeper understanding of the impact of tree greening on the local microclimate within urban street canyons.

Study on three-dimensional model of ventilation drying and heat and mass transfer of bulk grain pile based on discrete-continuous media

Abstract In order to ensure the safety of grain storage and explore the mechanisms of water and heat transfer during the drying process of grain piles, this paper takes wheat as the research object, uses a thermal conductivity analyzer to measure the thermal conductivity and specific heat capacity of wheat, and obtains a linear relationship between the heat constant and water content of wheat. COMSOL software was used to establish a three-dimensional model of ventilation drying and heat and mass transfer of bulk grain piles based on discrete continuum media, which simulated the temperature and humidity changes during the drying process of the grain pile. The model was verified by a thin layer drying experiment. The results show that the simulated values of temperature and water content obtained by the wet heat transfer model are in good agreement with the experimental values, and the maximum errors are 2.14 % and 5.68 % respectively. During the drying process, the grain temperature of wheat at the bottom of the grain pile increased rapidly, compared with that at the top of the grain pile, and the temperature of the wheat at the center was higher than that at the edge. At the end of drying, the moisture content from highest to lowest was top edge > top center > bottom edge > bottom center. Therefore, the model can be used to further study the changes of grain pile temperature gradient and water gradient.

Improving flatness of machined surface in rotating cathode electrochemical milling

Electrochemical milling has broad application prospects for machining large aeronautical thin-walled components. This is because this technique has no cutting force, has no heat-affected zones, and is considerably flexible. In contrast to the non-rotating tool cathode of traditional electrochemical milling, the rotating cathode used in electrochemical milling has more promising prospects because it has the same motion mode as the milling cutter employed in mechanical milling. However, because of the uneven electric quantity supply from the cylindrical rotating cathode, the machined surface typically has a curved profile with inadequate surface flatness; this is the main drawback of rotating-cathode electrochemical milling. To improve the flatness of surfaces processed by rotating-cathode electrochemical milling, a novel multichannel cathode with the outlet hole arrangement that can improve the uniformity of electric quantity supply is proposed. Numerous large outlet holes are bored at the bottom center of multichannel rotating cathode. Numerical simulation results indicate that these holes cause a decrease in the electric quantity supply from the inner area at the bottom of the cathode from the perspectives of electric and flow fields, minimizing the unevenness of the electric quantity supply distribution. Validation experiments prove that compared with previously reported rotating cathodes, the straightness index and depth error of the surface machined by novel multichannel cathode are reduced by 80.9 % and 69.4 %, respectively. After obtaining grooves with flat surfaces, the step-over distance required to machine a plane using a multichannel rotating cathode increases; meanwhile, the flatness of the machined plane significantly improves. With the applied voltage of 25 V, electrolyte pressure of 0.2 MPa, initial inter-electrode gap of 0.2 mm, and cathode rotational speed of 500 rpm, a 42 × 40 mm plane is finally machined, whose planeness index (Δhp) is only 0.047.

Elimination of gas entrapment in droplet-based 3D printing by induced electric-field

Gas entrapment during droplet deposition may induce pinhole defects in droplet-based 3D printing. However, achieving effective suppression of gas entrapment is challenging given that gas entrapment behavior is the physical essence of droplet impact. Inspired by that charged droplets will be deformed in the electric field, a method of suppressing gas entrapment by weakly charging the droplet was proposed. Here, a numerical model is developed to systematically investigate the gas entrapment behaviors during neutral droplet and charged droplet deposition. Results show that the electric field will be induced before the instant of droplet impact on the substrate, which fundamentally changes the gas entrapment behavior. Moreover, the competition mechanism between Maxwell stress and lubrication pressure during droplet deposition is revealed, and the pressure inside and outside the droplet bottom profile is quantified. Compared with the neutral droplet, the additional electric stresses act against the lubrication pressure, which increases sharply before the droplet touches the substrate. When the charge level reaches a critical value, the electric stresses are slightly stronger than the lubrication pressure at the bottom center, and the decrease rate of electric stresses along the horizontal distance r is higher than that of gas film pressure, leading to a central touchdown with residue concentric circle gas rings. Furthermore, the evolution of phase fraction, velocity field, and pressure field during droplet deposition with different charge level is investigated comprehensively. Based on this, the dimensionless scale of critical charge level to fundamentally eliminate gas entrapment is obtained. This work may provide new insights into various applications involving droplet deposition, such as eliminating pinhole defects in droplet-based additive manufacturing.

Study on the damage behaviour of titanium alloy laser-welded blank during hot gas pressure forming

The damage behaviour of titanium alloy laser-welded seam during hot gas pressure forming was studied by experiment and simulation. The GTN damage model was used to simulate the hot gas pressure forming process of the welded blank. The evolution of the void volume fraction during the forming process was obtained. Hot gas pressure forming experiments of cup-shaped parts were carried out. The microstructure at different positions of the cup-shaped part was observed by scanning electron microscope. Results show that the damage to the weld seam during hot gas pressure forming was mainly related to the strain. The damage of the inside fillet near the flange develops most rapidly, and it easily cracks due to the large deformation during the free bulging stage. The damage on the bottom centre develops slowly at the free bulging stage. After the bottom of the cup-shaped part contacted the die, the volume fraction of damage on the bottom center continued to increase firstly and then reached to a stable value gradually. Various micro cracks were observed during the hot gas pressure forming. The volume fraction of cracks increased with the increasing strain, and the small cracks gradually grew, expanded, and merged to form larger cracks. It is important to control the maximum strain of the weld seam during the forming to avoid possible harmful damage.

Wave-converging pressure increase in curved cylindrical rotating detonation combustors

The internal combustion structure of a curved cylindrical rotating detonation combustor (RDC) was experimentally investigated through optical observation and pressure measurements. Experiments were conducted under low back pressure conditions using two combustion chambers having, in both cases, an internal diameter of 17.5 mm, a curvature of radius of 38.1 mm, and an outlet angle of 90 deg, with gaseous C2H4 and O2 as the propellants. One was made of SUS and the other of resin. In addition to vibrations and bottom center pressure, pressure distribution on the sidewalls was measured for the SUS combustor, and high-speed camera observations of self-luminescence from the radial direction were conducted for the resin combustor. These measurements were compared by varying the equivalence ratio. The frequency analysis results obtained from vibrations and self-luminescence indicated that the strongly-coupled detonation mode exhibited a higher peak frequency, suggesting that the detonation waves may have different propagation speeds or rotational positions. In terms of pressure distribution and self-luminescence, only the strongly-coupled detonation mode inside near the bottom surface exhibited high pressure and brightness values. This suggested the potential for converging pressure by employing rotating detonation waves and a curved tube.

Morphology of Silver Particles and Films Arising from Particle‐Free Silver Ink Droplet Evaporation

AbstractThe evaporation of particle‐free silver ink droplets on heated substrates directly impacts the morphology of the resultant silver particles and electrically conductive inkjet‐printed films. In this work, COMSOL Multiphysics simulations of the droplet evaporation process are used to help explain the fluidic processes responsible for the experimental observations. The results show that the silver particle morphology depends on its location within the evaporating droplet where large particles (3 to 5 µm) accumulate at the center and smaller ones (1 to 2 µm) in the area beyond the central region. The smallest particles (≈500 nm) are near the contact line. Without the fluoro‐surfactant FS‐31, an inner ring with 3 µm particles also appears within the evaporating droplet. The large particles at the central region originate from the fluid near the droplet's apex due to the accumulation of polyacrylamide in the concentrated ethylene glycol solvent near the flow‐abundant apex. Furthermore, the capillary flow along the fluid–air interface transports silver ions and particles throughout the droplet, causing the larger particles to fall onto the substrate at the central vortex, forming the inner ring. The simulations also demonstrate that the evaporating droplet heterogeneously accumulates ethylene glycol in a sandhill formation at the bottom center.

GPro3D: Deriving 3D BBox from ground plane in monocular 3D object detection

Considering the inherent ill-posed nature, monocular 3D object detection (M3OD) is extremely challenging. The ground plane prior is a highly informative geometry clue in M3OD. However, it has been neglected by most mainstream methods. This paper introduces an original M3OD framework that leverages the ground plane to directly derive the object’s 3D Bounding Box (BBox) and 3D attributes geometrically. We identify and tackle three key factors that limit the applicability of the ground plane: the projection point localization issue, the ground plane tilt issue, and the lack of ground plane annotation issue. For the projection point localization issue, we propose leveraging the car’s explicit and salient wheel pixels, which are easier for the neural network to detect compared to the bottom vertices or the bottom center of the 3D BBox. To tackle the ground plane tilt problem, we propose a vertical-edge-enhanced horizon line detection algorithm to precisely deduce the ground plane equation. Moreover, using only M3OD labels, wheel pixel and horizon line pseudo-labels can be easily generated to train the network without extra data or annotation cost. Extensive experiments demonstrate the effectiveness and superiority of our framework over previous methods.

Numerical Simulation of Solvent Evaporation in a Reactive Silver Ink Droplet Deposited on a Heated Substrate.

Understanding the movement of silver ions (Ag+) in the solvent of a thermally evaporated particle-free reactive silver ink droplet is essential for optimizing the electronic inkjet printing process. In this work, a numerical study based on the Navier-Stokes equations is used to examine the microflows inside the evaporating solvent of a reactive silver ink droplet and to predict the morphology of the resultant Ag particle aggregations that form during the heat-activated processes. The droplet evaporation of the water-ethylene glycol ink solvent (H2O-(CH2OH)2) is simulated using COMSOL Multiphysics software. The model assumes that the evaporating fluid is heterogeneous due to the mass transfer of ethylene glycol molecules throughout the droplet by capillary flow. A layer of concentrated ethylene glycol forms at the fluid-substrate interface during solvent evaporation if the substrate is heated. The concentrated ethylene glycol molecules are then transported inward by the capillary action, and the resultant Ag particles, arising from the thermally driven reactions, accumulate at the bottom center of the drying droplet. The numerical simulations demonstrate that the droplet evaporation process depends on the water concentration in the solvent, substrate temperature, surface tension, and natural convection. Furthermore, the capillary flow dominates the fluid flow inside the evaporating droplet, causing some Ag particles to accumulate at the contact line, the commonly observed "coffee-ring effect". The results provide new insights into the chemical reactions that produce experimentally observed silver particle aggregations during the reactive silver ink droplet evaporation process and help establish realistic process parameters for improving the quality of inkjet-printed conductive silver films and electronic circuit microtraces.

A Novel Parallel-Plate Dielectric Resonator Method for Broadband Complex Permittivity Measurement in the Millimeter-Wave Bands

This article proposes a novel measurement method based on parallel-plate dielectric resonator (PPDR) for determining complex permittivity of low-loss dielectric materials over a wide frequency range. Two 1.0-mm coaxial probes are placed symmetrically as a coupling structure in the center of top and bottom of the PPDR, and only the TM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm{0np}}$</tex-math> </inline-formula> resonant modes will be selectively excited. For each value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$p$</tex-math> </inline-formula> , the resonator will operate over a specific frequency range, within which there are usually multiple frequency points available for testing. Based on this unique feature, dielectric constants of cylindrical or disk-shaped samples can be measured from less than 20 up to 110 GHz by utilizing TM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm{0np}}$</tex-math> </inline-formula> high-order modes. Rigorous analysis of the PPDR based on the electromagnetic field matching method is carried out and verified numerically. Moreover, the PPDR method is further validated experimentally by measuring several specimens processed from well-known materials, the main sources of measurement uncertainty are also analyzed in detail, and some recommendations are made accordingly. The results show that the PPDR method can perform high-accuracy measurement of complex permittivity in the millimeter-wave bands, even when the sample thickness exceeds the maximum value limited by the current state of the art.

Characterization and mechanism of natural rubber composites reinforced by modified calcium sulfate whisker

AbstractThis study concentrated on the mechanical properties of natural rubber (NR) composites [modified calcium sulfate whisker (MCSW)] and the reinforcement mechanism of MCSW on NR. First, anhydrous CSW with an orthogonal crystal system bottom center structure was prepared by hydrothermal method. Subsequently, MCSW was obtained by treating whiskers with inorganic, organic compounds, which effectively coated the surface of the whiskers with an average thickness of 40.85 nm, making the surface change from hydrophilic to hydrophobic. The CSW/MCSW filler was added to the NR under the optimum experimental conditions of 70°C, 12 min, 5 times of rolling, 140°C, and 1 h of curing time. The results showed that the tensile strength, elongation at break, and crosslink density of the NR composites with 15 phr of MCSW added were increased by 80.8%, 9.0%, and 80.2%, respectively, compared with the NR without the filler. The mechanism of MCSW improving the performance of composites was revealed from vulcanization kinetics and interfacial thermodynamics. In this work, a new type of high‐efficiency environmental protection NR filler reinforcing agent was developed.