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This study investigates terahertz (THz) wave scattering from a simulated lunar regolith surface, with a focus on the Brewster feature, backscattering, and bistatic scattering within the 325 to 500 GHz range. We employed a generalized power-law spectrum to characterize surface roughness and fabricated Gaussian correlated surfaces from Durable Resin V2 using 3D printing technology. The complex dielectric permittivity of these materials was determined through THz time-domain spectroscopy (THz-TDS). Our experimental setup comprised a vector network analyzer (VNA) equipped with dual waveguide frequency extenders for the WR-2.2 band, transmitter and receiver modules, polarizing components, and a scattering chamber. We systematically analyzed the effects of root-mean-square (RMS) height, correlation length, dielectric constant, frequency, polarization, and observation angle on THz scattering. The findings highlight the significant impact of surface roughness on the Brewster angle shift, backscattering, and bistatic scattering. These insights are crucial for refining theoretical models and developing algorithms to retrieve physical parameters for lunar and other celestial explorations. [ABSTRACT FROM AUTHOR]

This study evaluates the potential of erbium, chromium-doped:yttrium, scandium, gallium, and garnet (Er,Cr:YSGG) laser irradiation to modify the titanium surface for optimal seeding of fibroblasts and osteoblasts in the treatment of peri-implantitis. Titanium discs were treated using the Er,Cr:YSGG laser, an ultrasonic device with a stainless tip, or titanium scalers. Changes in surface properties were analyzed by profilometer and scanning electron microscopy (SEM). Murine fibroblast and osteoblast adhesion and proliferation were evaluated qualitatively and quantitatively at 24 and 72 h. Profilometric surface topography and SEM showed that titanium scalers and ultrasonic debridement techniques significantly changed the structure of the machined and rough titanium surfaces. The Er,Cr:YSGG laser irradiation, on the other hand, did not alter titanium microstructures. The Er,Cr:YSGG laser irradiation with the 40 Hz group showed a significantly higher attached fibroblast cell numbers than the titanium scaler group at 72 h after treatment (p = 0.023). Additionally, the number of the attached osteoblasts in the Er,Cr:YSGG laser irradiation with the 40 Hz group was significantly higher than that of the no-treatment groups 24 h after treatment (p = 0.045). The Er,Cr:YSGG laser effectively promoted adherence of fibroblasts and osteoblasts to the titanium surface without significantly altering the titanium surface, suggesting its superiority for treating peri-implantitis. [ABSTRACT FROM AUTHOR]

This paper presents the experimental and finite element analysis of surface asperity geometry during the running-in phase of rolling contact. Previous research efforts typically relied on simulating various shapes of asperity geometry to elucidate rough surface characteristics. However, this approximation did not accurately represent the actual surface asperities. In this study, a rolling contact rig was fabricated, and periodic surface scans were utilized to track the deformation of roller surface asperities. The experimental findings reveal a notable 69% reduction in surface roughness throughout the running-in phase, alongside showcasing the deformation of asperity geometry. Subsequently, a simulation model is developed using data derived from these experiments. Stress analysis conducted on individual and multiple asperities illustrates a decrease in contact stress over time, indicating a transition in contact behavior from plastic to elastic. Furthermore, simulations involving multiple asperities demonstrate an expansion in contact length as roughness diminishes with increasing cycles. Initially, only the highest peaks of asperities make contact, resulting in elevated contact stress. However, as rolling cycles progress, a greater number of asperities come into contact, leading to a more uniform distribution of load. Notably, the more prominent asperities endure significant contact stress and deformation compared to their smaller counterparts. [ABSTRACT FROM AUTHOR]

Interventional procedures for the recanalization of blood vessels to treat deep vein thrombosis carry a high risk of vessel wall injuries or hemorrhaging. Focused ultrasound (FUS) has been used to non-invasively break down blood clots that occlude the vessels in both in vitro and in vivo studies. Previous studies have either used thrombolytic drugs or ultrasound contrast agents (e.g., microbubbles) in combination with FUS. Several studies have applied very high peak-negativepressures (PNP) during FUS treatment to achieve successful thrombolysis without the use of contrast agents. In the current study, we demonstrated that cavitation activity could be significantly enhanced by placing a nitinol wire, whose surface was roughed by laser etching, in the focal region of a FUS field. We demonstrated in vitro in a mock thrombosis that the thrombolysis efficacy of a 500 kHz FUS transducer was significantly enhanced using a surface-etched nitinol wire as compared to an unetched nitinol wire, whereas FUS-alone at the same pressure level did not result in any thrombolysis. These results suggest that a surface modified nitinol catheter exposed to FUS can result in intense cavitation activities leading to enhanced thrombolysis without the use of additional pharmacological or contrast agents. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Taking the surface profile of C45 steel grinding as the research object, a two-dimensional finite element contact model of rough surface and smooth rigid surface was established by using ANSYS software, and the stress distribution characteristics and rules of contact surface were analyzed under 0–10 MPa normal load. On this basis, the force-magnetic coupling model was established by using ANSYS APDL language. Furthermore, the influence of stress under on leakage magnetic field of contact surface under different load conditions was studied. The results indicated that according to the zero-crossing point of the normal component of the leakage magnetic field or the extreme point of the tangential component, the number of stress concentrations on the contact surface and the stress level of the corresponding area can be effectively determined. This innovative approach offers valuable insights for future studies on surface contact stress distribution between components. [ABSTRACT FROM AUTHOR]

In this work, an efficient numerical method is proposed for three-dimensional (3D) electromagnetic scattering from multiple coated targets buried under a two-dimensional dielectric rough surface. In the proposed method, the interior region of each coated target is regarded as an independent subregion. The field within each coated target is modeled by 3D vector finite element method (FEM). The multiple scattering interactions between the buried targets and between targets and rough surface are considered by the electric field integral equation and the Poggio–Miller–Chang–Harrington–Wu integral equations, respectively. The fields inside and outside the targets are coupled together via boundary conditions on the boundary of each target. To improve the calculation efficiency and reduce the memory requirement, the fast multipole technique is used in our method. The presented method is numerically validated by comparing it with method of moments and conventional FEM-boundary integral method (BIM). The results indicate that, compared with traditional FEM-BIM, our method has significant advantages in computational efficiency and memory requirements. [ABSTRACT FROM AUTHOR]

We present an innovative Lagrangian dual-mechanism model for simulating versatile surface tension phenomena, designed to replicate the intricate interplay of liquids with textured solid surfaces and the emergence of gas bubbles. This model synergistically merges the influence of inter-particle dynamics with global surface curvature, ensuring a harmonious balance between the intricacies of fluid motion and the imperative of surface area reduction. A cornerstone of our methodology is the incorporation of Laplace pressure differentials across fluid boundaries, enhancing interface stability and enabling the depiction of distinctive droplet oscillations driven by fluctuations in kinetic energy. Additionally, our model introduces a dual-scale smoothing kernel, meticulously engineered to resolve the subtle nuances of surface textures. The prowess of our model is exemplified in its ability to simulate superhydrophobic behaviors, underscoring its utility. Integrated within the smoothed particle hydrodynamics framework, our model offers efficient simulation performance, contributing a valuable tool to the field of fluid simulation. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Xi'an Jiaotong University is the property of Editorial Office of Journal of Xi'an Jiaotong University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

After more than two decades of development, Persson's theory has become one of the dominantly used theoretical tools to analyze the interaction between a nominally flat rough surface and a rigid flat. The original theory (Persson in J. Chem. Phys. 115(8):3840–3861, 2001) tends to overestimate and underestimate the relative contact area and strain energy, respectively, for linear elastic purely normal contact. Several fudge factors, obtained empirically based on numerical solutions, have been used to amend the strain energy associated with each wavenumber, resulting in scale history-dependent formulations for the relative contact area and probability density function (PDF) of contact pressure, which significantly complicate the solution process. We provide a new fudge factor that results in simple formulations of the relative contact area and PDF of contact pressure, which only relies on the present scale. Compared with the relative contact area and PDF of contact pressure solved by Green's Function Molecular Dynamics (GFMD), Persson's theory using the new fudge factor shows similar accuracy to other variants. Among all variants of Persson's theory, the use of the new hybrid formulation of strain energy results in the best agreement with GFMD. Using the new fudge factor, various interfacial properties (e.g., the average interfacial gap) can be derived with a simple form, and solved more quickly, with acceptable accuracy. [ABSTRACT FROM AUTHOR]

Plastoelastohydrodynamic lubrication of rough surfaces (R-PEHL) is a cutting-edge area of research in interface fluid-structure coupling analysis. The existing R-PEHL model calculates the elastic-plastic deformation of rough surface by the Love equation in a semi-infinite space smooth surface, which deviates from the actual surface. Therefore, it is an innovative work to study the exact solution of elastic-plastic deformation of rough surface and its influence on the solution results of R-PEHL model. In this paper, a new contact calculation model of plastoelastohydrodynamic lubrication (PEHL) with three-dimensional (3D) rough surface is proposed by integrating numerical method of EHL and finite element method. The new model eliminates an original error introduced by the assumption of semi-infinite space in contact calculation, providing wide applicability and high accuracy. Under the given rough surfaces and working conditions, the study reveals that: (1) the oil film pressure calculated by the new model is lower than that of the smooth surface in semi-infinite space by 200–800 MPa; (2) the Mises stress of the new model is 2.5%–26.6% higher than that of the smooth surface in semi-infinite space; (3) compared with the semi-infinite space assumption, the rough surface plastic deformation of the new model is increased by 71%–173%, and the local plastic deformation singularity may appear under the semi-infinite space assumption; (4) the plastic deformation caused by the first contact cycle on the rough surface of the new model accounts for 66.7%–92.9% of the total plastic deformation, and the plastic deformation of the semi-infinite space accounts for 50%–83.3%. This study resolves the contradiction between the smooth surface assumption and the rough surface in the existing R-PEHL model, establishing a solid logic foundation for the accurate solution of R-PEHL model. [ABSTRACT FROM AUTHOR]

To fully evaluate the influence of the rough surface (𝜎) and speed (𝜔) of the crankpin bearing on the engine power, a combination model of the slider crank mechanism and crankpin bearing's lubrication is established to calculate the mathematical equations for the simulation. Three indexes of the bearing-capacity (𝑊), friction-force (𝐹), and friction-coeficient (𝜇) are used to evaluate the influence of the change of the crankpin bearing's speed and rough surface on the engine's power. The study shows that increasing 𝜔 not only effectively reduces the load capacity of the crankpin bearing but also increases the 𝐹 and 𝜇 in the engine's crankpin bearing, thereby directly reducing the engine's power. Besides, the reduction of 𝜔 also reduces the bearing-capacity of the crankpin bearing. To optimize the engine's power, the engine's speed should be maintained at 2000 r/min to improve the engine's power. In addition, under the effect of the rough surface of the crankpin bearing, the 𝑊 of the crankpin bearing is insignificantly affected by the change of the rough surface while both the 𝐹 and 𝜇 are greatly affected. In particular, the maximum 𝐹 at 𝜎 = 8 μm and 𝜎 = 10 μm is increased by 68.3 % and 77.7 % in comparison with the maximum 𝐹 at minimum value of 𝜎 = 2 μm, respectively. Therefore, in the design of the engine, the rough surface of the crankpin bearing should be reduced to improve the engine's power. Additionally, the design parameters of the crankpin bearings should also be optimized to further improve the engine's power. [ABSTRACT FROM AUTHOR]

Mechanical joint interfaces are widely found in mechanical equipment, and their contact stiffness directly affects the overall performance of the mechanical system. Based on the fractal and elastoplastic contact mechanics theories, the K-E elastoplastic contact model is introduced to establish the contact stiffness model for mechanical joint interfaces. This model considers the interaction effects between micro-asperities in the fully deformed state, including elasticity, first elastoplasticity, second elastoplasticity, and complete plastic deformation state. Based on this model, the effects of fractal parameters on normal contact stiffness and contact load are analyzed. It can be found that the larger fractal dimension D or smaller characteristic scale coefficient G will weaken the interaction between micro-asperities. The smoother processing surfaces lead to higher contact stiffness in mechanical joint interfaces. The applicability and effectiveness of the proposed model are verified by comparing it with the traditional contact model calculation results. Under the same load, the interaction between micro-rough surfaces leads to an increase in both overall deformation and contact stiffness. The accuracy of the predicted contact stiffness model is also validated by comparing it with experimental results. [ABSTRACT FROM AUTHOR]

The strength of jointed rock is a fundamental factor in the slope stability of rock mass. This research investigates the effect of infill thickness on the strength of jointed rock specimens. Unlike previous studies involving artificial rock-like materials and saw-tooth surfaces, this work has been conducted on two natural types of sandstone with various rock surfaces. Natural low-plasticity clay of different thicknesses (1 mm to 3 mm) was used as the infill material. A series of shear box tests with a range of initial normal stresses from 0.5 MPa to 1.5 MPa were performed to obtain high-quality data regarding the shear strength of natural rock and to provide insights into the effect of infill and rock surface roughness on shear strength. The obtained results were also used to improve the current methods of rock strength predictions, which were initially designed to estimate the strength of artificial rock-like material. Based on the obtained laboratory data and the strength estimation using different methods, a newly proposed procedure was proved to provide more accurate estimations of the shear strength of jointed rock. [ABSTRACT FROM AUTHOR]

The strength of jointed rock is a fundamental factor in the slope stability of rock mass. This research investigates the effect of infill thickness on the strength of jointed rock specimens. Unlike previous studies involving artificial rock-like materials and saw-tooth surfaces, this work has been conducted on two natural types of sandstone with various rock surfaces. Natural low-plasticity clay of different thicknesses (1 mm to 3 mm) was used as the infill material. A series of shear box tests with a range of initial normal stresses from 0.5 MPa to 1.5 MPa were performed to obtain high-quality data regarding the shear strength of natural rock and to provide insights into the effect of infill and rock surface roughness on shear strength. The obtained results were also used to improve the current methods of rock strength predictions, which were initially designed to estimate the strength of artificial rock-like material. Based on the obtained laboratory data and the strength estimation using different methods, a newly proposed procedure was proved to provide more accurate estimations of the shear strength of jointed rock.

Abstract Plastoelastohydrodynamic lubrication of rough surfaces (R-PEHL) is a cutting-edge area of research in interface fluid-structure coupling analysis. The existing R-PEHL model calculates the elastic-plastic deformation of rough surface by the Love equation in a semi-infinite space smooth surface, which deviates from the actual surface. Therefore, it is an innovative work to study the exact solution of elastic-plastic deformation of rough surface and its influence on the solution results of R-PEHL model. In this paper, a new contact calculation model of plastoelastohydrodynamic lubrication (PEHL) with three-dimensional (3D) rough surface is proposed by integrating numerical method of EHL and finite element method. The new model eliminates an original error introduced by the assumption of semi-infinite space in contact calculation, providing wide applicability and high accuracy. Under the given rough surfaces and working conditions, the study reveals that: (1) the oil film pressure calculated by the new model is lower than that of the smooth surface in semi-infinite space by 200–800 MPa; (2) the Mises stress of the new model is 2.5%–26.6% higher than that of the smooth surface in semi-infinite space; (3) compared with the semi-infinite space assumption, the rough surface plastic deformation of the new model is increased by 71%–173%, and the local plastic deformation singularity may appear under the semi-infinite space assumption; (4) the plastic deformation caused by the first contact cycle on the rough surface of the new model accounts for 66.7%–92.9% of the total plastic deformation, and the plastic deformation of the semi-infinite space accounts for 50%–83.3%. This study resolves the contradiction between the smooth surface assumption and the rough surface in the existing R-PEHL model, establishing a solid logic foundation for the accurate solution of R-PEHL model.

Lithium mining has become a controversial issue in the transition to green technologies due to the intervention in natural basins that impact the native flora and fauna in these environments. Large resources of this element are concentrated in Andean salt flats in South America, where extraction is much easier than in other geological configurations. The Pozuelos highland salt flat, located in northern Argentina (Salta's Province), was chosen for this study due to the presence of different evaporitic crusts and its proven economic potential in lithium-rich brines. A comprehensive analysis of a 5.5-year-long time series of its microwave backscatter with Synthetic Aperture Radar (SAR) images yielded significant insights into the dynamics of their crusts. During a field campaign conducted near the acquisition of three SAR images (Sentinel-1, ALOS-2/PALSAR-2, and SAOCOM-1), field measurements were collected for computational modeling of the SAR response. The temporal backscattering coefficients for the crusts in the salt flat are directly linked to rainfall events, where changes in surface roughness, soil moisture, and water table depth represent the most critical variables. Field parameters were employed to model the backscattering response of the salt flat using the Small Slope Approximation (SSA) model. Salt concentration of the subsurface brine and the water table depth over the slightly to moderately roughed crusts were quantitatively derived from Bayesian inference of the ALOS-2/PALSAR-2 and SAOCOM-1 SAR backscattering coefficient data. The results demonstrated the potential for subsurface estimation with L-band dual-polarization images, constrained to crusts compatible with the feasibility range of the layered model. [ABSTRACT FROM AUTHOR]

In order to study the distribution of heat, temperature and stress fields and their mutual influence on the sliding process of the wheel-rail friction substrate, based on the G-W model, the wheel-rail friction substrate was simplified into a rough surface of micro-convex bodies with different shapes and an ideal plane, and combined with the finite element method. The results show these as follows. The interaction between the micro-convex bodies has an impact on the frictional heat generation, with the increase of the stack of spherical crown-shaped micro-convex bodies, the distribution area of the heat zone increases and the heat source decreases. The friction temperature rise decreases with the increase of the number of micro-bumps in the X -direction, and increases with the increase of the number of micro-bumps in the Z -direction, and the distribution of the heat zone is concentrated behind the sliding direction. The friction temperature rise on the rough surface of the spherical crown-shaped micro-convex body is generally higher than that of the rectangular-shaped micro-convex body. The effect of rough surface morphology on the heat source, heat zone distribution, temperature field and stress field distribution of wheel-rail friction is explored at the microscopic level to provide a theoretical basis for further research on wheel-rail interaction and ensure safe train operation. [ABSTRACT FROM AUTHOR]

This paper is concerned with the inverse scattering of the rough surfaces with multi-frequency phase and phaseless measurements. We present a high-order recursive iteration method based on the homotopy iteration technique to reconstruct the rough surfaces. The convergence for the multi-frequency homotopy iteration method is obtained under some conditions. Some numerical experiments show the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

This paper presents the application of hierarchical splines on the representation of models with extremely rough surfaces. The displacement between the smooth spline and the rough shape is stored as a set of images, where the displacement scalar is approximated using all three channels of the image (red, green, and blue). This type of surface representation allows easy and fast scientific analysis, interactive web display, and a significant reduction in the size of the extremely rough shapes. By using hierarchical splines over B-spline in combination with a compact displacement representation, we aim to achieve the same displacement quality of the whole surface, taking care that the model does not require much memory and is suitable for fast rendering. The focus of the study is on models from cultural heritage, without diminishing the importance of applying the approach to models from other areas. [ABSTRACT FROM AUTHOR]

In this paper, we propose an efficient phase field method for the simulation of wetting phenomena on rough surfaces. This method is based on the minimization of the free energy functional over an extended domain that includes the solid phase. The solid phase is fixed as a phase field function, and a new phase field model is derived including the solid phase as a penalization term, We note that this method does not impose the contact angle boundary condition but is determined implicitly by the surface tension coefficients in the bulk of the phase field model, which is especially suitable when the solid surface is rough. A gradient stable convex splitting scheme is developed for the new system. Numerical experiments of wetting on some complex geometries are performed to demonstrate the capacity and efficiency of the new method. [ABSTRACT FROM AUTHOR]

A tremendous number of landmines has been buried during the last decade. In recent years, various autonomous platforms equipped with ground-penetrating radars (GPRs) have been proposed for the detection of landmines. These systems have already demonstrated their performance in controlled environments with known ground truth. However, it has been observed that the influence of surface conditions in the form of vegetation and roughness as well as soil moisture content significantly reduce the detection probability. The influence of these individual factors on a ground-offset GPR is presented and discussed in this work. Each of these factors significantly degrades the backscattered signal. With increasing soil moisture, the signal gets attenuated more strongly; however, the signature is maintained in the phase of the C-Scans. An increase in surface roughness deteriorates the target pattern making it difficult to detect buried objects unambiguously. Vegetation, especially with irregular leaf structures, can appear as a ghost target and scatter the electromagnetic waves. In most cases, the target is easier to detect in the phase of the B- or C-Scan. [ABSTRACT FROM AUTHOR]

A numerical simulation of the Herschel–Bulkley laminar steady state shear flow around a stationary particle located on a sedimentation layer was carried out. The surface of the sedimentation layer was formed by hemispheres of the same radius as the particle. The drag force, lift force, and torque values were obtained in the following ranges: shear Reynolds numbers for a particle  R e S H = 2 – 200 , corresponding to laminar flow; power law index  n = 0.6 – 1.0 ; and Bingham number  B n = 0 – 10 . A significant difference in the forces and torque acting on a particle in shear flow in comparison to the case of a smooth wall is shown. It is shown that the drag coefficient is on average 6% higher compared to a smooth wall for a Newtonian fluid but decreases with the increase in non-Newtonian properties. At the edge values of  n = 0.6  and  B n = 10 , the drag is on average 25% lower compared to the smooth wall. For a Newtonian fluid, the lift coefficient is on average 30% higher compared to a smooth wall. It also decreases with the increase in non-Newtonian properties of the fluid, but at the edge values of  n = 0.6  and  B n = 10 , it is on average only 3% lower compared to the smooth wall. Approximation functions for the drag, lift force, and torque coefficient are constructed. A reduction in the drag force and lifting force leads to an increase in critical stresses (Shields number) on the wall on average by 10% for incipient motion (rolling) and by 12% for particle detachment from the sedimentation bed. [ABSTRACT FROM AUTHOR]

A novel electrical contact wear simulation method was proposed to characterize the electrical contact wear of fittings in ultra-high-voltage transmission lines by combining line fittings with the Archard wear model and oxidation loss theory. In this method, a three-dimensional (3D) rough body was generated by using the Weierstrass–Mandelbrot fractal function to simulate the contact surface. An electrical contact wear subroutine was developed, and the wear state was updated using arbitrary Lagrangian–Eulerian adaptive grid technology. Finally, finite element software was used to perform thermal stress wear coupled analysis. The results show that the wear volume, wear depth and friction temperature obtained by the rough electric contact model were 2.71 times, 4.21 times and 2.18 times of the common ideal plane model, respectively. In the rough model, the wear depth of the nodes initially accelerated, subsequently slowed down, and again accelerated with time. The friction high temperature region was distributed in a point pattern, and the temperature difference between the contact region and the non-contact region became obvious. [ABSTRACT FROM AUTHOR]

In this article, we use the analytical Kirchhoff solution (AKS) and numerical Kirchhoff approach to study the bistatic scattering field ($\gamma $) from mountain terrain at P-band frequency. The study area is Grand Mesa, Colorado, USA, and the properties of land surface roughness are extracted from airborne lidar surveys. The bistatic scattering coefficient $\gamma $ of variance fields, denoted by${\gamma }_v$, for several cases of radar resolutions over a 3.6 km by 3.6 km area are calculated at various scattering azimuth angles. Based on the lidar measurements, the land surface is decomposed into ${f}_2 + {f}_3$, where ${f}_3$ is 30 m of deterministic planar patches to approximate the coarse topography and ${f}_2$ is modeled by random rough surfaces with correlation functions. Surface roughness statistics derived from the Lidar data give a typical root mean square height of 0.07 m and a correlation length of 3.6 m for ${f}_2$. The mean values of slopes of ${f}_3$ are 1.3° and 0° with a standard deviation of 1° each, respectively in the x and y directions. Simulations using AKS show that the values of bistatic scattering coefficients for the variance of scattered fields can reach above 10 dB over a range of azimuth angles ${\phi }_s$ in the vicinity of the specular direction. Even in mountainous regions, the value of the ${\gamma }_v$ around the forward scattering direction is much larger than that for radar backscattering, and thus could support the use of a synthetic aperture radar concept based on signals of opportunity with data acquisition near the forward direction.

This study investigates terahertz (THz) wave scattering from a simulated lunar regolith surface, with a focus on the Brewster feature, backscattering, and bistatic scattering within the 325 to 500 GHz range. We employed a generalized power-law spectrum to characterize surface roughness and fabricated Gaussian correlated surfaces from Durable Resin V2 using 3D printing technology. The complex dielectric permittivity of these materials was determined through THz time-domain spectroscopy (THz-TDS). Our experimental setup comprised a vector network analyzer (VNA) equipped with dual waveguide frequency extenders for the WR-2.2 band, transmitter and receiver modules, polarizing components, and a scattering chamber. We systematically analyzed the effects of root-mean-square (RMS) height, correlation length, dielectric constant, frequency, polarization, and observation angle on THz scattering. The findings highlight the significant impact of surface roughness on the Brewster angle shift, backscattering, and bistatic scattering. These insights are crucial for refining theoretical models and developing algorithms to retrieve physical parameters for lunar and other celestial explorations.

This study evaluates the potential of erbium, chromium-doped:yttrium, scandium, gallium, and garnet (Er,Cr:YSGG) laser irradiation to modify the titanium surface for optimal seeding of fibroblasts and osteoblasts in the treatment of peri-implantitis. Titanium discs were treated using the Er,Cr:YSGG laser, an ultrasonic device with a stainless tip, or titanium scalers. Changes in surface properties were analyzed by profilometer and scanning electron microscopy (SEM). Murine fibroblast and osteoblast adhesion and proliferation were evaluated qualitatively and quantitatively at 24 and 72 h. Profilometric surface topography and SEM showed that titanium scalers and ultrasonic debridement techniques significantly changed the structure of the machined and rough titanium surfaces. The Er,Cr:YSGG laser irradiation, on the other hand, did not alter titanium microstructures. The Er,Cr:YSGG laser irradiation with the 40 Hz group showed a significantly higher attached fibroblast cell numbers than the titanium scaler group at 72 h after treatment (p = 0.023). Additionally, the number of the attached osteoblasts in the Er,Cr:YSGG laser irradiation with the 40 Hz group was significantly higher than that of the no-treatment groups 24 h after treatment (p = 0.045). The Er,Cr:YSGG laser effectively promoted adherence of fibroblasts and osteoblasts to the titanium surface without significantly altering the titanium surface, suggesting its superiority for treating peri-implantitis.

The onset of thermal instability with hybrid nanoparticles Al2O3–Cu in nanofluid is investigated with the combined effects of variable gravity, variable heat source and Lorentz force in a porous medium. Its applications are in many areas like chemical engineering, geophysics, astrophysics, etc. Based on literature, many gravity variations are assumed in the present analysis, along with a space-dependent heat source/sink parameter that varies along the width of the channel. The finite difference-based Lobatto IIIa method has been applied to solve the system under no nanoparticle flux and rough boundary conditions, and approximate analytical results are generated for some special cases. The roughness parameters ( λ 1 , λ 2 ), Darcy number (Da), gravity variation function (G (z)), and Chandrasekhar number (Q) delay the onset of convection and thus stabilize the system. It is also observed that an increase in the Lewis number Le, power index in variable heat source, and the nanoparticle Rayleigh concentration number Rn decreases the critical Rayleigh number R θ , c which destabilizes the system, and increases the critical wave number, which enlarges the convection cell size. In the case of exponential variation (1 − e z ) in the gravity variation parameter, the system becomes stabilized due to a delay in the onset of convection. In addition, we have considered multilayer perceptron-artificial neural network (MLP-ANN) computation to predict the critical Rayleigh number as per function of important controlling parameters. The data set of 625 observations is chosen keeping 70% for testing, 15% for training and 15% for validation using efficient Levenberg−Marquardt back propagation algorithm with optimal accuracy measures i.e., root mean square deviation (RMSE), root mean relative error (RMRE) and R 2 (coefficient of determination). Finally, the regression plots are drawn that correlate, target and output data. [ABSTRACT FROM AUTHOR]

Heat transfer by convection is widely used in many engineering applications such as in heat exchangers, combustion devices or gas processing. In Buildings, the use of rough surfaces allows enhancing heat transfer rates. Practically, in this study, a rough surface is obtained by using protuberances on the vertical left wall. In this perspective, the originality of this research is to study the influence of the protuberance geometric shapes on the heat transfer using 2D numerical simulations as a tool investigation. The homotopic transformation is used to reach a flat plate. The system of equations with the boundary conditions is solved using the finite volume method. A simple algorithm is chosen for the integration of algebraic equations. The governing equations are figured out using ANSYS FLUENT commercial software with SIMPLE algorithm in order to solve pressure-velocity coupling. The numerical simulations have been performed for different shapes of the protuberances (battlement, triangular and sinusoidal). The boundary conditions are based on a uniform heat flux applied to the vertical wall. On the other hand, the horizontal walls are subject to the adiabatic condition. It can be noticed that the effect of the wavy geometry induces a noticeable improvement of the heat transfer rate compared to an enclosure without protuberances. It can also conclude that the wavy configuration exhibits a Nusselt average slightly higher than that of the square cavity, particularly the triangular configuration, by approximately 20%. [ABSTRACT FROM AUTHOR]

This study proposes a novel anisotropic model based on fractal theory for three-dimensional (3D) rough surface reconstruction to improve the large error associated with isotropic models. The proposed model comprises a fractal-based two-dimensional (2D) contour curve, a conversion operator and a coefficient vector ratio. The effects of the virtual random curve and fractal-based 2D contour curve in the conversion operator are discussed. The largest height ratio of the virtual contour curve and the measured surface discrete point curve of each column are used in the coefficient vector ratio. The rough surface is also smoothed using a five-point cubic smoothing algorithm. Compared with the isotropic model, the proposed model resembles the measured surface more closely with an average fitting error reduction of 49.84% and 64.7% before and after smoothing, respectively. The surface exhibits horizontal and vertical textures that can be controlled by the fractal dimension and roughness in the X and Y directions. Additionally, an asperity contact model is established and analysed. The proposed modelling method for anisotropic 3D rough surface contact condition is more consistent with the measured surface model. The transverse and longitudinal textures of the anisotropic surface can be changed by the fractal dimension and fractal roughness in the X and Y directions. This research provides insights into characterising 3D rough surfaces of high-precision gears and improving nominal contact area accuracy. [ABSTRACT FROM AUTHOR]

Due to inherent nonlinear stiffness and damping characteristics, dry friction interfaces have a significant impact on the dynamics of jointed structures. When two surfaces are brought into purely normal contact, contact pressure distribution is of high concern. This work focused on the statistics of the contact pressure distribution between a rough surface and a smooth rigid plane, which provides new insight into the interface contact behaviour. First, the fractal rough surface is generated using the Weierstrass–Mandelbrot function with measured roughness parameters. With meshed rough surfaces, an elastic–plastic finite element contact analysis is performed to determine the contact pressure distribution. Then, the results of contact pressure are statistically analysed. The effects of roughness and contact load on contact area, contact stiffness and mean contact pressure are thoroughly investigated. The probability distribution of contact pressure is determined by fitting a continuous function using a twofold Weibull mixture model. The proposed probability distribution function is found to be capable of describing contact pressure. The contact pressure distribution is affected by the surface fractal characteristics and evolves with the contact load. [ABSTRACT FROM AUTHOR]

The small angular deflection of the spool under the action of non-equilibrium force is a main reason for valve seal failure. In the present study, a prediction model of the valve seal leakage was established considering the sectional shape and channel height of the leakage channel. The effect of spool deflection on the leakage rate was analyzed quantitatively from the results of three-dimensional finite element mechanical analysis. The microscale leakage channel of a contact deformation surface was then generated through the reconstruction of the rough surface with nanoscale precision, deterministic rough-peak contact analysis, and lattice leakage theory. The results showed that the spool deflection was the key factor affecting the leakage rate. The leakage rate was measured on a self-built experimental platform, and the experimental results verified the accuracy of the theoretical calculations. [ABSTRACT FROM AUTHOR]

Solar air heating thermal systems have found extensive utilization in a broad array of industrial and residential settings, playing a pivotal role in the conversion and reclamation of solar energy. Implementing repeated artificial roughness in the surfaces has the potential to augment thermal performance in solar air heaters (SAHs). This study presents a numerical investigation of SAHs with artificial rough surfaces, consisting of polygonal-shaped ribs and grooves located at different places inside the rectangular duct, that improve thermal efficiency. ANSYS Fluent software was employed to simulate the SAH with different relative pitch distances of p = 10mm and 20mm and relative rib heights e/d = 0.09-0.045. The working fluid air flows at different Reynolds numbers (Re), ranging from 3,800 to 18,000. Nusselt number (Nu), friction factor (f), and Thermal Hydraulic Performance (THP) are parameters to evaluate the performance of the SAH. The renormalized group (RNG) k-ϵ turbulent model was implemented in this simulation. The study outcomes indicate that increasing the rib height improves the heat transfer rate and nonetheless increases pressure drop while increasing the pitch distance. The higher Nusselt number (Nu) is 3.762 attained at p = 10mm and 3.420 at p = 20mm in the center-positioned rib at Re 3,800. The lower friction factor (f ) obtained in p = 20mm is 1.681 and 0.785 in p = 10mm in the staggered positioned rib at higher Re 15,000. The optimal THP was achieved at 2.813 at a staggered rib height at a pitch distance of p = 10mm at Re 8,000. The study's findings suggest that the incorporation of artificial rough surfaces has the potential to enhance the THP of an SAH. [ABSTRACT FROM AUTHOR]

This study proposes an improved semi-analytical approach for contact stiffness modeling of bolted joints in a machine tool system. First, nonlinear contact stress distribution within a single-bolted joint is obtained from the simulation results of finite element analysis software. Second, employing the Hertz contact theory and fractal theory, the contact stiffness model of a single asperity is formulated, affording analytical expressions for normal and tangential contact stiffnesses of a single-bolted joint by integrating multi-asperities in the contact area. Subsequently, considering two test specimens as illustrations, the mode shapes and natural frequencies of the proposed model and modal analysis tests are compared, and the influence of coupling effects between two adjacent bolts is illustrated. The maximum error in the natural frequencies of the proposed approach is < 2.73% relative to the experimental results. Finally, the measurements of frequency response functions on a box-in-box precision horizontal machine tool are conducted to demonstrate the accuracy and efficiency of the proposed model. The proposed model is highly efficient in revealing the influence of microcontact factors on the contact stiffness of bolted joints and in guiding the optimal functional design of bolt arrangements under the framework of virtual machine tools.Highlights: A nonlinear contact stress distribution in a single-bolted joint is proposed using a negative exponential function. A single-bolted joint's normal and tangential contact stiffnesses are derived considering the coupling effect. A modal experiment is conducted on two designed test specimens to demonstrate the accuracy of the proposed model. [ABSTRACT FROM AUTHOR]

Grinding is the most important method in machining, which belongs to the category of precision machining processes. Many mechanical bonding surfaces are grinding surfaces. Therefore, the contact mechanism of grinding a joint surface is of great significance for predicting the loading process and dynamic characteristics of precision mechanical products. In this paper, based on the collected grinding surface roughness data, the profile parameters and topography characteristics of the asperity were analyzed, the rough surface data were fitted, the asperity profile was reconstructed, and the parabola y = nx2 + mx + l of the cylindrical asperity model was established. After analyzing the rough surface data of the grinding process, the asperity distribution height was fitted with a Gaussian distribution function, which proved that asperity follows the Gaussian distribution law. The validity of this model was confirmed by the non-dimensional processing of the assumed model and the fitting of six plasticity indices. When the pressure is the same, the normal stiffness increases with the decrease in the roughness value of the joint surface. The experimental stiffness values are basically consistent with the fitting stiffness values of the newly established model, which verifies the reliability and effectiveness of the new model established for the grinding surface. In this paper, a new model for grinding joint surface is established, and an experimental platform is set up to verify the validity of the model. [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) gas therapy demonstrates great potential to induce cancer cell apoptosis and antitumor immune responses, which exhibits tremendous potential in cancer treatment. However, the therapeutic efficacy of CO therapy is inhibited by the immunosuppressive tumor microenvironment (TME). Herein, a facile strategy is proposed to construct hollow‐structured rough nanoplatforms to boost antitumor immunity and simultaneously reverse immunosuppression by exploring intrinsic immunomodulatory properties and morphological optimization of nanomaterials. The TME‐responsive delivery nanosystems (M‐RMH) are developed by encapsulating the CO prodrug within hollow rough MnO2 nanoparticles and the subsequent surface functionalization with hyaluronic acid (HA). Rough surfaces are designed to facilitate the intrinsic properties of HA‐functionalized MnO2 nanoparticles (RMH) to induce dendritic cell maturation and M1 macrophage polarization by STING pathway activation and hypoxia alleviation through enhanced cellular uptake. After TME‐responsive degradation of RMH, controlled release of CO is triggered at the tumor site for CO therapy to activate antitumor immunity. More importantly, RMH could modulate immunosuppressive TME by hypoxia alleviation. After the combination with aPD‐L1‐mediated checkpoint blockade therapy, robust antitumor immune responses are found to inhibit both primary and distant tumors. This work provides a facile strategy to construct superior delivery nanosystems for enhanced CO/immunotherapy through efficient activation of antitumor immune responses and reversal of immunosuppression. [ABSTRACT FROM AUTHOR]

Mineral surface roughness is an important factor affecting flotation efficiency. Surface roughness can affect the hydrophobicity of minerals, the adsorption of reagents, and the rupture of liquid films between particles and bubbles, resulting in a significant impact on the interaction process between particles and bubbles. However, there is currently a lack of systematic review work on the influence of roughness on particle-bubble interaction process. Therefore, the authors firstly reviewed the surface roughening modification techniques and roughness testing methods. Secondly, the influence of roughness on the particle-bubble interaction process was systematically discussed from four aspects: flotation kinetics, contact angle, formation time of triple-phase contact line, and interaction force between particles and bubbles. The concept of roughness scale was proposed for its importance in the research of particle-bubble interactions. Thirdly, based on the coupling mechanism between roughness scale and mineral surface hydrophobicity in the particle-bubble interaction process, the importance of mineral surface wetting state in the interaction process between rough surfaces and bubbles was emphasized. The reasons for the inconsistent research conclusions on the impact of roughness on contact angle and flotation performance were also analyzed and discussed. Finally, the conclusions were drawn through critical analysis and literature review, and the prospects for future research directions were outlined. This paper contributes to a better understanding of the influence of mineral surface roughness on the flotation process, and can provide a theoretical support for regulating mineral surface roughness to create favorable flotation conditions and improve the flotation efficiency and selectivity.

Mechanical joint interfaces are widely found in mechanical equipment, and their contact stiffness directly affects the overall performance of the mechanical system. Based on the fractal and elastoplastic contact mechanics theories, the K-E elastoplastic contact model is introduced to establish the contact stiffness model for mechanical joint interfaces. This model considers the interaction effects between micro-asperities in the fully deformed state, including elasticity, first elastoplasticity, second elastoplasticity, and complete plastic deformation state. Based on this model, the effects of fractal parameters on normal contact stiffness and contact load are analyzed. It can be found that the larger fractal dimension D or smaller characteristic scale coefficient G will weaken the interaction between micro-asperities. The smoother processing surfaces lead to higher contact stiffness in mechanical joint interfaces. The applicability and effectiveness of the proposed model are verified by comparing it with the traditional contact model calculation results. Under the same load, the interaction between micro-rough surfaces leads to an increase in both overall deformation and contact stiffness. The accuracy of the predicted contact stiffness model is also validated by comparing it with experimental results.

Abstract Carbon monoxide (CO) gas therapy demonstrates great potential to induce cancer cell apoptosis and antitumor immune responses, which exhibits tremendous potential in cancer treatment. However, the therapeutic efficacy of CO therapy is inhibited by the immunosuppressive tumor microenvironment (TME). Herein, a facile strategy is proposed to construct hollow‐structured rough nanoplatforms to boost antitumor immunity and simultaneously reverse immunosuppression by exploring intrinsic immunomodulatory properties and morphological optimization of nanomaterials. The TME‐responsive delivery nanosystems (M‐RMH) are developed by encapsulating the CO prodrug within hollow rough MnO2 nanoparticles and the subsequent surface functionalization with hyaluronic acid (HA). Rough surfaces are designed to facilitate the intrinsic properties of HA‐functionalized MnO2 nanoparticles (RMH) to induce dendritic cell maturation and M1 macrophage polarization by STING pathway activation and hypoxia alleviation through enhanced cellular uptake. After TME‐responsive degradation of RMH, controlled release of CO is triggered at the tumor site for CO therapy to activate antitumor immunity. More importantly, RMH could modulate immunosuppressive TME by hypoxia alleviation. After the combination with aPD‐L1‐mediated checkpoint blockade therapy, robust antitumor immune responses are found to inhibit both primary and distant tumors. This work provides a facile strategy to construct superior delivery nanosystems for enhanced CO/immunotherapy through efficient activation of antitumor immune responses and reversal of immunosuppression.

Abstract The significance of freely oscillating unsteady stagnation flows is attributed to their use in various kinds of engineering processes like cooling systems, heat exchangers and turbomachinery. The restrictive forces produced with the help of magnetic fields are a useful technique in providing optimum flow control in the metallurgical operations and refinement of molten metals. The present study highlights the inclined magnetic field implications on an oscillatory streaming nanofluid which impinges non-orthogonally over a non-smooth surface. The surface roughness of the wall is elaborated by the slip velocity condition. The two-phase Buongiorno nanofluid model is being considered. The energy dissipation due to the active chemical reactions occurring in the flow is adopted with Arrhenius activation energy. Suitable dimension-free variables are chosen to make the mathematical model parameter dependent. The numerical outcomes of the problem are determined through the utilization of the bvp5c solver based on the finite difference method using MATLAB R2023a. The graphical representations depict significant alteration in concentration profiles with thermal ratio ( δ ) and Activation energy ( E * ). The findings indicate that higher activation energy and weaker temperature conditions increased the mass transfer. In conjunction, the velocity profile is enhanced for acute magnetic field angles. [ABSTRACT FROM AUTHOR]

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With the increasing demand for energy, heat and mass transfer through porous media has been widely studied. To achieve accuracy in studying the behavior of heat transfer, a good knowledge of the effective thermal conductivity (ETC) of porous materials is needed. Because pore structure dominates the ETC of porous materials and effective stress leads to a change in pore structure, effective stress is one of the key influencing factors affecting ETC. In this study, considering the structure of surface roughness and pore size, based on fractal theory, a novel analytical solution at the pore scale for ETC of porous materials under stress conditions is proposed. Furthermore, in this model, capillaries in porous materials saturated with multiple phases have sinusoidal periodically constricted boundaries. The derived ETC model is validated against available experimental data. Moreover, the influences of the effective stress, initial effective porosity, roughness structure characterization, and wetting phase saturation on the ETC are analyzed. Compared with previous models, the rough surfaces of porous materials and the coupling of heat conduction and mechanics are taken into consideration to make the model more reasonable. As a result, this ETC model can better reveal the mechanism of heat conduction in porous media under stress conditions. [ABSTRACT FROM AUTHOR]

The C/SiC composite is a promising material for ablation-resistant thermal protection in near-space hypersonic environments. The formation of an SiO2 oxide layer through passive oxidation on the surface of the composite is a significant factor influencing its performance. It is essential to accurately predict the thickness of the SiO2 oxide layer and the recession and mass loss of the C/SiC composite during passive oxidation. The SiO2 oxide layer is a typical porous media exhibiting self-similarity and thus fractal theory can be applied to establish the relation between the oxygen flow rate and microstructural parameters of the oxide layer. The Weierstrass–Mandelbrot (WM) function is employed to simulate the rough interfaces between the SiO2 oxide layer and the C/SiC composite to evaluate the influence of the fractal dimensions of the oxide layer on the performance of thermal protection of the C/SiC composite. The results show that the C/SiC composite exhibits improved thermal protection performance when accompanied by a lower tortuosity fractal dimension and a higher pore area fractal dimension of the oxide layer. Conversely, the composite demonstrates enhanced ablation resistance with a higher tortuosity fractal dimension and a lower pore area fractal dimension of the oxide layer. The predictions of the calculation model show good agreement with the experimental data and demonstrate the critical influence of microstructural parameters of the oxide layer on passive oxidation of the composite, providing practical implications for designing materials with desired thermal protection or ablation resistance properties. [ABSTRACT FROM AUTHOR]

In this paper, the first order perturbation theory (PT) and the small slope approximation (SSA) are employed to analyze the scattering behavior of a two dimensional dielectric-topological insulator (TI) rough interface with Gaussian distribution. Zeroth and first order scattering amplitudes are utilized to obtain the analytic expressions for the coherent and incoherent intensities, respectively. For vertical incidence, an equation can be found whose numerical solution gives the Brewster angle at which the co polarized coherent intensity becomes zero. The scattering scenarios are analyzed where both polarization states of the incident field exhibit total depolarization and the co polarized incoherent scattering is zero.