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Reasonable laser process parameters and heating paths are crucial in laser forming (LF) technology. Obtaining the proper laser processing parameters and the heating path is the decisive factor to determine the forming efficiency and precision of the complex 3D surfaces with double curvature. First, the 3D target surfaces with double curvature were developed in this paper to flat plates through the finite element numerical simulation tool, and the magnitude and direction of in-plane and bending strains were obtained; the direction perpendicular to the principal strain is the direction of the heating paths. Second, the database of laser process parameters and principal strains was established to determine the proper laser process parameters. Finally, combined with the above laser parameters and heating paths, the “pillow” and “spherical” surfaces were obtained, and the accuracy of this method was verified by experiments.

Hypothesis Droplet wetting on a solid substrate is affected by the surface heterogeneity. Introducing patterned wettability on the solid substrate is expected to engender anisotropic wetting morphologies, thereby manipulating droplet wetting behaviors. However, when the droplet size is comparable with that of the surface heterogeneity, the wetting morphologies cannot be depicted by the quintessential Cassie’s theory but should be possible to be predicted from the perspective of thermodynamics via surface energy minimization. Methods Here, we investigate the equilibrium droplet shapes on chemically patterned substrates by using an analytical model, phase-field simulations, and experiments. The former two methods are sharp and diffuse interface treatments, respectively, which both are based on minimizing the free energy of the system. The experimental results are obtained by depositing droplets on chemically patterned glass substrates. Findings Various anisotropic wetting shapes are found from the three methods. Excellent agreement is observed between different methods, showing the possibility to quantify the anisotropic wetting droplet morphologies on patterned substrates by present methods. We also address a series of non-rotationally symmetric droplet shapes, which is the first resport about these special wetting morphologies. Furthermore, we reveal the anisotropic wetting shapes in a quasi-equilibrium evaporation process.

This paper is concerned with the disturbance estimation and velocity recovery of autonomous surface ve hicles subject to unknown input gains, in addition to lumped uncertainties composed of unknown internal dynamics and external disturbances. Existing extended state observer design methods are not applicable due to the fact that some prior knowledge on model parameters such as the control input gains are assumed to be known in advance. By incorporating a concurrent learning approach into the extended state observer design, a three-order data-driven adaptive extended state observer based on position and acceleration information is proposed to estimate the unknown input gains, lumped disturbance, and unmeasured velocities. An advantage of the proposed data-driven adaptive extended state observer is that the unknown input gains, lumped disturbance, and unknown velocities can be simultaneously estimated with guaranteed convergence thanks to concurrent learning. The result is extended to a data-driven adaptive extended state observer with finite-time convergence. The efficacy of the proposed two data-driven adaptive extended state observers for autonomous surface vehicles is substantiated via simulations.

The interfacial tension gradient originating from a temperature gradient causes particle migration. Previously, the authors reported the manipulation of a metal sphere in a glass using a near-infrared (NIR) laser. The NIR laser beam was not absorbed by the glass but by the metal sphere, causing the metal sphere to heat up. The local softening of the surrounding glass enabled metal sphere migration. The driving force was explained in terms of an interfacial gradient induced by the temperature distribution. In this study, metal sphere migration driven by surface heating was investigated. A metal sphere located near a surface migrated toward the surface owing to surface heating using a CO2 laser and finally exited the glass. This phenomenon was observed using a charge-coupled device camera. A numerical calculation showed that the temperature at the metal sphere was 2760 K, and the temperature difference between the illuminated and non-illuminated metal sphere surfaces was 70 K. The driving force was calculated as 73 nN. The results confirmed that the glass surface heating caused the temperature distribution and the metal sphere migration.

Information regarding the depth distribution in a specific aquatic area is not also crucial for the safety of navigation, but also for modelling environmental processes, such as the quick establishment of marine-land boundaries or assessments of flood risk areas. Using elevation data from different available sources can be very convenient for individuals who wish to conduct quick analysis or need to obtain data covering a large area without the need for data collection and surveys. This study proposes a method of combining spatial data from different sources during surface modelling of a coastal area. The spatial data used for elevation surface modelling included hydrographic and topographic data, which are often collected separately for various purposes. Data are saved in different formats with various resolutions and accuracies; thus, a uniform surface model that will allow for easy and accurate analysis is currently lacking. The main aim of this study was to create a model of the surface of a coastal area using input data from various sources with the highest possible accuracy. This paper presents the available spatial data sources for coastal areas, along with the data pre-processing process. Furthermore, spatial data fusion is introduced, along with the results. The entire process of creating the uniform surface model consisted of several steps that are described in detail and visualised. The obtained model was visualised using a three-dimensional map.

This letter describes the new ability to measure wind-generated gravity waves using the airborne Ka-band interferometric altimeter (AirKaIA). Although the original definition of wave parameters is derived from wave-induced sea surface elevation (WSSE), it is difficult to directly measure the WSSE, so most remote sensing of waves use other types of signals to obtain wave parameters. Here, we present the measurement of 2-D WSSE from AirKaIA. A new wave retrieval method based on the 2-D WSSE has been developed, tested with simulation data, and applied to AirKaIA data. The results indicate that the retrieved dominant wave directions, dominant wavelengths, and significant wave heights from AirKaIA are in agreement with in situ measurements while highlighting the need for further method tests using more observations. The study of ocean signals from interferometric altimeter is an emerging research topic. AirKaIA's measurements of wind-generated gravity waves with 2-D WSSE have implications for the assessment of future interferometric altimeter missions.

The interaction of proteins and peptides with inorganic surfaces is relevant in a wide array of technological applications. A rational approach to design peptides for specific surfaces would build on amino-acid and surface specific interaction models, which are difficult to characterize experimentally or by modeling. Even with such a model at hand, the large number of possible sequences and the large conformation space of peptides make comparative simulations challenging. Here we present a computational protocol, the effective implicit surface model (EISM), for efficient in silico evaluation of the binding affinity trends of peptides on parameterized surface, with a specific application to the widely studied gold surface. In EISM the peptide surface interactions are modeled with an amino-acid and surface specific implicit solvent model, which permits rapid exploration of the peptide conformational degrees of freedom. We demonstrate the parametrization of the model and compare the results with all-atom simulations and experimental results for specific peptides.

It is critical for maintaining the safe operation of turbine blades to inspect the potential structural damages promptly. However, the industry still lacks efficient tools for inspection of the curved surface. In this respect, in this article, a new flexible probe with in-plane differential coils is proposed. With the sophisticated configuration, the probe has four channels, which complement each other in terms of sensitivity to defects of different orientations. The in-plane differential scheme nulls the background signal and reduces the noise resulting in high sensitivity to microdefects. The probe can be bent according to the curved surface due to its flexible configuration. A three-dimensional finite-element method model based on the cluster parallel computation is utilized to study the feasibility and performance of the probe, and a prototype probe is developed and tested by scanning defects on the curved surface of a turbine blade sample. Furthermore, a data fusion method is proposed to obtain a better signal-to-noise ratio so that defects with length*width*depth = 2.5 mm*0.1 mm*0.1 mm can be identified. Based on repeated experiments, it is observed that the probability of detection with the fusion of the multichannels is higher than that of every single channel demonstrating that the data fusion increases the reliability of the inspection.

We consider hyperbolic links that admit alternating projections on surfaces in compact, irreducible 3-manifolds. We show that, under some mild hypotheses, the volume of the complement of such a link is bounded below in terms of a Kauffman bracket function defined on link diagrams on the surface. In the case that the 3-manifold is a thickened surface, this Kauffman bracket function leads to a Jones-type polynomial that is an isotopy invariant of links. We show that coefficients of this polynomial provide 2-sided linear bounds on the volume of hyperbolic alternating links in the thickened surface. As a corollary of the proof of this result, we deduce that the twist number of a reduced, twist reduced, checkerboard alternating link projection with disk regions, is an invariant of the link., 24 pages, 6 figures; To be published in Fundamenta Mathematicae; V2: Corrected typos, updated references

The lift generation in a wing of primary importance to the flying vehicle the airfoil geometry plays a vital role in the magnitude of lift and drag forces. The enhancement of lift can be achieved using different active and passive techniques. Effect of fluid material interaction plays a major role in the boundary layer separation. The active control using the roller belt mechanism is investigated using NACA 662-015 airfoil wing configuration. The moving belt surface fixed to the top surface of the wing is used designed to operate in the various free stream velocities of 5, 10, and 15 m/s. The variation of lift characteristics for different angles of attack has experimented with the increase in belt speed, it is observed that the 10% increase in the effective lift in comparison with wing configuration without moving surface.

The complex terrain in mountainous areas distorts solar illumination, which brings a strong topographic effect on optical remote-sensing observations. Although many efforts have been done to correct this effect via normalizing solar illumination induced differences, there are still high uncertainty, especially for poor illuminated surfaces. In this study, a downwelling shortwave radiation (DSR)-based correction (DSRC) method was proposed. The topographic effects were accounted by normalizing DSR differences at different topographic conditions, and a stratified correction strategy was applied by separating the image into different groups according to normalized difference vegetation index (NDVI) to consider the spectral differences of different land-cover types. The DSRC method was applied to nine Landsat 8 scenes with high-resolution DSR data acquired by downscaling the Meteosat Second Generation (MSG) DSR product. The performance analysis indicates that the correlation coefficient between the corrected surface reflectance and illumination conditions notably decreased. Compared with SCS+ C, empirical rotation, Statistical-Empirical, and Modified Minnaert methods, the DSRC method well retains inherent spectral pattern and provides good advantages in normalizing the aspect differences of surface reflectance. Furthermore, the comparison of NDVI values before and after correction indicated that DSRC preserved the original values and successfully corrected the overestimated NDVI values of poor illuminated surfaces. The corrected NDVI time series provide more reasonable cycle of the phenology of vegetated surfaces than the original series. In summary, the DSRC method has a strong potential for reducing topographic effects that currently limit the applications of remotely sensed data in mountainous areas.

The responses of surface wind stress to the mesoscale sea surface temperature (SST) anomalies associated with the SST front in the northern South China Sea (NSCS) are studied using satellite observations and reanalysis data. Both satellite and reanalysis data explicitly show the linear relationships between the spatial-high-pass filtered wind stress perturbation derivatives and the underlying SST gradient field. However, the noise in the linear relationships is much smaller in the reanalysis data than in the satellite observations. This result is rarely reported in other frontal areas. The wavelet analysis shows that the satellite scatterometer observed numerous high wavenumber perturbations within 100 km in the NSCS, but these perturbations were absent in the reanalysis data. The linear relationship between the perturbation SST gradient and derivative wind stress fields is not significant at this scale, which enhances the noise in the linear relationship. The spatial bandpass-filtered perturbation between 100 and 300 km can give reasonable estimates of the coupling coefficients between the wind stress divergence and downwind SST gradient (αd) and between the wind stress curl and crosswind SST gradient (αc) in the NSCS, with values of 1.33 × 10−2 and 0.95 × 10−2 N m−2 °C−1, respectively.

This paper summarizes the submissions to a recently announced contact-mechanics modeling challenge. The task was to solve a typical, albeit mathematically fully defined problem on the adhesion between nominally flat surfaces. The surface topography of the rough, rigid substrate, the elastic properties of the indenter, as well as the short-range adhesion between indenter and substrate, were specified so that diverse quantities of interest, e.g., the distribution of interfacial stresses at a given load or the mean gap as a function of load, could be computed and compared to a reference solution. Many different solution strategies were pursued, ranging from traditional asperity-based models via Persson theory and brute-force computational approaches, to real-laboratory experiments and all-atom molecular dynamics simulations of a model, in which the original assignment was scaled down to the atomistic scale. While each submission contained satisfying answers for at least a subset of the posed questions, efficiency, versatility, and accuracy differed between methods, the more precise methods being, in general, computationally more complex. The aim of this paper is to provide both theorists and experimentalists with benchmarks to decide which method is the most appropriate for a particular application and to gauge the errors associated with each one.

The “Contact Mechanics Challenge” posed to the tribology community by Muser and Dapp in 2015 detailed a 100 µm × 100 µm randomly rough surface with a root-mean-square gradient of unity, $${\bar{\text{g}}} = 1$$ . Many surfaces, both natural and synthetic, can be described as randomly rough, but rarely with a root-mean-square gradient as steep as $${\bar{\text{g}}} = 1$$ . The selection of such a challenging surface parameter was intentional, but potentially limiting for broad comparisons across existing models and theories which may be limited by small-slope approximations. In this manuscript, the root-mean-square gradients ( $${\bar{\text{g}}}$$ ) of the “Contact Mechanics Challenge” surface were produced on 1000 × scaled models such that there were three different surfaces for study with $${\bar{\text{g}}} = \, 0.2, \, 0.5$$ , and 1. In situ measurements of the real area of contact and contact area distributions were performed using frustrated total internal reflectance along with surface deformation measurements performed using digital image correlation. These optical in situ experiments used the scaled 3D-printed rough surfaces that were loaded into contact with smooth, flat, and elastic samples that were made from unfilled PDMS: (10:1) E* = 2.1 MPa Δγ = 4 mJ/m2; (20:1) E* = 0.75 MPa Δγ = 3 mJ/m2; (30:1) E* = 0.24 MPa Δγ = 2 mJ/m2. All of the loading was performed using a uniaxial load frame under force control. A Green’s function molecular dynamics simulation assuming the small-slope approximation was compared to all experimental data. These measurements reveal that decreasing root-mean-square gradient noticeably increases real area of contact area under conditions of “equal” applied load, but variations in the root-mean-square gradient did not significantly alter the contact patch geometry under conditions of nearly equal real area of contact. Including $${\bar{\text{g}}}$$ in the reduced pressure ( $$p = P /(E*{\bar{\text{g}}})$$ ) reduced the root-mean-square error between the simulation ( $${\bar{\text{g}}} = 1$$ ) and all experimental data for the relative area of contact as a function of reduced pressure over the entire range of surfaces, materials, and loads tested.

This is an update of the article: ‘Surfaces and Interfaces, Electronic Structure of’ published in 2005 by Elsevier. In the last 10 years several new subjects have appeared. Among them (1) Topological Insulators and (2) Interfaces between solid–liquid structures are strictly related to the above-mentioned article. The first one discusses how insulators or semiconductors subjected to a shearing deformation that maintains the local topology become electrical conductors. In the second case, the interface between solids and electrolytic solutions shows, by appropriate application of voltages, surface structures similar to those observed in free surfaces obtained in ultra-high vacuum.

We study timelike surface, curve pairs by using their curvature properties. We assume that timelike surfaces whose one of the principal curvatures is identically constant, have diagonalizable shape operators in $${\mathbb {E}}_{1}^{3}$$ . Then we give some results about timelike surfaces on which inclined curves lie as geodesic curves.

The structure and energy characteristics of structures formed during arginine adsorption on silica surface from aqueous solution were studied by the density functional theory (B3LYP) method using a valence-split basis set 6-31++G(d,p) within the continuous solvent model (PCM) and supermolecular approximation. The equilibrium structural and energy parameters of the protonated arginine molecule in the gas phase dependent on the location of the hydrogen atom are considered including those of two possible zwitterions. The structure of the arginine ion Н2А+, which is formed when a proton attaches to a molecule or zwitterion of a given amino acid, has been elucidated. To determine the deprotonation constant of the carboxyl group in an acidic medium, the complexes of the arginine molecule (AH32+) in the state with undissociated and deprotonated carboxyl groups are considered. The simulation of the acid medium was performed by taking into account the interaction with two hydrated HCl ion pairs, which provided the protonation of the a-amino group and the nitrogen atom of amino group within the guanidine group. In the study on the interaction of an arginine molecule with silica surface in an aqueous medium, complexes containing a Si8O12(OH)7O– ion with a deprotonated silanol group, six water molecules, and an arginine molecule with a deprotonated carboxyl group were considered. It has been found that the arginine molecule is most likely to be adsorbed on slica surface with formation of hydrogen bonds between the hydrogen atoms of the a-amino group and the oxygen atom of the deprotonated silanol group. In this case, the formation of a hydrogen bond between the oxygen atom of the carboxyl group and the hydrogen atom of the neighboring silanol group is possible. Slightly less likely is adsorption of arginine molecules due to interaction of the guanidine group with silanol groups of the surface. According to the calculated data, the adsorption of the zwitterionic form of the arginine molecule from the aqueous solution is equally likely to occur due to interaction of silanol groups of silica surface with both the carboxyl group and the guanidine group.

The paper presents the results of analysis of electrical measurements performed in the space experiment "Impulse (stage 1)" on the Service module of the ISS RS. This experiment investigated the effects of the interaction of the charged component of the ionosphere to the surface of large KA, which is the ISS. This paper analyses the measurement of quasi-stationary electric field and current leakage, was, respectively, sensors of the vibration type and flat probes from the Complex control electrophysical parameters (CCEP), developed by SPJ MT. To study the dependence of measurements from the ionosphere flow direction to the surface of the ISS RS was installed two sets of sensors with the direction of the angle of "visibility" in the Nadir (towards the Earth) and to "satellite footprint " (against the velocity vector of the ISS). Carried out analysis of common regularities measurements depending on the sun-shadow environment on orbit ISS motions and depending on current geophysical dynamics of the ionosphere. Massive the measurements including more than 170 telemetric sessions were analyzed. More than 11000 hours of measurements current of leakage (or runoff current) and measurements of quasi-stationary electric field with discretization 1s and UT binding to each point were analysed. The data measurements, geophysical and orbital data were collected in an electronic album. It is shown that experimental data correlate with the crossing time of the ISS boundaries known geophysical structures: the noon Meridian, the Main ionospheric failure (MIF), the boundaries diffuse intrusion (BDI), the Equatorial Geomagnetic anomaly (EA). In this regard, despite the specificity of the ISS (the spacecraft super big sizes, the most complex spatial configuration) similar measurements, nevertheless, are quite suitable for monitoring researches of some features of an ionosphere at the level of F2 layer with a temporary scale from 1s and can be used for more detailed study of the geophysical structures and related effects in the ionosphere. In addition, the results obtained can be used for the analysis of disturbances of electromagnetic conditions near the surface of the ISS RS, for monitoring potential and currents of leakage on the surface of the ISS. Keywords: electrophysical measurements, sensors of the vibration type, flat probes, electric field, current leakage, geophysical structure, ionosphere

Following the continuous deterioration of flexible road pavements on Federal Highways in Northern Nigeria, which in some quarters is attributed to poor structural capacity of the subgrade soil or design and workmanship; this study examined the relationship between the instantaneous surface condition of flexible road pavement and the California Bearing Ratio (CBR) values of the corresponding subgrade soils. An investigation of road surface condition was carried out on 60 km length of the Zaria – Kaduna Federal Highway in Northern Nigeria. Experimental results on the mechanical properties of the corresponding subgrade soils of road segments measured at Chainages were obtained from the Nigeria Federal Ministry of Power, Works and Housing (FMPWH). The primary data used by the study were measured as quantities of surface area distresses along the site which included; cracks, potholes, rutting and edge failure, while secondary data from the FMPWH database included; natural moisture content, maximum dry density, specific gravity, liquid limit, plastic limit, liquidity index, optimum moisture content, California Bearing Ratio (CBR), percent of soil particles passing #200 sieve and AASHTO classification of the subgrade soil. A Pearson correlation analysis between the road pavement surface condition and the CBR value of the subgrade soil at 95% Confidence Level using a 1-tailed statistics for the test hypothesis revealed that, there was no dependency between the pavement surface condition and the corresponding CBR property of the subgrade soil.

First-arrival traveltime tomography has been widely used for upper crustal velocity modeling, but it usually suffers from the problem of complex surface topography. To overcome this problem, we have developed a new topography-dependent eikonal tomography scheme that combines a developed accurate and efficient traveltime modeling method and introduces a flexible and robust adjoint inversion scheme in the presence of irregular topography. A surface-flattening scheme is used to handle the irregular surface, where the real model is discretized by curvilinear grids and the irregular free surface is mathematically flattened through the transformation from Cartesian to curvilinear coordinates. Based on this parameterization, the forward traveltime modeling is conducted by a monotone fast-sweeping method that discretizes the factored topography-dependent eikonal equation with a point-source condition. This algorithm can circumvent the source-singularity problem and decrease the numerical error in the vicinity of a point source in the curvilinear system. Then, the gradient-based inversion is used to minimize the misfit function, which is achieved by a matrix-free adjoint-state method without cumbersome ray tracing and explicit estimation of the Fréchet derivative matrix in the curvilinear coordinate system. The new tomographic scheme is evaluated through numerical examples with different seismic structures with complex topography, and then applied to a wide-angle profile acquired in the northeastern Tibetan Plateau. The results validate the effectiveness and efficiency of our tomography scheme in constructing shallow crustal velocity models with irregular topography.

With the development of modern industry, rotary lip seal is applied to more complex working conditions. For the lip seal with larger or smaller radial force, and the lip seal with incomplete motion...

International audience; We describe an algorithm that can robustly decide whether a grip or a footstep is secure given data collected from at least two independent sensors. This algorithm is based on the observation that if there is an absence of slip, then, owing to the high velocity of mechanical waves in solids, the two sensor signals must be highly correlated, even in the presence of internal or external perturbations. The statistical distance between signals collected during slip and non-slip phases, regarded as random distributions, also provides a continuous measure of graspability or walkability of an object being held or a ground being stepped on. We tested the algorithm on a bench using micro-electro-mechanical system (MEMS) accelerometers and with a variety of materials of different surface roughnesses. We also discuss the applications of this non-slip/slip discrimination algorithm and its putative relationship with human gripping behavior.

In this paper, we handle focal surfaces of surface of revolution in Galilean 3-space $\mathbb{G}_{3}$. We define the focal surfaces of surface of revolution and we obtain some results for these types of surfaces to become flat and minimal. Also, by giving some examples to these surfaces, we present the visualizations of each type of focal surface of surface of revolution in $\mathbb{G}_{3}$.

Nanopatterning methods for pattern formation of high-resolution nanostructures are essential for the fabrication of various electronic devices, including wearable displays, high-performance semiconductor devices, and smart biosensor systems. Among advanced nanopatterning methods, nanotransfer printing (nTP) has attracted considerable attention due to its process simplicity, low cost, and great pattern resolution. However, to diversify the pattern geometries for wide device applications, more effective and useful nTP based patterning methods must be developed. Here, we introduce a facile and practical nanofabrication method to obtain various three-dimensional (3D) ultra-thin metallic films via thermally assisted nTP (T-nTP). We show how to generate surface-wrinkled 3D nanostructures, such as angular line, concave-valley, and convex-hill structures. We also demonstrate the principle for effectively forming 3D nanosheets by T-nTP, using Si master molds with a low aspect ratio (A/R ≤ 1). In addition, we explain how to obtain a 3D wavy structure when using a mold with high A/R (≥ 3), based on the isotropic deposition process. We also produced a highly ordered 3D Au nanosheet on flexible PET over a large area (> 15 µm). We expect that this T-nTP approach using various Si mold shapes will be applied for the useful fabrication of various metal/oxide nanostructured devices with high surface area.

Surface chemical reactions on atomically precise metal clusters have considerable attention for opening a new platform for cluster functionalization. In this study, basic Au25(4-PyET)18 (4-PyET = -SCH2CH2Py; Py = pyridyl) clusters were successfully transformed into cationized Au25(4-PyET-CH3+)x(4-PyET)18-x clusters, without altering their Au25 cores, through the Menshutkin SN2 reaction of their surface Py moieties. This study offers not only a simple cationization method but also a protocol for modifying the surface functionalities of molecular metal clusters via a synthetic reaction.

In this paper, a novel rigid-flexible coupled ultra-high elastic screen surface was proposed. Then vibration test was conducted to investigate kinematic characteristics of the screen surface. Moreover, a high-speed camera device was utilized to study deformations of the screen surface and the mechanism of strengthening looseness and overcoming plugging. Furthermore, the screening performance of screen surface was investigated. The obtained results show that the maximum acceleration and the displacement of the proposed screen surface can be as high as 27 g and 21.37 mm, which are 8.82 times and 7.32 times of the side plate area, respectively. Accordingly, the screen surface can produce strong impact on the sticky and moist materials, so as to make materials loosen and overcome the plugging problem of the screen surface. After optimizing the parameters, the screening efficiency can reach the maximum value of 85.41% and the content of the total misplaced material is 7.07%.

This paper proposes a new robust Discrete-Time Sliding Mode Control ( dt-smc ) scheme for linear discrete-time delay system. The delays, affecting the state and the input, are assumed to be known, time-varying and bounded. The considered system is also subject to time-varying Unknown But norm-Bounded ( ubb ) unmatched uncertainties, that act on the state and the delayed state vectors. The designed controller is based on a novel sliding surface. Using a new Lyapunov functional candidate and by introducing slack variables, a less conservative delay-dependent sufficient condition ensuring the asymptotic stability of the closed loop system is derived in terms of Linear Matrix Inequalities ( lmi s). With respect to that condition a new dt-smc law is synthesized. The proposed control algorithm is applied to an Autonomous Underwater Vehicle ( auv ). The simulation results demonstrate the effectiveness of the proposed controller.

This paper is devoted to a detachable fiber-reinforced plastic (FRP) machine parts joint of a new type along with its pull-through strength investigation. The relevance consists of a new mechanical processing technology proposition with the accompanying research into thread helical surfaces strength, which in turn benefits in a significant increase in strength compared to conventional thread joints. The paper presents a numerical experiment carried out with finite element method simulation using LS-DYNA. The helical surfaces contact problem of the rigid threaded insert pulled through the FRP thick cylindrical screw nut with constant velocity has been solved. Technology features of the mechanical processing form-generating method, which forms a threaded surface in one passage of the simple geometry tool are also revealed. The research is concluded with the physical experiment of the steel threaded insert pulled through internal thread made in the FRP thick plate with the pull-through test machine, complete with results statistical assessment was obtained by simulation and testing. It is shown that the combination of the new processing technology with the new geometry of the threaded joint makes it possible to significantly surpass pull-through ultimate strength in comparison with modern analogues of metric threads made in parts directly and even with threaded inserts.

A single-source surface integral equation (SS-SIE) for transverse electric (TE) scattering from cylindrical multilayered objects is proposed in this article. By incorporating the differential surface admittance operator (DSAO) and recursively applying the surface equivalence theorem from innermost to outermost boundaries, an equivalent model with only electric current density on the outermost boundary can be obtained. In addition, an integration approach is proposed, where the small argument expansion of the Hankel function is used to evaluate the singular and nearly singular integrals. Compared with other SIEs, such as the Poggio-Miller-Chang-Harrington-Wu-Tsai (PMCHWT) formulation, the computational expenditure is reduced for multilayered structures because only a single source is needed on the outermost boundary. As shown in the numerical results, the proposed method generates only 19% of unknowns, uses 26% of memory, and requires 29% of the CPU time of the PMCHWT formulation.

The paper presents evaluation of the surface topography obtained after turning of AISI 1045 steel with the use of cemented carbide tools diversified in terms of applied titanium-based coatings. During the research, three types of coatings deposited with the PVD method on a P25 sintered carbide insert were compared: nitride-titanium TiN, nitride-aluminum-titanium TiAlN and carbon-titanium TiC in a wide range of variable cutting speeds 125 - 325 m/min and variable feeds 0.05 - 0.25 mm/rev. The quality of the machined surface was assessed on the Sensofar S neox System optical profile meter using the confocal method. The paper presents the results of 3D parameters, contour maps, isometric views and material ratio curves. The surface topography analysis showed that for the TiAlN coated insert, lower surface roughness parameters were observed in the range of lower cutting speeds and higher feeds, while for higher cutting speeds, lower values of the selected 3D parameters were found for the insert with TiC coating. For the insert with TiC coating, the most even distribution of the valleys and ridges of the machined surface roughness was also observed. The research results determined the range of cutting parameters that allow the selection of the appropriate type of titanium-based coating when machining AISI 1045 steel.

In surface active seismic exploration, the near-surface imaging based on reflection signals provides valuable information for mineral exploration and deeper resources. However, the strong noises at near surface and stretching effects at nonzero offsets with conventional seismic data processing method severely damage the seismic reflection signals with low fold at near surface. The innovative method for the enhancement of seismic signals is the seismic interferometry method. However, due to the one-sided illumination, the seismic interferometry is still not suitable for the retrieval of reflection signals in most practical situations. In this article, we present the correlation-based interferometry (CI) method to enhance the reflection signals for near-surface imaging using the first cross correlation to construct virtual reflection signals and the second cross correlation to achieve the interferometric normal move-out (INMO) correction of the seismic reflection events with no stretching, which keeps the high resolution of near-surface reflection signals. Meanwhile, because of constructive interference stack, the CI method can significantly improve the signal-to-noise ratio (SNR) of reflection signals. The synthetic and field seismic data examples illustrate that the data-driven CI method performs better than the conventional stack (CS) method based on the velocity model for the near-surface reflection imaging.

Pattern recognition techniques are applied to various morphological descriptors to monitor the formation and propagation of surface defects of materials subjected to thermal shock. A low-cement high-alumina castable was synthesized, cured, sintered, and exposed to thermal stability testing using the water quench test. After a certain number of thermal shock cycles, photographs of the samples’ surfaces were taken and subjected to image analysis. The influence of the sintering temperature on the morphology of the detected defects was studied using principal component analysis (PCA) as a pattern recognition technique that is the most informative for extracting possible differences. The morphological descriptors of the defects correspond to the previous results regarding the influence of sintering temperature on the structure of a castable during thermal shocks.

This letter explores the use of intelligent reflecting surfaces (IRSs) to address the line-of-sight (LoS) blockage issue in an indoor visible light communication (VLC) system. This is done while considering practical user behaviors such as random receiver orientation and the presence of obstructions in the direct link between the transmitter and the receiver. Specifically, a system model for an IRS-aided VLC system is proposed and a rate maximization problem is considered to determine the optimal orientation of the IRS mirror array to establish robust non-LoS links. A low-complexity iterative solution based on the sine-cosine algorithm is proposed for this non-convex optimization problem. Simulation results are used to verify the effectiveness of the proposed IRS-aided VLC system design and optimization algorithm in overcoming the LoS blockage issue.

Relevance. Beam cages are the most common type of floor covering for working areas of buildings and structures. Based on the results of a critical analysis of the existing methods for calculating and arranging the dimensions of beam cells, it was established that there are no clear recommendations on the rational range of selection of the sizes of beam cells depending on the surface load. The purpose of the study is to present the areas of rational operation of steel rolling beams, secured against buckling, based on the requirements of the calculation by the method of limit states. Methods. The tasks set in the work, aimed at achieving the research goal, are solved by analytical methods, relying on the basic laws of structural mechanics and existing knowledge about the actual operation of steel rolling beams under load. Methods of mathematical statistics were used to construct the main dependencies presented on the nomograms. Results. Areas of rational operation of steel rolling beams, secured against curvatures, are determined. The area of rational operation of beams is presented in the form of nomograms, which allow at the design stage to use a beam cell of maximum dimensions. As a criterion for rationalization, the criterion of the simultaneous satisfaction of the accepted section of the beam with the requirements of two groups of limiting states with minimum reserves was chosen. A refined algorithm for the layout of the beam cages and a refined method for calculating the cross-section of rolled beams are proposed, which make it possible to arrange the dimensions of the beam cage with a minimum steel consumption. The increase in the overall dimensions of the cells of the working platforms is substantiated.

Bimaterial anti-plane interfacial crack problems with arbitrary distributed forces applied on crack surfaces are numerically investigated. The problems are in essence a kind of boundary value problems about Laplace's equations. Previous work of using Symplectic analytical singular element (SASE) with high-order accuracy and other singular finite elements for calculating mode III stress intensity becomes invalid when the distributed forces on each surface are different. In this paper, Jordan-form special solutions (JFSS) are proposed for the first time. We derive the JFSS for present problems and use them to improve displacement modes of SASE. The distributed forces are therefore converted into equivalent nodal forces of the nodes around SASE. The new SASE is found to be directly and conveniently used for cases where the two distributed forces are either equal (even both zero) or not equal. Numerical examples are provided to demonstrate the effectiveness and accuracy of the present method. The necessity and effectiveness of the JFSS is also validated. Moreover, the JFSS can be applied to some other physical problems represented by the Laplace's equation.

Quasi-satellite orbits (QSOs) are stable retrograde orbits in the restricted three-body problem that have gained attention as a viable candidate for future deep-space missions towards remote planetary satellites. JAXA’s robotic sample return mission MMX will utilize QSOs to perform scientific observations of the Martian moon Phobos before landing on its surface and attempt sample retrieval. The complex dynamical environment around Phobos makes the proximity operations of MMX quite challenging and requires novel and sophisticated techniques for maintaining and transferring between different quasi-satellite orbits. The present paper explores the application of invariant manifolds of unstable retrograde orbits to design transfer trajectories around Phobos. Starting from the equations of the Circular Hill Problem with ellipsoidal Phobos, we first compute families of three-dimensional QSOs using out-of-plane bifurcations near planar orbits. The feasibility of using unstable family members as staging orbits between high-altitude and low-altitude QSOs is later assessed. The final candidates are ranked based on MMX scientific requirements, transfer analyses, and station-keeping costs. It is found that intermediate 3D-QSOs can be maintained with as little as 1 m/s per month. Furthermore, it is discovered that transfer from high-altitude QSOs to low-altitude QSOs can be executed with a total Δ V of less than 40 m/s and total time of flight of less than 5 days.