Surface Configuration Research Articles

Hardware Implementations of a Deep Learning Approach to Optimal Configuration of Reconfigurable Intelligence Surfaces

Reconfigurable intelligent surfaces (RIS) offer the potential to customize the radio propagation environment for wireless networks, and will be a key element for 6G communications. However, due to the unique constraints in these systems, the optimization problems associated to RIS configuration are challenging to solve. This paper illustrates a new approach to the RIS configuration problem, based on the use of artificial intelligence (AI) and deep learning (DL) algorithms. Concretely, a custom convolutional neural network (CNN) intended for edge computing is presented, and implementations on different representative edge devices are compared, including the use of commercial AI-oriented devices and a field-programmable gate array (FPGA) platform. This FPGA option provides the best performance, with ×20 performance increase over the closest FP32, GPU-accelerated option, and almost ×3 performance advantage when compared with the INT8-quantized, TPU-accelerated implementation. More noticeably, this is achieved even when high-level synthesis (HLS) tools are used and no custom accelerators are developed. At the same time, the inherent reconfigurability of FPGAs opens a new field for their use as enabler hardware in RIS applications.

How Do the Dynamics of Urbanization Affect the Thermal Environment? A Case from an Urban Agglomeration in Lower Gangetic Plain (India)

Urban growth and development has significantly affected urban heat island (UHI) due to urbanization. Particularly in the cities in developing countries, the assessment of UHI has emerged as one of the core research themes as it significantly affects the ecological environment and livability in cities. Thus, the assessment of UHI is crucial for climate mitigation and sustainable urban landscape planning. This study identifies the dynamics of landscape patterns and the impact of composition and configuration on the thermal environment in English Bazar Urban Agglomeration (EBUA), Eastern India, along the urban–rural gradient (URG) approach. Geospatial approaches and spatial metrics were employed to assess the impact of the landscape pattern on the thermal environment. Descriptive and inferential statistics have also been used to find the effects of landscape patterns on the thermal environment. The result has also been validated based on the location and correlation analysis. The built-up area increased by about 63.54%; vegetation covers and water bodies declined by 56.72% and 67.99% from 2001 to 2021. Land surface temperature (LST) decreased with increasing distance from the core of the city. LST declined by about 0.45 °C per kilometer from the core of the city towards the outside. LST had a positive correlation with IS and a negative correlation with green space (GS) and blue space (BS). The mean aggregation of the impervious patches was larger (73.21%) than the GS (43.18%) and BS (49.02%). The aggregation of impervious surface (IS) was positively correlated, and aggregations of GS and BS had a negative correlation with LST. Findings suggest that the spatial composition and configuration of the impervious surface, GS, and BS must be considered in landscape planning and design framework to make the city more livable.

The applicability of stripe light projection data to the determination of fractal dimensions of blast-cleaned steel surfaces

This paper is concerned with the assessment of fractal dimensions of blast-cleaned steel substrates using stripe line projection on 12 surface configurations. By means of the box-counting method and a Design of Experiment (DoE) approach, the factors abrasive type, surface preparation grade, surface roughness, and measurement direction were analyzed. The results revealed that the factor surface roughness contributed 52.5 % to the fractal dimensions. The factor measurement direction contributed 14.7 % (even up to 20 % once interactions were included) to the fractal dimension. Particularly the profile “formation” values were significantly influenced by the factor measurement direction, with contributions ranging up to 17.2 %. The potential limitations on the optical stripe light projection in capturing variations in fractal dimensions, especially in the abscissa-direction (formation), are highlighted. Whereas the box-counting method offers valuable insights, the stripe line projection introduces variations in the derived fractal dimensions. Stripe line projection shall be carefully considered when applied to fractal analysis.

Salt-resistant solar water desalination system via surface modification and configuration engineering

Floating solar water desalination systems have received a lot of attention since they are portable, low cost, environmentally friendly, and highly efficient. However, salt accumulation on the evaporation surface and water transfer channels is one of the main obstacle to the development of these systems. In this work, two strategies of surface modification and configuration engineering are focused on to make the devices salt-resistant. First, the system becomes salt-resistant by formation of a hydration layer on the water manager and light absorber surface through cross-linking of polyethylene glycol diacrylate. Remarkably, the surface-modified device shows a water evaporation rate of 1.34 kg.m−2.h−1 and a conversion efficiency of 91.75 % in artificial seawater. There is no salt accumulation on the evaporation surface of surface-modified devices after desalination in the simulated seawater. In the second strategy, the water transferring to the evaporation surface and water evaporation rate are balanced by tuning the number of water transport channels and location. The engineered device shows an evaporation rate of 0.98 kg.m−2.h−1 and an efficiency of 75.5 % in a high saline solution (20 wt% NaCl). Simultaneous surface modification and configuration engineering improve the salt resistivity, showing that the configuration should be engineered according to the water salinity.

Dual-edged sword effects of sulfation/hydration on Ce-doped TiO2(001) single-atom catalyst for NH3-SCR reaction: A first-principles study

SO2/H2O-resistance remains challenges for selective catalytic reduction with NH3 (NH3-SCR). The detailed promotion and/or inhibition effects of sulfation/hydration on cerium-titanium (CT) catalysts for NH3-SCR are still controversial. Herein, a series of adsorption characteristics, bonding strengths, electronic effects, and reaction pathways were performed by first-principles density functional theory calculations to explore the structure-performance/resistance of CT catalysts and unravel the effects of sulfation/hydration for NH3-SCR. We constructed six CT catalyst structures based on three TiO2 facets [(001)/(101)/(100)] and two surface configurations [single-atom (SA)/interface (IF)]. CT(001)-SA could protect the active Ce site from sulfation/hydration with TiO2(001) as SO2/H2O-trapping site, which was the optimal SO2/H2O-resistant structure among six CT catalyst structures. An electron-deficient state of CT(001)-SA was caused by sulfation/hydration through electron capture behavior. From the perspective of reactants adsorption, this electron-deficient state not only promoted the NH3/NO adsorption but also suppressed the secondary sulfation/hydration. As for NH3-SCR pathways, hydration promoted NH3 dissociation, N-N coupling, and N-O breaking, but inhibited the H1 transfer (rate-determining step). Sulfation impaired the redox ability of Ce site, promoted H1 transfer and N-O breaking, but inhibited the NH3 dissociation, N-N coupling, and H2 transfer (rate-determining step). Hence, sulfation/hydration exhibited “dual-edged sword” effects for NH3-SCR on CT(001)-SA via electronic effects.

Mechanical behavior investigation of fused deposition modeling joints by using different bonding geometry with variable adhesive thickness

PurposeAdhesively bonded joints are used in many fields, especially in the automotive, marine, aviation, defense and outdoor industries. Adhesive bonding offers advantages over traditional mechanical methods, including the ability to join diverse materials, even load distribution and efficient thermal-electrical insulation. This study aims to investigate the mechanical properties of adhesively bonded joints, focusing on adherends produced with auxetic and flat surfaces adhered with varying adhesive thicknesses.Design/methodology/approachThe research uses three-dimensional (3D)-printed materials, polyethylene terephthalate glycol and polylactic acid, and two adhesive types with ductile and brittle properties for single lap joints, analyzing their mechanical performance through tensile testing. The adhesion region of one of these adherends was formed with a flat surface and the other with an auxetic surface. Adhesively bonded joints were produced with 0.2, 0.3 and 0.4 mm bonding thickness.FindingsResults reveal that auxetic adherends exhibit higher strength compared to flat surfaces. Interestingly, the strength of ductile adhesives in auxetic bonded joints increases with adhesive thickness, while brittle adhesive strength decreases with thicker auxetic bonds. Moreover, the auxetic structure displays reduced elongation under comparable force.Originality/valueThe findings emphasize the intricate interplay between adhesive type, bonded surface configuration of adherend and bonding thickness, crucial for understanding the mechanical behavior of adhesively bonded joints in the context of 3D-printed materials.

Atomistic Modeling of Spinel Oxide Particle Shapes and Reshaping under OER Conditions

The surface configurations of the low-index facets of a set of spinel oxides are investigated using DFT+U calculations to derive surface energies and predict equilibrium nanoparticle shapes via the Wulff construction. Two very different conditions are investigated, corresponding to application either in heterogeneous catalysis or in electrocatalysis. First, the bare stoichiometric surfaces of NiFe2O4, CoFe2O4, NiCo2O4, and ZnCo2O4 spinels are studied to model their use as high-temperature oxidation catalysts. Second, focusing attention on the electrochemical oxygen evolution reaction (OER) and on the CoFe2O4 inverse spinel as the most promising OER catalyst, we generate surface configurations by adsorbing OER intermediates and, in an innovative study, we recalculate surface energies taking into account adsorption and environmental conditions, i.e., applied electrode potential and O2 pressure. We predict that under OER operating conditions, (111) facets are dominant in CoFe2O4 nanoparticle shapes, in fair agreement with microscopy measurements. Importantly, in the OER case, we predict a strong dependence of nanoparticle shape upon O2 pressure. Increasing O2 pressure increases the size of the higher-index (111) and (110) facets at the expense of the (001) more catalytically active facet, whereas the opposite occurs at low O2 pressure. These predictions should be experimentally verifiable and help define the optimal OER operative conditions.

Anisotropic elastic and thermal properties and damage tolerance of CrH: A first-principles calculation

The elastic properties, thermal properties, and damage tolerance of one cubic (C-CrH) and two hexagonal (H1-CrH and H2-CrH) CrH hydrides were investigated using first-principles calculation based on density functional theory (DFT). The results showed that C-CrH is brittle, while H1-CrH and H2-CrH are ductile. Compared to the hexagonal CrH, C-CrH has the highest hardness, the largest damage tolerance, and the largest fracture toughness values. Three-dimensional (3D) surface configurations and two-dimensional (2D) planar projections were used to estimate the elastic anisotropy, and the elastic anisotropy is in the order of H2-CrH > C-CrH > H1-CrH. In addition, C-CrH has the highest minimum thermal conductivity among these CrH hydrides. CrH hydrides are anisotropic in minimum thermal conductivity with the order of H1-CrH > C-CrH > H2-CrH.

Thermo-hydraulic performance of tungsten flat tile type divertor target with two types of novel engineered cooling channel wall

The divertor is one of the key components in magnetic confinement fusion reactors. Improving the heat transfer performance of the divertor has great importance for promoting its service capacity. This work proposed a new kind of cooling surface configuration for a flat-type divertor design, which is based on the concept of synergetic heat transfer enhancement via combination of a sinusoidal undulation structure with a micro-nano structured surface (copper-mesh brazed coating). The combination surface configuration is preliminarily obtained by numerical optimization based on the calibrated model of subcooled flow boiling heat transfer. Then, experimental mockups were fabricated and tests with high heat flux (HHF) conditions were conducted to examine the effects of the new design. Both the numerical and experimental results confirm that the incident critical heat flux is increased from 15 MW/m2 of the micro-nano structured flat surface case to over 22 MW/m2 of the combination case under the conditions of relatively low flow velocity of 3 m/s and low flow resistance increase of 7.3 %.

Surface Reconstructions in II-VI Quantum Dots.

Although density functional theory (DFT) calculations have been crucial in our understanding of colloidal quantum dots (QDs), simulations are commonly carried out on QD models that are significantly smaller than those generally found experimentally. While smaller models allow for efficient study of local surface configurations, increasing the size of the QD model will increase the size or number of facets, which can in turn influence the energetics and characteristics of trap formation. Moreover, core-shell structures can only be studied with QD models that are large enough to accommodate the different layers with the correct thickness. Here, we use DFT calculations to study the electronic properties of QDs as a function of size, up to a diameter of ∼4.5 nm. We show that increasing the size of QD models traditionally used in DFT studies leads to a disappearance of the band gap and localization of the HOMO and LUMO levels on facet-specific regions of the QD surface. We attribute this to the lateral coupling of surface orbitals and the formation of surface bands. The introduction of surface vacancies and their a posteriori refilling with Z-type ligands leads to surface reconstructions that widen the band gap and delocalize both the HOMO and LUMO. These results show that the surface geometry of the facets plays a pivotal role in defining the electronic properties of the QD.

Effect of passive particle shape on effective force in active bath

<sec>In active matter, the effective force between passive objects is crucial for their structure and dynamics, which is the basis for understanding the complex behaviors within active systems. Unlike equilibrium states, the factors such as the surface configuration, size, and confinement strength significantly influence the effective forces between passive particles. Previous studies have shown that the shapes of passive particles affect the aggregation of active particles, leading to different forces experienced by passive particles with different shapes. However, recently, a long-range attractive force between passive platelike particles, caused by the bacterial flow field instead of the direct bacterium-plate collisions in active bacterial suspensions, has been found. This raises an intriguing question: how does hydrodynamics affect the forces on passive particles of different shapes in different ways?</sec><sec>In this work, we investigate the effective forces exerted on passive spherical and plate-like particles immersed in bacterial suspensions by optical-tweezers experiments. The effective force between passive particles can be calculated from the formula, <inline-formula><tex-math id="M1">\begin{document}$ {F_{{\text{eff}}}} = {\text{ }}k\left\langle {\Delta d} \right\rangle /2 $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M1.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M1.png"/></alternatives></inline-formula>, where <inline-formula><tex-math id="M2">\begin{document}$ \left\langle {\Delta d} \right\rangle $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M2.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M2.png"/></alternatives></inline-formula> represents the difference in distance between the passive particles in the bacterial bath and those in the solution without bacteria, <inline-formula><tex-math id="M3">\begin{document}$ k $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M3.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M3.png"/></alternatives></inline-formula> is the effective stiffness of optical traps. The <inline-formula><tex-math id="M5">\begin{document}$ {{{F}}}_{{\mathrm{e}}{\mathrm{f}}{\mathrm{f}}} > 0 $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M5.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M5.png"/></alternatives></inline-formula> indicates a repulsive force between passive particles, and the <inline-formula><tex-math id="M6">\begin{document}$ {F_{{\text{eff}}}} \lt {\text{ }}0 $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M6.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="15-20240650_M6.png"/></alternatives></inline-formula> represents an effective attractive force between passive particles. Our results demonstrate that the passive spherical particles experience short-range repulsion, while plate-like particles are subjected to long-range attraction. This highlights the substantial effect of particle shape on their effective forces.</sec><sec>The forces on passive particles are mainly attributed to two factors: direct bacterium-particle collisions and the bacterial flow field. The analysis of the bacterial concentration and orientation distribution around passive particles reveals that for spherical particles, the concentration of bacteria between particles is higher than that outside the particles, but there is almost no difference in the orientation order between bacteria inside and outside the particles. This suggests that the effective repulsion between spherical particles is mainly due to the direct bacterial collisions. Conversely, for plate-like particles, the long-range attraction is primarily influenced by the bacterial flow field rather than their direct collisions, which is evidenced by the higher bacterial density and orientation order inside the two plates compared with those outside the two plates. This study provides strong evidence that the effective force between passive particles is shape dependent in active bath, and offers new insights into controlling active-directed assembly.</sec>

Stability, electronic properties and CO adsorption properties of bimetallic PtAg/Pt(111) surfaces.

Aiming at a better fundamental understanding of the chemistry of bimetallic PtAg/Pt(111) surfaces, we have investigated the stability, electronic properties and CO adsorption properties of bimetallic PtAg surfaces, including pseudomorphic Ag film covered Pt(111) surfaces and PtxAg1-x/Pt(111) monolayer surface alloys, using periodic density functional theory calculations. The data provide detailed insights into the relative stabilities of different surface configurations, as indicated by their formation enthalpies and surface energies, and changes in their electronic properties, i.e., in the projected local densities of states and shifts in the d-band center. The adsorption properties of different Ptn ensembles were systematically tested using CO as a probe molecule. In addition to electronic ligand and strain effects, we were particularly interested in the role of different adsorption sites and of the local COad coverage, given by the number of CO molecules per Pt surface atom in the Ptn ensemble. Different from PdAg surfaces, variations in the adsorption energy with adsorption sites and with increasing local coverage are small up to one COad per Pt surface atom. Finally, formation of multicarbonyl species with more than one COad per Pt surface atom was tested for separated Pt1 monomers and can be excluded at finite temperatures. General trends and aspects are derived by comparison with comparable data for PdAg bimetallic surfaces. Fundamental insights relevant for applications of bimetallic Pt catalysts, specifically PtAg catalysts, are briefly discussed.

Optimal Configuration of Reconfigurable Intelligent Surfaces with Arbitrary Discrete Phase Shifts

Optimal Configuration of Reconfigurable Intelligent Surfaces with Arbitrary Discrete Phase Shifts

Exploring inhomogeneous surfaces: Ti-rich SrTiO3(110) reconstructions via active learning.

The investigation of inhomogeneous surfaces, where various local structures coexist, is crucial for understanding interfaces of technological interest, yet it presents significant challenges. Here, we study the atomic configurations of the (2 × m) Ti-rich surfaces at (110)-oriented SrTiO3 by bringing together scanning tunneling microscopy and transferable neural-network force fields combined with evolutionary exploration. We leverage an active learning methodology to iteratively extend the training data as needed for different configurations. Training on only small well-known reconstructions, we are able to extrapolate to the complicated and diverse overlayers encountered in different regions of the inhomogeneous SrTiO3(110)-(2 × m) surface. Our machine-learning-backed approach generates several new candidate structures, in good agreement with experiment and verified using density functional theory. The approach could be extended to other complex metal oxides featuring large coexisting surface reconstructions.

Federated Deep Reinforcement Learning-Based Intelligent Surface Configuration in 6G Secure Airport Networks

Federated Deep Reinforcement Learning-Based Intelligent Surface Configuration in 6G Secure Airport Networks

Tuning the electronic structure of Pd by the surface configuration of Al2O3 for hydrogenation reactions.

The electronic interaction between a metal and a support modulates the electronic structures of supported metals and plays an important role in manipulating their catalytic performance. However, this interaction is mainly realized in heterogeneous catalysts composed of reducible oxides. Herein, we demonstrate the electronic interaction between γ-Al2O3 and η-Al2O3 with varying acid-base properties and supported Pd nanoparticles (NPs) of 2 nm in size. The strength and number of acid-base sites on the supports and catalysts were systemically characterized by FT-IR spectroscopy and TPD. The supported Pd NPs exhibit electron-rich surface properties by receiving electrons from the electron-donating basic sites on γ-Al2O3, which are beneficial for catalyzing the hydrogenation of nitrobenzene. In contrast, Pd NPs loaded on η-Al2O3 are electron-deficient because of the rich electron-withdrawing acid sites of η-Al2O3. As a result, Pd/η-Al2O3 exhibits higher catalytic activity in phenylacetylene hydrogenation than Pd/γ-Al2O3. Our results suggest a promising route for designing high-performance catalysts by adjusting the acid-base properties of Al2O3 supports to maneuver the electronic structures of metals.

Structural dynamics of PtSn/SiO2 for propane dehydrogenation

Operando characterization reveals the structural dynamics of PtSn/SiO2 catalysts, hinting at a Pt-rich surface configuration for optimal propane dehydrogenation performance.

Numerical simulation of shear driven film instability over heterogeneous surfaces via enhanced lubrication theory

The prediction of the transition between continuous film, ensemble of rivulets and moving droplets is crucial in applications such as in-flight icing on airfoil wings or a number of chemical reactors. Here, lubrication theory is used to numerically investigate the stability of a continuous liquid film, driven by shear, over a heterogeneous surface. The disjoining pressure is used to model surface wettability, while the full implementation of the film curvature allows to investigate contact angles up to 60°. Different heterogeneous surface configurations occurring in real problems are investigated. An extended computational campaign records the transition from continuous film to rivulet regime and, if present, the further transition from rivulet to droplets at different flow conditions. A moving grid approach allows for accurate prediction of instability phenomena at low computational cost. The numerical results are successfully validated with experimental evidence in case of critical flow rate leading to a stable dry patch and compared with literature results involving the inherently multiscale in-flight icing phenomenon, providing useful statistical information, required to transfer the present detailed small-scale information into larger scale CFD computational approaches.

Reducing the vibration excitability of a metal plate by applying variable vibrodamping inserts

Thin-walled steel structures of process equipment and vehicles composed of plates are constantly agitated and become powerful sources and conductors of acoustic vibration. To reduce acoustic vibration, special vibrodamping coatings are usually applied to the plate surface by gluing or spraying. However for many engineering applications, concerned with reduction of acoustic vibration, the use of vibrodamping coatings is limited or impossible for a number of reasons, namely, the variability in geometric surface configuration of thin-walled steel structures, stringent restrictions of structure weight (e.g. in hovercrafts) and others. An alternative solution is the use of piece vibrodamping rubber inserts, applied to the plate through perforation. The inserts can be made either solid or with inner channel for free shift of extra weight in the form of a ball. The paper summarizes the results of experimental studies on reducing the loss factor for vibration excitability of plates with inserts.

High-entropy intermetallics: emerging inorganic materials for designing high-performance catalysts.

Alloy materials have been used as promising platforms to upgrade catalytic performance that cannot be achieved with conventional monometallic materials. As a result of numerous efforts, the recent progress in the field of alloy catalysis has been remarkable, and a wide range of new advanced alloys have been considered as potential electro/thermal catalysts. Among advanced alloy materials, high-entropy intermetallics are novel materials, and their excellent catalytic performance has recently been reported. High-entropy intermetallics have several advantages over disordered solid-solution high-entropy alloys, that is, greater structural/thermal stability, more facile site isolation, more precise control of electronic structures, tunability, and multifunctionality. A multidimensional compositional space is indeed limitless, but such a compositional space also provides a well-designed surface configuration because of its ordered nature. In this review, we will provide fundamental insights into high-entropy intermetallics, including thermodynamic properties, synthesis requirements, characterization techniques, roles in catalysis, and reaction examples. The comprehensive information provided in this review will highlight the great application potential of high-entropy intermetallics for catalysis, and will accelerate the development of this newly developed field.