Flat Ones Research Articles

Impingement of vortex dipole on heated boundaries and related thermal plume dynamics

The profound influence of an externally induced vortex dipole on thermal plume dynamics is numerically studied for varying Rayleigh numbers (Ra) employing the Bhatnagar–Gross–Krook collision model-based lattice Boltzmann method with a double distribution function approach. This study is extended to vortex dipole impingement with different types of heated bottom boundaries of two-dimensional domain, such as flat, “V-shaped,” and “inverted-V-shaped.” The vortex dipole impingement with the heated boundaries generates secondary vortices, which in turn produce vortex-driven thermal plumes, thereby advancing plume generation. The subsequent merging of the plumes enhances heat transport and leads to a continuous plume ascent. The presence of convex corners facilitates flow separation and also gives rise to the formation of secondary vortex dipoles, thereby significantly impacting the continuous generation of jet-like plumes when compared to concave configurations. The lack of an external vortex in pure buoyancy-driven flows produces less pronounced jet-like plumes and a relatively low Nusselt number. The boundary types and Ra significantly influence the vorticity production, resulting in higher enstrophy and palinstrophy for convex boundaries compared to flat and concave ones. A lower Prandtl number increases secondary vortices and corner rolls, leading to larger velocity gradients, higher thermal diffusivity, resulting in increased kinetic energy and thermal dissipation rates. The increased cell height enhances heat transfer at the top boundary due to improved heat convection from the slanted boundary and influence of early dipole impingement. Furthermore, kinetic energy dissipates in the dipole-driven flows and increases in the buoyancy-dominated flows.

An Enhanced Approach for High-Strain Plasticity in Flat Anisotropic Specimens with Progressively Distorting Neck Sections

An Enhanced Approach for High-Strain Plasticity in Flat Anisotropic Specimens with Progressively Distorting Neck Sections

Bi-material nanofibrous electrospun junctions: A versatile tool to mimic the muscle–tendon interface

Soft robotics aims to replicate the structure and mechanics of skeletal muscles. The challenge lies in seamlessly integrating these muscle-inspired soft actuators with the joints they intend to actuate, resembling the natural connection between muscles and tendons (i.e., myotendinous junction). This study addresses this issue by producing electrospun bundles of aligned nanofibers using a thermoplastic polyurethane, mimicking the muscle fascicle, and nylon 6.6 for the tendon one. A novel method was developed to create electrospun bi-material bundles with two different types of myotendinous-inspired junctions, called flat and conical. Scanning electron microscopy and microtomography analyses confirmed that conical junctions mimicked natural myotendinous structures better than flat ones. Tensile mechanical tests demonstrated that bi-material junctions reached stress at failure comparable to polyurethane bundles (11 ± 2 MPa), with the conical junction showing stiffness (0.13 ± 0.02 N/mm) and net elastic modulus (153 ± 10 MPa) values closer to the natural myotendinous ones. Cyclic tests verified the mechanical stability of junctions and their ability to dampen nylon 6.6 hardening over time. Moreover, all bundles withstood cyclic loading without breaking. These findings suggest the potential of biomimetic electrospun junctions for applications in soft robotics, marking a significant step toward advancing this field.

Not All about the Money: The Role of Financial Information in Promoting Residential Rooftop Photovoltaics

This study investigates the role of financial information in shaping the intention to adopt (ITA) Residential Rooftop Photovoltaic (RPV) systems in Israel—a country with a surprisingly low RPV adoption rate given the high solar irradiance, and significant governmental support for RPV. We used an online survey of 899 respondents to examine how different presentations of RPV revenues impact both RPV deal comprehension and ITA. Our results align with existing literature on the roles of early technology adopters and pro-environmental characteristics while introducing two novel findings. First, households value their roofs—especially flat ones used for leisure. This negatively impacts ITA. Second, we found a positive correlation between trust in government entities and ITA, underscoring the importance of trust in institutions. Although financial information does enhance RPV deal comprehension, it does not significantly influence ITA. This study concludes that RPV penetration should not be promoted solely by financial incentives, but also by other motivations like environmental concerns, novelty seeking, and improved institutional trust.

On Some Weingarten Surfaces in the Special Linear Group SL(2,R)

We classify Weingarten conoids in the real special linear group SL(2,R). In particular, there is no linear Weingarten nontrivial conoids in SL(2,R). We also prove that the only conoids in SL(2,R) with constant Gaussian curvature are the flat ones. Finally, we show that any surface that is invariant under left translations of the subgroup N is a Weingarten surface.

Constructing geometrical models of spherical analogs of the involute of a circle and cycloid

The common properties of images on a plane and a sphere are considered in the scientific works by scientists-designers of spherical mechanisms. This is due to the fact that the plane and the sphere share common geometric parameters. They include constancy at all points of the Gaussian curve, which has a zero value for a plane and a positive value for a sphere. Figures belonging to them can slide freely on both surfaces. With unlimited growth of the radius of the sphere, its limited section approaches the plane, and the spherical shape transforms into a plane. Thus, a loxodrome that crosses all meridians at a constant angle is transformed into a logarithmic spiral that intersects at a constant angle the radius vectors that come from the pole. The tooth profile of cylindrical gears is outlined by the involute of a circle. A spherical involute is used for the corresponding bevel gears. Other spherical curves are also known, which are analogs of flat ones. The formation of a cycloid and an involute of a circle are associated with the mutual rolling of a line segment with each of these figures. If the segment is fixed and the circle rolls along it, then the point of the circle describes the cycloid. In the case of a stationary circle along which a segment is rolled, the point of the segment will execute the involute. To move to the spherical analogs of these curves, it is necessary to replace the circle with a cone, and the straight line with a plane. The spherical prototype of the cycloid will be the trajectory of the point of the base of the cone, which rolls along the plane, that is, along the sweep of the cone. The sweep of a cone is a sector, the radius of the limiting circle of which is equal to the generating cone. If this sweep, like a section of a plane, is rolled around a fixed cone, when its top coincides with the center of the sector, then the point of the limiting radius of the sector will execute a spherical involute. This paper analytically implements these two motions and reports the parametric equations of the spherical analogs of the circle involute and the cycloid

Interaction of Bacteria, Immune Cells, and Surface Topography in Periprosthetic Joint Infections.

The incidence of periprosthetic joint infections (PJIs) is ~2% of total procedures and it is expected to rise due to an ageing population. Despite the large burden PJI has on both the individual and society, the immune response to the most commonly isolated pathogens, i.e., Staphylococcus aureus and Staphylococcus epidermidis, remains incompletely understood. In this work, we integrate the analysis of synovial fluids from patients undergoing hip and knee replacement surgery with in-vitro experimental data obtained using a newly developed platform, mimicking the environment of periprosthetic implants. We found that the presence of an implant, even in patients undergoing aseptic revisions, is sufficient to induce an immune response, which is significantly different between septic and aseptic revisions. This difference is confirmed by the presence of pro- and anti-inflammatory cytokines in synovial fluids. Moreover, we discovered that the immune response is also dependent on the type of bacteria and the topography of the implant surface. While S. epidermidis seems to be able to hide better from the attack of the immune system when cultured on rough surfaces (indicative of uncemented prostheses), S. aureus reacts differently depending on the contact surface it is exposed to. The experiments we performed in-vitro also showed a higher biofilm formation on rough surfaces compared to flat ones for both species, suggesting that the topography of the implant could influence both biofilm formation and the consequent immune response.

Mizohata–Takeuchi estimates in the plane

AbstractSuppose that is a smooth compact hypersurface in and is an appropriate measure on . If is the extension operator associated with , then the Mizohata–Takeuchi conjecture asserts that for all functions and weights , where the is taken over all tubes in of cross‐section 1, and . This paper investigates how far we can go in proving the Mizohata–Takeuchi conjecture in if we only take the decay properties of into consideration. As a consequence of our results, we obtain new estimates for a class of convex curves that include exponentially flat ones such as , , .

Combined impacts of square fins fitted wavy wings and micropolar magnetized-radiative nanofluid on the heat sink performance

The objective of this article is to assess numerically the effectiveness of using square fins supported by wavy wings on the performance of inclined heat sink box filled with magnetized-radiative nanoliquid. The software COMSOL Multiphysics, which is based on the finite element method, is employed to establish the numerical research. In a first stage, rectangular wings on all the four sides support the square fins. In a second stage, wavy rectangular wings are used to improve the heat sink box performance. A comparison between the influence of wavy and flat wings on the heat sink box performance and the influences of wings length (δ) and wings waves number (λ) for various heat sink box inclinations (γ) are discussed. The data reveal that backing the classical square fins with flat wings help to the betterment of the heat sink box performance by 10.52 %. Furthermore, extending the length of wings enhances the heat sink box performance by 15.98 %. The wavy wings gives better yield for heat exchange performance instead of flat ones. Moreover, the multiplication of the number of waves improves the heat sink box performance.

Numerical investigations on punching shear behavior of eccentrically loaded reinforced concrete footings

The undesired punching shear failure around the columns is the most critical scenario that causes a brittle failure of reinforced concrete flat plates. Matured studies and code provisions are available to assess the punching shear strength of thin flat plates. The punching shear behavior of thick plates differs from thin flat ones and produces a steeper shear crack. At the construction of thick footing plates, as some tolerances are permitted, the footing may be subjected to eccentric loading. However, there is a lack of studies on the footing performance under eccentric load. This numerical study aims to develop and validate a numerical model to examine the punching shear behavior of full-scale eccentrically loaded footings. The results have shown the accurate prediction of the developed numerical model of the reference case studies. The validated model has been utilized to examine the influence of three eccentricity ratios; 1/18, 1/9, and 1/6 of the footing length. The results demonstrated the significant influence of the load eccentricity on the punching shear strength of footings and the shear crack distribution. Moreover, parametric studies on sets of footings indicate that column perimeter to depth ratio and shear span to depth ratio play a key role in determining the footing behavior. The shear strength is found to increase with the increase of column perimeter to depth ratio and with the reduction of shear span to depth ratio. In addition, the negative effect of the eccentricity is less pronounced in the case of footings with a low shear span to depth ratio. Furthermore, the prEC2 approach for predicting the shear strength of eccentrically loaded footings has been assessed. It has been observed that the codeequation is found inaccurate with eccentric loading cases and needs some modification. The study ended with the development and verification of an equation that helps in obtaining more accurate results compared to the reference tests.

Rough discrete fracture network multi-parameter joint modeling based on improved neural spline flow

Discrete fracture network (DFN) modeling is a popular method for studying reservoir characteristics. However, on one hand of the existing DFN studies, the correlations that may exist among the multi-dimensional parameters of the fracture (dip, dip direction, trace length, aperture, and roughness) were ignored and each property was estimated independently. On the other hand, the 3D DFN models were simplified as flats without roughness. Therefore, this study proposes a simulation method for the rough discrete fracture network while considering multi-parameter joint distribution to make up for the stated deficiencies: (1) An improved deep learning model for the joint distribution estimation and joint sampling of the multi-dimensional parameters of the fracture is proposed, which is the Neural Spline Flow improved by the Multimodal Distribution (NSF-MD). The initial distribution of the Neural Spline Flow (NSF) is improved from a unimodal Gaussian to a multimodal mixed Gaussian, which enhances the fitting ability of the NSF model for the multimodal joint distribution. (2) A modeling assumption of the 3D rough fracture surface is presented to improve the conventional flat ones. In this way, a 3D rough fracture surface is generated by the NURBS tensor product of the fractal traces, and the fractal trace is simulated parametrically based on the fractal dimension. Finally, an outcrop DFN modeling application from southwest China indicates that the NSF-MD can simulate the correlations among the fracture multi-dimensional parameters and that the 3D rough discrete fracture network model (RDFN) increases the representation of the fracture roughness. The Wasserstein distance, which is an indicator quantifying the accuracy of the joint multi-parameter estimation, of the NSF-MD model was 72.4% and 81.9% better than that of the NSF model and that of the conventional method with parameters estimated independently, respectively. The relative distance error (RDE) and the global angle error (GAE) of the fractal traces were 87.9% and 88.3% more accurate than those of the conventional linear traces, respectively.

Air distribution efficiency improving in the premises by rectangular air streams

Abstract This article discusses the topical issue of improving the distribution of air in the premise due to application of the all type rectangular air streams: flat, axisymmetric and rectangular ones. The purpose of the article is research of the all types rectangular air streams, analytical dependencies obtaining for determination of the air velocity attenuation coefficient, aerodynamic local resistance coefficient and noise level from the ratio of slit length to its height; optimization of the inflow slit side's ratio. It has been established that increase of the inflow slit sides ratio results in the air velocity attenuation coefficient decrease and results in increase of the noise level and resistance coefficient of the rectangular slit. The optimal ratio of the sides of a rectangular slit is determined by the combination of aerodynamics and energetics, as well as of the sound power level.

(Digital Presentation) Operando Laser Scattering- and Inverted RDE-Based Approaches for the Development of Additive-Assisted Electrodeposited Co Interconnects

The development of Co interconnects by electrochemical means is more challenging than that of Cu-based analogues not only due to the ever decreasing critical feature dimensions but also to intrinsic complications of the water/Co system, as Co electrodeposition processes are inevitably accompanied by the competing hydrogen evolution reaction (HER). Aiming at enabling a more knowledge-driven Co interconnect development, we present herein two novel experimental approaches that reveal important insights on the complex interplay between additive-assisted Co electrodeposition and the HER.In a first instance, we present a custom-made inverted RDE instrument, particularly suitable for studying metal deposition processes that are accompanied by HER or any other gas evolving side reaction. We investigate the influence of a model redox-active suppressor additive on the electrochemical deposition of cobalt by means of linear sweep voltammetry and galvanostatic electrolysis coupled to online gas chromatography analysis. We find that under specific experimental conditions, addition of minor amounts of the additive to the standard Co-based virgin make-up solution significantly decreases the rate and efficiency of Co deposition, and favors instead the competing HER. Moreover, we identify and quantify the reductive conversion of the additive that accompanies the primary metal deposition process. Importantly, our approach complements standard screening Co plating studies as it succeeds to directly deconvolve the overall process into its three individual components, namely the metal ion reduction, the HER and the additive activation.Secondly, to develop understanding of proton dynamics in the diffusion layers generated by the metal electrodeposition processes we introduce a simple, non-invasive pH-sensing approach that is based on the Tyndall effect enhancement modulated by pH-controlled agglomeration events. We employ a laser beam laterally aligned to an electrode surface where additive-assisted cobalt deposition and hydrogen evolution take place simultaneously. This configuration allows the visualization of pH changes that result in precipitate formation and that extend to greater distances over patterned surfaces compared to flat ones, demonstrating a pH-guiding effect in superconformal metal deposition. The method provides real-time visualization of the pH dynamics with high lateral spatial resolution without physically or chemically influencing the investigated system. We suggest that applicability of the method can be extended to other processes where nanoaggregation/decomplexation inherently occur, as part of the investigated phenomena, at light-addressable interfaces.Overall, these investigations provide new insights for the further development of interconnect technology and metal deposition processes in general.. Figure 1

AFM macro-probes to investigate whole 3D cardiac spheroids

In its many applications, the Atomic Force Microscope (AFM) is a promising tool in cardiac mechanobiology because it can unravel the viscoelastic and mechano-dynamic properties of individual cardiomyocytes. However, the biophysical investigation of more accurate 3D models is hampered by commercial probes, which typically operate at the cell sub-compartmental resolution. We have previously shown how flat macro-probes can overcome these limitations by extending the AFM mechanical measurements to multicellular aggregates. Such macro-probes are fabricated by standard micromachining and carry a flat polymeric wedge to offset the AFM mounting tilt. Therefore, the AFM is upgraded to a micro-parallel plate rheometer with unmatched force range and sensitivity. In this article, we show how these macro-probes can be applied to reveal the global rheology of primary cardiomyocytes spheroids, by performing stress-relaxation tests. More importantly, we demonstrate that these macro-probes can be used as passive sensors capable of monitoring the spheroid beating force and beating pattern, and to perform a “micro-CPR” on the spheroid itself. • Cardiac mechanobiology has been succesfully studied at the single-cell level using Atomic Force Microscopy (AFM). • Commercial cantilevers can interrogate the sample at the single-cell level only, so we fabricate large and flat ones. • We can now disclose relevant information regarding the mechanical properties of whole 3D cardiac spheroids. • We perform stress-relaxation experiments, which give us an estimation of the spheroids' viscoelasticity. • By mechanically loading the spheroids with cyclic compressions, we stimulate their autonomous beating.

Dynamical evolution of Ge quantum dots on Si(111): From island formation to high temperature decay

Heteroepitaxial growth is a process of profound fundamental importance as well as an avenue to realize nanostructures such as Ge/Si quantum dots (QDs), with appealing properties for applications in opto- and nanoelectronics. However, controlling the Ge/Si QD size, shape, and composition remains a major obstacle to their practical implementation. Here, Ge nanostructures on Si(111) were investigated in situ and in real-time by low energy electron microscopy (LEEM), enabling the observation of the transition from wetting layer formation to 3D island growth and decay. The island size, shape, and distribution depend strongly on the growth temperature. As the deposition temperature increases, the islands become larger and sparser, consistent with Brownian nucleation and capture dynamics. At 550°C, two distinct Ge/Si nanostructures are formed with bright and dark appearances that correspond to flat, atoll-like and tall, faceted islands, respectively. During annealing, the faceted islands increase in size at the expense of the flat ones, indicating that the faceted islands are thermodynamically more stable. In contrast, triangular islands with uniform morphology are obtained from deposition at 600°C, suggesting that the growth more closely follows the ideal shape. During annealing, the islands formed at 600°C initially show no change in morphology and size and then rupture simultaneously, signaling a homogeneous chemical potential of the islands. These observations reveal the role of dynamics and energetics in the evolution of Ge/Si QDs, which can serve as a step towards the precise control over the Ge nanostructure size, shape, composition, and distribution on Si(111).

Morphological features of nectaries of some species of the genus Rosa (Rosaceae)

Results are presented of our study of nectaries of 13 species of the genus Rosa from the collection of the M.M. Gryshko National Botanical Garden of the National Academy of Sciences of Ukraine. Using light microscopy, we described and illustrated their morphological features in details. Nectaries of all studied species were floral, hypanthial, symmetrical, non-septally structural, mesenchymatous, and persistent. Based on location of the androecium, nectaries were intrastaminal, and only Rosa henryi was found to have amphistaminal nectary. Each species was morphologically differentiated from others by one or more characters. We analyzed morphological features (diameter of nectary and throat of hypanthia, thickness of nectary tissue around throat of hypanthia and on the edge, form of nectary on the longitudinal section), on that basis we allocated groups of nectaries based on their shape – convex (cone- and dome-shaped), curved, and flat ones. The latter is typical for Rosa roxburghii, which, according to a number of other morphological features, is separated by taxonomists in a monotypic (monospecific) subgenus. Based on surface characteristics of the nectary, Rosa xanthina with papillary growns and Rosa henryi with a uniformly humped relief stood out the most examined species. We emphasized reduction of thickness of nectary tissue in radial direction, except for Rosa spinosissima, in which thickness was almost even throughout the whole area of the nectary. The listed morphological differences can be used as additional diagnostic characters at the species level. Such features as the outline of the nectary throat and edges are quite variable within species and were not taxonomically significant. We present original figures and photographs of nectaries in an outline and on a longitudinal section.

Wireless Electrical Power Delivery Using Light through Soft Skin Tissues under Misalignment and Deformation

AbstractProviding sustainable electrical power to medical electronic implants is key to enabling the diverse functions of implants and to avoiding repetitive replacement surgeries of depleted batteries. Subcutaneous photovoltaic energy harvesting with an external light source patch can be a reliable approach that provides sufficient power using light. However, from a practical perspective, aligning the external light source patch over opaque skin by patients may affect the amount of delivered electrical power. The amount of delivered power may also be affected by the deformation of the light source and receiver patches in accordance with thin skin layers. In this paper, an experimental and analytical study on the performance of a power implant under an animal skin depending on the implantation depth, lateral misalignment with the external light patch, and bending radius and direction is presented. The experimental results indicate that the transferred power by the patches in misalignment (about 20% of the transmitter length) or in bending (≈30 mm radius) is maintained at least 90% power of the aligned and flat ones. The results provide important characteristic data that are required in designing reliable wireless power transfer systems for various types of implantable medical devices.

Чернильница и финики: тема труда в выставках «Предметы гордости и стыда» и «Гастев. Как надо работать»

This article investigates labor through the interpretation of modern artistic practices. Two exhibitions have been chosen as examples. The first one is the exhibition of Vladimir Arkhipov's collection of folk things; the second one is “Gastev. How to Work'' dedicated to Alexey Gastev. The exhibitions were held at the PERMM Museum of Contemporary Art in 2021. The author conducts a comparative cross-temporal study of the results of labor and the labor process focusing on the phenomenon of a folk thing investigated by artist Vladimir Arkhipov for more than two decades and idealistic reference ideas of scientifically regulated labor norms and standards developed by Alexei Gastev and the Central Institute of Labor in the 1920s. The comparative study will rely on the paradigms of re-thinking the labor in the mid-20th and early 21st centuries by scientists such as A. Honneth, Z. Bauman, M. Heidegger, G. Standing, and H. Arendt and the contemporary philosophical research on the issue of ontologies, namely the flat ones, undertaken by B. Latour and T. Morton. The methods designed during the evolution of the theoretical representation and understanding of labor in the second half of the 19th century and at the end of the 20th century allow for tracing and exploring the path from the forced labor to the free one focusing on artistic practices. This comparison will refer to the analysis of labor as a process. Contemporary approaches in the field of ontology, namely the flat ontology, have been used as a methodology for analyzing the transformation of perceiving the labor outcomes. Both the labor process and its results have been analyzed along the trajectory of the subject-object relations. The paper proposes a definition of the perception and product of labor under the modern socio-economic and sociopolitical conditions through the prism of artistic ideas.

Исследование макроскопической локализации пластического течения в аддитивно изготовленном биметалле

The paper studies the kinetics of macroscopic localization of plastic deformation in a bimetal obtained by electron-beam surfacing of wire from low-carbon steel 09G2S on a substrate of St.3. Mechanical tests according to the scheme of uniaxial tension of flat ones were carried out at a constant rate at room temperature. The mechanical properties and stages of the plastic flow of the bimetal are compared with those of the starting materials. The kinetics of plastic deformation localization zones in different bimetal layers was studied by digital speckle photography.

Multifunctional roles of hairs and spines in old man of the Andes cactus: Droplet distant coalescence and mechanical strength

Cactaceae have adapted to harsh environments by resisting intense solar radiation, retaining and collecting water. Some cacti species have hairs on them along with distinctive spines to serve different functions. In this study, we characterized the Old Man of Andes cactus (Oreocereus trolli). We examined the surface morphology and estimated roughness and adhesion force of both spines and hairs. They both consist of longitudinal microgrooves. The condensation experiments carried out on spines showed that there is a particular phenomenon of distant coalescence (DC): smaller droplets flow totally or partially into larger ones through the microgrooves with consequent accumulation of water in a few large drops. An earlier study (Bintein et al., 2019) has shown that artificial micro-grooved surfaces that exhibit DC are more efficient than flat ones at collecting and sliding dew, and thus cactus spines could act as soil dew conveyors. The agreement between our analytical model and experimental data verifies that the flow is driven by the Laplace pressure difference between the drops. This allowed us to obtain a general criterion for predicting the total or partial emptying of the smaller drops as a function of the dynamic contact angles of a surface. With the Wilhelmy method, we determined that hairs are less hydrophilic than spines. We also estimated the mechanical properties of both the spines and hairs to evaluate their possible role in physical defense. This study aids in better understanding the physical attributes and the condensation interaction with microstructures, and suggests some functional roles.