Modular Surface Research Articles

Modeling and validation of impact forces for back‐calculation of pavement surface moduli

AbstractWhen an impact load is sufficiently small, its influence on the pavement structure is mainly from the surface layer material. To explore the influence depth of an impact load and back‐calculation of the pavement surface modulus, both numerical calculation and experimental testing were conducted, and the results are presented in this paper. The numerical calculation was performed through a DEM‐FDM‐coupled model. After a new modulus back‐calculation algorithm is formed by analyzing the numerical modeling results, experimental tests were also conducted for verification, and the results were analyzed. The max value of the falling weight impact force was closely related to the elastic modulus of the material, and the influence depth was controllable. Finally, it is proved that the method can be used to calculate the surface layer modulus and estimate the surface layer thickness.

Compact moduli of elliptic K3 surfaces

Compact moduli of elliptic K3 surfaces

Particle Size and Rheology of Silica Particle Networks at the Air-Water Interface.

Silica nanoparticles find utility in different roles within the commercial domain. They are either employed in bulk within pharmaceutical formulations or at interfaces in anti-coalescing agents. Thus, studying the particle attributes contributing to the characteristics of silica particle-laden interfaces is of interest. The present work highlights the impact of particle size (i.e., 250 nm vs. 1000 nm) on the rheological properties of interfacial networks formed by hydrophobically modified silica nanoparticles at the air-water interface. The particle surface properties were examined using mobility measurements, Langmuir trough studies, and interfacial rheology techniques. Optical microscopy imaging along with Langmuir trough studies revealed the microstructure associated with various surface pressures and corresponding surface coverages (ϕ). The 1000 nm silica particle networks gave rise to a higher surface pressure at the same coverage compared to 250 nm particles on account of the stronger attractive capillary interactions. Interfacial rheological characterization revealed that networks with 1000 nm particles possess higher surface modulus and yield stress in comparison to the network obtained with 250 nm particles at the same surface pressure. These findings highlight the effect of particle size on the rheological characteristics of particle-laden interfaces, which is of importance in determining the stability and flow response of formulations comprising particle-stabilized emulsions and foams.

Compact and modular autonomous surface vehicle for water research: The Naval Operating Research Drone Assessing Climate Change (NORDACC)

Research, monitoring, and management of marine and aquatic ecosystems often require surface water samples to measure biogeochemical and optical parameters. Traditional sampling with a boat and several personnel onboard can be labor-intensive and safety requirements limit sampling activities in high-risk environments. This paper describes the Naval Operating Research Drone Assessing Climate Change (NORDACC). NORDACC is an open source, light-weight, and portable autonomous surface vehicle that can acquire surface water samples while also measuring sea surface temperature and salinity for the duration of its deployment. NORDACC is ideal for operations in remote areas where resources and personnel are limited. Two sample bottles, each one liter in volume, can be filled, either at pre-programmed sampling stations or manually, using the remote control. A trimaran design provides buoyancy and stability, with hulls constructed of vacuum-formed acrylonitrile butadiene styrene (ABS) plastic. NORDACC can navigate autonomously between waypoints and features first person view capabilities for enhanced situational awareness. NORDACC’s performance was validated in Aarhus Bay, Denmark, collecting multiple surface water samples in winds in excess of 8 ms−1 and steep, choppy waves.

Optimizing structure of photovoltaic thermal solar air heaters with baffles and hole plates

Based on previous research, a mathematical model of photovoltaic thermal solar air heaters with baffles and hole plates (PVTSAH-B) was proposed to analyze the influence of the opening ratio on the flow and heat transfer characteristics of PVTSAH-B and to further improve its performance. The results showed that the air velocity and temperature distributions were affected by the opening ratio of hole plates. The vortex zones in PVTSAH-B could be broken by air jet flow when the opening ratio of hole plates was less than 0.4. The PV modular surface temperature and the area of the high-temperature zones decreased with the decreasing of the opening ratio of hole plates. Lowering the opening ratio of hole plates could increase the thermal and power efficiency. However, the fan energy consumption increased due to the decrease in the opening ratio of hole plates increasing the pressure loss. Therefore, the effective power efficiency decreased. 0.4 opening ratio of hole plates recorded the highest performance of PVTSAH-B. Meanwhile, the maximum values of the effective power efficiency, thermal efficiency and the total efficiency were 0.129, 0.567 and 0.696 respectively, which were 5.97%, 12.30% and 11.07%, higher than the opening ratio 1.0, respectively.

On the yield criterion of porous materials by the homogenization approach and Steigmann–Ogden surface model

In this work, we investigate the yield criterion of nanoporous materials by using homogenization approach and Steigmann–Ogden surface model. The representative volume element is proposed as an infinite matrix containing a tiny nanovoid. The matrix is incompressible, rigid-perfectly plastic, von Mises materials and nanovoids are dilute and equal in size. First, the constitutive of microscopic stress and microscopic strain rate is established based on the flow criterion. Secondly, according to the Hill’s lemma, the relationship between the macroscopic equivalent modulus and the microscopic equivalent modulus is established by homogenization approach. Thirdly, the macroscopic equivalent modulus containing the Steigmann–Ogden surface model including surface parameters, porosity and nanovoid radius is derived from the trial microscopic velocity field. Finally, an implicit macroscopic yield criterion for nanoporous materials is developed. For surface modulus, nanovoids radius and porosity studies are developed through extensive numerical experiments. The research results in this paper have reference significance for the design and manufacture of nanoporous materials.

Improving the Mechanical Properties and Tribological Behavior of Sulfobetaine Polyurethane Based on Hydrophobic Chains to Be Applied as Artificial Meniscus.

In the context of meniscus reconstruction in knee joints, current bulk biomaterials fail to meet the clinical demands for both excellent mechanical strength and low coefficient of friction. In this research, zwitterionic polyurethanes (PUs) with varying sulfobetaine (SB) groups were synthesized as the potential materials for artificial meniscus to investigate the relationship between the structures of SB groups and the performances of PUs. Under the saturation condition of 3 mg/mL hyaluronic acid aqueous solution, PU with long-alkyl chains and SB groups (PU-hSB4) exhibited a good tensile modulus (111.5 MPa) because the hydrophobic interaction of carbon chains was able to maintain the ordered aggregations of hard segment domains. Interestingly, hydrophobic chains in the molecular chain could also improve the tribological performance of PU-hSB4 instead of resulting from the surface roughness of samples, the components of lubricants, and the counterface of samples. A thicker and relatively stable hydration layer of noncrystal water was formed on the surface of PU-hSB4, which exhibited superior resistance to external forces compared to other PUs. Even if the hydration layer was damaged, PU-hSB4 was able to resist the compression of cartilage due to its high surface modulus, thus maintaining a similar and stable coefficient of friction (0.15-0.16) to native meniscus (0.18) and excellent wear resistance. In addition, the low cytotoxicity of PU-hSB4 further demonstrated its great potential to be applied in artificial meniscus instead.

Electrochemical and surface study of an antibiotic drug as sustainable corrosion inhibitor on mild steel in 0.5 M H2SO4

Corrosive degradation of mild steel using the antibiotic ethambutol hydrochloride drug as a sustainableinhibitor in 0.5 M sulphuric acid was studied and found as an efficient inhibitor. The inhibitive action showed an increase with an upsurge in the drug concentration, but with escalating temperature, inhibition efficiency declined. The drug showed a best of 92.78% inhibition efficiency at 1000 ppm and 313 K. The thermodynamic, kinetic and adsorption parameters were evaluated and established the physisorption of the drug over the metal surface following Langmuir adsorption isotherm. The EIS analysis confirmed the adsorption of inhibitor on the metal surface by showing the lowering in the value of double layer capacitance, Cdl; improvement in charge transfer resistance, Rct as the surface modulus raised. The mixed type of inhibition mechanism was confirmed by a Potentiodynamic polarization experiment. Surface morphology through Atomic Force Microscopy (AFM) validated the less deteriorated metal surface exposed to corrosive medium in presence of the drug.

Intersecting geodesics on the modular surface

Intersecting geodesics on the modular surface

Performance-Based Expressway Asphalt Pavement Structural Surface Layer Modulus Matching Mode Research

The current asphalt pavement design theory is a traditional line elastic theory. The voltage resistance recovery modulus is used as the material stiffness parameter in the design, which does not fully consider the significant differences between the road material pull-up modulus. Therefore, to improve the overall stress of the pavement structure, this article started from the perspective of the volume of the structure layer, analyzed the development characteristics of reflected cracks in terms of the modular volume of different surface layers, and studied the size of each layer. It is proposed to match the asphalt pavement layer modulus with the crack development level. Based on structural computing and simulation, the application of different modular matching modes was verified, and support was provided for the design of the pavement structure. The results showed that with the increase of the surface modulus, the stress intensity factor determined by a semi-analytical method showed a nonlinear decrease trend, and the change of stress intensity factor was not obvious when the modulus was greater than 10,000; the surface layer compression mode ratio increased, and the vertical deformation of the road surface and the top surface pressure of the road base slowly increased, especially when the volume of the pressure pull-up ratio was greater than 1.5. In addition, the impact of the constraint between the surface layer on the vertical deformation of the road table decreased with the decrease in the volume of the surface layer.

Appell series over finite fields and modular forms

In this article, we express the special values of F4⁎, a finite field analogue of the classical Appell series F4, in terms of the Fourier coefficients of weight three modular forms. These modular forms are related to modular K3 surfaces. To obtain these results, we first prove the finite field analogues of classical identities connecting classical F23-hypergeometric series and F4-Appell series.

Modulating pentenoate-functionalized hyaluronic acid hydrogel network properties for meniscal fibrochondrocyte mechanotransduction.

Knee meniscus tears are one of the most common musculoskeletal injuries. While meniscus replacements using allografts or biomaterial-based scaffolds are available, these treatments rarely result in integrated, functional tissue. Understanding mechanotransducive signaling cues that promote a meniscal cell regenerative phenotype is critical to developing therapies that promote tissue regeneration rather than fibrosis after injury. The purpose of this study was to develop a hyaluronic acid (HA) hydrogel system with tunable crosslinked network properties by modulating the degree of substitution (DoS) of reactive-ene groups to investigate mechanotransducive cues received by meniscal fibrochondrocytes (MFCs) from their microenvironment. A thiol-ene step-growth polymerization crosslinking mechanism was employed using pentenoate-functionalized hyaluronic acid (PHA) and dithiothreitol to achieve tunability of the chemical crosslinks and resulting network properties. Increased crosslink density, reduced swelling, and increased compressive modulus (60-1020 kPa) were observed with increasing DoS. Osmotic deswelling effects were apparent in PBS and DMEM+ compared to water; swelling ratios and compressive moduli were decreased in the ionic buffers. Frequency sweep studies showed storage and loss moduli of hydrogels at 1 Hz approach reported meniscus values and showed increasing viscous response with increasing DoS. The degradation rate increased with decreasing DoS. Lastly, modulating PHA hydrogel surface modulus resulted in control of MFC morphology, suggesting relatively soft hydrogels (E = 60 ± 35 kPa) promote more inner meniscus phenotype compared to rigid hydrogels (E = 610 ± 66 kPa). Overall, these results highlight the use of -ene DoS modulation in PHA hydrogels to tune crosslink density and physical properties to understand mechanotransduction mechanisms required to promote meniscus regeneration.

Surface elasticity and area incompressibility regulate fiber beading instability

A continuum body endowed with an energetic surface can exhibit different mechanical behavior than its bulk counterpart. Soft polymeric cylinders under surface effects become unstable and form surface undulations referred to as the elastic Plateau–Rayleigh (PR) instability, exclusively driven by competing surface and bulk properties. However, the impact of surface elasticity and area compressibility, along with bulk compressibility, on the PR instability of soft solids remains unexplored. Here we develop a theoretical, finite deformations framework to capture the onset of the PR instability in highly deformable solids with surface tension, surface elasticity, and surface compressibility, while retaining the compressibility of the bulk as a material parameter. In addition to the well-known elastocapillary number, surface compressibility and a dimensionless parameter related to the surface modulus are found to govern the instability behavior. The results of the theoretical framework are analyzed for an exhaustive list of bulk and surface parameters and loading scenarios, and it is found that increasing surface elasticity and surface incompressibility preclude PR instability. Theoretical results are compared with high-fidelity numerical simulation results from surface-enhanced isogeometric finite element analysis and an excellent agreement is observed across a broad range of material parameters and large deformation levels. Our results demonstrate how surface effects can be used to (i) render stable soft structures and prevent PR instability when it occurs as an unwanted by-product of manufacturing techniques or (ii) tune the instability behavior for possible applications involving polymer fibers.

Stable pair compactification of moduli of K3 surfaces of degree 2

Abstract We prove that the universal family of polarized K3 surfaces of degree 2 can be extended to a flat family of stable KSBA pairs ( X , ϵ ⁢ R ) (X,\epsilon R) over the toroidal compactification associated to the Coxeter fan. One-parameter degenerations of K3 surfaces in this family are described by integral-affine structures on a sphere with 24 singularities.

The influence of water vapor on the structural response of asphalt pavement

Abstract A series of water damage phenomena of asphalt pavement during service show that water is very important. To comprehensively analyze the influence of water vapor factors on the response of pavement structure, this article first tests the water vapor diffusion coefficient of asphalt pavement materials at different temperatures establishes the water vapor concentration field model of the pavement structure, and analyzes the actual water vapor distribution of the pavement structure; then, the relationship between viscoelastic parameters of the mixture and water vapor concentration is established. Based on this, the finite element model of the pavement structure considering the water vapor factor is established, and the influence of the water vapor factor on the pavement structure response and fatigue life is quantified. It is found that water vapor has an important influence on the mechanical response. On the hottest days in summer, the attenuation of surface modulus caused by water vapor has the greatest impact on the upper layer of the pavement structure. Under the influence of water vapor, the position just below the wheel of the upper layer at the bottom of the horizontal tension strain increases by 108.26%, and the horizontal tension strain of the other layers increases by about 5%, increasing the risk of upper layer cracking. At the same time, water vapor reduces the stress that can be borne by the surface layer, while the rest of the stress is borne by the base. Compared with the fatigue life calculation method in the specification, the actual non-uniform water vapor concentration field reduces the fatigue life of the surface layer by 12.246%. This shows that the current structural calculation does not consider the water vapor factor, which makes the pavement structure more dangerous, and the influence of the water vapor factor should be fully considered.

Surface properties of [formula omitted]m and sub-[formula omitted]m polydimethylsiloxane thin films after oxygen plasma treatment

Polydimethylsiloxane (PDMS) is widely used in many areas of science due to its outstanding properties. The continuous expansion of its applications is evidenced by a large number of research studies dedicated to modifying this soft material, ultimately leading to tailored properties. These studies highlighted the important role of film thickness (in the range of a few micrometers to millimeters) on surface properties, including mechanical properties, wettability, and surface topography. In this work, we investigated these surface properties of pristine as well as oxygen plasma-treated PDMS, in a thickness range of submicrometer and micrometer. We explored the effects of film thickness, dilution ratio, and plasma treatment time on effective Young’s modulus, surface topography (buckling structures), and wettability (hydrophobicity recovery) of the PDMS surfaces by conducting force–distance measurements, atomic force microscopy (AFM) and contact angle (CA) measurements, respectively, over a period of more than one month after the plasma treatment. The results of effective Young’s modulus on pristine PDMS show a high correlation with the dilution ratio and no dependency on the thickness. The characterized waviness (λ) and amplitude (A) of the resulting buckling structures forming on the plasma-treated surfaces reveal a correlation with film thickness, which is not included in the theoretical predictions. The results of CAs show a faster recovery process for the advancing than for the receding condition, and uncover a high correlation with both film thickness and dilution ratio for short-time plasma treatment. Furthermore, the buckling structures as well as the hydrophobicity recovery process in this work revealed a significantly different domain in comparison to the studies in literature, where these properties of PDMS membranes with a thickness ranging from a few micrometers to a few millimeters have been investigated.

Hippo/YAP1 inhibition by verteporfin attenuates osteophyte formation in a mouse surgical osteoarthritis model

Osteophyte is an outgrowth of cartilage formed at the margins of the affected joint through endochondral ossification-like processes, and is one of the most common radiographic features of osteoarthritis (OA) that has been used to define the stage of disease. Osteophyte has been regarded to adapt the joint to the altered biomechanics of OA patients, limits joint movement and represent a source of joint pain, however, the mechanism of osteophyte formation, the morphology characteristics and biomechanical properties of osteophyte cells are remained unclear. In the present study, we isolated osteophyte cells and chondrocytes from late-stage OA patients who underwent total knee replacement surgeries, by applying Atomic Force Microscopy (AFM), we identified osteophyte cells were in irregular shape with dendrites, shrunk cell body, smooth surface and high elastic modulus (23.3 ± 5.4 kPa) when compared with chondrocytes (6.5 ± 1.8 kPa). In addition, osteophyte cells showed higher proliferation ability and colony formation capacity than chondrocytes. Mechanistically, we identified YAP1, the core transcriptional factor of Hippo signaling pathway, was highly expressed in osteophyte cell both at protein and RNA levels. Inactivation of Hippo/YAP1 signaling pathway by Verteporfin is sufficient to inhibit osteophyte cell proliferation in vitro and attenuate osteophyte formation in vivo. In conclusion, the morphology characteristic and biomechanical property of osteophyte cells at single cell level are quite different from chondrocytes, although we could not exclude other regulatory mechanisms, our findings suggested that Hippo/YAP1 is of great importance for osteophyte formation.

Analysis of zirconia mechanical properties after application of a protocol to simulate clinical aging

In order to test the effects of hydrothermal and clinically related aging on zirconia, monolithic disc-shaped samples were milled, sintered and polished from two high translucency zirconia , 3 mol % (HT) and 5 mol % (XT). Samples were divided into three groups: non-aged: control (CT); hydrothermal aging (HA - autoclave aging for 12.5 h at 134 °C, 2 bar); in vitro clinically-related aging (CRA - chewing simulation for 1.2 million cycles followed by 50,000 thermocycles and acidic exposure in HCl, pH 1.2, for 15 h). Mechanical properties (flexural strength, fatigue, hardness and elastic modulus) were analyzed and compared using the analysis of variance (at a level of 5% significance). In vitro clinically-related aging significantly decreased fatigue strength of XT zirconia with no effects on HT zirconia. Surface hardness and elastic modulus were not affected (p = 0.591 and 0.392 respectively). Hydrothermal aging increased fatigue strength for both materials and decreased the surface hardness and modulus of HT zirconia (p ≤ 0.001). Hydrothermal aging and in vitro clinically-related aging have different effects on the mechanical properties of zirconia , when used to simulate five years of clinical service.

Face Turning of Single Crystal (111)Ge: Cutting Mechanics and Surface/Subsurface Characteristics

Abstract Single crystal Ge is a semiconductor that has broad applications, especially in manipulation of infrared light. Diamond machining enables the efficient production of surfaces with tolerances required by the optical industry. During machining of anisotropic single crystals, the cutting direction with respect to the in-plane lattice orientation plays a fundamental role in the final quality of the surface and subsurface. In this study, on-axis face turning experiments were performed on an undoped (111)Ge wafer to investigate the effects of crystal anisotropy and feedrate on the surface and subsurface conditions. Atomic force microscopy and scanning white light interferometry were used to characterize the presence of brittle fracture on the machined surfaces and to evaluate the resultant surface roughness. Raman spectroscopy was performed to evaluate the residual stresses and lattice disorder induced by the tool during machining. Nanoindentation with Berkovich and cube corner indenter tips was performed to evaluate elastic modulus, hardness, and fracture toughness of the machined surfaces and to study their variations with feedrate and cutting direction. Post-indentation studies of selected indentations were also performed to characterize the corresponding quasi-plasticity mechanisms. It was found that an increase of feedrate produced a rotation of the resultant force imparted by the tool indicating a shift from indentation-dominant to cutting-dominant behavior. Fracture increased with the feedrate and showed a higher propensity when the cutting direction belonged to the <112¯> family.

Poly(2-hydroxyethyl methacrylate) surface chemistry and modulus differentially modulate neutrophils and lens epithelial cells-possible implications in cellular responses to intraocular lenses.

During cataract surgery, diseased lenses in the eye are surgically removed and replaced with polymeric artificial intraocular lenses (IOLs). Patients can experience a complication called posterior capsular opacification (PCO) that is corrected through the removal of part of the posterior capsule using a neodymium: yttrium-aluminum-garnet (Nd-YAG) laser to restore the optical path. These interventions have increased costs and can damage the retina and the IOL. PCO develops when lens epithelial cells (LECs) proliferate, migrate, and undergo epithelial-to-mesenchymal transition. Neutrophils involved in the immune response triggered during implantation impact LEC behavior and produce damaging neutrophil extracellular traps (NETs). In this research, poly(2-hydroxyethyl methacrylate) (PHEMA) -based disks were synthesized with varying amounts of comonomer (HEMA with 0, 2, and 12 mol% MMA) and functionalized with carboxyl and amine groups, yielding nine different hydrogels. Material and chemical properties of the disks were characterized, and neutrophil-like HL60 cells and B3 LECs were incubated with the disks. HL60 cell behavior was more strongly influenced by chemical functionalization than by mechanical properties with increases in adherence and NET accumulation. Conversely, the behavior and viability of B3 LECs were more strongly influenced by mechanical properties with increases in cell adhesion and α-SMA expression with increasing compressive moduli. Interestingly, B3 LECs had decreased viability and increased α-SMA expression when cultured on PHEMA2 disks pretreated with isolated NETs. Critical to the understanding of PCO and its prevention are both surface chemistry and mechanics as well as the inflammatory response.