Slip Layer Research Articles

Localization and Delocalization During Seismic Slip

AbstractThe thickness of a seismic slip layer controls style and rate of rupture propagation, frictional heating, weakening, and energy budget of earthquakes. Slip layer thickness changes dynamically with feedbacks between temperature rise, roughness, damage, and fluid pressurization. Natural faults have complex slip histories, ambiguating which layer thicknesses represent a record of seismic slip. The thickness of proven paleoseismic slip layers in nature are 1 mm–1 cm. Thicker slip layers do not get hot enough to retain coseismic frictional temperature anomalies and thereby prevent the detection of big earthquakes using current methods. We suggest that delocalization—the spontaneous increase in slipping layer thickness during slip—plays a role in coseismic healing and cause biases in the rock record of earthquakes. Recognizing the importance of feedbacks affecting slipping layer thickness is critical to understanding strength and stress variations during earthquakes and to correctly interpreting earthquake source parameters from exhumed faults.

Study on whitecapping dissipation process for wave modelling during tropical cyclones

The atmosphere-wave interaction is an important physical process during tropical cyclones. Understanding and modelling of this process are of great significance for the technical and functional design of coastal and harbor structures. At the high wind velocities of tropical cyclones, foams and sprays that are blown away from the sea form a slip layer between the atmosphere and the sea surface. This slip layer makes the atmosphere-wave interaction exhibit different characteristics compared with that at low wind velocities. The significant effect of this layer on the atmosphere is the reduction of aero-dynamical surface roughness, which has been used to improve the expression of the drag coefficient. On this basis, the effect of the slip layer on the sea surface is further explored in this study. The whitecap coverage may reach a low limit at high wind velocities, and a modified numerical method of whitcapping dissipation for the wave spectrum model is proposed based on the classic field observations of whitecaps. According to these observations, when developing waves appear, the variation characteristics of whitecap coverage are different from those of developed waves with low wind velocities. Thus, the critical friction velocity of wave states should be defined, which can be expressed by the threshold steepness of developed waves due to the negative correlation between wave age and wave steepness. The dissipation mode is then modified to gradually reach the limit with the increase of friction velocities, which is validated during 24 tropical cyclones measured with 26 buoys. The negative Bias of the default mode generally decreases with the increase of friction velocity, even reaching −0.8 m, while the Bias of the modified mode is mostly maintained between 0.2 m and −0.2 m.

Understanding the effect of physical aging on slip dynamics in soft-glassy materials using pure elongation flow

Slip over a solid surface is a very common occurrence in industrial scale transport and the processing of complex fluids. The knowledge of slip also plays a huge role in the correct estimation of rheological properties. In this work, we have studied the slip dynamics in a model soft-glassy material that exhibits physical aging, wherein the structure evolves gradually toward a more solid-like character via rearrangement of constituents. More precisely, we have investigated the impact of physical aging on slip associated with pure elongation flow of the material. We have allowed the sample to age over different waiting times, followed by the sample being deformed slowly in elongation mode by pulling the top plate to achieve a pure elongation flow. Normal force as a function of gap has been recorded during such pure elongation. These normal force–gap curves demonstrated a remarkable gap-waiting time superposition, manifesting the strong signature of self-similarity in the pure elongation flow of the soft-glassy system. We have adopted a slip layer model, which predicted these normal force–gap flow curves remarkably well. Such prediction also rendered slip layer thickness as a function of waiting time, using which we have explained the intriguing self-similar nature of normal force–gap dependence. Finally, we have established a relationship between the slip layer thickness and the age-dependent bulk rheological properties. We have provided a possible physical reasoning to explain this link between the physical aging-driven state of material and the slip dynamics.

Structural detachment influences the shale gas preservation in the Wufeng-Longmaxi Formation, Northern Guizhou Province

Abstract In order to reveal the restriction in shale gas enrichment of the Wufeng-Longmaxi Formation in the northern Guizhou province, the influence model of detachment layer was established through field geological investigation, core observation, logging, sample analysis, and geological background data. The response relationship between the detachment layer and the shale gas enrichment model in different structural formats was analyzed. The results show that the thickness of the Wufeng-Longmaxi Formation’s detachment layer is influenced by the conditions near the fault zones and mineralogical characteristics. The lithofacies of the detachment layer shows mainly a combination of clay-rich shale facies. This indicates that lithofacies type is one of the main factors influencing the variation in slip layer thickness. The detachment layer exhibits distinct well logging response characteristics and is influenced by nitrogen enrichment. The development of detachment fractures allows atmospheric nitrogen to infiltrate shale gas. It leads to poor gas saturation in the shale gas. In addition, the overall tectonic deformation in the northern Guizhou province was found to gradually intensify from Northwest to Southeast, and there were two tectonic models: a slot-shift tape transition belt and a spacer type deformation belt. The influence of decollements on shale gas preservation was barely found in the northern Guizhou province. It is mainly controlled by buried depth of the target layer, conditions of the cover layer, structural type, and deformation intensity.

Out-of-plane behavior of unreinforced masonry walls with horizontal slip layers in RC frames

In some cases, the infilled walls may be subjected to in-plane（IP） earthquake and out-of-plane(OOP) earthquake action due to the uncertainty of earthquake action and infills’ position. As a new type of unreinforced masonry(URM) walls with horizontal slip layers, it can effectively reduce the in-plane damage of infilled walls of reinforced concrete frames under an earthquake. However，the infill wall out-of-plane damage has a greater security threat than in-plane damage. In this study, a numerical study about the difference of OOP behavior of URM walls with/without horizontal sliding layers are analyzed, mainly including failure mode, bearing capacity, displacement capacity and stiffness. The spacing of horizontal slip layers, length of annectent reinforcing bars and the friction efficient between slip layer and masonry unit are chosen to investigate the differences of OOP mechanical behaviors. The results show that the horizontal sliding layers reduce the integrity of URM walls in reinforced concrete frames, causing the constraint of surrounding frame on infilled wall and the arching effect inside infilled wall become weaker, and OOP bearing capacity to drop. It is found that i) the annectent reinforcing bars is conducive to reducing the out-of-plane failure of the wall; 2)the smaller the slip layer spacing of the wall is, the more serious the damage of the infill wall under the out-of-plane load is, and the smaller the out-of-plane bearing capacity and the out-of-plane stiffness of the wall are; iii) the influence of the friction coefficient between slip layers and masonry unit on OOP mechanical behaviors is small. Finally, Chinese building design code is also selected to estimate the OOP bearing capacity of URM walls with horizontal sliding layers. The value of λcr is recommended to be greater than 1.0, and the value of λP is greater than 3.3. The spacing of the slip layer should be greater than 1 / 5 of the wall height, and the length of the annectent reinforcing bars should not be less than 1 / 5 of the infilled wall length.

Momentum transfer and foam production via breaking waves in hurricane conditions

Generated under hurricane conditions, a slip layer composed of foam, spray, bubble emulsion, etc. determines the behavior of surface drag with wind speed. This study estimates foam's contribution to this behavior. A logarithmic parametrization of surface drag is introduced, where the effective roughness length of the underlying surface is decomposed into three fractional roughness lengths. These correspond to the foam-free area (as determined by open-ocean data at low wind speeds and laboratory data at high wind speeds), which includes the effects of spray, bubble emulsion, etc., and ocean areas covered by whitecaps and streaks, each weighted by their respective coverage coefficients. A key concept of this approach is the use of well-established experimental bubble-size spectra produced by breaking surface waves to obtain the foam-produced effective roughness length. This method provides a fair correlation of the logarithmic parametrization of surface drag against wind speed with a wide class of experimental data. Additionally, this approach estimates the hurricane's potential intensity, demonstrating reasonable agreement with experimental findings.

Wheel slip ratio control considering time delay characteristic for electro-mechanical braking system

Electro-mechanical braking (EMB) system is a novel brake-by-wire (BBW) system which is the development direction of the electrification and intelligent vehicle braking system. However, as the EMB contains a mechanical transmission mechanism, there is an inevitable time delay in the braking process, which will cause problems of the wheel slip ratio control. To address this issue, this paper proposes a novel wheel slip ratio control system based on a hierarchical control framework, comprising a slip ratio control layer and a clamping force control layer. Firstly, an EMB actuator model considering the stiffness and damping characteristics of the ball screw is constructed and the correspondence between the model and the EMB object is verified. Subsequently, a model-based compensate active disturbance rejection control (MCADRC) algorithm based on the EMB actuator model is designed to compensate the uncertainty of the EMB and improve the tracking accuracy of the clamping force. Furthermore, the influence of time delay on slip ratio control is analyzed and a slip ratio controller considering time delay characteristic is developed to improve the slip ratio control quality. Finally, the HiL test results show that the proposed controller can effectively reduce the jitter of slip ratio by 1.2% and improve the response speed of slip ratio control 7.8%, which prove the real-time and effectiveness of the controller.

DIAGNOSIS OF THE DETERIORATION AND CONSERVATION OF BES POTTERY JAR FROM THE TOMB OF PETAH UMM UYA IN SAQQARA

The purpose of this study was the chemical characterization and conservation of the Bes pottery jar. Pottery jars were important in Egypt from prehistoric times until the end of late history; they had their ideological symbolism and important role in daily life. "Bes" jar is a kind of healing jar, which was known and spread during the end of the New Kingdom and Late Period of ancient Egypt. AutoCAD, digital microscope, and polarized microscope (PLM) were used to clarify the deterioration state of the pottery jar. The XRD method was used to investigate the mineralogical composition of the pottery jar. Besides, the pottery's internal morphology and chemical composition were studied using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). The examination revealed that the selected pottery jar exhibited numerous cracks, dust accumulation, salt crystallization, and black spots. PLM showed the presence of several minerals, such as calcite, quartz, biotite, and plagioclase. SEM-EDX analysis revealed high calcium oxide concentrations due to the use of calcium carbonate in the slip layer, besides chloride salts. XRD analysis indicated that quartz was the predominant mineral in all the samples. Additionally, calcite, diopside, anorthite, halite, and dolomite were also detected in varying proportions. The pottery jar underwent various treatments, including mechanical and chemical cleaning. In addition, dental gypsum and grog were used in the completion process. Furthermore, the paraloid B-72 was used to achieve the consolidation process.

Highly Concentrated Electrolyte Superlubricants Enhanced by Interfacial Water Competition Around Chemically Active MgO Additives.

The low concentration of water-based lubricants and the high chemical inertness of the additives involved are often regarded as basic norms in the design of liquid lubricants. Herein, a novel liquid superlubricant of an aqueous solution containing a relatively high concentration of salt, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), is reported for the first time, and the superlubricity stability and load-bearing capacity of the optimized system (MgO0.10/LiTFSI10) are effectively strengthened by the addition of only trace (0.10 wt %) water-chemically active MgO additives. It demonstrates higher applicable loads, lower COF (∼0.004), and stability relative to the base solution. Only a trace amount of MgO additive is needed for the superlubricity, which makes up for the cost and environmental deficiencies of LiTFSI10. The weak interaction region between free water and the outer-layer water of Li+ hydration shells becomes a possible ultralow shear resistance sliding interface; the Mg(OH)2 layer, generated by the reaction of MgO with water, further creates additional weakly interacting interfaces, leading to the formation of an asymmetric contact between the clusters/particles within the hydrodynamic film by moderating the competition between interfacial water and free water, thus achieving high load-bearing macroscopic superlubricity. This study deepens the contribution of electrolyte concentration to ionic hydration and superlubricity due to the low shear slip layer formed by interfacial water competition with water-activated solid additives, providing new insights into the next generation of high load-bearing water-based liquid superlubricity systems.

ANALYSIS AND RESTORATION OF GRECO-ROMAN POTTERY IN EGYPT

The research aims to identify features of the industry and assess the pottery damage through various examinations and analyses, such as examination by polarised microscope (PLM), examination by Scanning Electron Microscope with Energy Dispersive X-ray unit "SEM-EDX", analysis by X-ray diffraction powder XRD, and thermal analysis TGA. Archaeometric features of archaeological pottery were identified. The used clay is Nile Clay; the additives are sand, limestone powder, pottery powder (grog), and straw. The moulding technique is the hand and potter wheel technique. The surface treatment is a red wash and slip layer. The burning atmosphere is oxidising for the first and second pottery pieces and reducing for the third and fourth pottery pieces. The burning temperature is about 816°C for the first sample, 887°C for the second sample, 706°C for the third sample, and 651°C for the fourth sample. The texture is medium to coarse fabric for the first sample; the second sample fabric is fine; and the third and fourth samples have a coarse texture. The research proved that the pottery objects suffer from some different damage aspects such as fracture, loss of some parts, lack of strength, weakness, cracking, soil sediments, soot spots and black core, and salt crystallisation (chloride, sulphate, carbonate, and phosphate salts). The research proved the use of a mixture of distilled water, acetone, and ethyl alcohol at a ratio of 1:1:1, respectively, for removing clay soil deposits. EDTA is used to remove lime deposits. Nano-silica at a concentration of 0.5% is used to strengthen archaeological pottery by spraying. Paralloid B 82 dissolved in trichloroethylene at a concentration of 50% in assembling the pottery sherds; it is preferable to display it in the museum at a temperature of 20°C and a relative humidity of 55:60%.

Multi-analytical techniques for characterization of ancient Egyptian pottery objects from Cairo University excavations at Saqqara

Archaeological pottery shows various forms of deterioration and degradation. This research aims to determine the chemical composition and diagnose the damage manifestations of three pottery vessels from the archaeological site of Saqqara. The AutoCAD, digital microscope, X-ray diffraction, polarized microscope, portable X-ray fluorescence, and scanning electron microscopy are utilized to understand the preservation status of pottery vessels. According to the investigation’s findings, the chosen vessels had cracks, accumulated dirt, missing parts, peeling of the slip layer, and black deposits. The X-ray diffraction analysis showed that Albite, Anorthite, Wollastonite, Quartz, Calcite, and Hematite are the primary constituents of the vessels. However, the polarized microscope showed the plagioclase feldspar, indicating that the Nile clay is the source of the raw clay and that the temperature rose above 800 °C. Portable X-ray fluorescence and scanning electron microscopy revealed different concentrations of Si, Fe, and Ca, which are the main pottery components. In addition to the presence of high concentrations of chloride salts. There is no doubt that this will help to preserve the archaeological pottery in future studies.

A comparative study of structural and spectroscopic properties of three structurally similar mechanically bending organic single crystals – 2-Amino-3-nitro-5-halo (halo = Cl, Br, or I) pyridine

In recent years, scientists have been very interested in single crystals of monoaromatic compounds with mechanical softness, but they are hard to find. The present work reports a comparative study of structural, spectroscopic, and quantum chemical investigations of three structurally similar mechanically bending monoaromatic compounds, namely, 2-amino-3-nitro-5-chloro pyridine (I), 2-amino-3-nitro-5-bromo pyridine (II), and 2-amino-3-nitro-5-iodo pyridine (III). The mechanical responses of the three organic crystals studied here are very intriguing due to the similarity of their chemical structures, which only differ in the presence of halogen atoms (Cl, Br, and I) at the fifth position of the pyridine ring and are explained through examining intermolecular interaction energies from energy frameworks analysis, slip layer topology, and Hirshfeld surface analysis. The crystals of all the three feature one dimensional ribbons comprising alternating NaminoH⋯Onitro and NaminoH⋯Npyridine hydrogen bonds that form R22(12) and R22(8) dimeric rings, respectively. In (III), weak I⋯I interactions link the adjacent ribbons forming a two dimensional sheet. Layer-like structures are observed in all three crystals, with no significant interactions between the adjacent architectures (ribbons or sheets). Energy framework calculations are used for estimating the bending ability of the three compounds, with the three following the order Cl ≪ Br < I. The iterative electrostatic scheme coupled with the supermolecule approach (SM) at the DFT/CAM-B3LYP/aug-cc-pVTZ level is used to calculate the third-order nonlinear susceptibility (χ3) values in a simulated crystalline environment for the static case as well as two typical electric field frequency values, (λ = 1064 nm) and (λ = 532 nm). In addition, estimates of the topological studies (localized orbital locator and electron localization function) and reactivity characteristics (global reactivity parameters, molecular electrostatic potential, and Fukui function) are made for the compounds under investigation. Docking studies done using AutoDock software with a protein target (PDB ID: 6CM4) revealed that three compounds could be used to treat Alzheimer's disease.

Multi-layered turbulence structure of flow under free surface of open channel flow using velocity–vorticity correlation structure method

Turbulence near a free surface is of multi-layered nature and of fundamental significance in understanding vast marine and ocean processes. Direct numerical simulation of an open channel with the free surface modeled by a free-slip boundary is performed. Complex multi-layered turbulence (i.e., the blockage layer, the slip layer, and the Kolmogorov layer) under the free surface are first identified based on predefined anisotropy indices. Later on, statistical features of the anisotropic turbulence inside the three turbulence layers are presented. Most importantly, considering the drastic variation of both velocity and vorticity in near-surface layers, we revisit the complex multi-layered turbulence by the velocity–vorticity correlation structure (VVCS) method [Chen et al., J. Fluid Mech. 742, 291–307 (2014)]. It is found that the VVCS can physically depict evolution of the hairpin vortex inside the channel, including generation in the bottom wall region, expansion in the bulk flow, process of getting flattened in the blockage layer, and then distortion and breakdown in the slip layer and the Kolmogorov layer. Specifically, the correlation structures VVCS11 for streamwise velocity and streamwise vorticity reflect how the hairpin legs are spatially distributed, while the correlation structures VVCS13 for streamwise velocity and spanwise vorticity describe the evolution of the hairpin vortex head. In the end, a cradle-like structure model is proposed based on the VVCS results and the vortex ring collision model is introduced to improve the understanding of the multi-layered turbulence under free surface. Hopefully, this research can be of value in future turbulence modeling work on free surface flows.

Micro-foaming of plant protein based meat analogues for tailored textural properties

Meat-like foods based on plant protein sources are supposed to be a solution for a more sustainable sustenance of the world population while also having a great potential to reduce the impact on climate change. However, the transition from animal-based products to more climate-friendly alternatives can only be accomplished when consumers' acceptance of plant-based alternatives is high. This article introduces a novel micro-foaming process for texturized High-Moisture Meat Analogues (HMMA) conferring enhanced structural properties and a new way to tailor the mechanical, appearance and textural characteristics of such products. First, the impact of nitrogen injection and subsequent foaming on processing pressures, temperatures and mechanical energy were assessed using soy protein concentrate and injecting nitrogen fractions in a controlled manner in the range of 0 wt% to 0.3 wt% into the hot protein melt. Direct relationships between related extrusion parameters and properties of extruded HMMAs were established. Furthermore, optimized processing parameters for stable manufacturing conditions were identified. Secondly, so produced HMMA foams were systematically analyzed using colourimetry, texture analysis, X-ray micro-tomography (XRT) and by performing water and Preprint submitted to Innovative Food Science and Emerging Technologies June 17, 2023 oil absorption tests. These measurements revealed that perceived lightness, textural hardness, cohesiveness and overrun can be tailored by adapting the injected N2 concentrations provided that the gas holding capacity of the protein matrix is high enough. Moreover, the liquid absorption properties of the foamed HMMA were greatly optimized. XRT measurements showed that the porosity at the center of the extrudate strands was the highest. The largest porosity of 53% was achieved with 0.2 wt% N2 injection, whilst 0.3 wt% N2 lead to destructuration of the HMMA foam structure through limited gas dispersion and wall slip layer formation. The latter can, nonetheless, be improved by adapting the processing parameters. All in all, this novel extrusion microfoaming process opens new possibilities to enhance the structural properties of plant-based HMMA and ultimately, consumers’ acceptance.

Захист елементів двигунів транспортних засобів від окислення: технологічний аспект

Multi-component composite coatings based on refractory compounds with a low speed of diffuse interaction, are concerned in the article in order to increase the service life. A study was conducted to increase the heat resistance of working blades, in which a diffusion borosilicide coating was formed on their surface; on the surface of coating a layer of molybdenum disilicide with a thickness of 120 μm was applied using the slip method. Experiments showed that when the thickness (over 120 microns) of the layer of disilicide suspension was increased, its detachment from the borosilicate surface of the working blade was observed. It was found that the thickness of the MoSi2 layer should not exceed 120 microns. Based on the results of the test of borosilicinated blades with a layer of MoSi2, the combined coating at a temperature of 1,6000C works for 450 hours, which is one and a half times longer than the service life of samples with only a borosilicide coating. The slip layer made of MoSi2 is found to increase the service life of the borosilicide coating. A metallographic analysis of the samples was carried out, which proved that the multi-layered coating is a composition based on molybdenum disilicide, reinforced with refractory oxides. An X-ray phase analysis of the protective surface layer of the slip coating was carried out, which showed that after high-temperature treatment, in addition to molybdenum silicides, it contains a number of the following oxides: Zr SiO4, HfSiO4, YAlO3, Y4Al2 O 3. According to the study, organic compounds of one- and two-component additives, introduced into the saturating mixture, ensure the formation of a borosilicide coating on refractory metals with a certain arrangement of boride and silicide layers and an adjustable structure of the silicide layer. Therefore, in aggregate, these factors contribute to increasing the service life of the protective diffuse coating.

A Cross-Scale Framework for Modelling Chloride Ions Diffusion in C-S-H: Combined Effects of Slip, Electric Double Layer and Ion Correlation.

Water and chloride ions within pores of cementitious materials plays a crucial role in the damage processes of cement pastes, particularly in the binding material comprising calcium-silicate-hydrates (C-S-H). The migration mechanism of water and chloride ions restricted in C-S-H nanopores is complicated due to the presence of interfacial effects. The special mechanical properties of the solid-liquid interface determine the importance of boundary slip and Electric Double Layer (EDL) and ion diversity in pore solutions determines the difference of the EDL and the stability of water film slip. A cross-scale model covering slip effects, time-varying of EDL and ion correlation needs to be developed so that the interfacial effects concentrated at the pore scale can be extended to affect the overall diffusivity of C-S-H. The statistics of pore size distribution and fractal dimension were used to quantitatively compare the similarities between model and C-S-H structure, thus proving the reliability of cross-scale reconstructed C-S-H transmission model. The results show that the slip effect is the dominant factor affecting the diffusion ability of C-S-H, the contribution of the slip effect is up to 60% and the contribution rate of EDL time-varying only up to about 15%. Moreover, the slip effect is sensitive to both ion correlation and C-S-H inhomogeneity and EDL time-varying is almost insensitive to ion correlation changes. This quantification provides a necessary benchmark for understanding the destructiveness of cement-based materials in the salt rich environment and provides new insights into improving the durability of concrete by changing the solid-liquid interface on the micro-nanoscale.

Dynamic behavior of a magnetorheological fluid radial-flow-based energy absorber considering apparent slip boundary condition

Accurate theoretical models play a key role in the development of magnetorheological energy absorbers (MREAs). Traditionally, the apparent slip caused by non-uniformity interface (i.e., the separation of carrier fluid and magnetic particles at the wall) of the working medium is often ignored for simplifying theoretical models. However, the apparent slip influence the cross-sectional flow and decreased the theoretical accuracy of the damping force for MREA applied in the impact absorption area. In this study, a dynamic model with apparent slip boundary condition for radial-flow-based MREA was proposed. The effect of apparent slip layer thickness on the dynamic behavior of an MREA was qualitatively and quantitatively compared in terms of the following three aspects: (1) with the Power-Law constitutive model, theoretical models of the dynamic characteristics of the magnetorheological fluid (MRF) squeeze and MREA are presented based on the apparent slip boundary condition with the MRF behavior of the Navier–Stokes equation; (2) the accuracy of the theoretical model to predict MREA peak force and boundary velocity with different slip-layer thicknesses; and (3) global agreement of the dynamic force and range curves between the modeling and experimental results. The results show that the absolute values of the relative errors in the two models with a 2- and 0-µm thick slip layer were less than 3.73 and 7.41%, respectively, and that a 2-µm thickness can help predict the actual dynamic characteristic more efficiently under accidental collision loading conditions.

Stable low‐friction carbon/epoxy composites using carbon nanocages stuffed with ionic liquids as fillers

AbstractEpoxy resin (EP) is prone to brittle fracture during friction due to internal stress after curing, resulting in fatigue wear and cracking. Adding carbon fillers is considered as one of the great potential solutions to solve the serious dry wear of EP. Herein, we develop a novel carbon capsule composite filler (CNC‐IL) filled with ionic liquid (IL) in carbon nanocages (CNC) using the vacuum principle to address these concerns. Compared with pure EP, the friction coefficient (0.10) and wear rate (1.712 × 10−6 mm3 Nm−1) of the optimized CNC‐IL/EP were reduced by 74.62% and 88.14%, respectively. Such excellent tribological properties can be attributed to the solid–liquid lubricating film formed by the IL released from the broken CNC during friction. A low‐shear‐resistance slip layer can be formed between the CNC‐IL in the film due to the repulsion of the isoelectric ions adsorbed on the surface of the CNC; it effectively integrates the self‐lubricating functions of CNC and the liquid lubrication functions of ILs. This work provides a valuable idea for designing C/EP composites with good antifriction properties.

On the wall boundary condition for the velocity in concentrated suspensions

Continuum models for concentrated suspension have succeedded in reproducing most features of channel flows, except for volume-fraction profiles in the vicinity of the walls. It has been stipulated that this could be traced to the choice of the no-slip boundary condition for the velocity of the granular phase, which conflicts experiments indicating the existence of a slip layer. In fact, particle migration is inhibited in the absence of sufficient slip and, therefore, numerical simulations tend to overestimate the volume fraction. In this paper, we explore whether apparent slip and true slip boundary conditions can mitigate those discrepancies. Our study suggests that when adequate slip is prescribed at the wall, the numerical predictions can match the experimentally observed values near the walls. However, there is a complex correlation between required slip and the average concentration; this is in line with recent experimental measurements of the near-wall slip in concentrated suspension • The role of the velocity boundary condition and the near-wall volume fraction profile is investigated numerically. • Higher slip at the wall improves the near-wall volume fraction profile predictions. • Existing correlations for the slip coefficient need to be revised.

Structural Characteristics and Deformation Evolution of an Intra-Continental Fold-Thrust Belt in Eastern Sichuan: Insights Into Analogue Sandbox Models

The Eastern Sichuan area is a typical fold-and-impulse zone. It is bounded by the Qiyue Mountain fault, with septal folds on the east and on the west. Based on previous geological mapping and surface geological structure research as well as the fault-related folding theory, in this study, tectonophysical simulation experiments were conducted to investigate the tectonic geometry and kinematics of the Eastern Sichuan fold-impulse zone. The experiments were conducted by selecting different experimental materials and changing the physical properties of the cover, the friction between the cover and the basement, the number of slip layers, the burial depth, and other factors. Finally, the similarity of the results to the morphological characteristics of the real geological structure was assessed. The results show that the deformation style is influenced to some extent by the brittle shear strength and the ductile shear strength of the basement, and the different interlayer cohesions between the competent and incompetent layers, the high rheology, and the burial depth of the slickensides played crucial roles in the formation of the final evolution of the Eastern Sichuan fold fault zone. The step-like system, composed of a lower crustal crystalline basement detachment surface, regional boundary fractures, and the overlying Cambrian and Triassic synclines, is a necessary condition for the formation of the Eastern Sichuan fold and fault zone and controls the overall evolution of the zone. Under the action of multiple phases of tectonic activity with different main stress orientations, the geological phenomenon of multiple superimposed phases of folding in different directions observed at present in the Eastern Sichuan area was formed. The well-developed karst features are not conducive to the construction of a project tunnel in the area where tightly closed back-slope, fissures, and normal faults have developed in the Eastern Sichuan fold and fault zone.