Slide Surface Research Articles

Seismic Fragility Reduction for Base Isolated RC Frame Buildings by Curved Surface Sliding Bearings with Over-Stroke Displacement Capacity

ABSTRACT Recently, experimental studies on failure conditions of buildings equipped with curved surface sliding isolators have shown that when no displacement restraining elements are employed and the concave plates feature a flat rim, the inner slider can run on the edge of the sliding surfaces producing lateral displacement larger than the nominal isolator capacity. The over-stroke displacement capacity reduces the probability of seismic collapse of code-conforming base-isolated buildings for earthquake stronger than the design one. In order to quantify the benefit of the over-stroke displacement capacity of double concave curved surface slider (DCCSS) bearings on the seismic fragility of base isolated buildings, four case studies of six-storey reinforced concrete framed structures, consisting of new constructions and retrofit of existing structures located in high and medium hazard seismic sites, have been investigated in this paper. In all cases, two configurations of the isolation system have been considered, with end-stop displacement or with over-stroke displacement capacity. The seismic performance of the buildings has been investigated by multi-stripe nonlinear time-history analysis. The results of the nonlinear dynamic analysis at the collapse limit state have been compared with nonlinear static analysis in terms of maximum displacement and corresponding base shear. Fragility curves highlight a higher safety margin against collapse for seismic intensities beyond the design limit state of the isolation system with over-stroke capacity.

A novel method for the isolation of single cells mimicking circulating tumour cells adhered on Smart Bio Surface slides by Laser Capture Microdissection.

In recent years, the importance of isolating single cells from blood circulation for several applications, such as non-invasive tumour diagnosis, the monitoring of minimal residual disease, and the analysis of circulating fetal cells for prenatal diagnosis, urged the need to set up innovative methods. For such applications, different methods were developed. All show some weaknesses, especially a limited sensitivity, and specificity. Here we present a new method for isolating a single or a limited number of cells adhered to SBS slides (Tethis S.p.a.) (a glass slide coated with Nanostructured Titanium Dioxide) by Laser Capture Microdissection (LCM) and subsequent Whole Genome Amplification. SBS slides have been shown to have an optimal performance in immobilizing circulating tumour cells (CTCs) from early breast cancer patients. In this work, we spiked cancer cells in blood samples to mimic CTCs. By defining laser parameters to cut intact samples, we were able to isolate genetically intact single cells. We demonstrate that SBS slides are optimally suited for isolating cells using LCM and that this method provides high-quality DNA, ideal for gene-specific assays such as PCR and Sanger sequencing for mutation analysis.

A Method Based on a Modified Fluorescence In Situ Hybridization (FISH) Approach for the Sensing of Staphylococcus aureus from Nasal Samples.

Staphylococcus aureus is a major source of bacteremia and develops several complications, causing high morbidity and mortality. Rapid identification and detection of these bacteria have become an important issue for biomedical applications. Herein, an optical method based on a modified fluorescence in situ hybridization (FISH) approach has been established using DNA hybridization technology for the swift detection of pathogenic S. aureus from clinical samples. The platform was constructed with single-stranded genomic DNA and microbial colony by directly immobilizing in agarose-polyvinyl alcohol (AG-PVA) hydrogel on the surface of a glass slide. The probe was based on an elongation factor encoding the tuf gene, which binds with equal affinity to single-stranded DNA targets as well as surface proteins on microbial cells. The probe was labeled with MFP488 fluorophore having excitation wavelength 501nm. The hybridization of the labeled probe with the target DNA and surface proteins was carried out under optimal FISH conditions, and the detection of bacteria was based on temporary field excitation of the labeled probe under a fluorescence microscope. Positive hybridization signals were detected by high fluorescence intensity. In comparison to genomic DNA, robust signals were observed with microbial cells, perhaps due to the moonlighting effect of the elongation factor Tu (Ef-Tu) expressed on the surface of bacterial cells. The applicability of the developed platform was tested on pediatric nasal samples, and results were verified with real-time qPCR. The designed platform is stable and sensitive, and after detailed optimization, a portable structure for on-site detection of pathogenic bacteria from clinical samples can be produced.

Evaluation of buoyant action of groundwater and surface water interaction on pit slope stability using hydrogeological-stratigraphic-structural assessment within the Kawere catchment of the Nsuta mine

ABSTRACT In open-pit mining operations where activities are conducted below water table or close to surface water bodies, the mine is potentially faced with dewatering and slope stability challenges. Appropriate evaluation of slope stability to obtain adequate slope safety factor has continuously been the centre of geotechnical research locally and internationally. This paper evaluates the influence of buoyant action propagated by groundwater and surface (GW-SW) interaction on pit slope designed in multi-layered fractured rock with complex hydrology using Hydrogeological-Stratigraphic-Structural Assessment (HSSA) at the Nsuta Manganese Mine in Ghana. LEM analyses of the Pit C-western slope estimated an overall factor of safety (FOS) of 1.1, probabilities of failure (POF) of 7.5% and the reliability index (RI) of 1.4 in the slope stress field. However, when the groundwater was introduced, the slope FOS was reduced to 0.13, POF of 100.0% and (RI) of 0.00 indicating failure. FEM numerical model points to the location of maximum shear strain and total displacement in the argillite zone within the rock mass. The FEM seepage analysis model estimated groundwater pore pressure data along the critical slide surfaces from the crest of the slope to the bottom of the rock slope ranging between 250 kPa and 4250 kPa with an average pore pressure of 2250 kPa within the pit slope. This proposed HSSA approach used in the study provides innovative insights into the percentage failure contribution of the individual lithologies to the overall combined lithological susceptibility of the slope under stress and groundwater failure mechanisms, pointing out Ru ratio in pit slope stability estimation as inadequate.

Enhancing the lubricity and wear resistance of shape-memory-polymer via titanium carbide-based MAX and MXene

Sliding surfaces not only consume an exceptional amount of energy to overcome friction but also cause premature failure of mechanical systems due to wear, leading them to be frequently replaced. Friction and wear are, therefore, major concerns from the viewpoints of energy consumption, cost, and the environment. Here we report for the first time the development of tribologically resilient and self-healing smart composites comprising shape-memory polyurethane (SMPU) as the model polymer matrix and titanium carbide-based MAX and MXene materials as fillers. The ball-on-disk tribological tests and 3D optical surface profilometry tests are performed to examine the coefficient of friction and wear. The introduction of layered MAX and MXene phase materials exceptionally reduces the friction of SMPU by 2–3 times and reduces its wear rate by 2–3 orders of magnitude, even at low filler concentrations of 0.25 wt%. In-depth wear track analysis, using Raman spectroscopy and EDAX elemental mapping, reveals the presence of MAX and MXene at the wear track, in addition to tribochemically formed TiO2, which contributes to the SMPU's lubricity and wear resistance. Furthermore, the developed materials reveal damage healing capability, which is not hindered by the reinforcement of MAX and MXene as well. The results suggest that by using these composites, not only the friction and wear but also the frequent replacement of sliding components can be minimized, which is crucial for cost-saving and environmentally sustainable technologies.

Study on the Position Determination Method of Landslide Sliding Surface Based on the Theory of Data Correlation and Information Fusion

Study on the Position Determination Method of Landslide Sliding Surface Based on the Theory of Data Correlation and Information Fusion

Sliding Mode Control with Time-Varying Sliding Surface for Linear Uncertain Impulsive Systems

Sliding Mode Control with Time-Varying Sliding Surface for Linear Uncertain Impulsive Systems

Data-driven semianalytical method for predicting equivalent thickness of flexible pipeline carcass

The carcass layer inside a flexible marine pipeline is a large-angle spiral structure with a complex cross-section. A carcass resists radial loads and prevents flexible pipelines from collapsing under extreme hydrostatic pressures. The accurate evaluation of the critical collapse pressure of a carcass under external pressure is crucial for the safe design of flexible pipelines. Because of the complex cross-section of the carcass, the internal surface of the carcass slides and contacts adjacent layers under external loads, which complicates the analysis. Therefore, the complex cross-section of the carcass is often simplified into a uniform section with a fixed thickness during analysis. In this study, parametric models of the carcass with different cross-sectional parameters were established, and the radial stiffness of the carcass under symmetric radial compression was calculated numerically. Next, the calculated equivalent radial stiffness was introduced into the analytical model to obtain geometric coefficients with different cross-sectional parameters. Finally, symbolic regression was used to derive a mathematical equation relating the equivalent thickness and critical cross-sectional parameters of the carcass. The results showed that the Minimum error in the buckling eigenvalue between the equivalent models and full carcass layer model was 6.2 %, the error in the critical collapse pressure was 14.5 %. Meanwhile, the influence of different parameters on the critical collapse pressure of the carcass was discussed.

An Infinite Slope Model Considering Unloading Joints for Spatial Evaluation of Coseismic Landslide Hazards Triggered by a Reverse Seismogenic Fault: A Case Study of the 2013 Lushan Earthquake

Coseismic landslides pose a significant threat to the sustainability of both the natural environment and the socioeconomic fabric of society. This escalation in earthquake frequency has driven a growing interest in regional-scale assessment techniques for these landslides. The widely adopted infinite slope model, introduced by Newmark, is commonly utilized to assess coseismic landslide hazards. However, this conventional model falls short of capturing the influence of rock mass structure on slope stability. A novel methodology was previously introduced, considering the roughness of potential slide surfaces on the inner slope, offering a fresh perspective on coseismic landslide hazard mapping. In this paper, the proposed method is recalibrated using new datasets from the 2013 Lushan earthquake. The datasets encompass geological units, peak ground acceleration (PGA), and a high-resolution digital elevation model (DEM), rasterized at a grid spacing of 30 m. They are integrated within an infinite slope model, employing Newmark’s permanent deformation analysis. This integration enables the estimation of coseismic displacement in each grid area resulting from the 2013 Lushan earthquake. To validate the model, the simulated displacements are compared with the inventory of landslides triggered by the Lushan earthquake, allowing the derivation of a confidence level function that correlates predicted displacement with the spatial variation of coseismic landslides. Ultimately, a hazard map of coseismic landslides is generated based on the values of the certainty factor. The analysis of the area under the curve is utilized to illustrate the improved effectiveness of the proposed method. Comparative studies with the 2014 Ludian earthquake reveal that the coseismic landslides triggered by the 2013 Lushan earthquake predominantly manifest as shallow rock falls and slides. Brittle coseismic fractures are often associated with reverse seismogenic faults, while complaint coseismic fractures are more prevalent in strike–slip seismogenic faults. The mapping procedure stands as a valuable tool for predicting seismic hazard zones, providing essential insights for decision-making in infrastructure development and post-earthquake construction endeavors.

FRACTURE ANALYSIS AND SHIELDING EFFECTS IN ADVANCED MATERIALS

Due to their ability to interconnect electrical and mechanical domains, piezoelectric materials are increasingly finding applications in advanced electromechanical systems. Notably, magneto-electric composites like BaTiO3-CoFe2O4 have emerged as vital materials for the next generation of devices. Exploring this realm is a complex and significant endeavor, demanding the attention of the scientific community and further research. Over recent decades, the scope of formulating and executing computational models for continuous media has substantially broadened, encompassing a diverse array of material properties and fields in computational models. This article centers on the utilization of asymptotic analysis as a mathematical tool for constructing approximate equations and assessing the relevance of various hypotheses. It delves into the utilization of the perturbation method, pioneered by Kagadiy T. S. and others, to tackle two-dimensional contact problems in electropelasticity, particularly in the context of materials with linear anisotropy. The extensive applicability of this asymptotic approach underscores its efficacy in simplifying intricate problems by breaking them down into a sequence of boundary problem resolutions grounded in the theory of potentials. The collaborative effort of the authors in this research underscores that employing the mentioned method opens up avenues for formulating pertinent boundary problems for the fundamental equations. This, in turn, allows for the representation of the initial electropelasticity problem as a superposition of more manageable boundary problems. While mechanical and electrical components can be treated separately, they still interact via boundary conditions. To conduct a numerical analysis, the article examines scenarios where one crack surface slides parallel to the crack front against another and selects relevant materials with known characteristics. Calculations reveal that, even in the absence of mechanical load, crack surfaces undergo relative sliding due to non-zero electrical or magnetic fields. The study of the shielding effect, which mitigates crack motion by altering magnetic field distribution, holds particular significance. This effect reduces the overall stress intensity factor and impedes crack propagation. Conducting such a comprehensive analysis is pivotal for comprehending and foretelling the strength and reliability of structural components composed of piezoelectric and piezomagnetic materials. It is imperative to conduct a thorough examination of the mechanisms governing their failure.

Effect of proteins on biocementation in construction materials

This study examines the effect of proteins on the binding property and microstructure of enzymatic-induced calcium carbonate precipitation (EICP) in cementitious environment. The protein modified precipitates generally demonstrated improved binding to a glass slide surface or cement paste surface compared to the control precipitate. A marked decrease in the amount and binding strength of the precipitates in the cementitious environment was observed due to a reduction in the urease enzyme activity. The protein modified precipitates exhibited noticeable improvement compared to the control precipitate in cementitious environment which could arise from the ability of the proteins to partially shield urease from the negative effect of high pH. The protein gel network formation due to the complexation between the proteins and Ca2+ provides nucleation sites for CaCO3 crystallization. The FTIR, SEM, TGA, and XRD results indicated that vaterite is the dominant polymorph in cementitious environment compared to calcite in deionized water.

Effect of oxygen flow on electrical and optical properties of ITO films synthesized by magnetron sputtering method

The tin-doped indium oxide thin films were synthesized by DC magnetron sputtering on the surface of polished silicon samples and glass slides in a mixed argon-oxygen atmosphere. The other deposition parameters: operating pressure, magnetron power and substrate rotation speed were kept constant. Thickness and density of thin films were measured by X-ray Reflectometry. The effects of oxygen flow rate and substrate temperature on the optical and electrical properties were investigated. The electrical properties (resistivity, Hall mobility and charge concentration) of the thin films were measured by the Van der Pauw method using the Hall effect. The minimum value of resistivity 0.52 × 10-3 Ohm·cm, and maximum charge mobility 28 cm2V-1s-1 was achieved at an oxygen proportional gas mixture of 2.6% (0.71 sccm). The transmission spectra of the films were measured in the wavelength range from 300 to 1100 nm. The transmittance of all films exceeds 75% in the visible and near-infrared spectral ranges. It was found that increasing the oxygen flow rate and heating of the substrate up to optimal value 150°C led to an increase in the crystallinity of the films and, consequently, to an increase in the Hall mobility and the transmittance.

State estimation and sliding-mode fault-tolerant control of a class of nonlinear systems with actuator faults under the event-triggered mechanism

The current work is an analytical study of the problem of state estimation and fault-tolerant control (FTC) based on dynamic event triggered mechanism (ETM) in the event of actuator fault for a class of nonlinear systems in a network environment. First, a state estimator module is designed in conjunction with the designed dynamic ETM, and an integral sliding surface (SS) is designed in the estimation space to obtain a variable time delay system after augmenting the system by combining the state estimator module and the SS. Second, the sufficient conditions that can make the augmented system stable under the ETM with H∞ performance index are obtained by the Lyapunov–Krasovskii function. The sufficient conditions are decoupled after the design of the sliding mode control (SMC) law that can stabilize the system, and the calculation of the state estimation gain matrix and the SMC gain matrix are obtained. Finally, the effectiveness of the method proposed in this study is verified with two simulation comparison experiments.

The Influence of Vertical Seismic Acceleration on the Triggering of Landslides Constrained by Bedding Faults under an Inertial Frame Reference: The Case of the Daguangbao (DGB) Landslide

The Daguangbao (DGB) landslide was the largest landslide that was triggered by the 2008 Wenchuan earthquake with a magnitude of Ms8.0. The sliding surface of this landslide was constrained on a bedding fault 400 m below the ground surface. Seismic records show that the landslide suffered not only from strong horizontal but also vertical ground shaking that was almost equal to the horizontal component. In this study, to reveal the landslide triggering mechanism of the DGB landslide, this study ignores the steep dipping tension fracture section and the leading edge-locking section of the trailing edge of the DGB landslide, and the geological model of the large optical package landslide is generalized into a block model with the bottom controlled slip soft zone as the interface. Based on the improved Newmark method that considers vertical ground motion, the three-way seismic acceleration data and the shear strength parameter of the sliding surface being taken as a variable are used to calculate the cumulative permanent displacement of the slider. Then, by considering the cumulative permanent displacement ratio of vertical seismic acceleration or not and the cumulative permanent displacement ratio value considering the inertial force as the index, the response characteristics of the cumulative permanent displacement of the block-to-vertical ground motion and inertial forces were analyzed. The results show that both the horizontal inertial force and the vertical acceleration significantly increased the permanent displacement. The permanent displacement is 4.9 cm when considering the vertical acceleration, whereas it is only 2.0 cm without taking this into account. The contribution of vertical acceleration is significantly enlarged (87.8–90.7%) by the decreasing of the internal friction angle of the slide surface, while it is less influenced (5–27.4%) by the cohesion. Compared with the lower shear strength parameter of the sliding surface, the contributions of vertical acceleration and inertial force to the permanent displacement are more obvious when the shear strength parameter of the sliding surface is higher. When ϕ > 18°, the D/D* is greater than 1, and the maximum D/D* reaches 7. The fast accumulation event of permanent displacement is triggered in the concentration stage of the seismic energy release. In the DGB landslide area, 50% of the energy is released within 30–50 s, as indicated by the acceleration peaks recorded at the nearest seismic station, Qingping station. It is assumed that the DGB landslide may be triggered at 30–50 s due to half of the seismic energy being released during that time span.

Sliding-mode fault-tolerant control of the six-rotor UAV with dead-zone-input under event-triggered mechanism

This paper investigates the problem of event-triggered mechanism(ETM)-based sliding-mode fault-tolerant control (FTC) for a six-rotor Unmanned Aerial Vehicle (UAV) with dead zone input (DZI) cases, considering potential actuator and sensor faults. Initially, a dynamic ETM is designed, followed by the development of a non-fragile observer utilizing this designed ETM. An integral sliding surface (SS) is then designed in the observation space, and the system is augmented and treated as a variable time delay system. Subsequently, sufficient conditions to ensure the stability of the augmented system with an H∞ performance index γ are obtained using the Lyapunov-Krasovskii function. Next, a sliding mode control (SMC) law is formulated to guide the sliding variables to the SS in finite time. Furthermore, sufficient conditions for ensuring system stability with an H∞ performance index γ are decoupled, and the calculation methods for the non-fragile observer gain matrix and the sliding mode gain matrix are obtained. Finally, to validate the effectiveness of the proposed method in this paper, simulation experiments are conducted.

Efficient and Controllable Preparation of Tridirectionally Anisotropic Sliding Surfaces Based on Spatial Light Modulator.

Realizing the efficient and controllable preparation of tridirectionally anisotropic sliding surfaces (TASSs) is extremely important. However, achieving efficient preparation of TASSs remains a great challenge. Using a spatial light modulator combined with an image feedback algorithm to adjust the femtosecond laser beam to multifocus array with a gradient intensity distribution is an efficient solution to achieve this target. Specifically, the two solutions of multifocus combination and focus intensity design are used to realize the efficient and controllable preparation of TASSs, and the structure and performance characterizations are carried out to prove the superiority of this method. It is believed that the proposal of this method can provide more inspiration for solving the high-efficiency processing problems of complex micro/nanostructures.

The Effect of Star Shaped Dimples on Sliding Surfaces under Hydrodynamic Lubrication

The Effect of Star Shaped Dimples on Sliding Surfaces under Hydrodynamic Lubrication

A novel RCA-based DNA sensor system for specific and quantitative detection of Klebsiella pneumonia

The timely detection of Klebsiella pneumoniae (K. pneumoniae) infection is of great importance for patient management and the prevention of nosocomial infections. In this study, we present the development of a novel detection assay that enables sensitive and specific identification of K. pneumoniae-encoded topoisomerase IV (K. pneumoniae Topo IV) using a DNA sensor system in combination with Rolling Circle Amplification (RCA) technology. The DNA sensor system was designed by immobilizing DNA hairpin substrates on RCA primers modified slide surface. This modular reacting mode enhances the adaptability and flexibility of the sensor, thereby improving its universality as a sensing platform. When K. pneumoniae is present, the active Topo IV triggers the cleavage-ligation of DNA hairpin substrates, followed by RCA and labeling with fluorescent probes. This results in the visualization of K. pneumoniae at the single-molecule level by the DNA sensor, compared to situations when there are no K. pneumoniae present. The reliability and sensitivity of the DNA sensor were verified using purified enzymes and bacterial extracts, which establishes the foundation for quantitative detection of clinical samples. Notably, the sensor's detection limit for K. pneumoniae extracts was found to be 70 colony-forming units (CFU)/µL, a range considered clinically relevant for infections. Moreover, the DNA sensor system exhibited high sensitivity and accuracy in detecting K. pneumoniae from clinical samples, suggesting its potential application in clinical settings for detecting pathogenic microbes beyond K. pneumoniae.

A New Fractional-Order Adaptive Sliding-Mode Approach for Fast Finite-Time Control of Human Knee Joint Orthosis with Unknown Dynamic

This study delves into the implementation of Fast Finite Time Fractional-Order Adaptive Sliding Mode Control (FFOASMC) for knee joint orthosis (KJO) in the presence of undisclosed dynamics. To achieve this, a novel approach introduces a Fractional-Order Sliding Surface (FOSS). In the context of limited knowledge regarding the dynamics of knee joint arthrosis, Fractional-Order Fast Adaptive Sliding Mode Control (FOFASMC) is devised. Its purpose is to ensure both finite-time stability and prompt convergence of the KJO’s state to the desired trajectory. This controller employs adaptive rules to estimate the enigmatic dynamic parameters of KJO. Through the application of the Lyapunov theorem, the attained finite-time stability of the closed loop is demonstrated. Simulation results effectively showcase the viability of these approaches and offer a comparative analysis against conventional integer-order sliding mode controllers.

Study of [Bmim]Cl/LiCl Co-Solvent Dissolution of Waste Wool

Waste wool was subjected to dissolution using an ionic liquid solvent, 1-butyl-3-methylimidazole chloride salt ([Bmim]Cl), with lithium chloride (LiCl) as an additive. This study’s objective was to examine the impact of LiCl on keratin’s solubility in [Bmim]Cl and characterise the structure and properties of keratin post-dissolution and regeneration. The results indicated that LiCl exhibits efficient solubility in [Bmim]Cl, enhancing keratin dissolution. Investigations employing Infrared, XRD and small-angle X-scattering spectroscopy, along with SDS-PAGE, demonstrated a degradation of the α-helical keratin structure during the dissolution process. This was accompanied by a reduction in molecular weight; however, keratin retained its protein nature. Atomic force microscopy (AFM) results revealed that keratin could proliferate on the slide surface or establish a continuous film. An integrative analysis suggested that wool protein macromolecules could be deconstructed by [Bmim]Cl and LiCl actions, inducing minor structural alterations in wool. This study proposes a groundwork for future research into keratin’s adsorption behaviour on textile materials, without significantly modifying the wool keratin structure or function.