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Purpose This study aims to improve the tribological performance of Babbitt alloy under oil lubricant condition. Thus, the surface was treated into oleophobic state by modifying with low surface energy fluorosilane (1H,1H,2H,2H-perfluorodecyltriethoxysilane). It is believed that the oleophobic surface offered excellent wear resistance of Babbitt-based tribo-pairs. Design/methodology/approach By modifying the Babbitt alloy with low surface energy fluorosilane and measuring the oil contact angle, the wetting behavior was evaluated. Using Pin on Disk tribometer, the tribological properties of bare Babbitt and modified Babbitt were quantified. The samples after the friction test were characterized by scanning electron microscope (SEM) and the anti-wear performance was evaluated under dry and oil lubrication conditions. Findings Results showed that oil contact angle of modified Babbitt was109° which was tripled compared to that of prime surface, which indicates the oleophobic behavior was greatly improved. Under dry conditions, the friction coefficient of the modified surface with different load conditions is slightly lower than that of the bare surface, while the friction coefficient of the modified surface under lubrication conditions is significantly decreased compared to that of the bare surface. Interestingly, under low load and high load, the wear rate of the modified Babbitt alloy surface is only 1/4 and 1/3 of that of the bare surface, respectively. Originality/value The work proposed an effective method to improve the Babbitt tribological performances and will lighten future ideas for the Babbitt alloy bearing with high wear resistance, which is beneficial to improve the service life of sliding bearings and has huge promotion and application value in the manufacture of sliding bearings.

Infections caused by antibiotic-resistant bacteria are globally a major threat, leading to high mortality rates and increased economic burden. Novel treatment strategies are therefore urgently needed by healthcare providers to protect people. Biomaterials that have inherent antibacterial properties and do not require the use of antibiotics present an attractive and feasible avenue to achieve this goal. Herein, we demonstrate the effect of a new class of cationic hydrogels based on amino-functional hyperbranched dendritic–linear–dendritic copolymers (HBDLDs) exhibiting excellent antimicrobial activity toward a wide range of clinical Gram-positive and Gram-negative bacteria, including drug-resistant strains isolated from wounds. Intriguingly, the hydrogels can induce the expression of the antimicrobial peptides RNase 7 and psoriasin, promoting host-mediated bacterial killing in human keratinocytes (HaCaT). Moreover, treatment with the hydrogels decreased the proinflammatory cytokine IL-1β, reactive nitrogen species (NO), and mitochondrial reactive oxygen species (ROS) in S. aureus-infected HaCaT cells, conjunctively resulting in reduced inflammation.

Magnetic carbon nanotube (marked as “MWCNT@Fe3O4”) has been prepared by depositing magnetic Fe3O4 on carbon nanotube. In order to align MWCNT@Fe3O4 in polyimide (PI) film, weak magnetic field by permanent magnet has been applied during the film curing process. The orientation mechanism of MWCNT@Fe3O4 between the magnetic carbon nanotubes and the PI film matrix has been theoretically studied. Experimental results showed that MWCNT@Fe3O4 was formed in a chain-like alignment in the PI film matrix by the magnetic field, which significantly improved the dielectric properties of composite films. The dielectric permittivity of parallel-aligned films (1.6 wt%) was increased from 5.5 to 52.75 at 58 Hz and percolation threshold of 1.6 wt% was almost 6 times that of the film in random alignment. The dielectric loss of the aligned films before reaching the percolation threshold was between 10–2 and 1. The magnetic alignment can greatly enhance the dielectric permittivity of composite films and suppress their dielectric loss. As for magnetic properties, the relationship between different arrangements and saturation magnetization is as follows: randomly aligned > parallel aligned. PI(//)-0.4wt% film shows the best tensile strength of 70 MPa, 5% elongation at break improvement, and 23% improvement in elastic modulus. This study provides an effective method to align MWCNT in PI film matrix, and the MWCNT@Fe3O4/PI composite film has a promising application prospect in flexible electronic devices.

Microalgae, the primary producers in water ecosystems, are the main food of fish and shrimp. Microalgae have a great capacity to absorb heavy metals, and low concentrations of heavy metals can promote the growth of them. But high concentrations have a strong influence on the physiological and biochemical processes in algae, such as growth, photosynthesis, cell ultrastructure, protein content and fatty acid composition. Heavy metals may also induce the formation of reactive oxygen species (ROS), which causes the oxidation damage of protein, lipid and thiol peptides, and activates the antioxidant system. Heavy metals can be removed or converted into another state by biosorption of cell surface, accumulation in cells, combining with antioxidant enzymes and so on. This review summarized the responses of microalgae to heavy metals and comprehensively described the removal and tolerance mechanisms by extracellular adsorption and intracellular accumulation, which are helpful to treat pollution and improve the culture of microalgae.

MoSe2 nanoparticles were successfully synthesized by hydrothermal method and treated with a novel dispersion method, ultrasonic dispersion in water. The tribological behaviors and wear mechanisms of MoSe2 nanoparticles as oil additives were investigated using a reciprocating ball-on-disk tribo-meter. The results showed that the average friction coefficient and wear rate decreased by 43% and 87% respectively with the addition of the treated MoSe2 nanoparticles compared with white oil. The lubrication mechanism was investigated and can be interpreted as that the MoSe2 had smaller particle size after being ultrasonically dispersed in water, which were beneficial to the formation of the tribo-film.

Agarose hydrogel as an efficient carrier for protein model has been considered to optimize the lubrication of artificial hip joints. Elevating the effectiveness of lubricant to reduce frictional coefficient and wear debris to prolong life time of prosthesis is a main goal. Various biological solvents, such as sodium chloride (NaCl) solution, simulated body fluid (SBF), phosphate buffer solution (PBS) and deionized water, have been investigated to achieve the best structure for polymeric network during the hydrogel preparation process. Results proof that SBF is able to provide sustained release with 38% reduction rate of frictional coefficient to demonstrate sufficient strength of the polymer chains. Novelty of the present work is focusing on the anti-friction performance of hydrogel protein delivery system designed for medical or pharmaceutical applications.

In the paper, a distributed sensor fault detection and isolation scheme is presented for a network of second-order integrators. A new distributed control law is developed to achieve formation of the system. By using the integration information of distributed formation errors, the control law improves the robustness of the formation. A distributed observer is then designed in each vehicle based on the closed-loop dynamic model of the vehicle. Each vehicle updates the states of the distributed observer by employing the measurements of itself and the transmitted state estimations from its neighbors. Based on the distributed observer, a distributed fault detection observer and a distributed fault isolation observer are designed. The presented distributed fault detection observer in each vehicle is able to be sensitive to the faults of all vehicles in the system. By using the distributed fault isolation observers, each vehicle is able to be sensitive to the faults of itself, its neighbors and its neighbors’ neighbors and to be robust to the faults of other vehicles. Although the fault isolation of the proposed scheme is simple, computation loads of the scheme are lower than the current ones since only the model of the individual vehicle is used. Finally, the effectiveness of the control law and the fault diagnosis scheme is demonstrated by simulations and real-time experiments carried out based on a formation of three quadrotors.

This paper optimizes the coverage of circular micro-textures on bearing sliders aiming at improving their tribological performance. Grid-like array of textures are arranged to present or absent, which are respectively marked as 1 and 0. Genetic Algorithm is used to evolve the coverages of textures. The algorithm allows the derivation of preferable area for texture coverage in shape of pyramid at the inlet of slider. Evaluation of influences of convergence ratio and width demonstrates that sliders with small convergence ratio and width tend to result in significant tribological improvement effect. Subsequent experimental tests confirmed the achievement of low friction coefficient of the so optimized texture coverage.

A layer-by-layer deposition technique with grafting chitosan on the Co-Cr-Mo alloy was developed. The performance of tribology and biocompatibility were investigated under simulated conditions. Wettability of coating surface was super hydrophilic and the surface was in positive charge under the neutral solution, which was favored in water-based lubricating and adhesion of cells. By pin-on-disk tests, the chitosan coating surface exhibited lower friction coefficient under various sliding speed as compared with the uncoated substratum. A wear rate of 1.1 × 10−7mm3/Nm was detected, which was only one seventh of uncoated surfaces. Hypothetically illuminating the mechanism of antifriction is able to lead for better wear resistance. Co-culturing with osteoblast cells showed that coating had good benefits in the proliferation of osteoblast cells.

Multi-drug delivery systems constructed from a basic polymeric scaffold, and which have the ability to target a variety of biomedical applications, can streamline the development of nanomedicine to provide both environmental and economical relief. Herein, amphiphilic ABA-triblock copolymers are synthesized and assembled sequentially into micelles and nanogels as drug delivery systems following a thorough evaluation on advanced in vitro models to explore their potential for the treatment of cancer and bacterial infections. Short blocks of 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one (MAC) are oligomerized from PEG6k and thereafter functionalized with dihydroxyphenylalanine (dopa)-functional thiols using thiol-ene coupling (TEC) click chemistry. The copolymers self-assemble into well-defined micelles in aqueous solution and are further formulated into nanogels via UV-induced TEC. The resulting spherical micelles and nanogels are stable nanoparticles, with sizes ranging between 100 and 200 nm. The nanogels are found to be non-toxic to a panel of cell lines and mask the toxicity of the potent drugs until their release. The nanogels would be superior to micelles for the elimination of cancer cells supported by both 2D cell culture and a 3D spheroid model. The opposite conclusion could be drawn for bacteria inhibition.

In the paper, a new local-model-based distributed fault diagnosis (LMDFD) scheme is proposed for multi-agent systems subject to actuator faults. The proposed LMDFD scheme consists of a distributed fault detection (DFD) unit and a distributed fault isolation (DFI) unit. A distributed fault detection residual generator (DFDRG) and a bank of distributed fault isolation residual generators (DFIRGs) are developed in each agent based on the closed-loop model of both the agent and neighbors of the agent. Each agent updates states of its DFDRG and DFIRGs by using information of itself, its neighbors, and the delayed information of its neighbors’ neighbors. Moreover, adaptive fault detection and isolation thresholds are designed to deal with bounded disturbances induced by the delayed information. Based on the adaptive thresholds and the residuals of DFDRG and DFIRGs, the DFD and DFI logic are designed for each agent, respectively. Simulation results demonstrate the effectiveness of the proposed LMDFD scheme.

Surface texturing is one of the effective strategies to improve bioactivity of implantable materials. In this study, hierarchical micro and nano structure (HMN) were fabricated on Co-Cr-Mo alloy substrate by a movable picosecond laser irradiation. Respectively, microgrooves with nano ripples and islands were produced on Co-Cr-Mo alloy by low and high laser power density. X-ray diffraction apparatus (XRD) phase analysis illustrated that substrate was in the phase of γ- face-centered cubic structure (FCC) before laser treatment, while it was in ε-hexagonal closest packing structure (HCP) phase dominant after laser treatment. Cell adhesion and proliferation studies showed that the HMN surface exhibits enhanced adhesion of MC3TC-E1 osteoblast and promoted cell activity. Analyzing of the morphology of osteoblast cells indicated cells were in high ratio of elongation on the HMN surface, while they mainly kept in round shape on the polished surface. Results indicated the formation of hierarchical structure on Co-Cr-Mo alloy was able to improve biological performances, suggesting the potential application in cobalt based orthopedic implants.

Marine equipment and ships operating in complex environments face high drag consumption and severe surface fouling. Non-smooth biomimetic surfaces with specific microstructures work to reduce surface drag and inhibit fouling. In this work, the biological sharkskin shield scale structure was simplified by the idea of segmented independence to construct a bionic non-smooth surface. Single-crystal lithography was used to create a negative template of the silicon substrate. We created a non-smooth bionic structure on the flexible polydimethylsiloxane (PDMS) surface through die casting and molding. Additionally, the bionic non-smooth surface was modified by decorating zeolitic imidazolate framework-67 (ZIF-67) particles to modulate the antifouling properties. Based on tests performed on a self-designed and processed circulating water bath laboratory bench (CWBLB), results showed the non-smooth surface effectively reduced drag by 7.3% compared to that of smooth surface. The contact angle (CA) measurement and anti-bio-adhesion experiment on the surface showed that PDMS surface CAs increased from 109.78° to 140.71°, and Chlorella vulgaris attachment was decreased by 65.3%. The non-smooth bionic surface effectively reduces drag and antifouling, and the effectiveness of the antifouling can be significantly enhanced by augmenting and regulating the particle surface modification method. Our results provide a feasible solution for ship drag reduction and antifouling, which is critical for industrial applications and sustainable development.

Sustained release of the Bovine serum albumin (BSA) from agarose hydrogel has been suggested to decrease the frictional coefficient of hip implants. Hydrogel network formed with biological solvents such as simulated body fluid (SBF), sodium chloride (NaCl) and phosphate buffer solutions (PBS). Mechanical and rheological properties of hydrogel have been enhanced for injecting in load bearing area of the hip. Experimental evidences illustrated, hydrogel with PBS solvent produced stiffer network with slower deformation rate under heat and load. Cumulative released of lubricants have been moderated with regular and well-shaped pore structure to successfully reduce average of frictional coefficient with 47% reduction rate. Novelty of the present work provides an important candidate for the sustained biomedical material and pharmaceutical applications.

This paper considers the problem of distributed formation control for a second-order multi-agent system with a directed communication topology and constant communication time delays. A distributed proportion–integration–derivation (DPID) formation control law is proposed for the multi-agent system by introducing the integration information of the formation errors. A delay-independent condition and two delay-dependent conditions on the asymptotical formation stability are respectively presented under the assumption of the communication topology containing a directed spanning tree. Based on the Nyquist stability criterion, the range of the feasible time delays for asymptotical formation stability is obtained by analyzing the relationship between the Nyquist curves and the unit circle. Finally, simulations illustrate the effectiveness of the theoretical results.

In this paper, we study the crystal structures, density of states, electronic band structures and thermoelectric transport properties of SrCuChF (Ch = S, Se and Te) by the way of the first principle. The pictures of electronic band structure show the relatively large dispersion near the maximum value of valence band in the directions of Γ-M and Γ-X, but in the direction of Γ-Z, the band structure is relatively flat, and the top of valence band is mainly composed of Cu-Ch anti-bond state which has a very significant impact on the transport performance of p-type SrCuChF. Base on the semiclassical Boltzmann transport theory, we find that the p-type SrCuChF has a high value of Seebeck coefficient due to the quasi-flat character of the electronic bands at the edges of the valence band, and the outstanding anisotropic properties due to their natural layered structure. According to the predicted maximum value of power factors, the optimal doping concentration is presented. Therefore, we give a natural layered structure complex SrCuChF with the good thermoelectric properties and may find many important applications in the thermoelectric functional materials.

Heavy metals have caused widespread concern due to their adverse effects on aquatic organisms. However, there are few studies on their tolerance mechanism. In this study, the tolerance mechanisms of Cyclotella sp. to Cr(VI) were explored. The increase of antioxidant enzymes activity acting as a defense mechanism could help Cyclotella sp. to reduce the oxidative damage caused by the heavy metal Cr(VI). Cr(VI) was also combined with the functional groups on the cell surface to detoxify and was transported into the cell by binding to the carrier protein. In addition, it is worth noting that the molecular docking simulation showed that Cr(VI) combined with macromolecular compounds in cells through hydrogen and ionic bonds, which can reduce the toxicity of chromium. The determination of chromium content in cells showed that chromium was accumulated in cells. Furthermore, the low concentration of Cr(VI) had a growth stimulation on Cyclotella sp., while the growth of Cyclotella sp. microalgae was obvious inhibited when Cr(VI) concentration was over 0.5 mg/L. The content of Chlorophyll a (Chl-a) and soluble protein both had a dramatic change under the stress of Cr(VI). Cell ultrastructure analysis showed that plasmolysis phenomenon and dissolution of organelle structures when Cyclotella sp. was exposed to Cr(VI). The series of changes in Cyclotella sp. allow it to be an indicator of Cr(VI) pollution in water. Meanwhile, these findings were helpful to further understand the tolerance mechanism of Cr(VI) on microalgae and provide new insights to assess Cr(VI) toxicity to the microalgae.

An effective method of edge deburring in laser surface texturing was presented. Tribologically, suitably orientated micro-dimples on Co-Cr-Mo alloy can effectively reduce interfacial friction due to their storing of wear debris. However, burrs generated around dimple rim during laser irradiation inclined to cause plowing wear due to their piercing and cutting effect. This study was conducted to evaluate a technique for improving the quality of the laser-irradiated textures by implementing a freezing water layer to cover onto the texturing substrate surface. The existence of such freezing water layer reduced both Young’s modulus and hardness of the substrate material around the peripheral edge of the laser-ablated textures. Experimental results showed that integrating the laser texturing technology with the freezing water layer effectively constrained the deburring, and its beneficial mechanism in improving the quality of textures was also propounded. The irradiation technique reduced simultaneously the friction coefficient and wear.

Excessive wear debris in prosthesis tends to induce loosening, which is a major problem affecting the durability of long-serving implants. Although bionic synovial fluid can be used to improve the lubrication of artificial joints, the fluid is often absorbed easily by the tissues of human body. To enhance the effectiveness of bionic synovial fluid, poly(e-caprolactone)-poly(ethylene glycol)-poly(e-caprolactone) (PCEC) hydrogel was prepared as a carrier for the bovine serum albumin (BSA) in synovial fluid. It thus significantly reduces the loss rate of BSA. Experimental results show that the good sustainability and favorable release ability of hydrogel efficiently prevent the rapid outflowing of BSA. Experiments also reveal that the PCEC hydrogel inclines to form a particular structure with BSA and thus give BSA an excellent slow-release performance. Furthermore, friction and wear tests indicate that the released solution from the PCEC hydrogel possesses good lubricating properties. In general, the average friction coefficient of released solution is approximatively 77% lower than that of the normal phosphate-buffered solution. This study furnishes with an effective approach to prolong the lubricating duration of BSA in artificial prostheses.

The goal of the work is to investigate the lubrication mechanism of MoS2 nano sheet. Polyisobutyleneamine Succinimide (PIBS) provides the steric repulsion to disperse nanoparticles in oil due to its long carbon chain. In the present study, the tribological behavior of nano-MoS2 sheet mixed with different percentages of PIBS was explored. The dispersed state and the mode of nano-MoS2 sheet entering the contact point were studied. Ball-on-disk results illustrated that the COF of nano-MoS2 in paraffin oil with free of PIBS was 26.2% compared with those containing 3 wt% PIBS, and the reduction of wear depth reached 41.9%. The nano-MoS2 sheets with 3 wt% PIBS were in discrete state in paraffin oil, which moved with side flow and could not enter the contact area to cause poor lubrication. Aggregation of particles took place in the case of low PIBS concentration and without PIBS, it entered the contact area and formed well-distributed MoS2 tribofilm to reduce friction and wear.

This paper focuses on the fault-tolerant control problem for an Internet-based three-tank system in the presence of possible sensor bias faults. The Internet-based three-tank system is an experimental setup that can be regarded as a typical networked system for evaluating networked fault-diagnosis and fault-tolerant control methods. Packet dropout phenomenon in the sensor-to-controller link is considered in this paper, and the fault type we deal with is chosen as the sensor bias fault. Fault-diagnosis unit is designed toward an auxiliary system. Sensor bias faults can be detected by comparing the residual signal generated by the fault detection filter and a prescribed threshold. After that, the fault can be isolated by using the residual analysis approach. Once the fault is isolated, it can be estimated iteratively in the least-squares sense. A fault accommodation method is proposed, and a fault-tolerant control strategy is achieved based on the fault information provided by the fault-diagnosis unit. The approach brought forward in this paper is demonstrated via an experimental study on the practical Internet-based three-tank system. Results show the effectiveness and the applicability of the proposed techniques.