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Nitrile butadiene rubber (NBR) is a water-lubricated bearing material that demonstrates excellent vibrational absorption and impact resistance; however, rapid wear under abnormal conditions is still a serious problem. Graphene (Gra) and carbon nanotubes (CNTs) are two types of carbon nanomaterials with different dimensions and excellent mechanical and friction properties. In this work, Gra and CNTs were used to fill the NBR, and a multifunctional friction and wear testing machine was used to study their impacts on the friction between NBR and ZCuSn10Zn2 under water lubrication conditions. The results indicate that both Gra and CNTs can effectively reduce the adhesion and the friction coefficient of NBR during the friction process. The two-dimensional lamellar structure of Gra is more likely to precipitate from the NBR matrix to generate a surface lubrication film, which can effectively reduce the friction coefficient. Both Gra and CNTs can prevent crack initiation and propagation in NBR during the wear process, thereby effectively reducing the wear of NBR. Compared with the two-dimensional structure of Gra, the one-dimensional linear structure of carbon nanotubes can "trap" the NBR molecular chains more effectively during the friction process, thus reducing the initiation and propagation of wear cracks and further improving the wear performance of NBR. • Effect of different dimensions of carbon nanomaterials on friction behavior of NBR. • Effect mechanism of two-dimensional graphene and one-dimensional carbon nanotubes on friction behavior of NBR. • NBR wear mechanism enhanced by two-dimensional graphene and one-dimensional carbon nanotubes. [ABSTRACT FROM AUTHOR]

This paper investigates how nano-SiO 2 interacts with NBR to affect the tribological properties of water-lubricated NBR-based composites using the Rtec friction and wear tester and the molecular dynamics simulation method. The surface-modified nano-SiO 2 (SiO 2(TESPT)) particles were prepared by modifying the hydroxyl groups on the surface of nano-SiO 2 with Silicon 69 (TESPT), and cast copper alloy (ZCuSn10Zn2) was used as the counterface material in the friction test and wear test. The results showed that different interfacial interplay between nano-SiO 2 and NBR makes for distinct wear mechanisms of NBR-based composites. With weak interface bonding between nano-SiO 2 and NBR, NBR/SiO 2 can easily get worn as nano-SiO 2 particles detach from the matrix during the wear process, leaving pits and cracks on the worn surface. Instead, SiO 2(TESPT) has stronger interface bonding with the matrix, which can prevent the detachment of SiO 2(TESPT) , restrict the movement of molecular chains in NBR, and reduce the temperature peak of the friction pair. SiO 2(TESPT) exerts a dual influence on the tribological properties of NBR: while significantly improving the wear resistance of NBR, it can also notably increase the friction coefficient of the composite. • TESPT was used to modify the surface of nano-SiO 2 to enhance its interfacial bonding with NBR-based composites. • Strong interfacial bonding has dual effects on tribological properties of NBR-based composites. • Strong interfacial bonding can improve the wear property of NBR-based composites. • The study reveals the tribological mechanism of NBR enhanced by stronger interfacial interaction between nano-SiO 2 and NBR. [ABSTRACT FROM AUTHOR]

The asymptotic boundary condition to solve the time-dependent Schrödinger equation for a short-range model potential in an intense laser field is presented. The condition is obtained by means of the asymptotic behavior of the short-range model potential in the sufficiently large distance and Fourier transformation, and then the time-dependent Schrödinger equation is discretized into an inhomogeneous linear canonical equation. The inhomogeneous linear canonical equation is solved using the symplectic algorithm. The calculated wavefunctions, time-evolution of the population on the bound state, and the high-order harmonic generation verify that our numerical method is reasonable and effective. [ABSTRACT FROM AUTHOR]

The friction and wear of water-lubricated bearings has always been an engineering problem that we need to solve urgently. To investigate the influence of SiO 2 particle size and dispersion on the friction and wear properties of nitrile rubber. The friction and wear performance of rubber compounds (SiO 2 (nano) /NBR, SiO 2 (micr) /NBR and SiO 2 (TESP) /NBR) was tested by American Rtec multifunctional friction and wear test machine under the conditions of water lubrication and constant temperature. The results showed that the particle size of SiO 2 has a great impact on its dispersion in nitrile rubber, and the surface modification of SiO 2 can significantly improve its dispersion. SiO 2 (TESPT) /NBR showed a good friction coefficient under low-speed and high-load conditions. The wear of SiO 2 (nano) /NBR and SiO 2 (micr) /NBR, which was mainly the fatigue wear, was relatively serious. In contrast, the modified SiO 2 had a smaller particle size, better dispersion and stronger interfacial bonding with the nitrile rubber matrix. This significantly reduced the wear of SiO 2 (TESPT) /NBR, which was mainly the abrasive wear, and improved its wear resistance. • TESPT was used to modify the hydroxyl groups on the surface of nano-silica. • The escape and disintegration of SiO 2 (micr) and SiO 2 (nano) agglomerates during the wear process were characterized. • The effect of particle size and dispersion of SiO 2 on tribological properties of nitrile rubber was revealed. [ABSTRACT FROM AUTHOR]

Highlights • The density of overlaid laminated bamboo lumber improves with proper layup. • The density has a different impact on effective modulus of rupture between two panel directions. • Failure steps through the bamboo nodes and bamboo curtain joints. Abstract The overlaid laminated bamboo lumber (OLBL) was developed for structural applications with an aim to substitute commonly-used building materials such as steel and concrete. The OLBL was, via a hot press, fabricated by cross-laminating bamboo layers, bamboo mats and phenolic impregnated adhesive papers. Since the weight of OLBL was governed by the high density bamboo layer, the panels made of OLBL had a relatively high density value of about 850 kg/m3. In this study, a lightweight panel was developed by a proper arrangement of radial bamboo curtain. The major and minor directions of a panel were the parallel- and perpendicular-to-its length direction, respectively. It was found that 1) the density of an OLBL panel could be reduced by about 20%; 2) the failure occurred in the bamboo node(s); 3) there was a significant difference in effective modulus of elasticity and effective modulus of rupture between two panel directions; and 4) there was a good relationship between the density and strength in the minor direction. [ABSTRACT FROM AUTHOR]

Purpose: Ultra-high molecular weight polyethylene (UHMWPE) is adopted in water-lubricated bearings for its excellent performance. This paper aims to investigate the tribological properties of UHMWPE with a molecular weight of 10.2 million (g mol‐1) under different molding temperatures. Design/methodology/approach: The UHMWPE samples were prepared by mold pressing under constant pressure and different molding temperatures (140°C, 160°C, 180°C, 200°C, 220°C). The friction and wear tests in water were conducted at the RTEC tribo-tester. Findings: The friction coefficient and wear loss decreased first and rose later with the increasing molding temperature. The minimums of the friction coefficient and wear loss were found at the molding temperatures of 200°C. At low melting temperatures, the UHMWPE molecular chains could not unwrap thoroughly, leading to greater abrasive wear. On the other hand, high melting temperatures will cause the UHMWPE molecular chains to break up and decompose. The optimal molding temperatures for UHMWPE were found to be 200°C. Originality/value: Findings are of great significance for the design of water-lubricated UHMWPE bearings. [ABSTRACT FROM AUTHOR]

Abstract: A quasiclassical trajectory study with the fourth-order explicit symplectic algorithm for the atmospheric reaction has been performed by employing a new analytical fit of ab initio electronic structure calculations for the ground potential energy surface reported by Sayós et al. The effect of the relative translational energy, the vibrational energy and rotational energy of O2 molecule on the reaction probability and the reaction cross-section has been analyzed in details. The microscopic rate constant and the thermal rate constant have also been evaluated at the low translational temperature, and results have been compared with the experimental data and previous theoretical values. It is concluded that the thermal rate constants at the low temperature considered in this work agree well with the recommended experimental data and are very close to the variational transition state theory values carried out by Sayós et al. [Copyright &y& Elsevier]

High-levelab initiocalculations have been performed on the PBr radical by using multi-reference configuration interaction method plus Davidson correction (+Q) with correlation-consistent quadruple-ζ quality basis set. The potential energy curves (PECs) of the 22 Λ–S states of PBr have been obtained, most of which are reported for the first time. From the PECs of the bound states, the spectroscopic constants have been determined, in good agreement with the experimental results where available. Due to the large state density, there exhibits complicated interactions in the electronic excited states of PBr. The possible interactions by the spin–orbit coupling (SOC) effect have been discussed based on the evaluatedR-dependent spin–orbit matrix elements. The 51 Ω states, generating from the 22 Λ–S states after taking SOC into account, have been computed. The Λ–S component analysis of the wavefunctions for the Ω states indicates the strong interaction of the Λ–S states especially at the avoided crossing points and near the dissociation limits. Finally, the transition dipole moments of several transitions arising from upper Ω states to the X10+and X21 states and the corresponding radiative lifetimes have been studied. Our calculation results provide new information that should be valuable for further experimental studies on the electronic excited states of the PBr radical. [ABSTRACT FROM AUTHOR]

Wood-plastics composite (WPC) is a new kind of composite material, booming at home and abroad in recent years. It includes 2 types: one is the composite produced directly using extrusion and injection methods based on biomass materials such as wood powder, bamboo powder and hemp fiber; the other is based on carbonized biomass materials, which is fabricated by carbonizing biomass materials at high temperature and then compounding with polymer. The former has been studied in detail, but the latter is scarce. So in this paper, we prepared the charcoal/epoxy composites using compressing method. The effects of charcoal content on the mechanical properties and the heat resistance of charcoal/epoxy composites were investigated using scanning electron microscope (SEM), material testing machines, dynamical thermal mechanical analyzer (DMA) and Vicat softening temperature (VST) measuring instrument. The epoxy, diluents and curing agent at weight ratio of 3:2:5 were used to yield charcoal/epoxy composites. The weight fraction of charcoal in composite was set to 5%, 10%, 20%, 30% and 40%, and the curing temperature and curing time were 100°C and 3 h, respectively. The results showed that the charcoal in composites, acting as physical cross-link, could improve the mechanical properties of epoxy resins. The flexural strength of composites increased from 10.1 to 38.2 MPa as charcoal loading increased from 0 to 10%, but it started to reduce when charcoal loading exceeded 10%. Like flexural strength, the impact strength of composites also increased from 8.7 to 20.5 kJ/m2 within 10% charcoal loading. However, the flexural modulus of composites increased with charcoal loading increasing till 30%. At high charcoal content, due to the poor wetting properties of charcoal, the mechanical properties of composites began to decrease. The DMA results confirmed that the glass transition temperature of epoxy resins was elevated from 37.5°C to 60.5°C as charcoal loading increased from 0 to 10%, indicating strong interaction between epoxy and charcoal. When charcoal loading exceeded 10%, the glass transition temperature started to decline, but it was still higher than that of net epoxy resins. The addition of charcoal improved the heat resistance of epoxy composites, and the VST of charcoal/epoxy composites increased linearly with the increasing of charcoal loading. The 10% charcoal made the VST of epoxy resins increase from 81.2°C to 126.6°C. Further elevating the charcoal loading caused the VST of composites to exceed 200°C. The results indicate that the charcoal/epoxy composites have better mechanical properties and heat resistance with the charcoal loading of 10%. [ABSTRACT FROM AUTHOR]

Ab initio calculations on CdH + cation have been performed with the high-level relativistic MRCI + Q method. The potential energy curves of seven low-lying Λ–S states, correlated with the dissociation limits Cd + ( 2 S g ) + H( 2 S g ), Cd( 1 S g ) + H + ( 1 S g ), and Cd + ( 2 P u ) + H( 2 S g ), are computed. And the accurate spectroscopic constants of the bound Λ–S are determined. The permanent dipole moments (PDMs) of Λ–S states as well as the spin–orbit matrix elements are evaluated. The results indicate that the abrupt changes of PDMs and the spin–orbit matrix elements are attributed to the change of the electronic configurations at the avoided crossing point. After considering the spin–orbit coupling (SOC) effect, the 12 Ω states generated from the Λ–S states are investigated. It is indicated that the SOC effect is substantial for CdH + , leading to the double-well potential of (3)0 + state. Finally, the transition properties of several transitions are reported, including the transition dipole moments, Franck–Condon factors, and radiative lifetimes. [ABSTRACT FROM AUTHOR]

We study the chaotic dynamics in the Bose-Einstein condensate (BEC) system of a double lattice. Chaotic space-time evolution is investigated for the particle number density in a BEC. By changing of the s-wave scattering length with a Feshbach resonance, the chaotic behavior can be well controlled to enter into periodicity. Numerical calculation shows that there is periodic orbit according to the s-wave scattering length only if the maximal Lyapunov exponent of the system is negative. [ABSTRACT FROM AUTHOR]

Nitrile Butadiene Rubber (NBR) is widely used in ship water-lubricated stern tube bearings. Sediments in the water would cause a serious effect on friction and wear properties of the water-lubricated bearings. In this study, the tribological performance of water-lubricated rubber bearings under different sediment particle sizes and sand types were analyzed. Two sediment sand types are involved in the research, (i) SiO 2 particles with sizes of 0–25 μm, 48–60 μm, 75–90 μm and 150–200 μm, respectively; (ii) Sediment particles collected from the Yangtze River with sizes of 48–60 μm, 75–90 μm and 120–150 μm, respectively. The friction coefficients and wear volumes as well as surface morphology were measured. It was found that NBR worn by SiO 2 particles was worse than that by the sediment within a certain particle size range. On the other hand, the particle sizes exhibited significant effects on the tribological properties. As the particle size increased, the largest wear volume of NBR occurred at particle size of 75–90 μm, While the friction coefficient grew firstly and then fell down, and reached its maximum at particle size of 48–60 μm. Additionally, the friction coefficient demonstrated a negative correlation with sliding speed regardless of the sediment type and particle size. The particle sizes were prevented from flowing into the friction pair as applied load increased. In conclusion, this research offers a great insight for designing water-lubricated bearings. [ABSTRACT FROM AUTHOR]

A high level ab initio study on electronic states of sulfur dimer S 2 is carried out by utilizing multi-reference configuration interaction plus Davidson correction (MRCI+Q) method. The modification to the electronic structures caused by spin-orbit coupling (SOC) effect is taken into consideration by the state-interacting method with the full Breit-Pauli Hamiltonian. The potential energy curves (PECs) of 19 Λ-S states and 52 Ω states generated from the Λ-S states are calculated. With the aid of calculated SOC matrix elements and the PECs of the Ω states, we discuss the predissociaiton of the B3Σ u − state. The variation of line width of B3Σ u −- X3Σ g − transitions with vibrational quantum number v ' of the B3Σ u − are determined from Fermi golden rule calculations. Our study indicate that the predissociation of the B3Σ u − state is induced by the strong spin-orbit coupling with different electronic excited states, resulting in the abnormal dependence of the dissociation rate on vibrational states. Unlabelled Image • Electronic states of S 2 are studied by MRCI+Q method including spin-orbit coupling effect. • Linewidths for B-X vibronic transitions are evaluated by using Fermi golden rule calculations. • Predissociation mechanism of the B3Σ − u state is analyzed. [ABSTRACT FROM AUTHOR]

Unacceptable vibrations induced by the friction in the water-lubricated bearing-shaft system can seriously undermine the reliability and concealment performance of the ship. The mechanism of frictional vibration and the coupling process with torsional vibration are not yet entirely understood. In this study, a glass shaft is used to form a friction pair with a rubber block. To explore the frictional vibration mechanism and process of coupling with torsional vibration, a high-speed camera records the responses of the rubber, fixer and shaft simultaneously. The frictional vibration in stern shaft system is visually revealed by joint analysis of vibration, noise, friction, and images. Most importantly, the coupling process of frictional and torsional vibrations in the stern shaft system is intuitively displayed. • A transparent glass shaft was used to form a friction pair with a rubber test block. • With the help of a high-speed camera, the dynamic responses of the friction pair were recorded and analyzed. • The mechanism of frictional vibration was explained by joint analysis of vibration, noise, friction and image data. • The coupling process of frictional vibration and torsional vibration was explored visually. [ABSTRACT FROM AUTHOR]