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Rice–crab co-culture systems represent integrated agriculture–aquaculture systems developed in China over the last 30 years. The rice–crab co-culture area comprised approximately 1.386 × 105 hm2 in 2019. However, there is no specific feed designed for Chinese mitten crab (Eriocheir sinensis) cultured in this system until now. In this study, we investigated feed formulae for the nutritional requirements of Chinese mitten crab in this mode. The control group was not fed with any artificial feed (Co), and the experimental groups were fed with three different feeds of 15% (T15), 30% (T30), or 45% (T45) protein content, respectively. Growth performance variations in E. sinensis were investigated along with water quality, phytoplankton, zooplankton, aquatic vascular plants, and benthic animals in the paddy fields to determine the effect of crabs and their diet on the paddy ecosystem. Dietary protein levels had no significant effect on water quality. The biomass and species of phytoplankton, zooplankton, aquatic vascular plants, and zoobenthos in the paddy field were affected by crabs and their diet. Morphological parameters of crabs were significantly more pronounced in the high-protein group than in the other groups. However, the T45 diet negatively affected production by increasing feed costs, causing precocious puberty and inducing water eutrophication. In conclusion, adding a 15% protein compound feed can meet the nutritional needs of crabs, reduce culture costs, and improve water quality. The discharged water had low ammonia nitrogen and nitrite content and no eutrophication occurred, so the water could be recycled. These findings provide a scientific reference for supporting rice and fish co-cultivation. [ABSTRACT FROM AUTHOR]

The electronic structure and spectroscopic properties of the germanium dimer have been investigated by high-level ab initio calculations with consideration of spin–orbit coupling (SOC). The potential energy curves (PECs) of 19 Λ–S states, as well as those of 52 Ω states generated from the Λ–S states, are calculated by the multireference configuration interaction plus Davidson correction (MRCI + Q) method. The properties of the F3Σ +u1 −X3Σ −g1 and H3Σ −u1 −X3Σ −g1 transitions as well as the interactions of the F3Σ +u and H3Σ −u states with other excited states induced by SOC are investigated based on the calculated SO matrix and the PECs of the Ω states. Our results indicate that the previously observed spectra of Ge2 in the range 20 500–22 000 cm−1 should be assigned as the transition between the Ω = 1g component of the X3Σ −g state and Ω = 1u of the F3Σ +u state. Moreover, owing to the strong SOC with the repulsive 25Πu state, the H3Σ −u state is predissociative, leading to the Ge(3P2) + Ge(3P1) channel at vibrational levels higher than v′ = 6. Our theoretical study would provide comprehensive information and shed light on understanding the spectroscopy and dynamics of the electronic excited states of Ge2. [ABSTRACT FROM AUTHOR]

The frictional vibration generated in water-lubricated rubber bearings operating under low speed, heavy load, startup and shutdown conditions can severely degrade the reliability and the sheltered performance of underwater vehicles. The rubber layer of the ship stern tube water-lubricated rubber bearings is easily elastically deformed under certain loads, which affects the damping performance of the bearing system. To explore the effects of thickness, hardness, and concavo-convexity on the damping property of water-lubricated rubber stern bearings, frictional force, vibration, noise, and displacement and deformation of the contact area were studied using a test rig with a transparent glass cylinder. An orthogonal L9(3)4 test design was applied accordingly to determine the optimum construction and material parameters of the rubber layer. Orthogonal test results indicate that among rubber layer hardness, thickness, and test block concavo-convexity, the former is most significant in terms of the frictional vibration, followed by the thickness and, finally, the radius of the surface. When the hardness is 65 A, the thickness is 12 mm, and the plate type is concave, the frictional vibration performance of the rubber layer is optimal. More important, based on the static deformation and the dynamic displacement of the rubber, the causes of the frictional vibration and the influence of different materials and structural parameters on frictional vibration were visually analyzed. The overall trends and the mechanism discussed in this research may be considered as a guideline for the design, optimization, and manufacture of water-lubricated bearings. [ABSTRACT FROM AUTHOR]

The aim of this study was to improve the mechanical properties of an acrylonitrile--styrene--acrylate copolymer (ASA) with the help of carbon fibers (CFs). Additionally, the effects of the CFs on the morphology, rheological properties, dynamical mechanical properties, electrical resistivity, and heat resistance of the ASA composites were studied with scanning electron microscopy, rotational rheometry, and dynamic thermomechanical analysis (DMA). The mechanical properties of the ASA composites were enhanced largely by the CFs. The maximum tensile strength of the ASA/CF composites reached 107.2 MPa. The flexural strength and flexural modulus also reached 162.7 MPa and 12.4 GPa, respectively. These findings were better than those of neat ASA; this was attributed to the excellent interfacial adhesion between the CFs and ASA resin. Rheological experiments proved that the viscosity and storage modulus (G0) values of the ASA/CF composites did not increase until the CF content reached 20%. The DMA outcomes confirmed that the glass-transition temperature of the ASA composites was elevated from 120.6 to 125°C. Importantly, the G0 values of the composites with 20 and 30% CFs showed a large increase during heating. In addition, the ASA/CF composites exhibited excellent conductivity and heat resistance [ABSTRACT FROM AUTHOR]

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]

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]

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]

Using the three-dimensional classical ensemble approach, we theoretically investigate the nonsequential double ionization of argon atoms in an intense laser field enhanced by bowtie-nanotip. We observe an anomalous decrease in the double ionization yield as the laser intensity increases, along with a significant gap in the low momentum of photoelectrons. According to our theoretical analysis, the finite range of the induced field by the nanostructure is the fundamental cause of the decline in double ionization yield. Driven by the enhanced inhomogeneous field, energetic electrons can escape from the finite range of nanotips without returning. This reduces the possibility of re-scattering on the nucleus and imprints the finite size effect into the double ionization yield and momentum distribution of photoelectrons in the form of yield decline and a gap in the photoelectron-momentum distribution.

The carrier-envelop-phase (CEP) dependence of nonsequential double ionization (NSDI) of atomic Ar with few-cycle elliptically polarized laser pulse is investigated using 2D classical ensemble method. We distinguish two particular recollision channels in NSDI, which are recollision-impact ionization (RII) and recollision-induced excitation with subsequent ionization (RESI). We separate the RII and RESI channels according to the delay time between recollision and final double ionization. By tracing the history of the trajectories, we find the electron correlation spectra as well as the competition between the two channels are sensitively dependent on the laser field CEP. Finally, control can be achieved between the two channels by varying the CEP.