The preparation of graphene/polylactic acid nanocomposites by modifying polylactic acid with graphene and its derivative graphene oxide is reviewed. It mainly includes solution method and melt blending method. Under different processing methods, the dispersion degree of nano fillers in the matrix is different, and the properties of the obtained materials are different. The choice of graphene and graphene oxide has a greater impact on the properties of the materials. The improvement of the mechanical properties of graphene /PLA composite materials has made the performance of PLA in packaging, textiles, biomedicine and other fields more excellent, while the gas isolation performance and electrical conductivity brought by graphene have opened up more new directions for graphene /PLA composite materials, such as 3d printing materials.
We propose a scheme for the two-dimensional (2D) localization of an atom in a four-level Y-type atomic system. By applying two orthogonal standing-wave fields, the atoms can be localized at some special positions, leading to the formation of sub-wavelength 2D periodic spatial distributions. The localization peak position and number as well as the conditional position probability can be controlled by the intensities and detunings of optical fields.
Li1.3Al0.3Ti1.7(PO4)3 (LATP) is a promising solid electrolyte for lithium-ion batteries. However, it is challenging to densify LATP ceramics at reduced sintering temperature while preserving their electrical properties. Herein, LATP ceramics were pre-densified via cold sintering process (CSP) at 250 °C for 1 h and exhibited room temperature ionic conductivity of 2.01 × 10-6 S/cm. Subsequent post-annealing at as low as 900 °C for 1 h resulted in two orders of magnitude improvement in both grain boundary conductivity and total conductivity, compared to those of as-CSPed LATP. The optimal total conductivity (4.29 × 10-4 S/cm) obtained from post-annealed material is among the best reported values so far. It is also 5 times greater than the conductivity (8.51 × 10-5 S/cm) of the conventionally sintered LATP. We propose that post-annealing effectively eliminates amorphous insulating phases generated during CSP, promotes crack-free microstructure with moderate grain growth, and induces space charge effect, which collectively contributes to dramatically enhanced conductivity. This work unambiguously demonstrates that CSP-assisted process can avoid the detrimental effects of high temperature associated with conventional sintering on microstructure and conductivity, and thus is a cost-effective processing route for fabrication of solid-state electrolytes and batteries.
The use of two deformable mirrors (DM) with finite conjugate ranges is studied for compensating amplitude and phase distortions due to laser propagation through turbulence atmosphere. The Strehl ratio versus the log-amplitude variance (also known as the Rytov parameter) and the conjugate range of the second deformable mirror are plotted. The conclusion is drawn that an adaptive optics transmitting system with two DMs can clearly improve theoretical performance (compared to a system with one DM) in delivering energy on target through atmospheric turbulence. The second DM placed at a finite conjugate range can minimize lost energy outside the radius of the first deformable mirror and thus maximize the Strehl ratio.
In order to accurately simulate the actual road driving resistance of four-wheel drive motor vehicles based on the chassis dynamometer and efficiently test the vehicle performance, it is necessary to analyze the influencing factors of the additional loss resistance and the loading resistance of the chassis dynamometer bench system. In this paper, the effects of the drum speed, the sampling speed interval, and basic inertia on the test results of the additional loss resistance are tested and analyzed based on the self-developed chassis dynamometer of a four-wheel drive motor vehicle. The static and dynamic components of the additional loss resistance are defined by linear regression through ordinary least squares, and the additional loss resistance of the four-axis eight-drum chassis dynamometer and mainstream chassis dynamometer system for four-wheel drive motor vehicles are compared. In addition, the effects of the dynamometer type and the control strategy on the loading resistance are discussed, and the transient condition, steady-state condition, and overall operating condition deviation coefficient of loading force are defined, according to which the advantages and disadvantages of the control strategy of the chassis dynamometer system for four-wheel drive motor vehicles are evaluated. The analysis of the influencing factors and laws of the resistance of the four-wheel drive motor vehicle chassis dynamometer bench system can provide a reference basis for accurately simulating the resistance of vehicle road driving based on the bench testing.
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