Microstructure and anti-oxidation property of CrSi2-SiC coating for carbon/carbon composites

To protect carbon/carbon (C/C) composites from oxidation, a new type of oxidation protective coating has been produced by a two-step pack cementation technique. XRD and SEM analysis show, the coating obtained by the first step pack cementation was a porous β-SiC structure, and a new phase of CrSi₂ was generated in the porous SiC coating after heat-treatment according to the second step pack cementation process. Oxidation test shows that, the weight loss of the SiC coated C/C is up to 11.26% after 5 h oxidation in air at 1773 K, and the weight loss of the CrSi₂-SiC coated C/C composites is only 4.15% after oxidation in air at 1773 K for 34 h. The oxidation of C/C composites was primarily due to the reaction of C/C matrix and oxygen diffusing through the penetrable cracks in the coating.     

相对论平均场理论对∧,Ξ和∑超核的研究(英文)

基于相对论平均场理论,系统地研究了单∧,Ξ和∑超核,超子-核子相互作用通过拟合实验数据以及参照之前理论工作来确定。以16O为核芯,通过加入不同类型超子（∧,Ξ0,-和∑+,0,-）,比较了超子的平均势场和单粒子能级,并研究了对核芯的杂质效应。整体上看,∧和Ξ0超子在大块性质上类似;Ξ0超子平均势场最浅;库仑相互作用对于带电超子Ξ-,∑+和∑-非常重要。作为杂质,原子核中加入超子会使整个体系更束缚。然而,不同超子对原子核的半径有不同效应。此外,讨论了ωYY张量耦合,发现其对超子的能级劈裂有显著影响,甚至导致Ξ超子中出现能级反转现象。Single ∧, Ξ, and ∑ hypernuclei are systematically studied within the framework of relativistic mean-field (RMF) model with YN interactions being constrained according to the experimental data and previous theoretical efforts. By adding a hyperon to 16O, the mean-field potentials and single-particle levels for hyperons (∧, Ξ0,-, and ∑+,0,-) are compared and the impurity effects on the nuclear core are examined. In general, the ∧ and ∑0 hyperons show similar behaviors in bulk properties since both of them are electroneutral and with similar coupling constants; Ξ0 hyperon owns the shallowest mean-field potential well; and Coulomb interactions play vital roles in the charged Ξ-, ∑-, and ∑+ hyperons. As an impurity, the intruded single-hyperon makes the nuclear system more bound in most cases due to the attractive NY interaction. However, very different effects on the nucleon radii are observed for different hyperons. Besides, the effects of the ωYY tensor couplings on the spin-orbit splitting are discussed, and remarkable influences are found which even change the level ordering of Ξ hyperon.     

Using Laser Measuring and SFM Algorithm for Fast 3D Reconstruction of Objects

Effective measurement of the reflective or transparent surface of an object has always been a disadvantage in laser scanning modeling. We propose a fast and complete three-dimensional (3D) reconstruction method for small static objects using laser scanning and the structure from motion (SFM) algorithm. Meanwhile, a complete reconstruction workflow is designed and a multi-angle 3d reconstruction system is set up. To generate the complete point cloud model of the object, the SFM algorithm is used to reconstruct the surface part of the object, the data for which cannot be obtained by the laser measuring instrument. The experimental results show that this method not only improves the speed, accuracy, integrity, and visual effect of 3D reconstruction of small objects, but also extends the scope of 3D reconstruction of laser measurement.     

Microwave photonics reconfigurable mixer based on polarization modulator

A reconfigurable and stable mixer is proposed and demonstrated in this paper. It mainly consists of a dual-driven Mach–Zehnder modulator and a polarization modulator with several polarization controllers (PC) and polarizers (Pol). According to the theoretical analysis, different functions (such as single ended mixer, balanced mixer, I/Q mixer and image rejection mixer) can be realized by adjusting the PCs and Pols. The simulation results verify the possibility of multi-functions that realized by the reconfigurable mixer. In addition, another research on how the non-ideal parameters affect the image rejection ratio (ISR) and conversion efficiency of the mixer is also carried. The results show that both of them perform better as the extinction ratio gets higher. However, they are incurring a sharp decrease if the DC bias points deviate from the settled values. In the meantime, the results also indicate that the higher modulation indices lead to a better ISR. A 57.12 dB ISR can be achieved with conversion efficiency of ? 9.53 dB.     

Exotic ferromagnetism in the two-dimensional quantum material C<Subscript>3</Subscript>N

The search for and study of exotic quantum states in novel low-dimensional quantum materials have triggered extensive research in recent years. Here, we systematically study the electronic and magnetic structures in the newly discovered two-dimensional quantum material C₃N within the framework of density functional theory. The calculations demonstrate that C₃N is an indirect-band semiconductor with an energy gap of 0.38 eV, which is in good agreement with experimental observations. Interestingly, we find van Hove singularities located at energies near the Fermi level, which is half that of graphene. Thus, the Fermi energy easily approaches that of the singularities, driving the system to ferromagnetism, under charge carrier injection, such as electric field gating or hydrogen doping. These findings not only demonstrate that the emergence of magnetism stems from the itinerant electron mechanism rather than the effects of local magnetic impurities, but also open a new avenue to designing field-effect transistor devices for possible realization of an insulator–ferromagnet transition by tuning an external electric field.     

Effect of high-temperature crystallization on the electrochemical properties of LiNi<Subscript>0.5</Subscript>Co<Subscript>0.2</Subscript>Mn<Subscript>0.3</Subscript>O<Subscript>2</Subscript> synthesized from a lithiated transition metal oxide precursor

The lithiated transition metal oxide precursor (LNCMO) with typical α-NaFeO₂ structure and imperfect crystallinity, obtained from a hydrothermal process, was pretreated at 500 °C and then subjected to sintering at 800–920 °C to synthesize the ternary layered LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523). X-ray diffraction (XRD), scanning electron microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge/discharge testing were used for investigating the effect of the high-temperature crystallization on the properties of the NCM523 cathode materials. The results show that the materials heated at 880–900 °C possess superior cation ordering, perfect crystallinity, and excellent electrochemical performances, among which the material heated at 900 °C delivers better performances, with the initial discharge capacity of 152.6 mAh g^?1 at 0.5 C over 3.0 to 4.3 V and the capacity retention of 95.5% after 50 cycles. Furthermore, the effect of the high-temperature crystallization on the Li⁺ diffusion coefficient, potential polarization, and electrochemical resistance are discussed.     

Progressive ganglion cell loss and optic nerve degeneration in DBA/2J mice is variable and asymmetric

Background  

Glaucoma is a chronic neurodegenerative disease of the retina, characterized by the degeneration of axons in the optic nerve and retinal ganglion cell apoptosis. DBA/2J inbred mice develop chronic hereditary glaucoma and are an important model system to study the molecular mechanisms underlying this disease and novel therapeutic interventions designed to attenuate the loss of retinal ganglion cells. Although the genetics of this disease in these mice are well characterized, the etiology of its progression, particularly with respect to retinal degeneration, is not. We have used two separate labeling techniques, post-mortem DiI labeling of axons and ganglion cell-specific expression of the βGeo reporter gene, to evaluate the time course of optic nerve degeneration and ganglion cell loss, respectively, in aging mice.     

A satellite cluster as a gravitational-wave detector

The detection of gravitational waves by a cluster of satellites is considered. The detector is an optical interferometer formed of several satellites. The calculations for three spacecraft are given. The complete detector response to the monochromatic gravitational wave generated by a binary star is computed.     

Single-Photon Scattering Grating in a Waveguide-Cavity System

We investigate single-photon scattering grating in a one-dimensional waveguide coupled to a cavity embedded with a driven Λ-type three-level atom. The single-photon reflection amplitude and transmission amplitude in the waveguide are obtained via a real-space approach, respectively. By spatially modulating a classical control field to drive the three-level emitter, alternating regions of high reflection and absorption as well as high transmission and absorption of the single photon are generated in both directions of the waveguide, which acts as a kind of scattering grating. The proposed scheme may have the potential for the design of chip-integrated grating.