非离子型表面活性剂Tween 60用于碳纳米管的双水相分离

单壁碳纳米管以其优异的电学和光学性能受到了广泛的关注,高性能器件等应用要求使用性质均一的单壁碳纳米管.因此,不同结构的单壁碳纳米管的分离具有重要意义.双水相萃取是一种能够对单壁碳纳米管进行结构分离的新方法,分离结果稳定可靠,且不需要复杂的设备,具有简捷、高效、易扩大规模等特点.本文通过调节脱氧胆酸钠(DOC)和非离子型...     

Reflection and Transmission of Plane Waves at a Water–Porous Sediment Interface with a Double-Porosity Substrate

This paper investigates the wave propagation at the interface between the ocean and the ocean floor. The ocean floor is assumed to be composed of covered porous sediment with an underlying double-porosity substrate. For this purpose, plane wave reflection and transmission in the coupled water–porous sediment–double-porosity substrate system are analytically solved in terms of displacement potentials. Using numerical examples, the effects of the material properties of the underlying double-porosity substrate on the reflection coefficients are discussed in detail. Variations in pore and fracture fluid, fracture volume fraction, and permeability coefficients are considered. In addition, two cases of boundary conditions at the porous sediment–double-porosity substrate interface, i.e., sealed-pore boundary and open-pore boundary, are compared in the numerical calculations. Results show that material property variations in the double-porosity substrate may significantly affect the reflected wave in the overlying water if the sandwiched sediment depth is less than the critical value.     

Night vision dense crowd counting based on mid-term fusion of thermal imaging features北大核心CSCD

为了提高人群计数模型对尺度和光噪声的鲁棒性,设计了一种多模态图像融合网络。提出了一种针对夜间人群统计模型,并设计了一个子网络Rgb-T-net,网络融合了热成像特征和可见光图像的特征,增强了网络对热成像和夜间人群特征的判断能力。模型采用自适应高斯核对密度图进行回归,在Rgb-T-CC数据集上完成了夜视训练和测试。经验证网络平均绝对误差为18.16,均方误差为32.14,目标检测召回率为97.65%,计数性能和检测表现优于当前最先进的双峰融合方法。实验结果表明,所提出的多模态特征融合网络能够解决夜视环境下的计数与检测问题,消融实验进一步证明了融合模型各部分参数的有效性。     

Molten-Salt-Mediated Synthesis of an Atomic Nickel Co-catalyst on TiO2 for Improved Photocatalytic H2 Evolution

Atomic co-catalysts offer high potential to improve the photocatalytic performance, of which the preparation with earth-abundant elements is challenging. Here, a new molten salt method (MSM) is designed to prepare atomic Ni co-catalyst on widely studied TiO₂ nanoparticles. The liquid environment and space confinement effect of the molten salt leads to atomic dispersion of Ni ions on TiO₂, while the strong polarizing force provided by the molten salt promotes formation of strong Ni−O bonds. Interestingly, Ni atoms are found to facilitate the formation of oxygen vacancies (OV) on TiO₂ during the MSM process, which benefits the charge transfer and hydrogen evolution reaction. The synergy of atomic Ni co-catalyst and OV results in 4-time increase in H₂ evolution rate compared to that of the Ni co-catalyst on TiO₂ prepared by an impregnation method. This work provides a new strategy of controlling atomic co-catalyst together with defects for efficient photocatalytic water splitting.     

Grain size engineering and growth mechanism in hydrothermal synthesis of Bi0.5Na0.5TiO3 thin films on Nb-doped SrTiO3 substrates

Journal of Sol-Gel Science and Technology - Considering the full utilization of energy and pursuing thin-film capacitors with high energy-storage density, the grain size engineering is used to...     

Finite particle number description of neutron matter using the unitary correlation operator and high-momentum pair methods

Using bare Argonne V4' (AV4'), V6' (AV6'), and V8' (AV8') nucleon–nucleon (\begin{document}$NN$\end{document}) interactions, the nuclear equations of state (EOSs) for neutron matter are calculated with the unitary correlation operator and high-momentum pair methods. Neutron matter is described using a finite particle number approach with magic number \begin{document}$N=66$\end{document} under a periodic boundary condition. The central short-range correlation originating from the short-range repulsion in the \begin{document}$NN$\end{document} interaction is treated by the unitary correlation operator method (UCOM), and the tensor correlation and spin-orbit effects are described by the two-particle two-hole (2p2h) excitations of nucleon pairs, where the two nucleons with a large relative momentum are regarded as a high-momentum (HM) pair. With increasing 2p2h configurations, the total energy per particle of the neutron matter is well-converged under this UCOM+HM framework. Comparing the results calculated with AV4', AV6', and AV8' \begin{document}$NN$\end{document} interactions, we demonstrate the effects of the short-range correlation, tensor correlation, and spin-orbit coupling on the density dependence of the total energy per particle of neutron matter. Moreover, the contribution of each Hamiltonian component to the total energy per particle is discussed. The EOSs of neutron matter calculated within the present UCOM+HM framework agree with the calculations of six microscopic many-body theories, especially the auxiliary field-diffusion Monte Carlo calculations.     

Strain-Enhanced Metallic Intermixing in Shape-Controlled Multilayered Core–Shell Nanostructures: Toward Shaped Intermetallics

Controlling the surface composition of shaped bimetallic nanoparticles could offer precise tunability of geometric and electronic surface structure for new nanocatalysts. To achieve this goal, a platform for studying the intermixing process in a shaped nanoparticle was designed, using multilayered Pd-Ni-Pt core–shell nanocubes as precursors. Under mild conditions, the intermixing between Ni and Pt could be tuned by changing layer thickness and number, triggering intermixing while preserving nanoparticle shape. Intermixing of the two metals is monitored using transmission electron microscopy. The surface structure evolution is characterized using electrochemical methanol oxidation. DFT calculations suggest that the low-temperature mixing is enhanced by shorter diffusion lengths and strain introduced by the layered structure. The platform and insights presented are an advance toward the realization of shape-controlled multimetallic nanoparticles tailored to each potential application.     

15GHz马赫－陈德尔型Ti：LiNbO_3行波幅度电光调制器

比较了四种马赫－陈德尔调制器的结构特性，表明Ｚ切共面波导（ＣＰＷ）是最好的一种结构。用阶跃倒相电极设计了新型电光光波导幅度调制器，研制了包装式带尾光纤的有５段例相电极的马赫－陈德尔调制器。在１．５３２μｍ波长上，该器件调制带宽为１４．８ＧＨｚ，半波电压为１４Ｖ，消光比为２１．３ｄＢ，光纤－器件－光纤插入损耗７．６ｄＢ。     

Head–Tail Asymmetry as the Determining Factor in the Formation of Polymer Cubosomes or Hexasomes in a Rod–Coil Amphiphilic Block Copolymer

The self‐assembly of a rod–coil amphiphilic block copolymer (ABCP) led to Im m and Pn m polymer cubosomes and p6mm polymer hexasomes. This is the first time that these structures are observed in a rod–coil system. By varying the hydrophobic chain length, the initial concentration of the polymer solution, or the solubility parameter of the mixed solvent, head–tail asymmetry is adjusted to control the formation of polymer cubosomes or hexasomes. The formation mechanism of the polymer cubosomes was also studied. This research opens up a new way for further study of the bicontinuous and inverse phases in different ABCP systems.     

Coupling molecular rigidity and flexibility on fused backbones for NIR-II photothermal conversion

Great attention is being increasingly paid to photothermal conversion in the near-infrared (NIR)-II window (1000–1350 nm), where deeper tissue penetration is favored. To date, only a limited number of organic photothermal polymers and relevant theory have been exploited to direct the molecular design of polymers with highly efficient photothermal conversion, specifically in the NIR-II window. This work proposes a fused backbone structure locked via an intramolecular hydrogen bonding interaction and double bond, which favors molecular planarity and rigidity in the ground state and molecular flexibility in the excited state. Following this proposal, a particular class of NIR-II photothermal polymers are prepared. Their remarkable photothermal conversion efficiency is in good agreement with our strategy of coupling polymeric rigidity and flexibility, which accounts for the improved light absorption on going from the ground state to the excited state and nonradiative emission on going from the excited state to the ground state. It is envisioned that such a concept of coupling polymeric rigidity and flexibility will offer great inspiration for developing NIR-II photothermal polymers with the use of other chromophores.

Low bandgap and large deformation generally conflict each other. This work couples molecular rigidity and flexibility by intramolecular hydrogen bonds and double bonds to achieve NIR-II light absorption and reinforced internal conversion at the same time.