Fabrication of NixCo3-xS4 hollow nanosphere as wideband electromagnetic absorber at thin matched thickness

Nowadays, transition metal sulfide (TMS), especially for spinel crystal structure (A_xB_3-xS₄), have been proved to be a promising electromagnetic (EM) absorber if been used to deal with the severe electromagnetic pollution. However, EM performance degradation and absorption layer thickness-decreasing at present remains a big challenge, owning to the poor EM attenuation ability. To overcome this barrier, herein we reported a Ni_xCo_3-xS₄ (x = 0, 0.3, 0.6, 1.0) absorber with hollow sphere structure to realize a good EM performance with a thinner matched thickness (<1.5 mm). The average sizes of these Ni_xCo_3-xS₄ distributed in 450–550 nm. The dielectric loss ability (ε'') can be boosted by tuning the molar ratio of Ni/Co, which attributes to EM performance. Additionally, hollow structure would lead to the electromagnetic multi-reflection, also benefited to EM performance. The results demonstrated that the maximum qualified absorption bandwidth (f_E) of 3.8 GHz can be achieved for the Ni_0·3Co_2·7S₄ sample when specimen thickness only equals to 1.3 mm.     

Photomontage in the Present Perfect Continuous

In its first instance as art practice among the historical avant-garde, photomontage was considered indispensable for its claim to intervene in perceptual processes, stimulating a critical mode of apprehension that would redirect the viewer away from conventions of aesthetic experience and towards a lived reception of art with pronounced relevance to the sociopolitical landscape. The effect was understood as structural, that is, activated not so much by direct political content, but by the stark and shocking effects of juxtaposition. By this measure, one challenge to contemporary photomontage is clear: in a postindustrial and postdigital visual landscape dominated by the structural fragmentation of the attention economy, the ‘simultaneity of the radically disparate’ (as Peter Bürger put it) might no longer present as heterodoxy but rather threaten to sink into invisibility. Yet with the migration off-screen of the effects of electronic media, a new urgency around moving photomontage structures into physical, public space is rising in contemporary practices. Shannon Ebner’s multi-part project A Hudson Yard (2014–15) is emblematic of the new ways in which artists are manipulating photomontage as a form of fully sensory experience that gives the medium room to play critically in both virtual and material space. By constructing subtle interruptions of naturalised commercial space, A Hudson Yard activates a détournement of instrumentalised language, using structures of juxtaposition to divert the discursive surfaces of public space away from consumption and towards what could be called a public poesis.     

Controllable Fe/HCS catalysts in the Fischer-Tropsch synthesis: Effects of crystallization time

The Fischer–Tropsch synthesis (FTS) continues to be an attractive alternative for producing a broad range of fuels and chemicals through the conversion of syngas (H₂ and CO), which can be derived from various sources, such as coal, natural gas, and biomass. Among iron carbides, Fe₂C, as an active phase, has barely been studied due to its thermodynamic instability. Here, we fabricated a series of Fe₂C embedded in hollow carbon sphere (HCS) catalysts. By varying the crystallization time, the shell thickness of the HCS was manipulated, which significantly influenced the catalytic performance in the FTS. To investigate the relationship between the geometric structure of the HCS and the physic-chemical properties of Fe species, transmission electron microscopy, X-ray diffraction, N₂ physical adsorption, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction, Raman spectroscopy, and Mössbauer spectroscopy techniques were employed to characterize the catalysts before and after the reaction. Evidently, a suitable thickness of the carbon layer was beneficial for enhancing the catalytic activity in the FTS due to its high porosity, appropriate electronic environment, and relatively high Fe₂C content.     

TiO2 hollow spheres as a novel antibiotic carrier for the direct delivery of gentamicin

The TiO₂ hollow spheres were synthesized using a green, cheap, and easy process, in which carbonaceous spheres were chosen as the removable template. The prepared materials were characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDX), Atomic force microscopy (AFM), Fourier Transform Infrared Spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analysis. According to the results, the obtained mesoporous TiO₂ hollow spheres demonstrated an external diameters less than 200?nm with shell thickness around 40?nm. The antibacterial activities of the TiO₂ hollow spheres were evaluated against gram-positive (Bacillus subtilis and Staphylococcus aureus) and gram-negative (Escherichia coli and Pseudomonas aeruginosa). No antibacterial activity was found for TiO₂ hollow spheres in the used concentrations. TiO₂ hollow spheres were loaded with gentamycin as a selected antibiotic to magnify their benefits in biomedical applications. TiO₂ hollow spheres exhibited good antibiotic carrier activity for the direct delivery of gentamicin, which was attributed to interaction between gentamicin and surface due to their larger specific surface area, more abundant porous structure, and their spherical morphology. The application of TiO₂ hollow spheres as gentamicin carrier undoubtedly opens an avenue to use hollow sphere materials in other drug delivery applications.     

氮气球罐焊缝超标缺陷修复技术

通过对高含硫净化厂氮气球罐焊缝超标缺陷修复技术研究,高含硫净化厂氮气球罐焊缝超标缺陷修复技术,基本解决了在用氮气球罐现场修复难题,为国内同类设备检维修提供了经验。     

面向球幕投影系统的几何校正方法

摘 要：用于飞行模拟的视景仿真系统，经常会以多台投影仪同步投影以得到较大范围的 视场角。当投影机斜对屏幕或者投影屏幕为曲面时，图像会发生几何失真。针对此问题，本文 提出了一种专门面向球幕投影系统的几何校正方法，并以一个三通道显示系统为实例，详述了 该方法的理论原理以及校正流程。实例结果表明，经几何校正后，各投影图像无几何畸变，通 道过渡处几何内容完全一致。该方法是一种纯软件方法，成本小而且操作简单，能够适应于不 同的投影场景。     

Novel method of constructing generalized Hoberman sphere mechanisms based on deployment axes

This study proposes a method of constructing type II generalized angulated elements (GAEs II) Hoberman sphere mechanisms on the basis of deployment axes that intersect at one point. First, the constraint conditions for inserting n GAEs II into n deployment axes to form a loop are given. The angle constraint conditions of the deployment axes are obtained through a series of linear equations. Second, the connection conditions of two GAEs II loops that share a common deployable center are discussed. Third, a flowchart of constructing the generalized Hoberman sphere mechanism on the basis of deployment axes is provided. Finally, four generalized Hoberman sphere mechanisms based on a fully enclosed regular hexahedron, arithmetic sequence axes, orthonormal arithmetic sequence axes, and spiral-like axes are constructed in accordance with the given arrangement of deployment axes that satisfy the constraint conditions to verify the feasibility of the proposed method.     

Hollow tremella-like graphene sphere/SnO2 composite for high performance Li-ion battery anodes

A hollow tremella-like graphene sphere/tin dioxide (HTGS/SnO₂) composite was successfully prepared by simple emulsification and impregnation followed by calcination. In this material, tin dioxide adheres to the folds on the surface of the hollow tremella-like graphene spheres. Hollow tremella-like graphene spheres as the matrix of SnO₂ not only provide a space of volumetric expansion for the tin oxide particles, relieve the internal stress of the tin dioxide, but also effectively avoid aggregation of the tin dioxide and increase the electrical conductivity. As an anode electrode material for batteries, the initial discharge/charge capacities of HTGS/SnO₂ are 1762.4 mAh g^-1 and 1169.4 mAh g^-1, and the Coulomb efficiency is 96.9%. After 50 cycles, capacity remains 80.4% of reversible capacity. The excellent electrochemical stability is attributed to the extraordinary structure of HTGS/SnO₂. The hollow structure of graphene sphere allows simultaneous insertion of lithium ions from the inner and outer surfaces. Meanwhile, the tin dioxide particles are uniformly dispersed by the wrinkles on the surface of the graphene, thereby enlarging the space for the volume expansion of tin dioxide in order to avoid contact with the electrolyte.     

Waste sugar solution polymer-derived N-doped carbon spheres with an ultrahigh specific surface area for superior performance supercapacitors

Waste sugar solution (WSS), a waste by-product of manufacturing vitamin C, contains abundant waste acids and organics. In this work, a N/O-enriched copolymer was synthesized via a facile polymerization via the hydrogen bonding of O-containing functional groups and melamine and the crosslinking of aldehyde groups. Subsequently, N-doped carbon spheres were prepared by a typical carbonation/activation method. Remarkably, benefiting from an ultrahigh specific surface area (3612 m²/g) and rich heteroatom content (4.3% for N, 8.8% for O), the carbon spheres deliver a high specific capacitance of 387 F/g at 50 mA/g and 283 F/g at 5 A/g with 6 M KOH in two-electrode system. The assembled symmetric electric double-layer capacitor exhibits high energy density of 10.83 Wh/kg at 11.10 W/kg. This research provides a facile method for preparing N/O-doped carbon spheres by WSS, and confirms the excellent electrochemical performance of WSS-derived carbons in energy storage applications.     

空心球包覆处理制备氧化铝多孔陶瓷

采用浆料浸渍法在氧化铝空心球表面包覆高岭土和滑石粉(质量比为2∶3),利用高岭土和滑石粉引入的MgO-SiO2-Al2O3作为助烧剂,采用干压成型工艺制备氧化铝空心球多孔陶瓷,研究了高岭土和滑石粉包覆量对氧化铝空心球多孔陶瓷性能的影响。结果表明:随高岭土和滑石粉包覆量的增加,氧化铝空心球多孔陶瓷的相对密度、收缩率、抗弯强度和断裂韧性先减小后增大;当滑石粉和高岭土包覆量为11.5%(质量分数)时,氧化铝空心球多孔陶瓷的相对密度、线收缩率、抗弯强度和断裂韧性均分别达到最大值0.77、26%、177MPa和3.08MPa·m1/2。包覆后的氧化铝空心球多孔陶瓷的抗弯强度是未包覆的3倍。包覆适量高岭土和滑石粉明显改善了氧化铝空心球的界面结合强度。