MODELLING AND DYNAMIC ANALYSIS OF THREE-DIRECTION GRID PRESTRESSED RETICULATED MEGA-STRUCTURE

In this paper, the generation way of three-direction grid prestressed reticulated mega- structure is studied, and the three-direction grid prestressed reticulated mega-structure composite joint specific formation ideas are proposed. The important control parameters of three-direction grid prestressed reticulated mega-structure are determined, and the geometric modelling method of hexagon across the middle joint and octagon across the side joint is proposed. Coordinate formula of hexagonal and octagonal joints are derived to ensure reasonable grid arrangement and uniform stress distribution of the structure. Combined with the geometric parameters of the mega grid, a new method for creating the geometric model of three-direction grid prestressed mega reticulated structure is realized. The quadrangular pyramid space grid structure with the same length, span, rise and grid size and the three-direction grid prestressed grid structure are calculated, and the advantages of three-direction grid prestressed grid structure in dynamic performance are compared and analyzed

The Ginger-shaped Asteroid 4179 Toutatis: New Observations from a Successful Flyby of Chang'e-2

On 13 December 2012, Chang'e-2 conducted a successful flyby of the near-Earth asteroid 4179 Toutatis at a closest distance of 770 $\pm$ 120 meters from the asteroid's surface. The highest-resolution image, with a resolution of better than 3 meters, reveals new discoveries on the asteroid, e.g., a giant basin at the big end, a sharply perpendicular silhouette near the neck region, and direct evidence of boulders and regolith, which suggests that Toutatis may bear a rubble-pile structure. Toutatis' maximum physical length and width are (4.75 $\times$ 1.95 km) $\pm$10$\%$, respectively, and the direction of the +$z$ axis is estimated to be (250$\pm$5$^\circ$, 63$\pm$5$^\circ$) with respect to the J2000 ecliptic coordinate system. The bifurcated configuration is indicative of a contact binary origin for Toutatis, which is composed of two lobes (head and body). Chang'e-2 observations have significantly improved our understanding of the characteristics, formation, and evolution of asteroids in general.Comment: 21 pages, 3 figures, 1 tabl

Electrocatalytic Oxidation of Formic Acid on Pd/Ni Heterostructured Catalyst

通过两步还原法制备了Pd/Ni双金属催化剂.由于金属Pd原子在先行还原的Ni纳米粒子表面的外延生长以及其在Ni表面及Pd表面生长表现出的吉布斯自由能差异，最终导致了异结构Pd/Ni纳米粒子的形成.高分辨电子透射显微镜结果证实了异结构的存在，然而X射线衍射测量表明Pd/Ni纳米粒子具有类似于Pd的面心立方结构.制备的Pd/Ni纳米粒子与同等条件下合成的Pd纳米粒子相比对甲酸氧化呈现了更高的电催化活性，而且电催化稳定性也要明显优于纯Pd纳米粒子，证明Pd/Ni双金属催化剂是可选的直接甲酸燃料电池阳极催化剂.双金属催化剂对甲酸氧化电催化活性和稳定性增强可能是Ni原子的修饰改变了Pd粒子表面配位不饱和原子的电子结构所致.A Pd/Ni bimetallic nanostructured electrocatalyst was fabricated via a two-step reduction route. Owing to an epitaxial growth of Pd atoms on the surface of Ni nanoparticles, heterostructured Pd/Ni nanocomposites were formed and verified by high resolution transmission electron microscopy combined with energy-dispersion X-ray spectroscopy. X-ray diffraction confirmed that the as-prepared Pd/Ni nanocomposites possessed a single face-centered-cubic (fcc) Pd structure, probably due to a weaker diffraction intensity of metallic Ni and/or overlapping by that of Pd. The intrinsic catalytic activity on the Pd/Ni is higher than that on the Pd. Moreover, the durability of formic acid oxidation on the Pd/Ni was much enhanced over the Pd nanoparticles. The change in electronic structure of the surface coordination unsaturated Pd atoms and the possible dissolution of Ni species from the Pd/Ni heterostructure may account for such an improved durability for formic acid oxidation.This work was supported by the National Basic Research Program of China (973 Program) (No. 2012CB932800), the Natural Science Foundation of China (No. 21073219), Shanghai Science and Technology Committee (No. 11DZ1200400) and the Knowledge Innovation Engineering of the CAS (No. 12406, 124091231).This work was supported by the National Basic Research Program of China (973 Program) (No. 2012CB932800), the Natural Science Foundation of China (No. 21073219), Shanghai Science and Technology Committee (No. 11DZ1200400) and the Knowledge Innovation Engineering of the CAS (No. 12406, 124091231).作者联系地址：1. 中国科学院上海高等研究院，上海 201210；2. 中国科学院研究生院，北京 100039Author's Address: 1. Shanghai Advanced Research Institute, Chinese Academy of Sciences CAS, Shanghai 201210, China; 2. Graduate School of the CAS, Beijing 100039, China通讯作者E-mail：[email protected] & [email protected]

Hyperconjugated side chained benzodithiophene and 4,7-di-2-thienyl-2,1,3-benzothiadiazole based polymer for solar cells

A novel donor-acceptor (D-A) copolymer (P3TBDTDTBT), including hyperconjugated side chained benzodithiophene as a donor and 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTBT) as an acceptor, was designed and synthesized. Due to the introduction of the hyperconjugated side chain, the resultant polymer exhibited good thermal stability with a high decomposition temperature of 437 degrees C, a low band-gap of 1.67 eV with an absorption onset of 742 nm in the solid film, and a deep highest occupied molecular orbital (HOMO) energy level of -5.26 eV. Finally, the polymer solar cell (PSC) device based on this polymer and [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) showed the best power conversion efficiency (PCE) of 3.57% with an open-circuit voltage (V-oc) of 0.78 V, a short-circuit current density (J(sc)) of 8.83 mA cm(-2) and a fill factor (FF) of 53%

Protective effects of icariin extracted from epimedii herba on fetal rat hippocampal neurons

published_or_final_versionBiological SciencesMasterMaster of Philosoph

Binary Nitrogen Precursor-Derived Porous Fe-N-S/C Catalyst for Efficient Oxygen Reduction Reaction in a Zn-Air Battery

It is still a challenge to synthesize non-precious-metal catalysts with high activity and stability for the oxygen reduction reaction (ORR) to replace the state-of-the art Pt/C catalyst. Herein, a Fe, N, S co-doped porous carbon (Fe-NS/PC) is developed by using g-C3N4 and 2,4,6-tri(2-pyridyl)-1,3,5-triazine (TPTZ) as binary nitrogen precursors. The interaction of binary nitrogen precursors not only leads to the formation of more micropores, but also increases the doping amount of both iron and nitrogen dispersed in the carbon matrix. After a second heat-treatment, the best Fe/NS/C-g-C3N4/TPTZ-1000 catalyst exhibits excellent ORR performance with an onset potential of 1.0 V vs. reversible hydrogen electrode (RHE) and a half-wave potential of 0.868 V (RHE) in alkaline medium. The long-term durability is even superior to the commercial Pt/C catalyst. In the meantime, an assembled Zn-air battery with Fe/NS/C-g-C3N4/TPTZ-1000 as the cathode shows a maximal power density of 225 mW·cm−2 and excellent durability, demonstrating the great potential of practical applications in energy conversion devices

Experiment and Simulation Study of the Laser-Induced Cavitation Bubble Technique for Forming a Microgroove in Aluminum Foil

The present work introduces a laser-induced cavitation bubble technique for forming an axisymmetric structure (i.e., microgroove) and the dynamics of a cavitation bubble from initial expansion to the collapse stages that were also simulated. Furthermore, the shock wave signals and dynamic properties of the cavitation bubble were recorded using a hydrophone and a high-speed camera. The experiments on microgrooves formed by laser-induced cavitation bubble stamping were carried out, and the effects of laser energy, the initial position of the bubble, and the number of impacts on the microformability of aluminum sheets are discussed. The depth of the microgroove was investigated using experiments, and it was found that the process can serve as a rapid technique for impressing microfeatures on thin-sheet metals. The experimental results showed that as the initial position of the bubble increased, the deformation depth decreased. As the laser energy and number of impacts increased, the deformation depth increased. The results of the response surface experiments showed that a laser energy of 27 mJ, 3 impacts, and a bubble position of 3 mm were optimal for the process. By using the optimal parameters, flat and smooth microgrooves with a forming depth of 102.54 µm were successfully fabricated. Furthermore, the maximum thickness thinning of the microgroove section occurred at the entrance areas, and this area had the greatest hardness. This also indicated that the greatest amount of plastic deformation of the material and grain refinement occurred in this area. On the other hand, the aluminum foil did not undergo oxidation during the plastic deformation process. These results demonstrated that laser-induced bubble stamping is an advanced micromachining method with promising applications

Enantioselective 1,3-Dipolar Cycloaddition of Methylene­indolinones with α‑Diazomethyl­phosphonate to Access Chiral Spiro-phosphonyl­pyrazoline-oxindoles Catalyzed by Tertiary Amine Thiourea and 1,5-Diaza­bicyclo­[4.3.0]­non-5-ene

A methodology to access chiral 3,3′-spiro-phosphonyl­pyrazoline oxindoles via an asymmetric 1,3-dipolar cycloaddition reaction of substituted methylene­indolinones with α-diazomethyl­phosphonate in the catalysis of tertiary amine thiourea and 1,5-diaza­bicyclo­[4.3.0]­non-5-ene (DBN) has been established. This method exhibits high functional group compatibility, where a wide range of methylene­indolinones with various substituents and heterocyclic rings are accommodated by this reaction. The resulting chiral 3,3′-spiro-phosphonyl­pyrazoline oxindoles can be further transformed into spiro-phosphonyl­cyclo­propane oxindoles by ring contraction

Enantioselective 1,3-Dipolar Cycloaddition of Methylene­indolinones with α‑Diazomethyl­phosphonate to Access Chiral Spiro-phosphonyl­pyrazoline-oxindoles Catalyzed by Tertiary Amine Thiourea and 1,5-Diaza­bicyclo­[4.3.0]­non-5-ene

A methodology to access chiral 3,3′-spiro-phosphonyl­pyrazoline oxindoles via an asymmetric 1,3-dipolar cycloaddition reaction of substituted methylene­indolinones with α-diazomethyl­phosphonate in the catalysis of tertiary amine thiourea and 1,5-diaza­bicyclo­[4.3.0]­non-5-ene (DBN) has been established. This method exhibits high functional group compatibility, where a wide range of methylene­indolinones with various substituents and heterocyclic rings are accommodated by this reaction. The resulting chiral 3,3′-spiro-phosphonyl­pyrazoline oxindoles can be further transformed into spiro-phosphonyl­cyclo­propane oxindoles by ring contraction