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111.
Yenal Akgün Charis J. Gantes Konstantinos E. Kalochairetis Eleftheria E. Gkagka 《基于设计的结构力学与机械力学》2017,45(2):271-279
In this paper, a novel convertible stadium roof structure is introduced, which has been derived from a special geometric configuration of Watt-I linkage, a 1-DoF mechanism used in robot technologies as anthropomorphic fingers. The proposed structure can offer a wide range of different shape configurations according to the environmental conditions and spatial needs, thus offering several aesthetic and functional advantages over existing solutions. This paper serves as a feasibility investigation of this concept, mainly from geometric and structural point of view. To that affect, first kinematic analysis and geometric design of this linkage are introduced. Then, structural analyses of the proposed structure with realistic dimensions and loading conditions are performed in three different geometric configurations, in order to discuss strength and stiffness limitations. Finally, potential cover materials and actuators are briefly discussed. 相似文献
112.
添加剂PVP和MTS对合成Beta分子筛结构与性能的影响 《燃料化学学报》2017,45(4):468-474
分别以铝酸钠和硅溶胶为铝源和硅源,四乙基氢氧化铵为模板剂,在水热条件下,考察了添加剂(聚乙烯吡咯烷酮(PVP)和甲基三乙氧基硅烷(MTS))对合成Beta分子筛结构与性能的影响,并通过XRD、TEM、BET、ICP、~(29)Si-NMR和NH_3-TPD等方法对合成样品进行了结构表征和作用机理讨论,同时以催化裂化异丙苯为模型反应评价其催化性能。结果表明,与传统Beta分子筛相比,加入PVP后所得样品具有更高结晶度和较高的硅铝物质的量比(25.68)以及较大的比表面积(772 m~2/g);而加入MTS后尽管具有较大比表面积(657 m~2/g)和较高硅铝物质的量比(25.76),但是结晶度却相对降低,且粒径减小(160-320 nm)。两种添加剂作用下所得样品均具有更多酸量,在催化裂化异丙苯的反应中表现出较高的催化活性。 相似文献
113.
Efficient Synthesis of Cyclic Block Copolymers by Rotaxane Protocol by Linear/Cyclic Topology Transformation 下载免费PDF全文
Stephanie Valentina Dr. Takahiro Ogawa Dr. Kazuko Nakazono Dr. Daisuke Aoki Prof. Dr. Toshikazu Takata 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(26):8759-8762
High‐yielding synthesis of cyclic block copolymer (CBC) using the rotaxane protocol by linear‐cyclic polymer topology transformation was first demonstrated. Initial complexation of OH‐terminated sec‐ammonium salt and a crown ether was followed by the successive living ring‐opening polymerizations of two lactones to a linear block copolymer having a rotaxane structure by the final capping of the propagation end. CBC was obtained in a high yield by an exploitation of the mechanical linkage through the translational movement of the rotaxane component to transform polymer structure from linear to cyclic. Furthermore, the change of the polymer topology was translated into a macroscopic change in crystallinity of the block copolymer. 相似文献
114.
Dr. Chen Xue Shu Wang Prof. Dr. Wen-Long Liu Prof. Dr. Xiao-Ming Ren 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(20):5280-5287
A direct band gap 2D corrugated layer lead chloride hybrid, [(CH3)4N]4Pb3Cl10 ( 1 ), shows analogous topology to the {Mg3F104−}∞ layer in Cs4Mg3F10, and with the (CH3)4N+ cations locating in the inorganic layer voids and between the interlayers. Two reversible structural phase transitions occur in 1 at 225/210 K and 328/325 K upon heating/cooling, respectively. On going from the low- to intermediate-temperature phase, the space group changes from P21/c to Cmca, and the crystallographic axis perpendicular to the layers is doubled with the order–disorder transformation of (CH3)4N + cations between the interlayers. The intermediate- and high-temperature phases are isomorphic with similar cell parameters and packing structure; their main difference concerns the disorder degree of the (CH3)4N + cations between the interlayers. The two-step structural phase transitions lead to dielectric anomalies around the corresponding Tc. Interestingly, 1 shows multiband emission, originating from the recombination of exciton and emission of defects. Moreover, 1 exhibits divergent thermochromic luminescent features around the Tc on the intermediate to low temperature transition. 相似文献
115.
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117.
Zenghui Yang Fuzhi Song Qihua Wang Tingmei Wang 《Journal of polymer science. Part A, Polymer chemistry》2016,54(24):3858-3867
In this work, two kinds of high temperature shape memory copolyimides were prepared and the shape memory cycles induced structural evolution of macromolecular chains was investigated in detail. The glass transition temperature (Tg) of poly(benzoxazole‐co‐imide) (PI1) and poly(benzimidazole‐co‐imide) (PI2) are 280 °C and 355 °C, respectively. The results show that PI1 could keep stable macromolecular chain structure under shape memory cycles and exhibit outstanding shape memory performance (Rf > 98%, Rr > 97%) under different stretch condition. Whereas, shape memory cycles induced orientation with more ordered macromolecular chains packing is formed for PI2 after several thermal mechanical cycles, which strongly affect physical crosslinking points, thermal mechanical properties as well as shape memory behaviors. The study on macroscopic property and microscopic structure evolution will promote a better understanding of the shape memory effect of polyimides and accelerate development of high performance polyimides for shape memory applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3858–3867 相似文献
118.
Heinz Jagodzinski 《Phase Transitions》2013,86(1-4):231-237
The method of Fourier transforms is applied to the calculation of sharp (coherent) and diffuse (incoherent) scattering of modulated structures and quasicrystals. It is shown that the fundamental difference between both may best be described by introducing different distribution functions of atoms, before applying modulations of the structure. 相似文献
119.
Wenbin Zhang Siru Guo Prof. Shujuan Han Prof. Zhihua Yang Prof. Shilie Pan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(47):12047-12051
The first mixed calcium zinc borate with a new fundamental building block (FBB) [B8O17], Ca1.13Zn0.87B8O14 has been successfully synthesized. It exhibits two independent interpenetrating three-dimensional B−O anion networks constructed by [B8O17] groups, enriching the structural diversity of B−O configurations. In particular, the UV-Vis-NIR diffuse-reflectance spectrum shows that it has a short UV cutoff edge (<195 nm). 相似文献
120.
Yu. D. Fomin 《Molecular physics》2019,117(20):2786-2792
ABSTRACTHeat capacity of several liquids which demonstrate anomalous behaviour is studied. It is shown that isochoric heat capacity of these liquids shows anomalously high values which is related to smooth structural crossover in these liquids. This phenomenon can be used for qualitative explanation of high heat capacity of water and some other substances. 相似文献