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991.
本文提出了一个新的厚薄板通用的三角形板弯元,根据Hellinger-Reissner变分原理推导出来的新单元具有独立的转角、位移、剪应变和弯曲应变的插入函数,它没有其它混合元所存在的一些缺点。一些典型例子表明这个新单元具有很好的特性,刚度矩阵简单,计算精度高,收敛速度快以及厚薄板通用性强。 相似文献
992.
This article focuses on the formulation of a hysteretic model used as anisolator restoring force model. The proposed model is based on operatorgoverning input and output functions that depend on the deflection andthe restoring force of the isolator. First, the mathematical formulationis demonstrated, then the hysteretic model proposed is applied toisolators having different types of behavior. The model parameters aresought using the experimental force-deflection loop of each of theisolators studied. Next, the transient response of a flexible structuremounted on an all-metal isolator is predicted by coupling the firstorder differential equation of the restoring force and the second orderdifferential equations of the structure's motion. The experimentalinvestigation validates the proposed hysteretic model applied to theall-metal mount. 相似文献
993.
Regulating Molecular Recognition with C‐Shaped Strips Attained by Chirality‐Assisted Synthesis 下载免费PDF全文
Dr. Xiaoxi Liu Zackariah J. Weinert Mona Sharafi Dr. Chenyi Liao Prof. Jianing Li Prof. Severin T. Schneebeli 《Angewandte Chemie (International ed. in English)》2015,54(43):12772-12776
Chirality‐assisted synthesis (CAS) is a general approach to control the shapes of large molecular strips. CAS is based on enantiomerically pure building blocks that are designed to strictly couple in a single geometric orientation. Fully shape‐persistent structures can thus be created, even in the form of linear chains. With CAS, selective recognition between large host and guest molecules can reliably be designed de novo. To demonstrate this concept, three C‐shaped strips that can embrace a pillar[5]arene macrocycle were synthesized. The pillar[5]arene bound to the strips was a better host for electron‐deficient guests than the free macrocycle. Experimental and computational evidence is provided for these unique cooperative interactions to illustrate how CAS could open the door towards the precise positioning of functional groups for regulated supramolecular recognition and catalysis. 相似文献
994.
Dr. Arik Kar Sumanta Sain Dr. Simanta Kundu Arka Bhattacharyya Dr. Swapan Kumar Pradhan Prof. Amitava Patra 《Chemphyschem》2015,16(5):1017-1025
Tuning the functional properties of nanocrystals is an important issue in nanoscience. Here, we are able to tune the photocatalytic properties of SnO2 nanocrystals by controlling their size and shape. A structural analysis was carried out by using X‐ray diffraction (XRD)/Rietveld and transmission electron microscopy (TEM). The results reveal that the number of oxygen‐related defects varies upon changing the size and shape of the nanocrystals, which eventually influences their photocatalytic properties. Time‐resolved spectroscopic studies of the carrier relaxation dynamics of the SnO2 nanocrystals further confirm that the electron–hole recombination process is controlled by oxygen/defect states, which can be tuned by changing the shape and size of the materials. The degradation of dyes (90 %) in the presence of SnO2 nanoparticles under UV light is comparable to that (88 %) in the presence of standard TiO2 Degussa P‐25 (P25) powders. The photocatalytic activity of the nanoparticles is significantly higher than those of nanorods and nanospheres because the effective charge separation in the SnO2 nanoparticles is controlled by defect states leading to enhanced photocatalytic properties. The size‐ and shape‐dependent photocatalytic properties of SnO2 nanocrystals make these materials interesting candidates for photocatalytic applications. 相似文献
995.
Cyclotetrabenzoin: Facile Synthesis of a Shape‐Persistent Molecular Square and Its Assembly into Hydrogen‐Bonded Nanotubes 下载免费PDF全文
Qing Ji Ha T. M. Le Dr. Xiqu Wang Dr. Yu‐Sheng Chen Dr. Tatyana Makarenko Prof. Allan J. Jacobson Prof. Ognjen Š. Miljanić 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(48):17205-17209
Cyanide‐catalyzed benzoin condensation of terephthaldehyde produces a cyclic tetramer, which we propose to name cyclotetrabenzoin. Cyclotetrabenzoin is a square‐shaped macrocycle ornamented with four α‐hydroxyketone functionalities pointing away from the central cavity, the dimensions of which are 6.9×6.9 Å. In the solid state, these functional groups extensively hydrogen bond, resulting in a microporous three‐dimensional organic framework with one‐dimensional nanotube channels. This material exhibits permanent—albeit low‐porosity, with a Langmuir surface area of 52 m2 g?1. Cyclotetrabenzoin’s easy and inexpensive synthesis and purification may inspire the creation of other shape‐persistent macrocycles and porous molecular crystals by benzoin condensation. 相似文献
996.
997.
《Macromolecular rapid communications》2017,38(4)
Multistimuli‐responsive shape‐memory polymers are highly desirable in various applications, and numerous modes have been developed in recent years. However, most of them need to reprogram before they are ready to respond to another stimulus while one is triggered. Here, a new strategy is developed to achieve dual‐stimuli‐responsive triple‐shape memory with non‐overlapping effect in one programming cycle. Here, a series of poly(l ‐lactide)‐poly(tetramethylene oxide) glycol copolymers (PLA‐PTMEG‐A) is prepared by selected dangling photoresponsive anthracene moieties on the crystalline PTMEG backbone. The architectures of the copolymers are well‐controlled in order to keep a good balance between the crystallinity of the soft segment and the mobility of the anthracene moieties. Thus, PLA‐PTMEG‐A's can respond to heat and light with non‐overlapping effect. The thermally‐induced shape‐memory effect (TSME) is realized by the crystallization–melting transition of PTMEG soft segments, while the light‐induced shape‐memory effect (LSME) is achieved by the reversible photodimerization of anthracene groups. In view of the non‐overlapping effect of TSME and LSME in the copolymers, a triple‐shape‐memory effect triggered by dual‐stimuli is realized in one programming and recovery cycle.
998.
999.
1000.
In this paper, we obtain that multilinear Calderón-Zygmund operators and their commutators with BMO functions are bounded on products of Herz-Morrey spaces with variable smoothness and integrability. The vector-valued setting of multilinear Calderón-Zygmund operators is also considered. 相似文献