PVDF压电薄膜在应力波测量中的应用

综合介绍了PVDF压力传感器的测试原理、动态标定实验，并采用定制的PVDF压力传感器测量了不同类型分层介质在冲击载荷作用下的压力衰减，说明了PVDF压力传感器在压力测量中有着很好的前景．     

低密度开孔泡沫材料力学模型的理论研究进展

开孔泡沫材料主要用于隔音、减振和填充方面，对其力学行为进行理论描述，探讨力学性能与密度及复杂微结构的关系具有十分重要的学术价值和工程意义．为了促进国内泡沫材料力学的发展和交流，文中对低密度开孔泡沫材料力学模型的研究历史进行了简要回顾，重点介绍了能较好地反映开孔泡沫材料真实胞体结构特点的十四面体胞体模型和随机胞体模型，并报道了近年来基于十四面体胞体模型和随机胞体模型研究低密度开孔泡沫材料力学行为的一些理论工作、同时，也对国内的一些相关研究情况进行了简要评述，指出了该领域今后的一些研究方向．     

聚氨酯泡沫塑料压缩杨氏模量的理论预测

通过微分法导出了泡沫塑料剪切模量和体积模量所满足的微分方程组，再利用联系泡沫塑料泊松比和孔隙比的Ｋｅｒｎｅｒ－Ｒｕｓｃｈ经验关系及泡沫塑料弹性常数间满足足的关系，在基体材料不可压缩的假设下，确定了泡沫塑料的杨氏模量。本文针对几种密度的泡沫塑料，分别对它们的杨氏模量进行了理论预测和实验测定，结果表明：理论预测的模量在较高密度下与实验符合的很好，在低密度下也给出相当好的近似值。此外，本文的结果同其他理     

Meltable Spin Transition Molecular Materials with Tunable Tc and Hysteresis Loop Width

Herein, we report a way to achieve abrupt high‐spin to low‐spin transition with controllable transition temperature and hysteresis width, relying not on solid‐state cooperative interactions, but utilizing coherency between phase and spin transitions in neutral Fe^II meltable complexes.     

Programmable Engineering of a Biosensing Interface with Tetrahedral DNA Nanostructures for Ultrasensitive DNA Detection

Self‐assembled DNA nanostructures with precise sizes allow a programmable “soft lithography” approach to engineer the interface of electrochemical DNA sensors. By using millimeter‐sized gold electrodes modified with several types of tetrahedral DNA nanostructures (TDNs) of different sizes, both the kinetics and thermodynamics of DNA hybridization were profoundly affected. Because each DNA probe is anchored on an individual TDN, its lateral spacing and interactions are finely tuned by the TDN size. By simply varying the size of the TDNs, the hybridization time was decreased and the hybridization efficiency was increased. More significantly, the detection limit for DNA detection was tuned over four orders of magnitude with differentially nanostructured electrodes, and achieved attomolar sensitivity with polymeric enzyme amplification.     

Sol-Gel Microspheres Doped with Glycerol: A Structural Insight in Light of Forthcoming Applications in the Polyurethane Foam Industry

Porous silica-based microspheres encapsulating aqueous glycerol can be potential curing agents for one-component foams (OCFs). Such agents have the advantage of an enhanced sustainability profile on top of being environmentally friendly materials. A synthetically convenient and scalable sol-gel process was used to make silica and organosilica microspheres doped with aqueous glycerol. These methyl-modified silica microspheres, named “GreenCaps”, exhibit remarkable physical and chemical stability. The microspheres were characterized by scanning electron microscopy, transmission electron microscopy at reduced pressure, and cryogenic nitrogen adsorption—desorption analysis. The structure of the materials was also analyzed at the molecular level by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. As expected, the degree of methylation affects the degree of encapsulation and pore structure. Microspheres similarly methylated, however, can differ considerably in surface area and pore size due to the templating effect of glycerol on the organosilica structure. The results of the structure analysis reveal that glycerol is efficiently encapsulated, acts as a template, barely leaches over time, but is released by depressurization. A proper application of these microspheres can later on enhance both the environmental and health profile, as well as the technical performance (curing speed, foam quality, and froth thixotropy) of spray polyurethane foams.     

A comparison between parallelization approaches in molecular dynamics simulations on GPUs

We test the relative performances of two different approaches to the computation of forces for molecular dynamics simulations on graphics processing units. A “vertex‐based” approach, where a computing thread is started per particle, is compared to an “edge‐based” approach, where a thread is started per each potentially non‐zero interaction. We find that the former is more efficient for systems with many simple interactions per particle while the latter is more efficient if the system has more complicated interactions or fewer of them. By comparing computation times on more and less recent graphics processing unit technology, we predict that, if the current trend of increasing the number of processing cores—as opposed to their computing power—remains, the “edge‐based” approach will gradually become the most efficient choice in an increasing number of cases. © 2014 Wiley Periodicals, Inc.     

Direct On‐Surface Patterning of a Crystalline Laminar Covalent Organic Framework Synthesized at Room Temperature

We report herein an efficient, fast, and simple synthesis of an imine‐based covalent organic framework (COF) at room temperature (hereafter, RT‐COF‐1 ). RT‐COF‐1 shows a layered hexagonal structure exhibiting channels, is robust, and is porous to N₂ and CO₂. The room‐temperature synthesis has enabled us to fabricate and position low‐cost micro‐ and submicropatterns of RT‐COF‐1 on several surfaces, including solid SiO₂ substrates and flexible acetate paper, by using lithographically controlled wetting and conventional ink‐jet printing.     

A novel method to prepare microcellular poly(vinyl alcohol) foam based on thermal processing and supercritical fluid

Combining the thermal processing and supercritical fluid technology develops a novel preparation method of microcellular poly(vinyl alcohol) (PVA). Water, as the plasticizer in system, can form the hydrogen bonding with pendant hydroxyl of PVA and weaken its strong intermolecular and intramolecular forces to realize the thermal processing. Supercritical carbon dioxide (sc‐CO₂) can easily dissolve into water‐plasticized PVA (WPVA) because of the destruction of crystal region caused by water, and the enhanced sc‐CO₂ solubility can greatly improve the foamability of WPVA. The porous structure generates through the saturation of sc‐CO₂ in WPVA sample and followed by pressure drop‐induced phase separation. The foaming behavior of WPVA was studied as a function of saturation pressure, foaming temperature, and saturation time. The cell density, cell size, and distribution of the obtained foam can be controlled by tuning processing conditions. The results revealed that the cell size decreased, and its distribution narrowed with saturation pressure increasing, or decrease of foaming temperature. But excessively increasing the saturation time generated a negative effect on the foaming behavior owing to the deteriorated plasticization effect resulted from the loss of water. Copyright © 2016 John Wiley & Sons, Ltd.