Evaluation of the surface tension measurement of axisymmetric drop shape analysis (ADSA) using a shape parameter

A quantitative criterion called “shape parameter” to evaluate the quality of surface tension measurement of Axisymmetric Drop Shape Analysis (ADSA) is presented. ADSA is a powerful technique for the measurement of interfacial tensions and contact angles of pendant drops, sessile drops, and bubbles. Despite the general success of ADSA, deficient results may be obtained for drops close to spherical shape. Therefore, the “shape parameter” was used to determine the range of drop shapes in which ADSA succeeds or fails. The “shape parameter” is a dimensionless parameter that expresses quantitatively the difference in shape between a given experimental profile and an inscribed circle. The surface tension measurements of ADSA were evaluated for both pendant drop and constrained sessile drop configurations using the shape parameter. Different shapes of the pendant drop were studied using different sizes and materials of holders. For each drop configuration, a “critical shape parameter” was defined based on the minimum value of the shape parameter that guarantees an error of less than ±0.1 mJ/m². Furthermore, the effects of the type of liquid and constellation on the “critical shape parameter” were studied.     

Design,Synthesis, and Optical/Electronic Properties of a Series of Sphere-Rod Shape Amphiphiles Based on the C60-oligofluorene Conjugates

A series of sphere-rod shape amphiphiles were designed and synthesized by connecting the rod-like oligofluorenes with different lengths(OF_n) to the different positions of the spherical [60]fullerene(C_(60)) through a rigid linkage. The conjugates were characterized by ~1H-NMR, ~(13)C-NMR, FTIR, EA and MALDI-TOF mass spectrometry. The optical and electronic properties of the conjugates were studied by UV-Vis absorption spectroscopy, fluorescence spectrometry, and cyclic voltammetry. The results from UV-Vis absorption spectroscopy and cyclic voltammetry indicated that the energy profiles of C_(60) and OF_n remained unchanged when different lengths of OF_n were attached to C_(60). The electron affinities of the OF_n-C_(60) conjugates were close to that of C_(60), while slight electronic interaction was found between the two individual chromophores(C_(60) and OF_n) in their ground states. The fluorescence spectra exhibited a complete fluorescence quenching in the toluene solution, suggesting an effective energy transfer from OF_n to C_(60). It presents a systematic study on the selfassembly, structure-property relationship, and potential technical applications of the conjugates.     

聚甲基丙烯酸甲酯/星形聚乙二醇半互穿聚合物网络的形状记忆性能和分子机理

采用非共价复合方法,设计并合成了具有星形结构的聚甲基丙烯酸甲酯/星形聚乙二醇半互穿聚合物网络(PMMA/SPEG)和聚甲基丙烯酸甲酯/线性聚乙二醇半互穿聚合物网络(PMMA/LPEG).研究了PEG分子量对PMMA/SPEG和PMMA/LPEG的热性能、机械性能、动态机械性能和形状记忆性能的影响.结果表明,与PMMA/LPEG相比,星形结构的嵌入显著提高了PMMA/SPEG复合物的机械性能、形状回复率和回复速度.采用Edwards管道模型理论对其形状记忆效应的分子机理进行了阐释,利用材料的应力松弛特性对机理分析进行了验证.     

Stress-Strain Behavior of Shape Memory Polymers by 1WE Method: Application to Tecoflex®

Thermomechanical cycles including programming, cooling, unloading and heating to trigger the 1WE were examined for a shape memory polymer (SMP), Tecoflex® (TFX EG-72D). Cycles were performed at 60°C with 50% and 225% strains and the recovery time of 10 min. Strains evolving with time were estimated during the thermomechanical treatments for the total 44 cycles using 50% strains and the total 50 cycles using 225% strains. Recovery ratios for 50% strains and 225% were also estimated. It turns out that programming, cooling, unloading and heating to trigger the 1WE causes an increase of irreversible strain and is associated with a corresponding decrease of the intensity of the 1WE in particular during the first thermomechanical cycles. In parallel scanning electron microscopic study using secondary electron imaging shows a very slight wavy surface structure evolved during cycling.     

Existence analysis of an optimal shape design problem with non coercive state equation

In this paper, a shape optimization problem, modelling a welding process, governed by a second order non coercive PDE is considered. The well posedness of the shape optimal design problem is showed using the degree of Leray–Schauder. Then the existence of an optimal solution is proved.     

Comparison of two-dimensional integration methods for shape reconstruction from gradient data

As a requisite and key step in some gradient-based measurement techniques, the reconstruction of the shape, more generally the scalar potential, from the measured gradient data has been studied for many years. In this work, three types of two-dimensional integration methods are compared under various conditions. The merits and drawbacks of each integration method are consequently revealed to provide suggestions in selection of a proper integration method for a particular application.     

Molecular Shape Analysis of a Maillard Reaction Intermediate

Abstract

The Maillard (browning) reaction involving the polycondensation of sugars and amino acids is believed to be an important abiotic pathway for humic substance formation in nature. However, a major drawback is that the Maillard reaction is extremely slow at temperatures encountered under normal environmental conditions. In order to elucidate some details of this process molecular shape analysis was applied to investigate the initial reaction between D-glucose and glycine to form the Amadori compound fructosylglycine which is an intermediate product in the Maillard reaction. The structure of the Amadori compound was optimized at a quantum mechanical level and its ground state electron energy calculated. Molecular Iso-Density Contours (MIDCO's), electron density contour surfaces of constant electron density, were constructed for D-glucose, glycine and fructosylglycine in order to study the steric conditions for the reaction. The calculations indicate that the Amadori compound and water on one hand and the separate entities D-glucose and glycine on the other hand are very similiar to each other in terms of their ground state energy. This agrees with the experimental observation that the reaction between D-glucose and glycine to form the Amadori compound is slow.     

Inducing a high twisted conformation in the polyimide structure by bulky donor moieties for the development of non-volatile memory

Two polyimides, PI(DAT-6FDA) and PI(DAPT-6FDA), from N-(2,4-diaminophenyl)-N,N-diphenylamine (DAT) or N-(4-(2′,4′-diaminophenoxy)phenyl-N,N-diphenylamine (DAPT) and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) were prepared to clarify the structural effect on the resulting memory properties. The memory device based on PI(DAT-6FDA) showed an unstable volatile behavior, while the device based on PI(DAPT-6FDA) with a more bulky donor (D) unit exhibited a stable non-volatile FLASH type memory characteristic with a long retention time over 10⁴ s. The theoretical simulation based on the density functional theory (DFT) suggested that the greater distinct charge separation between the ground and charge transfer (CT) states led to a highly stable memory behavior. Also, it was clarified that PI(DAPT-6FDA) had a highly twisted conformation compared to PI(DAT-6FDA) in the ground state, and a more twisted dihedral angle between the D and acceptor (A) units was induced in the CT state, which led to the non-volatile memory characteristic.     

碱性电解液中K3[Fe(CN)6]在锌阳极上的自发还原和吸附延长锌镍电池的循环寿命

采用K₃[Fe(CN)₆]作为锌镍电池的电解液添加剂,克服了锌阳极的变形。此外,通过一系列实验设计和表征,探索了电解液中金属锌与K₃[Fe(CN)₆]的反应机理。通过XRD (X-ray diffraction)和XPS (X-ray photo-electron spectroscopy)测试,我们发现金属锌在KOH水溶液中能够与K₃[Fe(CN)₆]反应,将[Fe(CN)₆]^3–还原为[Fe(CN)₆]⁴⁻。添加K₃[Fe(CN)₆]的锌镍电池实现了更长的循环寿命,比不添加K₃[Fe(CN)₆]的锌镍电池长3倍以上。在相同循环次数下,改性电解质中锌阳极循环不仅形状变化较小,而且没有出现“死”锌现象,电极添加剂和粘结剂也没有发生偏析。此外,不同于一般的有机添加剂,K₃[Fe(CN)₆]的加入不仅不会增大电极的极化,还能够提高锌镍电池的放电容量和倍率性能。因此,考虑到这一改性策略有着较高的可行性和较低的成本,K₃[Fe(CN)₆]添加剂在锌镍电池的实际应用中具有极大的推广潜力。