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121.
A hydrogel is a polymer network that can absorb a large quantity of solvent and swell due to a physical or chemical stimulus. Hydrogels are more and more used as smart materials in recent micro-applications. This fact requires the development of adequate models and simulation tools for their large deformation behavior. These models must also predict the onset of instabilities, such as folding or creasing. In this work, we study an interesting application of adaptive optical microsystem using a previously developed theory of inhomogeneous large deformation of a pH-sensitive hydrogel. The devices function is based on the swelling of a ring made of a pH-sensitive hydrogel. The latter controls the focal length of the liquid microlens. Our aim is to analyze major design parameters that affect the hydrogel ring behavior and the function of the micro-optical device. The problem is solved numerically with the finite element commercial software ABAQUS. Various modes of large deformation and the influence of the rings aspect ratio on the behavior of the micro-device are investigated. Results show that, for relatively short rings, a stable swelling takes place. Rings with a relatively big aspect ratio can have an unstable swelling with the propagation of a creasing instability. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
122.
Jian Zhu Shengqiang Cai Zhigang Suo 《International Journal of Solids and Structures》2010,47(24):3254-3262
This paper analyzes a membrane of a dielectric elastomer, prestretched and mounted on a rigid circular ring, and then inflated by a combination of pressure and voltage. Equations of motion are derived from a nonlinear field theory, and used to analyze several experimental conditions. When the pressure and voltage are static, the membrane may attain a state of equilibrium, around which the membrane can oscillate. The natural frequencies can be tuned by varying the prestretch, pressure, or voltage. A sinusoidal pressure or voltage may excite superharmonic, harmonic, and subharmonic resonance. Several modes of oscillation predicted by the model have not been reported experimentally, possibly because these modes have small deflections, despite large stretches. 相似文献
123.
Immersed in an ionic solution, a network of polyelectrolytes imbibes the solution and swells, resulting in a polyelectrolyte gel. The swelling is reversible, and the amount of swelling is regulated by ionic concentrations, mechanical forces, and electric potentials. This paper develops a field theory to couple large deformation and electrochemistry. A specific material model is described, including the effects of stretching the network, mixing the polymers with the solvent and ions, and polarizing the gel. We show that the notion of osmotic pressure in a gel has no experimental significance in general, but acquires a physical interpretation within the specific material model. The theory is used to analyze several phenomena: a gel swells freely in an ionic solution, a gel swells under a constraint of a substrate, electric double layer at the interface between the gel and the external solution, and swelling of a gel of a small size. 相似文献
124.
在考虑齿轮时变啮合刚度的情况下,建立了齿轮耦合的转子-轴承系统的非线性动力学模型,用数值仿真法研究系统的稳态不平衡响应时发现,由于齿轮时变啮合刚度的影响。在系统响应中,不但会出现对应于啮合频率的响应分量,而且在某种条件下,该分量甚至超过基频分量;一个转子上的不平衡质量不仅会对本身产生激励,而且也会对其它转子产生激励。 相似文献
125.
126.
Three C60‐carbazole adducts have been synthesized by 1, 3‐dipolar cycloaddition reaction. Intramolecular energy/electron transfer from carbazole to C60 was observed by steady‐state absorption and fluorescence spectra. The fluorescence spectra of these adducts were similar to each other and dependent on the excitation wavelength and solvent. 相似文献
127.
对屠畜肉市场检验中淋巴结的选定、常见病畜肉中淋巴结的变化特征及淋巴结检查在屠畜肉检验中的重要价值作了论述 相似文献
128.
129.
FeZSM-5/N2O催化氧化苯制苯酚 总被引:10,自引:1,他引:9
苯一步氧化制苯酚,是有机物氧化合成中富有挑战性的研究课题之一。该文着重论述了在FeZSM-5及其一系列沸石催化剂上,应用氧化亚氮作为氧化剂使苯直接氧化制苯酚的研究进展。这一系列催化剂体系的特殊之处在于通过氧化亚氮在沸石分子筛上的分解获得具有催化活性的a-氧。详细讨论了在沸石分子筛上形成特殊结构的铁氧化物作为催化活性中心这一观点。由于这种催化体系对苯直接氧化制苯酚的反应有着很高的选择性,因此,这种比较经济和安全的制备苯酚的方法引起了人们的广泛关注。 相似文献
130.
Age of granulite from Huangtuling, Dabie Mountain: Pb-Pb dating of garnet by a stepwise dissolution technique 总被引:9,自引:0,他引:9
Hanwen Zhou Xianhua Li Ying Liu Zhendong You Shutian Suo Zengqiu Zhong 《科学通报(英文版)》1999,44(10):941-941
A new stepwise dissolution scheme, involving acids with different properties, enables the selective recovery of radiogenic
and common Pb from a mineral, and makes single-mineral Pb-Pb dating possible. Garnet from a granulite sample from Huangtuling,
northern Dabie Mountain yields a Pb-Pb isochron age of (1998 ±35) Ma, which is interpreted as the timing of peak metamorphism
of granulite facies. 相似文献