Progress in the production and modification of PVDF membranes

Recent developments of zinc oxide based photocatalyst in water treatment technology: A review

The stability of two-dimensional (2D) layers and membranes is subject of a long standing theoretical debate. According to the so called Mermin-Wagner theorem, long wavelength fluctuations destroy the long-range order for 2D crystals. Similarly, 2D membranes embedded in a 3D space have a tendency to be crumpled. These dangerous fluctuations can, however, be suppressed by anharmonic coupling between bending and stretching modes making that a two-dimensional membrane can exist but should present strong height fluctuations. The discovery of graphene, the first truly 2D crystal and the recent experimental observation of ripples in freely hanging graphene makes these issues especially important. Beside the academic interest, understanding the mechanisms of stability of graphene is crucial for understanding electronic transport in this material that is attracting so much interest for its unusual Dirac spectrum and electronic properties. Here we address the nature of these height fluctuations by means of straightforward atomistic Monte Carlo simulations based on a very accurate many-body interatomic potential for carbon. We find that ripples spontaneously appear due to thermal fluctuations with a size distribution peaked around 70 \AA which is compatible with experimental findings (50-100 \AA) but not with the current understanding of stability of flexible membranes. This unexpected result seems to be due to the multiplicity of chemical bonding in carbon.

Intrinsic ripples in graphene

Piezoresistive sensors are among the earliest micromachined silicon devices. The need for smaller, less expensive, higher performance sensors helped drive early micromachining technology, a precursor to microsystems or microelectromechanical systems (MEMS). The effect of stress on doped silicon and germanium has been known since the work of Smith at Bell Laboratories in 1954. Since then, researchers have extensively reported on microscale, piezoresistive strain gauges, pressure sensors, accelerometers, and cantilever force/displacement sensors, including many commercially successful devices. In this paper, we review the history of piezoresistance, its physics and related fabrication techniques. We also discuss electrical noise in piezoresistors, device examples and design considerations, and alternative materials. This paper provides a comprehensive overview of integrated piezoresistor technology with an introduction to the physics of piezoresistivity, process and material selection and design guidance useful to researchers and device engineers.

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Review: Semiconductor Piezoresistance for Microsystems

Journal of Applied physics,Vol.33 : 1962年に発表されたレオロジー関連の論文

The effects of flow velocity on the vibration frequency and mode shape of the fluid-conveying single-walled carbon nanotube are analyzed using nonlocal elastic theory. Results show that the frequency and mode shape are significantly influenced by the nonlocal parameter e0a/L. Increasing the nonlocal parameter decreases the real component of frequency and the decrease is more obvious for a lower flow velocity and a higher-order mode. In addition, a higher mode shape is observed with increasing the value of e0a/L. When a critical flow velocity is reached, the combination of first and second modes takes place. The mode shape for the combination is large relative to mode 3 due to the coupled frequency effect, especially including negative imaginary frequency. Furthermore, the mode shape of the combination increases as the nonlocal effect increases.

Free transverse vibration of the fluid-conveying single-walled carbon nanotube using nonlocal elastic theory

This paper analyzes the influences of nonlocal effect, viscosity effect, aspect ratio, and elastic medium constant on the fundamental frequency of a viscous-fluid-conveying single-walled carbon nanotube (SWCNT) embedded in an elastic medium. According to the analysis, the results show that the nonlocal effect on the frequency becomes significant as the flow velocity of viscous fluid decreases. As the value of dimensionless nonlocal parameter decreases, the frequency of SWCNT increases under the same velocity conditions. In addition, the viscosity effect on the frequency of SWCNT becomes significant as the flow velocity of viscous fluid increases. Under the same velocity conditions, the frequency increases as the values of the viscous parameter, the aspect ratio, and the elastic medium constant increase. Furthermore, it can also be found that a SWCNT embedded in a stiff matrix with a large aspect ratio conveying a highly viscous fluid makes the phenomenon of vibration-induced flutter instability delay to occur until a higher flow velocity.

Win-Jin Chang

Papers

Free transverse vibration of the fluid-conveying single-walled carbon nanotube using nonlocal elastic theory

Vibration analysis of a viscous-fluid-conveying single-walled carbon nanotube embedded in an elastic medium

Effects of AFM-based nanomachining process on aluminum surface

Nanomechanical properties of copper thin films on different substrates using the nanoindentation technique

Free vibration of a single-walled carbon nanotube containing a fluid flow using the Timoshenko beam model