Synthesis and Properties of Trimethylphenoxy- and Tetramethylphenoxy-Silanes

Twelve new Trimethylphenoxy- and Tetramethylphenoxy-silanes were synthesized and all were proved to be stable toward hydrolysis. The substituent effect of methyl groups on the stability of Si-O-Ar toward hydrolysis is also discussed.     

Analysis of Long-Term Optical Effects in Double-Coated Optical Fibers Induced by Hydrostatic Pressure and Thermal Loading

The hydrostatic pressure and thermal loading simultaneously induced optical effects in double-coated optical fibers in the long-term are analyzed by the viscoelastic theory. Using the Laplace transformation method, close-form solutions for the microbending loss and refractive index changes are obtained. The results of the microbending loss are initially identical to those obtained by the elastic analysis, and then decrease gradually as time progresses. The microbending loss and refractive index changes of the glass fiber are functions of the material properties of the primary and secondary coatings. To minimize the microbending loss and refractive index changes in the long-term, the Young's modulus of the primary coating, and the viscosity and Poisson's ratio of the secondary coating should be increased. Nevertheless, the viscosity and Poisson's ratio of the primary coating, and the Young's modulus of the secondary coating should be decreased.     

L- and U-shaped heat pipes thermal modules with twin fans for cooling of electronic system under variable heat source areas

This study utilizes a versatile superposition method with thermal resistance network analysis to design and experiment on a thermal module with embedded six L-shaped or two U-shaped heat pipes and plate fins under different fan speeds and heat source areas. This type of heat pipes-heat sink module successively transfer heat capacity from a heat source to the heat pipes, the heat sink and their surroundings, and are suitable for cooling electronic systems via forced convection mechanism. The thermal resistances contain all major components from the thermal interface through the heat pipes and fins. Thermal performance testing shows that the lowest thermal resistances of the representative L- and U-shaped heat pipes-heat sink thermal modules are respectively 0.25 and 0.17 °C/W under twin fans of 3,000 RPM and 30 × 30 mm² heat sources. The result of this work is a useful thermal management method to facilitate rapid analysis.     

Resonance frequency of chiral single-walled carbon nanotubes using Timoshenko beam theory

This Letter develops a model that analyzes the resonant frequency of the chiral single-walled carbon nanotubes (SWCNTs) subjected to a thermal vibration by using Timoshenko beam model, including the effect of rotary inertia and shear deformation. The analytical solution is derived and the frequency equation is obtained. The results based on the beam model show that the frequency increases with decreasing the nanotube aspect ratio of length to diameter. In addition, the frequency obtained by Timoshenko beam model is lower than that calculated by Euler beam model. As the nanotube aspect ratio of length to diameter decreased, the discrepancy is more obvious. Furthermore, as the effect of thermal vibration increases, the frequency for chiral SWCNTs decreases.     

Longitudinal vibration of cracked nanobeams using nonlocal elasticity theory

The aim of this paper is to study the longitudinal frequency of a cracked nanobeam. The frequency equation of the nanobeam with clamped–clamped and clamped–free boundary conditions is derived based on the nonlocal elasticity theory. According to the equation, it can be found that the effects of the crack parameter, crack location, and nonlocal parameter on the longitudinal frequency of the cracked nanobeam are significant. The frequency decreases with an increase of the crack parameter. However, the increasing nonlocal parameter results in a decrease of the crack effect on the frequency. In addition, when the crack location is near the support, a larger decrease in the frequency can be observed.