DSpace collection: 期刊論文

Two-dimensional displacement measurement by quasi-common-optical-path heterodyne grating interferometer

title: Two-dimensional displacement measurement by quasi-common-optical-path heterodyne grating interferometer abstract: A method based on a specific quasi-common-optical-path (QCOP) configuration for two-dimensional displacement measurement is presented. The measurement system consists of a heterodyne light source, two-dimensional holographic grating, specially designed set of half wave plates, and lock-in amplifiers. Two measurement configurations, for single and differential detection, are designed. The sensitivity, resolution and nonlinear phase error of the differential detection type are better than those of the single detection type. The experimental results demonstrate that the QCOP interferometer has the ability to measure two-dimensional displacement while maintaining high system stability. (C) 2011 Optical Society of America

Tooth contact analysis of a curvilinear gear set with modified pinion tooth geometry

title: Tooth contact analysis of a curvilinear gear set with modified pinion tooth geometry abstract: This article investigated the contact behaviours of a modified curvilinear gear set for parallel-axis transmission, which exhibits a pre-designed parabolic transmission error (TE) and localized bearing contact. The proposed gear set is composed of a modified pinion with curvilinear teeth and an involute gear with curvilinear teeth. Tooth contact analysis enabled the authors to explore the influences of assembly errors and design parameters on TEs and contact ellipses of this gear set. It is observed that TEs were continuous and the contact ellipses were localized in the middle of the tooth flanks, even under assembly errors. Finite-element contact analysis was performed to study stress distributions under different design parameters. In addition, numerical examples are presented to demonstrate the contact characteristics of the modified curvilinear gear set.

Three-dimensional response of unrelaxed tension to instability of viscoelastic jets

title: Three-dimensional response of unrelaxed tension to instability of viscoelastic jets abstract: Understanding the cause of instability of viscoelastic liquid jets is of fundamental importance to realise practical applications such as ink-jet printing, fuel injection spraying, and fibre spinning. For common viscoelastic fluids, the elastic stresses caused by the stretching of entangled polymeric chains at the nozzle can persist along the jet for a long downstream distance far away from the exit. Unrelaxed elastic tension has been regarded as a factor responsible for the delay in the breakup of viscoelastic jets. The present study performs a complete linear stability analysis to obtain deeper insights into the response of unrelaxed elastic tension to the onset of three-dimensional instability in viscoelastic jets. Results show that the elastic effect is multidimensional. In the absence of the unrelaxed tension, the elastic force, characterised by a Deborah number, has a slightly destabilising influence on both axisymmetric and non-axisymmetric disturbances. However, when the unrelaxed tension arises, the elastic force begins to suppress the instabilities driven by surface tension and the wind-induced effect to a great extent. In particular, once the tension exceeds a threshold, some novel oscillating non-axisymmetric modes emerge because of stimulation by the relaxation of the elastic energy, causing a variety of asymmetrical deformations.

The reactor design for photoelectrochemical hydrogen production

title: The reactor design for photoelectrochemical hydrogen production abstract: The heat transfer and flow characteristics of a photoelectrochemical (PEC) hydrogen generation reactor are investigated numerically. Four different reactor designs are considered in this study. The solar irradiation is separated into short and long wavelength parts depending on the energy band gap of the photoelectxode used. While short wavelength part is used to generate electron and hole pairs, the long wavelength part is used to heat the system. Because the energy required for splitting water decreases as temperature is increased, heating the reactor by using the long wave energy increases the system efficiency. Thus, how the long wavelength energy is absorbed by the reactor is very important. The results show that more long wavelength energy kept inside the reactor can increase the solar-to-hydrogen efficiency, eta(SH). For Fe(2)O(3) photoelectrode, careful reactor design can increase eta(SH) by 11.0%. For design D under 4000 W/m(2) irradiation and a quantum efficiency of 30%, eta(SH) is found to be 14.1% and the hydrogen volume production rate is 166 L/m(2) h for Fe(2)O(3). Effects of several parameters on the PEC hydrogen reactor are also discussed. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.