National Institute of Standards and Technology における超伝導研究及び生活

Review of discrete particle modeling of fluidized beds

Comparison of contact-force models for the simulation of collisions in DEM-based granular flow codes

A review of miniaturised humidity sensors is presented. Recent achievements in capacitive-, hygrometric-, gravimetric-, optical- and integrated sensors are discussed. Attention is paid to a general perspective of miniaturised humidity sensors, emphasising on integration issues and technological challenges. A table summarising most of the reviewed devices is included.

Recent achievements in miniaturised humidity sensors—a review of transduction techniques

Review and extension of normal force models for the Discrete Element Method

The measurement of particle rebound characteristics

An experimental study of the elastic rebound of spheres

The aim of this paper is to describe an experimental facility to measure the low velocity impact behaviour of spherical particles with high accuracy. Measurements have been made of particle rotation, normal restitution coefficient to within of glancing incidence, and tangential restitution coefficient to within of normal impact, with very low scatter. The results are accurate enough to be used for quantitative comparison to theoretical studies. Achievement of a high level of precision and reproducibility has involved detailed attention to all aspects of the experiment design, construction, control and computer-based image measurement.

https://iopscience.iop.org/article/10.1088/0957-0233/10/1/009/pdf

Accurate measurement of particle impact parameters

A novel multi-point distributed humidity-sensing system has been constructed based on the principle of using the absorption spectrum of a colorimetric reagent (cobalt chloride) immobilized on the surface of the core of a multimode optical fibre by employing a thin gelatin film. Two-wavelength detection is employed to provide intensity referencing. Light attenuation at the reference wavelength is only 0.2 dB. The basic design, construction and testing of an experimental sensor in the humidity region 20–80% RH and temperature range 25–50 °C is described. Resolution can be better than 2% RH and the time constant is about one second. Repeatability is at least as good as the resolution of measurement. A two-wavelength optical time-domain reflectometer (OTDR) has been developed and a four-sensor network has been built. The resolution of measurement on the network can be better than 4% RH, but because of noise in the OTDR the resolution value is dependent on the averaging time in the instrument.

A distributed optical-fibre sensing system for multi-point humidity measurement

The aim of this work is to provide useful quantitative support for theories of the restitution coefficient for normal impacts involving plastic deformation, especially in the region close to the threshold at which plastic deformation begins. The impacts were from spheres of 5 mm diameter of aluminium oxide (which deformed elastically), dropped on to thick plates of mild steel or aluminium alloy. Very accurate measurements of impact and rebound velocities were made for drop heights from 1.75 m down to 0.6 mm, covering a range of velocities down to the yield threshold. Most of these results are in the elastic-plastic velocity range over which the indentation pressure varies from its value at initial yield of about 1.1sigmay to the value when full plasticity is established of about 2.8sigmay. The variation in the restitution coefficient with velocity in this range closely fits the rebound model of Tabor, which allows the indentation pressure to vary through the Meyer index n. The fitted values of n take into...

Ahmad H. Kharaz

Papers

The measurement of particle rebound characteristics

An experimental study of the elastic rebound of spheres

Accurate measurement of particle impact parameters

A distributed optical-fibre sensing system for multi-point humidity measurement

A study of the restitution coefficient in elastic-plastic impact