Chord length measurement

Chord length measurement is not ideal for these sort of branched crystal growth... 

Chord length measure- ment Apparent volume >1 xm Moderate to high Any High Untested technique... 

S.4 Chord Length Measurement Using Laser and Rotating Mirror. 

Several diameter definitions are used in particle image measurements (Fig. 7). Martin diameter, the chord length which divides the projected particle into two equal areas with respect to a fixed dkection (29) Feret diameter, the projected length with respect to a reference dkection (30) and the diameter of equivalent surface area, the diameter of a ckcle the area of which is equivalent to the projected area of the particle in question (3). 

CSM has coupled the FBRM with a second probe, the particle video microscope, PVM (Lasentec/Mettler Toledo), which consists of six illuminating near-infrared lasers (850 nm) that are transmitted into the sample. While the FBRM provides precise quantitative tracking of the chord lengths, the PVM probe provides qualitative images of the hydrate particle size and degree of agglomeration. The size range scale of hydrate particles that can be measured with the PVM probe is 10-300 i,m. 

The local gas holdup and bubble behavior were measured by a reflective optic fiber probe developed by Wang and co-workers [21,22]. It can be known whether the probe is im-merging in the gas. The rate of the time that probe immerg-ing in the gas and the total sample time is gas holdup. Gas velocity can be got by the time difference that one bubble touch two probes and the distance between two probes. Chord length can be obtained from one bubble velocity and the time that the probe stays in the bubble. Bubble size distribution is got from the probability density of the chord length based on some numerical method. The local liquid velocity in the riser was measured by a backward scattering LDA system (system 9100-8, model TSI). Details have been given by Lin et al. [23]. 

The interpretation of local gas holdup, bubble chord length, and bubble velocity from the probe response has been discussed previously (13). As indicated earlier, the measured bubble length is not equal to the bubble diameter but rather is associated with the probability of a single bubble striking the probe over the projected area of the bubble and with the shape of the bubble. The relationship between measured chord length and bubble size has been discussed previously (1A, 15). The... 

The NA measurement yields a mean chord length of the pores 7=10.8 nm, via Eqs. (2). By use of this value, it follows a normalized Porod plot, defined by... 

Boeckeler manufacture simple systems which require more operator input but are less expensive than more automated systems. The VlA-20 Video Image Marker ean be used to mark details on a video image the VIA-50 includes a more varied array of positionable markers with an option for multiple overlay storage the VIA-100 can perform horizontal, vertical and point-to-point measurements, and the VIA-150 combines the capabilities of the VIA-50 and VIA-100. The VIA-160A1 video area measurement system can be combined with a video microscopy system to give cell areas, chord lengths and number counts. 

Lasentec s Focussed Beam Reflectance Measurement Model (FBRM M400L) operates at a wavelength of 791 nm and the beam rotates 75 s at a peripheral speed of 1.9 ms .to describe a circle of diameter 8 mm. It has been used with a 3D-model of chord length distribution for particles of a general shape as well as particles with the same shape but different sizes [124]. The focal point can be changed in the axial position but it is... 

The latest on-line version covers the size range 0.8 to 1000 m in 38 channels. In an investigation of this instrument it was found that the measured chord lengths data were sensitive to the location and orientation of the probe. Normalizes chord length data were in good agreement with predictions from the measured size distributions [129]. 

Focused beam reflectance measurement (FBRM) particle size (chord length) distribution... 

For the output variables, as shown in Figs. 9-15 and 9-16, the filtration time data correlated well with mean particle size (chord length) and the level of fines by Lasentec FBRM measurement and optical micrographs. This correlation enabled direct feedback of process performance (cake filtration resistance) based upon FBRM measurement. 

The terms dispersion characteristic and respective or constituent amount need further explanation. The dispersion characteristic, also called particle size, grain size, fineness index, or dispersion parameter, is a physical property which can be measured and defines, in a suitable way, the dispersity or, in a narrower sense, the dimensions of the particles. In the case of spheres, diameter would be the most descriptive dispersion characteristic. If the particles are irregularly shaped, other linear dimensions must be chosen, e.g. the statistical chord lengths according to Martin or Feret (Figure 21), the mesh size of a screen through which the particle just passes, or so-called equivalent diameters. Equivalent diameters are calculated from other dispersion characteristics, which must not necessarily be linear dimensions, using mathematical relationships and/or physical laws. 

More recently, there have been in-process techniques developed. Focused Beam Reflectance Measurement (FBRN ) uses an immersion probe and is capable of in situ measurement of particle chord length. Obscuration measurement can also be used as an in line size measurement. Acoustic size measurement is also emerging as in-process technique that permits use in heavy slurries that are difficult to measure using optical techniques. 

Further information from x-ray scattering can be extracted if a two-phase media model is applied. In this model, the porous body is assumed to consist of two phases with constant mass (or electron) density. The solid phase has a mass density that occupies a volume fraction 0s, and the voids with Pp = 0 occupy a volume fraction 0p = 1 - 0s. By the application of this model, the specific surface area and the mean chord length of each phase can be derived, provided an absolute intensity measurement is made [38]. 

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