Typical Particle Size Distribution Research Articles

Retention efficiency of 0.2 to 6 µm particles by the appendicularians Oikopleura dioica and Fritillaria borealis

We used suspensions of 0.2, 0.5, 0.75, 1, 2, 3 and 6 µm fluorescent beads in combination with analytical flow cytometry to determine the efficiency of retention by small (165 µm trunk length), medium (347 µm) and large (689 and 734 µm) Oikopleura dioica, and by large (585 µm) Frit- illaria borealis. Large O. dioica and F. borealis were the most efficient at retaining the 2 µm beads, and small and medium O. dioica were most efficient for 1 µm beads. Large O. dioica and F. borealis showed efficiencies of ca. 15% for 0.2 µm, 33% for 0.5 µm, 58% for 0.75 µm beads, 66% for 1 µm beads and 88% for 2 µm beads. However, small O. dioica showed higher efficiencies, measuring ca. 10% for 0.2 µm, 43% for 0.5 µm, 72% for 0.75 µm beads, 87% for 1 µm beads and 93% for 2 µm beads. The combination of our measured appendicularian particle-retention efficiency spectra with typical particle size-distribution spectra in the ocean indicates that large and small appendicularians obtain 80% of their diet from particles smaller than 15 and 7 µm respectively, and that the smallest particles represent a significant part of their diet only when they strongly dominate the biomass size spectra. Comparison with data from the literature indicates that although the appendicularian:prey length ratio is extremely high, the appendicularian:prey body-carbon ratio (14 538:1) is within the reported range for mesozooplankton (1:1 to ca. 3 × 10 6 :1), and statistically undistinguishable from that of copepods (1603:1).

Controllability of particulate processes in relation to the sensor characteristics

Some considerations are given that should be regarded when selecting a sensor for the control of the particle size distribution (PSD) in particulate processes, such as crystallizers, yet-mills and granulators. As an example, the control of the crystal size distribution (CSD) dynamics in a continuous crystallization process is taken. Different methods are discussed to derive process information from a typical PSD sensor, comprising an array detector. It is shown that generally a limited number of degrees of freedom are present in the process output signals. This is due to the principle of measurement and the limited number of degrees of freedom in the process itself. Factors limiting the controllability of processes are discussed. It is shown that proper placement of the sensor in the particle size domain is important for feedback control, because the sensor characteristics will determine the location of the zeros in the process transfer function. For an industrial crystallization process, it is shown that measurement of the CSD below 30 μm limits the achievable closed-loop speed of response, due to the presence of a right halve plane zero. Effective control of the CSD is achieved, using a simple feedback controller, that measures only the fine crystals in the range of 40–200 μm. Experimental results from the UNIAK pilot crystallizer are depicted.

Particle size characteristics of suspended sediment in Southern Ontario rivers tributary to the great lakes

AbstractIn spite of the important relationship between sediment particle size and the transport/deposition of adsorbed pollutants in fluvial systems, little information regarding the size characteristics of suspended sediment transported by southern Ontario Great Lakes tributaries is currently available. This paper examines long‐term sediment and hydrometric data collected by the Water Resources Branch of Environment Canada in order to provide information on (1) typical particle size distributions of suspended sediment, (2) relationships between source material and particle size characteristics of suspended sediment, and (3) temporal variation in the particle size characteristics of suspended sediment from six southern Ontario rivers. Results illustrate the complex behaviour and variability of sediment particle size transport in these rivers and demonstrate the need for a better understanding of seasonal effects on sediment availability and conveyance processes in fluvial systems.

The dispersion model for hydration of portland cement I. General concepts

This paper introduces an analytical mathematical model for development of the hydration of Portland cement: t 0 + t 1A + t 2A 2 = t t is time, and t 0, t 1 and t 2 are time-constants depending on temperature, cement type, admixtures etc. A is the hydration ratio, i.e. the ratio of hydrated to unhydrated cement. The dispersion model has been derived on basis of the typical particle size distribution for tube-milled products. Earlier findings by us have proven the particle size distribution to be a dominant factor in the correct modelling of cement hydration. The parameterization of hydration curves, which is easily performed with this dispersion model, gives a sufficient characterization of these for purposes of practical interpretations of the effects of factors decisive for the development of hydration.