Sieve miniature

A variation of this system is the installation of 0.5 in diameter sieves mounted on a spinning riffler to obtain small, representative powder samples, which can be sieved in situ without removing the miniature sieves from the riffler system [113]. By mounting several different aperture sieves around the riffler, a confederation of miniature sieves could replace nest sieving. 

Research projects have suggested that a multisectioned surface of a sieve can minimize the effects due to aperture distributions in the sieve. It has also been suggested that confederated miniature sieves may be able to replace nest sieving [39, 40]. 

One of the reasons that scientists have been reluctant to move from the standard 8 inch diameter sieves to use more fragile miniature sieves is that many sieving studies... 

B. H. Kaye, G. G. Clark, Confederated Miniature Sieves as an Alternative to Nest Sieving . Part. Char., 3 (1986) 145—150. 

The FPI principle can also be used to develop thin-film-coating-based chemical sensors. For example, a thin layer of zeolite film has been coated to a cleaved endface of a single-mode fiber to form a low-finesse FPI sensor for chemical detection. Zeolite presents a group of crystalline aluminosilicate materials with uniform subnanometer or nanometer scale pores. Traditionally, porous zeolite materials have been used as adsorbents, catalysts, and molecular sieves for molecular or ionic separation, electrode modification, and selectivity enhancement for chemical sensors. Recently, it has been revealed that zeolites possess a unique combination of chemical and optical properties. When properly integrated with a photonic device, these unique properties may be fully utilized to develop miniaturized optical chemical sensors with high sensitivity and potentially high selectivity for various in situ monitoring applications. 

Realisation of the first approach - trapping and offline analysis - employs a miniature gas-sampling tube packed with a mixture of Tenax (molecular sieve) and Carbopak (activated charcoal) absorbent material. Such tubes are routinely used for environmental monitoring of hazardous industrial atmospheres whereby operators during the normal course of their duties carry a small tube (about the size of a pen) clipped to their clothes. A pump may be used to draw gas through the tube at a controlled rate and, at the end of the work period, the tube is sealed and sent for analysis. Heating the sorbent tube drives off the trapped material into a gas chromatograph for separation and quantification. 

Porous membranes have been used for centuries in a number of applications and are especially important for use as filters in the size-dependent sieving of material from solution. The movement to miniaturize the pores contained within such membranes has been quite successful and has generated a number of different types of nanoporous membranes. These membranes find great diversity in application, and membranes can be prepared with a single nanopore or with a high density of nanopores. Additionally, membranes are amenable to production of pores of specific size. 

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