Apparatus measurement

Figure Bl.20.1. Direct force measurement via deflection of an elastic spring—essential design features of a direct force measurement apparatus.

According to an elegant remark by Davies [5], "Modem scientific data handling is multitechnique, multisystem, and manufacturer-independent, with results being processed remotely from the measuring apparatus. Indeed, data exchange and storage are steps of the utmost importance in the data acquisition pathway. The simplest way to store data is to define some special format (i.e., collection of rules) of a flat file. Naturally, one cannot overestimate the importance of databases, which are the subject of Chapter 5 in this book. Below we discuss three simple, yet efficient, data formats. 

On-Hne Procedures The growing trend toward automation in industry has resiilted in many studies of rapid procedures for generating size information so that feedback loops can be instituted as an integral part of a process. Many of these techniques are modifications of more traditional methods. The problems associated with on-line methods include allocation and preparation of a representative sample analysis of the sample evaluation of the results. The interface between the measuring apparatus and the process has the potential of high complexity, and consequently, high costs [Leschonsld, Paiticle Cha racterization, 1, 1 (July 1984)]. 

As is true for macroscopic adhesion and mechanical testing experiments, nanoscale measurements do not a priori sense the intrinsic properties of surfaces or adhesive junctions. Instead, the measurements reflect a combination of interfacial chemistry (surface energy, covalent bonding), mechanics (elastic modulus, Poisson s ratio), and contact geometry (probe shape, radius). Furthermore, the probe/sample interaction may not only consist of elastic deformations, but may also include energy dissipation at the surface and/or in the bulk of the sample (or even within the measurement apparatus). Study of rate-dependent adhesion and mechanical properties is possible with both nanoindentation and... 

Mess-, measuring, -analyse,/, volumetric anal-3. sis. -apparat, m. measuring apparatus, -apparatdl, n. (Petroleum) meter oil. -band, fi. tape measure. 

NOx measurement is much more difficult than that of SO2 and levels seem to vary considerably, depending on the position of the measuring apparatus. SO2 measurements are much more consistent. 

Figure 54.5 Common right triangle and simplified alignment-measuring apparatus...

Strictly speaking the description of such local measurements can be carried out only within the framework of quantum electrodynamics, i.e, in a theory wherein photons can be exchanged between the measuring apparatus and the current distribution being measured. 

The statics and dynamics of microstructures are governed by the forces that create or maintain them. Rarely can the forces be measured directly. But forces between special surfaces immersed in fluid can now be accurately gauged at separations down to 0.1 nm with the direct force measurement apparatus, an ingenious combination of a differential spring, a piezoelectric crystal, an interferometer, and crossed cyhndrical surfaces covered by atomically smooth layers of cleaved mica (Figure 9.4). This recent development is finding more and more applications in research on liquid and semiliquid microstructures, thin films, and adsorbed layers. 

FIGURE 9.4 The direct force measurement apparatus shown here ean measure the forees between two eurved molecularly smooth surfaces in liquids. Mica surfaces, either raw or eoated, are the primary surfaees used in this apparatus. The separation between the surfaces is measured by optieal teehniques to better than 10 nm. The distance between the two surfaces is controlled by a three-stage meehanism that ineludes a voltage-driven piezoelectric crystal tube supporting the upper mica surface this crystal tube can be displaced less than 10 nm in a controlled fashion. A force-measuring spring is attached to the lower mica surface and its stiffness can be varied by a factor of 1,000 by shifting the position of a movable clamp. Reprinted with permission from Proc. Natl. Acad Sci. USA, 84, July 1987, 4722. 

If we suppose that these Rydberg states have non-negligible lifetimes against autoionization, as could occur via dispersion of the potential energy of the molecule into various vibrational modes, then these states would be very sensitive to electric fields in the measuring apparatus. It is suggested here that this is the reason for the large discrepancies between cross sections measured in the various beam experiments. 

Shimo, M., A Continuous Measuring Apparatus using Filter-Sampling Technique for Environmental Radon Daughters, Research Letters on Atmospheric Electricity, 4 63-70 (9184). 

This is our starting point and the infinite dilution case was analysed by Einstein in the early years of this century.12 This analysis was based on the dilation of the flow field because the liquid has to move around the flowing particle. The particles were assumed to be hard spheres so that they were rigid, uncharged and without attractive forces small compared to any measuring apparatus so that the dilatational perturbation of the flow would be unbounded and would be able to decay to zero (the hydrodynamic disturbances decay slowly with distance, i.e. r 1) and at such dilution that the disturbance around one particle would not interact with the disturbance around another. The flow field is sketched in Figure 3.10. The coordinates are centred on the particle so that the symmetry is clear. The result of the analysis for slow flows (i.e. at low Reynolds number) was ... 

Fig. 5.10 Computer-assisted extraction kinetics-measuring apparatus for highly stirred phases (A) high-speed stirrer (B) stirrer shaft (C) sample inlet (D) Teflon stirring har (E) Teflon phase separator (F) water hath (G) flow-cell (H) spectrophotometer (I) peristaltic pump (J) chart recorder (K) A/D converter (L) clock (M) minicomputer (N) dual-floppy disk drive (O) printer, (P) plotter. (From Ref. 16.)...

FIGURE 11.48 Schematic diagram of radiochemical OH measurement apparatus (adapted from Felton et al. 1990). 

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