Circular sample

The solution of this problem was to design a device with circular sample transfer. Irradiation and chemiluminescence measurement are spatially separated ... 

Figure 1. Estimation scheme for sulfur emission from an average Stryphnodendron tree where emissions from roots, leaf litter, and soil were sampled at 4 m intervals on transects radiating out from trunk. Emissions at each distance (Table I) were multiplied by the area of circular sampling band between that distance and the previous distance, and the emissions summed through the circular bands for the whole tree.

Figure 5.14. Schematic of the four-electrode glass cell used for conductivity measurements on a circular sample of the membrane, using a steady-state linear sweep galvanodynamic technique [10], (Reproduced by permission of ECS—The Electrochemical Society, from Slade S, Campbell SA, Ralph TR, Walsh FC. Ionic conductivity of an extruded Nafion 1100 EW series of membranes.)...

Chemiluminescence at ambient temperature in this study was obtained from circular samples 1.0" in diameter (average wt. 0.5g), irradiated to 5MR only, which were placed in the sample well of an apparatus with automated counting function (Turner Designs, Inc. Model 20 Luminometer). The light emission was measured for several time periods of 120 seconds each. Average values and standard deviations were then obtained with pocket calculators. 

The powdered samples are contained in glass capillary tubes, D, of 1.6-1.8-mm id, which are placed in the circular sample holder plate, A. 

Sample sheets of 100 x 50 x 4 millimeter were prepared with the wet deposition technique. Two rectangular TMA samples and one circular TMA sample were machined from these sheets. The rectangular samples, 10 x 7 x 4 mm, were taken in the length (X) direction and in the width (Y) direction of the sample sheet. The circular sample, diameter 5 mm, was used to measure the l.e.c. in the Z direction. The samples, placed in a TMA 7, were measured from -20°C to 120°C with a heating rate of 2°C/minute. Subsequently, the sample was cooled with the same rate and heated again for the real measuring scan. The first heating scan was ment to remove the frozen-in stresses which influence the thermal expansion behaviour (see 3.1.2). 

The rotary abradcr applies two abrasive wheels under controlled pressure to a circular sample mounted on a rotating table or platform. The wheels arc free to rotate under the friction exerted by the moving specimen, and being mounted at an acute angle they induce wear. The weight loss of the coating can be determined after a fixed number of cycles... 

In the falling-dart test a circular sample of polymer is supported horizontally and a pointed steel dart is allowed to fall so that it strikes the centre of the disc. The standard dimensions for this test are radius of test disc 6 cm, thickness of disc 2 mm and radius of dart tip 1 mm. The disc is supported horizontally by an annulus of 4 cm aperture to which it is clamped by a second annulus. The behaviour of the sample can be studied under a variety of dilferent degrees of severity of impact simply by varying the height from which the dart is allowed to fall. 

A circular sample of 74 mm in diameter is sealed over the open mouth of a cup containing water and placed in standard atmospheric conditions. The evaporation of water through the fabric specimen is observed by successive weighing of the cup after the specimen has reached equilibrium. The cup is filled with 100 ml distilled water and an air gap of 19mm is left between the water surface and the fabric. The air velocity over the specimen is maintained at 2.8 m/s, as shown in Fig. 2.14. After a suitable time, for example overnight, the dishes are reweighed and the time noted. The water vapour transmission is given by ... 

Secondly, the mixture produced is thermoformed in a hot-plates press at 80 °C for 5 min using a pressure of 1 ton with the aim of obtaining circular samples. The thermoformed sample of activated NR was then introduced into a circular mould. The mould was also placed in the hot-plates press where the vulcanization and foaming process were performed simultaneously. The reason for choosing a hot-plates press instead of a conventional oven was that the heat transfer is faster in a press than in an oven, which consequently allows a reduction in the production time. Nevertheless, no pressure was applied to the material. The plates of the press were only in contact with the upper and lower surfaces of the mould. Temperature and time were set up respectively to 160 °C and 30 min. During this time, NR was crossUnked and expanded due to the decomposition of azodicarbonamide in gases, mainly N2 and CO, allowing NR to fill the mould completely. Finally, the mould was water cooled and the foam was removed from it. 

Tensile tests on tubular samples (a) frame for holding sample, (b) circular sample at start of test, (c) sample after or during test. 

Rheological experiments were performed with a Rheometrics RDS-II and a Philips selfmade dynamic spectrometer. Circular samples for this measurement were cut from the compression moulded sheets. 

The size and shape of samples should be as follows powder or granular form below 60 mesh for thinner films, cut the disks to fit in the circular sample vessels for molded or pelleted samples, cut the samples to fit the containers. 

The stress-stram curves for PTL materials over a wide range of compressive loads (0-5 MPa) have been measured (Escribano et al., 2006 Nitta et al., 2008). Nitta et al. attributed the variations at small loads (<0.2 MPa) to small differences in surface roughness across the samples. They also discussed two hnear regions on the curves that were attributed to the sequential deformation due to the collapse of hydrophihc and hydrophobic pores. More recently, Sadeghi et al. (2008,2010a,b) reported measurements on circular samples of 78% porous Toray carbon papers under static and cyclic loads of up to 1.5 MPa. These measurements revealed significant hysteresis in the measured parameters (porosity, thickness, etc.) with subsequent stabilization within a few cycles. A summary of representative data sets is plotted in... 

Through experiments, the following relationship to quantify screen compliance for circular samples of fine mesh LAD screens has been established by Paynter (1973a) ... 

The second correction factor F2, that accounts for the limited lateral dimensions of the sample, is of a more complex nature and will not be discussed here in detail (cf. Schroeder, 1998 UhUr, 1955). For circular samples, however, it can be shown that the diameter D has to be larger than 40 times the probe spacing (D> 40r), with the probes centered in the middle of the sample to keep the error <1%, but for samples with a diameter of 125 the error is still lower than 5%. A similar dependence is foimd for rectangular or square shaped samples, where the width of the sample should exceed 405 to obtain an error <1% (125 for <5%) (Smits, 1958). As the error increases drastically with decreasing sample size, it is inevitable for smaller samples to use correction factors, which are tabulated or can be calculated from literature. The minimum sample size for accurate measurements consequently depends on the used probe spacing and implies a width of at least 20 mm, for 5 = 0.5 mm, but almost 64 mm, for 5 = 1.59 mm (62.5 mils). 

The I -V were derived for small applied voltages by Riess and Tarmhauser for an arbitrary ratio of the electron and ion concentrations. The limitation of small applied voltages was then removed in analyzing a MIEC for which the model "n p N (or > w N ) holds (together with Equation (7.16)). All - /, i,j = 1,...4 relations have been evaluated in the steady state for the circular sample of Figure 7.3. We quote here the F32 - /relation first that of interest when the electrode 1 is the reversible one. 

The 1-V relations for the Van der Pauw configuration with three reversible electrodes (numbers 1, 2, and 3, respectively) and one ion-blocking electrode (number 4) for circular samples as shown in Figure 7.3 have been evaluated for the same model p n V (and p V ) and Oj ... 

Instead of a linear configuration one can also use a Van der Pauw configuration with planar samples. It is most convenient to use circular samples with four equally spaced electrodes applied near the edge. ... 

A Philips type PU 9800 FTIR spectrophotometer was used. The food simulants were placed between two KBr pellets and analysed directly. On the other hand, the PVC circular samples were dissolved in tetrahydrofuran. After evaporation of the solvent, a polymeric film was recovered and analysed. 

Another stretching flow that has been used to characterize the nonlinear behavior of melts is equibiaxial extension, usually called simply biaxial extension. This flow can be generated by clamping a circular sample around its rim and stretching it radially, as demonstrated by Hachmann and Meissner [160]. The biaxial strain gg is given by ... 

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