Slitting techniques

The two variables explained in the previous projects. Angle of Crease and Shape of Slit, create forms that arc s> nimc(rical to the axis of the gutter crease. There is also a method of achic ing asymmetric forms which will further expand your knowledge of Single Slit techniques. 

Tho prcliminarv constniction is tdcniical to ihai of ihc Single Slit version of the As> mmciric Slit technique (see page 29). Once the creases have been established, the two slits can be added. 

Almost all the Single and Double Slit techniques so far CNplained have maintained a cemml mountain crease in line with the gutter crease behind it. However, this mountain may be mo cd away from the centre to create an asymmetric eflect that is both elegant and suiprising. Follow the sccp-by-siep construction with care. 

After Sin c and Double Slit techniques, the ob ious extension is to use Multi Slits. The technique ts ideal for creating beautiful rythmic... 

This is arguably the simplest of all pop-up hearts and uses the Shape of Slit technique (see page 26). Note how by doubling over the paper at the back, the construction becomes... 

This is the most complex project in the chapter, but made easier because all the basic measurements are the same. It uses the Multi Slit technique (see page 60). To aid accuracy, it maybe advisable to fix squared paper to the back of the card, and to cut and crease on that side. Use thick paper. 

A number of techniques have been used successfully to measure temperature profiles in flames thermocouples, resistance thermometers, shadowgraphs, interferometers, pyrometers, spectrometers, pneumatic probes, and aerodynamic measurements. The most useful of these techniques have proven to be the thermocouple method and the inclined slit technique. 

The slit-shaped model has come into prominence in recent years, as electron microscopy has revealed the prevalence of solids composed of platelike particles the technique, indeed, has now developed to the point where it is possible to identify the presence of slit-shaped pores, and even to measure their width. In the ideal case where the sides of the slit are truly planar and parallel, the hysteresis takes an extreme form since the mean radius of curva-... 

The first stage in the interpretation of a physisorption isotherm is to identify the isotherm type and hence the nature of the adsorption process(es) monolayer-multilayer adsorption, capillary condensation or micropore filling. If the isotherm exhibits low-pressure hysteresis (i.e. at p/p° < 0 4, with nitrogen at 77 K) the technique should be checked to establish the degree of accuracy and reproducibility of the measurements. In certain cases it is possible to relate the hysteresis loop to the morphology of the adsorbent (e.g. a Type B loop can be associated with slit-shaped pores or platey particles). 

The film is fibrillated mechanically by mbbing or bmshing. Immiscible polymers, such as polyethylene or polystyrene (PS), may be added to polypropylene to promote fibrillation. Many common fiber-texturing techniques such as stuffer-box, false-twist, or knife-edge treatments improve the textile characteristics of slit-film fibers. 

For this technique, the upper plate has a mobile phase inlet channel on one edge and a slit at the opposite edge for directing the mobile phase toward the next plate (33). The slit (width approx. 0.1 mm) can be produced by cutting the layers with a sharp blade this enables easy passage of mobile phase and separated compounds without any mixing. The cushion of the OPLC instrument is applied to the uppermost layer only, and each plate presses on to the sorbent layer below. 

The experimental technique is simple. The cell containing the solution to be titrated is placed in the light path of a spectrophotometer, a wavelength appropriate to the particular titration is selected, and the absorption is adjusted to some convenient value by means of the sensitivity and slit-width controls. A measured volume of the titrant is added to the stirred solution, and the absorbance is read again. This is repeated at several points before the end point and several more points after the end point. The latter is found graphically. 

Fig. 1. Schematic illustration of the basic concept of the Doppler-selected TOF technique. The hatched slice on the left represents a Doppler-selection of a given vz- The strip on the Doppler slice (the middle figure) is the ID Vy-distribution measured under the -restriction of a slit in front of the TOF spectrometer. The combination of many Doppler-selected TOF measurements yields the result shown on the right. The lower figures are the corresponding actual data at each stage for the reaction of S(1D) + H2.

To sum up, the basic idea of the Doppler-selected TOF technique is to cast the differential cross-section S ajdv3 in a Cartesian coordinate, and to combine three dispersion techniques with each independently applied along one of the three Cartesian axes. As both the Doppler-shift (vz) and ion velocity (vy) measurements are essentially in the center-of-mass frame, and the (i j-componcnl, associated with the center-of-mass velocity vector can be made small and be largely compensated for by a slight shift in the location of the slit, the measured quantity in the Doppler-selected TOF approach represents directly the center-of-mass differential cross-section in terms of per velocity volume element in a Cartesian coordinate, d3a/dvxdvydvz. As such, the transformation of the raw data to the desired doubly differential cross-section becomes exceedingly simple and direct, Eq. (11). 

The Doppler-selected TOF technique is one of the laser-based techniques for measuring state-specific DCSs.30 It combines two popular methods, the optical Doppler-shift and the ion TOF, in an orthogonal manner such that in conjunction with the slit restriction to the third dimension, the desired center-of-mass three-dimensional velocity distribution of the reaction product is directly mapped out. Using a commercial pulsed dye laser, a resolution of T% has been achieved. As demonstrated in this review, such a resolution is often sufficient to reveal state-resolved DCSs. 

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