Beam Design

At temperatures above 1150°C, alloys used for the hearth or material handling systems in low and medium temperature furnaces lose strength rapidly (2) and temperatures are reached where ceramic refractories are required to support the work. This results in less use of roUer-hearth and belt-type hearths and greater use of pushers or walking-beam designs for continuous furnaces. 

Varied Beam Designs-Fobricoted to Meet Specific Job Demands. 

A large number of commercial instruments are now available and are based either on a single- or double-beam design. Important instrumental features of a modem atomic absorption instrument include the following facilities. 

Another method of flexural testing that can be used is, for example, the cantilever beam method (Fig. 2-18), which is used to relate different beam designs. It provides an exam-... 

Some spectrophotometers are single-beam instruments, and some are double-beam instruments. In a double-beam instrument the light beam emerging from the monochromator is split into two beams at some point between the monochromator and the detector. The double-beam design provides certain advantages that we will discuss shortly. 

FIGURE 8.6 An illustration (top view) of the double-beam design utilizing two cuvette holders in the sample compartment. 

FIGURE 8.7 The double-beam design in which the second beam passes directly to a detector without passing through the sample compartment. 

A basic photometer (Figure 2.17) is a single-beam instrument in which there is only one light path and the instrument is standardized using a blank solution, which is replaced with the sample to obtain a reading. The major problem with a single-beam design lies in the fact that the absorbance value recorded for the... 

No excavation is required in the roadway itself to install crash beams. All three crash beam designs possess a low crash rating relative to other types of barriers, such as wedge barriers, and thus they typically are used for lower-security applications. 

Multi-row detector systems are referred to as cone-beam systems. With a moving conveyor they become helical cone-beam systems. The cone-beam designation is in contrast to the fan-beam geometry used in Figures 3 and 4, where the source and detectors are aU in a single plane. 

Fig. 6. Critical dimensions of beam design for deflection-type torsion vacuum microbalance.

Larger ejection forces may lead to an increased wear on tooling and eject cam surface. Ejection force may also be used to evaluate the effectiveness of lubrication (of both the press and the product) and punch sticking. Sensitivity and linearity of an ejection transducer are design dependent shear force designs are always preferable over split cam or cantilevered beam designs. 

Many modem photometers and spectrophotometers are based on a double-beam design. Figure 25-20 shows two double-beam designs (b and c) compared with a... 

Double-beam instruments offer the advantage that they compensate for all but the most short-term fluctuations in the radiant output of the source. They also compensate for wide variations of source intensity with wavelength. Furthermore, the double-beam design is well suited for continuous recording of absorption spectra. 

The older IR instruments were invariably dispersive double-beam designs. These were often of the double-beam-in-time variety shown in Figure 25-20c except that the location of the cell compartment with respect to the monochromator was reversed. In most UV/visible instruments, the cell is located between the monochromator and the detector in order to avoid photodecomposition of the sample, which may occur if samples are exposed to the full power of the source. Note that photodiode array instruments avoid this problem because of the short exposure time of the sample to the beam. Infrared radiation, in contrast, is not sufficiently energetic to bring about photodecomposition. Also, most samples are good emitters of IR radiation. Because of this, the cell compartment is usually located between the source and the monochromator in an IR instrument. 

Figure 1.6 Pair of particles irradiated by two counter-propagating beams designated primary ( i, fci) and ( 2. 2) (standard optical binding) and secondary beams ( 3, 3) reflected with transverse polarization as ( 4, 4). The angle subtended by the interparticle displacement vector R on the y axis is 0, and the angle between the R projection on the zx plane and thex-axis is f.

Dispersive spectrometers. For a long time, mid-IR spectrometers were constructed on the principle of the double beam design. This fairly complex optical assembly, which remains in use for the UV/Vis, yields progressively over real time the... 

The wide-range radiolysis source shown schematically in Figure 1 consisted of three separate stainless steel compartments (A, B, C) in series, each with its own electron beam (designated hereafter as EB— e.g., EB-B means electrons beam in Compartment B). The energy and intensity of each EB emitted from a thoria-iridium filament could be varied independently by a versatile emission regulator (22) to suit the particular phase of the problem under study. The EB s were magnetically collimated to ensure localized ionization, and their intensities were usually about 10 fiA. 

Insirunicncs for atomic ahsorplioii measuremeiilc arc offered by numerous manufacturers both single- and double-beam designs are asailable. The range of sophistication and cost (upward of a few thousand dollars) is substantial. 

FIGURE 9-13 Typical flame specirophotomeiers la) single-beam design and (b) double-beam design... 

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