Scanning Measurement

Most paper quality measurements in the paper machine are scanning measurements. In various locations so called scanners with usually one upper and one lower measurement head are found (Fig. 9.2). Both measurement heads move synchronously across the paper width. One scan takes about 20 to 30 s. The paper moves much faster than the scanning measurement While the paper is moving e.g. 500 m the scanner moves across the web only 7 to 10 m. Thus, the scanning sensors can be seen as a system which measures paper quahty in MD and which is moved slowly across the web. 

During each scan hundreds of measurement values are collected. The resolution in CD is typically 10 mm. Each scan contains information of MD and CD variation of the measured paper quahty. MD and CD informahon are used for different purposes and have to be separated from each other. 

Upper and lower measurement head with multiple sensors 

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V/Q scan and CT scans are the most commonly used tests to diagnose PE. A V/Q scan measures the distribution of blood and air flow in the lungs. When there is a large mismatch between blood and air flow in one area of the lung, there is a high probability that the patient has a PE. Spiral CT scans can detect emboli in the pulmonary arteries. 

For 2PA or ESA spectral measurements, it is necessary to use tunable laser sources where optical parametric oscillators/amplifiers (OPOs/OPAs) are extensively used for nonlinear optical measurements. An alternative approach, which overcomes the need of expensive and misalignment prone OPO/OPA sources, is the use of an intense femtosecond white-light continuum (WLC) for Z-scan measurements [71,72]. Balu et al. have developed the WLC Z-scan technique by generating a strong WLC in krypton gas, allowing for a rapid characterization of the nonlinear absorption and refraction spectra in the range of 400-800 nm [72]. 

Firester AH, Heller ME, Sheng P (1977) Knife-edge scanning measurements of subwavelength focused light beams. Appl Opt 16 1971-1974... 

Two redox states of one complex, (168) and (169), exhibit very similar respective values of ca. 0.6 J cm-2 and 0.7 J cm-2 with 32 ps pulses at 532 nm (in benzene).452 A 532 nm OL study of the two neutral complexes (170) and (171) using ns and ps pulses has also been reported.453-455 Low values of ca. 0.3 Jem-2 are observed with ps pulses in benzene, and both ps time-resolved pump-probe and Z-scan measurements reveal that RSA and nonlinear refraction are responsible for the OL behavior.453-455 Because (170) and (171) are transparent in the region 400-900 nm, their OL responses should cover a wider range than those of fullerenes and MPcs.453-455 Dai et al. have applied ps 532 nm DFWM to the tetrahedral Zn11 or Cd11 complexes (172) and (173), the modest 7 responses of which are resonance enhanced by the n- 7r transition at 512nm.456 The dimeric square pyramidal Zn11 complex (174) exhibits a broad n —> tt absorption with Amax = 497 nm in DMF and is shown by 532 nm Z-scan to exhibit SF behavior.457... 

R. DeSalvo, M. Sheik-Bahae, A.A. Said, D.J. Hagan, and E.W. Van Stryland, Z-scan measurements of the anisotropy of nonlinear refiaction and absorption in crystals. Optics Letters 18(3), 194 (1993). 

As described in the previous section, the femtosecond fluorescence up-conversion microscope enabled us to visualize microscopic samples based on position-depen-dent ultrafast fluorescence dynamics. However, in the imaging measurements using the fluorescence up-conversion microscope, XY scanning was necessary as when using FLIM systems. To achieve non-scanning measurements of time-resolved fluorescence images, we developed another time-resolved fluorescence microscope. 

The use of a line scan facility on an imaging microscope enables the applicability of the two-dimensional theory to be tested directly. In Fig. 12.5, images of glass at three different values of defocus are presented. Superimposed on each picture are line scans measured along the line indicated in the middle. 

MONTE CARLO SIMULATIONS OF RADIATIVE TRANSFER FOR LIMB SCAN MEASUREMENTS... 

The Siro model is a good tool in the development of constituent retrieval algorithms for limb scan measurements. However, the Monte Carlo technique requires a lot of computer time. Faster models need to be developed for near-real time processing of limb spectra to constituent profiles. Siro serves as a reference against which faster but more approximate methods can be validated. 

Measurements of structural abnormalities using CT or MRI brain scans Measurements of functional or physiological abnormalities using PET, EEG, evoked potentials, or magnetoencephalography... 

Figure 1.59 Scheme of a stopped-flow rapid scan measurement sequence [110] (by courtesy of RSQ. 

Figure 6.10 Conventional 29 — 9 scans measured for (a) a SBTN and (b) a fluorite-SBTN thin film and (c) sbt powder.

The Z-scan theory has been described by different authors. In the thin sample limit the Z-scan measurement is described either through Fresnel integration or through a Gaussian decomposition procedure [3,6]. 

The analysis of Z-scans relies on Gaussian spatial beam profiles. For short laser pulses the beam profile is frequently not completely Gaussian and the unbiased use of the standard anlaysis of Z-scan can lead to large experimental errors. For reliable Z-scan measurements the spatial beam profile has to be well... 

Chappie et al thourougly discussed the critical parameter of Z-scan and Mian et al. [35] showed the influence of beam ellipticity on the Z-scan measurements. A solution to overcome the troubles with non-Gaussian beams is the employment of top-hat beams [36,37]. An aperture is placed in the expanded beam in front of the focusing lens, so that the beam profile is uniform in the aperture. The analysis follows an analogous approach as for Gaussian beams and results in similar curves but with a magnitude that is about 2.5 times larger. 

Although Z-scan is a very simple experiment at first view, caution has to be taken in the interpretation of the measurement curves. By far the most common source of errors in the interpretation of Z-scan measurements is the presence of slow components in the complex susceptibility changes, especially the thermal nonlinearity. 

In addition to the effect of the amount of fiber content also a dependence on the type of the used fiber can be observed in a different example (Fig. 8, [26]). In this investigation it was possible to carry out the wave-scan measurements directly on the unpainted surfaces. 

Of 24 solvent abusers (mean age 23 years), who had used substances containing a mean of 425 mg of toluene per day for an average of 6.3 years, 16 had marked impairment in neurological and neuropsychological tests cerebellar symptoms were particularly prominent (21). The impairment correlated significantly with CT scan measurements of the cerebellum, ventricles, and cortical sulci, all of which were abnormal compared with age-matched controls. 

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