Frequency measurements

The last part, following the method to analyse radioscopy and acoustic emission values, will be to correlate the characteristic values of the radioscopic detection of casting defects with extracted characteristic values of the acoustic emission analysis. The correlation between the time based characteristic values of acoustic emission analysis and the defect characterizing radioscopy values did not come to very satisfactory results referring the low frequency measurements. The reason can be found in the... 

The symbol t can be thought of as a mnemonic for time, while v/N is like the frequency measured in cycles per unit of time. 

At CSM Materialteknik AB the question has been raised whether the porosity estimation can be simplified further by utilizing attenuation measurements at a single frequency only. Empirical work show that for a given frequency, which is selcted based on the thickness of the inspected object, there is a correlation between the attenuation and the porosity contents. However, there has still not been any documented results proving that single frequency measurements are sufficient for porosity estimation. 

Effect of Vibration. Tfll objects have a natural frequency of vibration when stmck sharply and fan rings, blades, stmcture, etc are no exception. Vibration is usually siausoidal and its frequency measured ia Hertz. The travel or displacemeat of the vibratioa is measured ia mils (1 /1000 of an iach) ia the United States but ia micrometers elsewhere. Another measuremeat is velocity (mm/ s) of movement. 

An alternative method of studying the molecular motions of a polymeric chain is to measure the complex permitivity of the sample, mounted as dielectric of a capacitor and subjected to a sinusoidal voltage, which produces polarization of the sample macromolecules. The storage and loss factor of the complex permitivity are related to the dipolar orientations and the corresponding motional processes. The application of the dielectric thermal analysis (DETA) is obviously limited to macromolecules possessing heteroatomic dipoles but, on the other hand, it allows a range of frequency measurement much wider than DMTA and its theoretical foundations are better established. 

Another measure of frequency measured in radians (ft) = 2jif). 

Impedance Some of the errors arising from the use of linear polarisation resistance led to interest and development in a.c. systems.An early development used a fixed a.c. frequency and a commercial instrument was produced in the UK. Inaccuracies still occurred, however, and were due to the electrode impedance which is fequency dependent. Electrode reactions have a capacitance component, in addition to resistance, resulting in a requirement to measure the impedance. However, the total impedance comprises values for the reaction, solution, diffusion and capacitance. Measurements at different frequency are more reliable, particularly where high solution resistances occur. Simplifications for industrial monitoring have been developed consisting of two measurements, i.e. at a high (10 kHz) and low frequency (0-1 Hz). The high-frequency measurement can identify the... 

Another and more accurate microwave method makes use of frequency measurements.1 11 16 28 31 Acetaldehyde is an example of the class of molecules to which this method has been applied. Here there are three equivalent potential minima because of the... 

As long as the collisional frequency measured by 1/tj is less than this value, i.e. 

The spatial frequency measured by the interferometer is a two-dimensional quantity. It depends on the three-dimensional baseline B between telescopes... 

Application of small metal particles has attracted the attention of the scientists for a long time. As early as in the seventies Turkevich already prepared mono-dispersed gold particles [19], and later, using molecular transition metal carbonyl clusters [20], the importance of small nanoparticles increased considerably. One of the crucial points is whether turnover frequency measured for a given catalytic reaction increases or decreases as the particle size is diminished. 

In spectral identification, the first step is a comparison of the observed losses with vibrational frequencies measured by IRS in the gas phase, to see if any correlations exist. When a molecule is attached to a surface it is fettered by forces due to the chemical bonds to the surface, and there will be stretching modes of vibration... 

The axial profiles of the characteristic major frequencies measured along the bed height with the 25.4-cm and the 40.6-cmjet nozzle assemblies under different jet flow rates are shown in Figs. 22 and 23. The frequency profiles reveal that increasing the jet flow rates results in an increase in the... 

Figure 22. Profiles of the characteristic major frequencies measured along the bed height with the 25.4-cm jet assembly.

The bubbling frequencies measured in this study are much smaller than the 5- 8 Hz measured by Rowe et al. (1979) and the 20 Hz measured by Hsiung and Grace (1978). The difference may be due to the dominant effect of the much larger initial bed heights and jet nozzle sizes in this study. 

A mixture of noninteracting fluorophores might be observed by spatially variant FRET in a specimen, which is blurred because of optical resolution issues, will result in different lifetimes being measured for zm and zy- and zm > %f. In many instances, a single frequency measurement will be insufficient to determine the number of fluorophores or the number of fluorophore environments in a sample. 

Differently, and in agreement with previous findings (De Marco et al. 1995, 1999), both MN and AAT were observed in all treatments with MH (Fig. 1), including the positive control (H20 treatment). However, with respect to the positive control, the treatment with MH alone at different concentrations produced a significant increase of the clastogenic effect in V. faba, A. cepa and P. sativum (Ferrara et al. 2004) (Fig. 4). The MN and AAT frequencies increased as a function of MH concentration, but the differences were significant at the Duncan s test at P<0.05 only for AAT (Fig. 4). With respect to the positive control, the increases of frequencies measured for V. faba, A. cepa and P. sativum were for MN, respectively up to 9.8, 10 and 14 times, and for AAT, respectively up to 7.6, 2.8 and 1.8 times. 

Fig. 4. Relative frequency of MN and AAT in 30,000 root-tip cells of V. faba treated with MH at different concentrations, with respect to the frequency measured for the treatment with 10 mg L-1 of MH.

The recurrent nature of panic attacks can be viewed as an exclusion criterion, but it can as easily be considered an integral part of the syndrome, especially if one adopts a position that a person who had one panic attack but is severely impaired and a person who is mildly impaired but has frequent panic attacks should both qualify for the diagnosis. Since the DSM requirement of at least two unexpected panic attacks seems arbitrary, we would analyze recurrence as one of the criteria. Specifically, we propose to operationalize recurrence as a simple frequency measure, the history of unexpected panic attacks (i.e., 1, 2, 3). 

Figure 7 Apparatuses for frequency measurements of the LB film-deposited QCM in water and structures of lipid molecules...

From the frequency measurements of the LB-film-deposited QCM plate in water, the behavior of phospholipid LB films can be classified into three types (i) phospholipids having relatively hydrophilic head groups such as DPPC and DPPG are hydrated and then easily flaked from the substrate in the fluid liquid crystalline state above Tc (ii) DPPE and DPPS having the less hydrophilic head groups are hydrated only near their Tc (iii) cholesterol LB films show relatively large hydration behavior even at low temperatures due to the water penetration into the structure defects in the membrane. 

CIR-FTIR spectroscopy provides a direct technique for studying in situ hydrous metal oxide surfaces and molecules adsorbed on these surfaces (37). By itself, FTIR spectrometry is a well established technique which offers numerous advantages over dispersive (grating) IR spectrometry (1) improved accuracy in frequency measurements through the use of a HeNe laser (2) simultaneous frequency viewing (3) rapid, repetitive scanning which allows many spectra to be collected in a small time interval (4) miriimal thermal effects from IR beam and (5) no detection of sample IR emissions (38). 

For high-frequency measurements, normal photomultipliers are too slow, and microchannel plate photomultipliers are required. However, internal crosscorrelation is not possible with the latter and an external mixing circuit must be used. 

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