Frequency measurements, multiple

When oxidized NiR was put in contact with NO, the FenNO + intermediate was directly observed by FTIR spectroscopy (vnc> = 1910 cm-1) (52). This agrees with similar values of the stretching frequency measured for related ferri-hemes (24). The high values (compared to the ferro-hemes), together with the short N O distances (1.63 1.65 A) are consistent with a multiple bond, and indeed support the FeIINO + description, as generally accepted for NP and other classical nitrosyl complexes. 

The absolute frequency of the fundamental IS — 2S transition in atomic hydrogen has now been measured to 1.8 parts in 1014, an improvement by a factor of 104 in the past twelve years. This improvement was made possible by a revolutionary new approach to optical frequency metrology with the regularly spaced frequency comb of a mode locked femto-second multiple pulsed laser broadened in a non-linear optical fiber. Optical frequency measurement and coherent mixing experiments have now superseded microwave determination of the 2S Lamb shift and have led to improved values of the fundamental constants, tests of the time variation of the fine structure constant, tests of cosmological variability of the electron-to-proton mass ratio and tests of QED by measurement of g — 2 for the electron and muon. 

FFT techniques can measure multiple-frequency AC impedance at the same time as a stimulus waveform containing multiple frequencies. FFT performs very fast AC impedance measurements and can function as a complement to the single sine wave technique. The stimulus waveform, which is constructed by multiple sine waves, should also have as low an amplitude as possible to avoid or decrease the harmonic distortion effects at the non-linear regime. However, if the amplitude of the stimulus wave is too low, each single sine wave will be much lower and may be distorted by noises. Fortunately, some commercially available analyzers have the option of selecting the frequencies for AC impedance measurements. Usually, stimulus frequencies are selected in such a way that each is not coincident with the main harmonics of the lower frequencies. As a result, the main components of the harmonic distortion from each frequency in the stimulus waveform do not interfere with the other stimulus frequencies. 

The M-S measurement is performed at several different frequencies to verify that the slope and x-intercept do not change. If they do change and/or the M-S plot is not linear, as is the case in Fig. 6.6, then a more detailed analysis using frequencies over multiple decades (e.g. 1 x 10 -1 x 10 Hz) should be used in conjunction with a more sophisticated equivalent circuit model [14, 23]. 

The use of FFT (fast Fourier transform) spectral analysis can be the perfect complement to the single sine analysis technique. The FFT can perform very fast measurements since it is not necessary to sweep the stimulus frequency in order to measure multiple frequencies. With the introduction of DSP technology, very fast... 

EXTAR 6000 Dynamic Mechanical Spectrometer This instrument applies various deformations, such as bending, tension, compression, and shear, to a solid sample and operates in the oscillatory mode as well as the static mode for stress relaxation and creep. For dynamic measurements, a new synthetic oscillation mode has been added to the existing high-precision sine wave oscillation mode. The synthetic oscillation mode can measure multiple frequencies at an extremely fast rate, which allows the instrument to measure samples with extremely rapid elastic modulus transformations. Measurements from -150 °C are fully automatic using the automatic gas cooling unit. 

Several PSFs may have a decisive contribution to the failure mode of a downstream PSF, in such a way that their omission could automatically cancel this failure mode. This situation is tackled by introducing another type of node to the network, namely the situational (S) node , whose frequency is the product of the multiplication of the frequencies of the converging nodes and importance is defined according to frequency measure. A case of a situational node in a network is presented schematically in Figure 5. 

Phase Doppler anemometry or phase Doppler analysis was proposed two decades ago, based on the then well-established flow measurement technology-laser Doppler velocimetry [110]. PDA is widely used in sizing spherical and homogeneous particles, such as liquid sprays, aerosols, air bubbles in liquid, or other spherical particles. When single particles move through the intersection of at least two focused laser beams, they scatter light from each beam with different individual Doppler frequency shifts. Multiple detectors are placed at... 

Figure Al.6,8 shows the experimental results of Scherer et al of excitation of I2 using pairs of phase locked pulses. By the use of heterodyne detection, those authors were able to measure just the mterference contribution to the total excited-state fluorescence (i.e. the difference in excited-state population from the two units of population which would be prepared if there were no interference). The basic qualitative dependence on time delay and phase is the same as that predicted by the hannonic model significant interference is observed only at multiples of the excited-state vibrational frequency, and the relative phase of the two pulses detennines whether that interference is constructive or destructive.

The sound absorption of materials is frequency dependent most materials absorb more or less sound at some frequencies than at others. Sound absorption is usually measured in laboratories in 18 one-third octave frequency bands with center frequencies ranging from 100 to 5000 H2, but it is common practice to pubflsh only the data for the six octave band center frequencies from 125 to 4000 H2. SuppHers of acoustical products frequently report the noise reduction coefficient (NRC) for their materials. The NRC is the arithmetic mean of the absorption coefficients in the 250, 500, 1000, and 2000 H2 bands, rounded to the nearest multiple of 0.05. 

Frequency-Modulation Spectroscopy. Frequency-modulation spectroscopy (tins) is a high sensitivity null-background infrared technique for measuring absorbances down to 10 with fast acquisition speeds. Fms involves frequency-modulating a laser source at COq to produce a carrier frequency having sidebands at cJq where is an integral multiple of the modulation frequency. Dye lasers and many other single-line sources can... 

A measure of risk to a group of people. It is most often expressed in terms of the frequency distribution of multiple casualty events... 

---