Subject resonance frequency

Besides the inherent lateral natural frequency characteristic, compressors are also influenced by torsional natural frequencies. All torsionally flexible drive trains are subject to non-steady or oscillatory excitation torques during normal operation of the system. These excitation torques can be an inherent function of either the driver or the driven equipment and, when superimposed on the normal operating torque, may appear to be of negligible concern. However, when combined with the high inertia loads of many turbomachinery trains and a torsional resonant frequency of the system, these diminutive ripples can result in a tidal wave of problems. 

Curve of the frequency dependence of the amplitude of the displacement of a material specimen subject to forced oscillatiom in the region of a resonance frequency. 

Note 1 Material specimens subject to a forced oscillation in general have a spectrum of resonance frequencies. 

Because of its piezoelectric properties, synthetic CC-quartz is used for frequency control in electrical oscillators and filters and in electromechanical transducers. When mechanically stressed in the correct direction, CC-quartz develops an electric polarization. The opposite is also tme an applied electric field gives rise to a mechanical distortion in the crystal. Thin sections of quartz are cut to dimensions that produce the desired resonance frequency when subjected to an alternating electric field the vibrating crystal then reacts with the driving circuit to produce an oscillation that can be narrowly controlled. Quartz is ideal for this application because it is hard, durable, readily synthesized, and can be tuned to high accuracy, for example, quartz crystal clocks can be made that are stable to one part in 109. 

Digital timers of excellent quality that are based on crystal oscillators are available. The resonant frequency of such oscillators is temperature dependent and subject to aging effects, but the state of the art is highly developed. Crystal-controlled clock oscillators having a maximum error of 1 ppm at 25°C are commercially available from a number of manufacturers. Some units are tem-... 

Fig. 1.19. The spiral-type movement of the macroscopic magnetization vector subject to the simultaneous action of an external static magnetic field and of an r.f. field rotating at the resonance frequency.

The information of an EPR spectrum is contained in (i) the resonance frequency (in practice the g value), (ii) the line shape or spectral structure, and (iii) the relaxation behaviour. Comparison of the characteristic parameters with those of known species often leads to identification of the paramagnetic entity under investigation. More fundamentally, they give insight into the magnetic interactions to which the unpaired electron is subjected, and thus into the structure of its environment. In actuality, the stick spectrum of Fig. Ic will consist of resonances with Lorentzian line shape in the case of individual transitions as in Fig. 1, or with Gaussian line shape when many different unresolved hyperfine interactions are... 

Serious complications arise, however, if the spins are subject to strong nuclear electric quadrupolar interactions, which tend to modify the echo amplitudes measured. In such cases, it is still possible to extract dipole-dipole coupling information from spin echo decay spectroscopy, if the 71-pulses are applied entirely selectively to the central l/2>o -l/2> transition [6]. If the resonance frequencies between the coupled nuclei are sufficiently similar to allow for spin-exchange via the flip-flop mechanism, Eq. (5) turns into... 

The metabolic pathways of 5-FU and its prodrugs have been well characterized in the liver as well as in liver tumors and metastases by in vivo 19F MR spectroscopy. The liver and extrahepatic spaces catabolize 5-FU, which is subsequently excreted in the urine [3-5, 7-10, 46, 59], Active metabolites (fluoronucleotides) are created by anabolism in tumors. Even though clinical studies showed significant individual subject variations [3, 5, 7-10, 26,46,47], spectral characteristics such as resonance frequency, linewidth, relaxation time, and amplitude were not related to the therapeutic response. However, dynamic processes, specifically the accumulation and retention of 5-FU in the tumor, were indicative of response. Patients showing tumor half-lives of free 5-FU of 20 minutes or longer observed in patients were characterized by Wolff el al. [47, 53] as trappers. While over 50% of the evaluated population were nontrappers, approximately 60% of the patients who responded to therapy were trappers [3-5, 7-10],... 

Refinement refers to efforts to make experimental design as painless and efficient as possible in order to minimise the suffering of each animal subject. One of these refinements consist of non-invasive resonance frequency analysis (RFA) to assess the osseointegration of implants. Roze, Hoornaert and Layrolle (2014) found good correlation between the histomorphometric parameters implant stability quotient (ISQ) and bone growth around the implants (bone surface/tissue surface BS/TS 0.5 mm), and RFA of cylindrical Ti implants inserted bilaterally into the femoral epiphyses of rabbits, thus confirming that RFA may be a useful technique to determine the quality of bone apposition. 

As shown by Equation A measurement of electron concentration reduces to measurement of changes in the resonant frequency of a micro-wave cavity. The early approaches involved a point-by-point method (2) of following the decay of concentration and hence were slow and subject to error. In more recent work (7) the detection cavity formed part of a frequency discriminator thereby providing an output proportional to cavity frequency. The technique used in the work reported here is an obvious extension of this approach. 

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