Signature domain

Figure43.5 Typical frequency-domain vibration signature...

A frequency-domain vibration signature is generally used for the analysis because it is comprised of discrete peaks, each representing a specific vibration source. 

Vibration does not just happen. There is a physical cause, referred to as a forcing function, and each component of a vibration signature has its own forcing function. The components that make up a signature are reflected as discrete peaks in the TFT or frequency-domain plot. 

As shown previously, vibrations can be displayed graphically as plots which are referred to as vibration profiles or signatures. These plots are based on measurable parameters (i.e., frequency and amplitude). Note that the terms profile and signature are sometimes used interchangeably by industry. In this chapter, however, profile is used to refer either to time-domain (also may be called time trace or waveform) or frequency-domain plots. The term signature refers to a frequency-domain plot. 

Actual time-domain vibration signatures are commonly referred to as time traces or time plots (see Figure 43.17). Theoretical vibration data are generally referred to as waveforms (see Figure 43.18). 

In order to analyze this type of plot, the analyst must manually change the time scale to obtain discrete frequency curve data. The time interval between the recurrences of each frequency can then be measured. In this way, it is possible to isolate each of the frequencies that make up the time-domain vibration signature. 

With frequency-domain analysis, the average spectmm for a machine-train signature can be obtained. Recurring peaks can be normalized to present an accurate representation of the machine-train condition. Figure 43.20 illustrates a simplified relationship between the two methods (i.e., time-domain and frequency-domain). 

Comparative analysis directly compares two or more data sets in order to detect changes in the operating condition of mechanical or process systems. This type of analysis is limited to the direct comparison of the time-domain or frequency-domain signature generated by a machine. The method does not determine the actual dynamics of the system. Typically, the following data are used for this purpose (1) baseline data, (2) known machine condition, or (3) industrial reference data. 

Most predictive-maintenance programs rely almost exclusively on frequency-domain vibration data. The microprocessor-based analyzers gather time-domain data and automatically convert it using Fast Fourier Transform (FFT) to frequency-domain data. A frequency-domain signature shows the machine s individual frequency components, or peaks. 

The frequency-domain, or TFT, signature acquired at each measurement point is an actual representation of the individual machine-train component s motion at that point on the machine. Without knowing the specific location and orientation, it is difficult - if not impossible - to correctly identify incipient problems. In simple terms, the TFT signature is a photograph of the mechanical motion of a machine-train in a specific direction and at a specific point and time. 

The first method uses high-frequency vibration components that result from oscillating rotor bars. Typically, these frequencies are well above the normal maximum frequency used to establish the broadband signature. If this is the case, a high-pass filter such as high-frequency domain can be used to monitor the condition of the rotor bars. 

Inward Rectifier K Channels. Figure 4 Kir channel subunits consist of two transmembrane domains (M1, M2), separated by a pore loop (P-loop) that contains the signature K+-selectivity sequence (-GYG-), as well as extended cytoplasmic N - and C-termini. Several residues (indicated) have been implicated in causing rectification (see text). 

Computer applications allow for defining and managing several important nonclinical data types that are managed by the system itself. Such data are referred to as metadata or control data. These are information such as domain-specific descriptions, application conditions, parameters, and methods in a repository. Control data fields can be part of the data collection forms or in system-defined tables. Some of these control fields include electronic signatures, form status, transmission date, transmission number, field completed, and memo fields (large text format). The database contains tables for reference ranges, visit schedule, form schedule, labels, and drug codes. 

Hart SR (1988) Heterogeneous mantle domains signatures, genesis and mixing chronologies. Earth Planet Sci Lett 90 273-296... 

An endoscope, coupled with video rate wide field imager, operating in either the time or frequency domain [92] could be an invaluable tool for early detection of cancer or possibly other diseases whose AF signatures are yet to be studied. 

The characteristic Walker A and Walker B motifs that are involved in ATP binding [144] are always found in the ATPase or ABC domains. In addition, a signature motif, also called the LSGGQ motif, is typical of all bacterial ABC domains involved in binding-protein-dependent import. The signature motif is absent in other types of ATPases. 

Medicine, 35, 215 (2005). Identification of Signatures in Biomedical Spectra using Domain Knowledge. 

Also identified during the mid-1990s was the APC (anaphase promoting complex - also known as the cyclosome), another multi-subunit cullin-containing E3 that mediates ubiquitylation of mitotic cyclins [18, 19]. Mdm2, initially thought to be a HECT domain variant, was shown in 1997 to have E3 activity towards p53 in vitro [20]. For the non-HECT E3s no common structural feature had been detected. Thus, by 1997 the only defined molecular signature for E3 activity was the HECT domain. 

From LEED measurements of H monolayers adsorbed on Fe(110) Imbihl et al. proposed a phase diagram as shown in Fig. IS. In addition to lattice gas and lattice fluid phases, two commensurate ordered phases were identifled, denoted as (2 x 1) and (3 x 1) in the figure (cf. Fig. 16). The shaded regions are interpreted as incommensurate phases or as phases composed of antiphase domains their signature is that the LEED spot does not occur at the Bragg position but rather the peak is splitted and satellites appear (Fig. 17). 

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