Frequency weighting

The calculation of atmospheric transport with its many parameters and frequency weighting of the wind rose is practical only with a computer code. Table 8.3-6... 

Gastrointestinal symptoms occur frequently with the administration of ethosuximide (Zarontin), methsux-imide (Celontin Kapseals), and phensuximide (Milontin Kapseals). Mental confusion and other personality changes, pruritus, urticaria, urinary frequency, weight loss, and hematologic changes may also be seen. 

The criterion employed for a positive response in this assay is a reproducible statistically significant increase in mutation frequency (weighted mean for duplicate treated cultures) over the concurrent vehicle control value (weighted mean for four independent control cultures). Ideally, the response should show evidence of a dose-response relationship. When a small isolated significant increase in mutation frequency is observed in only one of the two duplicate experiments, then a third test should be carried out. If the third test shows no significant effects, the initial increase is likely to be a chance result. In cases where an apparent treatment-related increase is thought to be a result of unusually low variability or a low control frequency, comparison with the laboratory historical control frequency may be justified. 

Bartlett et alP exposed 194 young rats (3-4 weeks old) continuously to ozone at 0.2 ppm for 28-32 days and observed that there was no effect on respiratory frequency, weight gain, tail-length increase, and external appearance in the ozone-exposed group and that, although both ozone-exposed and control groups looked healthy, 12 ozone-exposed and 11 control animals had pneumonitis at the end of the exposure period. The results with the latter animals were discarded in the later data analysis. 

As the separation in the time scales between the particle and the bath becomes less severe, the assumption that yo is local breaks down, though it may still be stationary. This results in a frequency-weighted spectral density. 

All of the spectra in Fig. 13 appear to have two bands one at low frequency and one at high frequency. The spectra often can be fit reasonably well to the sum of a frequency-weighted exponential that peaks at low frequency,... 

The job severity index (JSI) is a time- and frequency-weighted ratio of worker capacity to job demands. Worker capacity is predicted with the models developed by Ayoub et al. (1978), which use isometric strength and anthropometric data to predict psychophysiceil lifting capacity. JSI and each of the components are defined below. 

The term noise refers to any unwanted sound, either a pure tone or a mixture of frequencies. Since the sensitivity of the ear is frequency dependent, as illustrated by the above table, noise level is expressed in a frequency-weighted scale, known as A-weighting. Decibel readings on this scale are designated as dBa. Typical noise levels from various sources are illustrated in this table ... 

Finally it seems interesting to compare the LO(L) frequencies as measured by Raman and neutron scattering (see table 3). The neutron scattering value of the LO(L) phonon frequency is soft compared to that measured by Raman scattering. The neutron LO(L) phonon frequency, on the other hand, compares quite well with the average of the Raman LO(L) phonon frequency and the boimd state frequency weighted by the scattering intensity. 

Frequency Weighting. The inverse frequency contour (i.e., reciprocal) to an equinoxious contour should be applied to a stimulus containing many frequencies to produce an overall magnitude that appropriately combines the contributions from each fr uency. The frequency weightings most commonly employed for whole-body and hand-transmitted vibration are shown in Fig. 10.1 (ISO 2631-1,1997 ISO 5349-1, 2001). The range of frequencies is from 1 to 80 Hz for whole-body vibration, and from 8 to 1250 Hz for vibration entering the hand. A frequency weighting for shocks may also be derived from a biodynamic model (see Dynamic Response Index (DRI) in Sec. 10.3.1). 

FIGURE 10.1 Frequency weightings for whole-body (W, and WJ and hand-transmitted 0V ) vibration. and Wj are for the z direction and X and y directions, respectively, and are applicable to seated and standing persons (see Fig. 10.2). IF ) is for all directions of vibration entering the hand. The filters are applied to acceleration-time histories a t). ISO 2631-I, I997 ISO 5349-1,2001.)... 

There is extensive literature on the occurrence of health effects and injury from exposure to vibration, shock, and impact, which has been reviewed recently (von Gierke et al 2002) and serves as the basis for the present discussion. Estimates of exposures necessary for common human responses and health effects are summarized in Table 10.2 for healthy adults the interested reader is directed to the references given in the table for more complete information, or to the recent review article cited. Included in Table 10.2 are the metric used for assessing the exposure, the frequency weighting of the stimidus, and a representative value for the response or health effect under consideration. As already noted, there are large variations between individuals in response, and susceptibility, to vi-bratirHi, shock, and impact. 

Vibration Perception. The perception of vibration depends on the body site and on the stimulus firequency. The thresholds in Table 10.2 are typical of those for healthy adults, and are expressed as instantaneous RMS accelerations (i.e., with T 1 s in Eq. (10.2)). The value for whole-body vibration is given in terms of a frequency-weighted acceleration, and so is applicable to vibration at frequencies from 1 to 80 Hz. The values for hand-transmitted vibration are for sinusoidal stimuli applied to the fingertips of males (M) and females (F) at the specified frequencies. 

EXAMPLE 10.2 A worker uses a percussive rock drill for 3 hours daily. Measuremeta of the handle vibration indicates a frequency-weighted RMS acceleration of 18 mJs along the drill axis, and a frequency-weighted RMS acceleration of 5 mJs perpendicular to this axis. Estimate the 8-hour daily exposure. 

The assessment of whole-body vibration onploys the VDV averaged over 8 hours [i.e., T = 28,800 s in Eq. (10.6)], with fiequency weighting for vertical vibration and frequency weighting Wj for horizontal vibration. It is believed that the higher-power metrics, as recommended here, better represent the hazard presented by motion containing transient events, particularly when these become small-magnitude shocks or impacts. The most appropriate metric, however, remains a subject for research. 

A weighted sound-pressure level obtained by use of metering characteristics and the weighting A, B, or C as specified in American National Standards Institute (ANSI) Standard S1.4, Specifications for Sound Level Meters. If the frequency weighting employed is not indicated, A-weighting is usually implied. 

A device to measure instant noise levels. It is comprised of a microphone, amplifier, output meter, and frequency-weighting networks, which are used for the measurement of noise and sound levels. Sound-level meters are often made with various filtering networks that measure the sound directly on A, B, C, etc., scales. Sound-level meters may also incorporate octave-band filters for measuring sound directly in octave bands. Since sound levels are specific to the areas being measured, the sound levels are called area sampling. Sound level meters used for measuring noise for compliance requirements must meet American National Standards Institute (ANSI) Standard S1.4, Specifications for Sound Level Meters. See also Noise Dosimeter Weighted Measurements. 

TABLE 23-5 Frequency Weighting Adjustments for Converting Sound Pressure Levels to A Scale Readings... 

Type of quantity A cumulable quantity, like volume, number, or (ideally) scattering intensity of the particle system, which is used to quantify the frequency (weights) of... 

The subsimilarity search method developed at the Upjohn Company, which is discussed later, measures the similarity between a pair of molecules by the maximal common substructure (MCS), that is, the largest substructure that is common to the two molecules that are being compared, as illustrated in Figure 4. The system utilizes an inverse-frequency weighting scheme that favors heteroatom-heteroatom pairs over the mote frequently occurring carbon-carbon pairs. For each pair of heteroatoms separated by minimum paths of two to six bonds, an additional bond is added to link the atoms directly. This additional link results in an increase in the size of the MCS and thus a greater similarity for heteroatom-containing common substructures. 

Frequency weighting Weighting for loudness and type of sound by means of various weighting networks fitted in the sound level meter mainly these are the A, B, C and D weightings (weighting curves are given in DIN 45633). 

Arif SM, Holiday JD, Willett P (2010) Inverse frequency weighting of fragments for similarity-based virtual screening. J Chem Inf Model 50 1340-1349... 

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