Low-pass filtering

Figure 4 General scheme for constructing N-steps low-pass J filters. Low-pass filtering process can be repeated and improved several times with different intervals t, r2,... in order to properly eliminate all Vch peaks when a wide range of one-bond coupling constants Vch is present in the molecule.

Coarse-Filtered One-Level Decomposition The coarse-filtered (low-pass)... 

Coarse-filtered (low-pass) wavelet coefficients C(l) of the first resolution level. 

These are, in alphabetical order, ash-free filters, bandpass filters, black band filters, blue band filters, broadband filters, cigarette filter, fluted filters, high-pass filters, low-pass filters, qualitative filters, and quantitative filters. The filter is catholic. In German, in chemistry the filter has neutral gender. In communication theory, the filter has male gender, however. 

In image processing, local filtering is used to increase the quality of an image. As a desired result, the image is smoothed and noise is removed. T3q)ical local filters are mean filter, low-pass filter, Gaussian filter, and median filter. Local averaging causes loss of spatial information. 

Figure 2.12(b,c) shows the equivalent RC circuit corresponding to the gas entrapped in a closed channel with liquid. It may be noted that RC circuit is commonly used for blocking certain frequencies of a signal, that is, high pass filter, low pass filter, and so on. 

The obtained signal is filtered with a low-pass filter having the cut-off frequency of 5Hz and a slope of 6 dB/octave. Since we are working with e.m.f modulus, the phase lag does not influence the control. 

The image generated by the image intensifier was found to be very sensitive to noise and to reduce this effect, a low pass filter was included. This filter has greatly improved the final 3D... 

And a rotation of the emitter-receiver transducer around the "object" (or a rotation of the object) gives a annulus of center O and radii [Km, Km] [2]. The situation is identical to that of X-ray tomography (slice-by-slice spectral coverage), but with a band-pass spectral filter instead of a low-pass spectral filter. ... 

In order to get an extremely high resolution and a small dead zone" (after the transmitter pulse) single amplifier states must have a bandwidth up to 90 MHz ( ), and a total bandwidth of 35 MHz (-3 dB) can be reached (HILL-SCAN 3010HF). High- and low-pass filters can be combined to band-passes and provide optimal A-scans. All parameters are controlled by software. 

The HILL-SCAN 30XX boards enable ultrasonic inspections from 50 kHz (concrete inspections) to 35 MHz (inspection of thin layers) with a signal to noise ratio up to 60 dB. The gain setting range of the receiver is 106 dB. High- and low pass filters in the receiver can be combined to band-passes, so that optimal A-scans are displayed. 

After the signal emerges from the lock-m amplifier it still contains a considerable amount of noise. Most of the noise contributions to the signal can be eliminated by passing the signal tlirough a low-pass filter. The filter tune constant is a measure of the cutoff frequency of the filter. If accurate linewidth and g-factor... 

The resolution of the analog I/O channels of the controller vaiy somewhat, with 12-bit and 14-bit conversions quite common. Sample rates for the majority of the constant sample rate controllers range from I to 10 samples/second. Hard-wired single-pole, low-pass filters are installed on the analog inputs to the controller to protect the sampler from aliasing errors. 

Sample times for the microprocessor-based SLCs vaiy from O.I to 0.4 seconds. Low-pass analog electronic filters are installed on the process inputs to stop abasing errors caused by fast changes in the process signal. Input filter time constants are typically in the range From O.I to I s. Microprocessor-based SLCs may be made part of a DCS by using the communication port (RS-488 is common) on the controller or may be operated in a standalone mode independent of the DCS. 

Low Pass Filter Two chambers are connected by a choke tube or pipe. At least one of the chambers should be connected to the compressor cylinder. Figures 13-lB and 13-lC. Melton offers a standardized, simple design that is useful for some types of package compressor arrangement. 

Figure 13-1B. Low pass filter. Two equal (usually) surge chambers connected by a choke-tube. This type of fii-ter does not have to be a common vessei as shown here. See Figure 13-1C.

Compressor Suction and Discharge Drums Design Method—Acoustic Low Pass Filters... 

After the anticipated disturbing frequencies have been determined, it is necessary to begin the sizing of the filter system. The cutoff frequency should be set at least one cycle per second below the lowest frequency to be filtered. The base frequency is determined from compressor speed and should be determined at the lowest anticipated compressor speed for variable-speed compressors. The following equation is used to determine cut-off frequency for a low-pass filter ... 

Melton, J. E, Low-Pass Filter Design for Gas Compressors Reduces Pulsation, Oil and GasJournal, p. 149, June 23, (1980). 

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