OTHER FILTERS

An inductor has an effect that is opposite to the capacitor s effect. This is shown in Fig. 11.3 (C and D), for direct comparison with their capacitor counterparts. 

The mathematical relationships are similar to those of a capacitor, but the inductor s effective resistance ( reactance ) is given by eqn. 10.3 on page 113. 

In this course, a second inductor other than the transformer would be needed to do experiments with inductive filters. That is not part of this simplified course, so such experiments will not be done, with the possible exception of an optional one in the diodes chapter. 

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The demodulation algorithm is very simple the DSP multiplies the received signal by each carrier, and then filters the result using a FIR filter. This kind of digital filter is phase linear, (constant group delay important for the EC combinations). Other filters may be programmed, other demodulation algorithms may be used. 

Other filters used for prefiltering account for lead- [22, 23] or drug-likeness [24-26], an appropriate ADMET profile [27-30], or favorable properties concerning receptor binding [31, 32]. 

Extra coarse 170-220 Filtration of very coarse materials. Gas dispersion, gas washing, and extractor beds. Support of other filter materials. 

The filter press has the advantage of simplicity, low capital cost, flexibility, and ability to operate at high pressure in either a cake-filter or a clarifying-filter application. Floor-space and headroom needs per unit of filter area are small, and capacity can be adjusted by adding or removing plates and frames. Filter presses are cleaned easily, and the filter medium is easily replaced. With proper operation a denser, drier cake compared with that of most other filters is obtained. 

The advantages of the tubular filter are that it uses an easily replaced filter medium, its filtration cycle can be interrupted and the shell can be emptied of prefilt at any time without loss of the cake, the cake is readily recoverable in dry form, and the inside of the filter is conveniently accessible. There is also no unfiltered heel. Disadvantages are the necessity and attendant labor requirements of emptying by hand and replacing the filter media and the tendency for neavy solids to settle out in the header chamber. Applications are as a scavenger filter to remove fines not removed in a prior-filtration stage with a different land of equipment, to handle the runoff from other filters, and in semiworks and small-plant operations in which the filter s size, versatility, and cleanliness recommend it. 

Continuous Precoat Filters These filters may be operated as either pressure or vacuum filters, although vacuum operation is the prevailing one. The filters are really not continuous but have an extremely long batch cycle (1 to 10 days). Apphcations are for continuous clarification of liqmds from slurries containing 50 to 5000 ppm of solids when only very thin unacceptable cakes would form on other filters and where perfect clarity is required. 

Concentration of organic contaminants can affect the adsorption process. A given AC filter may be more effective than another type of AC filter at low contaminant concentrations, but may be less effective than the other filter at high concentrations. This type of behavior has been observed with chloroform removal. The filter manufacturer should be consulted to determine how the filter will perform for specific chemicals at different levels of contamination. 

Rapping A method used on bag or other filters to dislodge the dust cake from the fabric when the airflow resistance exceeds a certain value. 

Many other filter functions can be designed, e.g. an exponential or a trapezoidal function, or a band pass filter. As a rule exponential and trapezoidal filters perform better than cut-off filters, because an abrupt truncation of the Fourier coefficients may introduce artifacts, such as the annoying appearance of periodicities on the signal. The problem of choosing filter shapes is discussed in more detail by Lam and Isenhour [11] with references to a more thorough mathematical treatment of the subject. The expression for a band-pass filter is H v) = 1 for v j < v < else... 

Injections and infusion fluids must be manufactured in a manner that will minimize or eliminate extraneous particulate matter. Parenteral solutions are generally filtered through 0.22 pm membrane filters to achieve sterility and remove particulate matter. Prefiltration through a coarser filter is often necessary to maintain adequate flow rates, or to prevent clogging of the filters during large-scale manufacturing. A talc or carbon filtration aid (or other filter aids) may also be necessary. If talc is used, it should be pretreated with a dilute acid solution to remove surface alkali and metals. 

Apart from the delta filter discussed here, one can define other filters using the same Chebyshev operators. In fact, any analytic function of the Hamiltonian can be expressed as an expansion in terms of the Chebyshev operator.148 For instance, the Green filter can be expressed as follows 126,127 149... 

Again, a combined 13C, 15N-filter can also be constructed from other filtering elements, for example, a gradient-purging scheme [19]. 

Filterable through membrane and other filters <0.1 mioron = 1000 A... 

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