Flow rate dependence

The surface overflow rate (SOR) for piimaiy sedimentation is normally held close to 40.74 mV(m day) [1000 gal/(ft day)] for average flow rates, depending upon the solids characteristics. Lowering the SOR below 40.74 mv(m day) does not produce improved effluent... 

The simplest calibration procedure for a gas flow-measuring device is to connect it in series with a reference meter and allow the same flow to pass th tough both instruments. This requires a reference instrument of better metrological quality than the calibrated instrument. One fact to consider when applying this method is that the mass flow rate in the system containing both instruments is constant (assuming no leakage), but the volume flow rate is not. The volume flow rate depends on the fluid density and the density depends on the pressure and the temperature. The correct way to calibrate is to compare either the measured mass... 

The volumetric flow rate depends on the total molar flow of the gas, and the temperature and pressure of reaction, where... 

Thus, in an isothermal system, the mass flow rate depends on the difference in pressures of the gas across the orifice and does not depend upon the thickness of the plate. One may define an area-normalized resistance, R, for mass transfer through the orifice using a generalization of Ohm s law, i.e., Resistance = force/ flux. For Knudsen flow, the force is the pressure difference (analogous to voltage difference in Ohm s law) and the flux is the mass flow per unit area of the hole (analogous to the electrical current density in Ohm s law). Thus, we have... 

Accordingly, for a given capillary pressure in a porous medium there will be a specific foam flow rate at which the lamellae rupture. This is the proposed origin of the flow-rate dependence... 

The inlet flow rate depends on time according to F = 1 + 0.2 sin(t)... 

It is only in regime 1 that the flow rate depends on the back pressure. It will be noticed that this is only a small part of the nozzle s range of operation. Once the sonic speed has been reached at the throat (at the pressure P ), the flow becomes choked and the flow rate remains constant, for constant supply conditions, and is independent of the back pressure. 

Reversed-phase separations currently dominate in CEC. As a result, the vast majority of the mobile phases are mixtures of water and an organic solvent, typically acetonitrile or methanol. In addition to the modulation of the retention, the mobile phase in CEC also conducts electricity and must contain mobile ions. This is achieved by using aqueous mixtures of salts instead of pure water. The discussion in Sect. 2 of this chapter indicated that the electro osmotic flow is created by ionized functionalities. The extent of ionization of these functionalities that directly affects the flow rate depends on the pH value of the mobile phase. Therefore, the mobile phase must be buffered to a pH that is desired to achieve the optimal flow velocity. Obviously there are at least three parameters of the mobile phase that have to be controlled (i) percentage of the organic solvent, (ii) the ionic strength of the aqueous component, and (iii) its pH value. 

P. Agrafiotu, C. Maliakas, A. Pappa-Louisi and S. Sotiropoulos, A general approach to the derivation of peak area flow rate dependence in FIA and HPLC amperometric detection. Electrochim. Acta 48 (2003) 2447-2462. 

Surprisingly enongh, the above processes are very fast and separation of macromolecnles on this principle can be considered an equilibrium process. The precise measurements of retention volumes of polymers under conditions of their partial pore permeation in absence of enthalpic interaction did not reveal practically any effect of the eluent flow rate [55]. On the contrary, in a review, Aubert and Tirrell [66] have demonstrated that the SEC exclusion volumes can be flow rate dependent due to both anomalous and physical effects. The former are caused by... 

Essentially, the above model is empirical as in real systems, both solid and fluid-film resistances play an important role in the adsorption process. An improved BDST model is found elsewhere (Ko et al., 2000, 2002). Finally, qm a and could be flow rate-dependent parameters (Walker and Weatherley, 1997). 

The choice of the appropriate flow rate depends on the wastewater volume to be treated and on the desired service time, and as presented in a following section, on the degree of utilization of the fixed-bed material. 

Fig. 17.3 Temperature and flow-rate dependence of silicon thin-film growth for a silane CVD process. The left-hand panel shows the temperature dependence for a fixed inlet flow rate. The right-hand panel shows normalized growth rate as a function of inlet velocity for three different surface temperatures. The actual growth rate at U = 10 cm/s is stated parenthetically under the temperature call out.

The requirements for these applications with respect to ozone concentration and flow rate depend on the application. For the cleaning process a liquid concentration of about 5 to 20 mg L 1 is normally mentioned, for photoresist removal much higher concentrations are required (50 mg L 1 and higher). 

The advantage of this extraction method is that the parameters pressure, temperature and solvent to feed ratio can be varied in each extraction step. By this way a very accurate fractionation of the different compounds included in the feed can be achieved. The solubility of the compounds in the supercritical fluid, depending on pressure and temperature, can be changed in each extraction step. The highly soluble substances are extracted in the first step at low fluid density. Increasing the density in the following extraction steps leads to the removal of the less soluble substances. Further, the flow rate of the supercritical fluid can be adjusted in each extraction step, either constant flow for each step or different flow rates, depending on the separation to be achieved. 

Radicals are generated at a tubular electrode and are then transported by laminar flow into the ESR cavity which, as a downstream detector, is analogous to a second electrode. The theoretical response for the cases where the radicals are stable or decompose by first- or second-order kinetics has been derived and experimentally confirmed [126, 301, 302]. The flow-rate dependence is different for each of the three situations which provides a diagnostic for the type of kinetics. Further information may be obtained from galvanostatic transients which allow the elucidation of electrode and radical surface processes [303]. Very recently, an in situ channel tube electrode has been described for electrochemical ESR which also allows shorter-lived species to be observed and smaller surface coverages to be analysed [304—306]. 

Incubation of the IgG-containing sample with the ligand matrix is not always necessary, but will allow maximal binding to occur. Alternatively, slowly pump the sample through the column. Flow rate depends on the IgG concentration in the sample, and the binding capacity and size of the affinity column. 

The inlet flow rate depends on time according to... 

Reaction scheme of photocatalytic decomposition of acetic acid under deaerated condition is analyzed based on the flow-rate dependence of the radical fomiation30) combined with the reported mechanism. In this scheme, CH3 radicals are formed via two reaction pathways. One is indirect oxidation via OH radicals which are formed by the oxidation of water with photoinduced holes (h+) at the valence band. Another is direct oxidation of adsorbed molecules by the hole. On the other hand, 011200011 radicals are not formed by direct oxidation but only by indirect oxidation via 0H radicals. The reaction scheme is proposed as illustrated in Fig. 5.7. 

Air-pressure-driven active devices. Air-pressure-driven aerosolization is the concept employed in a number of devices currently in different stages of development with drugs for local or systemic action. These devices rely on a small patient-operated air pump. Air is compressed by mechanical means (piston or bellows) and is released on the external trigger given by the patient s inspiratory cycle. Because of the use of this air pump, these devices have an active aerosolization mechanism and are assumed to be less flow-rate-dependent than passive DPI devices. 

Two factors are driving the market for precise, very-low-flow HPLC pumping systems extremely limited sample sizes in biotechnology and the electrospray and nanospray interfaces that are concentration and flow-rate dependent. It is very difficult to get precise flow and gradient formation from pumps that have a 5- to 10-/iL plunger displacement, even using 3200-step stepper motor drives. This has forced manufacturers to resurrect a very old concept from the earliest days of HPLC, the syringe pump. 

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