RC low-pass two-pole

Osmotic Pressure Controlled Oral Tablets. Alza Corp. has developed a system that is dependent on osmotic pressure developed within a tablet. The core of the tablet is the water-soluble dmg encapsulated in a hydrophobic, semipermeable membrane. Water enters the tablet through the membrane and dissolves the dmg creating a greater osmotic pressure within the tablet. The dmg solution exits at a zero-order rate through a laser drilled hole in the membrane. Should the dmg itself be unable to provide sufficient osmotic pressure to create the necessary pressure gradient, other water-soluble salts or a layer of polymer can be added to the dmg layer. The polymer swells and pushes the dmg solution through the orifice in what is known as a push-pull system (Fig. 3). The exhausted dmg unit then passes out of the body in fecal matter.  [c.231]

Fig. 3. (a) Cross section of the push-pull oral osmotic system (OROS), which has an inner flexible partition to segregate the osmotic propellant from the dmg compartment, (b) Push-pull OROS in operation with the propellant imbibing water, increasing in volume, and pushing the dmg out of the device  [c.232]

Fig. 8. Example of a Push-Pull osmotic pump where (a) represents the pump before operation, and (b), during operation. Fig. 8. Example of a Push-Pull osmotic pump where (a) represents the pump before operation, and (b), during operation.
Phase Changes at the Soil—Bath Interface. Closely related to solubilization is a phenomenon that involves polar organic sods and surfactant solutions. If a complete phase diagram is plotted for a ternary system containing sodium dodecyl sulfate (or glycerol oleate), and water, several important and unusual features are noted. A large area represents a Hquid phase consisting of a microemulsion, where the dispersed particles are so small that the system is isotropic, like the familiar soluble ods. Also, over another large area, a Hquid crystalline phase is formed, containing all three components. This Hquid crystalline phase flows like a Hquid, at least in one direction. Flow perpendicular to the oriented planes is accompHshed by folding the planes cylindricaHy, but the physical flow is stiU of the purely viscous type, with no yield point evident. These two phases, particularly the Hquid—crystal phase, play an important part in detergency (85). Furthermore, Hquid—crystal formation lowers interfacial tension (86). Although this phenomenon was demonstrated in tertiary oil recovery, the principles could also apply to oily-soil detergency.  [c.535]

Fig. 5. (a) Cross-section of the push-pull OROS, which has an inner flexible partition to segregate the osmotic propellant from the dmg compartment, (b) Push-pull OROS in operation with the propellant imbibing water, increasing in volume, and pushing the dmg out of the device through the deflvery orifice  [c.232]

The tablet consists of an oral osmotic system based upon the push-pull design (81). The osmoticaHy active dmg core is surrounded by a semipermeable membrane, possibly cellulose acetate [9004-40-6]. The core itself is divided into two regions, ie, a region containing dmg and a push region containing pharmacologically inert but osmoticaHy active components (Fig. 5). As water from the gastrointestinal tract enters the tablet, pressure increases in the osmotic region and pushes against the dmg region, releasing dmg through the precision laser-drilled tablet orifice in the active region. Upon swallowing, the biologically inert components of the tablet remain intact during GI transit, and are elirninated in the feces as an insoluble shell.  [c.232]

Pressure-negative (push-pull) combination system normally used when conveying from several pickup points to several discharge points.  [c.203]

Figure 3-14 The push-pull converter. Figure 3-14 The push-pull converter.
The first type of source is characterized by contaminant diffusion in the room in all directions due to the concentration gradient in all directions (e.g., emission from a painted surface). The emission rate in this case is significantly affected by the intensity of the ambient air turbulence and air velocity. With the second type of source, contaminants move in the space primarily due to heat energy as buoyant plumes over the heated surfaces. The third type of source is characterized by contaminant movement in a space with an air jet (e.g., a linear jet over the tank with push-pull ventilation) or particle flow from a grinding wheel. In some cases these factors influencing contaminant distribution are combined.  [c.542]

Push-Pull Ventilation of Open Surface Tanks 944  [c.809]

BEOs are most often used for point sources or small line or surface sources. See Chapter 7 for descriptions of sources. BEOs are sometimes used for lines or surfaces when the source is moving along the line or on the surface. This naturally demands the exhaust to move with (or be moved with) the source movements (e.g., during painting or seam welding). They have also been used for side suction from baths and tanks-- and these exhausts are usually called rim exhausts see Rim Exhausts. However, for these sources push-pull systems (Section 10.4.3) are often more efficient. Side hoods can also be used, e.g., when molten metal is poured however, in these cases an enclosed exhaust is more efficient.  [c.828]

Rim exhausts are suitable for area sources of contaminant. They are limited in the area over which they can draw with adequate velocity. In practice, the slot hood should be within 0.6 m of the far edge of the source. For an open surface tank this means that a slot hood on one long side is necessary for tanks up to 0.6 m in width hoods on both long sides are necessary for tanks up to 1.2 m in width and rim exhaust is not practical for tanks wider than 1.2 m. For those situations, push-pull ventilation or enclosure type hoods are recommended.-  [c.849]

For a push-pull system, the source is usually an open surface tank and the airflow acts as a horizontal curtain above the surface. In this case, the person could be anywhere as long as the system works as intended and the curtain is not broken. The curtain will be broken when parts or material are lifted out of or placed into the bath and the contaminants could be spread either through convection or because the supply air blows against the material or part.  [c.936]

Push-Pull Ventilation of Open Surface Tanks  [c.944]

In these cases, push-pull ventilation offers an appropriate mechanism for reducing the overall flow rate required, compared with side exhaust, by up to 50%, while still maintaining dear overhead access.  [c.944]

Push-pull ventilation systems for open surface tanks consist of two components the push flow is generated by a jet or series of jets that are blown across the surface of the tank towards an exhaust hood along one side of the tank, which pulls and removes the fluid from the jet containing the contaminant. This is shown schematically in Fig. 10.69.  [c.944]

This section deals mainly with side push-pull ventilation. Center push-pull ventilation is also sometimes used, where two jets of air are blown from a central pipe towards two parallel exhaust hoods at opposite ends of the tank. Much of what vve say about side push-pull systems is equally valid to center push-pull.  [c.944]

FIGURE (0.69 Schematic diagram of side push-pull system.  [c.944]

A number of workers at Pennsylvania State University examined the push-pull system and found good agreement between their numerical and experimental work. The computational algorithm SIMPLER was used to solve the flow in the two-dimensional push-pull system and it was concluded that for a tank 1.8 m long, the push jet must have an initial velocity of 3.8 m s, that the exhaust flow rate per unit width should be 0.495 m s", and that the ratio of the pull to push flow rates, q /qj, must be between 8.8 and 17.8.  [c.945]

Flynn et al." applied a finite element based numerical model to solve the problem of a push-pull flow with cross-drafts and demonstrate that the results show good agreement with experimental data. They note, however, that the numerical method is time consuming and therefore computationally expensive.  [c.945]

Flow Patterns Induced by a Push-Pull System  [c.945]

Collectively, for the sake of brevity, we refer to Eqs. (10.92) to (10.96) as the original Verhoff formulae. A numerical analysis of the wall jet in the push-pull situation suggests that the Verhoff formulae fit the numerical data more closely if the following constants are taken  [c.947]

Ingham. - This gives the required minimum value for the momentum ol the equivalent wall jet we must also recall the relationship shown in Fig. 10.72 to determine the required momentum of the offset jet in the push-pull system.  [c.953]

Even with modem CFD commercial software packages, achieving accurate results for a full numerical model for the push-pull system is time consuming because of the very fine grid required close to the jet nozzle and close to the surface of the tank. With the techniques described in this section, it is possible to produce at least first estimates of the required parameters for a given push-pull system. It is then recommended that a designer would conduct full numerical testing of the system at the suggested operating parameters and make final adjustments according to those results. Finally, when the system is installed, it is important to allow for some adjustment of the operating parameters following in situ testing of the ventilation system.  [c.955]

The flow ratio method was first suggested for use in designing receptor hoods and then it was suggested for design of push-pull systems. The concept of the method is described as follows.  [c.971]

Figure 10.87 shows the fundamental operation of the push-pull flow. The suction hood should simultaneously exhaust the pushed air (contaminated supply  [c.971]

In designing the push-pull hood, one always applies a safety factor, , resulting in the exhaust flow rate for design, which is expressed as the following  [c.972]

The limit value of the flow ratio, K , is expressed as the following experimental equation for two-dimensional push-pull flows  [c.972]

The many possible oxidation states of the actinides up to americium make the chemistry of their compounds rather extensive and complicated. Taking plutonium as an example, it exhibits oxidation states of -E 3, -E 4, +5 and -E 6, four being the most stable oxidation state. These states are all known in solution, for example Pu" as Pu ", and Pu as PuOj. PuOl" is analogous to UO , which is the stable uranium ion in solution. Each oxidation state is characterised by a different colour, for example PuOj is pink, but change of oxidation state and disproportionation can occur very readily between the various states. The chemistry in solution is also complicated by the ease of complex formation. However, plutonium can also form compounds such as oxides, carbides, nitrides and anhydrous halides which do not involve reactions in solution. Hence for example, it forms a violet fluoride, PuFj. and a brown fluoride. Pup4 a monoxide, PuO (probably an interstitial compound), and a stable dioxide, PUO2. The dioxide was the first compound of an artificial element to be separated in a weighable amount and the first to be identified by X-ray diffraction methods.  [c.444]

Developments. A variety of process modifications aimed at improving surface finish or weld line integrity have been described. They include gas assisted, co-injection, fusible core, multiple Hve feed, and push—pull injection mol ding (46,47). An important development includes computer-aided design (CAD) methods, wherein a proposed mold design is simulated by a computer and the melt flow through it is analy2ed (48).  [c.142]

Another type of osmotic device has the osmotic agent and the dmg in separate layers (Fig. 8). Incoming water causes the osmotic layer to hydrate and expand and the dmg layer gradually to go into solution or suspension. The dissolved or suspended dmg is released from the system oriftce(s). The net effect is to release the dmg at a zero-order rate. This Push-Pull system can release a variety of compounds, ranging from highly soluble dmgs to insoluble dmgs suspended in osmotic hydrogel carriers or in carriers that solvate at body temperature. Procardia XL, dehvering nifedipine for angina and hypertension, is a Push-Pull osmotic system.  [c.146]

Ring opening reactions of aziridines which are initiated by nucleophilic reagents have been shown to proceed with extensive, if not complete, inversion of configuration at the point of attack (S7JA734). When unsymmetrical aziridines are involved, ring opening can occur in either of two different directions. Frequently, the nucleophile attacks the less hindered carbon atom preferably with the result that one direction of ring opening is predominant (S9CRV737). However, such reactions are generally difficult to predict because the product ratio can easily be affected by changes in the solvent and in the proportion of the reagents. The diverse and often seemingly contradictory facts pertaining to the opening of this strained ring can be correlated in terms of a push-pull mechanism (64HC(19-1)524). According to this concept the major factors involved in such processes are approach of the nucleophilic reagent, the rupture of the C—X bond, and the effect of the electrophilic reagent. As a result, steric factors are less influential than usual, while sensitivity to factors such as solvent, resonance and the presence of electron releasing substituents is substantially increased.  [c.70]

The amplifier network provides signal conversion and suitable static and dynamic compensation for good positioner performance. Control from this block usually reduces down to a form of proportional or proportional plus derivative control. The output from this block in the case of a pneumatic positioner is a single connection to the spring and diaphragm actuator or two connections for push-pull operation of a springless piston acduator. The action of the amplifier network and the action of the stem-position feedback can be reversed together to provide for reversed positioner action.  [c.783]

T e flyback topology (see Figure 3-f2) is the favorite below fOO to f50W because of its low parts count (hence cost) and intrinsically better efficiency. But because its peak currents are much higher than the forward-mode converters, it reaches the SOA limits of the power switches at a relatively low output power. Between an output power of f50 and 500 W the half-bridge (see Figure 3-f5) becomes the favorite. The parts cost more but they are still reasonable. The half-bridge converter only places one-half of the input voltage across the primary winding and therefore exliibits fairly high peak currents. It therefore is only used to 500 W or less. Above 500 W and into many kilowatts, the full-bridge (see Figure 3-16) topology is used. This requires four power switches, two of which have floating drive circuits, and is the most costly to implement, but at these output power levels the added cost is necessary. The push-pull (see Figure 3-14) can also be used in this region, but it suffers from a potentially severe failure mode called core imbalance. This is where the flux within the transformer will operate non-symmetrically about a zero balance point. This will cause the  [c.29]

The eommon topologies whieh are eneompassed under this eategory are the buek, half-forward, push-pull, half and full bridge, with only the traditional voltage-mode eontrol method. Its representative eireuit diagram is given in  [c.201]

When using an inductor or transformer within a switching power supply, the core is never operated to the point of saturation. Instead it is operated in what is called a minor loop. These are B-H curves that are wholly contained within the boundary of the saturated B-H curve. In 20 to 50 kHz PWM switching power supplies, the peak excursion of the flux density (B, ) is usually half of the saturation flux density (Bsat)- This results in a core loss of two percent in overall converter efficiency, which is considered acceptable. For higher frequencies of operation, should be lowered to keep the core losses at or below two percent loss of efficiency. The common minor-loop curves are seen in Figure D-3. Curve A is the B-H curve within the transformer of a push-pull style forward converter such as the push-pull, half-bridge, and full-bridge converters. Curve B is the B-H curve of a discontinuous-mode flyback converter. Curve C is the B-H operation of a forward-mode filter choke and a flyback transformer operating in the continuous-mode. For dc and unipolar flux applications, it is desirable to place a small air-gap within the magnetic path of the core. Its effect on the B-H curve can be seen in Figure D-3. As one can notice, the permeability of the overall inductor drops. This drop is in proportion to the length of the air-gap introduced. This offers an advantage to the inductor s or transformer s operation in that it requires a greater current through the drive winding to drive the core s flux density to enter a state of saturation. Most of the energy placed within the core is now stored in the air-gap and the result is the flux density within the magnetic core material drops. For these applications, additional turns will have to be added to the core to maintain the same  [c.235]

To partition the incoming X rays into their proper energy channels, it is necessary to measure only single pulses. At high count rates, however, situations ofren arise where a second pulse reaches the main amplifier during the rise time of the preceding pulse. The two pulses may then combined into a single pulse whose eneigy is the combined energy of the two individual pulses. This process is known as pulse pile-up and the output, which is an artifact, is called a sum peak. Pile-up effects can be minimized with the use of electronic pulse rejection using a second pulse amplifier with a much faster response. Operationally, it is usually desirable to collect spectra with a dead time of less than 40%, or at an input count rate of about 5000 cps.  [c.124]

Airborne contaminant movement in the building depends upon the type of heat and contaminant sources, which can be classified as (1) buoyant (e.g., heat) sources, (2) nonbuoyant (diffusion) sources, and (d) dynamic sources.- With the first type of sources, contaminants move in the space primarily due to the heat energy as buoyant plumes over the heated surfaces. The second type of sources is characterized by cimtaminant diffusion in the room in all directions due to the concentration gradient in all directions (e.g., in the case of emission from painted surfaces). The emission rare in this case is significantly affected by the intensity of the ambient air turbulence and air velocity, dhe third type of sources is characterized by contaminant movement in the space with an air jet (e.g., linear jet over the tank with a push-pull ventilation), or particle flow (e.g., from a grinding wheel). In some cases, the above factors influencing contaminant distribution in the room are combined.  [c.419]

More recently, in the middle 1990s, the UK s Health and Safety Executive (HSE) also reviewed the push-pull system. Hollis and Fletcher offer a comprehensive literature review on push-pull ventilation and note that the main conclusions of previous work on push-pull ventilation of tanks are that the control is primarily supplied by the inlet jet, forming a wall jet along the surface of the tank, and that the main purpose of the exhaust hood is to remove the air and contaminant contained within the push jet.  [c.945]

The ACGIH " gives recommendations for the design of a push-pull system, apparently based largely on the work of NIOSH in the 1980s the nozzle should be between 3.2 mm and 6.4 mm and that the so-called momentum factor of the jet, the product of its velocity and flow rate per unit width, U,ij should be between 0.39 and 0.59 m s -. The outlet flow rate may then be calculated using the formula  [c.945]

See pages that mention the term RC low-pass two-pole : [c.29]    [c.36]    [c.36]    [c.37]    [c.57]    [c.917]    [c.945]    [c.969]   
Power supply cookbook (2001) -- [ c.198 ]