Pressure-time response curve

In a pressure-time dispensing system (see Section 8.3), the adhesive is forced under pressure through a valve so that the desired quantity is dispensed onto the component part. As the dispense valve opens and closes, the pressure-time response curve can be monitored just upstream of the nozzle tip. 

In order to use the dynamic response charts based on a triangular shaped load, the bilinear pressure-time curve shown in Figure 3.7 can be simplified to an equivalent triangle. This equivalent load is computed by equating the impulse for each load shape and using the same peak pressure, Pt. The impulse, I, under the bilinear pressure-time curve is ... 

This time the curve falls extremely slowly towards the new value. Given enough time, it will reach the baseline with no overshoot but clearly this type of response is unsuitable for measurement of a rapidly changing variable such as blood pressure. 

In a two-part series. Zeme discusses the importance of good separator hydraulics. A poor hydraulic design can make a good separation scheme ineffective. Zemel provides the methods and procedures to run a tracer test to identify short-circuiting, stagnant-flow regions, and shear forces. Analysis of the residence-time distribution curve that results is presented. Actual tests run on separators indicate that the most successful separator was the sequential dispersed-gas flotation cell, which closely followed the tanks-in-serie< model. This is contrasted with the poor performance of a conventional 2, 006-hbl [3 0-ms] wash tank The tracer responses of a pressurized flotation cell, a 15j000-bbl [2400 mJj wash tank, and a horizontal free-water knockout with and without baffles are also discussed. 

The general response of the sensor after changing the CO partial pressure at the working electrode is shown in Eigure 22, which is the response curve obtained after seven steps of auxiliary phase deposition for the first sample. When the CO partial pressure decreases at the working electrode, the emf of the cell increases dramatically at first and then slowly reaches an equilibrium value of 76 mV. The time to reach the equilibrium value is the recovery time of the sensor. The same is true when the partial pressure increases at the working electrode of the sensor, and the time to reach the equilibrium value is the response time of the sensor. In practice, researchers commonly use the time for... 

The efficacy and safety of salbutamol inhaled using a dry powder inhaler has been compared with salbutamol inhaled using a pressurized metered-dose inhaler (pMDI) in a randomized, open, crossover study in 12 patients with moderate to severe asthma. A total of 1600 micrograms of salbutamol was given on two separate days in a cumulative dose fashion in increments of 100,100,200, 400, and 800 micrograms at 3-minute intervals. FEVi rose progressively with each increment. The dose-response curves showed that powdered salbutamol was 3.0 times as potent (Cl = 1.8,5.8) as salbutamol from... 

Figure 6. Generalized hamster dose-response curves If the nitrogen partial pressure is high enough, the mortality will eventually go to 100%. However, with lower partial pressures the mortality rises to some asymptotic value after a constant time period. In this domain one can study the time effects independent of the nitrogen partial pressure.

Figure 6 shows three postulated dose-response curves that could be expected. In the curve marked high P. tissue, the ultimate response is 100% mortality because the inert gas partial pressure was so high that all animals were afflicted. If the depth of the dive is lowered (curves marked low P. tissue), the curve shifts to the right (towards increased exposure time) and flattens at a time In this range of pressures it is... 

Response times of 15-40 ms seem to be currently in use. Fry et al. (1957) analyzed the dynamic characteristics of three types of commercially available, differential-pressure pneumotachographs which employed concentric cylinders, screen mesh, and parallel plates for the air resistors. Using a high-quality, differential-pressure transducer with each, they measured total flow resistance ranging from 5 to 15 cm HjO. Frequency response curves taken on one model showed fairly uniform response to 40 Hz the second model showed a slight increase in response at 50 Hz, and the third exhibited a slight drop in response at this frequency. 

Figure 21.15 shows the transient response of the measured pressure shortly before and after the onset of the control. In Fig. 21.15, the apparent frequency of the oscillations was deduced as a function of time by measuring the zero crossing. Two sets of data are plotted since every other zero crossing corresponds roughly to one period of oscillation. The curve fit coincides with the average of the two. Figure 21.15c shows the resulting phase shift associated with the frequency change in Fig. 21.15. At about 40 ms after the control was turned...

PP bead foams of a range of densities were compressed using impact and creep loading in an Instron test machine. The stress-strain curves were analysed to determine the effective cell gas pressure as a function of time under load. Creep was controlled by the polymer linear viscoelastic response if the applied stress was low but, at stresses above the foam yield stress, the creep was more rapid until compressed cell gas took the majority of the load. Air was lost from the cells by diffusion through the cell faces, this creep mechanism being more rapid than in extruded foams, because of the small bead size and the open channels at the bead bonndaries. The foam permeability to air conld be related to the PP permeability and the foam density. 15 refs. 

Typical curves are shown in Fig. 22 a and b for current and potential steps respectively. For the short times (trate determining step is due to a concentration polarization [78], The variation of the transient current versus ]fi is linear, described satisfactorily by the classical Cottrel-type relation (see Fig. 23). After a certain time which depends on the experimental conditions, mainly the oxygen partial pressure in the surrounding atmosphere, a depolarization effect is observed the V (t) curve shows an overshoot while the I(t) curve shows a net enhancement of current. 

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