Push-Pull Operation

Another way to maximize the overall performance of thermal sensors is the push-pull principle that is used in isothermal calorimetry. In that case, the heats flowing into and out of the reactor are exactly balanced, so that the temperature inside the 

Equation (3.3) shows the individual heats that contribute to overall heat gain and loss. The reaction heat, A//rxn, is positive for endothermic reactions and negative for exothermic reactions. The heat loss to the environment is shown as A/7iOSs- The heat supplied to the reactor, usually in the form of electric heating, is AHe but other forms of heating, for example, radiative, can be used instead of the electric heater. The baseline condition applies when no chemical reaction takes place. 

When the heat lost to the environment is exactly balanced by the heat supplied by the heater, (3.5) is obtained. 

V is voltage, I is current, and R is resistance. When a chemical reaction takes place and the temperature in the environment is constant, the thermal output of the chemical reaction is directly related to the electric heater output. 

---

These are the probes of choice in thermal chemical sensors because they are stable ( 0.05°C/year), inexpensive, sensitive, chemically inert, and small (Herwaarden and Meijer, 1994). Moreover, they can be directly heated and as such can be used for the push-pull operation. They are made of high-temperature-sintered oxides (e.g., BaO/SrO) covered with glass coating (Fig. 3.1). 

The amplifier network provides signal conversion and suitable static and dynamic compensation for good positioner performance. Control from this block usually reduces 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... 

The third step of the method consists of having supply chain directors identifying current and future states scores for their operations based on the definitions available in the maturity model which has 5 levels that were already described Level 1 - Basic Push Operation, Level 2 - Optimized Push Operation, Level 3 - Hybrid Push - Pull Operation, Level 4 - Advanced Pull Operation, Level 5 - Optimized Pull Operation. For instance, if the SC director, after reading the maturity model, believes that his operation is stiU in level 1 for current state, he should enter number one into the respective field of current state in the spreadsheet. 

When the desired future state in 1 year horizon is analyzed, Uruguay is the country that shows a strong objective to move closely to a hybrid Push-Pull operation (level 3). It can also be seen that USA operation has a clear focus to move from a basic Push operation (level 1) to an optimized Push operation Gevel 2), as illustrated in Fig. 7.6. 

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... 

Fig. 8. Example of a Push-Pull osmotic pump where (a) represents the pump before operation, and (b), during operation.

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

The regiochemistry observed in the EGA-catalyzed displacement of methoxyl group with nucleophiles is promising For example, the carbenium ion formed from compound 29 in methanolic solution is trapped to produce the thermodynamically stable compound 30. However, in CHjClj, a concerted push-pull mechanism ( push by nucleophile and pull by EGA) is operative leading to the exclusive formation of 31. 1-Menthone 32 can be acetalized by EGA catalysis without epimerization at C-2... 

Thus, the sensitivity of a thermistor is a quadratic function of operating temperature. The optimum sensitivity is typically 4% °C 1. Because of their nonlinear response, thermistors are sometimes linearized by placing a resistor of similar nominal value in parallel with the thermistor, with a resulting loss of sensitivity. This is not generally necessary for thermochemical sensors, particularly for the push-pull applications, because the temperature range involved is small. For direct temperature measurement, the detection limit of 10 4oC can be achieved with a conventional Wheatstone bridge. 

Using the equivalency relationships in Table 3.1, propose an equivalent electrical circuit diagram for an enzyme thermistor operated (a) in direct detection mode and (b) in the feedback, push-pull mode. 

Fig. 17. A Electrode configuration and B operating configuration used for push-pull poling...

A backpack sprayer is similar to a push-pull sprayer, except that it is a self-contained unit (tank and pump) and is carried on the operator s back. A mechanical agitator plate may be attached to the pump plunger. Capacity of these sprayers is usually less than five gallons. Figure 8.7 shows a pest control worker using a backpack sprayer in a greenhouse. 

These sprayers involve a double-action hydraulic pump which is operated with a push-pull motion. The pesticide is sucked into the cylinder and pushed... 

---