Control strategies for exothermic batch and fed-batch processes A sub-optimal strategy is developed which combines fast response with a chosen control signal safety margin. Design procedures are described and results compared with conventional control.

There is a considerable scope for improving the temperature control of exothermic processes. In this thesis, a sub-optimal control strategy is developed through utilizing the dynamic, simulation tool. This scheme is built around easily obtained knowledge of the system and still retains flexibility. It can be applied to both exothermic batch and fed-batch processes. It consists of servo and regulatory modes, where a Generalized Predictive Controller (GPC) was used to provide self-tuning facilities. The methods outlined allow for limited thermal runaway whilst keeping some spare cooling capacity to ensure that operation at constraints are not violated. A special feature of the method proposed is that switching temperatures and temperature profiles can be readily found from plant trials whilst the addition rate profile Is capable of fairly straightforward computation. The work shows that It is unnecessary to demand stability for the whole of the exothermic reaction cycle, permitting a small runaway has resulted in a fast temperature response within the given safety margin. The Idea was employed for an exothermic single Irreversible reaction and also to a set of complex reactions. Both are carried out in a vessel with a heating/cooling coil. Two constraints are Imposed; (1) limited heat transfer area, and (11) a maximum allowable reaction temperature Tmax. The non-minimum phase problem can be considered as one of the difficulties in managing exothermic fed-batch process when cold reactant Is added to vessel at the maximum operating temperature. The control system coped with this within limits, a not unexpected result. In all cases, the new strategy out-performed the conventional controller and produced smoother variations in the manipulated variable. The simulation results showed that batch to batch variations and disturbances In cooling were successfully handled. GPC worked well but can be susceptible to measurement noise.Higher Education Ministry and Scientific Researc

Effect of delivery mode on postpartum neonatal body temperatures

Objective: It is known that general and local anesthesia practices disrupt the delicate balance of thermoregulation center which is already sensitive to very tiny differences of temperatures in a normal subject. We aimed to evaluate and compare the rectal temperatures of newborns born with normal vaginal delivery and cesarean section.Methods: We performed a prospective study of 106 term newborn - 40 born with normal vaginal delivery (group 1) and 66 born with cesarean section [51 spinal anesthesia (group 2), 15 general anesthesia (group 3)]. Only term babies were included in the study. Babies of eclamptic, pre-eclamptic and diabetic mothers and babies with chronic systemic diseases were excluded. Pregnants who underwent elective cesarean section were included in the study. Adolescent pregnants, pregnants with increased risks and pregnants with complicated operations were excluded. Mothers' temperatures were measured before and after the interventions. Rectal temperatures of the babies were measured immediately after birth.Results: Environmental temperature was maintained at 22-24 degrees C. Pre-operative mother temperatures were 36.310.30 degrees C in group 1, 36.36 +/- 0.26 degrees C in group 2 and 36.39 +/- 0.19 degrees C in group 3 (p=0.414). Post-operative mother temperatures were 36.39 +/- 0.27 degrees C in group 1, 36.29 +/- 0.31 degrees C in group 2 and 36.25 +/- 0.28 degrees C in group 3 (p=0.215). Rectal temperatures of the babies born with normal vaginal delivery were significantly higher than the others. It was lowest in the general anesthesia group (37.5 +/- 0.6 degrees C, 37.2 +/- 0.2 degrees C and 36.8 +/- 0.4 degrees C in group 1, 2 and 3, respectively). The temperature differences between groups were statistically significant p<0.001).Conclusions: In conclusion, it is worthy to note that temperatures of the newborns can differ according to the delivery mode. Physicians and health professionals that take care of the newborns should be aware of this difference