Monitoring the limiting reactant concentration is a key question to maximize the productivity and to guarantee the safety of exothermic fed-batch processes. However in most applications, the concentration cannot be measured in real-time since suitable devices do not exist or are too expensive; the concentrations are then measured by off-line analyses. In this context monitoring the concentrations via software sensors, or state observer based estimators, is an attractive option. The presence of model uncertainties is a major limitation when applying state observers to real processes. More precisely, in fed-batch exothermic reactors the bad knowledge of both the reaction kinetics and the heat transfer may prevent the use of classical observers. In this study, we propose two different approaches to estimate the concentration of the limiting reactant in a class of single phase exothermic fed-batch reactors with uncertain kinetics and heat transfer. The first approach is based on a finite time converging observer that provides an estimate for the reaction rate via the reactor energy balance equation. The concentration is then computed from the reaction rate estimate via a material balance equation. The main contribution of this approach is the use of a finite time observer to limit the reconstruction error by guaranteeing a small convergence time interval for the reaction rate estimate. The second approach is based on an interval observer that provides two bounds for the concentration by considering uncertainties related to both the heat transfer and the reaction kinetics. The final estimate is then computed as the mean of the bounds. A systematic tuning procedure has been developed for each of both estimation techniques. Both estimators have then been tested and validated with real data coming from the production of different kinds of resins carried out in 10 tons reactors.

During military operations, a small fraction of propellant mass is not consumed during firing and is deposited onto the ground surface. Soluble propellant constituents can be released from particulate residues into the environment. The release of uncombusted propellant residues and transformation products results in soil, surface water, and ultimately groundwater contamination. It is important to study the potential for off-site migration of munitions and to provide qualitative data that helps better understand transit of these propellant constituents. Propellant constituents of interest for this study were nitroglycerine (NG), 2,4-dinitrotoluine (2,4-DNT), 2,6-dinitrotoluine (2,6-DNT), and nitroguanidine (NQ). The goal of this work is to determine fate and transport parameters, partition/distribution coefficients and transformation rates for these compounds in three soils that represent a range of geographic locations and soil properties. This supports a companion study that looks at dissolution of constituents from fired and unfired solid propellant formulations and their transport in soil.

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International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Boeing's Test Data Retrieval System not only acts as an interface between the Airborne Data Acquisition System and a mainframe computer but also does batch mode processing of data at faster than real time. Analysis engineers request time intervals and measurements of interest. Time intervals and measurements requested are acquired from the flight tape, converted to first order engineering units, and output to 3480 data cartridge tape for post processing. This allows all test data to be stored and only the data of interest to be processed at any given time.

Many strains of Gram-negative bacteria, such as Pseudomonas, are able to utilize a variety of unusual chemicals, including a wide range or aromatic hydrocarbons and their derivatives for growth. Bacteria with the potential to degrade sodium benzoate were isolated, identified and grown as biofilms on sodium benzoate in a laboratory-scale fluidized bed biofilm bioreactor. Four Pseudomonas strains identified as P. aeruginosa (BDS2) P. putida (BDS1 and GR1) and Burkholderia cepecia (GR3FAR) were used in a laboratory-scale FBBR together with two Bacillus strains - Bacillus macroides (SBSY4) and Bacillus simplex (MAR). Sodium benzoate biodegradation capacities of these species were compared under batch and continuous operations. Biofilm and planktonic bacterial growth dynamics were monitored by plate counts, and optical density measurements (230nm) determined benzoate biodegradation. Overall, higher attached and planktonic bacterial counts were determined under batch compared to continuous mode. In addition to this, the ability of attached cells to use sodium benzoate as their sole carbon source was compared to their suspended counterparts in a batch system. There were more attached counts compared to suspended cells and attached cells apparently degraded sodium benzoate better than planktonic cells. Similarly, higher rates of benzoate depletion were found to occur under batch compared to the continuous system. It thus appeared that more cell growth implied more substrate consumption. SEM showed attached cells and microcolonies of all the isolates on GAC, indicating their biofilmforming abilities.

N-linked glycosylation often imparts important properties to protein therapeutics. An essential step in this intracellular process is the transfer of oligosaccharide from dolichol monophosphate (Dol-P) to a potential glycosylation site. Variability in the success rate of this reaction affects the extent of protein glycosylation. The critical role of Dol-P suggests that its availability may influence the extent of glycosylation by limiting the pool of lipid-linked oligosaccharides (LLOs), the glycosyl donor. To test this hypothesis, the impact of Dol-P supplementation on protein glycosylation in Chinese hamster ovary (CHO) cells was investigated. Although exogenous Dol-P was incorporated by CHO cells and processed into LLOs in a dose-dependent manner, Dol-P supplementation had no marked effects on LLO or overall cellular glycosylation levels. While concentrations of exogenous Dol-P exceeding 100 µg/ml were detrimental to CHO cell viability, maximum non-toxic supplemental doses of Dol-P had no significant impact on the glycosylation of recombinant interferon-γ produced by batch cultures of CHO cells. These results show that glycosylation in CHO cells cannot be readily enhanced by Dol-P feeding under normal culture conditions. / Singapore-MIT Alliance (SMA)

This research explores how near-future information can be used to strategically control a batch processor in a serial-batch processor system setting. Specifically, improved control is attempted by using the upstream serial processor to provide near-future arrival information to the batch processor and further meet the re-sequencing requests to shorten critical products? arrival times to the batch processor. The objective of the research is to reduce mean cycle time and mean tardiness of the products being processed by the serial-batch processor system. This research first examines how mean cycle time performance of the batch processor can be improved by an upstream re-sequencing approach. A control strategy is developed by combining a look-ahead control approach with an upstream re-sequencing approach and is then compared with benchmark strategies through simulation. The experimental results indicate that the new control strategy effectively improves mean cycle time performance of the serial-batch processor system, especially when the number of product types is large and batch processor traffic intensity is low or medium. These conditions are often observed in typical semiconductor manufacturing environments. Next, the use of near-future information and an upstream re-sequencing approach is investigated for improving the mean tardiness performance of the serial-batch processor system. Two control strategies are devised and compared with the benchmark strategies through simulation. The experimental results show that the proposed control strategies improve the mean tardiness performance of the serial-batch processor system. Finally, the look-ahead control approaches that focus on mean cycle time and mean tardiness performances of the serial-batch processor system are embedded under a new control strategy that focuses on both performance measures simultaneously. It is demonstrated that look-ahead batching can be effectively used as a tool for controlling batch processors when multiple performance measures exist.

Controlling crystal size distribution (CSD) is important to downstream processing and to product quality. It is well-recognized that selective removal functions can be used to influence CSD, for example by manufacturing a product with a larger dominant size or narrower distribution. Early work on the use of feedback control to manipulate the residence time distribution functions of fines in a continuous crystallizer demonstrated the utility of such an approach in handling process upsets and cycling that resulted from system instability. These efforts were extended to batch crystallization, although there remained significant difficulty associated with on-line analysis of the size distribution. The development of new technologies, such as Focused Beam Reflectance Measurement (FBRM), provides a methodology for on-line monitoring of a representation of the crystal population in either batch or continuous crystallization systems. The FBRM technology is based on laser light scattering; properly installed, it allows on-line determination of the chord length distribution (CLD), which is statistically related to the CSD and depends on the geometry of the crystal. The purpose of the present study is to use the FBRM to monitor the evolution of CSD characteristics and to implement a feedback control scheme that provides the flexibility to move the CSD in a preferred direction. Cooling batch crystallizations of paracetamol has been chosen to investigate implementation of the control scheme. The work will show how fines removal and varying cooling rates provide reliable and practical control of crystal size distribution.