Views on the Subject of Multilevel Control

The title of my talk suggests that my remarks be more philosophical than technical, more general and broad brush than detailed and specialized. I will, nevertheless, take the liberty of somewhat limiting the scope in order to focus very specifically on some problems related to the application of multilevel concepts and techniques to control of complex industrial systems. In the control of industrial systems, we consider the overall goal to be, in a very general sense, the efficient utilization of resources (e.g. material, energy, environmental, labor, capital) in the production of products satisfying quality specifications and consistent with goals and constraints which may be imposed by society. Thus, we are concerned with the broad spectrum of decision-making and control functions (e.g. process control, operations control, scheduling, planning, etc.) which play a role in the effective operation of the system with respect to its production goals. The control problem in this generalized context is extremely difficult to handle; we formulate various multilevel/multilayer, hierarchical structures to provide rational and systematic procedures for resolving the problem

Systems Control of Chemical and Related Process Systems

The traditional concept of control, in application to chemical and related process systems (CRS), concerns the problem of how to manipulate inputs to the system so that (a) designated output variables follow predetermined time trajectories (which may be constants over finite intervals) or (b) the state vector of the system is transferred (optimally) from some initial value to a specified final value. However, there has been an increasing tendency to consider control from a broader and more general perspective. Strong contributing factors in this trend are (a) the increasing application of computers in process control, providing the hardware and software means for implementing more sophisticated control concepts, and (b) the growing awareness and acceptance of a "systems approach" in the design and control of industrial process systems

Preliminary Draft Report: State-of-the-Art Review of Integrated Systems Control in the Steel Industry

This is a preliminary draft version of the report to be issued on the "State-of-the-Art of Integrated Systems Control in the Steel Industry". The draft is incomplete and not necessarily in final form. Its purpose is to provide background material for the IIASA Conference on "Integrated Systems Control in the Steel Industry" scheduled for 30 June to 2 July, 1975. A second purpose is to motivate feedbacks concerning omissions and additions generated by respondents and Conference participants which may be incorporated into the final 'report

On the Determination of an On-Demand Policy for a Multilayer Control System

The cost-performance tradeoff problem associated with a multilayer control system for controlling a class of static, nonlinear, multivariable systems is considered. The multilayer control system has a number of layers of control functions each of which updates different subsets of the manipulated variables at different costs. A favorable cost-performance tradeoff is achieved by determining at each control decision time which subset of the control variables is to be updated. In this paper, we present a mathematical model which describes the operation of the multilayer control system. Also we show that the problem of determining a decision rule (policy) which results in an optimal cost-performance tradeoff can be formulated as a problem in Markovian Decision Processes. Consequently, an optimal policy can be identified by solving a linear program. In order to reduce the computational effort required for identifying the optimal policy, a class of parameterized policies is introduced based on a measure of deviation of the disturbance. This approach provides a designer with a practical method of determining a control policy which achieves a favorable cost-performance tradeoff. An example is given for demonstrating a possible application to process control

The Development of a Regional Industrial Complex

One possible direction of further IIASA research among other possibilities (e.g. optimum utilization of natural resources of the world, international sharing of the resources of the open sea, energy options etc.) should have a certain concentration of IIASA research on the theme of this paper. This theme includes the possibility of bringing IIASA research into closer contact with "clients" (international organizations, national organizations and authorities) to strengthen the applied part of IIASA research, and to continue the conceptual generalized research work on this basis. In selecting this theme, we had to ask: (a) What contributions can IIASA bring to bear on the problem that would not merely repeat what has already been done or is being done? (b) What are IIASA's peculiar strengths (present and potential) in this regard? (c) What are IIASA's limitations

Integrated Systems Control in the Steel Industry. State-of-the-Art Review and Proceedings of the Conference June 30-July 2, 1975

Integrated systems control has as its goal the integration of the information processing, decision-making and control functions of an industrial system to achieve increased operating efficiency and productivity, better utilization of resources, improved product quality and other benefits. As the steel industry is well advanced, relative to other industries, in the application of highly computerized systems integration, it was selected as the basis for a first case study. The Review presents both the results of a state-of-the-art survey of integrated systems control in the steel industry and the proceedings of a IIASA conference on the subject. The results motivate a general methodology for integrated control system design based on a hierarchical structuring of the system, incorporating multilevel decomposition and temporal and functional multilayer concepts

PCR Based Microbial Monitor for Analysis of Recycled Water Aboard the ISSA: Issues and Prospects

The monitoring of spacecraft life support systems for the presence of health threatening microorganisms is paramount for crew well being and successful completion of missions. Development of technology to monitor spacecraft recycled water based on detection and identification of the genetic material of contaminating microorganisms and viruses would be a substantial improvement over current NASA plans to monitor recycled water samples that call for the use of conventional microbiology techniques which are slow, insensitive, and labor intensive. The union of the molecular biology techniques of DNA probe hybridization and polymerase chain reaction (PCR) offers a powerful method for the detection, identification, and quantification of microorganisms and viruses. This technology is theoretically capable of assaying samples in as little as two hours with specificity and sensitivity unmatched by any other method. A major advance in probe-hybridization/PCR has come about in a technology called TaqMan(TM), which was invented by Perkin Elmer. Instrumentation using TaqMan concepts is evolving towards devices that could meet NASA's needs of size, low power use, and simplicity of operation. The chemistry and molecular biology needed to utilize these probe-hybridization/PCR instruments must evolve in parallel with the hardware. The following issues of chemistry and biology must be addressed in developing a monitor: Early in the development of a PCR-based microbial monitor it will be necessary to decide how many and which organisms does the system need the capacity to detect. We propose a set of 17 different tests that would detect groups of bacteria and fungus, as well as specific eukaryotic parasites and viruses; In order to use the great sensitivity of PCR it will be necessary to concentrate water samples using filtration. If a lower limit of detection of 1 microorganism per 100 ml is required then the microbes in a 100 ml sample must be concentrated into a volume that can be added to a PCR assay; There are not likely to be contaminants in ISSA recycled water that would inhibit PCR resulting in false-negative results; The TaqMan PCR product detection system is the most promising method for developing a rapid, highly automated gene-based microbial monitoring system. The method is inherently quantitative. NASA and other government agencies have invested in other technologies that, although potentially could lead to revolutionary advances, are not likely to mature in the next 5 years into working systems; PCR-based methods cannot distinguish between DNA or RNA of a viable microorganism and that of a non-viable organism. This may or may not be an important issue with reclaimed water on the ISSA. The recycling system probably damages the capacity of the genetic material of any bacteria or viruses killed during processing to serve as a template in a PCR desinged to amplify a large segment of DNA (less than 650 base pairs). If necessary, vital dye staining could be used in addition to PCR, to enumerate the viable cells in a water sample; The quality control methods have been developed to insure that PCR's are working properly, and that reactions are not contaminated with PCR carryover products which could lead to the generation of false-positive results; and The sequences of the small rRNA subunit gene for a large number of microorganisms are known, and they consititue the best database for rational development of the oligonucleotide reagents that give PCR its great specificity. From those gene sequences, sets of oligonucleotide primers for PCR and Taqman detection that could be used in a NASA microbial monitor were constructed using computer based methods. In addition to space utilization, a microbial monitior will have tremendous terrestrial applications. Analysis of patient samples for microbial pathogens, testing industrial effluent for biofouling bacteria, and detection biological warfare agents on the battlefield are but a few of the diverse potential uses for this technology. Once fully developed, gene-based microbial monitors will become the fundamental tool in every lab that tests for microbial contaminants, and serve as a powerful weapon in mankind's war with the germ world

Theory of Deep Impurity Levels in Cucl

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Concentration Dependence of Superconductivity and Order-Disorder Transition in the Hexagonal Rubidium Tungsten Bronze RbxWO3. Interfacial and bulk properties

We revisited the problem of the stability of the superconducting state in RbxWO3 and identified the main causes of the contradictory data previously published. We have shown that the ordering of the Rb vacancies in the nonstoichiometric compounds have a major detrimental effect on the superconducting temperature Tc.The order-disorder transition is first order only near x = 0.25, where it cannot be quenched effectively and Tc is reduced below 1K. We found that the high Tc's which were sometimes deduced from resistivity measurements, and attributed to compounds with .25 < x < .30, are to be ascribed to interfacial superconductivity which generates spectacular non-linear effects. We also clarified the effect of acid etching and set more precisely the low-rubidium-content boundary of the hexagonal phase.This work makes clear that Tc would increase continuously (from 2 K to 5.5 K) as we approach this boundary (x = 0.20), if no ordering would take place - as its is approximately the case in CsxWO3. This behaviour is reminiscent of the tetragonal tungsten bronze NaxWO3 and asks the same question : what mechanism is responsible for this large increase of Tc despite the considerable associated reduction of the electron density of state ? By reviewing the other available data on these bronzes we conclude that the theoretical models which are able to answer this question are probably those where the instability of the lattice plays a major role and, particularly, the model which call upon local structural excitations (LSE), associated with the missing alkali atoms.Comment: To be published in Physical Review