Double-loop-iterative-tracking-algorithm-based direct coordination for hierarchical steady-state control of interconnected systems

An alternative hierarchical optimization algorithm obtained by combining a double-loop iterative strategy with an efficient coordination task is proposed. The new algorithm derived from the tracking method (Sidaoui et al. 1989, 1991) is applicable to non-convex problems and has the advantage of giving a better rate of convergence. Simulation results are given and compared with the original algorithm, indicating the superiority of the new approach for the example considered.     

THE INFLUENCE OF THE INDUCTION MOTOR VELOCITY ON THE TRANSIENT PHENOMENA

ABSTRACT

The paper deals with transient phenomena of an induction motor caused by a voltage pulse at different angular velocities. The response of the machine varies according to the angular velocity. The dependence of the time constants on the angular velocity has been derived. The response can be an exponential one or aperiodically damped. The reasons why the electromagnetic transient phenomenon of an asynchronous motor at standstill lasts longer than while revolving are explained. Per Unit System and space vectors are used.     

MEASUREMENT AND COMPUTATION OF PHYSICO-CHEMICAL PROPERTIES OF SUGAR SOLUTIONS

At the Department of Chemistry and Technology of Saccharides, Institute of Chemical Technology in Prague, we study technically important physical properties of sugar solutions. This paper deals with some results of measurement and correlation of boiling point elevation and density.

The present system of tables or nomograms of physical properties of sugar solutions is not satisfactory for automated data processing. In a critical analysis of the existing material it appears that physico-chemical data for sugar solutions were often compiled over ranges of variables which were interesting for laboratory control and not for engineering computations. That all calls for purposeful completion of data in the regions where they are lacking. Additionally, it calls for revision of tabulated values from the literature and for transformation of the tabulated data to functional relationships in order to make computation equations both precise and simple     

Recent Trends in the Search for New Extractants

Abstract

Since the introduction of solvent extraction as a separation method for metals, such solvating and acidic extractants have predominantly been used which are mono- or bifunctional compounds. They are able to form a five- or six-membered chelate ring, binding metal ions typically through one or two oxygen atoms, or through oxygen and nitrogen atoms. They can exhibit very useful selectivity, which is dependent on the localization of binding sites in various functional groups (acidic or neutral), chains or heterocyclic rings. However, a new approach in the search of new extractants is needed, if unusual selectivities are to be attained, e.g. within groups of chemically similar elements. Development of radius sensitive compounds represents one of the recent trends. The selectivity of macrocyclic ethers, mixed-heteroatom macrocyclic compounds and calixarenes is discussed in this review, with some emphasis laid on potential separation within groups of alkali and alkaline earth metals. Potential separation of lanthanides and actinides is also discussed, but less attention is paid to transition metals which can be separated by conventional extractants. Variables influencing the sensitivity are molecular configurations of the extractants nature of anions participating in the formation of extracted complexes, presence of mineral acids in the aqueous phase, nature of diluent and temperature. To separate elements with very similar ionic radii, extractants with less common, “soft” donor atoms can be applied. The separation of transplutonides (III) from lanthanides (III) is taken as an example, and the separation potential of acidic sulfur donor as well as neutral nitrogen donor extractants is discussed.     

Alternative Approach in Optimization of Plate Type Heat Exchangers

Plate type heat exchangers are widely used in process industries for gas/gas applications. Typically, these exchangers prove to be very efficient, especially as air preheaters in process furnaces or in equipment used in environmental protection (e.g., in units for thermal disposal of wastes).

For economic reasons, there is a need for a new optimization approach for plate type heat exchanger design and operation. The objective function is to achieve a minimal total annual cost of heat exchangers. Pressure drop and heat transfer are interdependent, and both of them strongly influence capital and operating costs of any heat transfer system. In designing a heat exchanger, it is necessary to determine the optimal dimensions of the apparatus with the given conditions of the equipment operation.

The goal is to obtain the most economically optimal design. An economic assessment allows a comparable estimation of various alternatives. The total annual cost consisting of fixed and variable costs of the heat exchanger was selected as a criterion that summarizes different factors of influence into one objective function. Major cost components of a heat exchange system are as follows: capital, operating and maintenance costs of air and flue gas fans, and capital and maintenance costs of the plate type heat exchanger.

The application of the developed optimization approach is demonstrated through practical industrial examples.     

INACTIVATION OF FICIN PROTEOLYTIC ACTIVITY IN THE PRESENCE OF ASCORBIC ACID AND Cu2+-IONS

The simultaneous presence of ascorbic acid, Cu²⁺ions and oxygen causes irreversible ficin inactivation. The degree of inactivation is dependent on the concentration of inhibitors. Relatively higher decrease of ficin proteolytic activity was found with high molecular substrate, hide powder azure, than with a low molecular one, N-benzoyl-L-arginine-p-nitroanilide. Gel chromatography on Sephadex G-50 showed that ficin inactivation is not due to the destruction of its molecule resulting in the decrease of its molecular weight. Inactivation of ficin proteolytic activity was associated with a partial drop in ficin immunoreactivity.