SYNTHESIS OF CHEMICAL REACTION PATHS: ECONOMIC AND SPECIFICATION CONSTRAINTS

The synthesis of alternative reaction paths leading to a desired chemical has received increasing attention in the recent past. A procedure to develop new reaction schemes in a systematic manner was reviewed by the authors ( [ 1 -3] ). The algorithm presented in these earlier papers implied the generation of an infinite number of reaction paths. The thermodynamic feasibility is a preliminary screening which reduces the number of chemical production schemes. Further screening is necessary, taking into account considerations which are related to economics, processing, safety and so on. Some constraints related with role specification, gross added value and demand/supply requirements are analysed in this paper. Examples illustrate the application of the screening procedure, showing that the addition of a few constraints results in a dramatic decrease of alternative reaction paths.     

Dynamic response and safety assessment of a batch process on cooling breakdown

Cooling breakdown in highly exothermic reaction processes may lead to runaway. The sensitivity and the safety assessment of a batch process on cooling breakdown are studied. The dependence of the minimum cooling time and the maximum allowable time of cooling breakdown for safe operation on the process parameters is investigated.     

Lyapunov-based control for switched power converters

Beginning with fundamental properties such as passivity or incremental passivity of the network elements comprised by a switched power converter, the nominal open-loop operation of a broad class of such converters is shown to be stable in the large via a Lyapunov argument. The obtained Lyapunov function is then shown to be useful for designing globally stabilizing controls that include adaptive schemes for handling uncertain nominal parameters. Numerical simulations illustrate the application of this control approach in DC-DC converters     

MOVPE grown Ga/sub 0.6/In/sub 0.4/Sb photodiodes for 2.55 mu m detection

Photodiodes with a long-wavelength cutoff extending out of 2.9 mu m have been fabricated from MOVPE-grown Ga/sub 0.6/In/sub 0.4/Sb homojunctions. These mesa devices without any passivation or antireflecting coating exhibit a peak efficiency as high as 43% at 2.60 mu m.<>     

Relative neighborhood graphs and their relatives

Results of neighborhood graphs are surveyed. Properties, bounds on the size, algorithms, and variants of the neighborhood graphs are discussed. Numerous applications including computational morphology, spatial analysis, pattern classification, and databases for computer vision are described     

Large scale transmission network planning using optimization andheuristic techniques

Pursuing optimal solutions for large scale transmission network planning problems is a formidable task due to their combinatorial nature and also due to the nonconvexities involved. Successful approaches using hierarchical Benders decomposition incur in a high computational cost mainly due to the need to solve a large integer program (the investment sub-problem) for every Benders iteration. In this work the authors propose to use heuristics within the decomposition framework, therefore avoiding to solve to optimality each integer sub-problem. The global computational effort is substantially reduced, and allows coping with large problems that would be intractable using classical combinatorial techniques. Case studies with the 6 bus Garver test system and a reduced Southeastern Brazilian power network are presented and discussed     

Employment and alcohol: analysis of a clinical casuistic

The relationship between alcohol and work was studied in a group of 537 voluntary patients (393 male and 144 female) admitted to the department of Medicina del Lavoro, Pavia University for alcohol rehabilitation. The highest incidence of alcohol abuse was found in non-working subjects (pensioners, unemployed, housewives) although the start of excessive drinking takes place after beginning a working activity; a cause-effect relationship between these two factors can not be clearly determined, however. It is true that the stress provoked by this new condition (introduction to the work experience) can, in certain subjects, be a contributing factor in alcohol abuse. The increasingly lower age of initiation to alcohol reconfirms the need for prevention and instruction even at scholastic level. We can deduce how no working condition, low age and low education can constitute makers of risk for alcohol abuse.     

Thin layer activation of chromium with deuterons

In view of the recent increased interest in chromium based materials, the thin layer activation of chromium has been studied. This paper considers relative activity as a function of depth for the deuteron induced reaction in natural chromium. The presented results are based on calculations using computer codes and experimental verification using the stacked foil technique and electropolishing of activated bulk samples. A very good agreement of the various methods was obtained. It is shown that using 10 MeV deuterons, a reasonable homogeneous activation over 120 μm can be obtained.