Computing partial expectations from tables

Many applications in inventory control, reliability engineering and preventive maintenance involve frequent calculations of probabilities and partial expectations. In the design of high-volume computer-based applications recourse to internal tables may therefore be preferable to an import of statistical packages. While interpolation in tabulated cdf’s will often prove sufficiently accurate from the point of view of statistical representation of the underlying problem, tables of compatible (partial) expectations need to be constructed with regard to the method of interpolation employed. The mathematics for establishing such tables differ from standard textbook procedures. This paper develops appropriate expressions in general terms and gives explicit results for the Gamma family of distributions, which is of particular interest in the areas of application mentioned.     

Tracking River Plumes with Volatile Halocarbon Contaminants: The Niagara River—Lake Ontario Example

The concentrations of six predominant volatile halocarbon contaminants CCl₄, total and industrial CHCl₃, CHBrCl₂, CH₂Cl₂, CFCl₃, and C₂Cl₄ in epi- and hypolimnetic lake waters are used to demonstrate tributary plumes and nearshore currents on the Lake Ontario/Niagara River example. The relative speed and sensitivity of the analysis for volatile halocarbons provides for a synoptic view of the major currents at the time of sampling. For example, the individual distributions of several contaminants indicate the existence of a Niagara River surface water plume in northerly direction for approximately 8 km into the lake. In contrast, the predominantly east-west isostats of the contaminant concentrations in the hypolimnetic water indicate little direct influence by the Niagara River and show the existence of other contaminant sources in these areas.     

Sicherung chemischer Produktionsanlagen mit Mitteln der Elektro-/Meß-, Steuerungs- und Regelungstechnik

Safeguarding of chemical production plant by means of control engineering . Control equipment is becoming increasingly important for safeguarding of plant. According to VDI/VDE 2180, sheet 3, control equipment is classified as operational equipment, as monitoring equipment, or as protective equipment. Operational and monitoring control equipment serves the proper operation of plant in its correct state or in a faulty but still acceptable state. Protective control equipment is intended to prevent occurrence of an unacceptable faulty state of the plant. It is helpful if the control equipment is classified at an early stage of planning. Preferably the protective control equipment should be considered separately from the other control equipment. It is then possible to design it in such a way that its behaviour in the event of faults can be clearly defined. A distinction is made between active faults (or functiontriggering faults) and passive faults (or function-inhibiting or blocking faults). An active fault reduces the availability of chemical plant for production by inadvertent shut-down. Passive faults of protective equipment prevent triggering of the protective function, even though the conditions for triggering are fulfilled. They adversely affect the safety of the plant. Passive faults of control equipment must therefore by prevented or kept under control. A selection of appropriate measures for achieving this is presented.     

Karbonatisierungszellen – Ein Beitrag zur Korrosion von Stahl in karbonatisiertem Beton

Carbonation cells – On the corrosion of steel in carbonated concrete Corrosion of steel in carbonated concrete involves the activity of active-passive galvanic couples (carbonation cells). Carbonation cells consisting of mortar electrodes in wet condition and subjected to wet-dry cycles have been investigated by means of current and potential measurements. The corrosion current can be explained in terms of oxygen diffusion through the mortar cover. The stationary current gives realistic values for the diffusion coefficient of oxygen in concrete. Changes from wet to dry and vice versa always increase the corrosion rate. Electrolytically and gravimetrically determined weight loss are in good agreement only for constant moisture conditions. In case of wetdry cycles oxidation and reduction reactions within the corrosion products are assumed to contribute to the total corrosion loss.     

A New Allenic Fatty Acid in Phlomis (Lamiaceae) Seed Oil

A new allenic fatty acid, phlomic acid, 7,8-eicosadienoic acid or 20:2Δ7,8allene, has been observed in several genera of the Lamiaceae, subfamily Lamioideae. The occurrence of this fatty acid seems to be correlated with the presence of an unusual 20:1 acid, 20:1Δ9cis or 20:1n–11. Phlomic acid is apparently produced by chain-elongation of the major seed oil fatty acid, laballenic acid or 18:2Δ5,6allene.     

A learning fedforward control strategy for the concentration control of recycle reactors. Part I: Set-point control

Unknown reaction rates make concentration control in laboratory recycle reactors a difficult task, particularly when gas chromatographs or other analytical equipment with long analysis times from part of the control system. For such time-delay systems, a model-based feedforward control technique is developed which uses some kind of learning linear mapping to provide estimates of the reaction rates. Regarding the number of time steps necessary to satisfy a new set point, in a variety of simulation studies, this technique has proven superior to similar but simpler control strategies.