Restricted recourse strategies for bounding the expected network recourse function

This paper presents bounds for the expected recourse function for stochastic programs with network recourse. Cyclic recourse, a concept introduced by Wallace [18], allows the approximation of the recourse problem by restricting the optimal flows on a set of cycles and by augmenting the original network to induce separability. We introduce a new procedure that uses again a set of cycles but does not approximate the problem; instead it solves it heuristically without altering the original network or requiring separability. The method produces tighter bounds and is computationally feasible for large networks. Numerical experiments with selected networks illustrate the effectiveness of the approach.     

Mechanism of electrodimerization of retinal and cinnamaldehyde

Electrochemical reduction of either cinnamaldehyde or retinal in acetonitrile containing 0.5 M. TBAP and water or phenol leads to a mixture of dimeric products. However, electroreduction of either of these aldehydes in the presence of the carbon acid, diethyl malonate, leads to increased yield of pinacol formation. The mechanism of these electrodimerization reactions has been discerned using cyclic voltammetry-variations in peak potential as a function of scan rate, proton donor concentration and concentration of aldehyde have been compared to published diagnostic criteria. Retinal and cinnamaldehyde form dimeric products in a radical-radical coupling pathway. The major mechanistic feature that correlates with product distribution is the association (solvation) of oxygen acids, phenol and water with the radical anion. In contrast, diethyl malonate reacts with the radical anion of either cinnamaldehyde or retinal by a direct proton transfer.     

Characterization and optimization of HPIC for on-line preconcentration of trace metals with detection by ICP-mass spectrometry

The objective of this study was to investigate the feasibility of using a commercially available cation-exchange column for trace metal preconcentration. In addition, the advantages of interfacing the column to a highly sensitive element-selective detector were examined. A high-performance ion-chromatograph (HPIC) with a high-pressure pump and valve system was used to aid loading and delivery of the mobile phase. An inductively coupled plasma mass spectrometer combination (ICP-MS) was used as a detection device, with interfacing by means of a small diameter liquid-transport tube. The performance of the HPIC/ICP-MS combination was optimized by varying the concentration and flow-rate of two eluents (nitric acid and hydrochloric acid). The effects of varying the sample pH were assessed and the column capacity was determined by "breakthrough" tests. The elements copper, cadmium, mercury and lead were studied; the detection capability was dependent upon the sample volume loaded onto the column. The accuracy of the method was assessed by analysis of an "in house" reference standard.     

Incident-energy dependence of 3p electron energy-loss spectra of nickel

The intensities of two features in the 3p electron energy-loss spectrum of nickel, a dip prior to the threshold and a satellite ～ 12 eV above the threshold, are observed to systematically decrease as the incident electron energy is lowered from 1000 to 150 eV. These intensity changes indicate a dependence of the matrix elements for each excitation on momentum transfer as the incident energy is decreased, in part through changes in the strength of Fano interference near threshold.     

A Comparison of Potential Applications of Expert Systems and Decision Support Systems

This paper describes ways in which decision support systems (DSS) and expert systems (ES) may be differentiated. It proposes a simplified systemic view which emphasises the functional differences of the environments within which each type of system is applied, thereby avoiding some of the problems often associated with attempting to define DSS and ES according to their constituent parts. This functional emphasis allows DSS and ES to be placed within a useful existing theoretical framework which takes account of contextual influences. The results of two independent surveys of DSS and ES applications in a sample domain-accountancy-are used to assess the view of their functionality held by users of the systems, particularly their functional differences. Some conclusions are drawn about the role of the user in the construction of such systems.     

Temperature dependence of the local mode in the vibronic spectrum of SrTiO3:Cr3+

The local vibrational mode exhibited by chromium impurity ions in strontium titanate has been investigated using vibronic spectroscopy. The temperature dependent characteristics of the mode are attributed to anharmonic interactions with lattice phonons. Line broadening contributions are made by both a decomposition mechanism and inelastic phonon scattering. Elastic phonon scattering processes can explain the line shift while multiphonon emission causes the integrated intensity to decrease. The results are compared with previous local mode investigations made on alkali halides by i.r. absorption spectroscopy.     

Reactions involving fluoride ion. Part 24 [1]. Syntheses from perfluorocyclobutene

Passage of perfluorocyclobutene, in a flow system, over caesium fluoride at 590–600^o provides a synthesis of hexa- fluoro-2-butyne in high yield. In a similar process, using glass tubes, tricyclo[3.3.0.0^2,6]octane and bicyclo[2.2.1] -2-heptene were obtained.     

Geometrical effects in the measurements of mechanical properties in parallel superposed flows

The shear-dependent complex viscosity η^*₁₂, which governs the linear time-dependent stresses in a viscoelastic fluid undergoing infinitesimal shearing oscillations in-line with a viscometric motion, has been investigated. Formulas relating η^*₁₂ to measured quantities have been derived for the cone-and-plate and parallel-plate geometries. In the former case, the formula has the same form as that found when there is no steady shearing present. For the parallel-plate geometry, the formula is different because of the radial variation in the viscometric shear rate. In order to determine the empirical significance of this formula, η^*₁₂ data were obtained for two fluids, NBS nonlinear sample No. 1 and a 4.3 g/dl aqueous polyethylene oxide (molecular weight, 5 X 10⁶) solution using a Weissenberg rheogoniometer Model R-18. Data were acquired and analyzed using a minicomputer on-line with the rheogoniometer. The obtained data indicate that good agreement between the η^*₁₂ measured using the two geometries is obtained only if the derived formulas are used. Also, it is shown that theoretical results of simple-fluid theory are valid for these data.     

The differential correction algorithm for generalized rational functions

The differential correction algorithm for generalized rational functions is described, and two theorems on convergence and order of convergence are given. An example shows that the order of convergence may deteriorate from superlinear to linear when a best generalized rational approximation does not exist.