Unerwünschte Reaktionen organischer Stoffe als Gefahren in Chemieanlagen

Undesired reactions of organic substances as sources of danger in chemical plant . In chemical production processes, danger can arise both from the intended exothermal reaction and from unintended exothermal reactions. Such “undesired” reactions may be exothermal reactions of the substances themselves (e.g. decomposition, polymerization) or reactions of the substances involved with one another (e. g. of a reactant with the solvent). Differential thermal analysis and warm storage have been successfully used in various modifications as experimental methods for the study of such reactions. For exothermal decomposition reactions, correlations can be made between the chemical constitution of the substances and the energy released on decomposition, as well as the temperature of incipient decomposition. In mixtures with other substances a modified decomposition behaviour must be expected, usually of such a kind that the temperature range of decomposition is lowered. There are many possible exothermal reactions of substances with one another; only a few have hitherto been studied in detail.     

An effective heuristic for adaptive control of job sequences subject to variation in processing times

Variation in sequential task processing times is common in manufacturing systems. This type of disturbance challenges most scheduling methods since they cannot fundamentally change job sequences to adaptively control production performance as jobs enter the system because actual processing times, are not known in advance. Some research literature indicates that simple rules are more suitable than algorithmic scheduling methods for adaptive control. In this work, a ‘state space – average processing time’ (SS-APT) heuristic is proposed and compared to four most commonly used scheduling rules and two well-established heuristics based on Taillard’s benchmarks. It is shown that the adaptive control is made possible under variation in processing times given the flexibility and strong performance of the SS-APT heuristic, especially for work-in-process inventory control.     

Hyperwelcome

Web page annotation and adaptive navigation support are two active, but independent research directions focused on the same goal: expanding the functionality of the Web as a hypertext system. The goal of the AnnotatEd system presented in this paper has been to integrate annotation and adaptive navigation support into a single value-added service where the components can reinforce each other and create new unique attributes. This paper describes the implementation of AnnotatEd from early prototypes to the current version, which has been explored in several contexts. We summarize some lessons we learned during the development process and which defined the current functionality of the system. We also present the results of several classroom studies of the system. These results demonstrate the importance of the browsing-based information access supported by AnnotatEd and the value of both the annotation and navigation support functionalities offered by the system.     

Field Properties in Surface Irrigation Management and Design

Field properties—topography, hydraulic resistance, and infiltration—play an important role in the performance of surface irrigation systems, and appropriate characterizations of these are required as data input to simulation or design software. The EWRI/ASCE Task Committee on Soil and Crop Hydraulic Properties has been charged with preparing a guide for practitioners faced with such data entry. The result is this special section of the Journal of Irrigation and Drainage Engineering in which this paper is the first in the series presented. It describes the characteristics of these field properties and notes a series of caveats to be considered when dealing with them in the course of analyses or designs of surface irrigation systems.     

Modal transmission-line theory of three-dimensional periodic structures with arbitrary lattice configurations

The scattering of waves by multilayered periodic structures is formulated in three-dimensional space by using Fourier expansions for both the basic lattice and its associated reciprocal lattice. The fields in each layer are then expressed in terms of characteristic modes, and the complete solution is found rigorously by using a transmission-line representation to address the pertinent boundary-value problems. Such an approach can treat periodic arbitrary lattices containing arbitrarily shaped dielectric components, which may generally be absorbing and have biaxial properties along directions that are parallel or perpendicular to the layers. We illustrate the present approach by comparing our numerical results with data reported in the past for simple structures. In addition, we provide new results for more complex configurations, which include multiple periodic regions that contain absorbing uniaxial components with several possible canonic shapes and high dielectric constants.     

Reductive silylation and alkylation of phthalimides

Preparative electrochemical reduction of N-methylphthalimide in dry acetonitrile and in the presence of dimethylsulfate or trimethylchlorosilane lead to bis-lactams by dimerization at the carbonyl group. 1, 3-Bis-trimethylsilyloxy-2-methylisoindole is formed instead using a large excess of silylating agent. An analogous isoindole derivative is obtained from reduction of N-phenylphthalimide. A mechanism accounting for the formation of one or two electron products under different alkylating conditions is discussed.     

Robust discrete-time minimum-variance filtering

The bounded-variance filtered estimation of the state of an uncertain, linear, discrete-time system, with an unknown norm-bounded parameter matrix, is considered. An upper bound on the variance of the estimation error is found for all admissible systems, and estimators are derived that minimize the latter bound. We treat the finite-horizon, time-varying case and the infinite-time case, where the nominal system model is time invariant. In the special stationary case, where it is known that the uncertain system is time invariant, we provide a robust filter for all uncertainties that still keep the system asymptotically stable     

Crystal chemistry of γ-(Zn, Me)3(PO4)2 solid solutions

A number of γ-(Zn,$\text{Me}$)₃(PO₄)₂ solid solutions with the “γ-Zn₃(PO₄)₂” structure have been prepared and equilibrated at about 1070 K ($\text{Me}\text{= Mg, Mn, Fe, Co, Ni, Cu, and Cd}$). Approximate homogeneity ranges are given. The monoclinic unit cell dimensions have been accurately determined from Guinier-Hägg photographs. The structure contains five- and six-coordinated cations. Correlations between homogeneity ranges, unit cell dimensions, cation radii and cation distributions are pointed out, and the phases are also compared with isotypic (Mg,$\text{Me}$₃(PO₄)₂ and (Co,$\text{Me}$)₃(PO₄)₂ solid solutions.