An experiment with affirm and HDM

Comparing the usefulness of methodologies for software development can be especially difficult when the services offered are based on different philosophies. Two systems, Affirm and HDM, were compared for their application to operation system security analysis. The assessment technique was to specify and analyze for security flaws on both systems a miniature example of a security kernel. The specification languages are at the opposite poles of the range from algebraic axioms to transition specifications. The types of security properties that could be verified with the tools available were access policy invariants and information flows. One theorem prover was highly interactive and the other nearly automatic. We found that the example could be specified satisfactorily and recognizably on both systems with a comparable amount of effort. The security analyses, on the other hand, led to very different verification tasks and different results. The two results were complementary rather than contradictory, and some additional experimentation, guided by theoretical suspicions, showed the exact relationship between them.     

A UNIFIED APPROACH TO THE STUDY OF SUMS, PRODUCTS, TIME-AGGREGATION AND OTHER FUNCTIONS OF ARMA PROCESSES

Abstract. Conditions under which sums, products and time-aggregation of ARMA processes follow ARMA models are derived from a single theorem. This characterizes these processes in terms of difference equations satisfied by their autocovariance function. From this we obtain necessary and sufficient conditions for a function of a Gaussian ARMA process and the product of two possibly dependent Gaussian ARMA processes to be ARMA. We show that the sum and product of two ARMA processes related by a Box and Jenkins transfer function model belong to the ARMA family.     

Correct: A simulated text editor

This paper describes a project to write a simulator for the native mode text editor of one computer, which could be run on a different computer. This was done to give a user of both computers a common editing language. The method of design and construction is presented together with brief details of the syntax and semantics of the editing language.     

Initial activation of platinum-rhodium gauzes for the catalytic oxidation of ammonia

Studies have been made of the activation of platinum-rhodium gauze catalysts for the oxidation of ammonia, using optical microscopy, electron probe microanalysis (EPMA), and electron spectroscopy to characterize the surfaces. The initial washing procedure is found to remove calcium and to reduce carbon residues on the surface, as a result of which the catalyst is active at lower temperatures. Subsequent activation in a hydrogen flame or in oxygen causes surface rearrangements and results in rhodium enrichment at the surface: this latter trend is partially reversed in the early stages of the oxidation of ammonia. Water vapor is found to deactivate the activated gauze.     

Analysis of SO2 oxidation in non-isothermal catalyst pellets using the dusty-gas model

Analysis of the experimental rate data [13] for SO₂ oxidation on a commercial V₂O₅ catalyst has yielded a model that describes the experimental data well while the rate constant follows the Arrhenius law. This model was subsequently used to adequately predict experimentally determined effectiveness factors using the dusty-gas model flux relations and a single value for the tortuosity factor. The latter analysis validates the excellent properties of the dusty-gas model to properly describe transport in complex systems.     

Transient diffusion and reaction in solids immersed in poorly-stirred fluids—II: Numerical aspects

A general computational strategy for the use of the formal solutions obtained in Part I of this paper is presented, and the numerical implementation of this strategy is described in detail for the right circular cylinder. Certain subtleties of the computational procedure are emphasized in order to facilitate similar numerical work for other geometries. Detailed numerical results are presented for a range of physically interesting but previously inaccessible parameter values. Limiting cases of our solution are shown to be in good agreement with the results of simpler analyses.The numerical solutions demonstrate that our techniques combine the classical advantages of eigenfunction expansions with good convergence properties at zero time and minimal computational overhead. In addition, our method is seen to be most efficient in those regimes where other theoretical treatments are unavailable. They thus provide computational and conceptual advantages over competing methods.     

广州市西江引水工程穿越北江大堤工程的结构设计

本文介绍了西江引水工程穿越北江大堤工程的结构设计和确保北江大堤安全的工程措施。该设计可供实际工程应用参考。