Proving termination of (conditional) rewrite systems

In this paper an important problem in the domain of term rewriting, the termination of (conditional) rewrite systems, is dealt with. We show that in many applications, well-founded orderings on terms which only make use of syntactic information of a rewrite systemR, do not suffice for proving termination ofR. Indeed sometimes semantic information is needed to orient a rewrite rule. Therefore we integrate a semantic interpretation of rewrite systems and terms into a well-founded ordering on terms: the notion ofsemantic ordering is the first main contribution of this paper. The use and usefulness of the semantic ordering in proving termination is illustrated by means of some realistic examples.Furthermore the concept of semantic information induces a novel approach for proving termination inconditional rewrite systems. The idea is to employ not only semantic information contained in the terms that are to be compared, but also extra (semantic) information contained in the premiss of the conditional equation in which the terms appear. This leads to our second contribution in the termination problem area: the notion ofcontextual ordering andcontextual semantic ordering. Thecontextual approach allows to prove termination of conditional rewrite systems where all classical partial orderings would fail.     

A short-chain dehydrogenase gene from Pichia stipitis having D-arabinitol dehydrogenase activity

An NAD⁺-dependent D-arabinitol dehydrogenase (polyol dehydrogenase) gene was isolated from Pichia stipitis CBS 6054 and cloned in Saccharomyces cerevisiae. The gene was isolated by screening of a λ-cDNA library with a zymogram technique. D -Arabinitol, xylitol, D -glucitol and galactitol are substrates for the recominant protein. With D -arabinitol as substrate the reaction product is D -ribulose. The molecular weight of the native tetramer enzyme is 110 000 Da and the monomer is 30 000 Da. The amino acid sequence is homologous to the short-chain dehydrogenase family. It is 85·5% identical to a D -arabinitol dehydrogenase from Candida albicans. The gene in P. stipitis was induced by D -arabinitol and P. stipitis was able to grow on D -arabinitol. The physiological role of D -rabinitol metabolism is discussed.     

LINEAR PROGRAMMING, SIMULATED ANNEALING AND TABU SEARCH HEURISTICS FOR LOTSIZING IN BOTTLENECK ASSEMBLY SYSTEMS

Multilevel lotsizing is one of the most challenging subjects in production planning, especially in the presence of capacity constraints. In this paper we investigate lotsizing heuristics for assembly production systems with a bottleneck. More specifically, we discuss heuristics based on Linear Programming (LP), and compare the performance of these heuristics with the performance of approaches based on simulated annealing and tabu search techniques.A comparison of the three heuristics on a set of test problems shows that simulated annealing and tabu search perform well compared to pure LP-based heuristics, but the effectiveness of the latter heuristics can be improved by combining them with elements from simulated annealing and tabu search.     

Amorphous microporous mixed oxides as selective redox catalysts

Amorphous microporous homogeneously mixed oxides based on Ti or V in silica can be prepared by an acid catalyzed solgel process. The materials have been characterized by TEM, UV, IR and sorption methods. The glasses can be used for the selective epoxidation of alkenes. The catalytic properties are comparable to those of the well known crystalline Ti-containing zeolites TS-1, Ti-MCM-41 and Ti-Beta. Amorphous microporous homogeneously mixed metal oxides seem to be promising new catalytic materials supplementing the well studied selective zeolites.     

Characterization of Vehicle-to-Vehicle Radio Channels from Measurements at 5.2 GHz

The development of efficient vehicle-to-vehicle (V2V) communications systems requires an understanding of the underlying propagation channels. In this paper, we present results on pathloss, power-delay profiles (PDPs), and delay-Doppler spectra from a high speed measurement campaign on a highway in Lund, Sweden. Measurements were performed at a carrier frequency of 5.2 GHz with the communicating vehicles traveling on the highway in opposite directions. A pathloss coefficient of 1.8 shows the best fit in the mean square sense with our measurement. The average root mean square (RMS) delay spread is between 263 ns and 376 ns, depending on the noise threshold. We investigate and describe selected paths in the delay-Doppler domain, where we observe Doppler shifts of more than 1,000 Hz.     

Weakest preconditions for progress

Predicate transformers that map the postcondition and all intermediate conditions of a command to a precondition are introduced. They can be used to specify certain progress properties of sequential programs.     

System-on-package: a broad perspective from system design to technology development

In this paper, we summarize and analyze main challenges towards system-on-package (SoP) integration with a broad perspective from system design to technology development. We see that the future SoP faces a main challenge of changed system architecture that will be different from today’s personal computer or PC-based systems. It is likely that communication-network based system architectures will be interesting to future SoP platforms. Second, we find that a major paradigm shift will occur in design methodology for SoP integration that emphasizes a coherent co-design of chip, package and system in a mixed signal environment and in combination with new issues such as virtual components integration. On the technology side, the major challenges will be power dissipation and system cooling, low-cost and thermal-matched high-density interconnect substrates, as well as low-cost passive components integration. Finally, we present some research examples that aim to cope with these new challenges on a strategic basis.     

Perceptual use of nonaccidental properties.

Reviews the literature about the nonaccidental properties (NAPs) cotermination, straightness, and parallelism to trace their historical roots, to list the properties that function as NAPs, and to discuss the psychological evidence for their detection and use. Four experiments are reviewed, and four are fully described that were designed to test the perceptual use of skewed symmetry, which results from orthographic projection of planar bilateral or mirror symmetry. Despite the large symmetry advantage obtained in all experiments, skewed symmetry is only perceived as bilateral symmetry-in-depth in cases of closed polygons or dot patterns with higher-order types of symmetry. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)