Folk Theorems on the Correspondence between State-Based and Event-Based Systems

Kripke Structures and Labelled Transition Systems are the two most prominent semantic models used in concurrency theory. Both models are commonly believed to be equi-expressive. One can find many ad-hoc embeddings of one of these models into the other. We build upon the seminal work of De Nicola and Vaandrager that firmly established the correspondence between stuttering equivalence in Kripke Structures and divergence-sensitive branching bisimulation in Labelled Transition Systems. We show that their embeddings can also be used for a range of other equivalences of interest, such as strong bisimilarity, simulation equivalence, and trace equivalence. Furthermore, we extend the results by De Nicola and Vaandrager by showing that there are additional translations that allow one to use minimisation techniques in one semantic domain to obtain minimal representatives in the other semantic domain for these equivalences.Comment: Full version of SOFSEM 2011 pape

Modelling the effects of waste components on cement hydration

Ordinary Portland Cement (OPC) is often used for the Solidification/Stabilization (S/S) of waste containing heavy metals and salts. These waste componenents will precipitate in the form of insoluble compounds onto unreacted cement clinker grains preventing further hydration. In this study the long term effects of the presence of contaminants in solidified waste is examined by numerically simulating cement hydration after precipitation of metal salts on the surface of cement grains. A cement hydration model was extended in order to describe porewater composition and the effects of coating. Calculations were made and the strength development predicted by the model was found to agree qualitatively with experimental results found in literature. The complete model is useful in predicting the strength and leaching resistance of solidified products and developing solidification recipes based on cement

Monotonicity and error bounds for networks of Erlang loss queues

Networks of Erlang loss queues naturally arise when modelling finite communication systems without delays, among which, most notably\ud (i) classical circuit switch telephone networks (loss networks) and\ud (ii) present-day wireless mobile networks.\ud \ud Performance measures of interest such as loss probabilities or throughputs can be obtained from the steady state distribution. However, while this steady state distribution has a closed product form expression in the first case (loss networks), it has not in the second case due to blocked (and lost) handovers. Product form approximations are therefore suggested. These approximations are obtained by a combined modification of both the state space (by a hyper cubic expansion) and the transition rates (by extra redial rates). It will be shown that these product form approximations lead to\ud \ud - secure upper bounds for loss probabilities and\ud - analytic error bounds for the accuracy of the approximation for various performance measures.\ud \ud The proofs of these results rely upon both monotonicity results and an analytic error bound method as based on Markov reward theory. This combination and its technicalities are of interest by themselves. The technical conditions are worked out and verified for two specific applications:\ud \ud - pure loss networks as under (i)\ud - GSM-networks with fixed channel allocation as under (ii).\ud \ud The results are of practical interest for computational simplifications and, particularly, to guarantee blocking probabilities not to exceed a given threshold such as for network dimensioning.\u

Tasks, cognitive agents, and KB-DSS in workflow and process management

The purpose of this paper is to propose a nonparametric interest rate term structure model and investigate its implications on term structure dynamics and prices of interest rate derivative securities. The nonparametric spot interest rate process is estimated from the observed short-term interest rates following a robust estimation procedure and the market price of interest rate risk is estimated as implied from the historical term structure data. That is, instead of imposing a priori restrictions on the model, data are allowed to speak for themselves, and at the same time the model retains a parsimonious structure and the computational tractability. The model is implemented using historical Canadian interest rate term structure data. The parametric models with closed form solutions for bond and bond option prices, namely the Vasicek (1977) and CIR (1985) models, are also estimated for comparison purpose. The empirical results not only provide strong evidence that the traditional spot interest rate models and market prices of interest rate risk are severely misspecified but also suggest that different model specifications have significant impact on term structure dynamics and prices of interest rate derivative securities.

Stimulating The Use Of Secondary Materials In The Construction Industry: The Role Of Certification\ud

Introduction of secondary materials in the construction industry is quite difficult and has not always been successful, even when they satisfy all necessary product demands and environmental (leaching) conditions. Besides the financial and commercial aspects the main problem is convincing the user or customer that the secondary material is a safe and reliable alternative for primary materials. The best way to deal with this problem is by certification of the secondary material. Optimal results can be expected when authorities and both suppliers and users of the new type of material closely collaborate. This can be achieved by mutual consulting in regard to technical aspects and their demands concerning the product. Collaboration between suppliers enables joint investments in order to obtain certification and to enhance the knowledge about their product. This collaboration will also stimulate the consideration that the supplier is a good and reliable trading partner for the use

Blends of polyamide-6 with acrylic core-shell impact modifiers

Blends of polyamide-6 (PA6) and acrylic core-shell impact modifiers (CSIM) were made by an extruder process as well as a reactor process. On the extruder blends, the impact behaviour was studied as a function of temperature while changing the type of CSIM, the CSIM concentration (0¿40%) and the blending conditions. Reactor blends were prepared from caprolactam/CSIM mixtures via a hydrolytic polymerization process initiated either with water or with aminocapronic acid. The aminocapronic acid-initiated process is faster. The influence of reaction conditions on the deagglomeration of the CSIM, the melt flow index and the impact behaviour of the blends were studied. The degree of grafting of PA6 on the CSIM and the melt rheological behaviour of some samples have been investigated. The CSIM agglomerates were found to be broken up in the caprolactam starting mixture and did not coalesce to bigger particles. With the reactor blend method, often highly viscous melts were obtained. This is probably due to the formation of a comb-like structure of CSIM chains dissolved in caprolactam to which PA6 chains had been grafted

Nylon 4,I: an amorphous polyamide

The melt polymerization of nylon 4, I was studied, starting with nylon-salt and nylon prepolymers (ηinh=0.25). With nylon-salt only low molecular polymers were obtained, while with prepolymers the inherent viscosity could be raised to 0.77 (3h, 270°, vac.). The cyclization of tetra methylene diamine to pyrrolidine seem to be the major disturbing factor. The polymer is glassy and could easily be melt pressed. The torsion modulus of the material at 20°C was high (1.8 109 Pa) and remained high to near its Tg (138°C)

Transient handover blocking probabilities in road covering cellular mobile networks

This paper investigates handover and fresh call blocking probabilities for subscribers moving along a road in a traffic jam passing through consecutive cells of a wireless network. It is observed and theoretically motivated that the handover blocking probabilities show a sharp peak in the initial part of a traffic jam roughly at the moment when the traffic jam starts covering a new cell. The theoretical motivation relates handover blocking probabilities to blocking probabilities in the M/D/C/C queue with time-varying arrival rates. We provide a numerically efficient recursion for these blocking probabilities. \u

Tasks, cognitive agents, and KB-DSS in workflow and process management

The purpose of this paper is to propose a nonparametric interest rate term structure model and investigate its implications on term structure dynamics and prices of interest rate derivative securities. The nonparametric spot interest rate process is estimated from the observed short-term interest rates following a robust estimation procedure and the market price of interest rate risk is estimated as implied from the historical term structure data. That is, instead of imposing a priori restrictions on the model, data are allowed to speak for themselves, and at the same time the model retains a parsimonious structure and the computational tractability. The model is implemented using historical Canadian interest rate term structure data. The parametric models with closed form solutions for bond and bond option prices, namely the Vasicek (1977) and CIR (1985) models, are also estimated for comparison purpose. The empirical results not only provide strong evidence that the traditional spot interest rate models and market prices of interest rate risk are severely misspecified but also suggest that different model specifications have significant impact on term structure dynamics and prices of interest rate derivative securities.

Segmented copolymers with polyesteramide units of uniform length: structure analysis

Segmented poly(ether esteramide) copolymers with short (M = 382) partially aromatic esteramide units of uniform length and segments of poly(tetramethylene oxide) (PTMO) have beem synthesized in the melt. The polymers show phase separation into two or three phases. The influence of the PTMO segment length on the following properties was studied: the Tg of the amorphous phase, the Tm of the crystalline PTMO and the melting and crystallization behaviour of the uniform polyesteramide units. Volume fraction and density of each phase were determined. The polyesteramide units crystallize in lamellar structures; their sizes were studied using WAXD and SAXS. The polymers were melt processed and their mechanical properties were investigated using dynamic mechanical thermal analysis (d.m.t.a.) and tensile tests. Polyesteramide crystallinity, crystalline structure and crystallite size were found to be almost independent of PTMO segment length. The decrease in hard-segment melting temperature with increasing PTMO segment length is explained as being due to a `solvent¿ effect of the soft phase. The copolymers crystallize very fast, and the modulus in the rubber region is essentially independent of temperature. The copolymers with long PTMO segments (M = 2000 and 2900) have a low glass transition temperature (¿65°C); the materials are very soft and have an elongation at break of over 1000%. The copolymer with the shortest PTMO segments (M = 250) has a glass transition temperature of 43°C and the material is hard at room temperature