Modeling and Testing Implementations of Protocols with Complex Messages

This paper presents a new language called APSL for formally describing protocols to facilitate automated testing. Many real world communication protocols exchange messages whose structures are not trivial, e.g. they may consist of multiple and nested fields, some could be optional, and some may have values that depend on other fields. To properly test implementations of such a protocol, it is not sufficient to only explore different orders of sending and receiving messages. We also need to investigate if the implementation indeed produces correctly formatted messages, and if it responds correctly when it receives different variations of every message type. APSL's main contribution is its sublanguage that is expressive enough to describe complex message formats, both text-based and binary. As an example, this paper also presents a case study where APSL is used to model and test a subset of Courier IMAP email server

Continuum damage mechanics: combining thermodynamics with a thoughtful characterization of the microstructure

We formulate a macroscopic description of the mechanics of damaged materials. To represent the microstructure, the distribution of crack sizes is captured by way of the Minkowski functionals, or so-called quermass integrals, while a second-rank tensor is used to describe the average orientation of the cracks. A two phase-type approach is adopted to distinguish elastically strained material from unstrained regions in the wake of the cracks. Using nonequilibrium thermodynamic techniques, the driving force for the growth of the microcracks is naturally identified. In particular, Griffith's law is generalized to assemblies of polydisperse crack sizes. Due to the detailed characterization of the microstructure, we are also able to account for the plastic zones at the rims of the cracks that are known to hamper the crack growth, and to discuss possible forms of the damage parameter. The presented approach separates in a transparent fashion the incorporation of fundamental thermodynamic and mechanic principles on one hand, from the specification of the material and details of the crack formation and growth on the other han

Melt-spun poly(tetrafluoroethylene) fibers

The recent discovery of melt-processable poly(tetrafluoroethylene) (PTFE) allows for common thermoplastic-polymer processing technologies to be applied to this unique polymer, which heretofore was considered to be highly intractable. In this paper, we report simple melt-spinning of monofilaments of a set of melt-processable (modified) PTFE grades with weight-average molar masses (M w) ranging from 77 to 292kg/mol. Fibers were spun at 380°C at draw-down ratios of up to 2,750, yielding filaments of linear densities as low as 0.8tex, corresponding to a diameter of ∼20μm. The maximum Young's modulus and tensile strength of as-spun fibers produced in this study were 91.7cN/tex (1,972MPa) and 12.0cN/tex (258MPa), respectively, accompanied by a strain to break of 24

A simple method for the determination of refractive indices of (rough) transparent solids

Simple methods for the determination of refractive indices of transparent polymers and inorganic and organic solids of irregular geometry or with scratched or corrugated surfaces are rare. A classical procedure is based on the invisibility of a body immersed in a liquid with the same refractive index as that of the body. In order to avoid the laborious procedure connected with the search for a liquid with matching refractive index and to find an approach which is independent of the observation by eye, we describe here a modified immersion method which allows the ready determination of the refractive index of solids. The present method is based on the interpolation of the maximum transmission (nTmax) of a solid immersed in liquids with different, typically non-matching, refractive indices. Illustrations with quartz glass, crown glass and poly(vinylidene fluoride) (PVDF) films showed that nTmax can be determined with a reproducibility of ± 0.003. By comparison with refractive indices determined by ellipsometry, it was concluded that the refractive index of a solid can be determined with the modified immersion method within an accuracy better than ± 0.01 when systematic errors resulting from the fit method are also taken into consideratio

Generation of Porous Particle Structures using the Void Expansion Method

The newly developed "void expansion method" allows for an efficient generation of porous packings of spherical particles over a wide range of volume fractions using the discrete element method. Particles are randomly placed under addition of much smaller "void-particles". Then, the void-particle radius is increased repeatedly, thereby rearranging the structural particles until formation of a dense particle packing. The structural particles' mean coordination number was used to characterize the evolving microstructures. At some void radius, a transition from an initially low to a higher mean coordination number is found, which was used to characterize the influence of the various simulation parameters. For structural and void-particle stiffnesses of the same order of magnitude, the transition is found at constant total volume fraction slightly below the random close packing limit. For decreasing void-particle stiffness the transition is shifted towards a smaller void-particle radius and becomes smoother.Comment: 9 pages, 8 figure

The transition from CCC to UCC with regard to royalties and license fees, and necessary consequences for the VAT-Directive

As the Union Customs Code will replace the Community Customs Code with effect from 1 May 2016, the thesis focuses on the new treatment of royalty payments for customs purposes and its legal consequences. In a first step, a comparison between the Community Customs Code and the Union Customs Code reveals that importers will have to face a significant increase in the customs liability of royalty payments. Secondly, with the European Union being a member of the World Trade Organization, it is investigated whether the topic-related provisions of the Union Customs Code comply with the provisions of the General Agreement on Tariffs and Trade. A survey of the advisory opinions and commentaries of the World Customs Organization indicates that the European customs law will follow the interpretation of the World Customs Organization to a great extent. Due to the fact that the taxable amount for import value added tax purposes corresponds with the customs value, the validity of this rule under the Union Customs Code is explored: an examination of the case law on the direct linkage between a supply and its consideration proves this rule as being justified. On the basis of these findings, then, the thesis discloses the considerable problem of double taxation of royalties and license fees in the case of taxable persons being exempt from the value added tax, as the royalty payment for the imported goods establishes a second taxable transaction, namely the supply of a service. Therefore, it is submitted to exclude the supply of services rendered in relation to the importation of goods from the taxable amount for import value added tax purposes

Constitutive modelling of polymer glasses : finite, nonlinear viscoelastic behaviour of polycarbonate

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The effect of size and density on the mean retention time of particles in the reticulorumen of cattle (Bos primigenius f. taurus), muskoxen (Ovibos moschatus) and moose (Alces alces)

Particle passage from the reticulorumen (RR) depends on particle density and size. Forage particle density and size are related and change over time in the RR. Particle density mainly influences sorting in the reticulum, whereas particle size influences particle retention in the fibre mat of stratified rumen contents (‘filter-bed' effect). We investigated these effects independently, by inserting plastic particles of different sizes (1, 10 and 20mm) and densities (1·03, 1·20 and 1·44mg/ml) in the RR of cattle (Bos primigenius f. taurus) as a pilot study, and of muskoxen (Ovibos moschatus; n 4) and moose (Alces alces; n 2) both fed two diets (browse and grass). Faeces were analysed for plastic residues for 13d after dosing to calculate mean retention times (MRT). The results confirmed previous findings of differences in absolute MRT between species. Comparing muskoxen with moose, there was no difference in the effect of particle density on the MRT between species but particle size had a more pronounced effect on the MRT in muskoxen than in moose. This indicated a stronger ‘filter-bed effect' in muskoxen, in accord with the reports of stratified RR contents in this species v. the absence of RR content stratification in moose. Low-density particles were retained longer in both species fed on grass diets, indicating a contribution of forage type to the ‘filter-bed effect'. The results indicate that retention based on particle size may differ between ruminant species, depending on the presence of a fibre mat in the RR, whereas the density-dependent mechanism of sedimentation in the RR is rather constant across specie

The Influence of the Degree of Heterogeneity on the Elastic Properties of Random Sphere Packings

The macroscopic mechanical properties of colloidal particle gels strongly depend on the local arrangement of the powder particles. Experiments have shown that more heterogeneous microstructures exhibit up to one order of magnitude higher elastic properties than their more homogeneous counterparts at equal volume fraction. In this paper, packings of spherical particles are used as model structures to computationally investigate the elastic properties of coagulated particle gels as a function of their degree of heterogeneity. The discrete element model comprises a linear elastic contact law, particle bonding and damping. The simulation parameters were calibrated using a homogeneous and a heterogeneous microstructure originating from earlier Brownian dynamics simulations. A systematic study of the elastic properties as a function of the degree of heterogeneity was performed using two sets of microstructures obtained from Brownian dynamics simulation and from the void expansion method. Both sets cover a broad and to a large extent overlapping range of degrees of heterogeneity. The simulations have shown that the elastic properties as a function of the degree of heterogeneity are independent of the structure generation algorithm and that the relation between the shear modulus and the degree of heterogeneity can be well described by a power law. This suggests the presence of a critical degree of heterogeneity and, therefore, a phase transition between a phase with finite and one with zero elastic properties.Comment: 8 pages, 6 figures; Granular Matter (published online: 11. February 2012