Policy conflict analysis for diffserv quality of service management

Policy-based management provides the ability to (re-)configure differentiated services networks so that desired Quality of Service (QoS) goals are achieved. This requires implementing network provisioning decisions, performing admission control, and adapting bandwidth allocation to emerging traffic demands. A policy-based approach facilitates flexibility and adaptability as policies can be dynamically changed without modifying the underlying implementation. However, inconsistencies may arise in the policy specification. In this paper we provide a comprehensive set of QoS policies for managing Differentiated Services (DiffServ) networks, and classify the possible conflicts that can arise between them. We demonstrate the use of Event Calculus and formal reasoning for the analysis of both static and dynamic conflicts in a semi-automated fashion. In addition, we present a conflict analysis tool that provides network administrators with a user-friendly environment for determining and resolving potential inconsistencies. The tool has been extensively tested with large numbers of policies over a range of conflict types.     

Sheeting of wheat flour dough

A combined experimental, analytical and numerical study of sheeting of wheat flour dough was performed. The material behaviour was defined using a non‐linear viscoelastic model calibrated with data obtained from uniaxial compression, loading–unloading and stress relaxation tests. Tests were performed using an instrumented small‐scale rolling rig. The roll speed and roll gap were varied to determine the effect on the steady‐state vertical force and exit thickness. Experiments were performed using one‐stand as well as a two‐stand roll set up. The analytical model which assumed perfect plasticity led to significantly lower forces than the experimental data. The numerical predictions were accurate at small reduction ratios. The exit thickness of the dough sheet was predicted accurately from the numerical model. For the two‐stand rolling, the numerical data were not accurate when a significant level of stress developed in the dough between the two roll stands.     

Viscoelastic properties of latex paint films in tension: Influence of the inorganic phase and surfactants

The tensile properties of latex coatings were investigated with a set of custom formulated artist-type paints at an age of 1 year. All films in the study contained a poly(methyl methacrylate-cobutyl acrylate) binder exhibiting a glass-transition at approximately 10 °C. The viscoelastic behaviour of the latex matrix is first highlighted through a series of experiments involving different strain histories and temperatures. Influence of the inorganic particle concentration and geometry is then illustrated using TiO₂ and calcined kaolin for the secondary phase. Experimental data from a wide range of conditions are summarised through master curves of secant modulus and failure strains using time–temperature superposition. The results indicate that the latex films behave in a rheologically simple manner and it is possible to predict the response outside of the experimental time-scale. An analysis by similar methods is also given for TiO₂ pigmented films with/without surfactant removed by immersion in water. Differential scanning calorimetry and atomic force microscopy were also used in conjunction with mechanical tests. The combined findings suggest that a fraction of surfactant migrates to the TiO₂ interface during film formation, where it interferes with adhesion of the acrylic matrix.     

Tensile properties of latex paint films with TiO2 pigment

The tensile properties of latex paint films containing TiO₂ pigment were studied with respect to temperature, strain-rate and moisture content. The purpose of performing these experiments was to assist museums in defining safe conditions for modern paintings held in collections. The glass transition temperature of latex paint binders is in close proximity to ambient temperature, resulting in high strain-rate dependence in typical exposure environments. Time dependence of modulus and failure strain is discussed in the context of time–temperature superposition, which was used to extend the experimental time scale. Nonlinear viscoelastic material models are also presented, which incorporate a Prony series with the Ogden or Neo-Hookean hyperelastic function for different TiO₂ concentrations.     

Effect of friction on uniaxial compression of bread dough

The mechanical and frictional properties of foods have received considerable attention in recent years as accurate material data are needed for the simulation of large scale processing operations as well as providing a basis for product quality and development. In this study, uniaxial compression tests were performed on bread flour/water dough. Cylindrical samples of various heights and diameters were tested under both lubricated and non lubricated conditions. The stress-strain data showed a dependency on sample dimensions when no lubricant was used due to surface friction effects. This dependency was eliminated when silicon oil of 500 centistokes viscosity was used as a lubricant and the true stress-strain data were obtained experimentally. A theoretical expression derived from an equilibrium analysis of a compressed disc under frictional conditions was used to determine the coefficient of friction and the true stress-strain curve from unlubricated data. The true stress-strain data were also determined by an empirical extrapolation procedure. Finally, an iterative numerical procedure based on Finite Element Analysis confirmed the calculated values for both the coefficient friction and the true stress-strain curve.     

The fracture energy of bimaterial interfaces

This article describes a framework applicable to the measurement and interpretation of the fracture energy of bimaterial interfaces. A major conclusion of this study is that the fracture energy, Γ_i, is not unique and usually exhibits values substantially larger than the thermodynamic “work of adhesion. ” The lack of uniqueness is related to mode mixity (shear/opening) effects experienced by interface cracks, as characterized by the phase angle of loading, ψ: typically, Γ_i, is found to increase as ψ increases. These trends are attributed to crack shielding caused by roughness of the interface fracture surface, to material nonlinearity,etc. The phase angle is, in turn, influenced by the choice of test specimen, resulting in values of Γ_i that differ between specimens in a manner attributed to the locus of Γ_i with ψ. Preliminary models that relate Γ_i to roughness, plasticity, segregation,etc., are described, leading to insights concerning microstructural aspects of “weaklrd and “strong” interfaces. This paper is based on a presentation made in the symposium “Interface Science and Engineering” presented during the 1988 World Materials Congress and the TMS Fall Meeting, Chicago, IL, September 26–29, 1988, under the auspices of the ASM-MSD Surfaces and Interfaces Committee and the TMS Electronic Device Materials Committee.     

A finite element analysis of fracture initiation in ductile/brittle periodically layered composites

A near-tip plane strain finite element analysis of a crack terminating at and normal to the interface in a laminate consisting of alternate brittle and ductile layers is conducted under mode-I loading. The studies are carried out for a system representing steel/alumina composite laminate. The Gurson constitutive model, which accounts for the ductile failure mechanisms of microvoid nucleation, growth and coalescence, is employed within the framework of small deformation plasticity theory. Evolution of plastic zone and damage in the ductile layer is monitored with increasing load. High plastic strain localization and microvoid damage accumulation are found to occur along the brittle/ductile interface at the crack-tip. Fracture initiation in the ductile phase is predicted and the conditions for crack renucleation in the brittle layer ahead of the crack are established for the system under consideration. Ductile fracture initiation has been found to occur before plasticity spreads in multiple ductile layers. Effects of material mismatch and yield strength on the plastic zone evolution are briefly discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Updated Taxonomy for the Network and Service Management Research Field

Network and service management is an established research field within the general area of computer networks. A few years ago, an initial taxonomy, organizing a comprehensive list of terms and topics, was established through interviews with experts from both industry and academia. This taxonomy has since been used to better partition standardization efforts, identify classes of managed objects and improve the assignment of reviewers to papers submitted in the field. Because the field of network and service management is rapidly evolving, a biyearly update of the taxonomy was proposed. In this paper, a large-scale questionnaire is presented which was answered by experts in the field, evaluating the relevance of each individual topic for the next five years. Missing topics, which are likely to become relevant over the next few years, are identified as well. Furthermore, an analysis is performed of the records of papers submitted to major conferences in the area. Based on the obtained results, an updated version of the taxonomy is proposed.     

Cracking and Damage in a Notched Unidirectional Fiber-Reinforced Brittle Matrix Composite

Results of four-point bend tests on notched beams of a laminated unidirectional fiber-reinforced glass matrix composite are presented. The failure sequence has been established through in situ examination. The dominant damage mode is a mixed-mode, split crack that runs parallel to the predominant fiber directions. The crack interacts with and crosses over imperfectly aligned fibers. The resulting bridging tractions are sufficient to cause the critical strain energy release rate to increase substantially as the crack extends. Several other damage modes are also observed. These include mode I (tensile) matrix cracks bridged by fibers, mode II (shear) cracks, and compressive damage at the loading points.     

The mechanical properties of model-compacted tablets

In this study, the compressive strength of tablets made with salt, starch and fat was investigated. The strength was found to increase with compaction pressure, up to a maximum value where further increase in the compaction pressure led to no increase in the strength. The maximum strength corresponded to the point where zero porosity was obtained during the compaction process. However, because of the elastic rebound of the tablets after ejection, the maximum strength corresponded to non-zero final tablet porosities which varied between the materials. For this reason, the use of the density occurring during the compaction process appeared to provide a more reliable comparison between the materials. A simple linear mixing rule did not hold in characterising the strength in the salt:starch:fat systems. However, two regimes were observed depending on the salt volume fraction. At low salt volume fractions, the effect of the salt was negligible. After a certain critical salt volume fraction, increasing the salt led to an increase in the strength. Finite element simulations based on X-ray microtomography images of the tablets suggested that in the first regime, the stresses due to the salt particles were localised but in the second regime, stress-bearing networks were formed between the salt particles.

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