Scaling of the viscoelasticity of highly filled carbon black polyethylene composites above the melting point

Different types of linear low-density polyethylene and ethylene butylacrylate copolymers were mixed with various types of carbon black in amounts between 25 and 40% by weight. Viscoelastic properties were measured using dynamic mechanical analysis applying a frequency sweep. Typically, the complex modulus approaches asymptotically a constant value at small frequencies, which is referred to as ‘yield modulus’. These results were analysed using a scaling approach according to which the complex modulus and the frequency are normalised by the yield modulus and the quotient of the yield modulus and the polymer viscosity, respectively. Thus a master curve is achieved for nearly all samples independent of the polymer and carbon black type and loading. A similar scaling behaviour has been observed earlier for differently concentrated suspensions of carbon black in Newtonian liquids, but not for filled polymers and different carbon blacks. Thus, contributions from polymer and carbon black to the compounds' viscoelastic properties are discussed.     

Evaluation of quarternary aggregate resources in Norway

The paper refers to some results of recent research in Norway on aggregate/concrete interaction. The objective has been to establish criteria for classification, based on knowledge of the geological origin of the aggregates. The evaluation system developed incorporates an automatic data processing information system and a new method of mineralogical quality classification of sand aggregates. The latter refers primarily to the properties of aggregates determining the water requirement and strength of concrete. The system has been used for evaluating a large number of Quaternary aggregate deposits throughout the country, and the results have been correlated with relevant concrete testing.     

Comparison of two CO2 removal options in combined cycle power plants

In this paper, two concepts of CO₂ removal in CC are compared from the performance point of view. The first concept has been proposed in the framework of the European Joule II programme and is based on a semi-closed gas turbine cycle using CO₂ as the working fluid and a combustion with pure oxygen generated in an air separation unit. This is a zero emission system as the excess CO₂ produced in the combustion process is totally captured without the need of costly and energy consuming devices. The second concept calls for a partial recirculation of the flue gas at the exit of the heat recovery boiler of a CC. The remaining flow is sent to a CO₂ scrubber. Ninety percent of the CO₂ is removed in an absorber/stripper device. The two systems are compared to a state-of-the-art CC when the most advanced technology is used, namely a 9FA type gas turbine and a three pressure level and heat recovery boiler. Our results show also that the CO₂ semi-closed CC cycle performances are not very dependent on the configuration of the heat recovery boiler and that the recirculated gas CC performances are only slightly sensitive to the recirculation ratio. A high value of this latter mainly gives a significant reduction of the size and hence of the cost of the CO₂ scrubber. From the performance point of view, the results show that the system efficiency with partial recirculation and a CO₂ scrubber is always higher by 2–3% points than the CO₂-based CC efficiency in comparable conditions.     

Shell structures in offshore platforms: design and application

The main structural aspects considering offshore steel platforms, steel decks, concrete platforms and other structural components involving shell elements are reviewed. Outlines are given with regard to design and strength analysis of the most important types of shell structures involved.     

SESAM-69—A general purpose finite element method program

The multilevel superelement method in combination with extensive data generators materialized in the program system SESAM-69 introduce a new dimension to the concept of the Finite Element Method (FEM).The paper describes the superelement method and the program system SESAM-69 in brief terms. However, the major part contains some of the program analytics in connection with this method. The multilevel superelement method is an extension of the better known substructure technique, or reduction procedure. The method applies to both statics and dynamics.     

Evaluation of Chinese projects and comparison with Norwegian projects

Project work in developing and emerging economies is complicated and unpredictable. It would be of great help to equip project managers with an easily applicable tool to assess whether the project is on the right track or not. A Project Evaluation Scheme (PEVS) has earlier been used on Norwegian projects. Data from 89 Chinese projects has been collected using the scheme. This article analyses the Chinese data and compares them to the Norwegian findings. The Chinese projects are scoring higher in all areas investigated, except on informal contacts. Particularly high were goal setting, overall planning and control execution. The Chinese projects achieve their goals and are regarded as a success by all participants. They should improve in project closeout work. The article discusses the reasons for differences between Chinese and Norwegian projects, ranging from differences in perception regarding the questionnaire, to the possibility that Chinese projects in fact are better. The qualities of activity execution are found to be the most important factor in predicting project success. PEVS is proven to be applicable to Chinese projects, yet further customisation is needed.     

Impedance modelling of air electrodes in alkaline media

A mathematical model of the impedance response of porous air electrodes in alkaline solutions, based on flooded agglomerate theory, was developed. The model results provides insight into characteristic features of the impedance spectra according to the relative rate of the various reactions and mass transfer processes occurring. The modelled spectra where dissolution, transport and reaction of oxygen dominates the impedance are close to ideal semicircles. With increasing contribution from ionic transport in the solution inside the pores, two distinct features occur, namely the appearance of a 45° branch at high frequencies, and an inductive loop at low frequenices. Examples from the literature where inductive loops occurs are given.     

Nonlinear robust constrained control of partially uncontrollable and open-loop unstable systems

In this paper we consider a bilinear matrix inequality (BMI) based method, which provides an ellipsoidal estimate of the region of attraction, for nonlinear constrained robust stabilization. Robustness against model uncertainty is handled. The method is based on an uncertain multi-model representation of the plant parameterized by affine local models and their respective supports in the state-space, and an associated piecewise affine state-feedback structure. We show that the method is applicable to uncertain constrained systems that are partially uncontrollable and open-loop unstable.