Prediction of solubility for HFC working fluids in model substances for compressor oils

This study is a first step towards the prediction of the behaviour of working fluids and compressor oils. Different thermodynamic models are investigated and a modified Flory-Huggins-based predictive model, termed MFH, is proposed for solubility of HFCs in long-chained hydrocarbons. From experimental data, 7 general parameters have been fitted for the MFH model to describe 14 binary systems. The UNIQUAC model demands 28 specific parameters without the possibility of extending their validity to other mixtures. A predictive UNIFAC model requires 8 general parameters, but its uncertainty, 17%. is poor compared to the MFH model's 7%.     

Swelling and mechanical properties of cellulose hydrogels. II. The relation between the degree of swelling and the creep compliance

The mechanical properties of swollen cellulose hydrogels have been studied. The degree of swelling of the gels was varied between 0.75 and 6.3 g water/g dry gel (g/g) by partial drying followed by reswelling in water. Creep rate was measured in uniaxial compression in the time interval 15–900 s for gels in equilibrium with water. Isochronous relations between stress and reversible strain were found to be linear, and creep compliance was calculated from the slopes. Both the creep compliance and the creep rate increase with an increased degree of swelling. General observations, such as the high strain limit of linearity in the stress–strain curves and the magnitude of the creep compliance, indicate similarities between swollen cellulose gels and rubbery networks. It is therefore assumed that the statistical theories for swollen networks can describe the amorphous matrix of the gels. In order to obtain creep compliance values representative of the amorphous matrix, the experimental values were corrected for the presence of crystalline regions. It is also suggested that non-load-bearing microvoids are present at high swelling levels. According to calculations based on the theory, the network chains of the amorphous regions in a gel swollen to 2.4 g/g contain about 11 monomer units and the Flory-Huggins interaction parameter χ equals 0.2.     

Colloidal Processing of a Very Fine BaTiO3 Powder—Effect of Particle Interactions on the Suspension Properties, Consolidation, and Sintering Behavior

The relation between the suspension state and the rheological properties, the consolidation, and packing of a very fine (nanosized) BaTiO₃ powder has been investigated. The BaTiO₃ powder was suspended in a nonaqueous medium by adsorbing fatty acids and a polymeric dispersant, poly(12-hydroxy stearic acid), (PHS), at the BaTiO₃/decane interface. Calculated interparticle energies imply that the suspension with PHS adsorbed is colloidally stable, while the suspensions with oleic and octanoic acid can be characterized as weakly and strongly flocculated, respectively. Analysis of settling experiments and rheological measurements at high concentrations confirmed these characteristics. Pressure filtration resulted in nearly identical green body densities in spite of the differences in colloidal properties, but the preliminary sintering experiments and microstructural characterization showed that the strongly flocculated suspension displays a significantly retarded sinterability compared to the colloidally stable and the weakly flocculated suspensions. The absence of a correlation between green density and sintering behavior was explained by considering both the volume taken by the adsorbed fatty acids and the PHS polymer—which can be substantial for nanosized powders—and the state of the suspension. While a decrease in the thickness of adsorbed surfactant or polymer layer will enable a higher particle packing density, such a thin adsorbed layer results in a more strongly flocculated suspension which will resist dense packing. Hence, it is suggested that the green bodies of the colloidally stable and the weakly flocculated suspensions correspond to a relatively homogeneous, but loosely packed, green body microstructure. The strongly flocculated suspension results in a green body with a more inhomogeneous microstructure.     

The solubility of HCFC22, CFC114 and HFC152A in n-hexadecane

The solubilities of chlorodifluoromethane (HCFC22), 1, 2-dichlorotetrafluoroethane (CFC114) and 1,1-difluoroethane (HFC 152a) in n-hexadecane have been measured at temperatures between 303. 15 and 343. IS K and Henry's constants have been derived. The measurements were made with two different methods, a GLC method and an isochoric method. In general the results of the methods differ less than their combined margin of error, which is estimated to be less than 5% for the GLC method and less than 2% for the isochoric method.     

ON THE LAGRANGE MULTIPLIER TEST FOR AUTOREGRESSIVE MOVING-AVERAGE MODELS

Abstract. This paper examines the score or Lagrange multiplier statistic for testing the adequacy of a fitted autoregressive moving-average model and gives a simple closed-form expression for this test statistic. Some singularities arising as the order of the alternative model is increased are examined.     

Mechanism for performance of energetically modified cement versus corresponding blended cement

The microstructure of cement paste of 50/50 mixes of cement/quartz and cement/fly ash, both ground in a special mill [energetically modified cement (EMC) process] and simply blended, have been studied under sealed curing conditions. The grinding process reduced the size of both cement grains and quartz/fly ash markedly and created flaky agglomerates of high inner surface for the finer particles. EMCs had much higher degree of hydration at 1 day, but similar as blends at 28 days. The pores were much finer for EMC paste due to smaller particles as also reflected in the strength. The morphology of calcium hydroxide in EMC paste appeared more mass like. Pozzolanic reaction was insignificant for quartz in EMC, but increased for fly ash. Thus, improved performance of EMC versus OPC can be explained by increased early hydration and extensive pore size refinement of the hardened binder resulting in reduced permeability and diffusivity for concrete.     

Initiation of fractures in rigid PVC pipes by soft particles

Rigid PVC pipes prepared from a particle-free, tin-stabilized formulation were subjected to constant internal pressure tests (16 MPa, 60°C), originally in order to study the scattering in time-to-failure of pipes free from crack-initiating particles. Although many efforts were made to produce pipes free from all possible foreign particles, most failures were initiated by particles. The particles in this case were soft and rubbery, Particles of this kind have previously never been found in any of the several hundred fracture surfaces in lead-stabilized PVC pipes containing calcium carbonate studied in this laboratory. The possible origin of the soft particles is discussed. The results suggest that soft particles represent serious flaws. Besides a full-grown (penetrating) crack, some of the pipes also contained growing, particle-induced cracks. In these cases the penetrating crack always contained the largest particle. The presence of growing cracks in fractured pipes indicates the crack propagation rate in rigid PVC to be rather low at the test temperature and stress level used. Fracture surface morphology and creep thinning of the pipe wall at the point of fracture most likely were strongly affected by physical aging during the test period.     

Bark consumption by voles in relation to mineral contents

Recent field experiments with impregnated wooden sticks have demonstrated a pronounced use by small rodents of mineral supplies, especially sodium, and such findings seemed related to vole damage to forestry seedlings. Consumption of the bark of experimentally introduced aspen twigs and of sodium-impregnated sticks by voles (mainly or onlyMicrotus agrestis) correlated significantly on clear-cuts but not on unmanipulated abandoned fields. Such a correlation appeared when abandoned fields were cut continuously in summer. At vole peak densities, bark of pine seedlings experimentally fertilized with sodium was consumed but not bark of seedlings fertilized with calcium or control seedlings. Field pine seedlings attacked by voles had significantly higher levels of calcium, sodium, and phosphorus than the nearest untouched seedling. However, sodium and phosphorus contents correlated strongly. Sodium and calcium supply to voles in laboratory feeding trials did not diminish the moderate interest in pine bark. Such conditions are, however, assumed to mimic a situation of bark sampling in low-density populations. Sodium, and possibly also calcium, requirements are concluded to be partial determinants of the destructive bark consumption by voles at the peaks of their multiannual population cycles.     

Static consistency checking of web applications with WebDSL

Modern web application development frameworks provide web application developers with high-level abstractions to improve their productivity. However, their support for static verification of applications is limited. Inconsistencies in an application are often not detected statically, but appear as errors at run-time. The reports about these errors are often obscure and hard to trace back to the source of the inconsistency. A major part of this inadequate consistency checking can be traced back to the lack of linguistic integration of these frameworks. Parts of an application are defined with separate domain-specific languages, which are not checked for consistency with the rest of the application. Examples include regular expressions, query languages and XML-based languages for definition of user interfaces. We give an overview and analysis of typical problems arising in development with frameworks for web application development, with Ruby on Rails, Lift and Seam as representatives.To remedy these problems, in this paper, we argue that domain-specific languages should be designed from the ground up with static verification and cross-aspect consistency checking in mind, providing linguistic integration of domain-specific sub-languages. We show how this approach is applied in the design of WebDSL, a domain-specific language for web applications, by examining how its compiler detects inconsistencies not caught by web frameworks, providing accurate and clear error messages. Furthermore, we show how this consistency analysis can be expressed with a declarative rule-based approach using the Stratego transformation language.     

Allocation mechanisms in public provision of transport and communication infrastructure

This study explores the allocation mechanisms in the public provision of interregional transport and communication infrastructure in Sweden. The logistics of the flow of infrastructure investments from the government budget is examined. The purpose is to consider how the demand for infrastructure investment is estimated by public agencies, how judgments are made on governmental expenditure policy, and what determines the spatial distribution of infrastructure investment. The analysis is carried out along four main lines; demand for infrastructure services, political intentions and goals, the modal composition of investments for transport and communication, and the spatial distribution of infrastructure. The discussion considers functional, spatial, and temporal consistency aspects in the public provision of infrastructure.