Screw optimization of a co-rotating twin-screw extruder for a binary immiscible blend

The effect of the screw configuration of a closely intermeshing co-rotating twin-screw extruder on residence time and mixing efficiency was studied for an uncompatibilized immiscible PA6/PP (80:20) bend. Alternative screw configurations were investigated systematically. The residence time distribution (RTD) was found to be a poor indicator of the total mixing efficiency, whereas the mixing intensity function yielded considerably better information. High shear stress, sufficient residence time, and high fill ratio in the melting section of the screw were the most important factors in achieving good dispersion of the minor phase. The evolution of morphology along the screw axis depended strongly on the screw configuration. The downstream flow characteristics after the screw end determined the final morphology of the blend.     

Use of epoxy reactivity for compatibilization of PP/PBT and PP/LCP blends

Binary blends of a reactive ethylene-based terpolymer with polybutylene terephthalate (PBT) and with a liquid crystalline polyester (LCP) were studied to clarify the possible interactions between the blended polymers. The aim was to determine the suitability of the reactive terpolymer containing epoxy reactivity as a compatibilizer in blends of polypropylene (PP) and these two polyesters. The binary blends exhibited increased viscosity during blending, changes in the crystallization of the PBT phase, and an intimate contact between the blended polymers, which pointed to strong interactions or chemical reactions between the compatibilizer and both PBT and LCP. FTIR analysis confirmed the reaction of the epoxide and formation of new esters. Most probably the carboxyl end groups of the polyesters reacted with the epoxy group of the compatibilizer. In the second part of the work the same terpolymer was shown to act as a compatibilizer in PP/PBT and PP/LCP blends. This behavior was based on good mixing with the PP phase and on the chemical reactivity or strong interactions with the polyesters demonstrated in the investigations on binary blends. Addition of 5 wt% of the compatibilizer improved the impact strength, especially in PP/PBT blends where synergistic behavior was found at compositions of 80/20 and 20/80. In PP/LCP blends, the compatibilizer significantly improved the impact strength of unnotched samples at 20 wt % LCP content. In both blends, the compatibilizer reduced the size of the dispersed domains and caused them to attach better in the matrix. © 1995 John Wiley & Sons, Inc.     

Plasma and lipoprotein lipid peroxidation in humans on sunflower and rapessed oil diets

The effects of natural mixed diets on lipid peroxidation were investigated in humans. In the first study, 59 subjects were fed a rapeseed oil-based diet rich in monounsaturated fatty acids (MUFA) and a sunflower oil-based diet rich in polyunsaturated fatty acids (PUFA) in a cross-over manner for three and a half weeks. The lipid peroxidation products in plasma were determined by measuring conjugated dienes and malondialdehyde (MDA). In a second study, plasma thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides, and the susceptibility of very low density lipoprotein + low-density lipoprotein (LDL) toin vitro oxidation were measured from subjects fed similar MUFA and PUFA diets for six week diets. No significant differences in plasma MDA or conjugated diene concentrations were found after the rapeseed oil diet or the sunflower oil diet in Study 1. In the second study, a small but significant decrease (P<0.05) in both lipid hydroperoxides and TBARS was observed in the LDL fraction after the sunflower oil diet. Thein vitro oxidation gave opposite results, showing increased oxidation after the sunflower oil diet. Despite a high intake of α-tocopherol during the oil peroids, no increase in plasma α-tocopherol was noticed in either study. The results suggest that moderate changes in the fatty acid composition in the Western-type diet may be adequate to affect lipoprotein susceptibility to oxidationin vitro, but there is considerable disparity with some indices ofin vivo lipid peroxidation.     

Challenges and industry practices for managing software variability in small and medium sized enterprises

Software variability is an ability to change (configure, customize, extend) software artefacts (e.g. code, product, domain requirements, models, design, documentation, test cases) for a specific context. Optimized variability management can lead a software company to 1) shorter development lead time, 2) improved customer and improved user satisfaction, 3) reduced complexity of product management (more variability, same $) and 4) reduced costs (same variability, less $). However, it is not easy for software companies, especially small and medium size of enterprises to deal with variability. In this paper we present variability challenges and used practices collected from five SMEs. Our study indicates that increased product complexity can lead growing SMEs to the time-consuming decision-making. Many of the analyzed medium size of companies also expect improved tool support to help them to boost their productivity when managing increasingly complex products and increasing amount of variants In fact, in many of the analysed SMEs, a high level of automation in design, release management and testing are or become a key factor for market success By introducing the challenges and used practices related to variability the paper deepens understanding of this highly relevant but relatively under-researched phenomenon and contributes to the literature on software product line engineering.     

Readout methods for an inductively coupled resonance sensor used in pressure garment application

The methods needed to inductively read a passive resonance sensor in pressure measurement are studied. A simple dual-layer pressure sensor, a small portable phase response measurement unit and the methods to extract a coupling coefficient compensated resonance frequency are presented. The functionality and accuracy of the measurement are tested in a test rig and demonstrated in a realistic measurement environment. According to the test measurements, the overall performance of this wireless system is promising and the accuracy is within the typical range of the measurements made in the field of pressure garments.     

Effects of submerged macrophytes on sediment resuspension and internal phosphorus loading in Lake Hiidenvesi (southern Finland)

The effects of submerged macrophytes on sediment resuspension and internal phosphorus loading in the shallow Kirkkoj?rvi basin of Lake Hiidenvesi were studied by sedimentation traps and sediment and water samples. During the 83 d study period, 793 g DW m(-2) of sediment was resuspended within the stand formed by Ranunculus circinatus, Ceratophyllum demersum and Potamogeton obtusifolius. Outside the stand, 1701g DW m(-2) sediment resuspension was measured during the same period. Water turbidity and concentration of suspended solids (SS) were significantly lower within the plant bed compared with the surrounding water area. Despite the higher concentration of inorganic suspendoids, the concentration of chlorophyll a was higher in the open water than within the submerged plant bed, owing to the enhanced nutrient recycling rate in the absence of submerged plants. With the resuspended sediment, 11.8 mg Pm(-2)d(-1) was brought into the water column within the stand and 24.5 mg Pm(-2)d(-1) outside the stand. Within the macrophyte stand, resuspended particles absorbed phosphorus from the water (indicated by the inverse relationship between SS and soluble reactive phosphorus), which was probably connected to the lowered phosphorus concentration of surface sediment due to uptake by macrophytes.     

Probabilistic simulation of fire endurance of a wooden beam

This paper presents a probabilistic simulation approach to assessment of the fire endurance of a wooden load-bearing beam in a fire. The approach introduces several novel modelling techniques developed by VTT, such as the probabilistic fire simulator which is an interface enabling to run fire simulation models in the Monte Carlo mode and the time-dependent event-tree method which enables to take into account the active fire safety measures such as detectors, first-aid fire fighting, sprinklers and fire brigade intervention. Also the simulation of the response to heat and the mechanical performance of the structure are carried out using the Monte Carlo technique. The charring rate of the wooden beam is calculated by a new model that includes explicitly the principal sources of uncertainties and variabilites. The results show explicitly the effectiveness of different fire safety measures in reducing the risk of structural failure.     

The Effect of Lithium Disilicate Ceramic Surface Neutralization on Wettability of Silane Coupling Agents and Adhesive Resin Cements

This in vitro study was aimed to evaluate the possible changes in wettability of an etched glass ceramic surface to silane primers, adhesive resin and resin cement when the surface had been neutralized by a special neutralizing agent after etching. Rectangular shaped specimens were cut from the CAD blocks of an e-max lithium disilicate glass ceramic, cut specimens were sequentially polished and ultrasonically cleaned. All the specimens were etched for 20 s with 5% hydrofluoric acid and ultrasonically cleaned. Specimens were randomly assigned to one control group (without neutralization) and one treatment group (with neutralization) having 20 specimens each. The specimens of each group were further divided into two subgroups having 10 specimens each and tested to determine the effect of neutralizing agent on wettability of experimental and commercial silanes. Each subgroup specimen was tested for wettability to adhesive resin and commercial resin cement. Data were analyzed using two-way ANOVA. Neutralizing the ceramic surface did not show a significant effect on wettability to the silanes and the resin based materials, but the experimental silane showed better wettability than the commercial silane. The adhesive resin had statistically significant lower contact angle (high wettability) values than the commercial resin cement. The results of the current study suggested that the neutralizing agent did not have an impact on the wettability of the etched ceramic. However, there were differences in wetting properties of the silane primers, and adhesive resin versus resin composite luting cements.