Bulk surface photografting process and its applications. I. Reactions and kinetics

A bulk surface photografting process which is conducted in the interface between two polymer films was designed and investigated. The bulk surface photografting is a highly efficient process. With this method, the surface of hydrophobic polymers can be made hydrophilic in less than 2 s and a grafted layer 5 μm thick can be obtained in 30 s. The kinetic investigation shows that the bulk surface photografting polymerization involves a four-step reaction process: induction period, surface initiation, successive polymerization, involves a four-step reaction process: induction period, surface initiation, successive polymerization, and solid-phase crosslinking. The photoreduction of benzophenone (BP) takes place in the interlayer between the LDPE films and is a three-stage process: surface photoreduction, secondary photoreduction, and solid-state photoreduction. With regard to the photoreduction of the initiator caused by hydrogen abstraction, the kinetic studies show that the photoreduction rate has a first-order dependence on the BP concentration. The activation energy of the hydrogen abstraction reaction is about 28.5 KJ (6.8 kcal)/mol. With regard to the photografting polymerization reaction, the reaction order of the rate Rp with respect to the monomer is unity and 0.89 with respect to BP. This means that the termination reaction takes place mainly by combination of polymer chain free radicals and semipinacol free radicals from BP. The activation energy of the overall polymerization reaction is around 8.8 kJ (2.1 kcal)/mol. © 1996 John Wiley & Sons, Inc.     

Modification of E-glass fiber surfaces with polyacrylic acid polymers from an aqueous solution

The research reported in the article focuses on modifying glass fiber surfaces with polyacrylic acid (PAA) compounds. E-glass fibers were treated with aqueous polyacrylic acid solution. Polyacrylic acid exchanges its protons with the ions present in the glass surface. Hydrolyzed metal cations may form salt complexes with the dissociated polyacrylic acid. Angular dependent electron spectroscopy for chemical analysis (ESCA) demonstrated that the atomic concentrations of aluminum and calcium in the glass fiber surface were constant throughout the analyzed interval. The cation exchange property of glass fiber was studied using direct current plasma (DCP), which showed that both calcium and aluminum ions were extracted by low concentration polycrylic acid solutions. ESCA studies of were extracted by low concentrationb polyacrylic acid solutions. ESCA studies of the PAA-treated glass fiber showed that the amount of PAA of the glass surface increases with increased acid concentration. A broadened and shifted ESCA peak of the carbon (0 CO) indicates the formation of salt complexes between the polyacrylic acid and metal ions on the glass surface. Polyacrylie acid was modified by an esterification reaction with glycidyl acrylate (GA) in aqueous solution in order to insert organofuctional groups into the PAA chain.     

On the improvement of film cooling performance using tree-shaped network holes: A comparative study

Abstract

For modern high-efficiency gas turbines, film cooling is an essential method to protect the turbine blade from the hot gas, and the issue about how to improve the film cooling performance has attracted much attention. This study presents a new design concept used for film cooling in gas turbine to improve the overall cooling effectiveness and better decrease the metal temperature of the blade at the same time. A tree-shaped film cooling structure is considered. To validate the superiority of the proposed structure, a series of numerical simulation cases are conducted at three typical blowing ratios (i.e. 0.5, 0.764, and 0.9). The first case is a film cooling channel with a single film hole with a diameter of 5?mm and it is inclined by α?=?45° relative to the mainstream direction and the other three cases are tree-shaped structures with one level, two levels and three levels of bifurcations. Moreover, the same boundary conditions and turbulence model (realizable k–ε) are adopted, and three-dimensional numerical simulations are used for all cases. The computed results show that the higher the blowing ratio, the better is the overall effectiveness downstream the film holes of the tree-shaped structures, whereas the opposite is valid for the case with a single film hole. Additionally, the overall effectiveness of the tree-shaped structures is improved more than 50% compared with Case 1 with a single film hole, and the results also demonstrate that the more levels of the structure, the lower the metal temperatures will be. Therefore, it is indicated that this research will make a contribution to a higher performance gas turbine.     

CeO2−CoO Phase Diagram

Phase equilibria in the CeO₂−CoO system at temperatures above 1500°C were investigated. The microstructures and the phase compositions of the DTA (differential thermal analysis) samples and the quenched solid pellets were analyzed using SEM (scanning electron microscope), EDX (energy dispersive X-ray), and WDX (wavelength dispersive X-ray). A eutectic reaction was found at 1645 ± 5°C. The eutectic point was calculated to be at 82 ± 1.5 mol% CoO. The eutectic phases were the CeO₂-rich phase (containing <5 mol% CoO) and the CoO-rich phase (containing ∼0.5 mol% CeO₂). At 1580°C, the solubility of CoO in CeO₂ was ∼3 mol%.     

Building and exports

The building recession in many western industrialised countries has obliged their construction industries to look abroad for new markets. A Swedish view of this situation and the scope for consultancy work overseas is given here by a partner in civil engineering consultants Kjessler and Mannerstråle, AB, of Stockholm.

Most recent estimates, incidentally, put the annual value of such Swedish construction consultancy work abroad as £50-£60 million, about 60 per cent of it in the Middle East.     

European wood pellet market integration - A study of the residential sector

The integration of European energy markets is a key goal of EU energy policy, and has also been the focal point of many scientific studies in recent years. International markets for coal, oil, natural gas and electricity have previously been investigated in order to determine the extent of the respective markets. This study enhances this field of research to bioenergy markets. Price series data and time series econometrics are used to determine whether residential sector wood pellet markets of Austria, Germany and Sweden are integrated. The results of the econometric tests show that the German and Austrian markets can be considered to be integrated, whereas the Swedish market is separate from the other two countries. Although increased internationalization of wood pellet markets is likely to contribute to European price convergence and market integration, this process is far from completed.     

Growth modulation of low density lipoprotein receptor sterol sensitivity in cultured human fibroblasts

Sterols regulate low density lipoprotein (LDL) receptor and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase gene expressions by end product repression. Studies on cultured cells have shown that growing cells have a higher LDL uptake than quiescent cells and that incubation of cells with growth factors or mitogenic compounds leads to sterol-resistant upregulation of LDL receptor gene expression. The recent finding that elevated LDL receptor activity in acute myelogenous leukemia cells was characterized by a decreased sensitivity to downregulation by sterols raises the possibility that the mechanism behind this is related to the cellular growth rate. By using cultured human fibroblasts as a model system we therefore studied whether growth modulation of sterol sensitivity takes place in normal actively growing cells. Judging from the ability of sterols (25-hydroxycholesterol+cholesterol) to inhibit ¹²⁵I-LDL degradation, we found that the sensitivity to sterols varied markedly between cells of different densities. The lowest sensitivity to sterols and highest ¹²⁵I-LDL degradation rate were found in subconfluent cells, whereas sparse and confluent cells were the most sensitive ones. In contrast to the LDL receptor, HMG-CoA reductase sterol sensitivity did not appear to be growth regulated. We conclude that growth-dependent modulation of sterol sensitivity and LDL receptor activity takes place in normal human fibroblasts. Modulation of sterol sensitivity may be an important mechanism to ensure an adequate cholesterol supply in growing cells.     

Energy saving in existing housing

In one of several pilot projects financed through the Swedish Council of Building Research, the Department of Building Technology at the Royal Institute of Technology, Stockholm, showed how energy consumption could be reduced by more than 50 per cent in a typical three-storey block of flats built around 1940. Thermal insulation levels of the building were low by Swedish standards — walls and roofs having U-values of 1.2 W/m². °C — and oil consumption was as high as 60 litres per m² of net dwelling area.