Silicon for thin-film transistors

We are standing at the beginning of the industrialization of flexible thin-film transistor (TFT) backplanes. The two important research directions for the TFTs are (i) processability on flexible substrates and (ii) sufficient field-effect mobilities of electrons and holes to support complementary metal insulator semiconductor operation. The most important group of TFT capable semiconductors are the several modifications of silicon films: amorphous, nanocrystalline and microcrystalline. We summarize their TFT properties and their compatibility with foil substrate materials.     

Is image selection a useful strategy to decrease the transmission time in teleradiology? A study using 100 emergency cranial CTs

This study examines the suitability of working with a selection of images in a teleradiology consulting system in neurological or neurosurgical emergency situations. The teleradiology system was based on IBM-compatible personal computers, video digitization for data acquisition, and data transmission by Integrated System Digital Network. Forty normal and 60 abnormal emergency cranial computed tomograms were shown to a radiologist on call who presented all cases he regarded as pathologic to a neuroradiologic expert by teleradiology. To reduce transmission time, only a selection of images from the CT study was presented (up to four images per case). For each case the on-call radiologist's diagnosis (D(on-call)), the expert's diagnosis on the teleradiology screen (D(monitor)), and the expert's diagnosis on the original film (D(original)) was documented, together with an estimation of the agreement between those diagnoses. There was clinically relevant disagreement between the on-call radiologist's diagnosis and the neuroradiologist's diagnosis based on the image selection on the teleradiology monitor in 23% of cases. A clinically important discrepancy between the neuroradiologist's diagnosis based on the image selection and his diagnosis using the original films was found in 30% of cases. This was due to the presence of clinically relevant information on images not transferred by the on-call radiologist. Image quality of the transferred images was sufficient in all cases. Drastic selection of images from a complete CT study leads to a high rate of incorrect diagnoses and is not appropriate to reduce transmission time in teleradiology.     

Optimizing 100%‐renewable grids through shifting residential water‐heater load

A low‐carbon electricity supply for Australia was simulated, and the installed capacity of the electrical grid was optimized by shifting the electricity demand of residential electric water heaters (EWHs). The load‐shifting potential of Australia was estimated for each hour of the simulation period using a nationwide aggregate EWH load model on a 90 × 110 raster grid. The electricity demand of water heaters was shifted from periods of low renewable resource and high demand to periods of high renewable resource and low demand, enabling us to effectively reduce the installed capacity requirements of a 100%‐renewable electricity grid. It was found that by shifting the EWH load by just 1 hour, the electricity demand of Australia could be met using purely renewable electricity at an installed capacity of 145 GW with a capacity factor of 30%, an electricity spillage of 20%, and a generation cost of 15.2 ¢/kWh. A breakdown of the primary energy sources used in our scenario is as follows: 43% wind, 29% concentrated solar thermal power, and 20% utility photovoltaic. Sensitivity analysis suggested that further reduction in installed capacity is possible by increasing the load‐shifting duration as well as the volume and insulation level of the EWH tank.     

Sustainable Product Design — Is there more to it than Science,Systems and Computers?1

The conditions are examined through which a company can take an active part in the evolutionary process towards ecologically sustainable societies. Productivity measures, quality perceptions, ecological performance and critical contradictions between business targets have to be identified, based on systematic retrieval and structuring of information of product, processes and practices. It is important that the company selects ecological performance parameters and sets performance targets which show the way towards ecologically sound products, processes and practices and at the same time secure its competitiveness in today's market. It is suggested that an extended quality function deployment process (QFD) can be used for this purpose. By combining this information structure with the modelling possibilities of products, processes and practices that are available in modern computer assisted engineering software (CAE), consequences and feasibilities of new ideas and creative solutions can be checked out continuously. New ideas and creative solutions that really will lead the way towards ecologically sustainable societies, seem to require development- and design-teams that are getting inspiration, visions and wisdom from other areas than the conventional business and university environment. Close cooperation should be encouraged between industry and the universities for building up such inspired environments.     

The Influence of Tocopherols on the Oxidation Stability of Methyl Esters

Tocopherols were found to be the principal natural antioxidants in biodiesel grade fatty acid methyl esters. The stabilising effect of α-, γ- and δ- tocopherols from 250 to 2,000 mg/kg was evaluated by thermal and accelerated storage induction times based on rapid viscosity increase, in sunflower (SME), recycled vegetable oil (RVOME), rapeseed (RME) and tallow (TME) methyl esters. Both induction times showed that stabilising effect is of the order of δ- > γ- > α-tocopherol, and that the stabilising effect increased with concentration. The correlation between the two induction times however was poor, which is probably due to the fact that the time they correspond to two different stages of oxidation. Tocopherols were found to stabilise methyl esters by reducing the rate of peroxide formation while present. The deactivation rates of tocopherols increased with unsaturation of the particular methyl ester and in the present work they were of the order of SME > RME > RVOME > TME. While α-tocopherol was found to be a relatively weak antioxidants, both γ- and δ- tocopherols increased induction times significantly and should be added to methyl esters without natural antioxidants.     

Structural decomposition of energy use in Brazil from 1970 to 1996

This paper examines the sources of changes in energy use of the Brazilian economy of industries and households from 1970 to 1996, using structural decomposition analysis based on the logarithmic mean divisia index technique. Energy use can be decomposed into eight factors that explain changes in overall energy use over the entire time period, and within five sub-periods. The growth of energy use between 1970 and 1996 was mainly influenced by changes in affluence, population and intersectoral dependencies, while changes in direct energy intensity and per capita residential energy use had a retarding impact on energy use. The novel contributions of the paper are the alignment of a previously disparate data set, the use of supply-use tables for SDA, and the application of such an SDA to a developing country. Both contributions involve solving a range of methodological issues pertaining to handling of large data sets.     

Effect of different microstructural features on the hydrogen embrittlement susceptibility of alloy 718

Due to its high strength and acceptable corrosion resistance, Alloy 718 is a viable material for the use in subsea applications. The alloy's susceptibility to hydrogen embrittlement is however limiting its viability. In this work the effect of microstructure on the hydrogen embrittlement susceptibility of Alloy 718 was examined by the use of slow strain rate testing on three different heat treatments. Cathodic pre-charging and polarization during testing were used to introduce hydrogen into the samples. A severe reduction in the ductility of the alloy due to the precipitation phases γ″ and γ′ were found. In addition, one of the heats had a continuous film of a Nb and C rich phase on the grain boundary giving an intergranular fracture mechanism. This intergranular fracture mode was further enhanced by the presence of hydrogen. In the solution annealed condition, the presence of hydrogen reduced the dimple size on the fracture surface.     

A method for the determination of polyunsaturated fatty acid methyl esters in biodiesel: Results of an interlaboratory study

A gas chromatographic method for the determination of fatty acid methyl esters with four or more double bonds in biodiesel was developed and tested. The method is based on gas chromatographic separation on a wax capillary column using methyl tricosanoate as internal standard. The performance of the method was proved with the participation of 11 European laboratories by a Round Robin test on six different biodiesel samples containing different amounts of polyunsaturated fatty acid methyl esters. The results showed that the precision is sufficient around the EN 14214 limit of 1 % (m/m). At lower concentrations the variation is too high. The scope of the application can be given between as 0.6 and 1.5%.     

Mechanics of thin-film transistors and solar cells on flexible substrates

When devices are fabricated on thin foil substrates, any mismatch strain in the device structure makes the work piece curve. Any change of the radius of curvature produces a change in the size of the work piece, and thereby misalignment between individual device layers. To achieve tight tolerances, changes of curvature must be minimized throughout the fabrication process.Amorphous silicon thin-film transistors and solar cells respond differently to externally applied tensile strain. The elastic deformation of the transistor is correlated with small increase in the electron mobility. When the tensile strain reaches 0.34%, crack formation starts and causes an abrupt change in the transistor performance. The performance of solar cells, on the other hand, does not change for tensile strain up to 0.7%. At larger strain the short-circuit current, open-circuit voltage, fill factor, and the efficiency gradually decrease.