Neutron diffraction and Raman studies of the incorporation of sulfate in silicate glasses

The oxidation state, coordination and local environment of sulphur in alkali silicate (R2O-SiO2; R= Na, Li) and alkali-alkaline earth silicate (Na2O-MO-SiO2; M= Ca, Ba) glasses have been investigated using neutron diffraction and Raman spectroscopy. With analyses of both the individual total neutron correlation functions, and of suitable doped-undoped differences, the S-O bonds and (O-O)S correlations were clearly isolated from the other overlapping correlations due to Si-O and (O-O)Si distances in the SiO4 tetrahedra, and the modifier-oxygen (R-O and M-O) distances. Clear evidence was obtained that the sulphur is present as SO4 2- groups, confirmed by the observation in the Raman spectra of the symmetric S-O stretch mode of SO4 2- groups. The modifier-oxygen bond length distributions were deconvoluted from the neutron correlation functions by fitting. The Na-O and Li-O bond length distributions were clearly asymmetric, whereas no evidence was obtained for asymmetry of the Ca-O and Ba-O distributions. A consideration of the bonding shows that the oxygen atoms in the SO4 2- groups do not participate in the silicate network, and as such constitute a third type of oxygen, ‘non-network oxygen’, in addition to the bridging and non-bridging oxygens that are bonded to silicon atoms. Thus each individual sulphate group is surrounded by a shell of modifier, and is not connected directly to the silicate network. The addition of SO3 to the glass leads to a conversion of oxygen atoms within the silicate network from non-bridging to bridging, so that there is a repolymerisation of the silicate network. There is evidence that SO3 doping leads to changes in the form of the distribution of Na-O bond lengths, with a reduction in the fitted short bond coordination number, and an increase in the fitted long bond coordination number, and this is consistent with a repolymerisation of the silicate network. In contrast, there is no evidence that SO3 doping leads to a change in the distribution of Li-O bond lengths, with a total Li-O coordination number consistently in excess of four

Applied sensor fault detection, identification and data reconstruction based on PCA and SOMNN for industrial systems

The paper presents two readily implementable approaches for Sensor Fault Detection, Identification (SFD/I) and faulted sensor data reconstruction in complex systems, in real-time. Specifically, Principal Component Analysis (PCA) and Self-Organizing Map Neural Networks (SOMNNs) are demonstrated for use on industrial turbine systems. In the first approach, Squared Prediction Error (SPE) based on the PCA residual space is used for SFD. SPE contribution plot is employed for SFI. A missing value approach from an extension of PCA is applied for faulted sensor data reconstruction. In the second approach, SFD is performed by SOMNN based Estimation Error (EE), and SFI is achieved by EE contribution plot. Data reconstruction is based on an extension of the SOMNN algorithm. The results are compared in each examining stage. The validation of both approaches is demonstrated through experimental data during the commissioning of an industrial 15MW turbine

Dietary assessment in Whitehall II: comparison of 7d diet diary and food-frequency questionnaire and validity against biomarkers

The aim of the present cross-sectional study was to examine the agreement and disagreement between a 7 d diet diary (7DD) and a self-administered machine-readable food-frequency questionnaire (FFQ) asking about diet in the previous year, and to validate both methods with biomarkers of nutrient intake. The subjects were an age- and employment-grade-stratified random subsample of London-based civil servants (457 men and 403 women), aged 39–61 years, who completed both a 7DD and a FFQ at phase 3 follow-up (1991–1993) of the Whitehall II study. Mean daily intakes of dietary energy, total fat, saturated, monounsaturated and polyunsaturated fatty acids, linoleic acid, total carbohydrate excluding fibre, sugars, starch, dietary fibre, protein, vitamin C, vitamin E (as α-tocopherol equivalents), folate, carotenes (as total β-carotene activity), Fe, Ca, Mg, K and alcohol were measured. Serum cholesteryl ester fatty acids (CEFA), plasma α-tocopherol and β-carotene were also measured as biomarkers. Estimates of mean energy intake from the two methods were similar in men, and some 10 % higher according to the FFQ in women. Compared with the 7DD, the FFQ tended to overestimate plant-derived micronutrient intakes (carotenes from FFQ v. 7DD men 2713 (SD 1455) V. 2180 (sd 1188) μg/d, women 3100 (sd 1656) v. 2221 (sd 1180) μg/d, both differences P<0·0001) and to underestimate fat intake. Against plasma β-carotene/cholesterol, carotene intake was as well estimated by the FFQ as the 7DD (Spearman rank correlations, men 0·32 v. 0·30, women 0·27 v. 0·22, all P≤0·0001, energy-adjusted data). Ranking of participants by other nutrient intakes tended to be of the same order according to the two dietary methods, e.g. rank correlations for CEFA linoleic acid against FFQ and 7DD estimates respectively, men 0·38 v. 0·41, women 0·53 v. 0·62, all P≤0·0001, energy-adjusted % fat). For α-tocopherol there were no correlations between plasma level and estimated intakes by either dietary method. Quartile agreement for energy-adjusted nutrient intakes between the two self-report methods was in the range 37–50 % for men and 32–44 % for women, and for alcohol, 57 % in both sexes. Disagreement (misclassification into extreme quartiles of intake) was in the range 0–6 % for both sexes. The dietary methods yielded similar prevalences (about 34 %) of low energy reporters. The two methods show satisfactory agreement, together with an expected level of systematic differences, in their estimates of nutrient intake. Against the available biomarkers, the machine-readable FFQ performed well in comparison with the manually coded 7DD in this study population. For both methods, regression-based adjustment of nutrient intake to mean dietary energy intake by gender appears on balance to be the optimal approach to data presentation and analysis, in view of the complex problem of low energy reporting

Effects of residual charge on the performance of electro-adhesive grippers

Electro-adhesion is the new technology for constructing gripping solutions that can be used for automation of pick and place of a variety of materials. Since the technology works on the principle of parallel plate capacitors, there is an inherent ability to store charge when high voltage is applied. This causes an increased release time of the substrate when the voltage is switched off. This paper addresses the issue of residual charge and suggests ways to overcome the same, so that the performance of the gripper can be improved in a cycle of pick and release. Also a new universal equation has been devised, that can be used to calculate the performance of any gripping solution. This equation has been used to define a desired outcome (K) that has been evaluated for different configurations of the suggested electro-adhesive gripper

The Growth And Development Of Education In Watauga County

The purpose of this study is to give the history of the development of education in Watauga County, North Carolina, from the beginning of education in the county to 1950. An attempt is also made to compare the development of education in Watauga County with the state as a whole, and to offer practical suggestions for improving and developing the school system

The environment of iron in silicate glasses

Iron species in glass are vital to applications such as solar control, and greater understanding of these species is required. Redox, coordination, distribution and environment of iron in alkali-alkaline earth-silica glasses containing 0-5 molar % Fe203 have been studied using a multi-technique approach. Wet chemical analysis provided values of the Fee+/EFe redox ratio and these are in agreement with those obtained from optical and Mössbauer techniques over a wide range of glass compositions and Fe203 contents. The Fee+/EFe ratio is independent of iron content in the glasses studied, provided that melting conditions allow sufficient equilibration with the furnace atmosphere. As iron content increases, Fe-Fe near-neighbour interactions have an increasing influence on measured properties. Mössbauer parameters indicate a wider range of site occupancies by Fe 2+ and Fe 3+ at low iron contents. Electron spin resonance suggests some clustering of Fe ions even at low iron concentrations. The amount of clustering is proportional to the square of the molar Fe203 content. Increasing alkali / alkaline earth ionic radius ratio promotes clustering at all Fe203 contents. The effects of alkali and alkaline earth ions on the redox, distribution, coordination and environment of Fe ions in these glasses generally fall into two behavioural categories which have been termed "collective" and "selective". Collective behaviour occurs when alkali and alkaline earth ions have similar effects on a property and the overall effect is cumulative. This is characterised by proportionality with theoretical optical basicity of the glass. Many parameters associated with Fe 2+ ions fall into this category. Selective behaviour occurs when alkali and alkaline earth ions have opposing effects on a property, suggesting competition or selectivity between ion types. This is characterised by proportionality with the alkali / alkaline earth ionic radius ratio. The redox ratio and several parameters associated with the clustering, coordination and environment of Fe 3+ ions fall into this category. Glasses containing MgO can exhibit behaviour dissimilar to the other alkaline earth oxides; molar volume, redox, coordination and clustering are affected. These phenomena may be due to some Mg 2+ ions occupying tetrahedral sites

Briquetting of waste glass cullet fine particles for energy-saving glass manufacture

Fine particles of glass cullet (fines) arising during glass recycling cannot presently be recycled into glass manufacture due to the potential for bubble formation and foaming. Consolidation of glass fines into briquettes could enable their re-introduction into furnaces, reducing waste and glass melting energies. Properties of briquetted cullet fines and briquette melting behaviour in soda-lime-silica glass batches are presented. Morphology and density of glass fines and briquettes; and briquette mass and mechanical properties as functions of time after formation were analyzed. Compressive strength increases linearly with time after briquette formation. With slight batch modifications to maintain the same final glass composition, up to 15 wt % briquettes were successfully added to a representative container glass batch and melted. Results confirm that briquette batch additions can provide equivalent final glass composition, optical absorption characteristics and redox to briquette-free batches, supporting their industrial uptake