7,447 research outputs found

    How does investor sentiment affect stock market crises? Evidence from panel data

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    We test the impact of investor sentiment on a panel of international stock markets. Specifically, we examine the influence of investor sentiment on the probability of stock market crises. We find that investor sentiment increases the probability of occurrence of stock market crises within a one-year horizon. The impact of investor sentiment on stock markets is more pronounced in countries that are culturally more prone to herd-like behavior and overreaction or in countries with low institutional involvement. Results also suggest that investors' sentiment is not a reliable predictor of stock market reversal pointsInvestor sentiment ; stock market crises ; reversal points

    Transformation of coal mineral matter during pulverized coal combustion

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    The theoretical development of a sequence of mathematical sub-models capable of calculating the fouling tendency of a coal based on microscopic analysis of the coal mineral matter is described. The sub-models interpret computer controlled-scanning electron microscope analysis data in terms of mineral size and chemical composition distributions; follow the transformation of these mineral property distributions during the combustion of the coal; determine the probability of the resultant fly ash particles impacting on boiler-tube surfaces and of their sticking upon impaction. The sub-models are probabilistic, and take account of the particle-to-particle variation of coal mineral matter and fly ash properties by providing mean values and variances for particle size, chemical composition and viscosity. The various sub- models are combined into a Coal Fouling Tendency (CFT) computer code. Comparison of CFT modeling results obtained for any coal or coal blend with those obtained for a coal whose behavior in a given boiler plant is known, can give useful information on their relative fouling tendencies. The report also includes data on the deposition characteristics of five coals or coal blends, obtained from combustion experiments in the 1-2 MW flame tunnel at MIT. The measurement data were used for validation of the CFT calculations, and for ranking the five fuels with respect to their fouling behavior. Similar ranking of other coals, without combustion testing, can be based solely on results from the CFT model, and examples are given in the report.New England Power Service Co., ABB-Combustion Engineering, Public Service Electric & Gas Co., Empire State Electric Energy Research Corp., ENEL S.p.A., and Electric Power Research Institut

    Direct neutron capture of 48Ca at kT = 52 keV

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    The neutron capture cross section of 48Ca was measured relative to the known gold cross section at kT = 52 keV using the fast cyclic activation technique. The experiment was performed at the Van-de-Graaff accelerator, Universitaet Tuebingen. The new experimental result is in good agreement with a calculation using the direct capture model. The 1/v behaviour of the capture cross section at thermonuclear energies is confirmed, and the adopted reaction rate which is based on several previous experimental investigations remains unchanged.Comment: 9 pages (uses Revtex), 2 postscript figures, accepted for publication as Brief Report in Phys. Rev.

    Nitric oxide turnover in permeable river sediment

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    We measured nitric oxide (NO) microprofiles in relation to oxygen (O-2) and all major dissolved N-species (ammonium, nitrate, nitrite, and nitrous oxide [N2O]) in a permeable, freshwater sediment (River Weser, Germany). NO reaches peak concentrations of 0.13 mu mol L-1 in the oxic zone and is consumed in the oxic-anoxic transition zone. Apparently, NO is produced by ammonia oxidizers under oxic conditions and consumed by denitrification under microoxic conditions. Experimental percolation of sediment cores with aerated surface water resulted in an initial rate of NO production that was 12 times higher than the net NO production rate in steady state. This initial NO production rate is in the same range as the net ammonia oxidation rate, indicating that NO is transiently the main product of ammonia oxidizers. Stable isotope labeling experiments with the N-15-labeled chemical NO donor S-nitroso-N-acetylpenicillamine (SNAP) (1) confirmed denitrification as the main NO consumption pathway, with N2O as its major product, (2) showed that denitrification combines one free NO molecule with one NO molecule formed from nitrite to produce N2O, and (3) suggested that NO inhibits N2O reduction

    Metabolic changes in the lungs after ischaemia

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    CITATION: Engelbrecht, F. M., Edwards, I. J. & De Beer, D. P. 1980. Metabolic changes in the lungs after ischaemia. South African Medical Journal, 58:409-413.The original publication is available at http://www.samj.org.zaThe effects of variable periods of ischaemia on the isolated lungs of rats and rabbits, stored for up to 6 hours at 4°C, 21°C and 37°C under standardized conditions, were investigated in vitro in terms of oxygen consumption, the rate of 1-14C-leucine incorporation into soluble proteins, and 1-14C-palmitate incorporation into total phospholipids and lipid fractions. The endogenous oxygen uptake of rat lung slices in an air phase, from tissues stored at 4°C and 21°C under ischaemic conditions for 6 hours and at 37°C for 4 hours, was significantly different from the control values. The oxygen uptake of lungs from animals anaesthetized with pentobarbitone prior to exsanguination and stored for only 2 hours at 37°C differed significantly from control values. Judged by the rate of incorporation of radiolabelled leucine into soluble proteins and that of palmitate into total lipids and phospholipids of lungs after storage for increasing periods at 4°C and 37°C, significant differences were already found after 1 1/2 hours. From this observation it would appear that these parameters are very sensitive indicators for assessing irreversible lung damage due to ischaemia.Publisher’s versio

    Human error analysis: Review of past accidents and implications for improving robustness of system design

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    Since the establishment of the high-technology industry and industrial systems, developments of new materials and fabrication techniques, associated with cutting-edge structural and engineering assessments, are contributing to more reliable and consistent systems, thus reducing the likelihood of losses. However, recent accidents are acknowledged to be linked to human factors which led to catastrophic consequences. Therefore, the understanding of human behavioural characteristics interlaced with the actual technology aspects and organisational context is of paramount importance for the safety & reliability field. This study first approaches this multidisciplinary problem by classifying and reviewing 200 major accident data from insurance companies and regulatory authorities under the Cognitive Reliability and Error Analysis framework. Then, specific attention is dedicated to discuss the implications for improving robustness of system design and tackling the surrounding factors and tendencies that could lead to the manifestation of human errors

    Learning from accidents: Investigating the genesis of human errors in multi-attribute settings to improve the organisation of design

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    Remarkable advances in engineering and system controls in recent times and the consequent development of state-of-the-art technologies are clearly resulting in economic, environmental and safety benefits to the society. Latest disasters, however, put human error in the glare of the media spotlight. The February 2016 train collision in southern Bavaria, Germany, which took 11 lives and left more than 90 people injured, is one of several examples where human errors appear to have played a significant role in a major accident. In this emblematic case, the railway system had multiple safety barriers in place, such as an automatic braking system if a train crosses a stop signal, but the track controller had reportedly disabled it. When he realised the error and tried to warn the drivers, it was too late (BBC, 2016)

    10Be in Ice Cores and 14C in Tree Rings: Separation of Production and Climate Effects

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    Cosmogenic radionuclides are more and more used in solar activity reconstructions. However, the cosmogenic radionuclide signal also contains a climate component. It is therefore crucial to eliminate the climate information to allow a better interpretation of the reconstructed solar activity indices. In this paper the method of principal components is applied to 10Be data from two ice cores from opposite hemispheres as well as to 14C data from tree rings. The analysis shows that these records are dominated by a common signal which explains about 80% of the variance on multi decadal to multi millennial time scales, reflecting their common production rate. The second and third components are significantly different for 14C and 10Be. They are interpreted as system effects introduced by the transport of 10Be and 14C from the atmosphere where they are produced to the respective natural archives where they are stored. Principal component analysis improves significantly extraction of the production signal from the cosmogenic isotope data series, which is more appropriate for astrophysical and terrestrial studie

    Measurement of neutron capture on 48^{48}Ca at thermal and thermonuclear energies

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    At the Karlsruhe pulsed 3.75\,MV Van de Graaff accelerator the thermonuclear 48^{48}Ca(n,γ\gamma)49^{49}Ca(8.72\,min) cross section was measured by the fast cyclic activation technique via the 3084.5\,keV γ\gamma-ray line of the 49^{49}Ca-decay. Samples of CaCO3_3 enriched in 48^{48}Ca by 77.87\,\% were irradiated between two gold foils which served as capture standards. The capture cross-section was measured at the neutron energies 25, 151, 176, and 218\,keV, respectively. Additionally, the thermal capture cross-section was measured at the reactor BR1 in Mol, Belgium, via the prompt and decay γ\gamma-ray lines using the same target material. The 48^{48}Ca(n,γ\gamma)49^{49}Ca cross-section in the thermonuclear and thermal energy range has been calculated using the direct-capture model combined with folding potentials. The potential strengths are adjusted to the scattering length and the binding energies of the final states in 49^{49}Ca. The small coherent elastic cross section of 48^{48}Ca+n is explained through the nuclear Ramsauer effect. Spectroscopic factors of 49^{49}Ca have been extracted from the thermal capture cross-section with better accuracy than from a recent (d,p) experiment. Within the uncertainties both results are in agreement. The non-resonant thermal and thermonuclear experimental data for this reaction can be reproduced using the direct-capture model. A possible interference with a resonant contribution is discussed. The neutron spectroscopic factors of 49^{49}Ca determined from shell-model calculations are compared with the values extracted from the experimental cross sections for 48^{48}Ca(d,p)49^{49}Ca and 48^{48}Ca(n,γ\gamma)49^{49}Ca.Comment: 15 pages (uses Revtex), 7 postscript figures (uses psfig), accepted for publication in PRC, uuencoded tex-files and postscript-files also available at ftp://is1.kph.tuwien.ac.at/pub/ohu/Ca.u

    Learning from major accidents to improve system design

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    © 2015 Elsevier Ltd.Despite the massive developments in new technologies, materials and industrial systems, notably supported by advanced structural and risk control assessments, recent major accidents are challenging the practicality and effectiveness of risk control measures designed to improve reliability and reduce the likelihood of losses. Contemporary investigations of accidents occurred in high-technology systems highlighted the connection between human-related issues and major events, which led to catastrophic consequences. Consequently, the understanding of human behavioural characteristics interlaced with current technology aspects and organisational context seems to be of paramount importance for the safety & reliability field. First, significant drawbacks related to the human performance data collection will be minimised by the development of a novel industrial accidents dataset, the Multi-attribute Technological Accidents Dataset (MATA-D), which groups 238 major accidents from different industrial backgrounds and classifies them under a common framework (the Contextual Control Model used as basis for the Cognitive Reliability and Error Analysis Method). The accidents collection and the detailed interpretation will provide a rich data source, enabling the usage of integrated information to generate input to design improvement schemes. Then, implications to improve robustness of system design and tackle the surrounding factors and tendencies that could lead to the manifestation of human errors will be effectively addressed
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