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991.
992.
The ATWS transient “Loss of main feed water supply” in a generic four-loop PWR at the nominal power of 3750 MW was analyzed using the coupled code system DYN3D/ATHLET. A variation of the MOX-fuel-assembly portion in the core has an effect on the reactivity coefficients of the fuel temperature and the moderator density. These two parameters mainly influence the behaviour of the coolant pressure, which is safety-relevant. It has been demonstrated that the pressure maximum decreases with an increasing portion of MOX. For all core loadings considered, both primary-circuit mechanical integrity and sufficient core cooling are guaranteed. 相似文献
993.
Abstract Mild hydrocracking of 30% crude oil (Indian Crude oil.North Gujarat base)solution in light gas oil is carried out over a commercial hydrotreating catalyst at a temperature range of 300–450°c and pressure of 6. 8–20.OMpa in laboratory reactor. About 30 to 60% of the long residue (365° c+ cut) in the solution is converted to light distillates. A mathematical model has been developed to predict the yields of products. 相似文献
994.
Researchers investigated the impact of podcasting on student motivation in the online environment during fall 2008 and spring 2009. Data were collected from students enrolled in fourteen online courses at a research university in the United States. One hundred and ninety-one students completed a modified version of the Instructional Materials Motivation Survey (Keller, 2006); it has four subscales: attention, relevance, confidence, and satisfaction. Strong positive relationships between all subscales were detected. Results indicate students were moderately motivated by the use of podcasts in their online courses. Statistically significant differences in student motivation based on gender, class standing, and prior online learning experience were found. Benefits of using podcasts and recommendations for improvement of the multimedia files were offered by users. 相似文献
995.
A. Yu. Mollaev I. K. Kamilov S. F. Marenkin R. K. Arslanov U. Z. Zalibekov T. R. Arslanov A. A. Abdullaev I. V. Fedorchenko 《Inorganic Materials》2010,46(9):919-923
The ferromagnetic semiconductor Cd0.7Mn0.3GeAs2 undergoes a high-pressure ferromagnetic-to-antiferromagnetic phase transition. We have studied this transition at different
temperatures. From magnetic-field dependences of the Hall resistance measured at different temperatures, we have derived the
normal and anomalous Hall coefficients of the material as functions of temperature. Its transverse magnetoresistance changes
from positive to negative near the ferromagnetic-to-antiferromagnetic phase transition. 相似文献
996.
L. Ekman A.-K. Nyman H. Landin U. Magnusson K. Persson Waller 《Journal of dairy science》2018,101(1):556-571
Udder cleft dermatitis (UCD) is an inflammatory skin condition affecting the anterior parts of the udder of dairy cows. The lesions may present as mild or severe skin lesions and have been associated with mastitis and digital dermatitis. The full etiology and pathogenesis are not understood and no large-scale studies have investigated prevalence and risk factors. Therefore, the main objectives of the study were to investigate the prevalence of mild and severe UCD in Swedish dairy herds and to identify risk factors associated with such lesions. We also wanted to investigate risk factors for all cases of UCD and to determine whether UCD increases the risk for mastitis and culling. A random sample of 100 freestall dairy herds were included in the study, and each herd was visited once. Cows were registered as having no, mild, or severe UCD. Additional cow and herd data were obtained via observations, interviews, and the Swedish Official Milk Recording Scheme. The data were analyzed using logistic regression models to identify risk factors for mild and severe UCD. In total, data from 3,479 cows in 99 herds were analyzed. The prevalence of mild and severe UCD was 19 and 9%, respectively. Lesions were found in 98 of 99 herds but the within-herd prevalence of mild (0–43%) and severe (0–33%) UCD varied notably between herds. Breed (Swedish Red compared with Swedish Holstein), certain udder conformation traits, and higher parity were risk factors associated with increased risk of UCD. In addition, cows with hock lesions and cows in herds with high incidence of culling due to hoof and leg diseases had a higher risk for mild UCD. More days in milk and high milk yield were cow-related risk factors associated with severe UCD. Three housing-related factors (shorter cubicles, mattress as cubicle base, and cubicles installed before 2001 compared with 2001–2005), a high incidence of veterinary-treated clinical mastitis and culling due to udder diseases, and a low incidence of culling of first-parity cows in early lactation were herd-related risk factors associated with increased risk for severe UCD. In addition, cows in herds with a high proportion of heifers older than 17 mo that were not inseminated were associated with lower risk of all UCD. Finally, UCD was not associated with the outcomes milk somatic cell count, veterinary-treated clinical mastitis, or culling in the multivariable analyses. The etiology of UCD is most likely multifactorial, involving udder conformation traits and other cow-related risk factors as well as herd-related risk factors. The high prevalence of severe UCD lesions in Swedish dairy cows emphasizes the need for preventive measures and efficient treatments. 相似文献
997.
The use of superplastic shaping in the manufacture of hollow components is considered. The influence of the threshold stress
on the basic shaping parameters is studied. 相似文献
998.
Iron oxide n-Fe2O3 nanowire photoelectrodes were synthesized by thermal oxidation of Fe metal sheet (Alfa Co. 0.25 mm thick) in an electric oven then tested for their photoactivity. The photoresponse of the n-Fe2O3 nanowires was evaluated by measuring the rate of water splitting reaction to hydrogen and oxygen, which is proportional to photocurrent density, Jp. The optimized electric oven-made n-Fe2O3 nanowire photoelectrodes showed photocurrent densities of 1.46 mA cm−2 at measured potential of 0.1 V/SCE at illumination intensity of 100 mW cm−2 from a Solar simulator with a global AM 1.5 filter. For the optimized carbon modified (CM)-n-TiO2 synthesized by thermal flame oxidation the photocurrent density for water splitting was found to increase by two fold to 3.0 mA cm−2 measured at the same measured potential and the illumination intensity. The carbon modified (CM)-n-Fe2O3 electrode showed a shift of the open circuit potential by −100 mV/SCE compared to undoped n-Fe2O3 nanowires. A maximum photoconversion efficiency of 2.3% at applied potential of 0.5 V/Eaoc was found for CM-n-Fe2O3 compared to 1.69% for n-Fe2O3 nanowires at higher applied potential of 0.7 V/Eaoc. These CM-n- Fe2O3 and n- Fe2O3 nanowires thin films were characterized using photocurrent density measurements under monochromatic light illumination, UV-Vis spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM). 相似文献
999.
Effects of ventilation rate per person and per floor area on perceived air quality,sick building syndrome symptoms,and decision‐making
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R. Maddalena M. J. Mendell K. Eliseeva W. R. Chan D. P. Sullivan M. Russell U. Satish W. J. Fisk 《Indoor air》2015,25(4):362-370
Ventilation rates (VRs) in buildings must adequately control indoor levels of pollutants; however, VRs are constrained by the energy costs. Experiments in a simulated office assessed the effects of VR per occupant on perceived air quality (PAQ), Sick Building Syndrome (SBS) symptoms, and decision‐making performance. A parallel set of experiments assessed the effects of VR per unit floor area on the same outcomes. Sixteen blinded healthy young adult subjects participated in each study. Each exposure lasted four hours and each subject experienced two conditions in a within‐subject study design. The order of presentation of test conditions, day of testing, and gender were balanced. Temperature, relative humidity, VRs, and concentrations of pollutants were monitored. Online surveys assessed PAQ and SBS symptoms and a validated computer‐based tool measured decision‐making performance. Neither changing the VR per person nor changing the VR per floor area, had consistent statistically significant effects on PAQ or SBS symptoms. However, reductions in either occupant‐based VR or floor‐area‐based VR had a significant and independent negative impact on most decision‐making measures. These results indicate that the changes in VR employed in the study influence performance of healthy young adults even when PAQ and SBS symptoms are unaffected. 相似文献
1000.