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61.
The current standard cosmological model is based on the normalized Friedmann equation 1 = ΩM +ΩΛ +ΩK, where ΩM is the mass density of dark and baryonic matter, ΩΛ the vacuum energy density, and ΩK is the curvature parameter. We show that the Friedmann equation was derived under excessive extrapolations from Einstein’s equations, which are not scale invariant and are “verified” on much smaller scales. We explain why these extrapolations are incorrect, why the unrestricted use of the term “verified” is questionable, and why dark matter may exist only by definition. 相似文献
62.
The production process of mineral wool is affected by several constantly changing factors. The ingredients for the mineral wool are melted in a furnace. The molten mineral charge exits the bottom of the furnace in a water-cooled trough and falls into a fiberization device (the centrifuge). The centrifuge forms the fibers. At this stage binders are injected to bind the fibers together. To ensure the quality of the end product (the consistent thickness) the flow of the bounded fibers must be as constant as possible. One way to ensure that is to control the speed of the conveyor belt that transports the bounded fibers from the centrifuge to the curing process. Predictive functional controller and PID controller are considered to replace an existing algorithm. Both can easily replace an existing one as they do not require any new sensor installation. All three algorithms are presented and tested on a developed plant model. The study showed that the predictive control gives better results than the existing and PID controller. 相似文献
63.
Adéla Grégrová Eva Neradová Vojtěch Kružík Jiří Mazáč Pavel Havelec Helena Čížková 《European Food Research and Technology》2014,239(1):169-174
Possible adulteration of canned products containing spirit vinegar pickle by adding synthetic acetic acid is a significant problem of the food industry. Isotope analyses, which determine botanical origin of acetic acid and also can detect synthetic acid, were applied to detect undeclared addition of synthetic acetic acid to canned products. The aim of the study was to improve the extraction technique for the SNIF-NMR (2H/1H; site-specific natural isotopic fractionation-nuclear magnetic resonance) and IRMS (13C/12C; isotope ratio mass spectrometry) isotope methods and for an atypical matrix and to determine isotope ratios in canned vegetables pickle to prove their adulteration or authenticity. The following set of canned products was analysed: pickled cucumbers (n = 16) and one vinegar pickle purchased in the Czech market and six model (cucumber) pickles. The determined ratios of 2H/1H and 13C/12C for the pickled cucumbers proved to be authentic ranged from 89.4 to 107.0 ppm and from ?28.7 to ?15.6 ‰, respectively; for the synthetic acetic acids diluted with water they ranged from 114.2 to 129.0 ppm and from ?44.9 to ?33.4 ‰, respectively. Isotope analyses were confirmed as a reliable tool for assessing authenticity of canned products. The method enables detection of synthetic acetic acid addition into vinegars and canned vegetables containing vinegar pickle up from 20 % (of total acidity). 相似文献
64.
Sla?ana Žilić Dejan Dodig Vesna Hadži‐Tašković Šukalović Milan Maksimović Goran Saratlić Biljana Škrbić 《International Journal of Food Science & Technology》2010,45(7):1360-1367
Potential beneficial components, including proteins, total phenolics, total flavonoids, carotenoids, tocopherols, and DPPH radical scavenging activity, were investigated in wholemeal of ten bread (T. aestivum L.) and ten durum (T. durum Desf.) novel wheat genotypes. In addition, the activity rate of lipoxygenase (LOX) and peroxidase (POD) enzymes implicated in the antioxidant metabolism was determined. The protein contnet and the antioxidant properties varied according to the two different wheat species, as well as, between the different bread and durum wheat genotypes themselves. The results indicated significant differences in proteins and antioxidant compounds between bread and durum wheat. Higher total proteins, wet gluten and antioxidants contents, combined with lower LOX and POD activities, point to a higher nutritive value of durum wheat than bread wheat. 相似文献
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67.
F. Cajner S. Kovačić H. Rafael A. Vugrinčić V. Šimunović B. Gržeta 《Materialwissenschaft und Werkstofftechnik》2015,46(1):69-77
Nitriding increases surface hardness and improves wear resistance of stainless steels. However, nitriding can sometimes reduce their corrosion resistance. In this paper, the influence of nitriding on the corrosion resistance of martensitic stainless steel was investigated. Plasma nitriding at 440 °C and 525 °C and salt bath nitrocarburizing were carried out on X17CrNi16‐2 stainless steel. Microhardness profiles of the obtained nitrided layers were examined. Phase composition analysis and quantitative depth profile analysis of the nitrided layers were preformed by X‐ray diffraction (XRD) and glow‐discharge optical emission spectrometry (GD‐OES), respectively. Corrosion behaviour was evaluated by immersion test in 1% HCl, salt spray test in 5% NaCl and electrochemical corrosion tests in 3.5% NaCl aqueous solution. Results show that salt bath nitrocarburizing, as well as plasma nitriding at low temperature, increased microhardness without significantly reducing corrosion resistance. Plasma nitriding at a higher temperature increased the corrosion tendency of the X17CrNi16‐2 steel. 相似文献
68.
Effect of CO2 Exposure on the Chemical Stability and Mechanical Properties of BaZrO3‐Ceramics
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Rokas Sažinas Carlos Bernuy‐López Mari‐Ann Einarsrud Tor Grande 《Journal of the American Ceramic Society》2016,99(11):3685-3695
The reactivity of BaZrO3 with CO2 has been addressed as one of the major challenges with BaZrO3‐based electrolytes in protonic ceramic fuel cells. Here, we present a study of the effect of CO2 exposure on BaZrO3‐materials at elevated temperatures. Dense BaZr1?xYxO3?x/2 (x = 0, 0.05, 0.1, 0.2) and BaCe0.2Zr0.7Y0.1O2.95 ceramics were prepared by sintering of powder prepared by spray pyrolysis. The Vickers indentation method was used to determine the hardness and estimate the fracture toughness of pristine materials as well as the corresponding materials exposed to CO2. Formation of BaCO3 on the surface of exposed ceramics was confirmed by X‐ray diffraction and electron microcopy. The reaction resulted in formation of Ba‐deficient perovskite at the exposed surface. The reaction with CO2 was most pronounced at 650°C compared to the other temperatures applied in the study. The reactivity was also shown to depend on the Y‐content and the grain size and was most pronounced for BaZr0.9Y0.1O2.95. The reaction with CO2 was observed to have a profound effect on the fracture toughness of the ceramics, demonstrating a depression of the mechanical stability of the materials. The results are discussed with respect to the chemical and mechanical stability of BaZrO3 materials, with particular emphasis on the composition and grain size. 相似文献
69.
Živec Tina Anžur Andreja Verbovšek Timotej 《Bulletin of Engineering Geology and the Environment》2019,78(3):1631-1643
Bulletin of Engineering Geology and the Environment - Terrestrial laser scanning (TLS) was performed in tectonically undisturbed flysch in the Elerji quarry (south-west Slovenia), which represents... 相似文献
70.
Andreja Žužić Filip Car Jelena Macan Vesna Tomašić Andreja Gajović 《International Journal of Applied Ceramic Technology》2022,19(5):2891-2904
Strontium-doped lanthanum manganites, La1-xSrxMnO3 (LSMO), are promising and affordable catalysts for oxidative degradation of volatile organic compounds. LSMO catalysts (x = 0, .1, .2, and .3) were prepared by the citrate-nitrate autocombustion (CNA) and coprecipitation synthesis. The phase composition was confirmed by X-ray diffraction and Rietveld refinement analysis, while the oxygen content was determined by Mohr's salt permanganate titration. Morphology and porosity of prepared catalysts was correlated to catalytic oxidation of benzene, toluene, ethylbenzene and o-xylene. It was observed that both synthesis methods yielded catalysts of similar average pore size diameter and specific surface area, but the pore size distribution differed: CNA-prepared catalysts had a multimodal pore size distribution, while the coprecipitated ones had a single maximum at 4 nm. Catalysts prepared by the CNA method have shown a higher catalytic activity in the temperature range 373–723 K, as the presence of Mn3+/Mn4+ mixed valences increased their reducibility. 相似文献