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排序方式: 共有816条查询结果,搜索用时 140 毫秒
1.
Nils Hallbäck Fred Nilsson 《Fatigue & Fracture of Engineering Materials & Structures》1992,15(2):173-185
The fracture assessment of structures subjected to secondary loading systems was studied by FEM-analysis of a few illustrative two-dimensional examples. The first example is an edge-cracked plate with a thermal gradient. The FEM-calculations revealed that a purely elastic analysis yielded J-values that are in most cases considerably more conservative than the ones calculated from an elastic-plastic analysis. The results were further compared with different engineering type non-linear estimates. As a second example a crack emanating from a semi-circular notch in a rectangular plate was chosen. The plate was subjected to uniaxial tension along its boundaries. It turned out that for the cases considered the J-values were fairly close to those elastically predicted. 相似文献
2.
3.
Wang Jie Shen XuHui Yang YanYan Zeren ZhiMa Hulot Gauthier Olsen Nils Zhou Bin Magnes Werner De Santis Angelo Huang JianPing Guo Feng Liu WenLong Yu JingBo 《中国科学:技术科学(英文版)》2021,64(5):1118-1126
Science China Technological Sciences - The China Seismo-Electromagnetic Satellite (CSES), China’s first satellite to measure geophysical fields with scientific goals in both space and solid... 相似文献
4.
Oliver Schmutzler Sebastian Graf Nils Behm Wael Y. Mansour Florian Blumendorf Theresa Staufer Christian Krnig Dina Salah Yanan Kang Jan N. Peters Yang Liu Neus Feliu Wolfgang J. Parak Anja Burkhardt Elisabetta Gargioni Sabrina Gennis Sharah Chandralingam Finn Heg Wolfgang Maison Kai Rothkamm Florian Schulz Florian Grüner 《International journal of molecular sciences》2021,22(7)
Quantitative cellular in vitro nanoparticle uptake measurements are possible with a large number of different techniques, however, all have their respective restrictions. Here, we demonstrate the application of synchrotron-based X-ray fluorescence imaging (XFI) on prostate tumor cells, which have internalized differently functionalized gold nanoparticles. Total nanoparticle uptake on the order of a few hundred picograms could be conveniently observed with microsamples consisting of only a few hundreds of cells. A comparison with mass spectroscopy quantification is provided, experimental results are both supported and sensitivity limits of this XFI approach extrapolated by Monte-Carlo simulations, yielding a minimum detectable nanoparticle mass of just 5 pg. This study demonstrates the high sensitivity level of XFI, allowing non-destructive uptake measurements with very small microsamples within just seconds of irradiation time. 相似文献
5.
The oxidation of acetaldehyde on carbon supported Pt/Vulcan, PtRu/Vulcan and Pt3Sn/Vulcan nanoparticle catalysts and, for comparison, on polycrystalline Pt and on an unsupported PtRu0.2 catalyst, was investigated under continuous reaction and continuous electrolyte flow conditions, employing electrochemical and quantitative differential electrochemical mass spectroscopy (DEMS) measurements. Product distribution and the effects of reaction potential and reactant concentration were investigated by potentiodynamic and potentiostatic measurements. Reaction transients, following both the Faradaic current as well as the CO2 related mass spectrometric intensity, revealed a very small current efficiency for CO2 formation of a few percent for 0.1 m acetaldehyde bulk oxidation under steady-state conditions on all three catalysts, the dominant oxidation product being acetic acid. Pt alloy catalysts showed a higher activity than Pt/Vulcan at lower potential (0.51 V), but do not lead to a better selectivity for complete oxidation to CO2. C–C bond breaking is rate limiting for complete oxidation at potentials with significant oxidation rates for all three catalysts. The data agree with a parallel pathway reaction mechanism, with formation and subsequent oxidation of COad and CH
x, ad species in the one pathway and partial oxidation to acetic acid in the other pathway, with the latter pathway being, by far, dominant under present reaction conditions. 相似文献
6.
Phase Stability of Fine-Grained (Mg,Y)-PSZ 总被引:2,自引:0,他引:2
Frank Meschke Nils Claussen Goffredo De Portu Jürgen Rödel 《Journal of the American Ceramic Society》1995,78(7):1997-1999
A fine-grained zirconia, which has been costabilized with yttria and magnesia, has been prepared. Its stability during subeutectoid annealing at 1100deg; C, and its hydrothermal stability during hydrothermal treatment at 180deg; C, have been determined and they are compared to those of Y-TZP and Mg-PSZ materials . 相似文献
7.
The purpose of this investigation was to study the origin of the differences in paper‐to‐paper friction of linerboards based on old corrugated containers (OCC). The sheets were subjected to two extraction stages and analyzed with respect to, surface roughness, and their content of low‐molecular‐mass lipophilic compounds (LLC). Friction was measured using a friction tester based on the horizontal plane principle. The surface roughness was measured using a Perthometer profiler and the low molecular mass lipophilic constituent of the paper sheets was determined by gas chromatography‐mass spectroscopy. The sheets were imaged using environmental scanning electron microscopy (ESEM), and the relative compositions of inorganic ions on the paper surfaces were determined by energy dispersive X‐ray spectroscopy (EDS). The results showed that a high amount of LLC in the sheets lead to low friction, due to lubrication. It was also observed that large CaCO3 particles on the surface had a friction‐increasing effect, and that there was no relationship between the surface roughness and the friction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1511–1520, 2002 相似文献
8.
Alternating-time temporal logic (ATL) is a modal logic that allows to reason about agents’ abilities in game-like scenarios. Semantic variants of ATL are usually built upon different assumptions about the kind of game that is played, including capabilities of agents (perfect vs. imperfect information, perfect vs. imperfect memory, etc.). ATL has been studied extensively in previous years; however, most of the research focused on model checking. Studies of other decision problems (e.g., satisfiability) and formal meta-properties of the logic (like axiomatization or expressivity) have been relatively scarce, and mostly limited to the basic variant of ATL where agents possess perfect information and perfect memory. In particular, a comparison between different semantic variants of the logic is largely left untouched. In this paper, we show that different semantics of ability in ATL give rise to different validity sets. The issue is important for several reasons. First, many logicians identify a logic with its set of true sentences. As a consequence, we prove that different notions of ability induce different strategic logics. Secondly, we show that different concepts of ability induce different general properties of games. Thirdly, the study can be seen as the first systematic step towards satisfiability-checking algorithms for ATL with imperfect information. We introduce sophisticated unfoldings of models and prove invariance results that are an important technical contribution to formal analysis of strategic logics. 相似文献
9.
L. Colmenares E. Guerrini Z. Jusys K. S. Nagabhushana E. Dinjus S. Behrens W. Habicht H. Bönnemann R. J. Behm 《Journal of Applied Electrochemistry》2007,37(12):1413-1427
The activity, selectivity, and methanol tolerance of novel, carbon supported high-metal loading (40 wt.%) Pt/C and Pt3Me/C (Me = Ni, Co) catalysts for the O2 reduction reaction (ORR) were evaluated in model studies under defined mass transport and diffusion conditions, by rotating
(ring) disk and by differential electrochemical mass spectrometry. The catalysts were synthesized by the organometallic route,
via deposition of pre-formed Pt and Pt3Me pre-cursors followed by their decomposition into metal nanoparticles. Characteristic properties such as particle sizes,
particle composition and phase formation, and active surface area, were determined by transmission electron microscopy, energy
dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. For comparison, commercial Pt/C catalysts
(20 and 40 wt.%, E-Tek, Somerset, NJ, USA) were investigated as well, allowing to evaluate Pt loading effects and, by comparison
with the pre-cursor-based catalyst with their much smaller particle sizes (1.7 nm diameter), also particle size effects. Kinetic
parameters for the ORR were evaluated; the ORR activities of the bimetallic catalysts and of the synthesized Pt/C catalyst
were comparable and similar to that of the high-loading commercial Pt/C catalyst; at typical cathode operation potentials
H2O2 formation is negligible for the synthesized catalysts. Due to their lower methanol oxidation activity the bimetallic catalysts
show an improved methanol tolerance compared to the commercial Pt/C catalysts. The results indicate that the use of very small
particle sizes is a possible way to achieve reasonably good ORR activities at an improved methanol tolerance at DMFC cathode
relevant conditions. 相似文献
10.
Novel carbon supported Pt/SnOx/C catalysts with Pt:Sn atomic ratios of 5:5, 6:4, 7:3 and 8:2 were prepared by a modified polyol method and characterized with respect to their structural properties (X-ray diffraction (XRD) and transmission electron microscopy (TEM)), chemical composition (XPS), their electrochemical properties (base voltammetry, COad stripping) and their electrocatalytic activity and selectivity for ethanol oxidation (ethanol oxidation reaction (EOR)). The data show that the Pt/SnOx/C catalysts are composed of Pt and tin oxide nanoparticles with an average Pt particle diameter of about 2 nm. The steady-state activity of the Pt/SnOx/C catalysts towards the EOR decreases with tin content at room temperature, but increases at 80 °C. On all Pt/SnOx/C catalysts, acetic acid and acetaldehyde represent dominant products, CO2 formation contributes 1-3% for both potentiostatic and potentiodynamic reaction conditions. With increasing potential, the acetaldehyde yield decreases and the acetic acid yield increases. The apparent activation energies of the EOR increase with tin content (19-29 kJ mol−1), but are lower than on Pt/C (32 kJ mol−1). The somewhat better performance of the Pt/SnOx/C catalysts compared to alloyed PtSnx/C catalysts is attributed to the presence of both sufficiently large Pt ensembles for ethanol dehydrogenation and C-C bond splitting and of tin oxide for OH generation. Fuel cell measurements performed for comparison largely confirm the results obtained in model studies. 相似文献