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排序方式: 共有467条查询结果,搜索用时 234 毫秒
101.
Patrizia Frontera Angela Malara Vincenza Modafferi Vincenzo Antonucci Pierluigi Antonucci Anastasia Macario 《加拿大化工杂志》2020,98(9):1924-1934
This work deals with the catalytic performance of nickel-cobalt supported on ceria-doped gadolinia (GDC) catalyst in the single and in the simultaneous methanation of carbon monoxide and carbon dioxide. The catalysts have been prepared by impregnation method, starting from metal salts precursors. Samples have been characterized by x-ray diffraction (XRD), thermogravimetric analysis and differential scanning calorimetry (TGA-DSC), hydrogen temperature programmed reduction (TPR-H2), transmission electronic microscopy (TEM), and scanning electron microscopy (SEM/EDX) technique. The temperature examined for methanation tests ranged from 200°C-600°C. The results show that the prepared and optimized catalysts possess the main characteristics of materials suitable for SOECs (solid oxide electrolyzer cells) applications: high metal content (50% wt/wt with respect to the support), high activity, and high stability. The catalytic performance of bimetallic catalysts highlights that the cobalt does not improve the activity of the nickel catalysts. 相似文献
102.
Boris A. Katsnelson Ivan N. Chernyshov Svetlana N. Solovyeva Ilzira A. Minigalieva Vladimir B. Gurvich Irene E. Valamina Oleg H. Makeyev Renata R. Sahautdinova Larisa I. Privalova Anastasia E. Tsaregorodtseva Artem V. Korotkov Eugene A. Shuman Vladimir G. Panov Marina P. Sutunkova 《International journal of molecular sciences》2021,22(1)
Rats were exposed to nickel oxide nano-aerosol at a concentration of 2.4 ± 0.4 µg/m3 in a “nose only” inhalation setup for 4 h at a time, 5 times a week, during an overall period of 2 weeks to 6 months. Based on the majority of the effects assessed, this kind of exposure may be considered as close to LOAEL (lowest observed adverse effect level), or even to NOAEL (no observed adverse effect level). At the same time, the experiment revealed genotoxic and allergic effects as early as in the first weeks of exposure, suggesting that these effects may have no threshold at all. 相似文献
103.
Anastasia Houndri Stelios Polymenis Yannis Chryssoulakis Dimitris Pantelis 《Metallurgical and Materials Transactions A》1992,23(6):1801-1806
Microstructure improvements of a nickel electrodeposited Al−Si alloy were studied after high-power laser melting treatment
through a single pass or partially overlapping successive adjacent passes. In some cases, laser melting treatment was preceded
by a 5-hour heating of the specimens at 500°C in argon atmosphere furnace. Microstructure observations and microhardness measurements
were carried out on the specimens before and after laser melting treatment with and without preheating. Best results concerning
microhardness, microstructural homogeneity, and porosity elimination, as well as adhesion of the nickel coating on the Al−Si
alloy, were achieved when the specimens were first subjected to heating at 500°C in an argon atmosphere furnace for 5 hours
and then submitted to a laser melting treatment through successive adjacent laser passes with an overlapping rate of 70 pct.
Microstructure studies were carried out employing X-ray diffraction analysis (XRD) and energy-dispersive spectrometry (EDS).
AlNi and Al3Ni phases were detected in the diffusion area which resulted from the 5-hour heating. AlNi, Al3Ni, and Al3Ni2 phases were identified in the laser melted zones (LMZs). Each one of the above phase was found to be the main phase under
different conditions. 相似文献
104.
High Stiffness Cellulose Fibers from Low Molecular Weight Microcrystalline Cellulose Solutions Using DMSO as Co‐Solvent with Ionic Liquid 下载免费PDF全文
Chenchen Zhu Anastasia F. Koutsomitopoulou Stephen J. Eichhorn Jeroen S. van Duijneveldt Robert M. Richardson Rinat Nigmatullin Kevin D. Potter 《大分子材料与工程》2018,303(5)
There is a need to develop high‐performance cellulose fibers as sustainable replacements for glass fibers, and as alternative precursors for carbon filaments. Traditional fiber spinning uses toxic solvents, but in this study, by using dimethyl sulfoxide (DMSO) as a co‐solvent with an ionic liquid, a novel high‐performance fiber with exceptional mechanical properties is produced. This involves a one‐step dissolution, and cost‐effective route to convert high concentrations of low molecular weight microcrystalline cellulose into high stiffness cellulose fibers. As the cellulose concentration increases from 20.8 to 23.6 wt%, strong optically anisotropic patterns appear for cellulose solutions, and the clearing temperature (T c) increases from ≈100 °C to above 105 °C. Highly aligned, stiff cellulose fibers are dry‐jet wet spun from 20.8 and 23.6 wt% cellulose/1‐ethyl‐3‐methylimidazolium diethyl phosphate/DMSO solutions, with a Young's modulus of up to ≈41 GPa. The significant alignment of cellulose chains along the fiber axis is confirmed by scanning electron microscopy, wide‐angle X‐ray diffraction, and powder X‐ray diffraction. This process presents a new route to convert high concentrations of low molecular weight cellulose into high stiffness fibers, while significantly reducing the processing time and cost. 相似文献
105.
Premixed conical CH4-air flames were studied experimentally and numerically under normal straight, reversed gravity conditions and microgravity. Low-gravity experiments were performed in Drop tower. Classical Bunsen-type burner was used to find out features of gravity influence on the combustion processes. Mixture equivalence ratio was varied from 0.8 to 1.3. Wide range of flow velocity allows to study both laminar and weakly turbulized flames. High-speed flame chemoluminescence video-recording was used as diagnostic. The investigations were performed at atmospheric pressure. As results normalized flame height, laminar flame speed were measured, also features of flame instabilities were shown. Low- and high-frequency flame-instabilities (oscillations) have a various nature as velocity fluctuations, preferential diffusion instability, hydrodynamic and Rayleigh-Taylor ones etc., that was explored and demonstrated. 相似文献
106.
107.
Near Room‐Temperature Memory Devices Based on Hybrid Spin‐Crossover@SiO2 Nanoparticles Coupled to Single‐Layer Graphene Nanoelectrodes 下载免费PDF全文
108.
Daniela Pfister Konrad Schäfer Claudia Ott Birgit Gerke Rainer Pöttgen Oliver Janka Maximilian Baumgartner Anastasia Efimova Andrea Hohmann Peer Schmidt Sabarinathan Venkatachalam Leo van Wüllen Ulrich Schürmann Lorenz Kienle Viola Duppel Eric Parzinger Bastian Miller Jonathan Becker Alexander Holleitner Richard Weihrich Tom Nilges 《Advanced materials (Deerfield Beach, Fla.)》2016,28(44):9782-9782
109.
Theodora Tsikrika Anastasia Moumtzidou Stefanos Vrochidis Ioannis Kompatsiaris 《Multimedia Tools and Applications》2016,75(3):1563-1587
Focussed crawlers enable the automatic discovery of Web resources about a given topic by automatically navigating the Web link structure and selecting the hyperlinks to follow by estimating their relevance to the topic based on evidence obtained from the already downloaded pages. This work proposes a classifier-guided focussed crawling approach that estimates the relevance of a hyperlink to an unvisited Web resource based on the combination of textual evidence representing its local context, namely the textual content appearing in its vicinity in the parent page, with visual evidence associated with its global context, namely the presence of images relevant to the topic within the parent page. The proposed focussed crawling approach is applied towards the discovery of environmental Web resources that provide air quality measurements and forecasts, since such measurements (and particularly the forecasts) are not only provided in textual form, but are also commonly encoded as multimedia, mainly in the form of heatmaps. Our evaluation experiments indicate the effectiveness of incorporating visual evidence in the link selection process applied by the focussed crawler over the use of textual features alone, particularly in conjunction with hyperlink exploration strategies that allow for the discovery of highly relevant pages that lie behind apparently irrelevant ones. 相似文献
110.
Danica Porobic Ippokratis Pandis Miguel Branco Pınar Tözün Anastasia Ailamaki 《The VLDB Journal The International Journal on Very Large Data Bases》2016,25(5):625-650
Modern hardware is abundantly parallel and increasingly heterogeneous. The numerous processing cores have non-uniform access latencies to the main memory and processor caches, which causes variability in the communication costs. Unfortunately, database systems mostly assume that all processing cores are the same and that microarchitecture differences are not significant enough to appear in critical database execution paths. As we demonstrate in this paper, however, non-uniform core topology does appear in the critical path and conventional database architectures achieve suboptimal and even worse, unpredictable performance. We perform a detailed performance analysis of OLTP deployments in servers with multiple cores per CPU (multicore) and multiple CPUs per server (multisocket). We compare different database deployment strategies where we vary the number and size of independent database instances running on a single server, from a single shared-everything instance to fine-grained shared-nothing configurations. We quantify the impact of non-uniform hardware on various deployments by (a) examining how efficiently each deployment uses the available hardware resources and (b) measuring the impact of distributed transactions and skewed requests on different workloads. We show that no strategy is optimal for all cases and that the best choice depends on the combination of hardware topology and workload characteristics. Finally, we argue that transaction processing systems must be aware of the hardware topology in order to achieve predictably high performance. 相似文献