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排序方式: 共有294条查询结果,搜索用时 15 毫秒
71.
Dirk Zahn Oliver Hochrein Gotthard Seifert Rüdiger Kniep 《Science and Technology of Advanced Materials》2007,8(5):434-441
The investigation of the atomistic mechanisms of processes in complex systems constitutes a major challenge to both theory and experiment. While experimental studies offer a wide variety of insights at the macroscopic scale, the atomistic level of detail often remains elusive. On the other hand, molecular simulation approaches may easily achieve microscopic resolution and hence appear particularly suited for detailed mechanistic analyses. However, the computational effort is typically quite considerable and in many cases special simulation strategies are needed to make simulations possible. This review is dedicated to special approaches for tackling the time/length-scale problem inherent to molecular dynamics simulations. Employing these techniques opened a series of new perspectives. The latter are illustrated with the example of recent simulation studies of the atomistic mechanisms involved in complex processes like crystal nucleation, phase transitions and reactions in solution. Along this line, we discuss the reaction mechanisms for He insertion into C60 fullerenes, nucleation events and domain morphogenesis in pressure-induced phase transitions in solids and ion aggregation from solution. 相似文献
72.
73.
D. G. Kipshidze H. P. Schenk A. Fissel U. Kaiser J. Schulze Wo. Richter M. Weihnacht R. Kunze J. Kräusslich 《Semiconductors》1999,33(11):1241-1246
The results of using molecular-beam epitaxy for growing piezoelectric AlN films on Si (111) substrates suitable for device
applications are reported. The technological conditions for growth of stoichiometric AlN by controlling the surface reconstruction
occurring under various thermodynamic conditions on the growth surface are determined. The films of the hexagonal polytype
of AlN possess high crystalline perfection and an atomically smooth epitaxial surface. The mechanism for relaxation of the
AlN crystal lattice over a distance of one monolayer from the heterojunction is found. It is demonstrated that the AlN film
is piezoelectric. Investigations of the temporal characteristics of a SAW attest to a low level of scattering of the wave
during propagation. The electromechanical coupling constant is measured in interdigital transducer geometry (λ=16 mm) and
is found to be 0.07 % at a frequency f=286 MHz, in good agreement with the theoretical value for a 1.04-μm-thick AlN film.
Fiz. Tekh. Poluprovodn. 33, 1372–1378 (November 1999) 相似文献
74.
Blastobotrys adeninivorans (syn. Arxula adeninivorans) is a non‐conventional, non‐pathogenic, imperfect, haploid yeast, belonging to the subphylum Saccharomycotina, which has to date received comparatively little attention from researchers. It possesses unusual properties such as thermo‐ and osmotolerance, and a broad substrate spectrum. Depending on the cultivation temperature B. (A.) adeninivorans exhibits different morphological forms and various post‐translational modifications and protein expression properties that are strongly correlated with the morphology. The genome has been completely sequenced and, in addition, there is a well‐developed transformation/expression platform, which makes rapid, simple gene manipulations possible. This yeast species is a very good host for homologous and heterologous gene expression and is also a useful gene donor. Blastobotrys (A.) adeninivorans is able to use a very wide range of substrates as carbon and/or nitrogen sources and is an interesting organism owing to the presence of many metabolic pathways, for example degradation of n‐butanol, purines and tannin. In addition, its unusual properties and robustness make it a useful bio‐component for whole cell biosensors. There are currently a number of products on the market produced by B. (A.) adeninivorans and further investigation may contribute further innovative solutions for current challenges that exist in the biotechnology industry. Additionally it may become a useful alternative to existing commercial yeast strains and as a model organism in research. In this review we present information relevant to the exploitation of B. (A.) adeninivorans in research and industrial settings. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
75.
In this paper we investigate the influence of material and device properties on the ballistic transport in epitaxial monolayer graphene and epitaxial quasi-free-standing monolayer graphene. Our studies comprise (a)?magneto-transport in two-dimensional (2D) Hall bars, (b)?temperature- and magnetic-field-dependent bend resistance of unaligned and step-edge-aligned orthogonal cross junctions, and (c)?the influence of the lead width of the cross junctions on ballistic transport. We found that ballistic transport is highly sensitive to scattering at the step edges of the silicon carbide substrate. A suppression of the ballistic transport is observed if the lead width of the cross junction is reduced from 50?nm to 30?nm. In a 50?nm wide device prepared on quasi-free-standing graphene we observe a gradual transition from the ballistic into the diffusive transport regime if the temperature is increased from 4.2 to about 50?K, although 2D Hall bars show a temperature-independent mobility. Thus, in 1D devices additional temperature-dependent scattering mechanisms play a pivotal role. 相似文献
76.
77.
Annegret Potthoff Robert Kratzsch Maria Barbosa Nick Kulissa Oliver Kunze Filofteia-Laura Toma 《Journal of Thermal Spray Technology》2018,27(4):710-717
Compositions in the system Cr2O3-TiO2-Al2O3 are among the most used ceramic materials for thermally sprayed coating solutions. Cr2O3 coatings present good sliding wear resistance; Al2O3 coatings show excellent insulation behavior and TiO2 striking corrosion properties. In order to combine these properties, coatings containing more than one oxide are highly interesting. The conventional spraying process is limited to the availability of binary feedstock powders with defined compositions. The use of suspensions offers the opportunity for tailor-made chemical compositions: within the triangle of Cr2O3-TiO2-Al2O3, each mixture of oxides can be created. Criteria for the selection of raw materials as well as the relevant aspects for the development of binary suspensions in the Cr2O3-TiO2-Al2O3 system to be used as feedstock for thermal spraying are presented. This formulation of binary suspensions required the development of water-based single-oxide suspensions with suitable behavior; otherwise, the interaction between the particles while mixing could lead up to a formation of agglomerates, which affect both the stability of the spray process and the coating properties. For the validation of this formulation procedure, binary Cr2O3-TiO2 and Al2O3-TiO2 suspensions were developed and sprayed using the S-HVOF process. The binary coatings were characterized and discussed in terms of microstructure and microhardness. 相似文献
78.
Johannes Paul Schoß Eric Schramm Paul Schönherr Natalia Maria Mrowka Helge Schumann Hanka Becker Andreas Keßler Michal Szucki Gotthard Wolf 《Advanced Engineering Materials》2023,25(9):2201576
The formation of iron (Fe)-containing intermetallics during solidification is challenging due to the influences of cooling rate and chemical composition. Differential scanning calorimetry (DSC) is an accurate analysis method but merely replicates adjustable cooling conditions. Thereby, the solidification range is traversed several times before DSC measurement. For this purpose, thermal analysis cooling curves with double thermocouple are conducted to investigate the formation temperature of Fe-rich intermetallics in different AlSi casting alloys. In addition, the influence of chemical composition is examined by increasing the initial contents of iron, manganese, and chromium to 0.8 wt% each. The double thermocouple setup allows determining feeding points and solid fractions of the alloy compounds. To evaluate the data sets, the statistical program R is used to improve data processing and smoothing. The signature of Fe-rich intermetallics in the temperature–time plots corresponds to the detected phases in optical micrographs. In addition, scanning electron microscopy with energy-dispersive spectroscopy and electron backscattering diffraction are used to measure the local chemical composition and identify the iron-rich intermetallics. Real-time evaluation (differential calculation, first derivative, incl. smoothing) for an applicable filtration process can be performed using thermocouples with analog-to-digital converter and Python programs with an interactive graphical interface. 相似文献
79.
80.
Kaiyue Jiang Igor A. Baburin Peng Han Chongqing Yang Xiaobin Fu Yefeng Yao Jiantong Li Enrique Cnovas Gotthard Seifert Jiesheng Chen Mischa Bonn Xinliang Feng Xiaodong Zhuang 《Advanced functional materials》2020,30(7)
2D soft nanomaterials are an emerging research field due to their versatile chemical structures, easily tunable properties, and broad application potential. In this study, a benzene‐bridged polypyrrole film with a large area, up to a few square centimeters, is synthesized through an interfacial polymerization approach. As‐prepared semiconductive films exhibit a bandgap of ≈2 eV and a carrier mobility of ≈1.5 cm2 V?1 s?1, inferred from time‐resolved terahertz spectroscopy. The samples are employed to fabricate in‐plane micro‐supercapacitors (MSCs) by laser scribing and exhibit an ultrahigh areal capacitance of 0.95 mF cm?2, using 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([EMIM][BF4]) as an electrolyte. Importantly, the maximum energy and power densities of the developed MSCs reach values up to 50.7 mWh cm?3 and 9.6 kW cm?3, respectively; the performance surpassing most of the 2D material‐based MSCs is reported to date. 相似文献