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排序方式: 共有179条查询结果,搜索用时 2 毫秒
1.
2.
Efimia K. Dermesonlouoglou Varvara Andreou Zacharias Alexandrakis George J. Katsaros Maria C. Giannakourou Petros S. Taoukis 《International Journal of Food Science & Technology》2017,52(4):916-926
Tomatoes are perishable products due to the activity of microorganisms and endogenous enzymes. The objective was to produce cut tomatoes with extended shelf life, using the combined hurdle effect of osmotic pretreatment (OD) and high pressure (HP), instead of a conventional one‐step thermal process. Samples were processed in a multicomponent osmotic solution at 35 °C, subsequently cold‐pasteurised in pack at 600 MPa and stored at 5–15 °C. Quality deterioration during isothermal and nonisothermal storage was kinetically modelled. Both OD process and OD‐HP combined process caused an increase in lycopene content that was well retained. Texture, colour and flavour of treated samples were evaluated as similar to fresh, with OD‐HP samples showing better retention during storage. Being microbiologically stable, shelf life of OD‐HP samples was limited by sensory deterioration, whereas OD samples were rejected due to eventual microbial growth. Shelf life of OD and OD‐HP samples was estimated at 77 and 181 days, respectively, at 5 °C. 相似文献
3.
In 2006, our group reported the fabrication of ultra-long single-crystal ZnAl2O4 spinel nanotubes, starting from ZnO/Al2O3 core–shell nanowires, involving the nanoscale Kirkendall effect. In this feature paper, we introduce our up-to-date results on the design of porous and hollow 1D nanostructures following this solid-state interfacial reaction route. In particular, we present our recent understandings on void evolution induced by the unbalanced diffusion. We first give a short introduction on the distinctions of core–shell nanowires in interfacial nanoreactions, in contrast to other systems. Then we discuss the roles of desorption, stress, and/or defects on void evolution and nanotube formation. Our results demonstrate that the stress- and defects-engineered diffusion mechanism can be used to specifically design hollow nanostructures, which will open up a new window in exploitation of the Kirkendall effect at the nanoscale. 相似文献
4.
R. D. Morales J. Palafox-Ramos J. de J. Barreto S. Lopez-Ramirez D. Zacharias 《Metallurgical and Materials Transactions B》2000,31(6):1505-1515
Water modeling and mathematical simulation techniques were used to study the melt flow under the influence of turbulence inhibitors
in a multistrand bloom caster tundish. Three different cases were studied: a bare tundish (BT), a tundish with two pairs of
baffles and a waved impact pad (BWIP), and a tundish equipped with turbulence inhibitor and a pair of dams (TI&D). Chemical
mixing of tracer turbulence diffusion was also simulated and compared with actual experimental results. The TI&D arrangement
showed an improvement of the fluid flow characteristics, yielding better tracer distribution among the outlets, lower values
of back mixing flow, and higher values of plug flow. A mass transfer model coupled with k-ɛ turbulence model predicted acceptably well the experimental chemical mixing of the tracer in the water model. The water modeling
and the numerical simulation indicated that the TI&D arrangement retains the tracer inside the vessel for longer times, increasing
the minimum residence time. These results encourage the use of turbulence-inhibiting devices in bloom and billet casters,
which pursue excellence in product quality. 相似文献
5.
The calculation and study of transient phenomena occurring when a photovoltaic (PV) source is applied to RLC circuits are presented in this paper. The method of approach adopted is based on an incremental model of the photovoltaic generator as opposed to the usual numerical integration algorithm for the solution of the governing non-linear differential equations. Such an approach is of particular advantage in many respects. On the quantitative basis, it ensures both accuracy and numerical stability even if a large time step is used. On the qualitative basis, it gives the ability to have a better insight into the response evolution and visualizes the effects that the various parameters may have on the nature of the transient response. Finally, it reveals some interesting and useful features about the transient behavior of a passive load driven by a PV generator, so that conclusions from the engineering viewpoint can be drawn. 相似文献
6.
Ultrasmall silicon (Si) nanoelectronic devices require an energy shift of electronic states for n‐ and p‐conductivity. Nanocrystal self‐purification and out‐diffusion in field effect transistors cause doping to fail. Here, it is shown that silicon dioxide (SiO2) and silicon nitride (Si3N4) create energy offsets of electronic states in embedded Si quantum dots (QDs) in analogy to doping. Density functional theory (DFT), interface charge transfer (ICT), and experimental verifications arrive at the same size of QDs below which the dielectric dominates their electronic properties. Large positive energy offsets of electronic states and an energy gap increase exist for Si QDs in Si3N4 versus SiO2. Using DFT results, the SiO2/QD interface coverage is estimated with nitrogen (N) to be 0.1 to 0.5 monolayers (ML) for samples annealed in N2 versus argon (Ar). The interface impact is described as nanoscopic field effect and propose the energy offset as robust and controllable alternative to impurity doping of Si nanostructures. 相似文献
7.
V. Bykov F. Schauer K. Egorov P. van Eeten J. Fellinger M. Sochor N. Jaksic A. Tereshchenko A. Dudek D. Zacharias D. Hathiramani P. Czarkowski Q. Yang T. Bergmann S. Freundt 《Fusion Engineering and Design》2011,86(6-8):645-650
The Wendelstein 7-X (W7-X) modular stellarator is in the assembly phase at the Max-Planck-Institut für Plasmaphysik in Greifswald, Germany. The design of the “basic machine”, i.e. without in-vessel components, diagnostics and periphery, is largely completed, structural parameters such as bolt preload, initial conditions for contact elements, etc. are defined, and most of the components are manufactured and partly assembled. Therefore, the focus of structural analysis was shifted towards fast analyses of non-conformities, changes in the assembly procedure, and exploration of operational limits. Assembly-related work is expected to continue until commissioning of the machine, however, with decreasing intensity. In parallel the analysis requirements for in-vessel components, diagnostics and periphery will increase.This paper focuses on the most remarkable results, on special problems which had to be solved, on strategic issues like parameterization, complex finite element model structuring and benchmarking with alternative models in different codes, on assumptions of reasonable safety margins and expected tolerances, and on confirmation of analysis results by tests. Finally it highlights some lessons learned so far, which might be relevant also for other large fusion machines, and gives an outlook on future work. 相似文献
8.
We report the influence of an Al(2)O(3) shell on the photoluminescence emission of ZnO nanowires. At room temperature, the spectrum of the core-shell nanowires shows a strong reduction of the relative intensity of the green defect emission with respect to the near-band-edge emission. At 5?K an increase of the relative intensity of the surface exciton band with respect to the donor-bound exciton emission is observed. Annealing the core-shell nanowires at 500?°C does not increase the green defect luminescence at 5?K. We propose a model explaining the spectral changes. 相似文献
9.
10.
Bi-Sr-Ca-Cu-O glasses and glass ceramics of various compositions were synthesised. The glass transition temperature varies
from 396 to 422°C depending on the glass composition. The bulk glass ceramics of 4334, 4336, 2223 and 4246 compositions show
superconductivity when the corresponding glass samples were heat-treated in air at 820°C for 3, 9, 12 and 24 h respectively.
X-ray diffraction studies show that the superconducting phase present in all these compositions is Bi2Sr2Ca1Cu2O
x
. The 4334 glass ceramic is almost a single-phase material with a preferred orientation such that thec axis is normal to the sample surface. The 2223 glass ceramic has a higherT
c (onset) than the other three compositions indicating the presence of highT
c phase (110K) also. ESR studies on the glass samples indicate the existence of Cu2+. The effect of heat treatment on ESR shows that the intensity of resonance decreases with increase in heat-treatment duration.
This effect is more pronounced for the 4334 and 2223 compositions. The advantages of synthesizing superconducting materials
by glass route are discussed in view of practical applications. 相似文献