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1.
Methods of automatic computer analyses of images have large impotence in numerous physical problems with different kinds of radiations, which use such solid-state detectors as nuclear photographic emulsions, plastics and others. We described a method of expanding boundaries of dark areas for such computer analyses of micro-pictures. We demonstrated effectiveness of this method by the example of the search of microcrystals size distributions in two undeveloped nuclear emulsions and similar distribution of background grains in the developed emulsion.  相似文献   
2.
Abstract

An aliphatic ester of hydroxysalicylic acid (6), reported for the first time from a natural source in addition to five known compounds were isolated from the fermented Carica papaya L. preparation, a commercialized functional food. The known compounds were identified as 5-hydroxymethylfurfuraldehyde (1), trans-caffeic acid (2), butyl 4-hydroxybenzoate (butylparaben) (3), lycopene (4), benzyl isothiocyanate (5). Compounds 1 and 3 were reported for the first time from Papaya fruits through this study. The new compound showed a moderate antioxidant activity and a potent hair growth stimulating activity in vitro.  相似文献   
3.
The effect of annealing condition on the microstructure evolution, together with mechanical properties of Fe-28.5Ni steel processed by one and six cycles of accumulative roll bonding (ARB), was explored. The evolution of microstructure was studied by means of Electron Backscattered Diffraction method. The ARB-processed specimens were annealed for 30 minutes between 500°C and 600°C, and the effect of these annealing processes was elaborated. Results showed a significantly reduced martensite phase during ARB process cycles. Moreover, a refined and stabilised ultrafine structure was obtained in 6-cycle ARB-processed specimen. Results also show that by annealing the 1-cycle specimen at 550°C, no significant microstructural change and mechanical properties variation are identified. As such, no significant microstructural change and mechanical properties variation were notified for annealing of 6-cycle ARB-processed specimen at 500°C. However, annealing at 600°C in both conditions led to a complete recrystallisation of the deformed structure. Annealing at 550°C in 6-cycle ARB-processed specimen showed partial recrystallisation as well as an abnormal grain growth characteristic. The abnormal grain growth was seen by annealing of 1-cycle ARB-processed specimen at 600°C. The changing features of dislocations were discussed in these specimens in terms of changing the dynamics of low- and high-angle grain boundaries. Tensile test results also showed a significant increase in the yield/ultimate tensile strengths with the application of ARB cycles. Although ARB process led to a rapid reduction of total elongation, full restoration during high-temperature annealing returned this value back to the initial, non-deformed, condition.  相似文献   
4.
S.P. Gido 《哲学杂志》2013,93(9):771-787
The microstructure of anisotropically shaped grains can strongly influence a range of material properties, including transport, mechanical and electro-optical. A grain-structure-related phenomenon, known as excluded volume epitaxy (EVE), is reported in this study. EVE is a local, inter-grain orientational correlations effect, which results from a combination of continuous nucleation of anisotropic grains and impingement of growing grains. Due to EVE, anisotropically shaped grains have a tendency to be similarly aligned in a local neighbourhood, despite the absence of any forced global orientation in the sample. The effect has been repeatedly observed by the authors in block copolymers, as illustrated by a representative TEM image. Optical microscopy of anisotropically shaped non-polymeric crystals revealed the generality of this effect. The simulation study revealed a tendency for azimuthal, inter-grain orientational correlation and re-confirmed the experimental observation of EVE.  相似文献   
5.
6.
The effect of processing and annealing temperatures on the grain boundary characters in the ultrafine-grained structure of a 304-type austenitic stainless steel was studied. An S304H steel was subjected to multidirectional forging (MDF) at 500–800°C to total strains of ~4, followed by annealing at 800–1,000°C for 30 min. The MDF resulted in the formation of ultrafine-grained microstructures with mean grain sizes of 0.28–0.85 μm depending on the processing temperature. The annealing behaviour of the ultrafine-grained steel was characterized by the development of continuous post-dynamic recrystallization including a rapid recovery followed by a gradual grain growth. The post-dynamically recrystallized grain size depended on both the deformation temperature and the annealing temperature. The recrystallization kinetics was reduced with an increase in the temperature of the preceding deformation. The grain growth during post-dynamic recrystallization was accompanied by an increase in the fraction of Σ3n CSL boundaries, which was defined by a relative change in the grain size, i.e. a ratio of the annealed grain size to that evolved by preceding warm working (D/D0). The fraction of Σ3n CSL boundaries sharply rose to approximately 0.5 in the range of D/D0 from 1 to 5, which can be considered as early stage of continuous post-dynamic recrystallization. Then, the rate of increase in the fraction of Σ3n CSL boundaries slowed down significantly in the range of D/D0 > 5. A fivefold increase in the grain size by annealing is a necessary condition to obtain approximately 50% Σ3n CSL boundaries in the recrystallized microstructure.  相似文献   
7.
Fast (14 MeV) neutrons have been successfully used in investigating the protein content of different food grains (Soya Beans, Sorghum, Maize and Beans) locally grown and consumed in Nigeria. Protein was estimated via nitrogen using the 14N(n, 2n)13N reaction. Quantification of nitrogen was achieved through a γ-γ coincidence counting of 511 keV positron emissions from the decaying 13N. The implication of the use of the emitted annihilation positrons, the interference introduced in the analytical energy spectra from other activated target nuclides present in the sample, as well as possible proton “knock on” reactions anticipated from cellulose in grain matrix were assessed, and their contributions to the 511 keV gamma energy resolved. For comparative purposes, replicates of samples analyzed through Fast Neutron Activation Analysis (FNAA) were investigated using the Kjeldahl method. The samples were carried through the Kjeldahl process of pre-digestion (with appropriate catalysts), digestion and titration. The results obtained through the Kjeldahl process were found to be in good agreement with those obtained using FNAA although slightly lower. Protein content (%) of Nigerian grains analyzed varied from a low 8.75 ± 2.96 for sorghum to 35.93 ± 0.31 for soya beans.  相似文献   
8.
John W. Goodby 《Liquid crystals》2017,44(12-13):1755-1763
ABSTRACT

In this article, the relationship between molecular architecture and the formation of twist-bend phases is reviewed under the context of shape dependency. We conclude that the twist-bend phase is a universal phenomenon, which occurs in a wide variety of materials, for dimers through to main chain polymers. In the process, the chemical information on molecular design is effectively lost or irrelevant, and molecular topology takes precedence over electrostatic interactions in mesophase formation. As a consequence of this macro-scale material, engineering by shape alone becomes a possibility, potentially more phases may be realised, and entropy is anisotropic.  相似文献   
9.
Most studies on granular physics have focused on dry granular media, with no liquids between the grains. However, in geology and many real world applications (e.g. food processing, pharmaceuticals, ceramics, civil engineering, construction, and many industrial applications), liquid is present between the grains. This produces inter-grain cohesion and drastically modifies the mechanical properties of the granular media (e.g. the surface angle can be larger than 90 degrees). Here we present a review of the mechanical properties of wet granular media, with particular emphasis on the effect of cohesion. We also list several open problems that might motivate future studies in this exciting but mostly unexplored field.

Table  相似文献   

10.
We report that nano‐emulsions can be creatively used as a morphology selective synthesis method to prepare not only nano‐grains but also nano‐fibers with high selectivity. Synthesis of the two different morphological materials was demonstrated using polyaniline synthesis as a model case. Polyaniline nano‐grains were synthesized from aniline molecules in nano‐size aqueous droplets as polymerization sites whose droplets were generated by inverse water‐in‐oil nano‐emulsion use, and polyaniline nano‐fibers were synthesized from aniline in aqueous nano‐dimensional channels as polymerization sites whose channels were generated by direct oil‐in‐water nano‐emulsion use containing high population of oil droplets. Using the approaches, we successfully synthesized nano‐fibers of 60 nm diameter with 0.5 µm length and also nano‐grains having diameter of 60–80 nm. The two different polymerization sites of nano‐scale dimension were made by changing the ratio among surfactant, aqueous aniline/HCl solution, and oil, i.e. organic solvent. We found the nano‐fibers synthesized from the channels formed by the direct oil‐in‐water nano‐emulsion have higher bulk electrical conductivity than the nano‐grains which were synthesized from the droplets formed by the inverse water‐in‐oil emulsion. We also found that the emulsion use allows us to use a room temperature synthesis unlike conventional synthesis methods which require to use ice bath temperature. Physical properties of both nano‐fibers and nano‐grains synthesized were characterized by Fourier transform infrared (FTIR), UV–Vis spectra, scanning electron microscopy (SEM), and four probes conductivity measurement. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
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