Search results

Introduction Grain boundaries act generally as diffusion short circuits; consequently, the major part of material transport will occur by grain-boundary diffusion in nanomaterials where a large amount of atoms can lie on grain or interphase boundaries (50% for a grain size equal to 5 nm; 20% for a grain size equal to 10 nm).
It is well known from classical treatments of grain or interface diffusion that there are three different grain-boundary diffusion regimes in coarse grained crystals: type A, B and C.
We will see that there is an increasing number of new experimental evidences that the above diffusion coefficients agree very well with each other, i.e. in most of the cases the structures of relaxed grain-boundaries in nanocrystalline and polycrystalline samples are very similar.
-In A kinetic regime (Dv t)1/2 >> d), the different diffusion zones overlap each other resulting in a macroscopic homogeneous diffusing distribution which appears to obey Fick's laws as for a homogeneous system with an effective diffusion coefficient (Deff) equal to an average of Dv and Db weighted in the ratio of the number of diffusing atoms in the grains to that in GB [6]: Deff = g Db + (1-g) Dv, (2) 4 Title of Publication (to be inserted by the publisher) where g is the grain-boundary volume fraction (g � �/d; the factor of proportionality depends on the grain shape, but is in the order of unity).
In effect, owing to the number of GBs and the synthesis conducted under UHV conditions, the grain boundaries must be purer in the first type of materials if one excepts the contamination during the preparation (specially by oxygen) and supersaturated metastable nanocrystalline solid solutions.

This resulted in an equiaxed grain size of 68 ± 4 µm.
As annealing proceeds the recrystallising grains grow into the non-banded grains.
Discussion From Fig. 2 it appears that nucleation of recrystallisation takes place preferentially at grain boundaries and inside grains with well developed microband structures.
The number of subgrains per unit volume α (δ) -3, and, assuming that the shapes of recrystallised grains and subgrains are the same, means that, from equation (5), the probability of a subgrain forming a nucleus increases somewhat with decreasing subgrain size.
If these were the only sites, one should consider only the number of subgrains impinging on boundaries.

The objective of this work is to discriminate single corn kernel and some broken kernels, which are difficult to achieve on the existing machinery and equipment, especially for the counted number and quality inspection process.
ENg ，W.F.Wilcke used three-layer neural network to research the detection techniques of grain damage and moldy maize grain [2]; in 2008, Shi Zhixing, Cheng Hong etc.
Based on the Matlab environment, through statistical analysis of a large number of corn kernels image, we can extracted a threshold of Area from the image [7].
Type 0 for broken kernel, 1 full grain, large amounts of data were normalized to train the model.
It was concluded that this may be used for variety and quality testing equipment for masses of grain.

The total number of grains of 5 grain boundary in whole mapping is 8869 with I AGG grain.
Number of grains included in misorientation calculation seems to be enough to obtain statistics.
Typical and reliable equipment obtaining orientation information is Transmission Electron Microscope(TEM), of which reasonably and practically measurable number of grains is below one hundred.
EBSD mapping and Montage technique used in this study can increase the measurable grain number of statistical data about hundred thousand, which is thousand times larger than TEM.
Large number of captured grain inside AGG grain has high angle boundary of 90°.

The number of cycles and corresponding fatigue crack length are recorded.Incremental polynomial is used to determinate the crack propagation rate ().
Grain boundaries play an important role in hindering the further propagation of plastic zone.
Fig. 8 Determination of of the critical points (1#) After determining of the critical points, the fatigue crack propagation length in near-threshold zone can be obtained from the corresponding fatigue crack propagation rate and cycle numbers at different test points in the near-threshold zone.
The equivalent diameters of 3~4 prior austenite grains at each critical point are measured, and the average is taken as the corresponding prior austenite grain size .
Relationship between Size of Plastic Zone and Prior Austenite Grain Size 5.1 Size of Plastic Zone at Critical Points.

Grain Potential Productivity of Cultivated Land in Baoji, Shaanxi Province, China Tuansheng Lia, Haohao Wu,b , Hongzhi Zhaoc College of Earth Science and Resources, Chang’an University, Xi’an, Shaanxi, 710054, China atuanshen@chd.edu.cn, bwhh_xkp@yahoo.cn, c247911938@qq.com, Keywords: grain potential productivity; agricultural land classification; Baoji Division Abstract.
Many scholars have made a large number of researches about the crop photosynthetic potential productivity, photo-temperature potential productivity, climatic potential productivity and land potential productivity from different angles ever since.
In the agricultural land classification, the natural quality index of a classification unit is theoretical standard grain yield got by land conditions of a classification unit revising the photo-temperature (or climatic) potential productivity of the crops, and converted by grain yield ratio coefficient.
Therefore, the utilization quality index of land is a standard grain yield that can be got by increasing investments and use level.
Result analyses The grain potential productivities of cultivated land of Baoji are shown in table 1.

The number of lattice points in the FDM is 256 ×256, and nodes in FEM is 6156.
The number of nuclei decreaces with increase of number of additional elements.
Grain diameters are calculated on the basis of the number of finite element included in each recrystallized grain.
The number of grains whose diameters are less than 0.4 µm is biggest in the case of .
It is obvious that more additional elements keep grains from recrystallizing, and the number of recrystallized grains become smaller.

The simulation results showed that the greater the restored energy, the greater the number of the recrystallized grains.
In order to simulate grain growth in a single-phase system, only the free energy density function f0 is required to provide a certain excess free energy at the grain boundary.
The parameters of the gradient term K2 and the coupling term K1 have been determined by the grain boundary energy and the grain boundary range.
The smaller grains shrink until they are absorbed by the surrounding grains, and the grain morphology remains relatively stable during the growth process, which is consistent with the main characteristics of grain growth.
On the other hand, the greater the restored energy, the greater the number of the recrystallized grain.

Brewer's grains is the main by-product of beer industry.
In this work, the waste brewer's grains has been modified through physical and chemical methods to generate suitable biosorption material.
The adsorption conditions was also studied so as to utilize the brewer's grains as the low cost material for Cr(VI) wastewater purification and the brewer's grains reutilization, then the results would be the theoretical basis for the comprehensive utilization of the material.
Material and Methods Reagents and instruments Preparation of modified brewer's grains biosorbent:The brewer's grains was from the bee laboratory in our school, washed with tap water, and broiled in 0.5 mol·L-1 sulfuric acid for 24 h.
And the 60-80 meshes of brewer's grains were selected in further experiments.

The as-extruded alloy bars retain equiaxed grains with a large number of precipitated phases, β-Al12Mg17 and AlMg2Zn.
The grain size is about 2 mm.
Many small precipitates distribute on the grain boundaries and inner grains.
There exists a large number of dimples, some cleavage steps and small tearing cracks on the fracture surface, which suggests toughness fracture feature.
A large number of precipitates (β-Al12Mg17 and AlMg2Zn) with a particle size of about 200nm occurred during hot extrusion, which distribute along the grain boundaries and throughout the interior of the grains