Search results

In fact, the horizontal rotary-disc-type precision seed-metering[5-7] can meet the technical requirement of single seed in one plant-opening to some extent, but some problems such as seeds damaged, replanted or leaking to be planted are always occurred so that it is difficult to meet the requirement of accurate planting and plant number per area because both methods of cleaning redundant planting and seed charge are achieved by mechanic device.
If the distance is too long, the belt moving speed must also be fast so that the transportation speed of seeds could meet the planting speed, which is disadvantage to fill the seed into the scoop; on the contrary, if the distance is too short, the probability of repeatedly filling seed into spoon will sharply decrease because the stock between both seed-spoons is too few[6].Given that the probability of filling seed into scoop is denoted as p(a) which is slipped along the top of seed-scoop, the probability p(λ) of secondly filling seed into the seed-scoop is: (5) 3 Experiment and result 3.1 Experimental method The Xianyu 335 corn seed is chosen, the experimental method is established according to the requirement of GB6973-86《single grain planter (precision) test method》,250 seeds are measured for each test, and each test is repeated three times[10].
It can be seen by combination of above test results that the designed precision seed-metering owns good performance for high or low planting speed, such as high single seed plant rate, low seed damaged rate, and the integrated performance achieve the best when the belt speed is 1.05 m/s. 4 Conclusions 1) The optimal size of seed-scoop is 8mmX12mm which may achieve the single seed plant rate 98.6%, multi-seed rate 0.48%, leakage seed rate 1.78% and seed damaged rate 0.05% 2) The belt type of the precision seed-metering owns good operational character such as the single seed plant rate 98.6%, multi-seed rate 6.3% ,leakage plant rate 0.8%, damage seed rate 0.05%. 3) Good adaptability for high or low operating speed, which meets the working requirement for different operating conditions, and the best planting speed is 1.05m/s. 4) Simple structure which can be used for different grains by changing the seed scoop; even make seeds and fertilizer to plant at meantime by adding the fertilizer-spoon

The creep activation energy observed in this study is close to those of high temperature alloys [17, 18], but smaller than that of grain growth at 850~950 ºC [20] and that of Ni diffusion in CrMnFeCoNi high entropy alloy [21].
With the increase of stress, the number and mobility of thermal vacancies increased, causing more visible large voids.
Lu, Grain growth and the Hall–Petch relationship in a high-entropy FeCrNiCoMn alloy, Scripta Materialia 68 (2013) 526–529

The background strongly depends on defective structures, in particular grain size and dislocation density [10].
Since heat treatments at 800 °C for 8.28 x 10 4 s (23 hours) do not change the mean grain size and scarcely affect the dislocation density [5], also repeated test runs do not remarkably modify these microstructural features and, consequently, the background level.
In the samples already submitted to IF test runs part of the material has been transformed and its fraction depends on the number of runs.

A number of factors such as the deformation history, microstructure stability, corrosion, stresses, creep behaviour and composition of scale play a important role in the life extension of highresistant steels [4,5].
The critical concentration of solute metal providing the formation of a protective scale during selective oxidation decreases with decreasing alloy grain size.
It is a result of fast diffusion along the grain boundaries, dislocations, martensitic laths, etc.

C15 case-hardening steel was used as a basic material for the investigation and carbide powders (WC, TaC and NbC) were used for the dispersion. [1,2,4] The following parameters were determined as variables: ♦ the scanning velocity of laser :300 … 700 [mm/min] and ♦ the grain-dosing: 1 … 3.25 g/min. 2.2 Wear experiment in case of surface dispersed samples There is no mature, unified method to determine wear resistance as an absolute number, such as tensile strenght.
Parameters of the experiments: Cutting paper used for metallographic samples, SiC grained, size 230x280 mm, sign P180, for dry grinding.

The results of property improvement mainly depend on the effect of grain size refinement.
Most of the cracks generate along grain boundaries and present obvious intergranular cracking characteristics.
Acknowledgement The authors gratefully thank the financial support of the National Natural Science Foundation of China under the granted number of 50375096.

Table 3 Cooling rate of specimens specimen 1 2 3 4 5 6 △t[s] 50 71 69 56 37 29 CR[℃/s] 2.801 1.972 2.029 2.295 3.784 4.375 Metallographs We take a large number of photographs of every specimen from one side to the other in 100 times magnification.
For example, changes in carbon concentration or lattice, grain refinement, and so on.
Modelling of inoculation of met allicmelts: Application to grain refinement of aluminium by Al-Ti-B.

After a number of preparations some sets of technical parameters were selected for scanning.
And the large alloy phase possibly generated across crystal grain cracks.
Fig.2 Across crystal grain cracks Fig.3 Traverse crack Fig.4 Cracks caused by gas cavities 3.3 Effects of component 3.3.1 Effects of nickel Adding Nickel into Fe-Cr-C alloy can increase plasticity of the cladding coating.

Its average molecular number was about 1600 and the melting point was 180-210°C.
The apparent mean grain size (L) of the β-SiC crystalline phase present in the samples was calculated from the width (D) of the (111) diffraction peak at mid-height, according to the following Eq. 1.
Fig.2 XPS patterns of SiC-2 fiber Fig.3 FT-IR spectra of the fibers Fig.4 XRD patterns of the fibers Table 3 The size of β-SiC crystallite grain in different fibers Fibers SiC-2 SiC-1 SiC NL-202[5,6] L111(nm) 2.8 2.6 1.7 2.1 It can be observed that the crystalline size of SiC-1 and SiC-2 fibers is bigger than that of SiC fibers and it suggests that the crystallinity of CVC SiC fibers is better than the traditional SiC fibers.

Acknowledgements The open fund of Key Laboratory of Material Corrosion and Protection of Sichuan Colleges and Universities (Project Number: 2009CL05) References [1] Tiegeng Xiang.
Effect of initial grain size on the secondary grain growth in molybdenum sheet [J].Materials Science and Engineering, 1984, 68(1):45-53