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K. Li, M. Song, Y. Du and X. Fang

Effect of Minor Cu Addition on the Precipitation Sequence of an As-Cast Al-Mg-Si 6005 Alloy

The whole precipitation sequences of two as-cast Al-Mg-Si 6005 alloys (containing no Cu or 0.1 wt.% Cu) at 150°C were investigated using X-ray diffraction, transmission electron microscopy and hardness examinations. The precipitation sequence of the Cu-free alloy can be expressed as: super-saturated solid solution (SSSS) → spherical G.P. zones → pre-β'β' → U2 + Si + βx → Si +βx, while that of the Cu-containing alloy can be expressed as: SSSS → spherical G.P. zones + platelet-like G.P. zones → pre-β' → β' → Q' + β + Si → Q + β + Si. A new type of β precipitate, namely βx here, has been discovered in the Cu-free alloy. The addition of minor Cu is found to accelerate the microstructural evolution by inducing the formation of a new type of platelet-like G.P. zone along {111} Al planes, and improve the hardening response at the over-aged stage by forming Q' and Q precipitates.

Open access

S. Gan, M. Li, F. Li, K. Wu, J. Wu and J. Bai

Summary

Factorial mating crosses of Eucalyptus urophylla × E. tereticornis (3 x 5), E. urophylla × E. camaldulensis (3 x 3) and E. urophylla × E. exserta (3 x 3) were used for genetic analysis of growth traits and susceptibility to bacterial wilt (Ralstonia solanacearum). Genetic effects including female, male and female × male interaction were examined for height (H) and diameter at breast height (DBH) at age five as well as final bacterial wilt index (BWI) in both nursery inoculation and field assessment by five years of age. Female, male and female x male variances appeared to have a significant role in growth traits H and DBH though their magnitude varied for the factorials studied. For the trait BWI additive (male) and dominant (female x male) effects were both involved in the genetics of bacterial wilt susceptibility, and additive was the major. Estimates of narrow-sense heritability (h2) for H, DBH and BWI ranged from 0.11 ± 0.06 to 0.70 ± 0.09, varying with either trait or factorial. Growth traits (H and DBH) had low and non-significant phenotypic and genetic correlations with BWI in all the three factorials, ranging from -0.10 ± 0.08 to 0.17 ± 0.14 in coefficient of correlation. This indicates that it may be possible to select superior trees with both fast growth and high resistance to bacterial wilt in eucalypt hybrid populations in operational breeding programs.

Open access

Y. H. Peng, Z. X. Lu, K. Chen, O. Luukkanen, H. Korpelainen and Chun Yang Li

Abstract

In this study, the genetic diversity of Populus cathayana Rehd was investigated using microsatellite markers. In a total of 150 individuals collected from six natural populations in the southeastern part of the Qinghai-Tibetan Plateau in China, a high level of microsatellite polymorphism was detected. At the seven investigated microsatellite loci, the number of alleles per locus ranged from 5 to 16, with a mean of 11.3, the observed heterozygosities across populations ranged from 0.408 to 0.986, with a mean of 0.792, and the expected heterozygosities across populations ranged from 0.511 to 0.891, with a mean of 0.802. The proportion of genetic differentiation among populations accounted for 37.3% of the whole genetic diversity. The presence of such a high level of genetic diversity could be attributed to the features of the species and the habitats where the sampled populations occur: The southeastern part of the Qinghai-Tibetan Plateau is regarded as the natural distribution and variation center of the genus Populus in China. Variation in environmental conditions and selection pressures in different populations, and topographic dispersal barriers could be factors associated with the high level of genetic differentiation found among populations. The populations possessed significant heterozygosity excesses, which may be due to extensive population mixing at the local scale. The cluster analysis showed that the populations are not strictly grouped according to their geographic distances but the habitat characteristics also influence the divergence pattern. In addition, we suggest that population SHY should be regarded as an ecologically divergent species of P. cathayana.

Open access

Y. Yin, Y. Li, K. Wu and J. Zhou

Abstract

The main work of this paper focuses on the simulation of binary alloy solidification using the phase field model and adaptive octree grids. Ni-Cu binary alloy is used as an example in this paper to do research on the numerical simulation of isothermal solidification of binary alloy. Firstly, the WBM model, numerical issues and adaptive octree grids have been explained. Secondary, the numerical simulation results of three dimensional morphology of the equiaxed grain and concentration variations are given, taking the efficiency advantage of the adaptive octree grids. The microsegregation of binary alloy has been analysed emphatically. Then, numerical simulation results of the influence of thermophysical parameters on the growth of the equiaxed grain are also given. At last, a simulation experiment of large scale and long-time has been carried out. It is found that increases of initial temperature and initial concentration will make grain grow along certain directions and adaptive octree grids can effectively be used in simulations of microstructure.

Open access

H Yang, J Liu, K Li, X Yin, X Tan and J Wang

Abstract

3-Oxo-α-ionol ethyl carbonate, a precursor of megastigmatrienones was prepared by reduction of α-ionone to α-ionol, followed by esterification with ethyl chloroformate and then by oxidation with t-butyl chromate. The total yield was about 23%. Infrared (IR) and mass spectra of this compound were determined. Upon smoking, cigarettes to which 0.002% by weight of the titled compound was added had an improved and more harmonious flavor. The smoke was sweeter and had a cleaner after taste. Experimental results suggest that the title compound added to the tobacco pyrolyzes to form megastigmatrienones during smoking.

Open access

X. Sun, B. Su, L. Chen, Z. Yang and K. Li

Abstract

In this paper, a new type of interior composite-rotor bearingless permanent magnet synchronous motors (BPMSMs) with two layer permanent magnets (PMs) is proposed. In order to reduce the torque ripple of this kind of motors, the sizes of PMs are optimized. Moreover, the magnetic field analysis of the interior composite-rotor BPMSM with two layer PMs is carried out by the finite element method (FEM). The corresponding static electronic magnetic characteristics at no load, including magnetic field, PM flux linkage and inductance, are studied in detail. In addition, electromagnetic torque characteristics and suspension force characteristics are also investigated thoroughly. The results of the analysis and simulation lay a significant foundation for further research on the interior composite-rotor BPMSMs with two layer PMs.

Open access

Yinjiang Li, Mihai Rotaru and Jan K. Sykulski

Abstract

The paper discusses some of the recent advances in kriging based worst-case design optimisation and proposes a new two-stage approach to solve practical problems. The efficiency of the infill points allocation is improved significantly by adding an extra layer of optimisation enhanced by a validation process.

Open access

Kai Ni, Yihua Hu and Xinhua Li

Abstract

With the fast development of power electronics techniques, electrification of shipboard power systems (SPS) is an unstoppable trend, and the concepts of electric ships (ESs) and all-electric ships (AESs) emerge. In order to meet the constantly increasing electricity demand in SPS, the medium voltage direct current (MVDC) SPS becomes a promising shipboard electrical network architecture. This paper aims to present a comprehensive review of the design, control, power management, system stability and reliability in ESs. The most recent technologies and academic achievements in these fields are discussed. In the near future, it is possible that the electric propulsion technology will be widely applied to various types of ships.

Open access

K. Han, D. Zhao, Y. Liu, Q. Liu, X. Huang, J. Yang, K. Bi, T. Xu and Y. Li

Abstract

Duck Tembusu virus (DTMUV) is a newly emerging pathogenic flavivirus that has caused massive economic losses to the duck industry in China. Envelope (E) protein of DTMUV is an important structural protein, which is able to induce protective immune response in target animals and can be used as specific serological diagnosis tool. In this study, a novel monoclonal antibody, designated mAb 3E9, was generated against DTMUV E protein. It is positive in indirect ELISA against both His-E protein and the purified whole viral antigen. Also, this mAb showed positive reaction with DTMUV in Western blot and indirect immunofluorescence assay, and the isotype was IgG1. End-point neutralizing assay performed in BHK-21 cells revealed that the neutralization titer of 3E9 against DTMUV JS804 strain reached 1:50. Furthermore, functional studies revealed that 3E9 blocks infection of DTMUV at a step on viral attachment. The anti-E mAbs produced in the present work may be valuable in developing an antigen-capture ELISA test for antigen detection or a competitive ELISA test for antibody detection or therapeutic medicine for DTMUV in poultry.

Open access

L. Zhang, N. Huanqiong, Washington J. Gapare, S. K. Dillon, X. Li and H. X. Wu

Abstract

Genetic diversity within radiata pine first generation of open-pollinated selections (OPS) from the native resource stands was compared with that observed in native populations to monitor potential changes in genetic diversity during domestication. Genetic diversity was estimated using 58 single nucleotide polymorphisms (SNPs) from 8 expressed genes. Nucleotide diversity maintained in first generation of selections (OPS) (mean π = 0.0036; mean θw = 0.0058) was similar to that found within the native population material (mean π = 0.0043; mean for θw = 0.0065). Likewise, mean values for expected heterozygosity (HE) within and between native population material and OPS were similar (mean = 0.27 ± 0.04) and not significantly different (P = 0.068). Also, the overall distribution of allele frequency classes was not significantly different between native population material and OPS. These results point to no evidence of loss of diversity in OPS due to artificial selection. One possible reason is that the domestication of the OPS is at a very early stage. Another may be that artificial selection in the OPS was based on tree growth and form, not wood properties. The genes selected in this study are mostly involved in cell wall formation, thus genetic diversity of these genes should remain stable between natural population and OPS, unless there was a significant sampling bias in the OPS. Although the SNP information suggests similarities among mainland populations, results from quantitative genetic studies found large provenance differences for growth-, morphological-, stem-form traits, and disease resistance. Determining the threshold at which genetic diversity levels will be significantly reduced during selection should help breeders to make informed decisions regarding the intensity of selection in managed breeding populations as well as gene resource populations.