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Open access

X. Xue, Y. Wang, H. Korpelainen and C. Li

Summary

Picea asperata Mast., which occurs in a restricted habitat in western China, has a wide ecological amplitude. In the present study, ten natural populations of P. asperata were studied using AFLP markers to investigate the population genetic structure and the level of genetic diversity. Of the 210 loci identified with two EcoRI/MseI primer combinations, 142 loci were found to be polymorphic. Yet, the level of genetic diversity observed within populations was quite low. The averages of NEI’s gene diversities (h) and Shannon's indices of diversity (I) calculated across populations equaled 0.156 and 0.227, respectively. The coefficient of gene differentiation among populations, based on the estimate GST and the unbiased estimate Φst, equaled 0.340 and 0.231, respectively. The mean genetic distance (D) between population pairs was 0.119 (range 0.050-0.156). Such high values indicate that there is significant differentiation among populations of P. asperata. Several factors could have contributed to the strong population differentiation, including relatively limited gene flow between populations (Nm = 0.968). Variation in environmental conditions and consequent selection pressures may be other factors attributing to the high level of genetic differentiation among populations. In addition, it was discovered that the geographic distances are not correlated with the genetic distances between the populations of P. asperata.

Open access

W. Li, J. Chen, H. Liang and C. Li

Abstract

The effect of porosity on high temperature compression and creep behavior of porous Cu alloy for the new molten carbonate fuel cell anodes was examined. Optical microscopy and scanning electron microscopy were used to investigate and analyze the details of the microstructure and surface deformation. Compression creep tests were utilized to evaluate the mechanical properties of the alloy at 650 °C. The compression strength, elastic modulus, and yield stress all increased with the decrease in porosity. Under the same creep stress, the materials with higher porosity exhibited inferior creep resistance and higher steadystate creep rate. The creep behavior has been classified in terms of two stages. The first stage relates to grain rearrangement which results from the destruction of large pores by the applied load. In the second stage, small pores are collapsed by a subsequent sintering process under the load. The main deformation mechanism consists in that several deformation bands generate sequentially under the perpendicular loading, and in these deformation bands the pores are deformed by flattering and collapsing sequentially. On the other hand, the shape of a pore has a severe influence on the creep resistance of the material, i.e. every increase of pore size corresponds to a decrease in creep resistance.

Open access

C. Li, Q. Meng, R. Reddy and C. Xu

Abstract

A new jar-like ZnO structure was synthesized by heating a mixture of Zn and InI3 powder with a weight ratio of 4:1 dispersed on Si wafer at 450°C in air. The diameter of the jar was of the order of 15 μm and the length of 20 μm. The formation of a molten InI3 drop, coating the drop with Zn powders, oxidation of these Zn grains, decomposition of InI3 to In and I vapors and the subsequent release of these vapors from the structure are considered important steps in the formation of the observed structures. The necessary elements in forming such structures are analyzed, which can be used as a guide in the design of experiments to synthesize similar structures for different purposes. Such structures are predicted to be able to soak large amount of liquid and release it at low rate, which is a desired property in some applications.

Open access

G. Chen, Y. Wang, C. Zhao, H. Korpelainen and C. Li

Abstract

Hippophae rhamnoides L., a dioecious and deciduous shrub species, occupies a wide range of habitats in the Wolong Nature Reserve, Southwest China. Our present study investigated the pattern of genetic variation and differentiation among five natural populations of H. rhamnoides, occurring along an altitudinal gradient that varied from 1,800 to 3,400 m above sea level in the Wolong Natural Reserve, by using ISSR markers. Based on fingerprinting patterns generated by fifteen primers, high levels of genetic variation were present within populations and subpopulations. Substantial genetic divergence was observed among populations, and also among female and male subpopulations, the GST values equaling 0.182, 0.222, and 0.238, respectively. Such considerable divergence present among populations and subpopulations may be caused by complex topography which effectively restricts gene flow, and by variable climatic conditions at different altitudes which may cause varying selective pressures. A significantly positive correlation between genetic and altitudinal distances was detected for the five populations and female subpopulations of H. rhamnoides. The cluster analysis including all populations or male subpopulations resulted in three altitude groups. Our results suggest that altitudinal gradients may be the prime cause affecting the genetic variation pattern of different populations and subpopulations in H. rhamnoides in the Wolong Nature Reserve, Southwest China.

Open access

D.W. Qian, S.W. Tong and C.D. Li

Abstract

This paper investigates the formation control problem of multiple agents. The formation control is founded on leader-following approaches. The method of integral sliding mode control is adopted to achieve formation maneuvers of the agents based on the concept of graph theory. Since the agents are subject to uncertainties, the uncertainties also challenge the formation-control design. Under a mild assumption that the uncertainties have an unknown bound, the technique of nonlinear disturbance observer is utilized to tackle the issue. According to a given communication topology, formation stability conditions are investigated by the observer-based integral sliding mode formation control. From the perspective of Lyapunov, not only is the formation stability guaranteed, but the desired formation of the agents is also realized. Finally, some simulation results are presented to show the feasibility and validity of the proposed control scheme through a multi-agent platform.

Open access

X. Yang, C. Liu, Y. Liu, X. Li and Y. Xu

Abstract

TiO2-SiO2 (TiO2 supported on SiO2) photocatalysts were prepared using an ultrasonic-assisted sol-gel method. These photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and photoluminescence spectra (PL). Their photocatalytic activities were investigated by the method of methyl orange oxidation. It was found that the photocatalytic activity of TiO2-SiO2 was optimal when the molar ratio of hexadecyl trimethyl ammonium bromide to titanium butoxide was 1:10. The average crystallite size of TiO2-SiO2 was smaller than that prepared by the stirring method. Furthermore, for pure anatase phase samples, it was shown that the lower the photoluminescence intensity, the higher the photocatalytic activity.

Open access

C. B. Yuen and Teresa Li

Abstract

Property management has often been described as an after-sale service because the participation of professional property managers is only required upon completion of the building. Recently, however, property management has become an integral part of project development based on its value. These days, managing recreational facilities such as residents’ clubs, gyms and swimming pools, given the frequent use of electronic installations, no longer falls under basic caretaking services. The early detection of hidden problems such as poor quality concealed cables, conduits and pipes and the improper selection of building materials saves time and money in subsequent maintenance and repair work, simultaneously reducing any inconvenience experienced by end-users due to a breakdown in services or defective rectification.

Environmental protection and energy conservation are becoming increasingly important in our daily lives, and thus are unavoidable agendas in the design and construction of buildings, be they domestic, commercial or industrial. The input of professional property managers based on their foresight and past work experience with end-users is crucial to the success of such schemes. This paper reviews the value of professional property managers in residential project development.

Open access

N. Min, H.M. Li, CH. Xie and X.C. Wu

Abstract

In this work, we present mechanical spectroscopy of cold work tool steel subjected to sub-zero cryogenic soaking treatment to reveal the carbon segregation and the subsequent carbides refinement. The maximum of Snoek-Köster (SK) peak height was obtained in the sample subjected to soaking 1h at −130°C cryogenic treatment. The SK peak height is reduced with prolonging the soaking time. The results indicate that an increase in the height of SK peak is connected with an increase in dislocation density and the number of segregated carbon atoms in the vicinity of dislocations or twin planes after martensite transformation at −130°C which is confirmed by corresponding TEM and atom probe tomography measurement. Hence, it is suggested that the isothermal martensite, formed during the cryogenic soaking treatment decreases (APT) the height of SK peak.

Open access

C. Li, F. Jiang, S. Ju, J. Peng, Y. Wei and L. Zhang

Abstract

Experiments were performed in an interdigital micromixer with 30 microchannels (40 μm width of each channel) to separate In3+, Fe3+ and Zn2+ from sulfate solutions using Di-(2-ethylhexyl)phosphoric acid (D2EHPA) as the extractant. The effects of pH, extractant concentration and flow rate on the extraction efficiency and flow rate on mass transfer coefficient of In3+, Fe3+ and Zn2+ were investigated. At a phase flow rate of 7.0 mL/min and initial solution pH of 0.423, the extraction efficiency of In3+, Fe3+ and Zn2+ was 99.29%, 3.43% and 2.54%, respectively and mass transfer coefficient of In3+, Fe3+ and Zn2+ was 144.307 s−1, 1.018 s−1 and 0.750 s−1. Then, the loaded organic phase was stripped in an interdigital micromixer. At a phase flow rate of 9.0 mL/min and HCl concentration of 160 g/L, stripping efficiency of In3+ was 98.92% and mass transfer coefficient of In3+ was 169.808 s−1, while concentration of Fe3+ and Zn2+ was lower than 0.005 g/L with good separation of In3+ from Fe3+ and Zn2+.

Open access

S. Zhang, L. Qi, C. Chen, X. Li, W. Song, R. Chen and S. Han

Abstract

This screening study analyzed ploidy levels by counting the chromosome number of 61 Aigeiros cultivars grown in China. Triploid Aigeiros has been found in four of these cultivars: Populus x euramericana (Dode) Guiner cv. Wuhei-1, P. × Liaohenica, P. Langfangensis-3 Wang (P. deltodide Barry cv. “Shanhaiguan” × P. simonii × P. pyramidalis-12 +Ulmus pumila Linn.), and P. × euramericana (Dode) Guinier. cv. “Zhonglin-46”. The karyotype analysis indicates that triploid Aigeiros might be derived from original allotriploid. Because growth of the triploid trees was faster than their respective diploid hybrids or clones in the plantations where we collected the materials, we expect that they will play a significant role in breeding, reforestation and fiber production in China.