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Open access

H. P. Song and C. F. Gao

Abstract

The problem of a piezoelectric screw dislocation, line force and line charge around a permeable crack in a finite piezoelectric cylinder is dealt with in this paper. Utilizing the complex function and conformal mapping methods, the closed form solutions of the stress fields and the electric displacement fields are derived. The stress intensity factor and the image force are discussed in detail. The results show that the stress fields are in direct proportion to the line force, but independent of the line charge. The shielding effect produced by the dislocation increases with the increasing of the radius of the piezoelectric cylinder. Moreover, the unstable equilibrium point and the image force are also severely affected by the radius of the piezoelectric cylinder.

Open access

H. Qin, J. Xiao, X. Gao and H. Wang

Abstract

In contrast to the rapid development of the horse husbandry in China, the ability of horse veterinarians to diagnose diseases has not been improved and only a few domain experts have considerable expertise. At present, many expert systems have been developed for diseases diagnosis, but few for horse diseases diagnosis have been studied in depth. This paper presents the design and development of a computer-aided expert system for diagnosing horse diseases. We suggest an approach for diagnosis of horse diseases based on the analysis of diagnostic characteristics and the experiential knowledge of domain experts. It is based on using evidence-weighted uncertainty reasoning theory, which is a combination of evidence theory and an uncertainty pass algorithm of confidence factors. It enables drawing of inferences with atypical clinical signs and the uncertainty of the user’s subjective understanding. It reduces the influence of subjective factors on diagnostic accuracy. The system utilizes a user friendly interface for users and requests a confidence factor from users when feedback is given to the system. Horse-Expert combines the confidence factors with weight factors assigned to clinical signs by experts during the knowledge acquisition process to make diagnostic conclusions. The system can diagnose 91 common horse diseases, and provides suggestions for appropriate treatment options. In addition, users can check the medical record through statistical charts. The system has been tested in seven demonstration areas of Xinjiang province in northwestern China. By constantly maintaining and updating the knowledge base, the system has potential application in veterinary practice.

Open access

M. Zheng, H. Gao, H. Teng, J. Hu, Z. Tian and Y. Zhao

Abstract

In this article, it aims to propose effective approaches for hydro-forming process of bi-metallic composite pipe by assuming plane strain and elastic-perfectly plastic material model. It derives expressions for predicting hydro-forming pressure and residual stress of the forming process of bi-metallic composite pipe. Test data from available experiments is employed to check the model and formulas. It shows the reliability of the proposed model and formulas impersonally.

Open access

H. Liu, T. Økland, R. Halvorsen, J. Gao, Q. Liu, O. Eilertsen and H. Bratli

Gradients analyses of forests ground vegetation and its relationships to environmental variables in five subtropical forest areas, S and SW China

Monitoring of ground vegetation and environmental variables in subtropical forests in China was initiated in 1999 as part of the "Integrated Monitoring Programme of Acidification of Chinese Terrestrial Systems". The study areas were selected to span regional gradients, in deposition of airborne pollutants and climatic conditions. All five study areas are located in the southern and south-western parts of China and consist of subtropical forests. In each study area 50 1-m2 plots were randomly chosen within each of ten 10×10 m macro plots, each in turn positioned in the centre of 30×30 m extended macro plot. All 250 1-m2 plots were subjected to vegetation analysis, using frequency in subplots as measure of species abundance. A total of 33 environmental variables were recorded for 1-m2 plots as well as 10×10 m macro plots. A major objective of this study is to identify the environmental variables that are most strongly related to the species composition of ground vegetation in S and SW Chinese subtropical forests, as a basis for future monitoring.

Comparison among DCA, LNMDS and GNMDS ordination methods, an additional objective of the study, was achieved by using a set of different techniques: calculation of pair-wise correlation coefficients between corresponding ordination axes, Procrustes comparison, assessment of outlier influence, and split-plot GLM analysis between environmental variables and ordination axes. LNMDS and GNMDS consistently produce very similar ordinations. GNMDS ordinations are generally more similar to DCA than LNMDS to DCA. In most cases DCA, LNMDS and GNMDS extract the same main ground vegetation compositional gradients and the choice of LNMDS or GNMDS is therefore hardly decisive for the results. GNMDS was chosen for interpretation and presentation of vegetation-environment relationships. The dimensionality of GNMDS (number of reliable axes) was decided by demanding high correspondence of all axes with DCA and LNMDS axes. Three dimensions were needed to describe the variation in vegetation in two of the areas (TSP and LXH), two dimensions in the other three areas (LCG, LGS and CJT).

Environmental interpretation of ordinations (identification of ecoclines; gradients in species composition and the environment) was made by split-plot GLM analysis and non-parametric correlation analysis. Plexus diagrams and PCA ordination were used to visualize correlations between environmental variables. Several graphical means were used to aid interpretation.

Complex gradients in litter-layer depth, topography, soil pH/soil nutrient, and tree density/crown cover were found to be most strongly related to vegetation gradients. However, the five study areas differed somewhat with respect to which of the environmental variables that were most strongly related to the vegetation gradients (ordination axes). Litter-layer depth was related to vegetation gradients in four areas (TSP, LCG, CJT and LXH); topography in four study areas (TSP, LGS, CJT and LXH); soil pH in three areas (LCG, LGS and CJT); soil nutrients in one area (LGS); and tree density/crown cover in one area (LCG).

The ecological processes involved in relationships between vegetation and main complex-gradi-ents in litter-layer depth, topography, soil pH/soil nutrient, and tree density/crown cover, in subtropical forests, are discussed. We find that gradient relationships of subtropical forests are complex, and that heavy pollution may increase this complexity. Furthermore, our results suggest that better knowledge of vegetation-environment relationships has potential for enhancing our understanding of subtropical forests that occupy vast areas of the S and SW China.

Open access

Y. Zhang, Z. Gao and H. Zhang

Abstract

We study the growth of the transcendental meromorphic solution f(z) of the linear difference equation: where q(z), p0(z), ..., pn-(z) (n ≥ 1) are polynomials such that p0(z)pn(z) ≢ 0, and obtain some necessary conditions guaranteeing that the order of f(z) satisfies σ(f) ≥ 1 using a difference analogue of the Wiman-Valiron theory. Moreover, we give the form of f(z) with two Borel exceptional values when two of p0(z), ..., pn(z) have the maximal degrees.

Open access

Y. J. Wang, C. F. Gao, H. P. Song and S. C. Xing

Abstract

The half elliptical hole with an edge crack in a thermopiezoelectric material is studied by using the complex variable method. First, the mapping function which maps the outside of the elliptical hole and the crack in the right half plane into the outside of a circular hole in a full plane is given by the method of conformal mapping. Then, the complex potential functions and the field intensity factors (FIF) are presented according to the boundary conditions, respectively. Some useful results can be found by numerical analysis: 1) The influence of the heat flux on FIF depends on the model of the crack; 2) The shape and the size of the hole possess a significant effect on the field distribution at the crack tip.

Open access

Q. F. Meng, W. T. Gao, J. Y Pang and Y. H. Weng

Abstract

Demand for planting elite shrub willows as a resource for industrial use such as bioenergy and pulp has been increasing in Jilin province in northeast China. Toward this end, 12 elite willow clones, representing various species and origins, were imported from New York, USA, and planted at Lushui River, Jilin province. Two indigenous species were included in the test as the controls for comparison. This study was an evaluation of their performance in adaptation, growth potential, and wood traits after one rotation (three growing seasons). Results indicated that (1) all clones, but one, showed a parallel phenology to the control, had excellent survival (> 86%) and displayed good frost resistance; (2) compared to the control, most imported clones were comparable in main stem growth (height and diameter), but developed more stems and main roots; and (3) most imported clones had similar lignin, but higher cellulose content relative to the control. These results imply that some of the imported clones should be considered for further evaluation as good sources for both bioenergy and pulping. Based on cluster analysis, six clones were recommended for the upcoming scale-up site-clone trials for yield evaluation.