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Search Results: 1 - 10 of 31233 matches for " Hui Dai "
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A New Algorithm for the Acquisition of Knowledge from Scientific Literature in Specific Fields Based on Natural Language Comprehension  [PDF]
Hui Wei, Zhi-long Dai
International Journal of Intelligence Science (IJIS) , 2011, DOI: 10.4236/ijis.2011.12005
Abstract: The acquisition of knowledge and the representation of that acquisition have always been viewed as the bottleneck in the construction of knowledge-based systems. The traditional methods of acquiring knowledge are based on knowledge engineering and communication with field experts. However, these methods cannot produce systematic knowledge effectively, automatically construct knowledge-based systems, or benefit knowledge reasoning. It has been noted that, in specific professional fields, experts often use fixed patterns to describe their expertise in the scientific articles that they publish. Abstracts and conclusions, for example, are key components of the scientific article, containing abundant field knowledge. This paper suggests a method of acquiring production rules from the abstracts and conclusions of scientific articles in specific fields based on natural language comprehension. First, the causal statements in article abstracts and conclusions are extracted using existing techniques, such as text mining. Next, antecedence and consequence fragments are extracted using causal template matching algorithms. As the final step, part-of-speech-tagging production rules are automatically generated according to a syntax parsing tree from the speech pair sequence. Experiments show that this system not only improves the efficiency of knowledge acquisition but also simultaneously generates systematic knowledge and guarantees the accuracy of acquired knowledge.
An improved PSO algorithm and its application in seismic wavelet extraction
Yongshou Dai,Hui Niu
International Journal of Intelligent Systems and Applications , 2011,
Abstract: The seismic wavelet estimation is finally a multi-dimension, multi-extreme and multi-parameter optimization problem. PSO is easy to fall into local optimum, which has simple concepts and fast convergence. This paper proposes an improved PSO with adaptive parameters and boundary constraints, in ensuring accuracy of the algorithm optimization and fast convergence. Simulation results show that the methods have good applicability and stability for seismic wavelet extraction.
Pathways, Scaling Laws and Analytical Solutions for Crease Formations in a Gel Layer
Xiaoyi Chen,Hui-Hui Dai
Physics , 2014,
Abstract: An analytical study on crease formations in a swelling gel layer is conducted. By exploring the smallness of the layer thickness and using a method of coupled series-asymptotic expansions, the original nonlinear eigenvalue problem of partial differential equations is reduced to one of ordinary differential equations. The latter problem is then solved analytically to obtain closed-form solutions for all the post-bifurcation branches. With the available analytical results, a number of deep insights on crease formations are provided, including the unveiling of three pathways to crease (depending on the layer thickness), determination of the bifurcation type, establishment of a lower bound for mode numbers and two scaling laws. Also, a number of experimental results are captured, which are then nicely interpreted based on the analytical solutions. In particular, it is shown that some critical physical quantities are invariant with respect to the thickness at the moment of crease formation. It appears that the present work offers a comprehensive understanding on crease formation, a widely-spread phenomenon.
Instabilities Induced by Phase Fronts Coalescence During the Phase Transitions in a Thin Sma Layer: Mechanism and Analytical Descriptions
Hui-Hui Dai,Jiong Wang
Physics , 2009,
Abstract: Systematic experiments on stress-induced phase transitions in thin SMA structures in literature have revealed two interesting instability phenomena: the coalescence of two martensite-austenite fronts leads to a sudden stress drop and that of two austenite-martensite fronts leads to a sudden stress jump. In order to get an insight into these two phenomena, in this work we carry out an analytical study on the stress-induced phase transitions in a thin SMA layer (a simple structure in which the two coalescence processes can happen). We derive a quasi-2D model with a non-convex effective strain energy function while taking into account the rate-independent dissipation effect. By using a coupled series-asymptotic expansion method, we manage to express the total energy dissipation in terms of the leading-order term of the axial strain. The equilibrium equations are obtained by maximizing the total energy dissipation, which are then solved analytically under suitable boundary conditions. The analytical results reveal that the mechanism for such instabilities is the presence of "limited points", which cause the switch of nontrivial solution modes to trivial solution modes. Descriptions for the whole coalescence processes of two fronts are also provided based on the analytical solutions, which also capture the morphology varies of the specimen. It is also revealed the key role played by the thickness-length ratio on these instabilities: the zero limit of which can lead to the smooth switch of nontrivial modes to trivial modes with no stress drop or stress jump.
An Analytical Study on the Instability Phenomena During the Phase Transitions in a Thin Strip under Uniaxial Tension
Hui-Hui Dai,Zongxi Cai
Physics , 2009,
Abstract: In the experiments on stress-induced phase transitions in SMA strips, several interesting instability phenomena have been observed, including a necking-type instability, a shear-type instability and an orientation instability. By using the smallness of the maximum strain, the thickness and width of the strip, we use a methodology, which combines series expansions and asymptotic expansions, to derive the asymptotic normal form equations, which can yield the leading-order behavior of the original three-dimensional field equations. Our analytical results reveal that the inclination of the phase front is a phenomenon of localization-induced buckling (or phase-transition-induced buckling as the localization is caused by the phase transition). Due to the similarities between the development of the Luders band in a mild steel and the stress-induced transformations in a SMA, the present results give a strong analytical evidence that the former is also caused by macroscopic effects instead of microscopic effects. Our analytical results also reveal more explicitly the important roles played by the geometrical parameters.
On a consistent finite-strain plate theory based on 3-D energy principle
Hui-Hui Dai,Zilong Song
Physics , 2014, DOI: 10.1098/rspa.2014.0494
Abstract: This paper derives a finite-strain plate theory consistent with the principle of stationary three-dimensional (3-D) potential energy under general loadings with a third-order error. Staring from the 3-D nonlinear elasticity (with both geometrical and material nonlinearity) and by a series expansion, we deduce a vector plate equation with three unknowns, which exhibits the local force-balance structure. The success relies on using the 3-D field equations and bottom traction condition to derive exact recursion relations for the coefficients. Associated weak formulations are considered, leading to a 2-D virtual work principle. An alternative approach based on a 2-D truncated energy is also provided, which is less consistent than the first plate theory but has the advantage of the existence of a 2-D energy function. As an example, we consider the pure bending problem of a hyperelastic block. The comparison between the analytical plate solution and available exact one shows that the plate theory gives second-order correct results. Comparing with existing plate theories, it appears that the present one has a number of advantages, including the consistency, order of correctness, generality of the loadings, applicability to finite-strain problems and no involvement of unphysical quantities.
Analytical Solutions for the Equilibrium states of a Swollen Hydrogel Shell and an Extended Method of Matched Asymptotics
Hui-Hui Dai,Zilong Song
Physics , 2011,
Abstract: A polymer network can imbibe water, forming an aggregate called hydrogel, and undergo large and inhomogeneous deformation with external mechanical constraint. Due to the large deformation, nonlinearity plays a crucial role, which also causes the mathematical difficulty for obtaining analytical solutions. Based on an existing model for equilibrium states of a swollen hydrogel with a core-shell structure, this paper seeks analytical solutions of the deformations by perturbation methods for three cases, i.e. free-swelling, nearly free-swelling and general inhomogeneous swelling. Particularly for the general inhomogeneous swelling, we introduce an extended method of matched asymptotics to construct the analytical solution of the governing nonlinear second-order variable-coefficient differential equation. The analytical solution captures the boundary layer behavior of the deformation. Also, analytical formulas for the radial and hoop stretches and stresses are obtained at the two boundary surfaces of the shell, making the influence of the parameters explicit. An interesting finding is that the deformation is characterized by a single material parameter (called the hydrogel deformation constant), although the free-energy function for the hydrogel contains two material parameters. Comparisons with numerical solutions are also made and good agreements are found.
Critical Thickness Ratio for Buckled and Wrinkled Fruits and Vegetables
Hui-Hui Dai,Yang Liu
Physics , 2013, DOI: 10.1209/0295-5075/108/44003
Abstract: Fruits and vegetables are usually composed of exocarp and sarcocarp and they take a variety of shapes when they are ripe. Buckled and wrinkled fruits and vegetables are often observed. This work aims at establishing the geometrical constraint for buckled and wrinkled shapes based on a mechanical model. The mismatch of expansion rate between the exocarp and sarcocarp can produce a compressive stress on the exocarp. We model a fruit/vegetable with exocarp and sarcocarp as a hyperelastic layer-substrate structure subjected to uniaxial compression. The derived bifurcation condition contains both geometrical and material constants. However, a careful analysis on this condition leads to the finding of a critical thickness ratio which separates the buckling and wrinkling modes, and remarkably, which is independent of the material stiffnesses. More specifically, it is found that if the thickness ratio is smaller than this critical value a fruit/vegetable should be in a buckling mode (under a sufficient stress); if a fruit/vegetable in a wrinkled shape the thickness ratio is always larger than this critical value. To verify the theoretical prediction, we consider four types of buckled fruits/vegetables and four types of wrinkled fruits/vegetables with three samples in each type. The geometrical parameters for the 24 samples are measured and it is found that indeed all the data fall into the theoretically predicted buckling or wrinkling domains. Some practical applications based on this critical thickness ratio are briefly discussed.
The Historical Features of Hoelderlin''''s Thought on Poetic Creation
荷尔德林创作思想的时代特征

DAI Hui,
戴晖

浙江大学学报(人文社会科学版) , 2000,
Abstract: Inherited directly from Rousseau and Schiller, Hoelderlin's idea on poetic creation focuses on human nature as a structure of knowledge in the art of poetry. Hoelderlin had gone through a period of philosophical studies before he began writing poetry. The Combination of rational thinking and poetic wisdom helped define the Western spirit, bringing with it a higher understanding and Sublimation of life itself.
Non-equilibrium Transport in dissipative one-dimensional Nanostructures
Hui Dai,Dirk K. Morr
Physics , 2010,
Abstract: We study the non-equilibrium transport properties of a one-dimensional array of dissipative quantum dots. Using the Keldysh formalism, we show that the dots' dissipative nature leads to a spatial variation of the chemical potential, which in disordered arrays, breaks the invariance of the current, I, under bias reversal. Moreover, the array's nanoscopic size results in an algebraic low-temperature dependence of I. Finally, we show that a local Coulomb interaction splits the dots' electronic levels, resulting in a Coulomb blockade, which is softened with increasing dissipation and array size.
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