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51.
A local scale, called the meso-scale, has recently been introduced to the multi-scale approach for 2D granular materials. This local scale is defined at the level of meso-domains enclosed by particles in contact. Stress and strain have been defined at this local scale, and their relation with the local structure has been studied. The purpose of this paper is to analyse the behaviour of granular materials at the meso-scale, i.e. the stress–strain–structure relationship at this scale. Analyses are performed on a 2D numerical granular sample subjected to a biaxial compression test and simulated with the Discrete Element Method (DEM). The sample is quite dense and it is loaded at a relatively low strain rate so that the state of the sample can be considered as being quasi-static. The size of sub-domains in the sample varies largely from 3 to 12 particles. It is shown that the evolution of the internal state of the sample corresponds, at the meso-scale, to a clear evolution of the quantity of meso-domains oriented in different directions. In addition, the behaviour of meso-domains is highly governed by their orientation rather than their density, especially for the strongly elongated meso-domains: the meso-domains oriented in the compression (resp. extension) direction behave like a dense (resp. loose) granular material. 相似文献
52.
Mrinal Iyer 《Journal of the mechanics and physics of solids》2011,59(8):1506-1535
The quasi-continuum method has provided many insights into the behavior of lattice defects in the past decade. However, recent numerical analysis suggests that the approximations introduced in various formulations of the quasi-continuum method lead to inconsistencies—namely, appearance of ghost forces or residual forces, non-conservative nature of approximate forces, etc.—which affect the numerical accuracy and stability of the method. In this work, we identify the source of these errors to be the incompatibility of using quadrature rules, which is a local notion, on a non-local representation of energy. We eliminate these errors by first reformulating the extended interatomic interactions into a local variational problem that describes the energy of a system via potential fields. We subsequently introduce the quasi-continuum reduction of these potential fields using an adaptive finite-element discretization of the formulation. We demonstrate that the present formulation resolves the inconsistencies present in previous formulations of the quasi-continuum method, and show using numerical examples the remarkable improvement in the accuracy of solutions. Further, this field theoretic formulation of quasi-continuum method makes mathematical analysis of the method more amenable using functional analysis and homogenization theories. 相似文献
53.
54.
OFDM with mixed-numerologies enhances the system flexibility effectively to meet the demands of diversified application scenarios. However, the coexistence of waveforms with different numerologies leads to serious inter-numerology interference (INI), and the corresponding relationship between the number of guard subcarriers and the power of INI needs to be considered for scheduling subcarriers. In this paper, we propose a multi-scale mapping (MSM) and INI cancellation (MSM-INIC) algorithm as well as the corresponding de-MSM algorithm for mixed-numerologies OFDM system. Based on the proposed algorithms, we provide a novel transceiver in the scenario of multi-path fading channel, in which subcarrier scheduling does not need to consider whether the guard band is allocated. In the proposed transmitter, an additional MSM-INIC module is employed to pre-compensate signal distortion for downlink, and in the receiver, a de-MSM module is applied to de-map the received signals for recovering the original numerologies. Furthermore, we reveal the inherent property of the mapped signals, and propose a low computational complexity de-MSM algorithm accordingly. Simulation results verify the superiority of the proposed transceiver in BER performance as well as spectrum efficiency even without any guard band. 相似文献
55.
Fan Xu Heng Hu Michel Potier-Ferry Salim Belouettar 《International Journal of Solids and Structures》2014
Bridging techniques between microscopic and macroscopic models are discussed in the case of wrinkling analysis. The considered macroscopic models are related to envelope equations of Ginzburg–Landau type, but generally, they are not valid up to the boundary. To this end, a multi-scale approach is considered: the reduced model is implemented in the bulk while the full model is applied near the boundary and these two models are coupled with the Arlequin method (Ben Dhia, 1998). This paper focuses on the definition of the coupling model and the transition between two scales. Especially, a new nonlocal bridging technique is presented and compared with another recent one (Hu et al., 2011). The present method can also be seen as a guide for coupling techniques involving other reduced order models. 相似文献
56.
Human beings often observe objects or deal with data hierarchically structured at different levels of granulations. In this paper, we study optimal scale selection in multi-scale decision tables from the perspective of granular computation. A multi-scale information table is an attribute-value system in which each object under each attribute is represented by different scales at different levels of granulations having a granular information transformation from a finer to a coarser labelled value. The concept of multi-scale information tables in the context of rough sets is introduced. Lower and upper approximations with reference to different levels of granulations in multi-scale information tables are defined and their properties are examined. Optimal scale selection with various requirements in multi-scale decision tables with the standard rough set model and a dual probabilistic rough set model are discussed respectively. Relationships among different notions of optimal scales in multi-scale decision tables are further analyzed. 相似文献
57.
Gas-solid fluidized beds are widely considered as nonlinear and chaotic dynamic systems. Pressure fluc- tuations were measured in a fluidized bed of 0.15 m in diameter and were analyzed using multiple approaches: discrete Fourier transform (DFT), discrete wavelet transform (DWT), and nonlinear recur- rence quantification analysis (RQA). Three different methods proposed that the complex dynamics of a fluidized bed system can be presented as macro, meso and micro structures. It was found from DFT and DWT that a minimum in wide band energy with an increase in the velocity corresponds to the transition between macro structures and finer structures of the fluidization system. Corresponding transition veloc- ity occurs at gas velocities of 0.3, 0.5 and 0.6 m]s for sands with mean diameters of 150, 280 and 490/~m, respectively. DFT, DWT, and RQA could determine frequency range of0-3.125 Hz for macro, 3. ! 25-50 Hz for meso, and 50-200 Hz for micro structures. The RQA showed that the micro structures have the least periodicity and consequently their determinism and laminarity are the lowest. The results show that a combination of DFT, DWT, and RQA can be used as an effective approach to characterize multi-scale flow behavior in gas-solid fluidized beds. 相似文献
58.
A novel conformation optimization model and algorithm for structure-based drug design 总被引:1,自引:0,他引:1
Ling Kang Honglin Li Xiaoyu Zhao Hualiang Jiang Xicheng Wang 《Journal of mathematical chemistry》2009,46(1):182-198
In this paper, we present a multi-scale optimization model and an entropy-based genetic algorithm for molecular docking. In
this model, we introduce to the refined docking design a concept of residue groups based on induced-fit and adopt a combination
of conformations in different scales. A new iteration scheme, in conjunction with multi-population evolution strategy, entropy-based
searching technique with narrowing down space and the quasi-exact penalty function, is developed to address the optimization
problem for molecular docking. A new docking program that accounts for protein flexibility has also been developed. The docking
results indicate that the method can be efficiently employed in structure-based drug design. 相似文献
59.
This article attempts to bring an enhanced insight into the analysis of in-plane shear behavior of woven fabrics. Two common methods have been used to characterize the shear behavior of woven preforms, namely the Bias Extension (BE) and Picture Frame (PF) tests. In spite of the identical macro-scale shear deformation of fabrics in these two characterization procedures, the current study demonstrates that their underlying micro- and meso-scale deformation mechanisms are quite distinct. The trellising mechanism, which is based on the well-known Pin-Joint Theory (PJT), has been regarded for a long time as the sole model to describe the meso-scale deformation of woven fabrics in both the BE and PF tests. Throughout this article, this mechanism is challenged for the PF test by undertaking a multi-scale analysis along with a critical review and integration of the previous experimental, analytical, and numerical studies. Intra-yarn shear, which has not been fully understood yet, is substantiated as a potential meso-level deformation mechanism occurring in the PF test. Accordingly, a new meso-level deformation model is proposed and compared with the trellising shear pattern in the BE setup. Afterward, the comparison is extended from meso-level to macro-level in order to provide more in-depth hypotheses for explaining differences reported in the literature between the shear characteristics of fabrics using BE and PF tests. Finally, some guidelines have been sought to select more reliable characterization method given a forming process. 相似文献
60.
Feiguo Chen Wei Ge Li Guo Xianfeng He Bo Li Jinghai Li Xipeng Li Xiaowei Wang Xiaolong Yuan 《Particuology》2009,7(4):332-335
A supercomputer with 1.0 Petaflops peak performance in single precision, designed and established by Institute of Process Engineering, Chinese Academy of Sciences, is introduced in this brief communication. A designing philosophy utilizing the similarity between hardware, software and the problems to be solved is embodied, based on the multi-scale method and discrete simulation approaches developed at Institute of Process Engineering (IPE) and implemented in a graphic processing unit (GPU)-based hybrid computing mode. The preliminary applications of this machine in areas of multi-phase flow, molecular dynamics and so on are reported, demonstrating the supercomputer as a paradigm of green computation in new architecture. 相似文献