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An extended cell-based smoothed discrete shear gap method (XCS-FEM-DSG3) for free vibration analysis

M. H. NGUYEN-THOI,L. Le-ANH,V. Ho-HUU,H. Dang-TRUNG,T. NGUYEN-THOI

《结构与土木工程前沿（英文）》 2015年第9卷第4期页码 341-358 doi: 10.1007/s11709-015-0302-1

摘要： A cell-based smoothed discrete shear gap method (CS-FEM-DSG3) was recently proposed and proven to be robust for free vibration analyses of Reissner-Mindlin shell. The method improves significantly the accuracy of the solution due to softening effect of the cell-based strain smoothing technique. In addition, due to using only three-node triangular elements generated automatically, the CS-FEM-DSG3 can be applied flexibly for arbitrary complicated geometric domains. However so far, the CS-FEM-DSG3 has been only developed for analyzing intact structures without possessing internal cracks. The paper hence tries to extend the CS-FEM-DSG3 for free vibration analysis of cracked Reissner-Mindlin shells by integrating the original CS-FEM-DSG3 with discontinuous and crack−tip singular enrichment functions of the extended finite element method (XFEM) to give a so-called extended cell-based smoothed discrete shear gap method (XCS-FEM-DSG3). The accuracy and reliability of the novel XCS-FEM-DSG3 for free vibration analysis of cracked Reissner-Mindlin shells are investigated through solving three numerical examples and comparing with commercial software ANSYS.

关键词： cracked Reissner-Mindlin shell free vibration analysis cell-based smoothed discrete shear gap method (CS-FEM-DSG3) extended cell-based smoothed discrete shear gap method (XCS-FEM-DSG3) smoothed finite element methods (SFEM)

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Static analysis of corrugated panels using homogenization models and a cell-based smoothed mindlin plateelement (CS-MIN3)

Nhan NGUYEN-MINH, Nha TRAN-VAN, Thang BUI-XUAN, Trung NGUYEN-THOI

《结构与土木工程前沿（英文）》 2019年第13卷第2期页码 251-272 doi: 10.1007/s11709-017-0456-0

摘要： Homogenization is a promising approach to capture the behavior of complex structures like corrugated panels. It enables us to replace high-cost shell models with stiffness-equivalent orthotropic plate alternatives. Many homogenization models for corrugated panels of different shapes have been proposed. However, there is a lack of investigations for verifying their accuracy and reliability. In addition, in the recent trend of development of smoothed finite element methods, the cell-based smoothed three-node Mindlin plate element (CS-MIN3) based on the first-order shear deformation theory (FSDT) has been proposed and successfully applied to many analyses of plate and shell structures. Thus, this paper further extends the CS-MIN3 by integrating itself with homogenization models to give homogenization methods. In these methods, the equivalent extensional, bending, and transverse shear stiffness components which constitute the equivalent orthotropic plate models are represented in explicit analytical expressions. Using the results of ANSYS and ABAQUS shell simulations as references, some numerical examples are conducted to verify the accuracy and reliability of the homogenization methods for static analyses of trapezoidally and sinusoidally corrugated panels.

关键词： homogenization corrugated panel asymptotic analysis smoothed finite element method (S-FEM) cell-based smoothed three-node Mindlin plate element (CS-MIN3)

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The smoothed finite element method (S-FEM): A framework for the design of numerical models for desired

Gui-Rong Liu

《结构与土木工程前沿（英文）》 2019年第13卷第2期页码 456-477 doi: 10.1007/s11709-019-0519-5

摘要：

The smoothed finite element method (S-FEM) was originated by G R Liu by combining some meshfree techniques with the well-established standard finite element method (FEM). It has a family of models carefully designed with innovative types of smoothing domains. These models are found having a number of important and theoretically profound properties. This article first provides a concise and easy-to-follow presentation of key formulations used in the S-FEM. A number of important properties and unique features of S-FEM models are discussed in detail, including 1) theoretically proven softening effects; 2) upper-bound solutions; 3) accurate solutions and higher convergence rates; 4) insensitivity to mesh distortion; 5) Jacobian-free; 6) volumetric-locking-free; and most importantly 7) working well with triangular and tetrahedral meshes that can be automatically generated. The S-FEM is thus ideal for automation in computations and adaptive analyses, and hence has profound impact on AI-assisted modeling and simulation. Most importantly, one can now purposely design an S-FEM model to obtain solutions with special properties as wish, meaning that S-FEM offers a framework for design numerical models with desired properties. This novel concept of numerical model on-demand may drastically change the landscape of modeling and simulation. Future directions of research are also provided.

关键词： computational method finite element method smoothed finite element method strain smoothing technique smoothing domain weakened weak form solid mechanics softening effect upper bound solution

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A “Sequential Design of Simulations” approach for exploiting and calibrating discrete element simulations

《化学科学与工程前沿（英文）》 2022年第16卷第6期页码 874-885 doi: 10.1007/s11705-021-2131-1

摘要： The flow behaviours of cohesive particles in the ring shear test were simulated and examined using discrete element method guided by a design of experiments methodology. A full factorial design was used as a screening design to reveal the effects of material properties of partcles. An augmented design extending the screening design to a response surface design was constructed to establish the relations between macroscopic shear stresses and particle properties. It is found that the powder flow in the shear cell can be classified into four regimes. Shear stress is found to be sensitive to particle friction coefficient, surface energy and Young’s modulus. A considerable fluctuation of shear stress is observed in high friction and low cohesion regime. In high cohesion regime, Young’s modulus appears to have a more significant effect on the shear stress at the point of incipient flow than the shear stress during the pre-shear process. The predictions from response surface designs were validated and compared with shear stresses measured from the Schulze ring shear test. It is found that simulations and experiments showed excellent agreement under a variety of consolidation conditions, which verifies the advantages and feasibility of using the proposed “Sequential Design of Simulations” approach.

关键词： discrete element method cohesive materials parameter calibration ring shear cell design of experiments

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The regulatory sciences for stem cell-based medicinal products

null

《医学前沿（英文）》 2014年第8卷第2期页码 190-200 doi: 10.1007/s11684-014-0323-5

摘要：

Over the past few years, several new achievements have been made from stem cell studies, many of which have moved up from preclinical stages to early, or from early to middle or late, stages thanks to relatively safe profile and preliminary evidence of effectiveness. Moreover, some stem cell-based products have been approved for marketing by different national regulatory authorities. However, many critical issues associated mainly with incomplete understanding of stem cell biology and the relevant risk factors, and lack of effective regulations still exist and need to be urgently addressed, especially in countries where establishment of appropriate regulatory system just commenced. More relevantly, the stem cell regulatory sciences need to be established or improved to more effectively evaluate quality, safety and efficacy of stem cell products, and for building up the appropriate regulatory framework. In this review, we summarize some new achievements in stem cell studies, especially the preclinical and clinical studies, the existing regulations, and the associated challenges, and we then propose some considerations for improving stem cell regulatory sciences with a goal of promoting the steadfast growth of the well-regulated stem cell therapies abreast of evolvement of stem cell sciences and technologies.

关键词： stem cell-based medicinal products (SCMPs) stem cell therapy (SCT) safety effectiveness standards guidelines regulatory science

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MAS-based production scheduling system for manufacturing cell-based workshop

CHU Hong-yan, CAO Quan-jun, FEI Ren-yuan

《机械工程前沿（英文）》 2006年第1卷第4期页码 375-380 doi: 10.1007/s11465-006-0043-x

摘要： The task of production scheduling is to determine the detailed machining path, time, machine tool, etc., for every work piece, according to the production objective and constraints. It is also an important part of the manufacturing system. In this paper, the manufacturing cell-based workshop is described and its scheduling system structure is established based on MAS (multi-agent system) technology. Through the negotiation and communication of each agent, the machining path is determined and the machining sequence and start time are calculated by GA (genetics algorithm). The communication among agents uses the CORBA (common object request broker architecture) technology of the OMG (Object Management Group). The CORBA-based architecture of the communication is designed and some interfaces for the communication are listed. For the genetics algorithm, chromosome coding, fitness function, parameters selection, and the basic genetics operation including selection, crossover and aberrance, are described. The scheduling system also can deal with some abnormal conditions, such as machine tool failure and urgent tasks. Finally, two scheduling examples are given.

关键词： negotiation selection multi-agent communication abnormal

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Challenges of NK cell-based immunotherapy in the new era

null

《医学前沿（英文）》 2018年第12卷第4期页码 440-450 doi: tzg@ustc.edu.cn

摘要：

Natural killer cells (NKs) have a great potential for cancer immunotherapy because they can rapidly and directly kill transformed cells in the absence of antigen presensitization. Various cellular sources, including peripheral blood mononuclear cells (PBMCs), stem cells, and NK cell lines, have been used for producing NK cells. In particular, NK cells that expanded from allogeneic PBMCs exhibit better efficacy than those that did not. However, considering the safety, activities, and reliability of the cell products, researchers must develop an optimal protocol for producing NK cells from PBMCs in the manufacture setting and clinical therapeutic regimen. In this review, the challenges on NK cell-based therapeutic approaches and clinical outcomes are discussed.

关键词： natural killer cells immunotherapy adoptive transfer genetic modification immune checkpoint inhibitor

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3D finite element method (FEM) simulation of groundwater flow during backward erosion piping

Kristine VANDENBOER,Vera van BEEK,Adam BEZUIJEN

《结构与土木工程前沿（英文）》 2014年第8卷第2期页码 160-166 doi: 10.1007/s11709-014-0257-7

摘要： Backward erosion piping is an important failure mechanism for cohesive water retaining structures which are founded on a sandy aquifer. At present, the prediction models for safety assessment are often based on 2D assumptions. In this work, a 3D numerical approach of the groundwater flow leading to the erosion mechanism of backward erosion piping is presented and discussed. Comparison of the 2D and 3D numerical results explicitly demonstrates the inherent 3D nature of the piping phenomenon. In addition, the influence of the seepage length is investigated and discussed for both piping initiation and piping progression. The results clearly indicate the superiority of the presented 3D numerical model compared to the established 2D approach. Moreover, the 3D numerical results enable a better understanding of the complex physical mechanism involved in backward erosion piping and thus can lead to a significant improvement in the safety assessment of water retaining structures.

关键词： backward erosion piping groundwater flow 3D finite element method (FEM)

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3D mode discrete element method with the elastoplastic model

Wei HU, Feng JIN, Chong ZHANG, Jinting WANG

《结构与土木工程前沿（英文）》 2012年第6卷第1期页码 57-68 doi: 10.1007/s11709-012-0139-9

摘要： The three-dimensional mode-deformable discrete element method (3MDEM) is an extended distinct element approach under the assumptions of small strain, finite displacement, and finite rotation of blocks. The deformation of blocks is expressed by the combination of the deformation modes in 3MDEM. In this paper, the elastoplastic constitutive relationship of blocks is implemented on the 3MDEM platform to simulate the integrated process from elasticity to plasticity and finally to fracture. To overcome the shortcomings of the conventional criterion for contact fracturing, a new criterion based on plastic strain is introduced. This approach is verified by two numerical examples. Finally, a cantilever beam is simulated as a comprehensive case study, which went through elastic, elastoplastic, and discontinuous fracture stages.

关键词： mode discrete element method elastoplastic numerical method discontinuum contact

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A dynamic model of mobile concrete pump boom based on discrete time transfer matrix method

Wu REN, Yunxin WU, Zhaowei ZHANG

《机械工程前沿（英文）》 2013年第8卷第4期页码 360-366 doi: 10.1007/s11465-013-0280-8

摘要：

Mobile concrete pump boom is typical multi-body large-scale motion manipulator. Due to posture constantly change in working process, kinematic rule and dynamic characteristic are difficult to solve. A dynamics model of a mobile concrete pump boom is established based on discrete time transfer matrix method (DTTMM). The boom system is divided into sub-structure A and sub-structure B. Sub-structure A is composed by the 1st boom and hydraulic actuator as well as the support. And sub-structure B is consists of the other three booms and corresponding hydraulic actuators. In the model, the booms and links are regarded as rigid elements and the hydraulic cylinders are equivalent to spring-damper. The booms are driven by the controllable hydraulic actuators. The overall dynamic equation and transfer matrix of the model can be assembled by sub-structures A and B. To get a precise result, step size and integration parameters are studied then. Next the tip displacement is calculated and compared with the result of ADAMS software. The displacement and rotation angle curves of the proposed method fit well with the ADAMS model. Besides it is convenient in modeling and saves time. So it is suitable for mobile concrete pump boom real-time monitoring and dynamic analysis. All of these provide reference to boom optimize and engineering application of such mechanisms.

关键词： multi-body mobile concrete pump boom discrete time transfer matrix method (DTTMM) kinematic dynamic tip displacement

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FEM-based strain analysis study for multilayer sheet forming process

Rongjing ZHANG,Lihui LANG,Rizwan ZAFAR

《机械工程前沿（英文）》 2015年第10卷第4期页码 373-379 doi: 10.1007/s11465-015-0371-9

摘要：

Fiber metal laminates have many advantages over traditional laminates (e.g., any type of fiber and resin material can be placed anywhere between the metallic layers without risk of failure of the composite fabric sheets). Furthermore, the process requirements to strictly control the temperature and punch force in fiber metal laminates are also less stringent than those in traditional laminates. To further explore the novel method, this study conducts a finite element method-based (FEM-based) strain analysis on multilayer blanks by using the 3A method. Different forming modes such as wrinkling and fracture are discussed by using experimental and numerical studies. Hydroforming is used for multilayer forming. The Barlat 2000 yield criteria and DYNAFORM/LS-DYNA are used for the simulations. Optimal process parameters are determined on the basis of fixed die-binder gap and variable cavity pressure. The results of this study will enhance the knowledge on the mechanics of multilayer structures formed by using the 3A method and expand its commercial applications.

关键词： finite element method (FEM) strain analysis multilayer sheet forming

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Buffer capacity of granular matter to impact of spherical projectile based on discrete element method

Ying YAN, Pengfei LI, Shunying JI

《结构与土木工程前沿（英文）》 2013年第7卷第1期页码 50-54 doi: 10.1007/s11709-013-0186-x

摘要： Granular matter possesses impact-absorbing property due to its energy dissipation character. To investigate the impact-absorbing capacity of granular matter, the discrete element method (DEM) is adopted to simulate the impact of a spherical projectile on to a granular bed. The dynamic responses of the projectile are obtained for both thin and thick granular bed. The penetration depth of the projectile and the first impact peak are investigated with different bed thicknesses and impact velocities. Determining a suitable bed thickness is crucial to the buffering effect of granular matter. The first impact peak is independent of bed thickness when the thickness is larger than the critical thickness.

关键词： granular matter impact peak buffer capacity discrete element method critical thickness

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Gradient-based compressive image fusion

Yang CHEN,Zheng QIN

《信息与电子工程前沿（英文）》 2015年第16卷第3期页码 227-237 doi: 10.1631/FITEE.1400217

摘要： We present a novel image fusion scheme based on gradient and scrambled block Hadamard ensemble (SBHE) sampling for compressive sensing imaging. First, source images are compressed by compressive sensing, to facilitate the transmission of the sensor. In the fusion phase, the image gradient is calculated to reflect the abundance of its contour information. By compositing the gradient of each image, gradient-based weights are obtained, with which compressive sensing coefficients are achieved. Finally, inverse transformation is applied to the coefficients derived from fusion, and the fused image is obtained. Information entropy (IE), Xydeas’s and Piella’s metrics are applied as non-reference objective metrics to evaluate the fusion quality in line with different fusion schemes. In addition, different image fusion application scenarios are applied to explore the scenario adaptability of the proposed scheme. Simulation results demonstrate that the gradient-based scheme has the best performance, in terms of both subjective judgment and objective metrics. Furthermore, the gradient-based fusion scheme proposed in this paper can be applied in different fusion scenarios.

关键词： Compressive sensing (CS) Image fusion Gradient-based image fusion CS-based image fusion

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Application of coupled multi-body dynamics–discrete element method for optimization of particle damper

Danhui DAN, Qianqing WANG, Jiongxin GONG

《结构与土木工程前沿（英文）》 2021年第15卷第1期页码 244-252 doi: 10.1007/s11709-021-0696-x

摘要： With the application of the particle damping technology to cable vibration attenuation, the rootless cable damper overcomes the limit in installation height of existing dampers. Damping is achieved through energy dissipation by collisions and friction. In this paper, a coupled multi-body dynamics–discrete element method is proposed to simulate the damping of the damper–cable system under a harmonic excitation. The analyses are done by combining the discrete element method in EDEM and multi-body dynamics in ADAMS. The simulation results demonstrate the damping efficiency of rootless particle damper under different excitations and reveal the influence of the design parameters on its performance, including the filling ratio, particle size, coefficient of restitution, and coefficient of friction.

关键词： granular material vibration control discrete element method particle damper cable vibration

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Discrete ordinates method for three-dimensional neutron transport equation based on unstructured-meshes

JU Haitao, WU Hongchun, YAO Dong, XIAN Chunyu

《能源前沿（英文）》 2008年第2卷第2期页码 179-182 doi: 10.1007/s11708-008-0024-3

摘要： A discrete ordinates method for a three-dimensional first-order neutron transport equation based on unstructured-meshes that avoids the singularity of the second-order neutron transport equation in void regions was derived. The finite element variation equation was obtained using the least-squares method. A three-dimensional transport calculation code was developed. Both the triangular-z and the tetrahedron elements were included. The numerical results of some benchmark problems demonstrated that this method can solve neutron transport problems in unstructured-meshes very well. For most problems, the error of the eigenvalue and the angular flux is less than 0.3% and 3.0% respectively.

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标题作者时间类型操作

An extended cell-based smoothed discrete shear gap method (XCS-FEM-DSG3) for free vibration analysis

M. H. NGUYEN-THOI,L. Le-ANH,V. Ho-HUU,H. Dang-TRUNG,T. NGUYEN-THOI

期刊论文

Static analysis of corrugated panels using homogenization models and a cell-based smoothed mindlin plateelement (CS-MIN3)

Nhan NGUYEN-MINH, Nha TRAN-VAN, Thang BUI-XUAN, Trung NGUYEN-THOI

期刊论文

The smoothed finite element method (S-FEM): A framework for the design of numerical models for desired

Gui-Rong Liu

期刊论文

A “Sequential Design of Simulations” approach for exploiting and calibrating discrete element simulations