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Two-scale modeling of granular materials: A FEM-FEM approach

Yun-Zhu CAI, Yu-Ching WU

《结构与土木工程前沿（英文）》 2013年第7卷第3期页码 304-315 doi: 10.1007/s11709-013-0213-y

摘要： In the present paper, a homogenization-based two-scale FEM-FEM model is developed to simulate compactions of visco-plastic granular assemblies. The granular structure consisting of two-dimensional grains is modeled by the microscopic finite element method at the small-scale level, and the homogenized viscous assembly is analyzed by the macroscopic finite element method at large-scale level. The link between scales is made using a computational homogenization method. The two-scale FEM-FEM model is developed in which each particle is treated individually with the appropriate constitutive relations obtained from a representative volume element, kinematic conditions, contact constraints, and elimination of overlap satisfied for every particle. The method could be used in a variety of problems that can be represented using granular media.

关键词： homogenization two-scale representative volume element compaction granular assembly finite element method

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Application of granular solid hydrodynamics to a well-graded unbound granular material undergoing triaxial

Shixiong SONG, Qicheng SUN, Feng JIN, Chuhan ZHANG

《结构与土木工程前沿（英文）》 2013年第7卷第1期页码 83-88 doi: 10.1007/s11709-012-0148-8

摘要： Unbound granular materials (UGMs) are widely used as a base or a subbase in pavement construction. They are generally well graded and exhibit a higher peak strength than that of conventional cohesionless granular materials. By using a simplified version of granular solid hydrodynamics (GSH), a set of GSH material constants is determined for a UGM material. The deviatoric stress and volumetric strain caused by triaxial compression are calculated and then compared with experimental data. The results indicate that the GSH theory is able to describe such a special type of granular materials.

关键词： granular solid hydrodynamics unbound granular material (UGM) triaxial tests

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Assembly of biosynthetic pathways in

Lidan Ye,Xiaomei Lv,Hongwei Yu

《化学科学与工程前沿（英文）》 2017年第11卷第1期页码 126-132 doi: 10.1007/s11705-016-1597-8

摘要： A robust and versatile tool for multigene pathway assembly is a key to the biosynthesis of high-value chemicals. Here we report the rapid construction of biosynthetic pathways in using a marker recyclable integrative toolbox (pUMRI) developed in our research group, which has features of ready-to-use, convenient marker recycling, arbitrary element replacement, shuttle plasmid, auxotrophic marker independence, GAL regulation, and decentralized assembly. Functional isoprenoid biosynthesis pathways containing 4–11 genes with lengths ranging from ~10 to ~22 kb were assembled using this toolbox within 1–5 rounds of reiterative recombination. In combination with GAL-regulated metabolic engineering, high production of isoprenoids (e.g., 16.3 mg?g dcw carotenoids) was achieved. These results demonstrate the wide range of application and the efficiency of the pUMRI toolbox in multigene pathway construction of .

关键词： pathway assembly toolbox reiterative recombination S. cerevisiae biosynthesis

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A novel task-oriented framework for dual-arm robotic assembly task

《机械工程前沿（英文）》 2021年第16卷第3期页码 528-545 doi: 10.1007/s11465-021-0638-2

摘要： In industrial manufacturing, the deployment of dual-arm robots in assembly tasks has become a trend. However, making the dual-arm robots more intelligent in such applications is still an open, challenging issue. This paper proposes a novel framework that combines task-oriented motion planning with visual perception to facilitate robot deployment from perception to execution and finish assembly problems by using dual-arm robots. In this framework, visual perception is first employed to track the effects of the robot behaviors and observe states of the workpieces, where the performance of tasks can be abstracted as a high-level state for intelligent reasoning. The assembly task and manipulation sequences can be obtained by analyzing and reasoning the state transition trajectory of the environment as well as the workpieces. Next, the corresponding assembly manipulation can be generated and parameterized according to the differences between adjacent states by combining with the prebuilt knowledge of the scenarios. Experiments are set up with a dual-arm robotic system (ABB YuMi and an RGB-D camera) to validate the proposed framework. Experimental results demonstrate the effectiveness of the proposed framework and the promising value of its practical application.

关键词： dual-arm assembly AI reasoning intelligent system task-oriented motion planning visual perception

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Mesoscopic properties of dense granular materials: An overview

Qicheng SUN, Feng JIN, Guohua ZHANG

《结构与土木工程前沿（英文）》 2013年第7卷第1期页码 1-12 doi: 10.1007/s11709-013-0184-z

摘要： A granular material is a conglomeration of discrete solid particles. It is intrinsically athermal because its dynamics always occur far from equilibrium. In highly excited gaseous states, it can safely be assumed that only binary interactions occur and a number of kinetic theories have been successfully applied. However, for granular flows and solid-like states, the theory is still poorly understood because of the internally correlated structures, such as particle clusters and force networks. The current theory is that the mesoscale characteristics define the key differences between granular materials and homogeneous solid materials. Widespread interest in granular materials has arisen among physicists, and significant progress has been made, especially in understanding the jamming phase diagram and the characteristics of the jammed phase. In this paper, the underlying physics of the mesoscale structure is discussed in detail. A multiscale framework is then proposed for dense granular materials.

关键词： granular matter macroscopic structure jamming phase transition

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Effects of shear force on formation and properties of anoxic granular sludge in SBR

Xinyan ZHANG, Binbin WANG, Qingqing HAN, Hongmei ZHAO, Dangcong PENG

《环境科学与工程前沿（英文）》 2013年第7卷第6期页码 896-905 doi: 10.1007/s11783-013-0539-7

摘要： This paper reports the effects of shear force on anoxic granular sludge in sequencing batch reactors (SBR). The study was carried out in two SBRs (SBR1 and SBR2) in which sodium acetate (200 mg COD·L ) was used as the sole substrate and sodium nitrate (40 mgNO -N·L ) was employed as the electron acceptor. The preliminary objective of this study was to cultivate anoxic granules in the SBR in order to investigate the effects of shear force on the formation of anoxic granular sludge and to compare the properties of anoxic sludge in the SBR. This study reports new results for the values of average velocity gradient, a measure of the applied shear force, which was varied in the two SBRs (3.79 s and 9.76 s for SBR1 and SBR2 respectively). The important findings of this research highlight the dual effects of shear force on anoxic granules. A low shear force can produce large anoxic granules with high activity and poor settling ability, whereas higher shear forces produce smaller granules with better settling ability and lower activity. The results of this study show that the anoxic granulation is closely related to the strength of the shear force. For high shear force, this research demonstrated that: 1) granules with smaller diameters, high density and good settling ability were formed in the reactor, and 2) granular sludge formed faster than it did in the low shear force reactor (41days versus 76 days). Once a steady-state has been achieved, the nitrate and COD removal rates were found to be 98% and 80%, respectively. For low shear force, such as was applied in SBR1, this research demonstrated that: 1) the activity of anoxic granular sludge in low shear force was higher than that in high shear force, 2) higher amount of soluble microbial products (SMPs) were produced, and 3) large pores were observed inside the larger granules, which are beneficial for nitrogen gas diffusion. Electron microscopic examination of the anoxic granules in both reactors showed that the morphology of the granules was ellipsoidal with a clear outline. Coccus and rod-shaped bacteria were wrapped by filamentous bacteria on the surface of granule.

关键词： denitrification anoxic granular sludge sequencing batch reactors (SBR) shear force

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Pareto lexicographic α-robust approach and its application in robust multi objective assembly line balancing

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《机械工程前沿（英文）》 2014年第9卷第3期页码 257-264 doi: 10.1007/s11465-014-0294-x

摘要：

Robustness in most of the literature is associated with min-max or min-max regret criteria. However, these criteria of robustness are conservative and therefore recently new criteria called, lexicographic α-robust method has been introduced in literature which defines the robust solution as a set of solutions whose quality or jth largest cost is not worse than the best possible jth largest cost in all scenarios. These criteria might be significant for robust optimization of single objective optimization problems. However, in real optimization problems, two or more than two conflicting objectives are desired to optimize concurrently and solution of multi objective optimization problems exists in the form of a set of solutions called Pareto solutions and from these solutions it might be difficult to decide which Pareto solution can satisfy min-max, min-max regret or lexicographic α-robust criteria by considering multiple objectives simultaneously. Therefore, lexicographic α-robust method which is a recently introduced method in literature is extended in the current research for Pareto solutions. The proposed method called Pareto lexicographic α-robust approach can define Pareto lexicographic α-robust solutions from different scenarios by considering multiple objectives simultaneously. A simple example and an application of the proposed method on a simple problem of multi objective optimization of simple assembly line balancing problem with task time uncertainty is presented to get their robust solutions. The presented method can be significant to implement on different multi objective robust optimization problems containing uncertainty.

关键词： Pareto lexicographic α-robust assembly line balancing

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Force fluctuations in sheared granular disks

Mingbo YUAN, Qicheng SUN, Feng JIN

《结构与土木工程前沿（英文）》 2013年第7卷第1期页码 46-49 doi: 10.1007/s11709-013-0189-7

摘要： The internal structure established within granular materials, often observed as force chains, is dominant in controlling bulk mechanical properties. We designed a two-dimensional Hele-Shaw cell to contain photoelastic disks, and two servos were used on the top and right boundaries individually. We experimentally monitored the fluctuations in force on the top plate while slowing the shearing of the well-confined disks and keeping the right boundary at a contact-confined force of 0.2 kN. The particle rearrangements were found to correspond to bulk force drops and were observed in a localized zone with a length of approximately 5 particle diameters. These results help reveal the structure and mechanics of granular materials, and further investigations are ongoing.

关键词： granular matter force chain stick and slip

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Assembly design system based on engineering connection

Wensheng YIN

《机械工程前沿（英文）》 2016年第11卷第4期页码 423-432 doi: 10.1007/s11465-016-0382-1

摘要：

An assembly design system is an important part of computer-aided design systems, which are important tools for realizing product concept design. The traditional assembly design system does not record the connection information of production on the engineering layer; consequently, the upstream design idea cannot be fully used in the downstream design. An assembly design model based on the relationship of engineering connection is presented. In this model, all nodes are divided into two categories: The component and the connection. Moreover, the product is constructed on the basis of the connection relationship of the components. The model is an And/Or graph and has the ability to record all assembly schemes. This model records only the connection information that has engineering application value in the product design. In addition, this model can significantly reduce the number of combinations, and is very favorable for the assembly sequence planning in the downstream. The system contains a connection knowledge system that can be mapped to the connection node, and the connection knowledge obtained in practice can be returned to the knowledge system. Finally, VC++6.0 is used to develop a prototype system called Connect-based Assembly Planning (CAP). The relationship between the CAP system and the commercial assembly design system is also established.

关键词： product design assembly design engineering connection assembly sequence planning

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Visualization of force networks in 2D dense granular materials

Jianguo LIU, Qicheng SUN, Feng JIN,

《结构与土木工程前沿（英文）》 2010年第4卷第1期页码 109-115 doi: 10.1007/s11709-010-0003-8

摘要： Dense granular matter is a conglomeration of discrete solid and closely packed particles. As subjected to external loadings, the stress is largely transmitted by heavily stressed chains of particles forming a sparse network of larger contact forces. To understand the structure and evolution of force chains, a photoelastic technique was improved for determining stresses and strains in the assemblies of photoelastic granular disks in this paper. A two-dimensional vertical slab was designed. It contains 7200 polydispersed photoelastic disks and is subjected to a localized probe penetrating at the top of the slab to mimic the cone penetration test. The interparticle contact force distribution was found a peak around the mean value, a roughly exponential tail for greater force and a dip toward zero for smaller force. The force chain network around the probe tip was depicted, and the contact angle distribution of particles in force chains was found to be well aligned in the directions of major principal stress.

关键词： granular matter force chain multiscale modeling

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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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Enzyme-instructed self-assembly of peptides containing phosphoserine to form supramolecular hydrogels

Jie Zhou, Xuewen Du, Jiaqing Wang, Natsuko Yamagata, Bing Xu

《化学科学与工程前沿（英文）》 2017年第11卷第4期页码 509-515 doi: 10.1007/s11705-017-1613-7

摘要： Enzyme-instructed self-assembly (EISA) offers a facile approach to explore the supramolecular assemblies of small molecules in cellular milieu for a variety of biomedical applications. One of the commonly used enzymes is phosphatase, but the study of the substrates of phosphatases mainly focuses on the phosphotyrosine containing peptides. In this work, we examine the EISA of phosphoserine containing small peptides for the first time by designing and synthesizing a series of precursors containing only phosphoserine or both phosphoserine and phosphotyrosine. Conjugating a phosphoserine to the -terminal of a well-established self-assembling peptide backbone, (naphthalene-2-ly)-acetyl-diphenylalanine (NapFF), affords a novel hydrogelation precursor for EISA. The incorporation of phosphotyrosine, another substrate of phosphatase, into the resulting precursor, provides one more enzymatic trigger on a single molecule, and meanwhile increases the precursors’ propensity to aggregate after being fully dephosphorylated. Exchanging the positions of phosphorylated serine and tyrosine in the peptide backbone provides insights on how the specific molecular structures influence self-assembling behaviors of small peptides and the subsequent cellular responses. Moreover, the utilization of D-amino acids largely enhances the biostability of the peptides, thus providing a unique soft material for potential biomedical applications.

关键词： enzyme-instructed self-assembly phosphoserine phosphatase supramolecular hydrogel

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Concept and application of anaerobic suspended granular sludge bed (SGSB) reactor for wastewater treatment

Mingxia ZHENG,Zhong YAN,Jiane ZUO,Kaijun WANG

《环境科学与工程前沿（英文）》 2014年第8卷第5期页码 797-804 doi: 10.1007/s11783-013-0597-x

摘要： Bed expansion serves an important function in the design and operation of an upflow anaerobic reactor. An analysis of the flow pattern of expanded granular sludge bed (EGSB) reactors shows that most EGSB reactors do not behave as expanded bed reactors, as is widely perceived. Rather, these reactors behave as fluidized bed reactors based on the classic chemical reactor theory. In this paper, four bed expansion modes, divided as static bed, expanded bed, suspended bed, and fluidized bed, for bioreactors are proposed. A high-rate anaerobic suspended granular sludge bed (SGSB) reactor was then developed. The SGSB reactor is an upflow anaerobic reactor, and its expansion degree can be easily controlled within a range to maintain the suspended status of the sludge bed by controlling upflow velocity. The results of the full-scale reactor confirmed that the use of SGSB reactors is advantageous. The full-scale SGSB reactor runs stably and achieves high COD removal efficiency (about 90%) at high loading rates (average 40 kg-COD·m ·d , maximum to 52 kg-COD·m ·d ) based on the SGSB theory, and its expansion degree is between 22% and 37%.

关键词： expansion characteristic high-rate bioreactor anaerobic suspended granular sludge bed expanded granular sludge bed reactor

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Methanogenic community structure in simultaneous methanogenesis and denitrification granular sludge

Yujiao Sun, Juanjuan Zhao, Lili Chen, Yueqiao Liu, Jiane Zuo

《环境科学与工程前沿（英文）》 2018年第12卷第4期 doi: 10.1007/s11783-018-1067-2

摘要：

• UASB with SMD granules was operated with high removal efficiency of COD and NO₃^--N.

• Methanosaetaceae was absolute predominant methanogen in SMD granules.

• The methanogen quantity and activity decreased as C/N decreased from 20:1 to 5:1.

• Bacterial community succession happened with C/N decreasing.

关键词： Simultaneous methanogenesis and denitrification (SMD) Methanogens Community structure Diversity index Granular sludge

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Development of a constitutive model for rockfills and similar granular materials based on the disturbed

Mehdi VEISKARAMI, Ali GHORBANI, Mohammadreza ALAVIPOUR

《结构与土木工程前沿（英文）》 2012年第6卷第4期页码 365-378 doi: 10.1007/s11709-012-0178-2

摘要： Behavior of rockfills was investigated experimentally and theoretically. A series of standard triaxial compression tests were carried out on a quarried rockfill material at different stress levels. It was found that both the stress level and the shear stress ratio, like most of granular materials, controls the behavior of rockfill materials. At lower shear stress ratios the behavior is much more similar to a nonlinear elastic solid. When the shear stress goes further, the stress-strain curve shows an elasto-plastic behavior which suggests using the disturbed state concept to develop a constitutive model to predict the stress-strain behavior. The presented constitutive model complies reasonably with the experimental data.

关键词： constitutive model granular material rockfill plasticity disturbed state concept stress level