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DEM study on effect of particle roundness on biaxial shearing of sand

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Underground Space 2021年第6期6卷 678-694页

作者： mengmeng wu Linghong Xiong Jianfeng Wang Department of Architecture and Civil Engineering City University of Hong KongHong KongChina Shenzhen Research Institute of City University of Hong Kong ShenzhenChina

In this study,discrete element method(DEM)simulations of a biaxial test were used to examine the effect of particle roundness on the mechanical behavior of sands at both the macro and micro ***,a stack of microcomputed tomography images were binarized,segmented,and labeled using advanced image processing and analysis ***,a spherical harmonic(SH)analysis,which involves a complete set of orthogonal functions,was implemented to rebuild the natural particle ***,five templates of virtual particles were built in a DEM simulation,four of which were obtained from SH degrees of 3,8,12,and 15,and one template was an elementary sphere.A flexible membrane was numerically generated to allow the material to deform freely under a prescribed confining ***,the effect of particle roundness on the mechanical properties of granular materials was investigated and *** shear bands were found to intersect,forming an X shape in both the rotation and displacement ***,a lower particle roundness results in higher deviatoric stress and stronger dilation in the volumetric change.A decrease in particle roundness leads to less rotation of particles despite a higher displacement *** addition,a larger SH degree leads to smaller normalized contact forces of the *** implies that decreasing the roundness results in higher anisotropy of the contact forces.

关键词： Grain shape Roundness Flexible membrane Spherical harmonic analysis Discrete element method

Strength criterion effect of the translator and destabilization model of gas-bearing coal seam

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International Journal of Mining Science and Technology 2019年第2期29卷 327-333页

作者： Gang Wang Rui Wang mengmeng wu Cheng Fan Xiang Song Mine Disaster Prevention and Control-Ministry of State Key Laboratory Breeding Base Shandong University of Science & Technology College of Mining and Safety Engineering Shandong University of Science & Technology Department of Civil and Architectural Engineering City University of Hong Kong

Coal seam destabilization inflicts damage to equipment, causes property loss and personnel casualties,and severely threatens mining safety and efficient production. To further understand this destabilization based on the basic theory of Lippmann seam destabilization, a mathematical model was introduced for gas pressure distribution by considering intermediate principal stress and support ***, we established a translation model suitable for the entire roadway coal seam with rocky roof and floor by applying the unified form of yield criterion in the state of plane strain. We also obtained the analytic expressions of coal seam stress distribution on both sides of the roadway and the widths of plastic and disturbance zones. Afterward, we analyzed several typical cases with different material yield criteria, obtained the plastic zone widths of the coal seam under different gas pressures, and assessed the effects of support resistance, roadway size, and coal strength on coal seam destabilization. Results showed that: the results obtained on the basis of Wilson and Mohr–Coulomb criteria are considerably conservative, and the use of Druker–Prager criteria to evaluate the rockburst-induced coal seam destabilization is safer than the use of the two other criteria; coal seam stability is correlated with gas pressure;and high-pressure gas accelerates the coal seam destabilization.

关键词： Coal seam destabilization Strength criterion effect Gas Stress distribution

Whole genome sequencing and its applications in medical genetics

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Frontiers of Electrical and Electronic Engineering in China 2016年第2期4卷 115-128页

作者： Jiaxin wu mengmeng wu Ting Chen Rui Jiang MOE Key Laboratory of Bioinformatics Bioinformatics Division and Center for Synthetic&Systems BiologyTNLIST Department of Automation Tsinghua UniversityBeijing 100084China

Fundamental improvement was made for genome sequencing since the next-generation sequencing （NGS） came out in the 2000s. The newer technologies make use of the power of massively-parallel short-read DNA sequencing, genome alignment and assembly methods to digitally and rapidly search the genomes on a revolutionary scale, which enable large-scale whole genome sequencing （WGS） accessible and practical for researchers. Nowadays, whole genome sequencing is more and more prevalent in detecting the genetics of diseases, studying causative relations with cancers, making genome-level comparative analysis, reconstruction of human population history, and giving clinical implications and instructions. In this review, we first give a typical pipeline of whole genome sequencing, including the lab template preparation, sequencing, genome assembling and quality control, variants calling and annotations. We compare the difference between whole genome and whole exome sequencing （WES）, and explore a wide range of applications of whole genome sequencing for both mendelian diseases and complex diseases in medical genetics. We highlight the impact of whole genome sequencing in cancer studies, regulatory variant analysis, predictive medicine and precision medicine, as well as discuss the challenges of the whole genome sequencing.

关键词： whole genome sequencing whole exome sequencing next-generation sequencing non-coding regulatoryvariant

The drying of liquid droplets

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Chinese Physics B 2020年第9期29卷 435-442页

作者： Zechao Jiang Xiuyuan Yang mengmeng wu Xingkun Man Center of Soft Matter Physics and Its Applications Beihang UniversityBeijing 100191China School of Physics Beihang UniversityBeijing 100191China

The drying of liquid droplets is a common phenomenon in daily life,and has long attracted special interest in scientific *** propose a simple model to quantify the shape evolution of drying *** model takes into account the friction constant between the contact line(CL)and the substrate,the capillary forces,and the evaporation *** typical evaporation processes observed in experiments,i.e.,the constant contact radius(CCR)and the constant contact angle(CCA),are demonstrated by the ***,the simple model shows complicated evaporation dynamics,for example,the CL first spreads and then recedes during *** models of no evaporation,CCR,and CCA cases are given,*** scaling law of the CL or the contact angle as a function of time obtained by analytical model is consistent with the full numerical model,and they are all subjected to experimental *** general model facilitates a quantitative understanding of the physical mechanism underlying the drying of liquid droplets.

关键词： evaporation droplets Onsager variational principle contact line motion

A transition prediction method for flow over airfoils based on high-order dynamic mode decomposition

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Chinese Journal of Aeronautics 2019年第11期32卷 2408-2421页

作者： mengmeng wu Zhonghua HAN Han NIE Wenping SONG Soledad Le CLAINCHE Esteban FERRER School of Aeronautics Northwestern Poly technical UniversityX i’an 710072China ETSIAE-UPM School of AeronauticsUniversidad Politecnica de MadridPza Cardenal Cisneros 3Spain

This article presents a novel approach for predicting transition locations over airfoils,which are used to activate turbulence model in a Reynolds-averaged Navier-Stokes flow *** approach combines Dynamic Mode Decomposition(DMD)with e^*** core idea is to use a spatial DMD analysis to extract the modes of unstable perturbations from a steady flowfield and substitute the local Linear Stability Theory(LST)analysis to quantify the spatial growth of Tollmien–Schlichting(TS)*** is assumed to take place at the stream-wise location where the most amplified mode’s N-factor reaches a prescribed threshold and a turbulence model is activated *** improve robustness,the high-order version of DMD technique(known as HODMD)is employed.A theoretical derivation is conducted to interpret how a spatial highorder DMD analysis can extract the growth rate of the unsteady *** new method is validated by transition predictions of flows over a low-speed Natural-Laminar-Flow(NLF)airfoil NLF0416 at various angles of attack and a transonic NLF airfoil *** transition locations predicted by our HODMD/e^Nmethod agree well with experimental data and compare favorably to those obtained by some existing methods■.It is shown that the proposed method is able to predict transition locations for flows over different types of airfoils and offers the potential for application to 3D wings as well as more complex configurations.

关键词： Airfoil Dynamic mode decomposition(DMD) e^N criterion Navier-Stokes equations Transition prediction

Reinforcement effect of fiber and deoiled asphalt on high viscosity rubber/SBS modified asphalt mortar

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Petroleum Science 2014年第3期11卷 454-459页

作者： wu mengmeng Li Rui Zhang Yuzhen Wei Jianming Lv Yuchao Ding Xuemei State Key Laboratory of Heavy Oil Processing China University of Petroleum (East China)

In this paper we investigate the reinforcement mechanism of high viscosity rubber/SBS modified asphalt mortar mixed with fiber （mineral, lignin or carbon fiber） and deoiled asphalt （DOA）. The softening point, penetration and viscosity tests were conducted to characterize the engineering properties of asphalt-fiber mortar. The microstructure of fiber was observed using scanning electron microscopy （SEM）, and the results indicated that fiber can effectively improve the toughness of asphalt matrix through forming a spatial network structure, and then adhesion and stabilization of asphalt binder. The cone penetration test was designed to study the rheological property of fiber modified asphalt. The results indicated that the reinforcement effect increased with fibers and DOA fraction increasing to a certain threshold, and the optimal fiber content was dependent on the fiber type and its length. Fiber content and filler-asphalt ratio had significant effects on the softening point, penetration, viscosity and cone penetration of asphalt mortar.

关键词： Asphalt mortar fiber filler-asphalt ratio reinforcement mechanical property

Simultaneous inference of phenotype-associated genes and relevant tissues from GWAS data via Bayesian integration of multiple tissue-specific gene networks

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Journal of Molecular Cell Biology 2017年第6期9卷 436-452页

作者： mengmeng wu Zhixiang Lin Shining Ma Ting Chen Rui Jiang Wing Hung Wong Department of Computer Science Tsinghua University Beijing 100084 China Ministry of Education Key Laboratory of Bioinformatics and Bioinformatics Division Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China Department of Statistics Stanford University CA 94305 USA Department of Automation Tsinghua University Beijing 100084 China

Although genome-wide association studies （GWAS） have successfully identified thousands of genomic loci associated with hun- dreds of complex traits in the past decade, the debate about such problems as missing heritabiUty and weak interpretability has been appealing for effective computational methods to facilitate the advanced analysis of the vast volume of existing and antici- pated genetic data. Towards this goal, gene-tevel integrative GWAS analysis with the assumption that genes associated with a phenotype tend to be enriched in biological gene sets or gene networks has recently attracted much attention, due to such advan- tages as straightforward interpretation, tess multiple testing burdens, and robustness across studies. However, existing methods in this category usually exploit non-tissue-specific gene networks and thus lack the ability to utilize informative tissue-specific characteristics. To overcome this limitation, we proposed a Bayesian approach called SIGNET （Simultaneously Inference of GeNEs and Tissues） to integrate GWAS data and multiple tissue-specific gene networks for the simultaneous inference of phenotype- associated genes and relevant tissues. Through extensive simulation studies, we showed the effectiveness of our method in find- ing both associated genes and relevant tissues for a phenotype. In applications to real GWAS data of 14 complex phenotypes, we demonstrated the power of our method in both deciphering genetic basis and discovering biological insights of a phenotype. With this understanding, we expect to see SIGNET as a valuable tool for integrative GWAS analysis, thereby boosting the preven- tion, diagnosis, and treatment of human inherited diseases and eventually facilitating precision medicine.

关键词： GWAS tissue-specific gene networks Markov random field

ASB3 knockdown promotes mitochondrial apoptosis via activating the interdependent cleavage of Beclin1 and caspase-8 in hepatocellular carcinoma

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Science China(Life Sciences) 2019年第12期62卷 1692-1702页

作者： Wenli Zhang Fuchen Liu Zhihui Che mengmeng wu Zihui Tang Jie Liu Dongqin Yang Department of Digestive Diseases of Huashan Hospital Fudan UniversityShanghai 200040China The Third Department of Hepatic Surgery Eastern Hepatobiliary Surgery HospitalSecond Military Medical UniversityShanghai 200438China

Apoptosis and autophagy are distinct cellular processes that can be highly interconnected. The cross talk between the two processes is indispensable in determining the overall cell fate. Although the apoptosis-promoting effect of caspases has been demonstrated, the roles of autophagy-related proteins and even autophagy itself in regulating apoptosis remain poorly understood. In our present study, we found that downregulation of ubiquitin E3 ligase ASB3 led to enhanced mitochondrial apoptosis as well as autophagy, which synergistically promoted cell death in hepatocellular carcinoma(HCC). We observed the activation of caspase-8 and decrease of autophagy protein Beclin1 in apoptotic cells that were depleted of ASB3. Beclin1 was mainly cleaved by activated caspase-8 and active Beclin1 initiated mitochondrial apoptosis via locating its C-terminal fragment to mitochondria. In addition, knocking down of Beclin1 markedly blocked the apoptosis, indicating its essential role in the ***, our study indicated that enhanced autophagy level might be involved in the activation of caspase-8 and promote the apoptosis. Taken together, our results demonstrated that ASB3 can regulate mitochondrial pathway of apoptosis by controlling caspase-8 mediated cleavage of Beclin1 in HCC. Therefore, ASB3 may potentially serve as a novel target for HCC therapy,especially when combined with autophagy agonist.

关键词： ASB3 apoptosis Beclin1 caspase-8 autophagy liver cancer

Effect of strawberry vein banding virus and strawberry mottle virus co-infection on the growth and development of strawberry

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BIOCELL 2022年第1期46卷 263-273页

作者： LINGJIAO FAN DAN SONG YINGWEI KHOO mengmeng wu TENGFEI XU XIAOLI ZHAO HONGQING WANG College of Horticulture China Agricultural UniversityBeijing100193China State Key Laboratory of Biology of Plant Diseases and Insect Pests Institute of Plant ProtectionChinese Academy of Agricultural SciencesBeijing100193China

Strawberry mottle virus(SMoV)and strawberry vein banding virus(SVBV)cause diseases on strawberry plants,but the effect of coinfection of SMoV and SVBV on the growth,development,and defense system of strawberry(Fragaria×ananassa Duchesne)remains *** investigated the effect of SMoV and SVBV coinfection on strawberry cultivar‘Benihope’.The results showed that stem diameter,leaf size,leaf number,relative chlorophyll content,total chlorophyll content,photosynthetic parameters,and stomatal aperture of SMoV and SVBV co-infected strawberry(VIS)plants were in a weaker level than uninfected control plants,indicating that viruses inhibited the growth and photosynthesis of strawberry ***,the initiation of flowering and fruiting stages of VIS plants were delayed by about three weeks compared with the controls,and the fruiting period was shortened,demonstrating that the reproduction of VIS plants was *** quality was damaged in VIS plants due to a significant increase in fruit firmness and titratable acidity and decrease in total soluble solid content than control *** dead cells and H_(2)O_(2) accumulated along the veins of VIS leaves,and the content of abscisic acid and catalase activity significantly increased,whereas anthocyanin content was lower than that of control *** results demonstrate that SVBV and SMoV coinfection inhibits the growth and development of‘Benihope’strawberry plants,and the plants respond to viruses by regulating stomatal aperture,the accumulation of ABA and *** our knowledge,this study contributes information to understand how both viruses impair the strawberry growth and development for the first time.

关键词： Photosynthesis Flowering and fruiting period Antioxidants Plant defense