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Effects of salinity on methane gas hydrate system

Science china Earth sciences 2007年第11期50卷 1733-1745页

作者： yang dinghui1 & xu wenyue2.1 department of mathematical sciences, tsinghua university, Beijing {2., china 2.School of Earth & Atmospheric sciences, Georgia Institute of Technology, Atlanta, GA 30332. USA 1. department of mathematical {2. Tsinghua University Beijing 100084 China 2. School of Earth & Atmospheric sciences Georgia Institute of Technology Atlanta GA 30332 USA

Using an approximately analytical formation, we extend the steady state model of the pure methane hydrate system to include the salinity based on the dynamic model of the methane hydrate system. The top and bottom boundaries of the methane hydrate stability zone (MHSZ) and the actual methane hy-drate zone (MHZ), and the top of free gas occurrence are determined by using numerical methods and the new steady state model developed in this paper. Numerical results show that the MHZ thickness becomes thinner with increasing the salinity, and the stability is lowered and the base of the MHSZ is shifted toward the seafloor in the presence of salts. As a result, the thickness of actual hydrate occur-rence becomes thinner compared with that of the pure water case. On the other hand, since lower solubility reduces the amount of gas needed to form methane hydrate, the existence of salts in sea-water can actually promote methane gas hydrate formation in the hydrate stability zone. Numerical modeling also demonstrates that for the salt-water case the presence of methane within the field of methane hydrate stability is not sufficient to ensure the occurrence of gas hydrate, which can only form when the methane concentration dissolved in solution with salts exceeds the local methane solubility in salt water and if the methane flux exceeds a critical value corresponding to the rate of diffusive methane transport. In order to maintain gas hydrate or to form methane gas hydrate in marine sedi-ments, a persistent supplied methane probably from biogenic or thermogenic processes, is required to overcome losses due to diffusion and advection.

关键词： methane gas hydrate,solubility,stability of hydrate,salinity,phase equilibrium

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Remnant Paleoproterozoic Subduction or Lithospheric Drip Initiation at the Yilgarn Craton Margin: Constraints from P-wave Tomography

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Acta Geologica Sinica(English Edition) 2024年第S1期 72-74页

作者： xu Xiaobing WANG Kun yang {2. ZHAO Liang YUAN Huaiyu department of mathematical {2. Tsinghua University Institute of Geophysics China Earthquake Administration State Key Laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences university of Chinese Academy of sciences ARC Centre of Excellence for Core to Crust Fluid Systems Department of Earth and Environmental SciencesMacquarie University Centre for Exploration Targeting University of Western Australia

The Paleoproterozoic was a critical time in whether modern-style plate tectonics had become globally dominant(e.g., Wan et al., 2.2.). The Capricorn Orogen witnessed the assembly of the Pilbara and Yilgarn Cratons and an exotic microcontinent, the Glenburgh Terrane, to form the West Australia Craton(WAC) through two collisional orogenic events, the 2.15–2.45 Ma Ophthalmian and 2.05–1950 Ma Glenburgh Orogenies(Johnson et al., 2.13; Fig. 1). Compared to other Proterozoic orogenic belts in Australia, the Capricorn Orogen preserves ‘complete' opposing continental margin successions, together with intervening arc fragments associated with oceanic closure and foreland basins associated with collisional loading(Cawood et al., 2.09).

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Cationic starch microparticles with integrated antibacterial and hemostatic performance

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Science china Technological sciences 2024年第10期67卷 3235-3246页

作者： SU yang NIU MengXin xu KaiDong xu Chen yang PeiLang HU yang xu Fu-Jian Key Lab of Biomedical Materials of Natural Macromolecules (Beijing university of Chemical Technology Ministry of Education)Beijing Laboratory of Biomedical MaterialCollege of Materials Science and EngineeringBeijing University of Chemical Technology department of Burn Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine

It is urgently demanded to develop biomaterials with balanced hemostatic/antibacterial ability and facile preparation methods. In this work, cationic starch microparticles(MSQP), prepared by the facile grafting of microporous starch particles(MS) with tunable quaternized polyethyleneimine, were readily constructed as promising hemostatic materials for integrated antibacterial and hemostatic performance. The cationic grafts not only endowed MSQP with good antibacterial ability, but also benefited from biocompatible MS to achieve favorable biocompatibility. Moreover, in vitro results confirmed the superior hemostatic property of MSQP2.with the medium content of cationic grafts) among three MSQP and pristine MS. After investigating the bloodmaterial interactions of MSQP/MS, the procoagulant mechanism of MSQP2.was revealed that the optimal amount of cationic grafts achieves highly balanced plasma-protein adhesion, platelet adhesion and blood coagulation system. In vivo artery-injury model further demonstrated the superior hemostatic performance of MSQP2.for potential severe hemorrhage. This work sheds light on the design of cationic polymer-based biomaterials for balanced antibacterial and hemostatic functions.

关键词： hemostasis antibacterial cationic polymer microparticles

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New Insight into the Flexoelectricity in the View of Mechanics of Materials:Prismatic Beams Subjected to Bending

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Acta Mechanica Solida Sinica 2024年第4期37卷 555-569页

作者： xu yang Lingling Chen Shengyou yang department of Engineering Mechanics School of Civil EngineeringShandong UniversityJinan250061China

Flexoelectricity is a fascinating electromechanical phenomenon that occurs in non-homogeneously deformed dielectric *** piezoelectricity,the flexoelectric effect is highly dependent on both the material scale and the deformation *** several theoretical models have been proposed to explain the mechanism of flexoelectricity,these models can be rather complicated for those who are interested in studying the *** paper aims to simplify the understanding of flexoelectricity by focusing on the bending behavior of a prismatic dielectric beam from a mechanics of material *** avoid using complicated mathematical formulations based on continuum mechanics,including advanced tensor algebra and calculus of *** formulation clearly explains how inhomogeneous deformations and material size affect the electromechanical coupling,changing the effective bending stiffness,deflection,and rotation angles of a bending *** hope this paper can help undergraduate students and researchers,who are unfamiliar with the electromechanical coupling in flexoelectricity,to develop an understanding of this phenomenon and encourage further research in this area.

关键词： bending formulation dielectric

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Preparation of MWNTs/Al_2._3 composites and their mechanical and electrical properties

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Science china(Technological sciences) 2005年第6期48卷 622-631页

作者： FAN Jinpeng1,2. ZHAO Daqing1,2. xu Zening1,2.& WU Minsheng1,2.1. {2. of Mechanical Engineering, tsinghua university, Beijing 100084, china 2. Key Laboratory for Advanced Manufacturing by Materials Processing Technology, tsinghua university, Beijing 100084, china 1. department of Mechanical Engineering Tsinghua University 100084 Beijing China 2. Key Laboratory for Advanced Manufacturing by Materials Processing Technology Tsinghua University 100084 Beijing China

The mechanical and electrical properties of MWNTs/Al2.3 composite prepared fabricated by hot pressing are investigated. The relation between properties and microstructure of composites is also discussed. With 4wt% MWNTs as reinforcement, the fracture toughness of composite obtained reaches 5.55 MPa·m1/2. which is 80% higher than that of pure Al2.3 obtained in the same conditions. The main toughening mechanism is CNTs’ pinning alumina grain boundaries, and the pullout of CNTs takes effect also. Through adding 2.t% MWNTs and altering the mix method, the fracture toughness of the composite obtained is 3.97 MPa·m1/2. Furthermore, the electrical resistivity is as low as 8.4×10?3 ?·m, decreasing by 14 orders of magnitude compared with pure alumina ceramics. The function of CNTs in composite is related to the distribution state of CNTs in composite, and the distribution state of CNTs in matrix is dependent on preparation procedures.

关键词： MWNTs, alumina, composite, fracture toughness, electrical properties.

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Skeletal interoception in osteoarthritis

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Bone Research 2024年第2期12卷 241-254页

作者： Dinglong yang Jiawen xu Ke xu Peng xu department of Joint Surgery Honghui HospitalXi’an Jiaotong UniversityXi’an 710054China department of Orthopedic Surgery and Orthopedic Research Institute West China HospitalSichuan UniversityChengdu 610041China

The interoception maintains proper physiological conditions and metabolic homeostasis by releasing regulatory signals after perceving changes in the internal state of the *** its various forms,skeletal interoception specifically regulates the metabolic homeostasis of ***(OA)is a complex joint disorder involving cartilage,subchondral bone,and *** subchondral bone undergoes continuous remodeling to adapt to dynamic joint *** findings highlight that skeletal interoception mediated by aberrant mechanical loads contributes to pathological remodeling of the subchondral bone,resulting in subchondral bone sclerosis in *** skeletal interoception is also a potential mechanism for chronic synovial inflammation in *** this review,we offer a general overview of interoception,specifically skeletal interoception,subchondral bone microenviroment and the aberrant subchondral *** also discuss the role of skeletal interoception in abnormal subchondral bone remodeling and synovial inflammation in OA,as well as the potential prospects and challenges in exploring novel OA therapies that target skeletal interoception.

关键词： homeostasis inflammation releasing

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Development of a Three-Dimensional Multiscale Octree SBFEM for Viscoelastic Problems of Heterogeneous Materials

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Computer Modeling in Engineering & sciences 2024年第8期140卷 1831-1861页

作者： xu xu Xiaoteng Wang Haitian {2. Zhenjun {2. Yiqian He State Key Laboratory of Structural Analysis Optimization and CAE Software for Industrial EquipmentDepartment of Engineering MechanicsDalian University of TechnologyDalian116024China Hubei Key Laboratory of Geotechnical and Structural Safety School of Civil EngineeringWuhan UniversityWuhan430072China Mechanik–Materialtheorie Ruhr-Universität BochumBochum44801Germany

The multiscale method provides an effective approach for the numerical analysis of heterogeneous viscoelastic materials by reducing the degree of freedoms(DOFs).A basic framework of the Multiscale Scaled Boundary Finite Element Method(MsSBFEM)was presented in our previous works,but those works only addressed two-dimensional *** order to solve more realistic problems,a three-dimensional MsSBFEM is further developed in this *** the proposed method,the octree SBFEM is used to deal with the three-dimensional calculation for numerical base functions to bridge small and large scales,the three-dimensional image-based analysis can be conveniently conducted in small-scale and coarse nodes can be flexibly adjusted to improve the computational ***,the Temporally Piecewise Adaptive Algorithm(TPAA)is used to maintain the computational accuracy of multiscale analysis by adaptive calculation in time *** results of numerical examples show that the proposed method can significantly reduce the DOFs for three-dimensional viscoelastic analysis with good *** instance,the DOFs can be reduced by 902. times compared with Direct Numerical Simulation(DNS)with an average error of 1.87%in the third example,and it is very effective in dealing with three-dimensional complex microstructures directly based on images without any geometric modelling process.

关键词： Three-dimensionalmultiscale viscoelastic analysis numerical base functions octree SBFEM image-based analysis temporally piecewise adaptive algorithm

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Pole assignment in descriptor periodic systems

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Science china Mathematics 2005年第10期48卷 1309-1332页

作者： FAN Hung-Yuan~1 LIN Wen-Wei~1 & xu Shufang~2.1. {2. of Mathematics,Tsing Hua university,Hsinchu 30043,china 2. LMAM,School of mathematical sciences,Peking university,Beijing 100871,china 1. department of Mathematics Tsing Hua University 30043 Hsinchu China 2. LMAM School of Mathematical Sciences Peking University 100871 Beijing China

In this paper a pole assignment problem is considered for the descriptor linear discrete-time periodic systems, which is using the periodic proportional-derivative feedback to modify a given system such that the closed loop system has a specified selfconjugate set of eigenvalues. It is shown that the complete reachability of an open loop periodic system is equivalent to the possibility of assigning an arbitrary set of the eigenvalues to the system by choosing the suitable periodic proportional-derivative feedback.A computational approach is also proposed to solve the problem, which uses the reliable numerical techniques based on the orthogonal transformations. Numerical examples are presented to illustrate the effectiveness of the proposed approach.

关键词： descriptor linear periodic system, pole assignment, proportional and derivative feedback, numerical method, periodic Schur decomposition.

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ARPES investigation of the electronic structure and its evolution in magnetic topological insulator MnBi2.2.Te4+3n family

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National Science Review 2024年第2期11卷 81-93页

作者： Runzhe xu Lixuan xu Zhongkai Liu Lexian yang Yulin Chen State Key Laboratory of Low Dimensional Quantum Physics Department of PhysicsTsinghua University School of Physical Science and Technology Shanghai Tech University and CAS-Shanghai Science Research Center Shanghai Tech Laboratory for Topological Physics Frontier Science Center for Quantum Information Collaborative Innovation Center of Quantum Matter department of Physics Clarendon LaboratoryUniversity of Oxford

In the past 5 years,there has been significant research interest in the intrinsic magnetic topological insulator family compounds MnBi2.2.Te4+3n（where n=0,1,2.）.In particular,exfoliated thin films of MnBi2.e4have led to numerous experimental breakthroughs,such as the quantum anomalous Hall effect,axion insulator phase and high-Chern number quantum Hall effect without Landau ***,despite extensive efforts,the energy gap of the topological surface states due to exchange magnetic coupling,which is a key feature of the characteristic band structure of the system,remains experimentally *** electronic structure measured by using angle-resolved photoemission （ARPES） shows significant deviation from ab initio prediction and scanning tunneling spectroscopy measurements,making it challenging to understand the transport results based on the electronic *** paper reviews the measurements of the band structure of MnBi2.2.Te4+3nmagnetic topological insulators using ARPES,focusing on the evolution of their electronic structures with temperature,surface and bulk doping and film *** aim of the review is to construct a unified picture of the electronic structure of MnBi2.2.Te4+3ncompounds and explore possible control of their topological properties.

关键词： magnetic topological insulator MnBi2.e4 electronic structure angle-resolved photoemission spectroscopy

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Analysis of Fatty Acid in Biological Samples Using Liquid Chromatography–Quadrupole-Orbitrap Mass Spectrometry Under Parallel Reaction Monitoring Mode

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Journal of Analysis and Testing 2024年第2期8卷 210-217页

作者： Jingxuan yang Wenjun Guo Xiaohang xu Liang Zhao Yajuan xu yang Wang School of Pharmaceutical sciences Changchun University of Chinese MedicineChangchun130117China Key Laboratory of Medicinal Materials Jilin Academy of Chinese Medicine SciencesChangchun130021China Jilin Ginseng Academy Changchun University of Chinese MedicineChangchun130117China

Fatty acids(FAs)are an important class of functional small molecules and participate in a variety of life biological *** experiment proposed a liquid chromatography–quadrupole-Qrbitrap mass spectrometry(LC–Q-Orbitrap MS)method to perform FA profiling under parallel reaction monitoring(PRM)acquisition *** FA was derivatized by 2.dimethylaminoethylamine(DMED)to increase the ionization e fficiency and provide the characterized fragment *** mass spectra obtained from full scan,multiple ion monitoring(MIM),and PRM were *** results showed that the protonated ion of FA+DMED–H2. was detected and the neutral loss of 45.06 Da was observed in the tandem mass *** PRM method provided the highest selectivity and sensitivity for FA detection with the help of accurate mass weight and specific neutral loss-based *** method validation was performed using the FA standards and pooled quality control serum sample,which showed that the established method had good repeatability,stability,and ***,the developed method was successfully applied to analyze the rat serum and brain tissue samples for the drug e ffi-cacy evaluation of gross saponin of Tribulus terrestris ***(GSTTF)against middle cerebral artery occlusion(MCAO)-induced ischemic *** method has extensive practicability and great potential in the detection of FA,especially for the analysis of samples with complex matrices.

关键词： Fatty acid Derivatization LC-Q-Orbitrap MS Parallel reaction monitoring Biological sample

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