Fine slag(FS)is an unavoidable by-product of coal gasification.FS,which is a simple heap of solid waste left in the open air,easily causes environmental pollution and has a low resource utilization rate,thereby restri...Fine slag(FS)is an unavoidable by-product of coal gasification.FS,which is a simple heap of solid waste left in the open air,easily causes environmental pollution and has a low resource utilization rate,thereby restricting the development of energy-saving coal gasification technologies.The multiscale analysis of FS performed in this study indicates typical grain size distribution,composition,crystalline structure,and chemical bonding characteristics.The FS primarily contained inorganic and carbon components(dry bases)and exhibited a"three-peak distribution"of the grain size and regular spheroidal as well as irregular shapes.The irregular particles were mainly adsorbed onto the structure and had a dense distribution and multiple pores and folds.The carbon constituents were primarily amorphous in structure,with a certain degree of order and active sites.C 1s XPS spectrum indicated the presence of C–C and C–H bonds and numerous aromatic structures.The inorganic components,constituting 90%of the total sample,were primarily silicon,aluminum,iron,and calcium.The inorganic components contained Si–O-Si,Si–O–Al,Si–O,SO_(4)^(2−),and Fe–O bonds.Fe 2p XPS spectrum could be deconvoluted into Fe 2p_(1/2) and Fe 2p_(3/2) peaks and satellite peaks,while Fe existed mainly in the form of Fe(III).The findings of this study will be beneficial in resource utilization and formation mechanism of fine slag in future.展开更多
Assimilating satellite radiances into Numerical Weather Prediction(NWP) models has become an important approach to increase the accuracy of numerical weather forecasting. In this study, the assimilation technique sche...Assimilating satellite radiances into Numerical Weather Prediction(NWP) models has become an important approach to increase the accuracy of numerical weather forecasting. In this study, the assimilation technique scheme was employed in NOAA's STMAS(Space-Time Multiscale Analysis System) to assimilate AMSU-A radiances data.Channel selection sensitivity experiments were conducted on assimilated satellite data in the first place. Then, real case analysis of AMSU-A data assimilation was performed. The analysis results showed that, following assimilating of AMSU-A channels 5-11 in STMAS, the objective function quickly converged, and the channel vertical response was consistent with the AMSU-A weighting function distribution, which suggests that the channels can be used in the assimilation of satellite data in STMAS. With the case of the Typhoon Morakot in Taiwan Island in August 2009 as an example, experiments on assimilated and unassimilated AMSU-A radiances data were designed to analyze the impact of the assimilation of satellite data on STMAS. The results demonstrated that assimilation of AMSU-A data provided more accurate prediction of the precipitation region and intensity, and especially, it improved the 0-6h precipitation forecast significantly.展开更多
Palmatine is a valuable ingredient in Chinese medicine that is produced by Phellodendron amurense Rupr. The contents of palmatine content in root bark, trunk bark, perennial branch bark, annual branches, and leaves of...Palmatine is a valuable ingredient in Chinese medicine that is produced by Phellodendron amurense Rupr. The contents of palmatine content in root bark, trunk bark, perennial branch bark, annual branches, and leaves of the trees with different ages and geographies in Northeast China were measured by high-performance liquid chromatography. The contents of palmatine in the barks of root, trunk, and perennial branch were significantly higher than those in annual branches and leaves. The contents of palmatine in trunk bark and root bark from Lesser Khingan Mountains increased with age, which is significantly opposite to other three vegetation types. The contents of palmatine in perennial branch bark, annual bark and leaves had no significant reg- ularity. Moreover, the contents of palmatine in samples of root bark, trunk bark, perennial branch bark and annual bark varied significantly with latitude. The nature populations of P. amurense growing at low latitude contained significantly more palmatine than those growing at high latitude. These results provide a scientific basis for the reasonable cultivation and efficient utilization of P. amurense.展开更多
Fretting wear is a phenomenon,in which wear happens between two oscillatory moving contact surfaces in microscale amplitude.In this paper,the effect of debris between pad and specimen is analyzed by using a semi-concu...Fretting wear is a phenomenon,in which wear happens between two oscillatory moving contact surfaces in microscale amplitude.In this paper,the effect of debris between pad and specimen is analyzed by using a semi-concurrent multiscale method.Firstly,the macroscale fretting wear model is performed.Secondly,the part with the wear profile is imported from the macroscale model to a microscale model after running in stage.Thirdly,an effective pad’s radius is extracted by analyzing the contact pressure in order to take into account the effect of the debris.Finally,the effective radius is up-scaled from the microscale model to the macroscale model,which is used after running in stage.In this way,the effect of debris is considered by changing the radius of the pad in the macroscale model.Due to the smaller number of elements in the microscale model compared with the macroscale model containing the debris layer,the semi-concurrent method proposed in this paper is more computationally efficient.Moreover,the results of this semi-concurrent method show a better agreement with experimental data,compared to the results of the model ignoring the effect of debris.展开更多
Cemented carbide tools are widely utilized in titanium alloy machining.However,severe tool wear usually occurs during machining;thus,the wear process has attracted widespread attention.Electromagnetic treatment was ap...Cemented carbide tools are widely utilized in titanium alloy machining.However,severe tool wear usually occurs during machining;thus,the wear process has attracted widespread attention.Electromagnetic treatment was applied in our previous study to significantly improve the tool life of cemented carbide tools in Ti6Al4V machining.To investigate the effect of electromagnetic treatment on wear performance,a multiscale analysis of the wear process of cemented carbide tools in the turning process,including microdefects and wear topography at various scales,was conducted in the present study.The distribution of dislocations in the tool material was measured through electron backscatter diffraction,and the surface topographies in the wear area during the Ti6Al4V cutting process were recorded via white light interferometry.Fractal analysis based on the scaling property of surface roughness was carried out to further quantify the wear performance of the tools.The results revealed that the wear mechanism of the cutting tools was mainly adhesion and diffusion,and the diffusion wear of the electromagnetically treated tools was less than that of the untreated tools.Based on the multiscale analysis of flank wear,the effect of electromagnetic treatment on the enhancement of the wear resistance of cemented carbide cutting tools was demonstrated.The multiscale analysis of the wear performance of cutting tools in this study effectively revealed the mechanism by which electromagnetic treatment enhances wear resistance,thus contributing to filling the research gap of traditional studies on tool wear that generally employ single scales.展开更多
This study presents a multiscale method to evaluate the transverse tensile strength and failure mechanism of SiC_(f)/TC17 cruciform specimen machined from a large-size ring.The mechanical properties and failure of the...This study presents a multiscale method to evaluate the transverse tensile strength and failure mechanism of SiC_(f)/TC17 cruciform specimen machined from a large-size ring.The mechanical properties and failure of the specimen were evaluated through a macroscale model under transverse tensile loading at 200°C.A mesoscale model was developed to analyze the transverse tensile behavior and failure of the composite specimen.Interfacial debonding,plastic deformation of matrix and cladding,and damage to the composite core were incorporated into the mesoscopic and macroscopic models.The stress–strain curves and fracture modes obtained from the numerical simulation showed good agreement with the experimental curves,acoustic emission test results,and fracture morphology.The simulation results suggested that the damage to the central region interface and the plastic deformation of the matrix initiated first and propagated outwards.Subsequently,the interfacial failure,matrix failure,and formation of macro-crack developed,which led to the crack of the titanium matrix composite core.Finally,cladding was plastically deformed and crack developed,which led to the severe failure of the cruciform specimen.展开更多
Nanosecond single- and multiple-pulse laser damage studies on HfOffSiO2 high-reflection （HR） coatings are performed at 532 nm. For single-pulse irradiation, the damage is attributed to the defects and the electric i...Nanosecond single- and multiple-pulse laser damage studies on HfOffSiO2 high-reflection （HR） coatings are performed at 532 nm. For single-pulse irradiation, the damage is attributed to the defects and the electric intensity distribution in the multilayer thin films. When the defect density in the irradiated area is high, delami- nation is observed. Other than the 1064 nm laser damage, the plasma scalding of the 532 nm laser damage is not pits-centered for normal incidence, and the size of the plasma scalding has no relation to the defect density and position, but increases with the laser fluence. For multiple-pulse irradiations, some damage sites show deeper precursors than those from the single-shot irradiation due to the accumulation effects. The cumulative laser- induced damages behave as pits without the presence of plasma scalding, which is unaffected by the laser fluence and shot numbers. The damage morphologies and depth information both confirm the fatigue effect of a HfO2/SiO2 HR coating under 532 nm laser irradiation.展开更多
A novel multiscale algorithm based on the higher-order continuum at both micro-and macrostructural level is proposed for the consideration of the quasi-brittle damage response of heterogeneous materials.Herein,the mic...A novel multiscale algorithm based on the higher-order continuum at both micro-and macrostructural level is proposed for the consideration of the quasi-brittle damage response of heterogeneous materials.Herein,the microlevel damage is modelled by the degradation of the homogenized stress and tangent stiffness tensors,which are then upscaled to govern the localization at the macrolevel.The C^1 continuity finite element employing a modified case of Mindlin’s form II strain energy density is derived for the softening analysis.To the authors’knowledge,the finite element discretization based on the strain gradient theory is applied for the modeling of damage evolution at the microstructural level for heterogeneous materials for the first time.The advantage of the novel C1 finite element formulation in comparison with the standard finite element discretization in terms of the regularization efficiency as well as the objectivity has been shown.An isotropic damage law is used for the reduction of the constitutive and nonlocal material behaviour,which is necessary for the physically correct description of the localization formation in quasi-brittle materials.The capabilities of the derived finite element to capture the fully developed localization zones are tested on a random representative volume element(RVE)for several different loading cases.By employing the conventional second-order computational homogenization,the microstructural material constitutive response is averaged over the whole RVE area.In order to model the loss of structural integrity when sharp localization is formed across RVE,the specific conditions which detect a completely formed localization zone are developed.A new failure criterion at the microstructural level has been proposed.The derived finite element formulation,as well as the multiscale damage algorithm,are implemented into the finite element program ABAQUS.The capabilities of the presented multiscale scheme to capture the effects of the deformation localization are demonstrated by few benchmark numerical examples.展开更多
This paper is devoted to the microstructure geometric modeling and mechanical properties computation of cancellous bone.The microstructure of the cancellous bone determines its mechanical properties and a precise geom...This paper is devoted to the microstructure geometric modeling and mechanical properties computation of cancellous bone.The microstructure of the cancellous bone determines its mechanical properties and a precise geometric modeling of this structure is important to predict the material properties.Based on the microscopic observation,a new microstructural unit cell model is established by introducing the Schwarz surface in this paper.And this model is very close to the real microstructure and satisfies the main biological characteristics of cancellous bone.By using the unit cell model,the multiscale analysis method is newly applied to predict the mechanical properties of cancellous bone.The effective stiffness parameters are calculated by the up-scaling multi-scale analysis.And the distribution of microscopic stress in cancellous bone is determined through the down-scaling procedure.In addition,the effect of porosity on the stiffness parameters is also investigated.The predictive mechanical properties are in good agreement with the available experimental results,which verifies the applicability of the proposed unit cell model and the validness of the multiscale analysis method to predict the mechanical properties of cancellous bone.展开更多
A multiscale analysis method is presented in which detailed information on the microscopic level is incorporated into macroscopic models capable of simulating damage evolution and ultimate failure.The composite consid...A multiscale analysis method is presented in which detailed information on the microscopic level is incorporated into macroscopic models capable of simulating damage evolution and ultimate failure.The composite considered is reinforced by randomly-dispersed particles,which reflects the statistical characteristics of real materials,such as cement-based materials.Specifically,a three-dimensional material body is decomposed into many unit cells.Each unit cell is reinforced by a cylindrical particle,the orientation of which is characterized by three Euler angles generated by the random number generator.Based on a detailed finite element analysis,the material properties of the representative volume element are obtained.As verification,the properties of the cylindrical particles are set equal to those of the matrix and the computed‘composite’properties reduce exactly to those of the‘isotropic’material,as expected.Through coordinate transformation,the effective material properties of each unit cell are calculated.The assembly of stiffness matrices of all unit cells leads to the stiffness matrix of the whole specimen.Under the simple tension loading condition,the initial damaged unit cell can be identified according to the vonMises yield criterion.The stiffness of the damaged unit cell will then be reduced to zero and it will cause stress redistribution and trigger further damage.It was found that the reinforcement is effective to mitigate and arrest the damage propagation,and therefore prolongs the material’s lifetime.These results suggest that the hierarchical coupling approaches used here may be useful for material design and failure protection in composites.展开更多
This paper reports a multiscale analysis method to predict the thermomechanical coupling performance of composite structures with quasi-periodic properties.In these material structures,the configurations are periodic,...This paper reports a multiscale analysis method to predict the thermomechanical coupling performance of composite structures with quasi-periodic properties.In these material structures,the configurations are periodic,and the material coefficients are quasi-periodic,i.e.,they depend not only on the microscale information but also on the macro location.Also,a mutual interaction between displacement and temperature fields is considered in the problem,which is our particular interest in this study.The multiscale asymptotic expansions of the temperature and displacement fields are constructed and associated error estimation in nearly pointwise sense is presented.Then,a finite element-difference algorithm based on the multiscale analysis method is brought forward in detail.Finally,some numerical examples are given.And the numerical results show that the multiscale method presented in this paper is effective and reliable to study the nonlinear thermo-mechanical coupling problem of composite structures with quasiperiodic properties.展开更多
The transport of fluid, nutrients, and signaling molecules in the bone lacunar-canalicular system （LCS） is critical for osteocyte survival and function. We have applied the fluorescence recovery after photobleaching...The transport of fluid, nutrients, and signaling molecules in the bone lacunar-canalicular system （LCS） is critical for osteocyte survival and function. We have applied the fluorescence recovery after photobleaching （FRAP） approach to quantify load-induced fluid and solute transport in the LCS in situ, but the measurements were limited to cortical regions 30-50 μm underneath the periosteum due to the constrains of laser penetration. With this work, we aimed to expand our understanding of load-induced fluid and solute transport in both trabecular and cortical bone using a multiscaled image-based finite element analysis （FEA） approach. An intact murine tibia was first re-constructed from microCT images into a three-dimensional （3D） linear elastic FEA model, and the matrix deformations at various locations were calculated under axial loading. A segment of the above 3D model was then imported to the biphasic poroelasticity analysis platform （FEBio） to predict load-induced fluid pressure fields, and interstitial solute/fluid flows through LCS in both cortical and trabecular regions. Further, secondary flow effects such as the shear stress and/or drag force acting on osteocytes, the presumed mechano-sensors in bone, were derived using the previously developed ultrastructural model of Brinkman flow in the canaliculi. The material properties assumed in the FEA models were validated against previously obtained strain and FRAP transport data measured on the cortical cortex. Our results demonstrated the feasibility of this computational approach in estimating the fluid flux in the LCS and the cellular stimulation forces （shear and drag forces） for osteocytes in any cortical and trabecular bone locations, allowing further studies of how the activation of osteocytes correlates with in vivo functional bone formation. The study provides a promising platform to reveal potential cellular mechanisms underlying the anabolic power of exercises and physical activities in treating patients with skeletal deficiencies.展开更多
Factorial kriging analysis is applied to the research on the spatial multiscale variability of heavy metals in submarine. It is used to analyze the multiscale spatial structures of seven heavy metals, Ni, Cu, Zn, Pb, ...Factorial kriging analysis is applied to the research on the spatial multiscale variability of heavy metals in submarine. It is used to analyze the multiscale spatial structures of seven heavy metals, Ni, Cu, Zn, Pb, Cr, As and Cd in the surface sediment from the northeastern of Beibu Gulf, identify and separate spatial variations at different scales of heavy metals, and discuss the provenance of heavy metals and the influencing factors. The results show that the existence of three-scale spatial variations those consist of nugget effect, a spherical structure with range of 30 km（short-range scale） and a spherical structure with range of 140 km（long-range scale） in the linear model of coregionalization fitted. The spatial distribution features of seven heavy metals at short-range scale reflect ＂spot-like＂ or ＂stripe-like＂ local-scale spatial variations; the spatial distribution features of the seven heavy metals at long-range scale represent ＂slice-like＂ regional-scale spatial variations. At local scale, Zn, Cr, Ni,Cu, Pb and Cd are derived primarily from parent materials of Hainan Island, Leizhou Peninsula and Guangxi land, whose spatial distribution characteristics are controlled by granularity of sediments, while As is influenced dominantly by human pollution components from Hainan Island and Leizhou Peninsula. At regional scale, Zn,Cr, Ni and Cu originate primarily from parent rock materials of Leizhou Peninsula and Hainan Island, secondly from Guangxi land; As originated primarily from parent rock materials from Hainan Island, secondly from Leizhou Peninsula and Guangxi land. These metals are transported and migrated with sediments dominated by the anticlockwise circulation of Beibu Gulf year-round, deposited in ＂convergence center＂, forming the whole sedimentary pattern in direction of NWW-NNW at regional scale. The difference in distribution type between As and other metals at regional scale is mainly due to their different geochemical behavior.展开更多
A multiscale method for simulating the dynamic response of ceramic matrix composite （CMC） with matrix cracks is developed. At the global level, the finite element method is employed to simulate the dynamic response ...A multiscale method for simulating the dynamic response of ceramic matrix composite （CMC） with matrix cracks is developed. At the global level, the finite element method is employed to simulate the dynamic response of a CMC beam. While at the local level, the multiscale mechanical method is used to estimate the stress/strain response of the material. A distributed computing system is developed to speed up the simulation. The simulation of dynamic response of a Nicalon/CAS-II beam being subjected to harmonic loading is performed as a numerical example. The results show that both the stress/strain responses under tension and compressive loading are nonlinear. These conditions result in a different response compared with that of elastic beam, such as： 1） the displacement response is not symmetric about the axis of time; 2） in the condition of small external load, the response at first order natural frequency is limited within a finite range; 3） decreasing the matrix crack space will increase the displace- ment response of the beam.展开更多
The frequent occurrence of geopolitical crises in the post-financial crisis era is driving the rethinking behind whether the global crude oil market is still a highly connected"great pool".Using the spillove...The frequent occurrence of geopolitical crises in the post-financial crisis era is driving the rethinking behind whether the global crude oil market is still a highly connected"great pool".Using the spillover network model suggested by Baruník and Krehlík(2018),and the daily data of 31 global crude oil markets from 2009 to 2019,this study examines the return and volatility spillover effects and their timevarying behavior in six crude oil market segments at different timescales.The findings indicate that heterogeneity exists in the co-movements between global crude oil markets in the post-financial crisis era.In the medium term,both return and volatility spillover effects are not significant,which makes the diversified portfolio strategy useful.Prices in the Europe and Central Asian regions take the lead in return spillovers.In contrast,Asia-Pacific regional prices contribute the most in terms of volatility spillovers.Long-term volatility spillovers increase sharply when confronted with oil-related events in the postfinancial crisis era.Therefore,policymakers should take effective measures to prevent any large-scale risk transmission in the long run.展开更多
Automotive surface coating manufacturing is one of the most sophisticated and expensive steps in automotive assembly. This step involves generating multiple thin layers of polymeric coatings on the vehicle surface thr...Automotive surface coating manufacturing is one of the most sophisticated and expensive steps in automotive assembly. This step involves generating multiple thin layers of polymeric coatings on the vehicle surface through paint spray and curing in a multistage, dynamically changing environment. Traditionally, the quality control is solely post-process inspection based, and process operational adjustment is only experience based, thus the manufacturing may not be （highly） sustainable. In this article, a multiscale system modeling and analysis methodology is introduced for achieving a sustainable application of polymeric materials through paint spray and film curing in automotive surface coating manufacturing. By this methodology, the correlations among paint material, application processes and coating performance can be identified. The model-based analysis allows a comprehensive and deep study of the dynamic behaviors of the material, process, and product in a wide spectrum of length and time. Case studies illustrate the efficacy of the methodology for sustainable manufacturing.展开更多
By combining multiscale stationary wavelet analysis with fuzzy c-means, a robust edge detection algorithm is presented. Based on the translation invafiance built in multiscale stationary wavelet transform, components ...By combining multiscale stationary wavelet analysis with fuzzy c-means, a robust edge detection algorithm is presented. Based on the translation invafiance built in multiscale stationary wavelet transform, components in different transformed sub-images corresponding to a pixel are employed to form a feature vector of the pixel. All the feature vectors are classified with unsupervised fuzzy c-means to segment the image, and then the edge pixels are checked out by the Canny detector. A series of images contaminated with different intensive Gaussian noises are used to test the novel algorithm. Experiments show that fairly precise edges can be checked out robustly from those images with fairly intensive noise by the proposed algorithm.展开更多
A novel wavelet-based algorithm for image enhancement is proposed in the paper. On the basis of multiscale analysis, the proposed algorithm solves efficiently the problem of noise over-enhancement, which commonly occu...A novel wavelet-based algorithm for image enhancement is proposed in the paper. On the basis of multiscale analysis, the proposed algorithm solves efficiently the problem of noise over-enhancement, which commonly occurs in the traditional methods for contrast enhancement. The decomposed coefficients at same scales are processed by a nonlinear method, and the coefficients at different scales are enhanced in different degree. During the procedure, the method takes full advantage of the properties of Human visual system so as to achieve better performance. The simulations demonstrate that these characters of the proposed approach enable it to fully enhance the content in images, to efficiently alleviate the enhancement of noise and to achieve much better enhancement effect than the traditional approaches. Key words wavelet transform - image contrast enhancement - multiscale analysis CLC number TP 391 Foundation item: Supported by the National Natural Science Foundation of China (69931010)Biography: Wu Ying-qian (1974-), male, Ph. D, research direction: image processing, image compression and wavelet.展开更多
An algorithm which allows the generation of representative volume elements(RVEs) for complex woven and warp-interlaced fiber-reinforced composite topologies while avoiding unphysical tow intersections is presented. Th...An algorithm which allows the generation of representative volume elements(RVEs) for complex woven and warp-interlaced fiber-reinforced composite topologies while avoiding unphysical tow intersections is presented. This is achieved by extending an existing RVE generation strategy in two significant ways:(1) the local cross section shape of the tow is adjusted depending on the local tow curvature in a way that preserves the cross sectional area of the tow, and(2) the elementary crimp interval is separated into a planar and a transition region. The modifications facilitate the generation of a wide range of elaborate textile topologies without tow intersections, which are present without the proposed modifications unless complex tow to tow contact models are introduced. The mechanical properties of plain weaves were predicted based on the topology generated with the proposed algorithm as well as based on RVEs which were constructed based on actual micrographs, i.e. a "digital twin" of the actual microstructure. A comparison of the predicted mechanical properties based on finite element and Multiscale Generalized Method of Cells techniques shows close agreement. However, some differences exist with respect to experimentally determined material parameters due to the finite dimensions of the specimens. Lastly,mechanical properties of multilayered weaves are predicted with the finite element method. The considered material systems are carbon fiber in epoxy matrix as well as C/C-SiC. However, the procedure is applicable to a wide range of material systems.展开更多
基金Scientific Research Foundation for the Introduction of Talent in Anhui University of Science and Technology(2023yjrc90)Graduate Research Project of Higher Education in Anhui Province(YJS20210377)+2 种基金Postgraduate Innovation Fund of Anhui University of Science and Technology(2021CX1002)University Synergy Innovation Program of Anhui Province(GXXT-2020-006)National Science Fund for Young Scientists(52200139).
文摘Fine slag(FS)is an unavoidable by-product of coal gasification.FS,which is a simple heap of solid waste left in the open air,easily causes environmental pollution and has a low resource utilization rate,thereby restricting the development of energy-saving coal gasification technologies.The multiscale analysis of FS performed in this study indicates typical grain size distribution,composition,crystalline structure,and chemical bonding characteristics.The FS primarily contained inorganic and carbon components(dry bases)and exhibited a"three-peak distribution"of the grain size and regular spheroidal as well as irregular shapes.The irregular particles were mainly adsorbed onto the structure and had a dense distribution and multiple pores and folds.The carbon constituents were primarily amorphous in structure,with a certain degree of order and active sites.C 1s XPS spectrum indicated the presence of C–C and C–H bonds and numerous aromatic structures.The inorganic components,constituting 90%of the total sample,were primarily silicon,aluminum,iron,and calcium.The inorganic components contained Si–O-Si,Si–O–Al,Si–O,SO_(4)^(2−),and Fe–O bonds.Fe 2p XPS spectrum could be deconvoluted into Fe 2p_(1/2) and Fe 2p_(3/2) peaks and satellite peaks,while Fe existed mainly in the form of Fe(III).The findings of this study will be beneficial in resource utilization and formation mechanism of fine slag in future.
基金National Natural Science Foundation of China(41375027,41130960,41275114,41275039)Public Benefit Research Foundation of China Meteorological Administration(GYHY201406001,GYHY201106044)+1 种基金"863"Program(2012AA120903)National Key Research and Development Program of China(2016YFB0502501)
文摘Assimilating satellite radiances into Numerical Weather Prediction(NWP) models has become an important approach to increase the accuracy of numerical weather forecasting. In this study, the assimilation technique scheme was employed in NOAA's STMAS(Space-Time Multiscale Analysis System) to assimilate AMSU-A radiances data.Channel selection sensitivity experiments were conducted on assimilated satellite data in the first place. Then, real case analysis of AMSU-A data assimilation was performed. The analysis results showed that, following assimilating of AMSU-A channels 5-11 in STMAS, the objective function quickly converged, and the channel vertical response was consistent with the AMSU-A weighting function distribution, which suggests that the channels can be used in the assimilation of satellite data in STMAS. With the case of the Typhoon Morakot in Taiwan Island in August 2009 as an example, experiments on assimilated and unassimilated AMSU-A radiances data were designed to analyze the impact of the assimilation of satellite data on STMAS. The results demonstrated that assimilation of AMSU-A data provided more accurate prediction of the precipitation region and intensity, and especially, it improved the 0-6h precipitation forecast significantly.
基金supported by Special Fund for ForestryScientific Research in the Public Interest(Grant No.201104066)
文摘Palmatine is a valuable ingredient in Chinese medicine that is produced by Phellodendron amurense Rupr. The contents of palmatine content in root bark, trunk bark, perennial branch bark, annual branches, and leaves of the trees with different ages and geographies in Northeast China were measured by high-performance liquid chromatography. The contents of palmatine in the barks of root, trunk, and perennial branch were significantly higher than those in annual branches and leaves. The contents of palmatine in trunk bark and root bark from Lesser Khingan Mountains increased with age, which is significantly opposite to other three vegetation types. The contents of palmatine in perennial branch bark, annual bark and leaves had no significant reg- ularity. Moreover, the contents of palmatine in samples of root bark, trunk bark, perennial branch bark and annual bark varied significantly with latitude. The nature populations of P. amurense growing at low latitude contained significantly more palmatine than those growing at high latitude. These results provide a scientific basis for the reasonable cultivation and efficient utilization of P. amurense.
文摘Fretting wear is a phenomenon,in which wear happens between two oscillatory moving contact surfaces in microscale amplitude.In this paper,the effect of debris between pad and specimen is analyzed by using a semi-concurrent multiscale method.Firstly,the macroscale fretting wear model is performed.Secondly,the part with the wear profile is imported from the macroscale model to a microscale model after running in stage.Thirdly,an effective pad’s radius is extracted by analyzing the contact pressure in order to take into account the effect of the debris.Finally,the effective radius is up-scaled from the microscale model to the macroscale model,which is used after running in stage.In this way,the effect of debris is considered by changing the radius of the pad in the macroscale model.Due to the smaller number of elements in the microscale model compared with the macroscale model containing the debris layer,the semi-concurrent method proposed in this paper is more computationally efficient.Moreover,the results of this semi-concurrent method show a better agreement with experimental data,compared to the results of the model ignoring the effect of debris.
基金supported by the National Natural Science Foundation of China(No.52275441)the Shenzhen Science and Technology Program(No.KJZD20230923114606013).
文摘Cemented carbide tools are widely utilized in titanium alloy machining.However,severe tool wear usually occurs during machining;thus,the wear process has attracted widespread attention.Electromagnetic treatment was applied in our previous study to significantly improve the tool life of cemented carbide tools in Ti6Al4V machining.To investigate the effect of electromagnetic treatment on wear performance,a multiscale analysis of the wear process of cemented carbide tools in the turning process,including microdefects and wear topography at various scales,was conducted in the present study.The distribution of dislocations in the tool material was measured through electron backscatter diffraction,and the surface topographies in the wear area during the Ti6Al4V cutting process were recorded via white light interferometry.Fractal analysis based on the scaling property of surface roughness was carried out to further quantify the wear performance of the tools.The results revealed that the wear mechanism of the cutting tools was mainly adhesion and diffusion,and the diffusion wear of the electromagnetically treated tools was less than that of the untreated tools.Based on the multiscale analysis of flank wear,the effect of electromagnetic treatment on the enhancement of the wear resistance of cemented carbide cutting tools was demonstrated.The multiscale analysis of the wear performance of cutting tools in this study effectively revealed the mechanism by which electromagnetic treatment enhances wear resistance,thus contributing to filling the research gap of traditional studies on tool wear that generally employ single scales.
基金This work was supported by the National Science and Technology Major Project(HT-J2019-VI-0007-0121)the CAS Project for Young Scientists in Basic Research(YSBR-025)the National Natural Science Foundation of China(No.52101164).
文摘This study presents a multiscale method to evaluate the transverse tensile strength and failure mechanism of SiC_(f)/TC17 cruciform specimen machined from a large-size ring.The mechanical properties and failure of the specimen were evaluated through a macroscale model under transverse tensile loading at 200°C.A mesoscale model was developed to analyze the transverse tensile behavior and failure of the composite specimen.Interfacial debonding,plastic deformation of matrix and cladding,and damage to the composite core were incorporated into the mesoscopic and macroscopic models.The stress–strain curves and fracture modes obtained from the numerical simulation showed good agreement with the experimental curves,acoustic emission test results,and fracture morphology.The simulation results suggested that the damage to the central region interface and the plastic deformation of the matrix initiated first and propagated outwards.Subsequently,the interfacial failure,matrix failure,and formation of macro-crack developed,which led to the crack of the titanium matrix composite core.Finally,cladding was plastically deformed and crack developed,which led to the severe failure of the cruciform specimen.
基金supported by the National Natural Science Foundation of China under Grant Nos.11104293and 61308021
文摘Nanosecond single- and multiple-pulse laser damage studies on HfOffSiO2 high-reflection （HR） coatings are performed at 532 nm. For single-pulse irradiation, the damage is attributed to the defects and the electric intensity distribution in the multilayer thin films. When the defect density in the irradiated area is high, delami- nation is observed. Other than the 1064 nm laser damage, the plasma scalding of the 532 nm laser damage is not pits-centered for normal incidence, and the size of the plasma scalding has no relation to the defect density and position, but increases with the laser fluence. For multiple-pulse irradiations, some damage sites show deeper precursors than those from the single-shot irradiation due to the accumulation effects. The cumulative laser- induced damages behave as pits without the presence of plasma scalding, which is unaffected by the laser fluence and shot numbers. The damage morphologies and depth information both confirm the fatigue effect of a HfO2/SiO2 HR coating under 532 nm laser irradiation.
基金This work has been fully supported by Croatian Science Foundation under the project“Multiscale Numerical Modelling of Material Deformation Responses from Macro-to Nanolevel”(2516).
文摘A novel multiscale algorithm based on the higher-order continuum at both micro-and macrostructural level is proposed for the consideration of the quasi-brittle damage response of heterogeneous materials.Herein,the microlevel damage is modelled by the degradation of the homogenized stress and tangent stiffness tensors,which are then upscaled to govern the localization at the macrolevel.The C^1 continuity finite element employing a modified case of Mindlin’s form II strain energy density is derived for the softening analysis.To the authors’knowledge,the finite element discretization based on the strain gradient theory is applied for the modeling of damage evolution at the microstructural level for heterogeneous materials for the first time.The advantage of the novel C1 finite element formulation in comparison with the standard finite element discretization in terms of the regularization efficiency as well as the objectivity has been shown.An isotropic damage law is used for the reduction of the constitutive and nonlocal material behaviour,which is necessary for the physically correct description of the localization formation in quasi-brittle materials.The capabilities of the derived finite element to capture the fully developed localization zones are tested on a random representative volume element(RVE)for several different loading cases.By employing the conventional second-order computational homogenization,the microstructural material constitutive response is averaged over the whole RVE area.In order to model the loss of structural integrity when sharp localization is formed across RVE,the specific conditions which detect a completely formed localization zone are developed.A new failure criterion at the microstructural level has been proposed.The derived finite element formulation,as well as the multiscale damage algorithm,are implemented into the finite element program ABAQUS.The capabilities of the presented multiscale scheme to capture the effects of the deformation localization are demonstrated by few benchmark numerical examples.
基金This work is supported by the National Natural Science Foundation of China(11471262,11501449)Fundamental Research Funds for the Central Universities(3102017zy043)China Postdoctoral Science Foundation(2018M633569).
文摘This paper is devoted to the microstructure geometric modeling and mechanical properties computation of cancellous bone.The microstructure of the cancellous bone determines its mechanical properties and a precise geometric modeling of this structure is important to predict the material properties.Based on the microscopic observation,a new microstructural unit cell model is established by introducing the Schwarz surface in this paper.And this model is very close to the real microstructure and satisfies the main biological characteristics of cancellous bone.By using the unit cell model,the multiscale analysis method is newly applied to predict the mechanical properties of cancellous bone.The effective stiffness parameters are calculated by the up-scaling multi-scale analysis.And the distribution of microscopic stress in cancellous bone is determined through the down-scaling procedure.In addition,the effect of porosity on the stiffness parameters is also investigated.The predictive mechanical properties are in good agreement with the available experimental results,which verifies the applicability of the proposed unit cell model and the validness of the multiscale analysis method to predict the mechanical properties of cancellous bone.
文摘A multiscale analysis method is presented in which detailed information on the microscopic level is incorporated into macroscopic models capable of simulating damage evolution and ultimate failure.The composite considered is reinforced by randomly-dispersed particles,which reflects the statistical characteristics of real materials,such as cement-based materials.Specifically,a three-dimensional material body is decomposed into many unit cells.Each unit cell is reinforced by a cylindrical particle,the orientation of which is characterized by three Euler angles generated by the random number generator.Based on a detailed finite element analysis,the material properties of the representative volume element are obtained.As verification,the properties of the cylindrical particles are set equal to those of the matrix and the computed‘composite’properties reduce exactly to those of the‘isotropic’material,as expected.Through coordinate transformation,the effective material properties of each unit cell are calculated.The assembly of stiffness matrices of all unit cells leads to the stiffness matrix of the whole specimen.Under the simple tension loading condition,the initial damaged unit cell can be identified according to the vonMises yield criterion.The stiffness of the damaged unit cell will then be reduced to zero and it will cause stress redistribution and trigger further damage.It was found that the reinforcement is effective to mitigate and arrest the damage propagation,and therefore prolongs the material’s lifetime.These results suggest that the hierarchical coupling approaches used here may be useful for material design and failure protection in composites.
基金financially supported by the National Natural Science Foundation of China(11501449)the Fundamental Research Funds for the Central Universities(3102017zy043)+2 种基金the China Postdoctoral Science Foundation(2016T91019)the fund of the State Key Laboratory of Solidification Processing in NWPU(SKLSP201628)the Scientific Research Program Funded by Shaanxi Provincial Education Department(14JK1353).
文摘This paper reports a multiscale analysis method to predict the thermomechanical coupling performance of composite structures with quasi-periodic properties.In these material structures,the configurations are periodic,and the material coefficients are quasi-periodic,i.e.,they depend not only on the microscale information but also on the macro location.Also,a mutual interaction between displacement and temperature fields is considered in the problem,which is our particular interest in this study.The multiscale asymptotic expansions of the temperature and displacement fields are constructed and associated error estimation in nearly pointwise sense is presented.Then,a finite element-difference algorithm based on the multiscale analysis method is brought forward in detail.Finally,some numerical examples are given.And the numerical results show that the multiscale method presented in this paper is effective and reliable to study the nonlinear thermo-mechanical coupling problem of composite structures with quasiperiodic properties.
基金supported by grants from NIH (P30GM103333 and RO1AR054385 to LW)China CSC fellowship (to LF)DOD W81XWH-13-1-0148 (to XLL)
文摘The transport of fluid, nutrients, and signaling molecules in the bone lacunar-canalicular system （LCS） is critical for osteocyte survival and function. We have applied the fluorescence recovery after photobleaching （FRAP） approach to quantify load-induced fluid and solute transport in the LCS in situ, but the measurements were limited to cortical regions 30-50 μm underneath the periosteum due to the constrains of laser penetration. With this work, we aimed to expand our understanding of load-induced fluid and solute transport in both trabecular and cortical bone using a multiscaled image-based finite element analysis （FEA） approach. An intact murine tibia was first re-constructed from microCT images into a three-dimensional （3D） linear elastic FEA model, and the matrix deformations at various locations were calculated under axial loading. A segment of the above 3D model was then imported to the biphasic poroelasticity analysis platform （FEBio） to predict load-induced fluid pressure fields, and interstitial solute/fluid flows through LCS in both cortical and trabecular regions. Further, secondary flow effects such as the shear stress and/or drag force acting on osteocytes, the presumed mechano-sensors in bone, were derived using the previously developed ultrastructural model of Brinkman flow in the canaliculi. The material properties assumed in the FEA models were validated against previously obtained strain and FRAP transport data measured on the cortical cortex. Our results demonstrated the feasibility of this computational approach in estimating the fluid flux in the LCS and the cellular stimulation forces （shear and drag forces） for osteocytes in any cortical and trabecular bone locations, allowing further studies of how the activation of osteocytes correlates with in vivo functional bone formation. The study provides a promising platform to reveal potential cellular mechanisms underlying the anabolic power of exercises and physical activities in treating patients with skeletal deficiencies.
基金The National Natural Science Foundation of China under contract Nos 41176045,41476050,41106047,41476047 and41106045the Scientific Research Fund of the Second Institute of Oceanography,State Oceanic Administration of China under contract No.JG1204+2 种基金the National Special Project for"Global change and air-sea interaction"under contract Nos GASI-04-01-02 and GASI-GEOGE-03Chinese Polar Environment Comprehensive Investigation and Assessment Programmes under contract Nos CHINARE2012-01-02,CHINARE2013-01-02,CHINARE2014-01-02,CHINARE2013-04-01 and CHINARE2014-04-01the Marine Public Welfare Research Project,State Oceanic Administration of China under contract No.201105003
文摘Factorial kriging analysis is applied to the research on the spatial multiscale variability of heavy metals in submarine. It is used to analyze the multiscale spatial structures of seven heavy metals, Ni, Cu, Zn, Pb, Cr, As and Cd in the surface sediment from the northeastern of Beibu Gulf, identify and separate spatial variations at different scales of heavy metals, and discuss the provenance of heavy metals and the influencing factors. The results show that the existence of three-scale spatial variations those consist of nugget effect, a spherical structure with range of 30 km（short-range scale） and a spherical structure with range of 140 km（long-range scale） in the linear model of coregionalization fitted. The spatial distribution features of seven heavy metals at short-range scale reflect ＂spot-like＂ or ＂stripe-like＂ local-scale spatial variations; the spatial distribution features of the seven heavy metals at long-range scale represent ＂slice-like＂ regional-scale spatial variations. At local scale, Zn, Cr, Ni,Cu, Pb and Cd are derived primarily from parent materials of Hainan Island, Leizhou Peninsula and Guangxi land, whose spatial distribution characteristics are controlled by granularity of sediments, while As is influenced dominantly by human pollution components from Hainan Island and Leizhou Peninsula. At regional scale, Zn,Cr, Ni and Cu originate primarily from parent rock materials of Leizhou Peninsula and Hainan Island, secondly from Guangxi land; As originated primarily from parent rock materials from Hainan Island, secondly from Leizhou Peninsula and Guangxi land. These metals are transported and migrated with sediments dominated by the anticlockwise circulation of Beibu Gulf year-round, deposited in ＂convergence center＂, forming the whole sedimentary pattern in direction of NWW-NNW at regional scale. The difference in distribution type between As and other metals at regional scale is mainly due to their different geochemical behavior.
基金Jiangsu Postdoctoral Science Foundation (0902013C)Innovation Foundation for Young Teachers in University of Aeronautics and Astronautics (Y1024-054)
文摘A multiscale method for simulating the dynamic response of ceramic matrix composite （CMC） with matrix cracks is developed. At the global level, the finite element method is employed to simulate the dynamic response of a CMC beam. While at the local level, the multiscale mechanical method is used to estimate the stress/strain response of the material. A distributed computing system is developed to speed up the simulation. The simulation of dynamic response of a Nicalon/CAS-II beam being subjected to harmonic loading is performed as a numerical example. The results show that both the stress/strain responses under tension and compressive loading are nonlinear. These conditions result in a different response compared with that of elastic beam, such as： 1） the displacement response is not symmetric about the axis of time; 2） in the condition of small external load, the response at first order natural frequency is limited within a finite range; 3） decreasing the matrix crack space will increase the displace- ment response of the beam.
基金the financial support from the National Natural Science Foundation of China(No.71922013)。
文摘The frequent occurrence of geopolitical crises in the post-financial crisis era is driving the rethinking behind whether the global crude oil market is still a highly connected"great pool".Using the spillover network model suggested by Baruník and Krehlík(2018),and the daily data of 31 global crude oil markets from 2009 to 2019,this study examines the return and volatility spillover effects and their timevarying behavior in six crude oil market segments at different timescales.The findings indicate that heterogeneity exists in the co-movements between global crude oil markets in the post-financial crisis era.In the medium term,both return and volatility spillover effects are not significant,which makes the diversified portfolio strategy useful.Prices in the Europe and Central Asian regions take the lead in return spillovers.In contrast,Asia-Pacific regional prices contribute the most in terms of volatility spillovers.Long-term volatility spillovers increase sharply when confronted with oil-related events in the postfinancial crisis era.Therefore,policymakers should take effective measures to prevent any large-scale risk transmission in the long run.
基金Supported in part by US NSF (CBET 0647113 and 0730383, CMMI 0700178, and DUE 0736739)the Institute of Manufacturing Research of Wayne State University.
文摘Automotive surface coating manufacturing is one of the most sophisticated and expensive steps in automotive assembly. This step involves generating multiple thin layers of polymeric coatings on the vehicle surface through paint spray and curing in a multistage, dynamically changing environment. Traditionally, the quality control is solely post-process inspection based, and process operational adjustment is only experience based, thus the manufacturing may not be （highly） sustainable. In this article, a multiscale system modeling and analysis methodology is introduced for achieving a sustainable application of polymeric materials through paint spray and film curing in automotive surface coating manufacturing. By this methodology, the correlations among paint material, application processes and coating performance can be identified. The model-based analysis allows a comprehensive and deep study of the dynamic behaviors of the material, process, and product in a wide spectrum of length and time. Case studies illustrate the efficacy of the methodology for sustainable manufacturing.
文摘By combining multiscale stationary wavelet analysis with fuzzy c-means, a robust edge detection algorithm is presented. Based on the translation invafiance built in multiscale stationary wavelet transform, components in different transformed sub-images corresponding to a pixel are employed to form a feature vector of the pixel. All the feature vectors are classified with unsupervised fuzzy c-means to segment the image, and then the edge pixels are checked out by the Canny detector. A series of images contaminated with different intensive Gaussian noises are used to test the novel algorithm. Experiments show that fairly precise edges can be checked out robustly from those images with fairly intensive noise by the proposed algorithm.
文摘A novel wavelet-based algorithm for image enhancement is proposed in the paper. On the basis of multiscale analysis, the proposed algorithm solves efficiently the problem of noise over-enhancement, which commonly occurs in the traditional methods for contrast enhancement. The decomposed coefficients at same scales are processed by a nonlinear method, and the coefficients at different scales are enhanced in different degree. During the procedure, the method takes full advantage of the properties of Human visual system so as to achieve better performance. The simulations demonstrate that these characters of the proposed approach enable it to fully enhance the content in images, to efficiently alleviate the enhancement of noise and to achieve much better enhancement effect than the traditional approaches. Key words wavelet transform - image contrast enhancement - multiscale analysis CLC number TP 391 Foundation item: Supported by the National Natural Science Foundation of China (69931010)Biography: Wu Ying-qian (1974-), male, Ph. D, research direction: image processing, image compression and wavelet.
基金support from the Excellence Initiative of the German federal and state governments (GS018/OPBF051)funding through the von Kármán fellowship GS069+3 种基金the Alexander von Humboldt FoundationFunding by the Ministry of Innovation, Science and Research of the State of North Rhine-Westphalia is acknowledged by J.-W. Simonthe support from the Space Technology Mission Directorate Composite Technology for Exploration Projectthe Aeronautics Research Directorate Transformational Tools and Technologies Project
文摘An algorithm which allows the generation of representative volume elements(RVEs) for complex woven and warp-interlaced fiber-reinforced composite topologies while avoiding unphysical tow intersections is presented. This is achieved by extending an existing RVE generation strategy in two significant ways:(1) the local cross section shape of the tow is adjusted depending on the local tow curvature in a way that preserves the cross sectional area of the tow, and(2) the elementary crimp interval is separated into a planar and a transition region. The modifications facilitate the generation of a wide range of elaborate textile topologies without tow intersections, which are present without the proposed modifications unless complex tow to tow contact models are introduced. The mechanical properties of plain weaves were predicted based on the topology generated with the proposed algorithm as well as based on RVEs which were constructed based on actual micrographs, i.e. a "digital twin" of the actual microstructure. A comparison of the predicted mechanical properties based on finite element and Multiscale Generalized Method of Cells techniques shows close agreement. However, some differences exist with respect to experimentally determined material parameters due to the finite dimensions of the specimens. Lastly,mechanical properties of multilayered weaves are predicted with the finite element method. The considered material systems are carbon fiber in epoxy matrix as well as C/C-SiC. However, the procedure is applicable to a wide range of material systems.
