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 Fini...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 problems.In order to solve more realistic problems,a three-dimensional MsSBFEM is further developed in this article.In 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 accuracy.Besides,the Temporally Piecewise Adaptive Algorithm(TPAA)is used to maintain the computational accuracy of multiscale analysis by adaptive calculation in time domain.The results of numerical examples show that the proposed method can significantly reduce the DOFs for three-dimensional viscoelastic analysis with good accuracy.For instance,the DOFs can be reduced by 9021 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.展开更多
Critical properties of metallic materials,such as the yield stress,corrosion resistance and ductility depend on the microstructure and its grain size and size distribution.Solute atoms that favorably segregate to grai...Critical properties of metallic materials,such as the yield stress,corrosion resistance and ductility depend on the microstructure and its grain size and size distribution.Solute atoms that favorably segregate to grain boundaries produce a pinning atmosphere that exerts a drag pressure on the boundary motion,which strongly affects the grain growth behavior during annealing.In the current work,the characteristics of grain growth in an annealed Mg-1 wt.%Mn-1 wt.%Nd magnesium alloy were investigated by advanced experimental and modeling techniques.Systematic quasi in-situ orientation mappings with a scanning electron microscope were performed to track the evolution of local and global microstructural characteristics as a function of annealing time.Solute segregation at targeted grain boundaries was measured using three-dimensional atom probe tomography.Level-set computer simulations were carried with different setups of driving forces to explore their contribution to the microstructure development with and without solute drag.The results showed that the favorable growth advantage for some grains leading to a transient stage of abnormal grain growth is controlled by several drivers with varying importance at different stages of annealing.For longer annealing times,residual dislocation density gradients between large and smaller grains are no longer important,which leads to microstructure stability due to predominant solute drag.Local fluctuations in residual dislocation energy and solute concentration near grain boundaries cause different boundary segments to migrate at different rates,which affects the average growth rate of large grains and their evolved shape.展开更多
For high-precision pulsar timing analysis and low-frequency gravitational wave detection,it is essential to accurately determine pulsar pulse times of arrival(ToAs)and associated uncertainties.To measure the ToAs and ...For high-precision pulsar timing analysis and low-frequency gravitational wave detection,it is essential to accurately determine pulsar pulse times of arrival(ToAs)and associated uncertainties.To measure the ToAs and their uncertainties,various cross-correlation-based techniques can be employed.We develop methodologies to investigate the impact of the template-matching method,profile shape,signal-to-noise ratio of both template and observation on ToA uncertainties.These methodologies are then applied to data from the International Pulsar Timing Array.We demonstrate that the Fourier domain Markov chain Monte Carlo method is generally superior to other methods,while the Gaussian interpolation shift method outperforms other methods in certain cases,such as profiles with large duty cycles or smooth profiles without sharp features.However,it is important to note that our study focuses solely on ToA uncertainty,and the optimal method for determining both ToA and ToA uncertainty may differ.展开更多
The service performance of the turbine blade root of an aero-engine depends on the microstructures in its superficial layer.This work investigated the surface deformation structures of turbine blade root of single cry...The service performance of the turbine blade root of an aero-engine depends on the microstructures in its superficial layer.This work investigated the surface deformation structures of turbine blade root of single crystal nickel-based superalloy produced under different creep feed grinding conditions.Gradient microstructures in the superficial layer were clarified and composed of a severely deformed layer(DFL)with nano-sized grains(48–67 nm)at the topmost surface,a DFL with submicron-sized grains(66–158 nm)and micron-sized laminated structures at the subsurface,and a dislocation accumulated layer extending to the bulk material.The formation of such gradient microstructures was found to be related to the graded variations in the plastic strain and strain rate induced in the creep feed grinding process,which were as high as 6.67 and 8.17×10^(7)s^(−1),respectively.In the current study,the evolution of surface gradient microstructures was essentially a transition process from a coarse single crystal to nano-sized grains and,simultaneously,from one orientation of a single crystal to random orientations of polycrystals,during which the dislocation slips dominated the creep feed grinding induced microstructure deformation of single crystal nickel-based superalloy.展开更多
Plasticity of cerebellar Purkinje cells(PC)is influenced by progeste rone via the classical progeste rone receptors PR-A and PR-B by stimulating dendritogenesis,spinogenesis,and synaptogenesis in these cells.Dissociat...Plasticity of cerebellar Purkinje cells(PC)is influenced by progeste rone via the classical progeste rone receptors PR-A and PR-B by stimulating dendritogenesis,spinogenesis,and synaptogenesis in these cells.Dissociated PC cultures were used to analyze progeste rone effects at a molecular level on the voltage-gated T-type-Ca^(2+)-channels Ca_(v)3.1,Ca_(v)3.2,and Ca_(v)3.3 as they helped determine neuronal plasticity by regulating Ca^(2+)-influx in neuronal cells.The results showed direct effects of progesterone on the mRNA expression of T-type-Ca^(2+)-channels,as well as on the protein kinases A and C being involved in downstream signaling pathways that play an important role in neuronal plasticity.For the mRNA expression studies of T-type-Ca^(2+)-channels and protein kinases of the signaling cascade,laser microdissection and purified PC cultures of diffe rent maturation stages were used.Immunohistochemical staining was also performed to characte rize the localization of T-type-Ca^(2+)-channels in PC.Expe rimental progesterone treatment was performed on the purified PC culture for 24 and 48 hours.Our results show that progesterone increases the expression of Ca_(v)3.1 and Ca_(v)3.3 and associated protein kinases A and Cin PC at the mRNA level within 48 hours after treatment at latest.These effects extend the current knowledge of the function of progesterone in the central nervous system and provide an explanatory approach for its influence on neuronal plasticity.展开更多
Photocatalytic oxidation of alcohols has received more and more attention in recent years following the numerous studies on the degradation of pollutants, hydrogen evolution, and CO_(2) reduction by photocatalysis. In...Photocatalytic oxidation of alcohols has received more and more attention in recent years following the numerous studies on the degradation of pollutants, hydrogen evolution, and CO_(2) reduction by photocatalysis. Instead of the total oxidation of organics in the degradation process, the photo-oxidation of alcohols aims at the selective conversion of alcohols to produce carbonyl/acid compounds. Promising results have been achieved in designing the catalysts and reaction system, as well as in the mechanistic investigations in the past few years. This review summarizes the state-of-the-art progress in the photo-oxidation of alcohols, including the development of photocatalysts and cocatalysts, reaction conditions including the solvent and the atmosphere, and the exploration of mechanisms with scavengers experiment, electron paramagnetic resonance (EPR) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The challenges and outlook for the further research in this field are also discussed.展开更多
For deep rock mechanics and subsurface engineering,accurately characterizing and evaluating rock heterogeneity as well as analyzing the correlation between the heterogeneity and physical and mechanical properties of r...For deep rock mechanics and subsurface engineering,accurately characterizing and evaluating rock heterogeneity as well as analyzing the correlation between the heterogeneity and physical and mechanical properties of rocks are critical.This study investigated the characteristics of acoustic emission signals produced in the process of strong and weak phase damage to rocks.The failure mechanisms of the strong and weak phases were analyzed by performing Brazilian splitting tests on different metagabbros and granites.The strong-weak phase ratio of the rocks and the uniformity of their spatial distribution were characterized.Test results show that as the feldspar develops,the strong-phase ratio of the metagabbro increases.However,the spatial distribution of feldspar minerals in the metagabbro becomes less uniform.The mineral spatial distribution uniformity in the altered granite is good;however,its strong-phase ratio is low.Furthermore,the strong-phase ratio of the typical granite is high;however,its mineral spatial distribution uniformity is poor.Moreover,uniaxial and triaxial test results show that the peak strength and elastic modulus of the rocks are related to the strong-weak phase ratio and mineral spatial distribution uniformity of the rocks.This study provides a new analytical method for the mechanical evaluation of deep rocks.展开更多
AIM To investigate the efficacy and safety of mineralwater with a high content of hydrogen carbonate inpatients with heartburn.METHODS： This open, single-center, single-armclinical pilot study enrolled 50 patients, 1...AIM To investigate the efficacy and safety of mineralwater with a high content of hydrogen carbonate inpatients with heartburn.METHODS： This open, single-center, single-armclinical pilot study enrolled 50 patients, 18-64 yearsold, who had been suffering from heartburn at leasttwice a week for at least 3 mo before entering thestudy. Pharmacological treatment of heartburn was notpermitted, and patients with severe organic diseaseswere excluded. After a run-in period of one week, theparticipants received 1.5 L of the test water for thefollowing 6 wk; 300 mL with meals t.i.d., the remainderto be drunk throughout the day. During the trial, therewere five visits at the study center （screening, baseline,two interim visits and the final visit）. The efficacyendpoints included incidence and duration of heartburnepisodes per week by patient＇s self-assessment （heartburndiary） as well as changes in symptom severity asper symptom specific questionnaires [Reflux Disease Questionnaire （RDQ）; Quality of Life in Reflux andDyspepsia （QOLRAD）; Gastrointestinal Quality of LifeIndex] and overall health-related quality of life per SF-12（12-question short form） at each visit. At the end of thestudy, patients and investigators independently ratedthe overall efficacy of the test water on a 4-point Likertscale. Safety was assessed by evaluation of adverseevents （AEs）, vital signs （heart rate, blood pressure）and laboratory parameters. Changes from initial to finalexaminations were assessed by the non-parametricWilcoxon test; categorical variables were comparedusing the χ 2 test, and for more than 5 categories, by theU-test.RESULTS： Twenty-eight participants were men, 22women. The mean age of the patients in the fullanalysis set/intention-to treat population （FAS/ITT） was40.6 years. Forty-two participants completed the studyaccording to the study protocol and formed the perprotocolset （PP population）; 48 participants drank thewater at least once as requested and were analyzedas ITT population. The occurrence of heartburn wasstatistically significantly reduced at wk 6 in both the ITTand the PP populations. At wk 6, the mean number ofheartburn episodes/week decreased by 5.1 episodes（P 〈 0.001） and the mean duration of heartburnsymptoms by 19 min （ITT） （P = 0.002）. The frequencyof heartburn symptoms was reduced in 89.6% of thepatients （P 〈 0.001）, and the duration of symptoms in79.2% of patients （ITT） （P 〈 0.001）. All dimensions ofthe RDQ （heartburn, regurgitation, gastro-esophagealreflux disease symptoms, dyspepsia） showed asignificant improvement at 6 wk. Likewise, diseasespecificquality of life improved significantly （QOLRAD,GIQLI）. Overall, 89.4% of patients rated the efficacyof the test water as ＂good＂ or ＂very good＂, as did theinvestigators for 91.5% of the patients. There wereno serious AEs. After 6 wk, systolic and diastolic bloodpressure values decreased slightly but significantly [-3.5and -3.0 mmHg, respectively （P = 0.008 and P = 0,002）].Ninety-six percent of patients and investigators for thesame percentage of patients rated the tolerability of thewater as ＂good＂ or ＂very good＂.CONCLUSION： The data demonstrate effectiveness ofa hydrogen carbonate-rich mineral water in alleviatingheartburn frequency and severity, thereby improvingquality of life. The water has excellent tolerability.展开更多
A methodology for identifying and calibrating the material parameters for a coupled hydro-mechanical problem is presented in this pape r.For validation purpose,a laboratory-based water infiltration test was numericall...A methodology for identifying and calibrating the material parameters for a coupled hydro-mechanical problem is presented in this pape r.For validation purpose,a laboratory-based water infiltration test was numerically simulated using finite element method(FEM).The test was conducted using a self-designed column-type experimental device,which mimicked the wetting process of a candidate backfill material in a nuclear waste repository.The real-time measurements of key state variables(e.g.water content,relative humidity,temperature,and total stresses)were performed with the monitoring sensors along the height of cylindrical soil sample.For numerical simulation,the modified Barcelona Basic Model(BBM)along with soil-water retention model for compacted bentonite was used.It shows that the identified model parameters successfully captured the moisture migration process under an applied hydraulic gradient in a bentonite-based compacted soil sample.A comparison between the measured and predicted values of total stresses both in axial and lateral directions along with other state variables revealed that heterogeneous moisture content was distributed along the hydration-path,resulting in non-uniform stress-deformation characteristics of soil.展开更多
Background:Seven out of ten hornbill species in the Philippines are threatened with extinction.Among these is the endangered Visayan Hornbill(Penelopides panini),found on the islands of Panay and Negros.Threatened by ...Background:Seven out of ten hornbill species in the Philippines are threatened with extinction.Among these is the endangered Visayan Hornbill(Penelopides panini),found on the islands of Panay and Negros.Threatened by habitat loss and hunting,its population size is thought to have declined from 1800 individuals 20 years ago to less than 1000.However,a recent study on Negros estimated 3564 individuals across three core forest blocks.This study aims to quantify the Visayan Hornbill population size in and around the Northwest Panay Peninsula Natural Park(NWPPNP)on Panay,the largest contiguous low-elevation forest landscape remaining across its range,and its broad habitat associations across a gradient of environmental degradation.Methods:Hornbills were surveyed using 10-min distance sampling point counts(n=367)along transects(average length 1.1 km).Environmental variables were recorded along transects,while habitat was classified into primary forest,secondary forest,plantation,or open habitat.Distance software was used to estimate population densities stratified by habitat,with the overall population estimate taken as a mean of habitat density estimates weighted by habitat area.Using generalized linear mixed models,hornbill occurrence was modelled using combinations of nine environmental variables as main and two-way fixed effects.Results:Surveys covered 204.4 km^(2) of the 374.8 km^(2) Northwest Panay Peninsula.Hornbills were not recorded in plantations or open habitats.Hornbill density was significantly higher in primary forest(17.8 individuals/km~2±26.9%CV)than in secondary forest(3.7 individuals/km^(2)±33.2%CV;z=15.212,P<0.001).The overall population estimate for the NWPPNP and environs is 2109 individuals,and 2673 individuals for the entire Northwest Panay Peninsula.Hornbill presence was best explained by a model including distance from the Park boundary alongside five interaction effects and transect as a random effect.Distance,and the interaction between distance and medium-sized trees were significant predictors of hornbill presence.Conclusions:Our study evidences the habitat preference of the Visayan Hornbill,highlights the importance of the NWPPNP for the species'conservation,and provides strong evidence for re-assessing the global population size.展开更多
The Archean Eon was a time of geodynamic changes.Direct evidence of these transitions come from igneous/metaigneous rocks,which dominate cratonic segments worldwide.New data for granitoids from an Archean basement inl...The Archean Eon was a time of geodynamic changes.Direct evidence of these transitions come from igneous/metaigneous rocks,which dominate cratonic segments worldwide.New data for granitoids from an Archean basement inlier related to the Southern S?o Francisco Craton(SSFC),are integrated with geochronological,isotopic and geochemical data on Archean granitoids from the SSFC.The rocks are divided into three main geochemical groups with different ages:(1)TTG(3.02–2.77 Ga);(2)mediumto high-K granitoids(2.85–2.72 Ga);and(3)A-type granites(2.7–2.6 Ga).The juvenile to chondritic(Hf-Nd isotopes)TTG were divided into two sub-groups,TTG 1(low-HREE)and 2(high-HREE),derived from partial melting of metamafic rocks similar to those from adjacent greenstone belts.The compositional diversity within the TTG is attributed to different pressures during partial melting,supported by a positive correlation of Dy/Yb and Sr/Zr,and batch melting calculations.The proposed TTG sources are geochemically similar to basaltic rocks from modern island-arcs,indicating the presence of subduction processes concomitant with TTG emplacement.From~2.85 Ga to 2.70 Ga,the dominant rocks were K-rich granitoids.These are modeled as crustal melts of TTG,during regional metamorphism indicative of crustal thickening.Their compositional diversity is linked to:(i)differences in source composition;(ii)distinct melt fractions during partial melting;and(iii)different residual mineralogies reflecting varying P–T conditions.Post-collisional(~2.7–2.6 Ga)A-type granites reflect rifting in that they were closely followed by extension-related dyke swarms,and they are interpreted as differentiation or partial melting products of magmas derived from subduction-modified mantle.The sequence of granitoid emplacement indicates subduction-related magmatism was followed by crustal thickening,regional metamorphism and crustal melting,and post-collisional extension,similar to that seen in younger Wilson Cycles.It is compelling evidence that plate tectonics was active in this segment of Brazil from~3 Ga.展开更多
Since many industrial applications rely on the processing of densely packed and moving granular ma-terial,obtaining bulk internal information on the particle movement inside the reactors is of great importance.Such in...Since many industrial applications rely on the processing of densely packed and moving granular ma-terial,obtaining bulk internal information on the particle movement inside the reactors is of great importance.Such information can be delivered by Positron Emission Particle Tracking(PEPT).By marking pellets with a positron-emitting radioisotope,the position of these tracer particles can be determined via the time-of-flight differences of the emitted gamma-ray pairs.The current paper proposes a PET-like detector system based on cost-effective organic plastic scintillators instead of the more common but expensive inorganic scintillators.This system is currently under construction and was tested for its resolution and efficiency in this simulation study.Using Monte Carlo simulations and the software toolkit Geant4,three different geometries(an empty glass box,a generic grate system,and a cubic box of 1 m3 completely filled with pellets)were investigated,leading to a spatial resolution in the millimeter range and an efficiency,defined as the ratio of reconstructed decay locations to simulated decays,of 2.7%,1.4%,and 0.3%.展开更多
This work is the second part of a simulation study investigating the processing of densely packed and moving granular assemblies by positron emission particle tracking (PEPT).Since medical positron emission tomography...This work is the second part of a simulation study investigating the processing of densely packed and moving granular assemblies by positron emission particle tracking (PEPT).Since medical positron emission tomography (PET) scanners commonly used for PEPT are very expensive,a PET-like detector system based on cost-effective organic plastic scintillator bars is being developed and tested for its capabilities.In this context,the spatial resolution of a resting positron source,a source moving on a freely designed model path,and a particle motion given by a discrete element method (DEM) simulation is studied using Monte Carlo simulations and the software toolkit Geant4.This not only extended the simulation and reconstruction to a moving source but also significantly improved the spatial resolution compared to previous work by adding oversampling and iteration to the reconstruction algorithm.Furthermore,in the case of a source following a trajectory developed from DEM simulations,a very good resolution of about 1 mm in all three directions and an average 3D deviation between simulated and reconstructed events of 2.3 mm could be determined.Thus,the resolution for realistic particle motion within the generic grate system (which is the test rig for further experimental studies) is well below the smallest particle size.The simulation of the dependence of the reconstruction accuracy on tracer particle location revealed a nearly constant efficiency within the entire detector system,which demonstrates that boundary effects can be neglected.展开更多
The environmental challenges and growing energy demand have promoted the development of renewable energy,including solar,tidal,and wind.The next-generation electrochemical energy storage(EES),incorporating flow batter...The environmental challenges and growing energy demand have promoted the development of renewable energy,including solar,tidal,and wind.The next-generation electrochemical energy storage(EES),incorporating flow battery(FB)and metal-based battery(MB,Li,Na,Zn,Mg,etc.)received more attention.The flammable electrolytes in nonaqueous batteries have raised serious safety hazards and more unconventional electrolyte systems have been proposed recently.An emerging class of electrolytes,eutectic electrolytes have been reported in many batteries due to the facile preparation,concentrated states,and unique ion transport properties.In FB,eutectic electrolytes can significantly increase the energy density by promoting the molar ratio of redox active materials.In MB,eutectic electrolytes reduce the vapor pressure and toxicity,inhibit metal dendrites growth,and enlarge the electrochemical window.In this review,we summarize the progress status of different eutectic electrolytes on both FBs and MBs.We expect this review can supply the guidance for the application of eutectic electrolytes in EES.展开更多
The huge atomic heterogeneity of high-entropy materials along with a possibility to unravel the behavior of individual components at the atomic scale suggests a great promise in designing new compositionally complex s...The huge atomic heterogeneity of high-entropy materials along with a possibility to unravel the behavior of individual components at the atomic scale suggests a great promise in designing new compositionally complex systems with the desired multifunctionality.Herein,we apply multi-edge X-ray absorption spectroscopy(extended X-ray absorption fine structure(EXAFS),Xray absorption near edge structure(XANES),and X-ray magnetic circular dichroism(XMCD))to probe the structural,electronic,and magnetic properties of all individual constituents in the single-phase face-centered cubic(fcc)-structured nanocrystalline thin film of Cr_(20)Mn_(26)Fe_(18)Co_(19)Ni_(17)(at.%)high-entropy alloy on the local scale.The local crystallographic ordering and componentdependent lattice displacements were explored within the reverse Monte Carlo approach applied to EXAFS spectra collected at the K absorption edges of several constituents at room temperature.A homogeneous short-range fcc atomic environment around the absorbers of each type with very similar statistically averaged interatomic distances(2.54-2.55Å)to their nearest-neighbors and enlarged structural relaxations of Cr atoms were revealed.XANES and XMCD spectra collected at the L2,3 absorption edges of all principal components at low temperature from the oxidized and in situ cleaned surfaces were used to probe the oxidation states,the changes in the electronic structure,and magnetic behavior of all constituents at the surface and in the sub-surface volume of the film.The spin and orbital magnetic moments of Fe,Co,and Ni components were quantitatively evaluated.The presence of magnetic phase transitions and the co-existence of different magnetic phases were uncovered by conventional magnetometry in a broad temperature range.展开更多
In this paper,an electrostatic compliant mechanical amplifier intended for force-compensated displacement amplification in MEMS sensor applications is described.Usually,mechanical transformers that enhance a small inp...In this paper,an electrostatic compliant mechanical amplifier intended for force-compensated displacement amplification in MEMS sensor applications is described.Usually,mechanical transformers that enhance a small input displacement into a large output displacement generate large forces at the input of the transformer.The microsystem proposed here allows for the reduction and compensation of the input stiffness of the amplifier and any mechanical components connected to it while providing a constant amplification ratio at the same time.The amplifying mechanism features bidirectional electrostatic anti-springs enabling the control of the stiffness by applying a constant DC voltage.The electrode design of the anti-springs and its influence on the force-displacement characteristic,the side instability and the maximal displacement are studied through analytical approaches and supported by FEA and by experiments.Based on the derived models,a compliant electromechanical amplifier is developed,featuring an amplification ratio of 50.For this amplifier the initial input stiffness of 422 N/m could be reduced to 6.8 N/m by applying a voltage of 100 V.As an additional application,we show how the amplifier can be used as a mechanical force sensor with tuneable sensitivity,where the forces at the input are transformed into large output displacements.Through experiments,we show how the sensitivity can be adjusted and increased by a factor of 25 by applying a voltage at the anti-springs.展开更多
基金NSFC Grants(12072063,11972109)Grant of State Key Laboratory of Structural Analysis for Industrial Equipment(S22403)+1 种基金National Key Research and Development Program of China(2020YFB1708304)Alexander von Humboldt Foundation(1217594).
文摘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 problems.In order to solve more realistic problems,a three-dimensional MsSBFEM is further developed in this article.In 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 accuracy.Besides,the Temporally Piecewise Adaptive Algorithm(TPAA)is used to maintain the computational accuracy of multiscale analysis by adaptive calculation in time domain.The results of numerical examples show that the proposed method can significantly reduce the DOFs for three-dimensional viscoelastic analysis with good accuracy.For instance,the DOFs can be reduced by 9021 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.
基金support of the Deutsche Forschungsgemeinschaft(DFG),Grant no.AL 1343/7–1,AL 1343/8–1,Yi 103/3–1。
文摘Critical properties of metallic materials,such as the yield stress,corrosion resistance and ductility depend on the microstructure and its grain size and size distribution.Solute atoms that favorably segregate to grain boundaries produce a pinning atmosphere that exerts a drag pressure on the boundary motion,which strongly affects the grain growth behavior during annealing.In the current work,the characteristics of grain growth in an annealed Mg-1 wt.%Mn-1 wt.%Nd magnesium alloy were investigated by advanced experimental and modeling techniques.Systematic quasi in-situ orientation mappings with a scanning electron microscope were performed to track the evolution of local and global microstructural characteristics as a function of annealing time.Solute segregation at targeted grain boundaries was measured using three-dimensional atom probe tomography.Level-set computer simulations were carried with different setups of driving forces to explore their contribution to the microstructure development with and without solute drag.The results showed that the favorable growth advantage for some grains leading to a transient stage of abnormal grain growth is controlled by several drivers with varying importance at different stages of annealing.For longer annealing times,residual dislocation density gradients between large and smaller grains are no longer important,which leads to microstructure stability due to predominant solute drag.Local fluctuations in residual dislocation energy and solute concentration near grain boundaries cause different boundary segments to migrate at different rates,which affects the average growth rate of large grains and their evolved shape.
基金support by the Deutsche Forschungsgemeinschaft(DFG)through the Heisenberg program(Project No.433075039)。
文摘For high-precision pulsar timing analysis and low-frequency gravitational wave detection,it is essential to accurately determine pulsar pulse times of arrival(ToAs)and associated uncertainties.To measure the ToAs and their uncertainties,various cross-correlation-based techniques can be employed.We develop methodologies to investigate the impact of the template-matching method,profile shape,signal-to-noise ratio of both template and observation on ToA uncertainties.These methodologies are then applied to data from the International Pulsar Timing Array.We demonstrate that the Fourier domain Markov chain Monte Carlo method is generally superior to other methods,while the Gaussian interpolation shift method outperforms other methods in certain cases,such as profiles with large duty cycles or smooth profiles without sharp features.However,it is important to note that our study focuses solely on ToA uncertainty,and the optimal method for determining both ToA and ToA uncertainty may differ.
基金This work was financially supported by the National Nat-ural Science Foundation of China(Nos.51921003,51775275 and 51905363)the Natural Science Foundation of Jiangsu Province(No.BK20190940)+1 种基金the National Major Science and Technology Projects of China(No.2017-VII-0002-0095)the Six Talents Summit Project in Jiangsu Province(No.JXQC-002).
文摘The service performance of the turbine blade root of an aero-engine depends on the microstructures in its superficial layer.This work investigated the surface deformation structures of turbine blade root of single crystal nickel-based superalloy produced under different creep feed grinding conditions.Gradient microstructures in the superficial layer were clarified and composed of a severely deformed layer(DFL)with nano-sized grains(48–67 nm)at the topmost surface,a DFL with submicron-sized grains(66–158 nm)and micron-sized laminated structures at the subsurface,and a dislocation accumulated layer extending to the bulk material.The formation of such gradient microstructures was found to be related to the graded variations in the plastic strain and strain rate induced in the creep feed grinding process,which were as high as 6.67 and 8.17×10^(7)s^(−1),respectively.In the current study,the evolution of surface gradient microstructures was essentially a transition process from a coarse single crystal to nano-sized grains and,simultaneously,from one orientation of a single crystal to random orientations of polycrystals,during which the dislocation slips dominated the creep feed grinding induced microstructure deformation of single crystal nickel-based superalloy.
文摘Plasticity of cerebellar Purkinje cells(PC)is influenced by progeste rone via the classical progeste rone receptors PR-A and PR-B by stimulating dendritogenesis,spinogenesis,and synaptogenesis in these cells.Dissociated PC cultures were used to analyze progeste rone effects at a molecular level on the voltage-gated T-type-Ca^(2+)-channels Ca_(v)3.1,Ca_(v)3.2,and Ca_(v)3.3 as they helped determine neuronal plasticity by regulating Ca^(2+)-influx in neuronal cells.The results showed direct effects of progesterone on the mRNA expression of T-type-Ca^(2+)-channels,as well as on the protein kinases A and C being involved in downstream signaling pathways that play an important role in neuronal plasticity.For the mRNA expression studies of T-type-Ca^(2+)-channels and protein kinases of the signaling cascade,laser microdissection and purified PC cultures of diffe rent maturation stages were used.Immunohistochemical staining was also performed to characte rize the localization of T-type-Ca^(2+)-channels in PC.Expe rimental progesterone treatment was performed on the purified PC culture for 24 and 48 hours.Our results show that progesterone increases the expression of Ca_(v)3.1 and Ca_(v)3.3 and associated protein kinases A and Cin PC at the mRNA level within 48 hours after treatment at latest.These effects extend the current knowledge of the function of progesterone in the central nervous system and provide an explanatory approach for its influence on neuronal plasticity.
基金This research was funded by the National Natural Science Foundation of China(21976054)the Fundamental Research Funds for the Central Universities(2020MS036)the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)within the collaborative research centre/transregio 247"Heterogeneous Oxidation Catalysis in the Liquid Phase,f.
文摘Photocatalytic oxidation of alcohols has received more and more attention in recent years following the numerous studies on the degradation of pollutants, hydrogen evolution, and CO_(2) reduction by photocatalysis. Instead of the total oxidation of organics in the degradation process, the photo-oxidation of alcohols aims at the selective conversion of alcohols to produce carbonyl/acid compounds. Promising results have been achieved in designing the catalysts and reaction system, as well as in the mechanistic investigations in the past few years. This review summarizes the state-of-the-art progress in the photo-oxidation of alcohols, including the development of photocatalysts and cocatalysts, reaction conditions including the solvent and the atmosphere, and the exploration of mechanisms with scavengers experiment, electron paramagnetic resonance (EPR) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The challenges and outlook for the further research in this field are also discussed.
基金financially supported by the National Key R&D Program of China (No. 2016YFC0600801)the Major Scientific and Technological Innovation Project of Shandong Province (Nos. 2019SDZY02 and 2019SDZY05)+1 种基金the National Natural Science Foundation of China (Nos. 52074021 and 51774021)China Scholarship Council (No. 202006460024)
文摘For deep rock mechanics and subsurface engineering,accurately characterizing and evaluating rock heterogeneity as well as analyzing the correlation between the heterogeneity and physical and mechanical properties of rocks are critical.This study investigated the characteristics of acoustic emission signals produced in the process of strong and weak phase damage to rocks.The failure mechanisms of the strong and weak phases were analyzed by performing Brazilian splitting tests on different metagabbros and granites.The strong-weak phase ratio of the rocks and the uniformity of their spatial distribution were characterized.Test results show that as the feldspar develops,the strong-phase ratio of the metagabbro increases.However,the spatial distribution of feldspar minerals in the metagabbro becomes less uniform.The mineral spatial distribution uniformity in the altered granite is good;however,its strong-phase ratio is low.Furthermore,the strong-phase ratio of the typical granite is high;however,its mineral spatial distribution uniformity is poor.Moreover,uniaxial and triaxial test results show that the peak strength and elastic modulus of the rocks are related to the strong-weak phase ratio and mineral spatial distribution uniformity of the rocks.This study provides a new analytical method for the mechanical evaluation of deep rocks.
基金Supported by Deutsche Heilbrunnen im Verband Deutscher Mineralbrunnen e.V.,Kennedyallee 28,53175 Bonn,Germany,www.vdm-bonn.de
文摘AIM To investigate the efficacy and safety of mineralwater with a high content of hydrogen carbonate inpatients with heartburn.METHODS： This open, single-center, single-armclinical pilot study enrolled 50 patients, 18-64 yearsold, who had been suffering from heartburn at leasttwice a week for at least 3 mo before entering thestudy. Pharmacological treatment of heartburn was notpermitted, and patients with severe organic diseaseswere excluded. After a run-in period of one week, theparticipants received 1.5 L of the test water for thefollowing 6 wk; 300 mL with meals t.i.d., the remainderto be drunk throughout the day. During the trial, therewere five visits at the study center （screening, baseline,two interim visits and the final visit）. The efficacyendpoints included incidence and duration of heartburnepisodes per week by patient＇s self-assessment （heartburndiary） as well as changes in symptom severity asper symptom specific questionnaires [Reflux Disease Questionnaire （RDQ）; Quality of Life in Reflux andDyspepsia （QOLRAD）; Gastrointestinal Quality of LifeIndex] and overall health-related quality of life per SF-12（12-question short form） at each visit. At the end of thestudy, patients and investigators independently ratedthe overall efficacy of the test water on a 4-point Likertscale. Safety was assessed by evaluation of adverseevents （AEs）, vital signs （heart rate, blood pressure）and laboratory parameters. Changes from initial to finalexaminations were assessed by the non-parametricWilcoxon test; categorical variables were comparedusing the χ 2 test, and for more than 5 categories, by theU-test.RESULTS： Twenty-eight participants were men, 22women. The mean age of the patients in the fullanalysis set/intention-to treat population （FAS/ITT） was40.6 years. Forty-two participants completed the studyaccording to the study protocol and formed the perprotocolset （PP population）; 48 participants drank thewater at least once as requested and were analyzedas ITT population. The occurrence of heartburn wasstatistically significantly reduced at wk 6 in both the ITTand the PP populations. At wk 6, the mean number ofheartburn episodes/week decreased by 5.1 episodes（P 〈 0.001） and the mean duration of heartburnsymptoms by 19 min （ITT） （P = 0.002）. The frequencyof heartburn symptoms was reduced in 89.6% of thepatients （P 〈 0.001）, and the duration of symptoms in79.2% of patients （ITT） （P 〈 0.001）. All dimensions ofthe RDQ （heartburn, regurgitation, gastro-esophagealreflux disease symptoms, dyspepsia） showed asignificant improvement at 6 wk. Likewise, diseasespecificquality of life improved significantly （QOLRAD,GIQLI）. Overall, 89.4% of patients rated the efficacyof the test water as ＂good＂ or ＂very good＂, as did theinvestigators for 91.5% of the patients. There wereno serious AEs. After 6 wk, systolic and diastolic bloodpressure values decreased slightly but significantly [-3.5and -3.0 mmHg, respectively （P = 0.008 and P = 0,002）].Ninety-six percent of patients and investigators for thesame percentage of patients rated the tolerability of thewater as ＂good＂ or ＂very good＂.CONCLUSION： The data demonstrate effectiveness ofa hydrogen carbonate-rich mineral water in alleviatingheartburn frequency and severity, thereby improvingquality of life. The water has excellent tolerability.
基金the German Research Foundation(DFG)for the financial support(Grant No.SCHA 675/17-1)。
文摘A methodology for identifying and calibrating the material parameters for a coupled hydro-mechanical problem is presented in this pape r.For validation purpose,a laboratory-based water infiltration test was numerically simulated using finite element method(FEM).The test was conducted using a self-designed column-type experimental device,which mimicked the wetting process of a candidate backfill material in a nuclear waste repository.The real-time measurements of key state variables(e.g.water content,relative humidity,temperature,and total stresses)were performed with the monitoring sensors along the height of cylindrical soil sample.For numerical simulation,the modified Barcelona Basic Model(BBM)along with soil-water retention model for compacted bentonite was used.It shows that the identified model parameters successfully captured the moisture migration process under an applied hydraulic gradient in a bentonite-based compacted soil sample.A comparison between the measured and predicted values of total stresses both in axial and lateral directions along with other state variables revealed that heterogeneous moisture content was distributed along the hydration-path,resulting in non-uniform stress-deformation characteristics of soil.
基金funded by the Mohamed bin Zayed Species Conservation Fund(project 192514132)Bristol Zoological SocietyDK was employed by Bristol Zoological Society to oversee the project,and HM,BT and AF worked as contractors for Bristol Zoological Society during the survey duration。
文摘Background:Seven out of ten hornbill species in the Philippines are threatened with extinction.Among these is the endangered Visayan Hornbill(Penelopides panini),found on the islands of Panay and Negros.Threatened by habitat loss and hunting,its population size is thought to have declined from 1800 individuals 20 years ago to less than 1000.However,a recent study on Negros estimated 3564 individuals across three core forest blocks.This study aims to quantify the Visayan Hornbill population size in and around the Northwest Panay Peninsula Natural Park(NWPPNP)on Panay,the largest contiguous low-elevation forest landscape remaining across its range,and its broad habitat associations across a gradient of environmental degradation.Methods:Hornbills were surveyed using 10-min distance sampling point counts(n=367)along transects(average length 1.1 km).Environmental variables were recorded along transects,while habitat was classified into primary forest,secondary forest,plantation,or open habitat.Distance software was used to estimate population densities stratified by habitat,with the overall population estimate taken as a mean of habitat density estimates weighted by habitat area.Using generalized linear mixed models,hornbill occurrence was modelled using combinations of nine environmental variables as main and two-way fixed effects.Results:Surveys covered 204.4 km^(2) of the 374.8 km^(2) Northwest Panay Peninsula.Hornbills were not recorded in plantations or open habitats.Hornbill density was significantly higher in primary forest(17.8 individuals/km~2±26.9%CV)than in secondary forest(3.7 individuals/km^(2)±33.2%CV;z=15.212,P<0.001).The overall population estimate for the NWPPNP and environs is 2109 individuals,and 2673 individuals for the entire Northwest Panay Peninsula.Hornbill presence was best explained by a model including distance from the Park boundary alongside five interaction effects and transect as a random effect.Distance,and the interaction between distance and medium-sized trees were significant predictors of hornbill presence.Conclusions:Our study evidences the habitat preference of the Visayan Hornbill,highlights the importance of the NWPPNP for the species'conservation,and provides strong evidence for re-assessing the global population size.
基金Fundacao Carlos Chagas de AmparoàPesquisa do Estado do Rio de Janeiro(FAPERJ),for providing him a post-doctoral fellowship(E-26/202.084/2020 and 2020.03701.1).the National Council for Scientific Development(CNPq)for financial support.CNPq for his Productivity on Research grant(#311106/2020-0)。
文摘The Archean Eon was a time of geodynamic changes.Direct evidence of these transitions come from igneous/metaigneous rocks,which dominate cratonic segments worldwide.New data for granitoids from an Archean basement inlier related to the Southern S?o Francisco Craton(SSFC),are integrated with geochronological,isotopic and geochemical data on Archean granitoids from the SSFC.The rocks are divided into three main geochemical groups with different ages:(1)TTG(3.02–2.77 Ga);(2)mediumto high-K granitoids(2.85–2.72 Ga);and(3)A-type granites(2.7–2.6 Ga).The juvenile to chondritic(Hf-Nd isotopes)TTG were divided into two sub-groups,TTG 1(low-HREE)and 2(high-HREE),derived from partial melting of metamafic rocks similar to those from adjacent greenstone belts.The compositional diversity within the TTG is attributed to different pressures during partial melting,supported by a positive correlation of Dy/Yb and Sr/Zr,and batch melting calculations.The proposed TTG sources are geochemically similar to basaltic rocks from modern island-arcs,indicating the presence of subduction processes concomitant with TTG emplacement.From~2.85 Ga to 2.70 Ga,the dominant rocks were K-rich granitoids.These are modeled as crustal melts of TTG,during regional metamorphism indicative of crustal thickening.Their compositional diversity is linked to:(i)differences in source composition;(ii)distinct melt fractions during partial melting;and(iii)different residual mineralogies reflecting varying P–T conditions.Post-collisional(~2.7–2.6 Ga)A-type granites reflect rifting in that they were closely followed by extension-related dyke swarms,and they are interpreted as differentiation or partial melting products of magmas derived from subduction-modified mantle.The sequence of granitoid emplacement indicates subduction-related magmatism was followed by crustal thickening,regional metamorphism and crustal melting,and post-collisional extension,similar to that seen in younger Wilson Cycles.It is compelling evidence that plate tectonics was active in this segment of Brazil from~3 Ga.
基金funded by the DeutscheForschungsgemeinschaft(DFG,German Research Foundation)through 422037413-CRC/TRR 287"BULK-REACTION"。
文摘Since many industrial applications rely on the processing of densely packed and moving granular ma-terial,obtaining bulk internal information on the particle movement inside the reactors is of great importance.Such information can be delivered by Positron Emission Particle Tracking(PEPT).By marking pellets with a positron-emitting radioisotope,the position of these tracer particles can be determined via the time-of-flight differences of the emitted gamma-ray pairs.The current paper proposes a PET-like detector system based on cost-effective organic plastic scintillators instead of the more common but expensive inorganic scintillators.This system is currently under construction and was tested for its resolution and efficiency in this simulation study.Using Monte Carlo simulations and the software toolkit Geant4,three different geometries(an empty glass box,a generic grate system,and a cubic box of 1 m3 completely filled with pellets)were investigated,leading to a spatial resolution in the millimeter range and an efficiency,defined as the ratio of reconstructed decay locations to simulated decays,of 2.7%,1.4%,and 0.3%.
基金funded by the Deutsche Forschungsgemeinschaft (DFG,German Research Foundation)-Project-ID 422037413-TRR 287.
文摘This work is the second part of a simulation study investigating the processing of densely packed and moving granular assemblies by positron emission particle tracking (PEPT).Since medical positron emission tomography (PET) scanners commonly used for PEPT are very expensive,a PET-like detector system based on cost-effective organic plastic scintillator bars is being developed and tested for its capabilities.In this context,the spatial resolution of a resting positron source,a source moving on a freely designed model path,and a particle motion given by a discrete element method (DEM) simulation is studied using Monte Carlo simulations and the software toolkit Geant4.This not only extended the simulation and reconstruction to a moving source but also significantly improved the spatial resolution compared to previous work by adding oversampling and iteration to the reconstruction algorithm.Furthermore,in the case of a source following a trajectory developed from DEM simulations,a very good resolution of about 1 mm in all three directions and an average 3D deviation between simulated and reconstructed events of 2.3 mm could be determined.Thus,the resolution for realistic particle motion within the generic grate system (which is the test rig for further experimental studies) is well below the smallest particle size.The simulation of the dependence of the reconstruction accuracy on tracer particle location revealed a nearly constant efficiency within the entire detector system,which demonstrates that boundary effects can be neglected.
基金National Natural Science Foundation of China,Grant/Award Numbers:22279133,22393964International Partnership Program of the Chinese Academy of Sciences,Grant/Award Number:121421KYSB20210028Liaoning Binhai Laboratory,Grant/Award Number:LBLF202305。
文摘The environmental challenges and growing energy demand have promoted the development of renewable energy,including solar,tidal,and wind.The next-generation electrochemical energy storage(EES),incorporating flow battery(FB)and metal-based battery(MB,Li,Na,Zn,Mg,etc.)received more attention.The flammable electrolytes in nonaqueous batteries have raised serious safety hazards and more unconventional electrolyte systems have been proposed recently.An emerging class of electrolytes,eutectic electrolytes have been reported in many batteries due to the facile preparation,concentrated states,and unique ion transport properties.In FB,eutectic electrolytes can significantly increase the energy density by promoting the molar ratio of redox active materials.In MB,eutectic electrolytes reduce the vapor pressure and toxicity,inhibit metal dendrites growth,and enlarge the electrochemical window.In this review,we summarize the progress status of different eutectic electrolytes on both FBs and MBs.We expect this review can supply the guidance for the application of eutectic electrolytes in EES.
文摘The huge atomic heterogeneity of high-entropy materials along with a possibility to unravel the behavior of individual components at the atomic scale suggests a great promise in designing new compositionally complex systems with the desired multifunctionality.Herein,we apply multi-edge X-ray absorption spectroscopy(extended X-ray absorption fine structure(EXAFS),Xray absorption near edge structure(XANES),and X-ray magnetic circular dichroism(XMCD))to probe the structural,electronic,and magnetic properties of all individual constituents in the single-phase face-centered cubic(fcc)-structured nanocrystalline thin film of Cr_(20)Mn_(26)Fe_(18)Co_(19)Ni_(17)(at.%)high-entropy alloy on the local scale.The local crystallographic ordering and componentdependent lattice displacements were explored within the reverse Monte Carlo approach applied to EXAFS spectra collected at the K absorption edges of several constituents at room temperature.A homogeneous short-range fcc atomic environment around the absorbers of each type with very similar statistically averaged interatomic distances(2.54-2.55Å)to their nearest-neighbors and enlarged structural relaxations of Cr atoms were revealed.XANES and XMCD spectra collected at the L2,3 absorption edges of all principal components at low temperature from the oxidized and in situ cleaned surfaces were used to probe the oxidation states,the changes in the electronic structure,and magnetic behavior of all constituents at the surface and in the sub-surface volume of the film.The spin and orbital magnetic moments of Fe,Co,and Ni components were quantitatively evaluated.The presence of magnetic phase transitions and the co-existence of different magnetic phases were uncovered by conventional magnetometry in a broad temperature range.
基金This work has been funded by the German Federal Ministry of Education and Research under contract 16ES1063(ForMikro-upFUSE).The authors thank Matthias Paul Kroll for his support with the measurements in the cleanroom.The microsystems were partly fabricated with etching equipment provided by the Center for Interface-Dominated High-Performance Materials(ZGH).We acknowldege support by the Open Access Publication Funds of the Ruhr-Universität Bochum.
文摘In this paper,an electrostatic compliant mechanical amplifier intended for force-compensated displacement amplification in MEMS sensor applications is described.Usually,mechanical transformers that enhance a small input displacement into a large output displacement generate large forces at the input of the transformer.The microsystem proposed here allows for the reduction and compensation of the input stiffness of the amplifier and any mechanical components connected to it while providing a constant amplification ratio at the same time.The amplifying mechanism features bidirectional electrostatic anti-springs enabling the control of the stiffness by applying a constant DC voltage.The electrode design of the anti-springs and its influence on the force-displacement characteristic,the side instability and the maximal displacement are studied through analytical approaches and supported by FEA and by experiments.Based on the derived models,a compliant electromechanical amplifier is developed,featuring an amplification ratio of 50.For this amplifier the initial input stiffness of 422 N/m could be reduced to 6.8 N/m by applying a voltage of 100 V.As an additional application,we show how the amplifier can be used as a mechanical force sensor with tuneable sensitivity,where the forces at the input are transformed into large output displacements.Through experiments,we show how the sensitivity can be adjusted and increased by a factor of 25 by applying a voltage at the anti-springs.
