This article investigates the mechanical responses and acoustic emission(AE)characteristics of sandstone under the triaxial differential cyclic loading(DCL)at different unloading rates of confining stress.The test res...This article investigates the mechanical responses and acoustic emission(AE)characteristics of sandstone under the triaxial differential cyclic loading(DCL)at different unloading rates of confining stress.The test results indicate that strength of rock specimens under different stress paths of triaxial unloading confining stress-differential cyclic loading(TUCS-DCL)can be fitted by the Mohr–Coulomb,Hoek–Brown,and Bieniawski criteria.The confining stress unloading rate can dominate the radial strain rate,while the axial DCL pattern has an unpronounced effect.The confining stress unloading rate affects the energy evolution in radial and axial directions of specimens,with the ratio of radially released energy to axially consumed energy fluctuating more significantly during the fast unloading of confining stress,the valley value of the ratio can serve as a precursor for failure.The confining stress unloading rate has no significant effect on stress–strain phase shift,while axial rapid-loading-slow-unloading can correspond to a larger magnitude of phase shift.AE signals begin to significantly increase after the confining stress is unloaded to zero,and a notable Kaiser effect is observed during cyclic loading preceding the failure.展开更多
The pseudo-excitation method combined with the integral transform method (PEM-ITM) is presented to investigate the ground vibration of a coupled track-soil system induced by moving random loads. Commonly in the track ...The pseudo-excitation method combined with the integral transform method (PEM-ITM) is presented to investigate the ground vibration of a coupled track-soil system induced by moving random loads. Commonly in the track model, the rail, sleepers, rail pads, and ballast are modelled as an infinite Euler beam, discretely distributed masses, discretely distributed vertical springs, and a viscoelastic layer, respectively. The soil is regarded as a homogenous isotropic half-space coupled with the track using the boundary condition at the surface of the ground. By introducing a pseudo-excitation, the random vibration analysis of the coupled system is converted into a harmonic analysis. The analytical form of evolutionary power spectral density responses of the simplified coupled track-soil system under a random moving load is derived in the frequency/wavenumber domain by PEM-ITM. In the numerical examples, the effects of different parameters, such as the moving speed, the soil properties, and the coherence of moving loads, on the ground response are investigated.展开更多
The plastic deformation of amorphous alloys is well known to be localized into shear bands(SBs),which are believed to stem from the atomic-scale flow defects,i.e.,shear transformation zones(STZs).Yet,the bridge betwee...The plastic deformation of amorphous alloys is well known to be localized into shear bands(SBs),which are believed to stem from the atomic-scale flow defects,i.e.,shear transformation zones(STZs).Yet,the bridge between the mesoscopic SBs and the atomic-scale STZs remains poorly understood.In this work,through thermally activating pronouncedβrelaxations in the well-designed crystalline-layer confined amorphous(CLCA)Ni W alloy films,we experimentally captured and observed an intermediate nanosized structure termed as“nano shear bands”(NSBs)with a typical size of 1–2 nm in thickness and5–10 nm in length.The influences of such NSB structures on the macroscale deformation behavior were systematically investigated.It was found that NSBs lead to both hardening and toughening effects for the CLCA films,as they promote multiple and controlled shear banding deformation,which results in enhanced crystallization.The intermediate NSB structure could connect the microstructural characteristics and macroscopic plasticity in amorphous alloys and may provide new insights for understanding the microscopic deformation mechanism of amorphous alloys as well as tuning/designing their properties.展开更多
Broadband lasers have been proposed as future drivers of inertial confined fusion(ICF)to enhance the laser-target coupling efficiency via the mitigation of various parametric instabilities.The physical mechanisms invo...Broadband lasers have been proposed as future drivers of inertial confined fusion(ICF)to enhance the laser-target coupling efficiency via the mitigation of various parametric instabilities.The physical mechanisms involved have been explored recently,but are not yet fully understood.Here,stimulated Raman scattering(SRS)as one of the key parametric instabilities is investigated theoretically and numerically for a broadband laser propagating in homogeneous plasma in multidimensional geometry.The linear SRS growth rate is derived as a function of scattering angles for two monochromatic laser beams with a fixed frequency differenceδω.Ifδω/ω_(0)∼1%,withω0 the laser frequency,these two laser beams may be decoupled in stimulating backward SRS while remaining coupled for sideward SRS at the laser intensities typical for ICF.Consequently,side-scattering may dominate over backward SRS for two-color laser light.This finding of SRS transition from backward to sideward SRS is then generalized for a broadband laser with a few-percent bandwidth.Particle-in-cell simulations demonstrate that with increasing laser bandwidth,the sideward SRS gradually becomes dominant over the backward SRS.Since sideward SRS is very efficient in producing harmful hot electrons,attention needs to be paid on this effect if ultra-broadband lasers are considered as next-generation ICF drivers.展开更多
This work presents experimental tests based on coal collected from a coal mine based underground water reservoir(CMUWR).The mechanical responses of dry and water-soaked coal samples under the complex normal and shear ...This work presents experimental tests based on coal collected from a coal mine based underground water reservoir(CMUWR).The mechanical responses of dry and water-soaked coal samples under the complex normal and shear stresses under multi-amplitude and variable frequency is investigated.The experimental results reveal the effects of stress path,water soaking and frequency on deformation,energy dissipation,secant modulus and shear failure surface roughness.The experimental results show that when normal and shear stresses are applied simultaneously,there is a significant competitive relationship between them.On the dominant side,the strain rate will be significantly increased.The sample under a loading frequency of 0.2 Hz exhibits a longer fatigue life.During the cyclic shear test,the shear strain of the water-soaked sample is higher than that of the dry samples.The average roughness coefficient of failure surface exhibits an increasing pattern with increase in shear strength,the elevated roughness of a shear surface is advantageous in constraining shear displacements of specimens,thereby lowering the energy dissipation.This study can provide theoretical and practical implications for a long-term safety evaluation of CMUWR.展开更多
It is generally believed that coronal mass ejections(CMEs)have magnetic flux rope structures because of their helical shapes.However,only about 30%–40%of interplanetary CMEs(ICMEs)have a local magnetic flux rope stru...It is generally believed that coronal mass ejections(CMEs)have magnetic flux rope structures because of their helical shapes.However,only about 30%–40%of interplanetary CMEs(ICMEs)have a local magnetic flux rope structure.The usual explanations are that the spacecraft only crossed the flank of the ropes and failed to detect the complete magnetic flux rope structure or that some processes destroyed these magnetic flux rope structures.Several studies suggest that some ICMEs inherently possess disordered magnetic fields and consequently exhibit no magnetic flux-rope structures.We introduce a special kind of ICME which has a low magnetic field magnitude and stable magnetic field direction,relatively fast expansion speed,and lower proton temperature and density.All three of the measured magnetic field components are relatively stable.We want to know whether these ICMEs also have magnetic flux rope structures or not.We identified 20 special ICMEs and analyzed their evolution based on their observed characteristics.We took a special ICME as an example,which had an apparent rope configuration at 1 au but evolved to a special ICME at 5.4 au,to illustrate that this kind of ICME could come from magnetic clouds(MCs)whose rope structure had been being stretched due to expansion.We inferred that the missing obvious flux rope structure may be due to the expansion of MCs,not the flank crossing effect.However,more than 50%of the events were associated with the dominant x-component of the magnetic field,which indicates a leg crossing.Therefore,the detection of part of these special ICMEs may also be the result of the leg-crossing effect.展开更多
A hallmark of all forms of neurodegenerative diseases is impairment of neuronal functions,and in many cases neuronal cell death.Although the etiology of neurodegenerative diseases may be distinct,different diseases di...A hallmark of all forms of neurodegenerative diseases is impairment of neuronal functions,and in many cases neuronal cell death.Although the etiology of neurodegenerative diseases may be distinct,different diseases display a similar pathogenesis,for example abnormal immunity within the central nervous system(CNS),activation of macrophage/microglia and the involvement of proinflammatory cytokines.Recent studies show that neurons in a neurodegenerative state undergo a highly regulated programmed cell death,also called apoptosis.TNF-related apoptosis-inducing ligand(TRAIL),a member of the TNF family,has been shown to be involved in apoptosis during many diseases.As one member of a death ligand family,TRAIL was originally thought to target only tumor cells and was not present in CNS.However,recent data showed that TRAIL was unregulated in HIV-1-infected and immune-activated macrophages,a major disease inducing cell during HIV-1-assoeiated dementia(HAD).TRAIL is also induced on neuron by β-amyloid protein,an important pathogen for Alzheimer's disease.In this review,we summarize the possible common aspects that TRAIL involved those neurodegenerative diseases,TRAIL induced apoptosis signaling in the CNS cells,and specific role of TRAIL in individual diseases.Cellular & Molecular Immunology.2005;2(2):113-122.展开更多
Background Each GECAM satellite payload contains 25 gamma-ray detectors(GRDs),which can detect gamma-rays and particles and can roughly localize the Gamma-Ray Bursts(GRBs).GRD was designed using lanthanum bromide(LaBr...Background Each GECAM satellite payload contains 25 gamma-ray detectors(GRDs),which can detect gamma-rays and particles and can roughly localize the Gamma-Ray Bursts(GRBs).GRD was designed using lanthanum bromide(LaBr3)crystal as the sensitive material with the rear end coupled with silicon photomultiplier(SiPM)array for readout.Purpose In aerospace engineering design of GRD,there are many key points to be studied.In this paper,we present the specific design scheme of GRD,the assembly and the performance test results of detectors.Methods Based on Monte Carlo simulation and experimental test results,the specific schematic design and assembling process of GRD were optimized.After being fully assembled,the GRDs were conducted performance tests by using radioactive source and also conducted random vibration tests.Result and conclusion The test results show that all satellite-borne GRDs have energy resolution<16%at 59.5 keV,meeting requirements of satellite in scientific performance.The random vibration test shows that GRD can maintain in a stable performance,which meets the requirement of spatial application.展开更多
Introduction The main physical objective of the GECAM satellite is to detect gamma-ray bursts,which is related to gravitational waves of double compact object mergers.The GECAM satellite also detects and investigates ...Introduction The main physical objective of the GECAM satellite is to detect gamma-ray bursts,which is related to gravitational waves of double compact object mergers.The GECAM satellite also detects and investigates various bursts of high-energy celestial bodies.Purposes and methods In this study,we designed,developed and calibrated the payload and launched it into orbit with GECAM satellite.The payload consists of the gamma ray detector(GRD,for detecting 4 keV–4 MeV X/γray),the charged particle detector(CPD,for detecting 150 keV–5 MeV charged particle),and the electronic box(EBOX).The all-sky field coverage is achieved via two 229-degree large-area satellites positioned 180 degrees apart and are on opposite sides of the geo-center.Each satellite is equipped with 25 GRDs and 8 CPDs;thus,the satellite can identify charged particle bursts in space.Gamma-ray detectors adopt lanthanum bromide crystal technology combined with silicon photomultipliers.This is the first time that this technology was used massively in space detectors.Conclusions The GECAM satellite can quickly determine the direction of gamma-ray bursts(positioning)via indexing and fitting method,while the transmit variability,energy spectrum and direction of the gamma-ray bursts guide subsequent observations through the Beidou-3 RDSS in quasi-real time.It will play an important role in the study of high energy celestial bursts.展开更多
Background The Gravitational wave highly energetic Electromagnetic Counterpart All-sky Monitor(GECAM)is dedicated to detecting gravitational wave gamma-ray bursts.It is capable of all-sky monitoring over and discoveri...Background The Gravitational wave highly energetic Electromagnetic Counterpart All-sky Monitor(GECAM)is dedicated to detecting gravitational wave gamma-ray bursts.It is capable of all-sky monitoring over and discovering gamma-ray bursts and new radiation phenomena.GECAM consists of two microsatellites,each equipped with 8 charged particle detectors(CPDs)and 25 gamma-ray detectors(GRDs).Purpose The CPD is used to measure charged particles in the space environment,monitor energy and flow intensity changes,and identify between gamma-ray bursts and space charged particle events in conjunction with GRD.Methods CPD uses plastic scintillator as the sensitive material for detection,silicon photomultiplier array as the optically readable device,and the inlaid Am-241 radioactive source as the onboard calibration means.Conclusion In this paper,we will present the working principle,physical design,functional implementation and preliminary performance test results of the CPD.As a result,the energy range of electron,gamma-ray detection efficiency and dead time are tested to be better than the indexes required through the ground calibration experiment.展开更多
Basalt discriminant diagrams have been used to identify the tectonic setting of basaltic magmatism since the 1970s and have played an important role in reconstructing paleotectonic environments.However,the significant...Basalt discriminant diagrams have been used to identify the tectonic setting of basaltic magmatism since the 1970s and have played an important role in reconstructing paleotectonic environments.However,the significant increase in the availability of geochemical data has led to a reassessment of these diagrams,suggesting that some of the tectonic settings indicated by these diagrams are not accurate.Here,we use a database of global ocean island basalt(OIB),mid-ocean ridge basalt(MORB),and island arc basalt(IAB)geochemistry to propose a series of new tectonic discriminant diagrams based on the ratios of large-ion lithophile elements(LILEs)to high field strength elements(HFSEs).These new diagrams indicate that the LILE can be used to differentiate OIB,MORB,and IAB samples,meaning that LILE/HFSE ratios can discriminate between these basalts that form in different tectonic settings.Our new diagrams can correctly assign samples to OIB,MORB,and IAB categories more than 85%of the time,with the discrimination between OIB and MORB having an accuracy of slightly less than 85%.展开更多
Background The Gravitational Wave High-energy Electromagnetic Counterpart All-sky Monitor(GECAM)consists of 2 microsatellites,each of which contains 25 GRD(LaBr3)detectors and 8 CPD(plastic scintillator)detectors.Meth...Background The Gravitational Wave High-energy Electromagnetic Counterpart All-sky Monitor(GECAM)consists of 2 microsatellites,each of which contains 25 GRD(LaBr3)detectors and 8 CPD(plastic scintillator)detectors.Method silicon photomultiplier(SiPM)array is used to read each detector.The output signal of these detectors with SiPM array is very special and challenging to readout.In this study,a novel data acquisition(DAQ)algorithm for these detectors is designed and implemented,and the content of the output event packet is defined.Result and Conclusion The performances,including the event acquisition efficiency of this DAQ algorithm,are extensively verified through experimental tests.From the on-ground and in-flight tests,this algorithm has excellent performance despite the very limited resources and short development time of GECAM mission.展开更多
The paper presents an explicit matrix algorithm to solve the problem of an elastic wedge with three loaded surfaces.The algorithm makes use of a recently published concept of transformation matrix,by which the origina...The paper presents an explicit matrix algorithm to solve the problem of an elastic wedge with three loaded surfaces.The algorithm makes use of a recently published concept of transformation matrix,by which the original surface loads are converted to equivalent loads in half-space.The three loaded edges are considered simultaneously.The developed algorithm is used to study the effects of two free edges of a steel block and tapered rollers with different contact angles.The two load-free edges can substantially increase deformation if the two edges are close in distance.The results of the tapered roller simulation show that deformation is considerably sensitive to the contact angle of the tapered roller.The largest deformation appears at the big end of the roller.Furthermore,empirical formulae for correction factors for the calculation of block or quarter-space deformation based on half-space solutions are summarized.展开更多
The development of wideband lasing media has deep implications for imaging,sensing,and display technologies.We show that a single chromophore can be engineered to feature wide-gamut fluorescence and lasing throughout ...The development of wideband lasing media has deep implications for imaging,sensing,and display technologies.We show that a single chromophore can be engineered to feature wide-gamut fluorescence and lasing throughout the entire visible spectrum and beyond.This exceptional color tuning demonstrates a chemically controlled paradigm for light emission applications with precise color management.Achieving such extensive color control requires a molecular blueprint that yields a high quantum efficiency and a high solubility in a wide variety of liquids and solids while featuring a heterocyclic structure with good steric access to the lone pair electrons.With these requirements in mind,we designed a lasing chromophore that encloses a lasing color space twice as large as the sRGB benchmark.This record degree of color tuning can in principle be adapted to the solid state by incorporating the chromophore into polymer films.By appropriately engineering the base molecular structure,the widest range of lasing wavelengths observed for a conventional gain medium can be achieved,in turn establishing a possible route toward highefficiency light emitters and lasers with near-perfect chromaticity.展开更多
A finite volume(FV)method for simulating 3D Fluid-Structure Interaction(FSI)is presented in this paper.The fluid flow is simulated using a parallel unstructured multigrid preconditioned implicit compressible solver,wh...A finite volume(FV)method for simulating 3D Fluid-Structure Interaction(FSI)is presented in this paper.The fluid flow is simulated using a parallel unstructured multigrid preconditioned implicit compressible solver,whist a 3D matrix-free implicit unstructured multigrid finite volume solver is employed for the structural dynamics.The two modules are then coupled using a so-called immersed membrane method(IMM).Large-Eddy Simulation(LES)is employed to predict turbulence.Results from several moving boundary and FSI problems are presented to validate proposed methods and demonstrate their efficiency。展开更多
Photo-induced processes in organic materials mostly occur on molecular levels. Excited molecules may split to form radicals, starting a polymerization process with diffusing monomers. The azo-dyes perform an optically...Photo-induced processes in organic materials mostly occur on molecular levels. Excited molecules may split to form radicals, starting a polymerization process with diffusing monomers. The azo-dyes perform an optically induced cis-trans isomerization. During pattern formation like a holographic grating, the local temperature increase, especially in thin films, is up to date a subject of estimation from absorption and dissipation data. However, the exact knowledge of the surface temperature would help a lot in understanding the resulting refractive index and thickness patterns during holographic exposure. In this paper, in-situ pyrometer measurements are presented. As examples, different photosensitive materials, varying from a photopolymer to polycrystalline azo dyes, are used in order to outline the magnitude of this effect and demonstrate the feasibility of this technique.展开更多
基金funded by NSFC(52204086,52474122)Guangdong Provincial Department of Science and Technology(2025B1515020067,2022A1515240009).
文摘This article investigates the mechanical responses and acoustic emission(AE)characteristics of sandstone under the triaxial differential cyclic loading(DCL)at different unloading rates of confining stress.The test results indicate that strength of rock specimens under different stress paths of triaxial unloading confining stress-differential cyclic loading(TUCS-DCL)can be fitted by the Mohr–Coulomb,Hoek–Brown,and Bieniawski criteria.The confining stress unloading rate can dominate the radial strain rate,while the axial DCL pattern has an unpronounced effect.The confining stress unloading rate affects the energy evolution in radial and axial directions of specimens,with the ratio of radially released energy to axially consumed energy fluctuating more significantly during the fast unloading of confining stress,the valley value of the ratio can serve as a precursor for failure.The confining stress unloading rate has no significant effect on stress–strain phase shift,while axial rapid-loading-slow-unloading can correspond to a larger magnitude of phase shift.AE signals begin to significantly increase after the confining stress is unloaded to zero,and a notable Kaiser effect is observed during cyclic loading preceding the failure.
基金the National Basic Research Program of China (Grant 2014CB046803)the National Natural Science Foundation of China (Grant 11772084).
文摘The pseudo-excitation method combined with the integral transform method (PEM-ITM) is presented to investigate the ground vibration of a coupled track-soil system induced by moving random loads. Commonly in the track model, the rail, sleepers, rail pads, and ballast are modelled as an infinite Euler beam, discretely distributed masses, discretely distributed vertical springs, and a viscoelastic layer, respectively. The soil is regarded as a homogenous isotropic half-space coupled with the track using the boundary condition at the surface of the ground. By introducing a pseudo-excitation, the random vibration analysis of the coupled system is converted into a harmonic analysis. The analytical form of evolutionary power spectral density responses of the simplified coupled track-soil system under a random moving load is derived in the frequency/wavenumber domain by PEM-ITM. In the numerical examples, the effects of different parameters, such as the moving speed, the soil properties, and the coherence of moving loads, on the ground response are investigated.
基金financially supported by the Guangdong Major Project of Basic and Applied Basic ResearchChina(No.2019B030302010)+8 种基金the Guangdong Basic and Applied Basic Research FoundationChina(Nos.2021A1515010756,2019B1515130005)the Natural Science Foundation of Jiangsu ProvinceChina(No.BK20180266)the National Natural Science Foundation of China(Nos.51471131,52071222,51822107,11972037,52001269,52101199,52001219)the FundamentalResearch Funds for the Central Universitiesthe National Key Research and Development Plan(No.2018YFA0703603)the Strategic Priority Research Program of Chinese Academy of Sciences with Grant No.XDB30000000the Tianshan Innovation Team Program of Xinjiang Uygur Autonomous Region(No.2020D14038)。
文摘The plastic deformation of amorphous alloys is well known to be localized into shear bands(SBs),which are believed to stem from the atomic-scale flow defects,i.e.,shear transformation zones(STZs).Yet,the bridge between the mesoscopic SBs and the atomic-scale STZs remains poorly understood.In this work,through thermally activating pronouncedβrelaxations in the well-designed crystalline-layer confined amorphous(CLCA)Ni W alloy films,we experimentally captured and observed an intermediate nanosized structure termed as“nano shear bands”(NSBs)with a typical size of 1–2 nm in thickness and5–10 nm in length.The influences of such NSB structures on the macroscale deformation behavior were systematically investigated.It was found that NSBs lead to both hardening and toughening effects for the CLCA films,as they promote multiple and controlled shear banding deformation,which results in enhanced crystallization.The intermediate NSB structure could connect the microstructural characteristics and macroscopic plasticity in amorphous alloys and may provide new insights for understanding the microscopic deformation mechanism of amorphous alloys as well as tuning/designing their properties.
基金This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA25050100)the National Natural Science Foundation of China(Grant Nos.11991074,11975154,12005287,and 12135009)+2 种基金the Science Challenge Project(Grant No.TZ2018005)X.F.Li was supported by the China and Germany Postdoctoral Exchange Program from the Office of the China Postdoctoral Council and the Helmholtz Centre(Grant No.20191016)and the China Postdoctoral Science Foundation(Grant No.2018M641993)Y.Zhao was also supported by Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515011695).Simulations were carried out on the JURECA and JUWELS supercomputers at the Jülich Supercomputing Centre,which are granted from the Projects JZAM04 and LAPIPE.
文摘Broadband lasers have been proposed as future drivers of inertial confined fusion(ICF)to enhance the laser-target coupling efficiency via the mitigation of various parametric instabilities.The physical mechanisms involved have been explored recently,but are not yet fully understood.Here,stimulated Raman scattering(SRS)as one of the key parametric instabilities is investigated theoretically and numerically for a broadband laser propagating in homogeneous plasma in multidimensional geometry.The linear SRS growth rate is derived as a function of scattering angles for two monochromatic laser beams with a fixed frequency differenceδω.Ifδω/ω_(0)∼1%,withω0 the laser frequency,these two laser beams may be decoupled in stimulating backward SRS while remaining coupled for sideward SRS at the laser intensities typical for ICF.Consequently,side-scattering may dominate over backward SRS for two-color laser light.This finding of SRS transition from backward to sideward SRS is then generalized for a broadband laser with a few-percent bandwidth.Particle-in-cell simulations demonstrate that with increasing laser bandwidth,the sideward SRS gradually becomes dominant over the backward SRS.Since sideward SRS is very efficient in producing harmful hot electrons,attention needs to be paid on this effect if ultra-broadband lasers are considered as next-generation ICF drivers.
基金funded by Open Fund of State Key Laboratory of Water Resource Protection and Utilization in Coal Mining(GJNY-20-113-03)Funds from NSFC(52204086)+2 种基金Funds from Joint National-Local Engineering Research Center for Safe and Precise Coal Mining(EC2021004)Funds from State Key Laboratory of Coal Resources in Western China(SKLCRKF20-07)Funds from Humboldt Research Fellowship.
文摘This work presents experimental tests based on coal collected from a coal mine based underground water reservoir(CMUWR).The mechanical responses of dry and water-soaked coal samples under the complex normal and shear stresses under multi-amplitude and variable frequency is investigated.The experimental results reveal the effects of stress path,water soaking and frequency on deformation,energy dissipation,secant modulus and shear failure surface roughness.The experimental results show that when normal and shear stresses are applied simultaneously,there is a significant competitive relationship between them.On the dominant side,the strain rate will be significantly increased.The sample under a loading frequency of 0.2 Hz exhibits a longer fatigue life.During the cyclic shear test,the shear strain of the water-soaked sample is higher than that of the dry samples.The average roughness coefficient of failure surface exhibits an increasing pattern with increase in shear strength,the elevated roughness of a shear surface is advantageous in constraining shear displacements of specimens,thereby lowering the energy dissipation.This study can provide theoretical and practical implications for a long-term safety evaluation of CMUWR.
基金support from the National Natural Science Foundation of China(NSFC,Grant Nos.41974197,41804162,and 42104158)supported by Central Plains Science and Technology Innovation Leading Talents of Henan Province under grant No.244200510012。
文摘It is generally believed that coronal mass ejections(CMEs)have magnetic flux rope structures because of their helical shapes.However,only about 30%–40%of interplanetary CMEs(ICMEs)have a local magnetic flux rope structure.The usual explanations are that the spacecraft only crossed the flank of the ropes and failed to detect the complete magnetic flux rope structure or that some processes destroyed these magnetic flux rope structures.Several studies suggest that some ICMEs inherently possess disordered magnetic fields and consequently exhibit no magnetic flux-rope structures.We introduce a special kind of ICME which has a low magnetic field magnitude and stable magnetic field direction,relatively fast expansion speed,and lower proton temperature and density.All three of the measured magnetic field components are relatively stable.We want to know whether these ICMEs also have magnetic flux rope structures or not.We identified 20 special ICMEs and analyzed their evolution based on their observed characteristics.We took a special ICME as an example,which had an apparent rope configuration at 1 au but evolved to a special ICME at 5.4 au,to illustrate that this kind of ICME could come from magnetic clouds(MCs)whose rope structure had been being stretched due to expansion.We inferred that the missing obvious flux rope structure may be due to the expansion of MCs,not the flank crossing effect.However,more than 50%of the events were associated with the dominant x-component of the magnetic field,which indicates a leg crossing.Therefore,the detection of part of these special ICMEs may also be the result of the leg-crossing effect.
文摘A hallmark of all forms of neurodegenerative diseases is impairment of neuronal functions,and in many cases neuronal cell death.Although the etiology of neurodegenerative diseases may be distinct,different diseases display a similar pathogenesis,for example abnormal immunity within the central nervous system(CNS),activation of macrophage/microglia and the involvement of proinflammatory cytokines.Recent studies show that neurons in a neurodegenerative state undergo a highly regulated programmed cell death,also called apoptosis.TNF-related apoptosis-inducing ligand(TRAIL),a member of the TNF family,has been shown to be involved in apoptosis during many diseases.As one member of a death ligand family,TRAIL was originally thought to target only tumor cells and was not present in CNS.However,recent data showed that TRAIL was unregulated in HIV-1-infected and immune-activated macrophages,a major disease inducing cell during HIV-1-assoeiated dementia(HAD).TRAIL is also induced on neuron by β-amyloid protein,an important pathogen for Alzheimer's disease.In this review,we summarize the possible common aspects that TRAIL involved those neurodegenerative diseases,TRAIL induced apoptosis signaling in the CNS cells,and specific role of TRAIL in individual diseases.Cellular & Molecular Immunology.2005;2(2):113-122.
基金This research was supported by the National Natural Science Foundation of China,Grant No.11775251the strategic leading science and technology program of Chinese Academy of Sciences(Grant No.XDA 15360100,XDA 15360102).
文摘Background Each GECAM satellite payload contains 25 gamma-ray detectors(GRDs),which can detect gamma-rays and particles and can roughly localize the Gamma-Ray Bursts(GRBs).GRD was designed using lanthanum bromide(LaBr3)crystal as the sensitive material with the rear end coupled with silicon photomultiplier(SiPM)array for readout.Purpose In aerospace engineering design of GRD,there are many key points to be studied.In this paper,we present the specific design scheme of GRD,the assembly and the performance test results of detectors.Methods Based on Monte Carlo simulation and experimental test results,the specific schematic design and assembling process of GRD were optimized.After being fully assembled,the GRDs were conducted performance tests by using radioactive source and also conducted random vibration tests.Result and conclusion The test results show that all satellite-borne GRDs have energy resolution<16%at 59.5 keV,meeting requirements of satellite in scientific performance.The random vibration test shows that GRD can maintain in a stable performance,which meets the requirement of spatial application.
基金This project is supported by National Natural Science Foundation of China(12173038)the strategic leading science and technology program(XDA 15360100,XDA 15360102)of the Chinese Academy of Sciences.
文摘Introduction The main physical objective of the GECAM satellite is to detect gamma-ray bursts,which is related to gravitational waves of double compact object mergers.The GECAM satellite also detects and investigates various bursts of high-energy celestial bodies.Purposes and methods In this study,we designed,developed and calibrated the payload and launched it into orbit with GECAM satellite.The payload consists of the gamma ray detector(GRD,for detecting 4 keV–4 MeV X/γray),the charged particle detector(CPD,for detecting 150 keV–5 MeV charged particle),and the electronic box(EBOX).The all-sky field coverage is achieved via two 229-degree large-area satellites positioned 180 degrees apart and are on opposite sides of the geo-center.Each satellite is equipped with 25 GRDs and 8 CPDs;thus,the satellite can identify charged particle bursts in space.Gamma-ray detectors adopt lanthanum bromide crystal technology combined with silicon photomultipliers.This is the first time that this technology was used massively in space detectors.Conclusions The GECAM satellite can quickly determine the direction of gamma-ray bursts(positioning)via indexing and fitting method,while the transmit variability,energy spectrum and direction of the gamma-ray bursts guide subsequent observations through the Beidou-3 RDSS in quasi-real time.It will play an important role in the study of high energy celestial bursts.
基金This research was supported by the“Strategic Priority Research Program”of the Chinese Academy of Sciences,Grant No.XDA 15360102.
文摘Background The Gravitational wave highly energetic Electromagnetic Counterpart All-sky Monitor(GECAM)is dedicated to detecting gravitational wave gamma-ray bursts.It is capable of all-sky monitoring over and discovering gamma-ray bursts and new radiation phenomena.GECAM consists of two microsatellites,each equipped with 8 charged particle detectors(CPDs)and 25 gamma-ray detectors(GRDs).Purpose The CPD is used to measure charged particles in the space environment,monitor energy and flow intensity changes,and identify between gamma-ray bursts and space charged particle events in conjunction with GRD.Methods CPD uses plastic scintillator as the sensitive material for detection,silicon photomultiplier array as the optically readable device,and the inlaid Am-241 radioactive source as the onboard calibration means.Conclusion In this paper,we will present the working principle,physical design,functional implementation and preliminary performance test results of the CPD.As a result,the energy range of electron,gamma-ray detection efficiency and dead time are tested to be better than the indexes required through the ground calibration experiment.
基金Technological Leading Talents Program of Yunnan Province[grant number 2013HA001]the National Natural Science Foundation of China[grant number 41502076]+1 种基金the State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences program[grant number 81300001]the China Geological Survey[grant number 12120114013701].
文摘Basalt discriminant diagrams have been used to identify the tectonic setting of basaltic magmatism since the 1970s and have played an important role in reconstructing paleotectonic environments.However,the significant increase in the availability of geochemical data has led to a reassessment of these diagrams,suggesting that some of the tectonic settings indicated by these diagrams are not accurate.Here,we use a database of global ocean island basalt(OIB),mid-ocean ridge basalt(MORB),and island arc basalt(IAB)geochemistry to propose a series of new tectonic discriminant diagrams based on the ratios of large-ion lithophile elements(LILEs)to high field strength elements(HFSEs).These new diagrams indicate that the LILE can be used to differentiate OIB,MORB,and IAB samples,meaning that LILE/HFSE ratios can discriminate between these basalts that form in different tectonic settings.Our new diagrams can correctly assign samples to OIB,MORB,and IAB categories more than 85%of the time,with the discrimination between OIB and MORB having an accuracy of slightly less than 85%.
基金The authors would like to thank all colleagues for helpful suggestions and comments.This study was supported by the National Natural Science Foundation of China(Grant No.11803039 and 12173038)the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(Grant No.XDA 15360100 and XDA 15360102).
文摘Background The Gravitational Wave High-energy Electromagnetic Counterpart All-sky Monitor(GECAM)consists of 2 microsatellites,each of which contains 25 GRD(LaBr3)detectors and 8 CPD(plastic scintillator)detectors.Method silicon photomultiplier(SiPM)array is used to read each detector.The output signal of these detectors with SiPM array is very special and challenging to readout.In this study,a novel data acquisition(DAQ)algorithm for these detectors is designed and implemented,and the content of the output event packet is defined.Result and Conclusion The performances,including the event acquisition efficiency of this DAQ algorithm,are extensively verified through experimental tests.From the on-ground and in-flight tests,this algorithm has excellent performance despite the very limited resources and short development time of GECAM mission.
基金the Research Grants Council of Hong Kong(Project No.CityU11213914).
文摘The paper presents an explicit matrix algorithm to solve the problem of an elastic wedge with three loaded surfaces.The algorithm makes use of a recently published concept of transformation matrix,by which the original surface loads are converted to equivalent loads in half-space.The three loaded edges are considered simultaneously.The developed algorithm is used to study the effects of two free edges of a steel block and tapered rollers with different contact angles.The two load-free edges can substantially increase deformation if the two edges are close in distance.The results of the tapered roller simulation show that deformation is considerably sensitive to the contact angle of the tapered roller.The largest deformation appears at the big end of the roller.Furthermore,empirical formulae for correction factors for the calculation of block or quarter-space deformation based on half-space solutions are summarized.
基金DFG(IRTG 2022)NSERC(CREATE grant 463990-2015)for financial support of the Alberta/Technische Universität München Graduate School for Functional Hybrid Materials(ATUMs).
文摘The development of wideband lasing media has deep implications for imaging,sensing,and display technologies.We show that a single chromophore can be engineered to feature wide-gamut fluorescence and lasing throughout the entire visible spectrum and beyond.This exceptional color tuning demonstrates a chemically controlled paradigm for light emission applications with precise color management.Achieving such extensive color control requires a molecular blueprint that yields a high quantum efficiency and a high solubility in a wide variety of liquids and solids while featuring a heterocyclic structure with good steric access to the lone pair electrons.With these requirements in mind,we designed a lasing chromophore that encloses a lasing color space twice as large as the sRGB benchmark.This record degree of color tuning can in principle be adapted to the solid state by incorporating the chromophore into polymer films.By appropriately engineering the base molecular structure,the widest range of lasing wavelengths observed for a conventional gain medium can be achieved,in turn establishing a possible route toward highefficiency light emitters and lasers with near-perfect chromaticity.
文摘A finite volume(FV)method for simulating 3D Fluid-Structure Interaction(FSI)is presented in this paper.The fluid flow is simulated using a parallel unstructured multigrid preconditioned implicit compressible solver,whist a 3D matrix-free implicit unstructured multigrid finite volume solver is employed for the structural dynamics.The two modules are then coupled using a so-called immersed membrane method(IMM).Large-Eddy Simulation(LES)is employed to predict turbulence.Results from several moving boundary and FSI problems are presented to validate proposed methods and demonstrate their efficiency。
文摘Photo-induced processes in organic materials mostly occur on molecular levels. Excited molecules may split to form radicals, starting a polymerization process with diffusing monomers. The azo-dyes perform an optically induced cis-trans isomerization. During pattern formation like a holographic grating, the local temperature increase, especially in thin films, is up to date a subject of estimation from absorption and dissipation data. However, the exact knowledge of the surface temperature would help a lot in understanding the resulting refractive index and thickness patterns during holographic exposure. In this paper, in-situ pyrometer measurements are presented. As examples, different photosensitive materials, varying from a photopolymer to polycrystalline azo dyes, are used in order to outline the magnitude of this effect and demonstrate the feasibility of this technique.
