VUV imaging of type-ⅠELM filamentary structures and their temporal characteristics on EAST

In the H-mode experiments conducted on the Experimental Advanced Superconducting Tokamak(EAST),fluctuations induced by the so-called edge localized modes(ELMs)are captured by a high-speed vacuum ultraviolet(VUV)imaging system.Clear field line-aligned filamentary structures are analyzed in this work.Ion transport induced by ELM filaments in the scrape-off layer(SOL)under different discharge conditions is analyzed by comparing the VUV signals with the divertor probe signals.It is found that convective transport along open field lines towards the divertor target dominates the parallel ion particle transport mechanism during ELMs.The toroidal mode number of the filamentary structure derived from the VUV images increases with the electron density pedestal height.The analysis of the toroidal distribution characteristics during ELM bursts reveals toroidal asymmetry.The influence of resonance magnetic perturbation(RMP)on the ELM size is also analyzed using VUV imaging data.When the phase difference of the coil changes periodically,the widths of the filaments change as well.Additionally,the temporal evolution of the ELMs on the VUV signals provides rise time and decay time for each single ELM event,and the results indicate a negative correlation trend between these two times.

The effect of Ti and Zr content on the structure,mechanics and energy-release characteristics of Ti—Zr—Ta alloys

Energetic structural materials(ESMs)are a new type of structural materials with bearing and damage characteristics.In this work the microstructure,mechanical properties and energy release characteristics of multi-element Ti-Zr-Ta alloys with good casting performance were studied.The microstructure of the Ti_(x)ZrTa alloys gradually change from BCC+HCP to single BCC structure with the increase of Ti.While the Ti_(2)Zr_(y)Ta alloys was still uniform and single BCC structure with the increase of Zr.The evolution of microstructure and composition then greatly affect the mechanical properties and energy-release characteristics of Ti-Zr-Ta alloys.The synergistic effect of dual phase structure increases the fracture strain of Ti_(x)ZrTa(x=0.2,0.5)with the Ti content decreases,while the fracture strain of Ti_(x)ZrTa(x=2.0,3.0,4.0)gradually increase with the Ti content increases caused by the annihilation of the obstacles for dislocation movement.And as Zr content increases,the fracture strain of Ti_(2)Zr_(y)Ta alloys decrease,then the oxidation reaction rate and fragmentation degree gradually increase.The higher oxidation rate and the lager exposed oxidation area jointly leads the higher releasing energy efficiency of Ti_(x)ZrTa alloys with low Ti content and Ti_(2)Zr_(y)Ta alloys with high Zr content.

Effect of cyclic hydraulic stimulation on pore structure and methane sorption characteristics of anthracite coal: A case study in the Qinshui Basin, China

The cyclic hydraulic stimulation(CHS) has proven as a prospective technology for enhancing the permeability of unconventional formations such as coalbeds. However, the effects of CHS on the microstructure and gas sorption behavior of coal remain unclear. In this study, laboratory tests including the nuclear magnetic resonance(NMR), low-temperature nitrogen sorption(LTNS), and methane sorption isotherm measurement were conducted to explore changes in the pore structure and methane sorption characteristics caused by CHS on an anthracite coal from Qinshui Basin, China. The NMR and LTNS tests show that after CHS treatment, meso- and macro-pores tend to be enlarged, whereas micropores with larger sizes and transition-pores may be converted into smaller-sized micro-pores. After the coal samples treated with 1, 3, 5 and 7 hydraulic stimulation cycles, the total specific surface area(TSSA)decreased from 0.636 to 0.538, 0.516, 0.505, and 0.491 m^(2)/g, respectively. Fractal analysis based on the NMR and LTNS results show that the surface fractal dimensions increase with the increase in the number of hydraulic stimulation cycles, while the volume fractal dimensions exhibit an opposite trend to the surface fractal dimensions, indicating that the pore surface roughness and pore structure connectivity are both increased after CHS treatment. Methane sorption isothermal measurements show that both the Langmuir volume and Langmuir pressure decrease significantly with the increase in the number of hydraulic stimulation cycles. The Langmuir volume and the Langmuir pressure decrease from 33.47 cm^(3)/g and 0.205 MPa to 24.18 cm^(3)/g and 0.176 MPa after the coal samples treated with 7 hydraulic stimulation cycles, respectively. The increments of Langmuir volume and Langmuir pressure are positively correlated with the increment of TSSA and negatively correlated with the increments of surface fractal dimensions.

Experimental study of the effects of a multistage pore-throat structure on the seepage characteristics of sandstones in the Beibuwan Basin:Insights into the flooding mode

To investigate the relationship between grain sizes, seepage capacity, and oil-displacement efficiency in the Liushagang Formation of the Beibuwan Basin, this study identifies the multistage pore-throat structure as a crucial factor through a comparison of oil displacement in microscopic pore-throat experiments. The two-phase flow evaluation method based on the Li-Horne model is utilized to effectively characterize and quantify the seepage characteristics of different reservoirs, closely relating them to the distribution of microscopic pores and throats. It is observed that conglomerate sandstones at different stages exhibit significant heterogeneity and noticeable differences in seepage capacity, highlighting the crucial role played by certain large pore throats in determining seepage capacity and oil displacement efficiency. Furthermore, it was found that the displacement effects of conglomeratic sandstones with strong heterogeneity were inferior to those of conventional homogeneous sandstone, as evidenced by multiple displacement experiments conducted on core samples with varying granularities and flooding systems. Subsequently, core-based experiments on associated gas flooding after water flooding were conducted to address the challenge of achieving satisfactory results in a single displacement mode for reservoirs with significant heterogeneity. The results indicate that the oil recovery rates for associated gas flooding after water flooding increased by 7.3%-16.4% compared with water flooding alone at a gas-oil ratio of approximately 7000 m^(3)/m^(3). Therefore, considering the advantages of gas flooding in terms of seepage capacity, oil exchange ratio, and the potential for two-phase production, gas flooding is recommended as an energy supplement mode for homogeneous reservoirs in the presence of sufficient gas source and appropriate tectonic angle. On the other hand, associated gas flooding after water flooding is suggested to achieve a more favorable development effect compared to a single mode of energy supplementation for strongly heterogeneous sandstone reservoirs.

Experimental Investigation of the Hydrodynamic Characteristics of A Modular Floating Structure System Integrated with WEC-Type Floating Artificial Reefs

Integrating wave energy converters(WECs)with offshore platforms offers numerous advantages,such as reducing wave loads,supplying energy to the platform,and cost-sharing in construction.This paper reports an experimental investigation focusing on the hydrodynamic characteristics of a proposed modular floating structure system integrated with WEC-type floating artificial reefs.The proposed system comprises several serially arranged hexagonal floating structures,anchored by tension legs,and integrated with outermost WEC-type floating artificial reefs.A simplified wave energy converter utilizing the relative pitch motion between adjacent modules for energy conversion was constructed in the scale model test.The effects of chain-type modular expansion on the multi-body motion response,mooring tension response,and WEC performance of the system have been thoroughly investigated.The experimental results indicate that increasing the number of hexagonal modules can notably reduce the system’s surge response,particularly under survival sea conditions.The connection of the outermost reef modules slightly increases the tension leg load of the adjacent module,whereas the tension leg load remains relatively consistent across the inner hexagonal modules.Furthermore,through a comparison of the dynamic responses of the hexagonal module connected and unconnected outermost reefs,the good performance in terms of energy conversion and wave attenuation of the WECtype floating artificial reef modules was effectively validated.The main results from this work can provide useful references for engineering applications involving modular floating structures integrated with WECs.

Numerical simulation of inlet placement on sewage characteristics in the rounded square aquaculture tank with single inlet

To improve the self-cleaning ability of aquaculture tank and the efficiency of circulating water,physical and numerical experiments were conducted on the influence of inlet structure on sewage discharge in a rounded square aquaculture tank with a single inlet.Based on the physical model of the tank,analysis of how inlet structure adjustment affects sewage discharge efficiency and flow field characteristics was conducted to provide suitable flow field conditions for sinkable solid particle discharge.In addition,an internal flow field simulation was conducted using the RNG k-εturbulence model in hydraulic drive mode.Then a solid-fluid multiphase model was created to investigate how the inlet structure affects sewage collection in the rounded square aquaculture tank with single inlet and outlet.The finding revealed that the impact of inlet structure is considerably affecting sewage collection.The conditions of C/B=0.07-0.11(the ratio of horizontal distance between the center of the inlet pipe and the tank wall(C)to length of the tank(B))andα=25°(αis the angle between the direction of the jet and the tangential direction of the arc angle)resulted in optimal sewage collection,which is similar to the flow field experiment in the rounded square aquaculture tank with single inlet and outlet.An excellent correlation was revealed between sewage collection and fluid circulation stability in the aquaculture tank.The present study provided a reference for design and optimization of circulating aquaculture tanks in aquaculture industry.

Research on the Course of Principles of Concrete Structure Design

Nowadays,education and teaching have become a hot topic,and teaching in colleges and universities is facing a brand-new development direction.Principles of Concrete Structure Design,as one of the main courses,transmits professional knowledge for students,enhances the students’professional ability,and further carries out in-depth research on the course to bring a better teaching effect for students.The article mainly focuses on the research of the principles of concrete structure design course,conducts an analysis of the teaching characteristics of the principles of concrete structure design course,and reasonably sets the teaching content from the optimization of the course teaching objectives;innovative course teaching methods can deepen the effect of knowledge understanding;reform of experimental practice teaching can lay down the effect of the internalization of knowledge,etc.The in-depth description and discussion of the relevant aspects of the research aim to provide guidelines for related research.

Sintering characteristics of fluxes and their structure optimization

Sintering characteristics of common fluxes and sintering blending ores, such as mineralization capacity, liquid generation capacity, consolidation strength, were examined to master the behavior and effect of fluxes in sintering. Based on fundamental studies, sinter pot tests were carried out to obtain the principles of optimizing the sinter flux structure. The results showed that strong mineralization capacity, liquid phase generation capacity, and consolidation strength were obtained as sintering blending ores combined with the calcareous flux, while rela-tively poor sintering characteristics were obtained as sintering blending ores combined with the magnesian flux. High reactive quicklime should be used as much as possible in the sintering mixture. It reached better sintering results while quicklime was used instead of limestone and its appropriate proportion in the sintering mixture was around 4wt%. On the premise of ensuring the MgO content, the dolomite amount should be decreased, and the substitution of quicklime for dolomite caused better sintering results. The granularity of serpentine should be re-fined with a proper size smaller than 2 mm. The application of the divided addition method brought the best sintering performance with 30wt% of quicklime and 70wt% of fuel.

Seasonal characteristics and formation mechanism of the thermohaline structure of mesoscale eddy in the South China Sea

The seasonal characteristics and formation mechanism of the thermohaline structure of mesoscale eddy in the South China Sea are investigated using the latest eddy dataset and ARMOR3D data. Eddy-centric composites reveal that the horizontal distribution of temperature anomaly associated with eddy in winter is more of a dipole pattern in upper 50 m and tends to be centrosymmetric below 50 m, while in summer the distribution pattern is centrosymmetric in the entire water column. The horizontal distribution of eddy-induced salinity anomaly exhibits similar seasonal characteristics, except that the asymmetry of the salinity anomaly is weaker. The vertical distribution of temperature anomaly associated with eddy shows a monolayer structure, while the salinity anomaly demonstrates a triple-layer structure. Further analysis indicates that the vertical distribution of the anomalies is related to the vertical structure of background temperature and salinity fields, and the asymmetry of the anomalies in upper 50 m is mainly caused by the horizontal advection of background temperature and salinity.

Effects of material of metallic frame on the penetration resistances of ceramic-metal hybrid structures

The effects of metallic material on the penetration resistances of ceramic-metal hybrid structures against vertical long-rod tungsten projectiles were studied by artillery-launched experiments and numerical simulation.Hybrid structures with rectangular cores in transverse orthogonal arrangement and slidefitting ceramic inserts of zirconia toughened alumina prisms were fabricated with titanium alloy TC4(Ti6 Al4 V),AISI 4340 steel and 7075 aluminum alloy panels,respectively.The results showed that the hybrid structure of Ti6A14V exhibited the highest penetration resistance,followed by that of 7075 aluminum alloy with the same area density.The penetration resistance of the hybrid structure of AISI4340 steel was the lowest.The underlying mechanisms showed that the metallic material of a ceramicmetal hybrid structure can directly affect its energy absorption from the impact projectile,which further affects its penetration resistance.Different metallic frames exhibited different failure characteristics,resulting in different constraint conditions or support conditions for ceramic prisms.The high penetration resistance of the Ti6Al4V hybrid structure was due to its stronger back support to ceramic prisms as compared with that of AISI 4340 steel hybrid structure,and better constraint condition for ceramic prisms by metallic webs as compared with that of 7075 aluminum alloy hybrid structure.The results of mass efficiency and thickness efficiency showed that the Ti6Al4V hybrid structure has advantages in reducing both the thickness and the mass of protective structure.In addition,because the ceramic-metal hybrid structures in the present work were heterogeneous,impact position has slight influence on their penetration resistances.

Different characteristics of the structure of atmospheric boundary layer between dry and rainy periods over the northern Tibetan Plateau

In this paper, based on in-situ observational data of the Coordinated Enhanced Observing Period （CEOP） Asia-Australia Monsoon Project （CAMP） on the Tibetan＇Plateau （CAMP-Tibet）, structure of the Atmospheric Boundary Layer （ABL） was preliminarily studied during the dry and rainy seasons. The main results show： （a） Diurnal variation of the ABL is obvious over the northern Tibetan Plateau area. The height of the ABL is different with the season change, which ranges from 2,211 m to 4,430 m during the pre-monsoon season and from 1,006 m to 2,212 m during the monsoon season. The ABL height is higher during the dry period than during the rainyigeriod. （b） The humidity is lower during the dry period than during the rainy period, and there are reverse humidity during both periods. （c） Horizontal wind direction is mostly west during the dry period, east under the height of 2,500 m and west above the height of 2,500 m during the rainy period. The wind speed is low during both the rainy and dry periods in the lower ABL layer. The wind speed is stronger within the upper ABL during the dry period than dtn-ing the rainy period.

Study of the seismic response of a recycled aggregate concrete frame structure

Based on six-degree-of-freedom three-dimensional shaking table tests, the seismic response of a recycled aggregate concrete （RAC） frame was obtained. The analysis results indicate that the maximum story shear force and overturning moment reduce proportionally along the height of the model under the same earthquake wave. The story shear force, base shear coefficient and overturning moment of the structure increase progressively as the acceleration amplitude increases. The base shear coefficient is primarily controlled by the peak ground acceleration （PGA）. The relationships between the PGA and the shear coefficient as well as between the PGA and the dynamic amplification factor are obtained by mathematical fitting. The dynamic amplification factor decreases rapidly at the elastic-plastic stage, but decreases slowly with the development of the elastic-plasticity stage. The results show that the RAC frame structure has reasonable deformability when compared with natural aggregate concrete frame structures. The maximum inter-story drift ratios of the RAC frame model under frequent and rare intensity 8 test phases are 1/266 and 1/29, respectively, which are larger than the allowable value of 1/500 and 1/50 according to Chinese seismic design requirements. Nevertheless, the RAC frame structure does not collapse under base excitations with PGAs from 0.066 g up to 1.170 g.

Near-surface structure and energy characteristics of the Antarctic Circumpolar Current

Historical surface drifter observations collected from the Southern Ocean are used to study the near-surface structure, variability, and energy characteristics of the Antarctic Circumpolar Current （ACC）. A strong, nearly zonal ACC combined with complex fronts dominates the circulation system in the Southern Ocean. Standard variance ellipses indicate that both the Agulhas Return Current and the East Australian Warm Current are stable supplements of the near-surface ACC, and that the anticyclonic gyre formed by the Brazil warm current and the Malvinas cold current is stable throughout the year. During austral winter, the current velocity increases because of the enhanced westerly wind. Aroused by the meridional motion of the ACC, the meridional velocity shows greater instability characteristics than the zonal velocity does over the core current. Additionally, the ACC exhibits an eastward declining trend in the core current velocity from southern Africa. The characteristics of the ACC are also argued from the perspective of energy. The energy distribution suggests that the mean kinetic energy （MKE）, eddy kinetic energy （EKE）, and are strong over the core currents of the ACC. However, in contrast, EKE/MKE suggests there is much less （more） eddy dissipation in regions with strong （weak） energy distribution. Both meridional and zonal energy variations are studied to illustrate additional details of the ACC energy characteristics. Generally, all the energy forms except EKE/MKE present west-east reducing trends, which coincide with the velocity statistics. Eddy dissipation has a much greater effect on MKE in the northern part of the Southern Ocean.

Concurrent multi-scale design optimization of composite frame structures using the Heaviside penalization of discrete material model

This paper deals with the concurrent multi-scale optimization design of frame structure composed of glass or carbon fiber reinforced polymer laminates. In the composite frame structure, the fiber winding angle at the micro-material scale and the geometrical parameter of components of the frame in the macro-structural scale are introduced as the independent variables on the two geometrical scales. Considering manufacturing requirements, discrete fiber winding angles are specified for the micro design variable. The improved Heaviside penalization discrete material optimization interpolation scheme has been applied to achieve the discrete optimization design of the fiber winding angle. An optimization model based on the minimum structural compliance and the specified fiber material volume constraint has been established. The sensitivity information about the two geometrical scales design variables are also deduced considering the characteristics of discrete fiber winding angles. The optimization results of the fiber winding angle or the macro structural topology on the two single geometrical scales, together with the concurrent two-scale optimization, is separately studied and compared in the paper. Numerical examples in the paper show that the concurrent multi-scale optimization can further explore the coupling effect between the macro-structure and micro-material of the composite to achieve an ultralight design of the composite frame structure. The novel two geometrical scales optimization model provides a new opportunity for the design of composite structure in aerospace and other industries.

Effect of cermet substrate characteristics on the microstructure and properties of TiAlN coatings

The composition and structure of substrate materials have important influences on coating performance,especially in terms of bond-ing strength and coating hardness,which determine whether the coating can be used for a given application.In this study,a TiAlN coating is deposited on Ti(C,N)-based cermet(TC)substrates with 0wt%-20wt%WC by arc ion plating.The influence of cermet substrate characterist-ics on the structure and properties of the TiAlN coating is then researched.Results show that the TiAlN coating deposited on the TC substrate has a columnar grain structure.As WC increases,the strength ratio of I(111)/I(200)and adhesive strength of TiAlN gradually increases.In the ab-sence of WC in the substrate,the preferred orientation of the TiAlN coating is(200).As WC increases,the preferred orientation of the TiAlN coating becomes(111)and(200).Notable differences in adhesive strength between the coating and substrate could be attributed to the micro-structure and composition of the latter.Scratching results show that the adhesive strengths of the TiAlN coating on the 0wt%-20wt%WC cer-met substrate are 52-65 N.Among the coatings obtained that on the TC substrate with 15wt%WC presents the highest H/E and H3/E2,which indicates that this coating also features the best wear resistance.The failure mechanisms of the coated tools include coating peeling,adhesive wear,and abrasive wear.As the cutting speed increases,the degree of flank wear increases and the durability of the coating decreases accord-ingly.Increases in WC result in an initial decrease followed by a gradual increase in the flank wear of the coated cermet inserts.

In-situ experimental investigation of the influence of structure characteristics on subway-induced building vibrations

Many types of buildings have been widely constructed in the vicinity of subway lines in China.Normal life and business activities are hampered by excessive subway-induced vibrations.This study aims to determine the influence of structure characteristics on structure-borne vibrations,generally based on experimental results.Vibration measurements were performed in four typical sites in Wuxi,China,involving over-track buildings,along-track buildings,frame structure buildings and a masonry building.Special structure designs like structure transfer floor were also included.Then,the captured data was analyzed in the time domain and the frequency domain.Furthermore,the influence of building location,structure type and structure layout was investigated.Finally,vibrations were evaluated with ISO and Chinese criteria and structure optimization for vibration attenuation was proposed.It is found that over-track buildings are more severely affected than along-track buildings.Higher frequency contents(20‒60 Hz)in over-track buildings and lower frequency contents(0‒10 Hz)in along-track buildings should be seriously considered in vibration control.Weaker structure member joints and lower material strength would be beneficial to over-track buildings while the inverse situation would be beneficial to along-track buildings.The application of structure transfer floor‒generally stiffer structure members and structure discontinuity‒is also beneficial.

The Characteristics of Ore-Controlling Structure in Baoshan Cu-Pb-Zn Polymetallic Deposit,Hunan Province

The Baoshan Cu-Pb-Zn polymetallic deposit is lied in the central Nanling mineralization zone,and belongs to the junction area of the Chenzhou-Linwu fault zone and the Leiyang-Linwu fault zone.It is a significant part of Nanling polymetallic deposit belt.The outcropping stratas consist of upper Devonian Shetianqiao,Xikuangshan Formation,Lower Carboniferous Menggong’ao,Shidengzi,Ceshui,and Zimenqiao Formation.Igneous rocks in the Baoshan ore area mainly comprise granodiorite porphyry.Furthermore,the radio isotopic age ranges from 123 Ma to 183 Ma,belonging to the early to middle Yanshanian.

Investigation on thermal characteristics and desensitization mechanism of improved step ladder-structured nitrocellulose

Nitrocellulose,or cellulose nitrate,has received considerable interest due to its various applications,such as propellants,coating agents and gas generators.However,its high mechanical sensitivity caused many accidents during its storage and usage in ammunition.In this work,two kinds of insensitive step ladderstructured nitrocellulose(LNC)with different nitrogen contents were synthesized.The products were characterized by FT-IR,Raman,XRD,SEM,elemental analysis,TGA,DSC,accelerating rate calorimeter analysis(ARC),and drop weight test to study their molecular structure,thermal characteristics and desensitization performance.Compared with raw nitrocellulose,LNC has a sharper exothermic peak in the DSC and ARC curves.The H50values of the two kinds of LNC increased from 25.76 to 30.01 cm for low nitrogen content and from 18.02 to 21.84 cm for high nitrogen content,respectively.The results show that the ladder-structure of LNC which provides regular molecular arrangement and a soft buffer made with polyethylene glycol could affect the energy releasing process of LNC and reduce the sensitivity of LNC.Insensitive LNC provides an alternative to be used as a binder in insensitive propellants formulation.

Failure characteristics and the damage evolution of a composite bearing structure in pillar-side cemented paste backfilling

A backfilling body-coal pillar-backfilling body(BPB)structure formed by pillar-side cemented paste backfilling can bear overburden stress and ensure safe mining.However,the failure response of BPB composite samples must be investigated.This paper examines the deformation characteristics and damage evolution of six types of BPB composite samples using a digital speckle correlation method under uniaxial compression conditions.A new damage evolution equation was established on the basis of the input strain energy and dissipated strain energy at the peak stress.The prevention and control mechanisms of the backfilling body on the coal pillar instability were discussed.The results show that the deformation localization and macroscopic cracks of the BPB composite samples first appeared at the coal-backfilling interface,and then expanded to the backfilling elements,ultimately appearing in the coal elements.The elastic strain energy in the BPB composite samples reached a maximum at the peak stress,whereas the dissipated energy continued to accumulate and increase.The damage evolution curve and equation agree well with the test results,providing further understanding of instability prevention and the control mechanisms of the BPB composite samples.The restraining effect on the coal pillar was gradually reduced with decreasing backfilling body element's volume ratio,and the BPB composite structure became more vulnerable to failure.This research is expected to guide the design,stability monitoring,instability prevention,and control of BPB structures in pillar-side cemented paste backfilling mining.

The Influence of Various Structure Surface Boundary Conditions on Pressure Characteristics of Underwater Explosion

The shock wave of the underwater explosion can cause severe damage to the ship structure.The propagation characteristics of shock waves near the structure surface are complex,involving lots of complex phenomena such as reflection,transmission,diffraction,and cavitation.However,different structure surface boundaries have a significant effect on the propagation characteristics of pressure.This paper focuses on investigating the behavior of shock wave propagation and cavitation from underwater explosions near various structure surfaces.A coupled Runge–Kutta discontinuous Galerkin(RKDG)and finite elementmethod(FEM)is utilized to solve the problem of the complex waves of fluids and structure dynamic response,considering the fluid compressibility.The level set(LS)method and the ghost fluid(GF)method are combined to capture the moving interface and deal with the stability of the coupling between the shock wave and structure surface.Besides,a cut-off cavitation model is introduced to the RKDG method.The validation of the numerical calculation model is discussed by comparing it with the known solution to verify the numerical solutions.Then,crucial kinds of structure surface boundary conditions include shallow-water single layer elasticity plate,double-layer crevasse elasticity plate,single layer curved elasticity plate,and double-layer curved elasticity plates are analyzed and discussed.The results and analysis can provide references for underwater explosion pressure characteristics,the impacting response of different boundary structures,and designing structures.