The reaction of carbon-free oxide-based(corundum,spinel,zirconia,and mullite)submerged entry nozzle(SEN)lining with rare earth inclusions and its anti-clogging effects under near working conditions were systematically...The reaction of carbon-free oxide-based(corundum,spinel,zirconia,and mullite)submerged entry nozzle(SEN)lining with rare earth inclusions and its anti-clogging effects under near working conditions were systematically studied.A variety of lining composite test methods were innovatively used to ensure the consistency of test conditions.The experimental results showed that the mullite(acidic oxide)has strong reactivity with rare earth inclusions,and the spinel(basic oxide)has stable chemical properties and weak reactivity with rare earth inclusions.Because alumina is one of the main reactants of clogging formation,corundum is not suitable for SEN lining.There are less clogs on the surface of zirconia,but it will be exsoluted and unstable.Therefore,solving the problem of zirconia exsolution will greatly strengthen its application in SEN lining.展开更多
The finite volume method was applied to numerically simulate the bottom pressure field induced by regular waves,vehicles in calm water and vehicles in regular waves.The solution of Navier-Stokes(N-S)equations in the v...The finite volume method was applied to numerically simulate the bottom pressure field induced by regular waves,vehicles in calm water and vehicles in regular waves.The solution of Navier-Stokes(N-S)equations in the vicinity of numerical wave tank's boundary was forced towards the wave theoretical solution by incorporating momentum source terms,thereby reducing adverse effects such as wave reflection.Simulations utilizing laminar flow,turbulent flow,and ideal fluid models were all found capable of effectively capturing the waveform and bottom pressure of regular waves,agreeing well with experimental data.In predicting the bottom pressure field of the submerged vehicle,turbulent simulations considering fluid viscosity and boundary layer development provided more accurate predictions for the stern region than inviscid simulations.Due to sphere's diffractive effect,the sphere's bottom pressure field in waves is not a linear superposition of the wave's and the sphere's bottom pressure field.However,a slender submerged vehicle exhibits a weaker diffractive effect on waves,thus the submerged vehicle's bottom pressure field in waves can be approximated as a linear superposition of the wave's and the submerged vehicle's bottom pressure field,which simplifies computation and analysis.展开更多
Rice varieties tolerant to submergence regulate shoot elongation during short-term submergence by expressing the SUB1A gene.In contrast,the deep-rooted DRO1 is effectively expressed under drought conditions to enhance...Rice varieties tolerant to submergence regulate shoot elongation during short-term submergence by expressing the SUB1A gene.In contrast,the deep-rooted DRO1 is effectively expressed under drought conditions to enhance water and nutrient uptake.This study investigates the growth and yield of rice with both SUB1A and DRO1 in the background of IR64,under early-season flooding,and mid-season drought.The study used a randomized complete design with two factors:soil moisture treatments(submergence,drought,and their combination)and genotypes.The genotypes included IR64,and three near-isogenic lines(NILs):NIL-SUB1DRO1,NIL-SUB1,and NIL-DRO1.Complete submergence was imposed for 7 days on 14-day-old seedlings,while drought was imposed on control and submerged plants following a 21-day recovery period from submergence,using 42-day-old plants.Variables were measured before and after treatments(submergence and drought),and at harvest or grain maturity.The stresses negatively affected the genotypes.At harvest,IR64 and NIL-SUB1DRO1 under both stresses showed a significant reduction in tiller numbers,shoot dry weights,and yields compared to their control plants.IR64 exhibited a significant delay in reaching flowering under all stresses.The rice introgression lines showed significant improvements in tolerance to the stresses.The study showed no negative consequences of combining drought and submergence tolerance in rice.展开更多
Under submerged conditions, compared with traditional self-excited oscillating pulsed waterjets(SOPWs), annular fluid-enhanced self-excited oscillating pulsed waterjets(AFESOPWs) exhibit a higher surge pressure throug...Under submerged conditions, compared with traditional self-excited oscillating pulsed waterjets(SOPWs), annular fluid-enhanced self-excited oscillating pulsed waterjets(AFESOPWs) exhibit a higher surge pressure through self-priming. However, their pressure frequency and cavitation characteristics remain unclear, resulting in an inability to fully utilize resonance and cavitation erosion to break coal and rock. In this study, high-frequency pressure testing, high-speed photography, and large eddy simulation(LES) are used to investigate the distribution of the pressure frequency band, evolution law of the cavitation cloud, and its regulation mechanism of a continuous waterjet, SOPW, and AFESOPW. The results indicated that the excitation of the plunger pump, shearing layer vortex, and bubble collapse corresponded to the three high-amplitude frequency bands of the waterjet pressure. AFESOPWs have an additional self-priming frequency that can produce a larger amplitude under a synergistic effect with the second high-amplitude frequency band. A better cavitation effect was produced after self-priming the annulus fluid, and the shedding frequency of the cavitation clouds of the three types of waterjets was linearly related to the cavitation number. The peak pressure of the waterjet and cavitation erosion effect can be improved by modulating the waterjet pressure oscillation frequency and cavitation shedding frequency.展开更多
Flooding can lead to oxygen deprivation in rapeseed,negatively affecting its growth and development and ul-timately reducing yields.Vitreoscilla hemoglobin(VHb),a bacterial hemoglobin with a high oxygen-binding affini...Flooding can lead to oxygen deprivation in rapeseed,negatively affecting its growth and development and ul-timately reducing yields.Vitreoscilla hemoglobin(VHb),a bacterial hemoglobin with a high oxygen-binding affinity,plays a key role in enhancing oxygen uptake and metabolic efficiency under low-oxygen conditions.Through genetic transformation,we overexpressed the VHb gene in rapeseed,which resulted in significant im-provements in survival rate,root length,and biomass under submerged conditions.Additionally,we observed that transgenic plants developed adventitious roots in response to submergence stress.These transgenic plants also exhibited increased activities of ethanol dehydrogenase and pyruvate decarboxylase-enzymes associated with anaerobic respiration.Our findings indicate that VHb enhances flooding tolerance in rapeseed by promoting adventitious root formation and strengthening the plant's capacity for fermentation metabolism under anaerobic conditions.展开更多
This study investigates the effects of radiation force due to the rotational pitch motion of a wave energy device,which comprises a coaxial bottom-mounted cylindrical caisson in a two-layer fluid,along with a submerge...This study investigates the effects of radiation force due to the rotational pitch motion of a wave energy device,which comprises a coaxial bottom-mounted cylindrical caisson in a two-layer fluid,along with a submerged cylindrical buoy.The system is modeled as a two-layer fluid with infinite horizontal extent and finite depth.The radiation problem is analyzed in the context of linear water waves.The fluid domain is divided into outer and inner zones,and mathematical solutions for the pitch radiating potential are derived for the corresponding boundary valve problem in these zones using the separation of variables approach.Using the matching eigenfunction expansion method,the unknown coefficients in the analytical expression of the radiation potentials are evaluated.The resulting radiation potential is then used to compute the added mass and damping coefficients.Several numerical results for the added mass and damping coefficients are investigated for numerous parameters,particularly the effects of the cylinder radius,the draft of the submerged cylinder,and the density proportion between the two fluid layers across different frequency ranges.The major findings are presented and discussed.展开更多
Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,...Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,including bubble,electromagnetic stirring,filtration separation,fluid flow,and sedimentation,often struggle with the removal of fine inclusions.Apart from these known methods,pulsed electric current(PEC),as an emerging technology,has demonstrated immense potential and environmental advantages.PEC offers adjustable current parameters and simple equipment,making it an attractive alternative to traditional methods.Its green energy-saving features and excellent results in regulating inclusion morphology and migration,as well as inhibiting submerged entry nozzle(SEN)clogging,make it a promising technology.In comparison to continuous current technology,PEC has shown significant advantages in regulating inclusions,not only improving purification efficiency but also demonstrating outstanding performance in flow stability and energy consumption.The ability of PEC to efficiently reduce inclusion numbers enhances the purity and quality of molten steel,improving its mechanical properties.Currently,the theoretical basis for controlling the movement of inclusions by current is mainly composed of three major theories:the double electric layer theory,electromagnetic force reverse separation theory,and electric free energy drive theory.These theories together form an important framework for researchers to understand and optimize the behavior of impurity movement controlled by electric current.Looking ahead,PEC is expected to pave the way for new solutions in directional regulation of inclusion migration,efficient inclusion removal,SEN clogging prevention,and the purification of molten steel.展开更多
Flooding in rice fields,especially in coastal regions and low-lying river basins,causes significant devastation to crops.Rice is highly susceptible to prolonged flooding,with a drastic decline in yields if inundation ...Flooding in rice fields,especially in coastal regions and low-lying river basins,causes significant devastation to crops.Rice is highly susceptible to prolonged flooding,with a drastic decline in yields if inundation persists for more than 7 d,especially during the reproductive stage.Although the SUB1 QTL,which confers tolerance to complete submergence during the vegetative stage,has been incorporated into breeding programs,the development of alternative sources is crucial.These alternatives would broaden the genetic base,mitigate the influence of the genomic background,and extend the efficacy of SUB1 QTL to withstand longer submergence periods(up to approximately 21 d).Contemporary breeding strategies predominantly target submergence stress at the vegetative stage.However,stagnant flooding(partial submergence of vegetative parts)during the reproductive phase inflicts severe damage on the rice crop,leading to reduced yields,heightened susceptibility to pests and diseases,lodging,and inferior grain quality.The ability to tolerate stagnant flooding can be ascribed to several adaptive traits:accelerated aerenchyma formation,efficient underwater photosynthesis,reduced radial oxygen loss in submerged tissues,reinforced culms,enhanced reactive oxygen species scavenging within cells,dehydration tolerance post-flooding,and resistance to pests and diseases.A thorough investigation of the genetics underlying these traits,coupled with the integration of key alleles into elite genetic backgrounds,can significantly enhance food and income security in flood-prone rice-growing regions,particularly in coastal high-rainfall areas and low-lying river basins.This review aims to delineate an innovative breeding strategy that employs genomic,phenomic,and traditional breeding methodologies to develop rice varieties resilient to various dimensions of flooding stress at both the vegetative and reproductive stages.展开更多
The electromagnetic swirling flow in nozzle(EMSFN)technique is designed to mitigate the adverse effects of unstable and uneven flow within the submerged entry nozzle in continuous casting.Utilizing electromagnetic for...The electromagnetic swirling flow in nozzle(EMSFN)technique is designed to mitigate the adverse effects of unstable and uneven flow within the submerged entry nozzle in continuous casting.Utilizing electromagnetic forces,EMSFN stabilizes the flow within the nozzle,leading to a more controlled flow in the mold.Numerical simulations were used to quantitatively analyze the magnetic and flow fields in a slab continuous casting system under EMSFN.Results indicate that EMSFN significantly stabilizes the outflow from the nozzle,with stability increasing with higher current intensity.At 10,000 Ampere-turns(At)of the coil,meniscus fluctuations were unstable.They stabilized at 13,000 At,with minimal changes observed beyond this point.The optimal current intensity for stable mold flow,at a casting speed of 1.56 m/min,is 13,000 At.These findings confirm the effectiveness of EMSFN in stabilizing the internal flow field of the slab mold and determining optimal operational current intensity.展开更多
The large molecular weight and high hydrophilicity of chloramphenicol(CAP) residuals in wastewater led to severe degradation difficulty,which propelled the development of new wastewater degradation processes and react...The large molecular weight and high hydrophilicity of chloramphenicol(CAP) residuals in wastewater led to severe degradation difficulty,which propelled the development of new wastewater degradation processes and reactors based on process intensification.This study enhanced the CAP degradation by ozone/peroxydisulfate(PDS) advanced oxidation process in a submerged rotating packed bed(SRPB)reactor.Compared the usage of different oxidants,it was indicated that the combination of O_(3) and PDS exhibited a higher degradation efficiency than ozone and PDS alone.The more desired degradation efficiency could be achieved at the operating conditions of ascending PDS concentration,SRPB rotational speed,ozone concentration,reduced initial CAP concentration,and the water qualities of ascended pH,lower Cl^(-)and initial CO_(3)^(2-) concentrations.Under the optimized conditions of C_(CAP)=20 mg·L^(-1),C_(O3)=30 mg·L^(-1),C_(PDS)=100 mg·L^(-1),and N=400 r·min^(-1),and water qualities of pH=10,the maximum chloramphenicol degradation efficiency of 97% and kinetic constant of 0.23 min^(-1) were achieved after treating 16 min.A comparison of the results with previously reported advanced oxidation processes of CAP indicated that the enhanced O^(3)/PDS advanced oxidation system using the SRPB can significantly improve the degradation efficiency of CAP.展开更多
Submerged Abrasive Waterjet Peening(SAWJP)shows great application potential in augmenting the fatigue properties of metallic parts.Thus,the present work aims to investigate the influence of SAWJP on the Surface Integr...Submerged Abrasive Waterjet Peening(SAWJP)shows great application potential in augmenting the fatigue properties of metallic parts.Thus,the present work aims to investigate the influence of SAWJP on the Surface Integrity(SI)and Fretting Fatigue(FF)properties of Inconel 718(IN718)superalloy and illustrate the microstructural evolution,FF life improvement,and fretting wear mechanism.First,the SI of the IN718 specimen was examined following treatment via SAWJP.Results showed that the specimen subjected to SAWJP formed a total plastic deformation layer of 56μm.The maximum microhardness and Compressive Residual Stress(CRS)measured across the depth of the SAWJP-treated specimens exhibited an increase in values ranging between 522 HV and 541 HV and 1171–1380 MPa,respectively.The FF test results of the specimen before and after SAWJP treatment at ambient temperatures indicated that the FF life of the SAWJP-treated specimen surpassed that of the as-received specimen by a factor of 2.81.The examination of the FF fracture,contact surface,and crack propagation behavior revealed the crucial factors contributing to the enhanced FF resistance of the IN718 specimen,including the gradient nanostructure characterized by ultra-refined grains,substantial CRS,and elevated microhardness,which were all induced by the SAWJP treatment.展开更多
Taking a C1x motor with a backward-facing step which can generate a typical corner vortex as a reference,a numerical methodology using large eddy simulation was established in this study.Based on this methodology,the ...Taking a C1x motor with a backward-facing step which can generate a typical corner vortex as a reference,a numerical methodology using large eddy simulation was established in this study.Based on this methodology,the position of the backward-facing step of the motor was computed and analyzed to determine a basic configuration.Two key geometrical parameters,the head cavity angle and submerged nozzle cavity height,were subsequently introduced.Their effects on the corner vortex motion and their interactions with the acoustic pressure downstream of the backward-facing step were analyzed.The phenomena of vortex acoustic coupling and characteristics of pressure oscillations were further explored.The results show that the maximum error between the simulations and experimental data on the dominant frequency of pressure oscillations is 5.23%,which indicates that the numerical methodology built in this study is highly accurate.When the step is located at less than 5/8 of the total length of the combustion chamber,vortex acoustic coupling occurs,which can increase the pressure oscillations in the motor.Both the vorticity and the scale of vortices in the downstream step increase when the head cavity angle is greater than 24°,which increases the amplitude of the pressure oscillation by maximum 63.0%.The submerged nozzle cavity mainly affects the vortices in the cavity itself rather than those in the downstream step.When the height of the cavity increases from 10 to 20 mm,the pressure oscillation amplitude under the main frequency increases by 39.1%.As this height continues to increase,the amplitude of pressure oscillations increases but the primary frequency decreases.展开更多
Cryogenic steels,i.e.,steels with maximum toughness at particularly low temperature,are increasingly becoming the focus of research.Cryogenic steels are usually alloyed with 5%–9%nickel.Ni can also be substituted by ...Cryogenic steels,i.e.,steels with maximum toughness at particularly low temperature,are increasingly becoming the focus of research.Cryogenic steels are usually alloyed with 5%–9%nickel.Ni can also be substituted by manganese as an austenite former.These high-manganese cryogenic grades are a cost-effective alternative to nickel-alloyed steels for use in liquefied natural gas storage tanks.The Mn content can then be more than 20 wt.%and lead to problems in production,particularly in the continuous casting process.In continuous casting of high-Mn-grades,quality issues and even breakout may result from the initial solidification behavior of the steel grades at high temperatures.Hot cracks form when a critical load is exceeded during solidification,close to the solidus temperature of the steel.A selected high-Mn-steel grade was characterized with respect to liquidus and solidus temperatures by means of thermal analysis and computational thermodynamics.In addition,so-called submerged split chill tensile tests were carried out to further understand the crack sensitivity of the solidifying shell for high-manganese cryogenic steels.The results reveal the presence of coarse hot tears,and also,a high frequency of hot cracks was observed at the location with the maximum accumulated strain,which is in line with the applied cracking criterion of Pierer and Bernhard for this investigation.In summary,the initial solidification phase of continuous casting poses a high risk of cracking for high-manganese cryogenic steel.展开更多
For a generalized radiation problem,an infinitely long submerged horizontal cylinder is forced to vibrate periodically in the transverse direction,with a described elastic harmonic motion along its longitudinal direct...For a generalized radiation problem,an infinitely long submerged horizontal cylinder is forced to vibrate periodically in the transverse direction,with a described elastic harmonic motion along its longitudinal direction.A critical frequency corresponds to the described wave number of elastic vibration,and the generalized hydrodynamic coefficients abruptly change in the vicinity of critical frequency.In this work,a numerical examination is carried out to study the characteristics of wave profiles and wave propagation in the vicinity of the critical frequency.Results show that below the critical frequency,the real parts of complex wave profiles have large values in the vicinity of the cylinder and decay to zero with the increasing distance from the cylinder.Meanwhile,the imaginary parts of complex wave profiles are all zero,which explains why the generalized radiation damping is zero when the vibration is less than the critical frequency.At far distances,no radiation wave is observed.When the vibration exceeds the critical frequency,the real and imaginary parts of the wave profiles oscillate harmonically and keep steady amplitudes.In addition,the generated radiation wave propagates obliquely outward.The influence of the cylinder’s submergence depth on the wave profile is also studied,and the results indicate that the amplitude of the wave profile decreases as the submergence depth of the cylinder increases.The 3D wave profiles are graphically presented to show the wave propagation characteristics in the vicinity of the critical frequency for this generalized radiation problem.This study provides a good reference for the interaction between fluid and slender elastic structures.展开更多
The paper is focused on the design of artificial sand beaches at sheltered and exposed sites.The methodology applied includes the study of the most essential design parameters and the application of numerical models t...The paper is focused on the design of artificial sand beaches at sheltered and exposed sites.The methodology applied includes the study of the most essential design parameters and the application of numerical models to compute the beach erosion and maintenance.The computed erosion volume decreases for coarser sand(0.5 mm sand instead of 0.3 mm).Beach erosion increases for more graded sand,but the effect is small(10%–15%).The slope of the artificial beach at sheltered sites is commonly between 1 to 15 and 1 to 30 in conditions with a micro tidal range and mild waves.Slopes between 1 to 30 and 1 to 50 are used for more open exposed sites.The effect of the upper and lower beach slope(1 to 15 or 1 to 20)on beach erosion is marginal for sand in the range of 0.3 to 0.5 mm.A break in slope is quickly adjusted by transport processes.The volume of beach sand required may be reduced by constructing a submerged sill at the toe of the beach.Analysis of costs shows that the construction costs including maintenance over a period of 50 years of a submerged sill are about the same as that of beach fill including maintenance.Hence,the beach fill volume can be twice as large for a solution without a sill.Beach erosion due to alongshore transport processes is minimum if the beach line of the planform is perpendicular to the main wave direction(equilibrium beach).展开更多
Various technologies and projects have been explored and developed for the synergetic control of environmental pollution and carbon emissions in aquatic ecosystems.Planting submerged vegetation in shallow waters was a...Various technologies and projects have been explored and developed for the synergetic control of environmental pollution and carbon emissions in aquatic ecosystems.Planting submerged vegetation in shallow waters was also expected to achieve this purpose.However,the magnitude and mechanism of carbon dioxide(CO_(2))emission affected by submerged vegetation is not clear enough in complex aquatic ecosystems.This study investigated the influences of submerged plants on CO_(2)emission,ecosystem metabolism features,and microbial community traits based on observations in river networks on the Changjiang River Delta.The results showed that CO_(2)emission from planted waters accounted for 73%of unplanted waters.Meanwhile,planted waters had higher dissolved organic carbon removal capacity in overlying water and higher potential of carbon sequestration in sediment at the same time.These distinctions between the two habitats were attributed to(1)improved CO_(2)and bicarbonate consumption in water columns via enhancing photosynthesis and(2)inhibited CO_(2)production by reconstructing the benthic microbial community.Additional eco-advantages were found in planted sediments,such as a high potential of methane oxidation and xenobiotics biodegradation and a low risk of becoming black and odorous.In brief,submerged vegetation is beneficial in promoting pollution removal and carbon retention synchronously.This study advances our understanding of the feedback between aquatic metabolism and CO_(2)emission.展开更多
A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impac...A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms.展开更多
Submerged vegetation commonly grows and plays a vital role in aquatic ecosystems,but it is also regarded as a barrier to the passing flow.Numerical simulations of flow through and over submerged vegetation were carrie...Submerged vegetation commonly grows and plays a vital role in aquatic ecosystems,but it is also regarded as a barrier to the passing flow.Numerical simulations of flow through and over submerged vegetation were carried out to investigate the effect of vegetation density on flow field.Numerical simulations were computationally set up to replicate flume experiments,in which vegetation was mimicked with flexible plastic strips.The fluid-structure interaction between flow and flexible vegetation was solved by coupling the two modules of the COMSOL packages.Two cases with different vegetation densities were simulated,and the results were successfully validated against the experimental data.The contours of the simulated time-averaged streamwise velocity and Reynolds stress were extracted to highlight the differences in mean and turbulent flow statistics.The turbulence intensity was found to be more sensitive to vegetation density than the time-averaged velocity.The developing length increased with the spacing between plants.The snapshots of the bending vegetation under instantaneous velocity and vorticity revealed that flexible vegetation responded to the effects of eddies in the shear layer by swaying periodically.The first two rows of vegetation suffered stronger approaching flow and were prone to more streamlined postures.In addition,the origin of tip vortices was investigated via the distribution of vorticity.The results reveal the variation of flow properties with bending submerged vegetation and provide useful reference for optimizationofrestorationprojects.展开更多
The ammonium exceedance discharge from sewage treatment plants has a great risk to the stable operation of subsequent constructed wetlands(CWs).The effects of high ammonium shocks on submerged macrophytes and epiphyti...The ammonium exceedance discharge from sewage treatment plants has a great risk to the stable operation of subsequent constructed wetlands(CWs).The effects of high ammonium shocks on submerged macrophytes and epiphytic biofilms on the leaves of submerged macrophytes in CWs were rarely mentioned in previous studies.In this paper,the 16S rRNA sequencing method was used to investigate the variation of the microbial communities in biofilms on the leaves of Vallisneria natans plants while the growth characteristics of V.natans plants were measured at different initial ammonium concentrations.The results demonstrated that the total chlorophyll and soluble sugar synthesis of V.natans plants decreased by 51.45%and 57.16%,respectively,and malondialdehyde content increased threefold after8 days if the initial NH_(4)^(+)-N concentration was more than 5 mg/L.Algal density,bacterial quantity,dissolved oxygen,and pH increased with high ammonium shocks.The average removal efficiencies of total nitrogen and NH_(4)^(+)-N reached 73.26%and 83.94%,respectively.The heat map and relative abundance analysis represented that the relative abundances of phyla Proteobacteria,Cyanobacteria,and Bacteroidetes increased.The numbers of autotrophic nitrifiers and heterotrophic nitrification aerobic denitrification(HNAD)bacteria expanded in biofilms.In particular,HNAD bacteria of Flavobacterium,Hydrogenophaga,Acidovorax,Acinetobacter,Pseudomonas,Aeromonas,and Azospira had higher abundances than autotrophic nitrifiers because there were organic matters secreted from declining leaves of V.natans plants.The analysis of the nitrogen metabolic pathway showed aerobic denitrification was the main nitrogen removal pathway.Thus,the nitrification and denitrification bacterial communities increased in epiphytic biofilms on submerged macrophytes in constructed wetlands while submerged macrophytes declined under ammonium shock loading.展开更多
Submerged abrasive waterjet peening(SAWJP)is an effective anti-fatigue manufacturing technology that is widely used to strengthen aeroengine components.This study investigated the correlation of SAWJP process paramete...Submerged abrasive waterjet peening(SAWJP)is an effective anti-fatigue manufacturing technology that is widely used to strengthen aeroengine components.This study investigated the correlation of SAWJP process parameters on surface integrity and fatigue life of titanium alloy TA19.SAWJP with different water pressures and standoff distances(SoDs)was conducted on the TA19 specimens.The surface integrity of the specimens before and after SAWJP with different process parameters was experimentally studied,including microstructure,surface roughness,microhardness,and compressive residual stress(CRS).Finally,fatigue tests of the specimens before and after SAWJP treatment with different process parameters were carried out at room temperature.The results highlighted that the fatigue life of the TA19 specimen can be increased by 5.46,5.98,and 6.28 times under relatively optimal process parameters,which is mainly due to the improved surface integrity of the specimen after SAWJP treatment.However,the fatigue life of specimens treated with improper process parameters is decreased by 0.55 to 0.69 times owing to the terrible surface roughness caused by the material erosion.This work verifies that SAWJP can effectively improve the surface integrity and fatigue life of workpieces,and reveals the relationship between process parameters,surface integrity,and fatigue life,which provides support for the promotion of SAWJP in the manufacturing fields.展开更多
基金supported by the National Outstanding Youth Science Fund Project of National Natural Science Foundation of China(52302031)National Natural Science Foundation of China(51932008 and 51772277)Central China Thousand Talents Project(204200510011).
文摘The reaction of carbon-free oxide-based(corundum,spinel,zirconia,and mullite)submerged entry nozzle(SEN)lining with rare earth inclusions and its anti-clogging effects under near working conditions were systematically studied.A variety of lining composite test methods were innovatively used to ensure the consistency of test conditions.The experimental results showed that the mullite(acidic oxide)has strong reactivity with rare earth inclusions,and the spinel(basic oxide)has stable chemical properties and weak reactivity with rare earth inclusions.Because alumina is one of the main reactants of clogging formation,corundum is not suitable for SEN lining.There are less clogs on the surface of zirconia,but it will be exsoluted and unstable.Therefore,solving the problem of zirconia exsolution will greatly strengthen its application in SEN lining.
文摘The finite volume method was applied to numerically simulate the bottom pressure field induced by regular waves,vehicles in calm water and vehicles in regular waves.The solution of Navier-Stokes(N-S)equations in the vicinity of numerical wave tank's boundary was forced towards the wave theoretical solution by incorporating momentum source terms,thereby reducing adverse effects such as wave reflection.Simulations utilizing laminar flow,turbulent flow,and ideal fluid models were all found capable of effectively capturing the waveform and bottom pressure of regular waves,agreeing well with experimental data.In predicting the bottom pressure field of the submerged vehicle,turbulent simulations considering fluid viscosity and boundary layer development provided more accurate predictions for the stern region than inviscid simulations.Due to sphere's diffractive effect,the sphere's bottom pressure field in waves is not a linear superposition of the wave's and the sphere's bottom pressure field.However,a slender submerged vehicle exhibits a weaker diffractive effect on waves,thus the submerged vehicle's bottom pressure field in waves can be approximated as a linear superposition of the wave's and the submerged vehicle's bottom pressure field,which simplifies computation and analysis.
文摘Rice varieties tolerant to submergence regulate shoot elongation during short-term submergence by expressing the SUB1A gene.In contrast,the deep-rooted DRO1 is effectively expressed under drought conditions to enhance water and nutrient uptake.This study investigates the growth and yield of rice with both SUB1A and DRO1 in the background of IR64,under early-season flooding,and mid-season drought.The study used a randomized complete design with two factors:soil moisture treatments(submergence,drought,and their combination)and genotypes.The genotypes included IR64,and three near-isogenic lines(NILs):NIL-SUB1DRO1,NIL-SUB1,and NIL-DRO1.Complete submergence was imposed for 7 days on 14-day-old seedlings,while drought was imposed on control and submerged plants following a 21-day recovery period from submergence,using 42-day-old plants.Variables were measured before and after treatments(submergence and drought),and at harvest or grain maturity.The stresses negatively affected the genotypes.At harvest,IR64 and NIL-SUB1DRO1 under both stresses showed a significant reduction in tiller numbers,shoot dry weights,and yields compared to their control plants.IR64 exhibited a significant delay in reaching flowering under all stresses.The rice introgression lines showed significant improvements in tolerance to the stresses.The study showed no negative consequences of combining drought and submergence tolerance in rice.
基金supported by the program for National Natural Science Foundation of China (Nos. 52174173, 52274188, and 52104190)the Joint Funds of the National Natural Science Foundation of China (No. U24A2091)+1 种基金The Natural Science Foundation of Henan Polytechnic University (No. B2021-2)Double FirstClass Initiative of Safety and Energy Engineering (Henan Polytechnic University) (Nos. AQ20240703 and AQ20230304)。
文摘Under submerged conditions, compared with traditional self-excited oscillating pulsed waterjets(SOPWs), annular fluid-enhanced self-excited oscillating pulsed waterjets(AFESOPWs) exhibit a higher surge pressure through self-priming. However, their pressure frequency and cavitation characteristics remain unclear, resulting in an inability to fully utilize resonance and cavitation erosion to break coal and rock. In this study, high-frequency pressure testing, high-speed photography, and large eddy simulation(LES) are used to investigate the distribution of the pressure frequency band, evolution law of the cavitation cloud, and its regulation mechanism of a continuous waterjet, SOPW, and AFESOPW. The results indicated that the excitation of the plunger pump, shearing layer vortex, and bubble collapse corresponded to the three high-amplitude frequency bands of the waterjet pressure. AFESOPWs have an additional self-priming frequency that can produce a larger amplitude under a synergistic effect with the second high-amplitude frequency band. A better cavitation effect was produced after self-priming the annulus fluid, and the shedding frequency of the cavitation clouds of the three types of waterjets was linearly related to the cavitation number. The peak pressure of the waterjet and cavitation erosion effect can be improved by modulating the waterjet pressure oscillation frequency and cavitation shedding frequency.
基金supported by National Key Research and Development Program of China(2023YFD1201403)The Science and Technology Innovation Program of Hunan Province(2023RC1077)+2 种基金Key Research and Development Projects of Hunan Provincial(2023NK2012)Hunan Provincial Science and Technology Talent Promotion Project(2023 TJ-Z09)The Hunan Agricultural Science and Technology Innovation Fund Project(2024CX096).
文摘Flooding can lead to oxygen deprivation in rapeseed,negatively affecting its growth and development and ul-timately reducing yields.Vitreoscilla hemoglobin(VHb),a bacterial hemoglobin with a high oxygen-binding affinity,plays a key role in enhancing oxygen uptake and metabolic efficiency under low-oxygen conditions.Through genetic transformation,we overexpressed the VHb gene in rapeseed,which resulted in significant im-provements in survival rate,root length,and biomass under submerged conditions.Additionally,we observed that transgenic plants developed adventitious roots in response to submergence stress.These transgenic plants also exhibited increased activities of ethanol dehydrogenase and pyruvate decarboxylase-enzymes associated with anaerobic respiration.Our findings indicate that VHb enhances flooding tolerance in rapeseed by promoting adventitious root formation and strengthening the plant's capacity for fermentation metabolism under anaerobic conditions.
基金supported by MHRD as researcher C.K.Neog received the MHRD Institute GATE scholarship from Govt.of India.
文摘This study investigates the effects of radiation force due to the rotational pitch motion of a wave energy device,which comprises a coaxial bottom-mounted cylindrical caisson in a two-layer fluid,along with a submerged cylindrical buoy.The system is modeled as a two-layer fluid with infinite horizontal extent and finite depth.The radiation problem is analyzed in the context of linear water waves.The fluid domain is divided into outer and inner zones,and mathematical solutions for the pitch radiating potential are derived for the corresponding boundary valve problem in these zones using the separation of variables approach.Using the matching eigenfunction expansion method,the unknown coefficients in the analytical expression of the radiation potentials are evaluated.The resulting radiation potential is then used to compute the added mass and damping coefficients.Several numerical results for the added mass and damping coefficients are investigated for numerous parameters,particularly the effects of the cylinder radius,the draft of the submerged cylinder,and the density proportion between the two fluid layers across different frequency ranges.The major findings are presented and discussed.
基金supported by the Fundamental Research Funds for the Central Universities(No.FRF-BD-23-01).
文摘Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,including bubble,electromagnetic stirring,filtration separation,fluid flow,and sedimentation,often struggle with the removal of fine inclusions.Apart from these known methods,pulsed electric current(PEC),as an emerging technology,has demonstrated immense potential and environmental advantages.PEC offers adjustable current parameters and simple equipment,making it an attractive alternative to traditional methods.Its green energy-saving features and excellent results in regulating inclusion morphology and migration,as well as inhibiting submerged entry nozzle(SEN)clogging,make it a promising technology.In comparison to continuous current technology,PEC has shown significant advantages in regulating inclusions,not only improving purification efficiency but also demonstrating outstanding performance in flow stability and energy consumption.The ability of PEC to efficiently reduce inclusion numbers enhances the purity and quality of molten steel,improving its mechanical properties.Currently,the theoretical basis for controlling the movement of inclusions by current is mainly composed of three major theories:the double electric layer theory,electromagnetic force reverse separation theory,and electric free energy drive theory.These theories together form an important framework for researchers to understand and optimize the behavior of impurity movement controlled by electric current.Looking ahead,PEC is expected to pave the way for new solutions in directional regulation of inclusion migration,efficient inclusion removal,SEN clogging prevention,and the purification of molten steel.
基金the University Grants Commission(UGC),Government of India for the UGC-Non-NET Fellowship during the PhD degree program(Grant No.R/Dev/IX-Sch/BHU-Res-Sch/2022-23/51137).
文摘Flooding in rice fields,especially in coastal regions and low-lying river basins,causes significant devastation to crops.Rice is highly susceptible to prolonged flooding,with a drastic decline in yields if inundation persists for more than 7 d,especially during the reproductive stage.Although the SUB1 QTL,which confers tolerance to complete submergence during the vegetative stage,has been incorporated into breeding programs,the development of alternative sources is crucial.These alternatives would broaden the genetic base,mitigate the influence of the genomic background,and extend the efficacy of SUB1 QTL to withstand longer submergence periods(up to approximately 21 d).Contemporary breeding strategies predominantly target submergence stress at the vegetative stage.However,stagnant flooding(partial submergence of vegetative parts)during the reproductive phase inflicts severe damage on the rice crop,leading to reduced yields,heightened susceptibility to pests and diseases,lodging,and inferior grain quality.The ability to tolerate stagnant flooding can be ascribed to several adaptive traits:accelerated aerenchyma formation,efficient underwater photosynthesis,reduced radial oxygen loss in submerged tissues,reinforced culms,enhanced reactive oxygen species scavenging within cells,dehydration tolerance post-flooding,and resistance to pests and diseases.A thorough investigation of the genetics underlying these traits,coupled with the integration of key alleles into elite genetic backgrounds,can significantly enhance food and income security in flood-prone rice-growing regions,particularly in coastal high-rainfall areas and low-lying river basins.This review aims to delineate an innovative breeding strategy that employs genomic,phenomic,and traditional breeding methodologies to develop rice varieties resilient to various dimensions of flooding stress at both the vegetative and reproductive stages.
基金supported by the Application Technology of Automotive Steels(No.2021040300048)the National Natural Science Foundation of China(No.52304347)+2 种基金Hebei Provincial Natural Science Foundation(No.E2019501008),China Baowu Low Carbon Metallurgy Innovation Foundation(BWLCF202320)Natural Science Foundation of Liaoning Province(Nos.2023-MSBA-135 and 2023-BSBA-107)Fundamental Research Funds for the Central Universities(Nos.N2409008 and N2409006).
文摘The electromagnetic swirling flow in nozzle(EMSFN)technique is designed to mitigate the adverse effects of unstable and uneven flow within the submerged entry nozzle in continuous casting.Utilizing electromagnetic forces,EMSFN stabilizes the flow within the nozzle,leading to a more controlled flow in the mold.Numerical simulations were used to quantitatively analyze the magnetic and flow fields in a slab continuous casting system under EMSFN.Results indicate that EMSFN significantly stabilizes the outflow from the nozzle,with stability increasing with higher current intensity.At 10,000 Ampere-turns(At)of the coil,meniscus fluctuations were unstable.They stabilized at 13,000 At,with minimal changes observed beyond this point.The optimal current intensity for stable mold flow,at a casting speed of 1.56 m/min,is 13,000 At.These findings confirm the effectiveness of EMSFN in stabilizing the internal flow field of the slab mold and determining optimal operational current intensity.
基金supported by the National Natural Science Foundation of China(22288102)。
文摘The large molecular weight and high hydrophilicity of chloramphenicol(CAP) residuals in wastewater led to severe degradation difficulty,which propelled the development of new wastewater degradation processes and reactors based on process intensification.This study enhanced the CAP degradation by ozone/peroxydisulfate(PDS) advanced oxidation process in a submerged rotating packed bed(SRPB)reactor.Compared the usage of different oxidants,it was indicated that the combination of O_(3) and PDS exhibited a higher degradation efficiency than ozone and PDS alone.The more desired degradation efficiency could be achieved at the operating conditions of ascending PDS concentration,SRPB rotational speed,ozone concentration,reduced initial CAP concentration,and the water qualities of ascended pH,lower Cl^(-)and initial CO_(3)^(2-) concentrations.Under the optimized conditions of C_(CAP)=20 mg·L^(-1),C_(O3)=30 mg·L^(-1),C_(PDS)=100 mg·L^(-1),and N=400 r·min^(-1),and water qualities of pH=10,the maximum chloramphenicol degradation efficiency of 97% and kinetic constant of 0.23 min^(-1) were achieved after treating 16 min.A comparison of the results with previously reported advanced oxidation processes of CAP indicated that the enhanced O^(3)/PDS advanced oxidation system using the SRPB can significantly improve the degradation efficiency of CAP.
基金financially supported by the National Key Research and Development Project,China(Nos.2018YFA0703300,2022YFB4600019)the National Natural Science Foundation of China(Nos.52275148,52405154)+2 种基金the Innovation Program Phase II of AECC Commercial Aircraft Engine Co.Ltd,China(No.HT-3RJC1053-2020)support by the Postdoctoral Fellowship Program of CPSF,China(No.GZB20240219)the Shanghai Sailing Program,China(No.24YF2708100).
文摘Submerged Abrasive Waterjet Peening(SAWJP)shows great application potential in augmenting the fatigue properties of metallic parts.Thus,the present work aims to investigate the influence of SAWJP on the Surface Integrity(SI)and Fretting Fatigue(FF)properties of Inconel 718(IN718)superalloy and illustrate the microstructural evolution,FF life improvement,and fretting wear mechanism.First,the SI of the IN718 specimen was examined following treatment via SAWJP.Results showed that the specimen subjected to SAWJP formed a total plastic deformation layer of 56μm.The maximum microhardness and Compressive Residual Stress(CRS)measured across the depth of the SAWJP-treated specimens exhibited an increase in values ranging between 522 HV and 541 HV and 1171–1380 MPa,respectively.The FF test results of the specimen before and after SAWJP treatment at ambient temperatures indicated that the FF life of the SAWJP-treated specimen surpassed that of the as-received specimen by a factor of 2.81.The examination of the FF fracture,contact surface,and crack propagation behavior revealed the crucial factors contributing to the enhanced FF resistance of the IN718 specimen,including the gradient nanostructure characterized by ultra-refined grains,substantial CRS,and elevated microhardness,which were all induced by the SAWJP treatment.
基金Sponsored by the Natural Science Foundation of Shaanxi Province (Grant No. S2025-JC-YB-0532)the Practice and Innovation Funds for Graduate Students of Northwestern Polytechnical University (PF2024044)
文摘Taking a C1x motor with a backward-facing step which can generate a typical corner vortex as a reference,a numerical methodology using large eddy simulation was established in this study.Based on this methodology,the position of the backward-facing step of the motor was computed and analyzed to determine a basic configuration.Two key geometrical parameters,the head cavity angle and submerged nozzle cavity height,were subsequently introduced.Their effects on the corner vortex motion and their interactions with the acoustic pressure downstream of the backward-facing step were analyzed.The phenomena of vortex acoustic coupling and characteristics of pressure oscillations were further explored.The results show that the maximum error between the simulations and experimental data on the dominant frequency of pressure oscillations is 5.23%,which indicates that the numerical methodology built in this study is highly accurate.When the step is located at less than 5/8 of the total length of the combustion chamber,vortex acoustic coupling occurs,which can increase the pressure oscillations in the motor.Both the vorticity and the scale of vortices in the downstream step increase when the head cavity angle is greater than 24°,which increases the amplitude of the pressure oscillation by maximum 63.0%.The submerged nozzle cavity mainly affects the vortices in the cavity itself rather than those in the downstream step.When the height of the cavity increases from 10 to 20 mm,the pressure oscillation amplitude under the main frequency increases by 39.1%.As this height continues to increase,the amplitude of pressure oscillations increases but the primary frequency decreases.
基金supported by National Natural Science Foundation of China(Grant Nos.52174324,51974213 and 52204351)the China Postdoctoral Science Foundation(2022M722487)+1 种基金Open fund project(Grant No.FMRUlab23-05)supported by Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Educationsupport under the scope of the COMET program within the K2 Center“Integrated Computational Material,Process and Product Engineering(IC-MPPE)”(Project No.886385).
文摘Cryogenic steels,i.e.,steels with maximum toughness at particularly low temperature,are increasingly becoming the focus of research.Cryogenic steels are usually alloyed with 5%–9%nickel.Ni can also be substituted by manganese as an austenite former.These high-manganese cryogenic grades are a cost-effective alternative to nickel-alloyed steels for use in liquefied natural gas storage tanks.The Mn content can then be more than 20 wt.%and lead to problems in production,particularly in the continuous casting process.In continuous casting of high-Mn-grades,quality issues and even breakout may result from the initial solidification behavior of the steel grades at high temperatures.Hot cracks form when a critical load is exceeded during solidification,close to the solidus temperature of the steel.A selected high-Mn-steel grade was characterized with respect to liquidus and solidus temperatures by means of thermal analysis and computational thermodynamics.In addition,so-called submerged split chill tensile tests were carried out to further understand the crack sensitivity of the solidifying shell for high-manganese cryogenic steels.The results reveal the presence of coarse hot tears,and also,a high frequency of hot cracks was observed at the location with the maximum accumulated strain,which is in line with the applied cracking criterion of Pierer and Bernhard for this investigation.In summary,the initial solidification phase of continuous casting poses a high risk of cracking for high-manganese cryogenic steel.
基金supported by the National Key Research and Development Program of China(2022YFB2602800)National Natural Science Foundation of China(No.52271261).
文摘For a generalized radiation problem,an infinitely long submerged horizontal cylinder is forced to vibrate periodically in the transverse direction,with a described elastic harmonic motion along its longitudinal direction.A critical frequency corresponds to the described wave number of elastic vibration,and the generalized hydrodynamic coefficients abruptly change in the vicinity of critical frequency.In this work,a numerical examination is carried out to study the characteristics of wave profiles and wave propagation in the vicinity of the critical frequency.Results show that below the critical frequency,the real parts of complex wave profiles have large values in the vicinity of the cylinder and decay to zero with the increasing distance from the cylinder.Meanwhile,the imaginary parts of complex wave profiles are all zero,which explains why the generalized radiation damping is zero when the vibration is less than the critical frequency.At far distances,no radiation wave is observed.When the vibration exceeds the critical frequency,the real and imaginary parts of the wave profiles oscillate harmonically and keep steady amplitudes.In addition,the generated radiation wave propagates obliquely outward.The influence of the cylinder’s submergence depth on the wave profile is also studied,and the results indicate that the amplitude of the wave profile decreases as the submergence depth of the cylinder increases.The 3D wave profiles are graphically presented to show the wave propagation characteristics in the vicinity of the critical frequency for this generalized radiation problem.This study provides a good reference for the interaction between fluid and slender elastic structures.
文摘The paper is focused on the design of artificial sand beaches at sheltered and exposed sites.The methodology applied includes the study of the most essential design parameters and the application of numerical models to compute the beach erosion and maintenance.The computed erosion volume decreases for coarser sand(0.5 mm sand instead of 0.3 mm).Beach erosion increases for more graded sand,but the effect is small(10%–15%).The slope of the artificial beach at sheltered sites is commonly between 1 to 15 and 1 to 30 in conditions with a micro tidal range and mild waves.Slopes between 1 to 30 and 1 to 50 are used for more open exposed sites.The effect of the upper and lower beach slope(1 to 15 or 1 to 20)on beach erosion is marginal for sand in the range of 0.3 to 0.5 mm.A break in slope is quickly adjusted by transport processes.The volume of beach sand required may be reduced by constructing a submerged sill at the toe of the beach.Analysis of costs shows that the construction costs including maintenance over a period of 50 years of a submerged sill are about the same as that of beach fill including maintenance.Hence,the beach fill volume can be twice as large for a solution without a sill.Beach erosion due to alongshore transport processes is minimum if the beach line of the planform is perpendicular to the main wave direction(equilibrium beach).
基金supported by the Youth Exploration Foundation of Chinese Research Academy of Environmental Sciences(No.2022YSKY-55).
文摘Various technologies and projects have been explored and developed for the synergetic control of environmental pollution and carbon emissions in aquatic ecosystems.Planting submerged vegetation in shallow waters was also expected to achieve this purpose.However,the magnitude and mechanism of carbon dioxide(CO_(2))emission affected by submerged vegetation is not clear enough in complex aquatic ecosystems.This study investigated the influences of submerged plants on CO_(2)emission,ecosystem metabolism features,and microbial community traits based on observations in river networks on the Changjiang River Delta.The results showed that CO_(2)emission from planted waters accounted for 73%of unplanted waters.Meanwhile,planted waters had higher dissolved organic carbon removal capacity in overlying water and higher potential of carbon sequestration in sediment at the same time.These distinctions between the two habitats were attributed to(1)improved CO_(2)and bicarbonate consumption in water columns via enhancing photosynthesis and(2)inhibited CO_(2)production by reconstructing the benthic microbial community.Additional eco-advantages were found in planted sediments,such as a high potential of methane oxidation and xenobiotics biodegradation and a low risk of becoming black and odorous.In brief,submerged vegetation is beneficial in promoting pollution removal and carbon retention synchronously.This study advances our understanding of the feedback between aquatic metabolism and CO_(2)emission.
基金supported by the Program for National Defense Science and Technology Foundation Strengtheningthe Youth Foundation of Rocket Force University of Engineering(Grant No.2021QN-B014)。
文摘A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms.
基金supported by the National Natural Science Foundation of China(Grants No.2022YFC3202602,52109013,and U2040205)the China Postdoctoral Science Foundation(Grant No.2021M701049).
文摘Submerged vegetation commonly grows and plays a vital role in aquatic ecosystems,but it is also regarded as a barrier to the passing flow.Numerical simulations of flow through and over submerged vegetation were carried out to investigate the effect of vegetation density on flow field.Numerical simulations were computationally set up to replicate flume experiments,in which vegetation was mimicked with flexible plastic strips.The fluid-structure interaction between flow and flexible vegetation was solved by coupling the two modules of the COMSOL packages.Two cases with different vegetation densities were simulated,and the results were successfully validated against the experimental data.The contours of the simulated time-averaged streamwise velocity and Reynolds stress were extracted to highlight the differences in mean and turbulent flow statistics.The turbulence intensity was found to be more sensitive to vegetation density than the time-averaged velocity.The developing length increased with the spacing between plants.The snapshots of the bending vegetation under instantaneous velocity and vorticity revealed that flexible vegetation responded to the effects of eddies in the shear layer by swaying periodically.The first two rows of vegetation suffered stronger approaching flow and were prone to more streamlined postures.In addition,the origin of tip vortices was investigated via the distribution of vorticity.The results reveal the variation of flow properties with bending submerged vegetation and provide useful reference for optimizationofrestorationprojects.
基金supported by the National Special Program of Water Environment(No.2017ZX07204002)the National Natural Science Foundation of China(No.41871082)。
文摘The ammonium exceedance discharge from sewage treatment plants has a great risk to the stable operation of subsequent constructed wetlands(CWs).The effects of high ammonium shocks on submerged macrophytes and epiphytic biofilms on the leaves of submerged macrophytes in CWs were rarely mentioned in previous studies.In this paper,the 16S rRNA sequencing method was used to investigate the variation of the microbial communities in biofilms on the leaves of Vallisneria natans plants while the growth characteristics of V.natans plants were measured at different initial ammonium concentrations.The results demonstrated that the total chlorophyll and soluble sugar synthesis of V.natans plants decreased by 51.45%and 57.16%,respectively,and malondialdehyde content increased threefold after8 days if the initial NH_(4)^(+)-N concentration was more than 5 mg/L.Algal density,bacterial quantity,dissolved oxygen,and pH increased with high ammonium shocks.The average removal efficiencies of total nitrogen and NH_(4)^(+)-N reached 73.26%and 83.94%,respectively.The heat map and relative abundance analysis represented that the relative abundances of phyla Proteobacteria,Cyanobacteria,and Bacteroidetes increased.The numbers of autotrophic nitrifiers and heterotrophic nitrification aerobic denitrification(HNAD)bacteria expanded in biofilms.In particular,HNAD bacteria of Flavobacterium,Hydrogenophaga,Acidovorax,Acinetobacter,Pseudomonas,Aeromonas,and Azospira had higher abundances than autotrophic nitrifiers because there were organic matters secreted from declining leaves of V.natans plants.The analysis of the nitrogen metabolic pathway showed aerobic denitrification was the main nitrogen removal pathway.Thus,the nitrification and denitrification bacterial communities increased in epiphytic biofilms on submerged macrophytes in constructed wetlands while submerged macrophytes declined under ammonium shock loading.
基金supported financially by the National Natural Science Foundation of China(Nos.52275148 and U21B2077)Natural Science Foundation of Shanghai(20ZR1415300)+1 种基金Innovation Program of Shanghai Municipal Education Commission(2019-01-07-00-02-E00068)Innovation Program Phase II of AECC Commercial Aircraft Engine Co.Ltd.(Grant No.HT-3RJC1053-2020)。
文摘Submerged abrasive waterjet peening(SAWJP)is an effective anti-fatigue manufacturing technology that is widely used to strengthen aeroengine components.This study investigated the correlation of SAWJP process parameters on surface integrity and fatigue life of titanium alloy TA19.SAWJP with different water pressures and standoff distances(SoDs)was conducted on the TA19 specimens.The surface integrity of the specimens before and after SAWJP with different process parameters was experimentally studied,including microstructure,surface roughness,microhardness,and compressive residual stress(CRS).Finally,fatigue tests of the specimens before and after SAWJP treatment with different process parameters were carried out at room temperature.The results highlighted that the fatigue life of the TA19 specimen can be increased by 5.46,5.98,and 6.28 times under relatively optimal process parameters,which is mainly due to the improved surface integrity of the specimen after SAWJP treatment.However,the fatigue life of specimens treated with improper process parameters is decreased by 0.55 to 0.69 times owing to the terrible surface roughness caused by the material erosion.This work verifies that SAWJP can effectively improve the surface integrity and fatigue life of workpieces,and reveals the relationship between process parameters,surface integrity,and fatigue life,which provides support for the promotion of SAWJP in the manufacturing fields.
