Since the ban on the use of organochlorine pesticides （OCPs） such as dichloro-diphenyl-trichloroethane （DDT） and hexachlorocyclohexane（HCH） in agriculture, their levels have generally dropped. In a number of cas...Since the ban on the use of organochlorine pesticides （OCPs） such as dichloro-diphenyl-trichloroethane （DDT） and hexachlorocyclohexane（HCH） in agriculture, their levels have generally dropped. In a number of cases, however, the levels of these OCPs were found to be unchanging or even increasing after the ban. With the aim to unveil the possible causes of these exceptions, we collected two lake cores from King George Island, West Antarctica, and determined their accumulation flux profiles and temporal trends of these OCPs. In the lake core sediments with glacier meltwater input, the accumulation flux of DDT shows an abnormal peak around 1980s in addition to the expected one in 1960s. In the lake core sediments without glacier meltwater input, the accumulation flux of DDT shows a gradual decline trend after the peak in 1960s. This striking difference in the DDT flux profiles between the two lake cores is most likely caused by the regional climate warming and the resulted discharge of the DDT stored in the Antarctic ice cap into the lakes in the Antarctic glacier frontier. Furthermore, to investigate the change of OCPs loadings in the Antarctic coastal ecosystem, we reconstructed the HCH and DDT concentration profiles in penguin droppings and observed a gradual increase for the former and a continuous decrease for the latter during the past 50 years. The increase of HCH seems to be due to the regional warming from the early 1970s and the resulted HCH discharge to the coastal ecosystem by glaciers＇ meltwater and the illegal use of HCH in the Southern Hemisphere in the recent decade. The different temporal trends of HCH and DDT accumulation rate in the lake core with glacier meltwater input and the aged penguin droppings can be explained by their different water-soluble property.展开更多
The present study aimed to investigate the effect of relative humidity(RH) at either acute or chronic moderate ambient temperature(Ta) on growth performance and droppings' corticosterone metabolites of broilers.Tw...The present study aimed to investigate the effect of relative humidity(RH) at either acute or chronic moderate ambient temperature(Ta) on growth performance and droppings' corticosterone metabolites of broilers.Two experiments were conducted: effect of RH(35,60 or 85%) on average daily feed intake(ADFI) and droppings' corticosterone metabolites at acute(1 d: 20–26 or 31–20°C,26 or 31°C for 6 h d–1 at 10:00–16:00) moderate Ta(experiment 1) and effect of RH(35,60 or 85%) on growth performance and droppings' corticosterone metabolites at chronic(step-wisely increasing temperature by 3°C every 3 d from 20 to 32°C within 15 d: 20–23–26–29–32°C) moderate Ta(experiment 2).Droppings were collected at the 2,4,6,8,and 22 h after Ta-RH controlled in experiment 1 and at the 2,4,6,and 22 h after Ta controlled to 32°C in experiment 2.The results showed that: 1) In experiment 1,85% RH increased(P<0.05) the droppings' corticosterone metabolites at the 2,6,8,and 22 h and 35% RH increased(P<0.05) it at the 2 and 22 h compared to the 60% RH.Moreover,85% RH further increased(P<0.05) it compared to the 35% RH,however,no difference(P>0.05) was found in ADFI among the three RH groups at acute moderate 26°C; 35 and 85% RH increased(P<0.05) droppings' corticosterone metabolites at the 2,6,8 and 22 h and decreased(P<0.05) ADFI compared to the 60% RH,moreover,85% RH further increased(P<0.05) droppings' corticosterone metabolites and further decreased(P<0.05) ADFI compared to the 35% RH at acute moderate 31°C; and the average of droppings' corticosterone metabolites in the whole period had a negative correlation(P<0.02) with the ADFI.2) In experiment 2,85% RH increased(P<0.01) droppings' corticosterone metabolites only at the 2 h and decreased(P<0.02) ADFI and average daily gain(ADG) compared to the 60% RH,no difference(P>0.05) in droppings' corticosterone metabolites was found between the 35 and 60% RH,however,35% RH decreased(P<0.01) ADG compared to the 60% RH,and the average of droppings' corticosterone metabolites in the whole period also had a negative correlation(P<0.02) with ADFI and ADG.In conclusion,droppings' corticosterone metabolites could be used as a RH stress index and low and high RH,especially high RH,reduced growth performance possibly through inducing RH stress at moderate temperature.展开更多
<span style="font-family:Verdana;">The</span><span><span style="font-family:Verdana;"> use of organic manures, constitute an alternative to that of polluting artificial fert...<span style="font-family:Verdana;">The</span><span><span style="font-family:Verdana;"> use of organic manures, constitute an alternative to that of polluting artificial fertilizers. In this study, the effect of various levels of hen droppings fertilization on the production of biomass, chemical composition and carrying capacity of </span><i><i><span style="font-family:Verdana;">P</span></i><span><span style="font-family:Verdana;">. </span><i><span style="font-family:Verdana;">clandestinum</span></i><span style="font-family:Verdana;"></span></span></i> </span><span style="font-family:Verdana;">were evaluated at the Research and Experimental Farm (REF) and at the Animal Nutrition and Feeding Laboratory of </span><span style="font-family:Verdana;">the University of Dschang, between April and September 2016. A completely randomized block design comparing three nitrogen level of fertilization in hen droppings form (0;100 and 200 kg N/ha) on 4 m</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> plot of </span><span style="font-family:Verdana;"><i></i></span><i><i><span style="font-family:Verdana;">P</span></i><span><span style="font-family:Verdana;">. </span><i><span style="font-family:Verdana;">clandestinum</span></i><span style="font-family:Verdana;"></span></span></i><span style="font-family:Verdana;"> were used. Each treatment was carried out in four replications for a total of 12 experimental plots. Then a sample of 500 g of forage has been collected in the center of each plot, then dried and used for the evaluation of the biomass and the</span><span><span style="font-family:Verdana;"> chemical composition of <i></i></span><i><i><span style="font-family:Verdana;">P</span></i><span><span style="font-family:Verdana;">. </span><i><span style="font-family:Verdana;">clandestinum</span></i><span style="font-family:Verdana;"></span></span></i>, </span><span style="font-family:Verdana;">according to the level of fertilization and the cutting frequency. The results showed that the fertilization with the hen droppings positively influenced (p < 0.05) regenera</span><span style="font-family:Verdana;">tion at the first cutting frequency and the highest value (47.12 cm) was obtained with of 200 kg N/ha rate of fertilization. The biomass of this fodder increased significantly (p < 0.05) with the level of fertilization with hen droppings. Besides, it decrease</span><span style="font-family:Verdana;">s</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> with the increasing cutting of frequency whatever the level of fertilization. Independently of the fertilization and the cutting frequency, the maximum biomass (6.22 t DM/ha) was obtained with the first cutting at the 200 kg N/ha of hen droppings fertilization. The fertilization influenced in variable way the chemical composition of </span><span style="font-family:Verdana;"><i></i></span><i><i><span style="font-family:Verdana;">P</span></i><span><span style="font-family:Verdana;">. </span><i><span style="font-family:Verdana;">clandestinum</span></i><span style="font-family:Verdana;"></span></span></i></span><span style="font-family:Verdana;">. The dry matter and organic matter content decrease with the level of fertilization and the highest values (83.79% and 89.39% respectively for the DM and OM) were obtained on the control plot at the third and the first cutting. Moreover, the ash and crude protein contents increased significantly (p < 0.05) with the cutting frequency of cutting and the level of fertilization applied. The highest ash (19.34% DM) and CP (20.04% DM) contents were obtained with of 200 kg N/ha of hen droppings at the second cutting frequency.</span>展开更多
Background:Pseudomonas aeruginosa and Acinetobacter baumannii are common nosocomial pathogens in hospital settings.Recently,they have also been found in non-hospital environments,such as poultry farms.While most studi...Background:Pseudomonas aeruginosa and Acinetobacter baumannii are common nosocomial pathogens in hospital settings.Recently,they have also been found in non-hospital environments,such as poultry farms.While most studies in Ethiopia have focused on these bacteria's antibiotic resistance patterns in hospitals,information regarding their prevalence and resistance in veterinary settings,particularly poultry farms,is limited.This study aimed to assess the prevalence and antibiotic resistance patterns of P.aeruginosa and A.baumannii isolated from chicken droppings on poultry farms.Methods:A cross-sectional study was conducted from March 2022 to June 2022.A total of 87 poultry farms were included in this study,and pooled chicken dropping samples were collected.The samples were subsequently transferred to buffered peptone water and cultured on MacConkey agar.Species of the isolates were identified via routine biochemical tests,including oxidase,catalase,urease,Simon's citrate,sulfide indole motility medium,triple sugar iron agar and growth at temperatures of 37℃ and 42℃.The Kirby–Bauer disk diffusion technique was used for antibiotic susceptibility testing.The data were entered into EpiData version 4.6 and then exported to SPSS version 26 for analysis.Fisher's exact test was used to observe an appropriate association between independent variables and the occurrence of isolates.The results are presented in the text,figures and tables.Results:Among the 87 poultry farms,41(47.1%)were positive for Pseudomonas and Acinetobacter.Among these strains,24(27.6%)P.aeruginosa strains and 13(14.9%)A.baumannii strains were recovered.P.aeruginosa showed complete resistance to tetracycline(24,100.0%)and trimethoprim-sulfamethoxazole(24,100.0%).Additionally,there was a high rate of resistance to ciprofloxacin(13,54.2%)and amikacin(12,50.0%).Similarly,13(100.0%)A.baumannii isolates were resistant to tetracycline,and 12(92.3%)were resistant to trimethoprim-sulfamethoxazole.However,both isolates presented lower resistance rates to piperacillintazobactam(4,9.8%)and cefepime(7,17.1%).Both A.baumannii and P.aeruginosa exhibited multidrug resistance in 10/13(76.9%)and 16/24(66.7%)of the strains,respectively.The overall prevalence of multidrug resistance in this study was 28/41(68.3%).Conclusion:This study demonstrated that poultry farms may be potential reservoirs for P.aeruginosa and A.baumannii,including antibiotic-resistant strains.This is a significant concern to public health because poultry farmers may be contaminated,increasing their dissemination to the community.Therefore,poultry farmers should improve sanitation and reduce the misuse and overuse of antibiotics at poultry farms.展开更多
Lipid biomarkers in AD2 penguin droppings-amend soil core from the Ardley Island,Western Antarctic,were dated using 210Pb.Changes in the fatty acid ratios of nC18:2/nC18:0 from the penguin droppings reflect climate ch...Lipid biomarkers in AD2 penguin droppings-amend soil core from the Ardley Island,Western Antarctic,were dated using 210Pb.Changes in the fatty acid ratios of nC18:2/nC18:0 from the penguin droppings reflect climate changes coincident with ENNO events during 1931-2006.The occurrence of the minimum values in the depth of 2-3 and 6-7 cm are consistent with the end of ENSO in 1958 and 1983,respectively,reflecting a lag of the biomarker records in AD2 penguin droppings-amend soil in climatic signatures.This study also reveals that the changes in the relative concentration of n-alkanes nC23,the ratios of nC23/nC17 and nC21 /nC22+,and carbon preferential index(CPI) values collectively indicate the variations of soil microor-ganism and lower plant,which are closely related to climate changes.The ratios of bacterial fatty acids iC15:0/aC15:0 reflect the increasing significance of microorganism activities during the two periods that occurred at the end years of ENSO.Decrease in CPIA value and increase in nC21 /nC22+ indicate that low molecular weight fatty acids are derived from microorganism;and their insignificant correlation with Pr/Ph suggests microorganisms play an important role in the relatively simply ecosystem in the Antarctic and are closely linked to climatic conditions.In addition,the observed penguin community indicates the popula-tion of penguin can largely reflect the impacts of global climate changes on the ecosystem.展开更多
The characteristics of chicken droppings are closely related to the health of chickens.Veterinarians often judge the health of a chicken by looking at whether the chicken poop is normal.At present,the inspection of ab...The characteristics of chicken droppings are closely related to the health of chickens.Veterinarians often judge the health of a chicken by looking at whether the chicken poop is normal.At present,the inspection of abnormal chicken droppings in chicken coops relies on manual observation,which is inefficient,accurate varies from person to person,labor-intensive,and has the risk of cross-infection.To achieve efficient,accurate,and intelligent identification of abnormal chicken droppings,an abnormal chicken droppings detection method based on improved Faster Region-based Convolutional Neural Network(Faster R-CNN)was proposed in this study.In the feature extraction network stage,deformable convolution was used and combined with Path Augmentation-Feature Pyramid Network(PA-FPN)to improve the extraction ability of features at different scales.In the Region Proposal Network(RPN)stage,the K-means++algorithm was used to cluster the dataset and obtain the Anchor-ratio which is more suitable for the chicken poop object,and the FocalLoss classification loss function was used to improve the classification ability of difficult samples.In the regional convolutional network stage,the region of interest calibration algorithm was used instead to obtain more accurate localization information.The experimental results show that the improved Faster R-CNN structure can reach an accuracy of 98.8%for abnormal chicken poop detection,and the average accuracy mean value was improved by 27.8%.The results can provide a key core technology support for establishing an efficient abnormal chicken droppings online detection system.展开更多
Aqueous zinc-ion batteries(AZIBs) are regarded as one of the most promising energy conversion and storage devices.Nevertheless,side reactions and dendrite growth on the zinc metal anode hinder their widespread applica...Aqueous zinc-ion batteries(AZIBs) are regarded as one of the most promising energy conversion and storage devices.Nevertheless,side reactions and dendrite growth on the zinc metal anode hinder their widespread application.In this study,hemin was employed as a multi-functional artificial interface for the first time to inhibit the disordered growth of zinc dendrites and mitigate side reactions.Theoretical calculations indicate that hemin is preferentially adsorbed onto the zinc anode,thus blocking the interaction between the active zinc anode and electrolyte.Compared with zinc foil,the Hemin@Zn anode demonstrates enhanced corrosion resistance,a decrease in hydrogen evolution,and more orderly deposition of zinc.As expected,the symmetric cell with Hemin@Zn anode can sustain up to 4000 h at 0.2 mA/cm^(2),0.2 mAh/cm^(2).Asymmetric Zn//Cu cells exhibit an average coulombic efficiency exceeding 99.72 % during 500 cycles.Moreover,the full cell Hemin@Zn//NH_(4)V_(4)O_(10) delivers a superior capacity up to 367 m Ah/g and the discharge capacity retention reaches 124 mAh/g after 1200 cycles even at a current density of 5 A/g.This work provides a simple and effective method for constructing a robust artificial interface to promote the application of long-life AZIBs.展开更多
Predicting the precise impacts of climate change on extreme winds remains challenging,yet strong storms are widely expected to occur more frequently in a warming climate.Wind barriers are commonly used on bridges to r...Predicting the precise impacts of climate change on extreme winds remains challenging,yet strong storms are widely expected to occur more frequently in a warming climate.Wind barriers are commonly used on bridges to reduce aerodynamic loads on trains through blocking effects.This study develops a novel wind barrier based on Tesla valves,which not only blocks incoming flow but also dissipates mechanical energy through fluid collision.To demonstrate this energy-dissipation capability,a Tesla plate is placed in a circular duct to examine its influence on pressure drop.Experimental tests and numerical simulations comparing a Tesla channel and a straight channel of equal porosity show that the Tesla configuration produces a substantially higher pressure drop.Validated simulations are then used to conduct a parametric study to optimize the design.By varying the channel ratio,diversion angle,number of dissipation units,and porosity,velocity–pressure-drop relationships for different Tesla plates are obtained.The results show that larger channel ratios,larger diversion angles,and more dissipation units,combined with lower porosity,all increase pressure drop and thus enhance energy dissipation.Finally,the aerodynamic coefficients of a high-speed train on a bridge deck equipped with a Tesla-type barrier are evaluated and compared with those for a traditional straight-channel barrier.The Tesla-type barrier reduces the train’s lateral force coefficient to only 15%–25%of that produced by the traditional barrier,and it generates an additional stabilizing force that further improves running safety.展开更多
Heat exchangers play a crucial role in thermal energy systems,with their performance directly impacting efficiency,cost,and environmental impact.Apowerful technique for performance improvement can be given by passive ...Heat exchangers play a crucial role in thermal energy systems,with their performance directly impacting efficiency,cost,and environmental impact.Apowerful technique for performance improvement can be given by passive enhancement strategies,which are characterized by their dependability and minimal external power requirements.This comprehensive review critically assesses recent advancements in such passive methods to evaluate their heat transfer mechanisms,performance characteristics,and practical implementation challenges.Our methodology involves a systematic and comprehensive analysis of various heat transfer enhancement techniques,including surface modifications,extended surfaces,swirl flow devices,and tube inserts.This approach synthesizes and integrates findings from a broad spectrum of experimental investigations and numerical simulations to establish a cohesive understanding of their performance characteristics and underlyingmechanisms.Based on the findings,passive heat transfer techniques result in significant improvements in thermal performance;for instance,corrugated and roughened surfaces increase the heat transfer coefficient by 50%–200%,and advanced insert geometries,such as modified twisted tapes,can increase it by more than 300%,typically accompanied by significant pressure-drop penalties.However,an important finding is the general trade-off between enhanced heat transfer and higher frictional loss,which requires optimization depending on the applications.Finally,this review also provides recommendations that will document the gaps of various passive techniques in heat exchangers to future address.展开更多
Coiled tube heat exchangers are widely preferred in shell structures due to their superior heat transfer performance,driven by favorable flow characteristics.This study investigates the effect of modifying coil and sh...Coiled tube heat exchangers are widely preferred in shell structures due to their superior heat transfer performance,driven by favorable flow characteristics.This study investigates the effect of modifying coil and shell configurations on heat transfer efficiency.Two key enhancements were examined:adding fins to the outer coil surface and integrating longitudinal slots within a hollowed shell.These modifications promote turbulence and extend heat transfer duration,thereby improving performance.However,they also introduce challenges,including increased pressure loss andmanufacturing complexity.Numerical simulationswere conducted usingANSYS Fluent 2024R1 under identical boundary conditions.With a fixed cold-side flow rate of 3 L/min,the input temperatures for the hot and cold fluids were 333.15 and 291.65 K,respectively.The hot-side flow rate varied between 2 and 6 L/min.Simulation outcomes were reported for the objectives of the study that included the improvement in heat exchangers’heat transfer enhancement.As it was indicated in the study outcomes,the average heat transfer rate increased by 15.56%,the overall heat transfer coefficient enhanced by about 29.51%,and the convective heat transfer coefficient improved by about 75.96%compared to the conventional shell-and-coil tube heat exchanger model.However,the modified technique resulted in a significant pressure drop.展开更多
This study examines the hemodynamics of non-Newtonian blood flow in stenosed arteries,focusing on the roles of stenosis severity,guidewire presence,and various non-Newtonian constitutive models.Computational simulatio...This study examines the hemodynamics of non-Newtonian blood flow in stenosed arteries,focusing on the roles of stenosis severity,guidewire presence,and various non-Newtonian constitutive models.Computational simulations using the generalized power-law,Casson,and Carreau-Yasuda models are conducted for stenosis severities of 50%,70%,80%,and 90%.Results indicate that stenosis severity exerts the greatest influence on pressure and wall shear stress(WSS),with increasing severity leading to higher pressure drops and WSS maxima.Guidewire presence reduces recirculation zone lengths by nearly 60%across different severities and raises the trans-stenotic pressure drop up to 120%.While the choice of constitutive model has minimal impact on hemodynamics within the stenotic region,it becomes crucial in healthy vessels,where non-Newtonian effects are more pronounced.In cases with a guidewire,pressure gradients in the healthy region show up to 18.8%differences between non-Newtonian models.These findings highlight the dominant roles of stenosis severity and guidewire presence in shaping hemodynamics within stenotic regions while emphasizing the need for precise constitutive modeling to capture flow characteristics in healthy vascular segments.展开更多
This study investigates in-station pressure drop mechanisms in a shale gas gathering system,providing a quantitative basis for flow system optimization.Computational fluid dynamics(CFD)simulations,based on field-measu...This study investigates in-station pressure drop mechanisms in a shale gas gathering system,providing a quantitative basis for flow system optimization.Computational fluid dynamics(CFD)simulations,based on field-measured parameters related to a representative case(a shale gas platform located in Sichuan,China)are conducted to analyze the flow characteristics of specific fittings and manifolds,and to quantify fitting resistance coefficients and manifold inlet interference.The resulting coefficients are integrated into a full-station gathering network model in PipeSim,which,combined with production data,enables evaluation of pressure losses and identification of equivalent pipeline blockages.The results indicate that the resistance coefficients,valid only for fittings under the studied field-specific geometries,are 0.21 for 90◦elbows in the fully open position,0.16 for gate valve passages in the fully open position,and 2.3 for globe valve passages.Manifold interference decreases with lower high-pressure inlet values,whereas inlets farther from the high-pressure side experience stronger disturbances.Interestingly,significant discrepancies between simulated and measured pressure drops reveal partial blockages,corresponding to effective diameter reductions of 65 mm,38 mm,44 mm,38 mm,and 28 mm for Wells 1#,3#,5#,and 6#,respectively.展开更多
The airflow mechanics in adult nasal airways,whether healthy or abnormal,are extensively studied and investigated,but the flow mechanics in child nasal airways remain underexplored.This study investigates the airflow ...The airflow mechanics in adult nasal airways,whether healthy or abnormal,are extensively studied and investigated,but the flow mechanics in child nasal airways remain underexplored.This study investigates the airflow mechanics in the child’s nasal upper airway with adenoid hypertrophy,with an adenoid nasopharyngeal ratio(AN of 0.9),under cyclic inhalation and exhalation.An inlet respiratory cycle with three different flow rates(3.2 L/min calm breathing,8.6 L/min normal breathing,and 19.3 L/min intensive breathing)was simulated by using the computational fluid dynamics approach.To better capture the interaction between airflow and the flexible airway tissue,fluid-structure interaction analysis was performed at the normal breathing rate.Comparing the airflow dynamics during inhalation and exhalation,the pressure drops,nasal resistance,and wall shear stress show significant differences in the nasopharyngeal region for all different flow rates.This observation suggests that the inertial effect associated with the transient flow is important during exhalation and inhalation.Furthermore,the considerable temporal variation in flow rate distribution across a specific cross-section of the nasal airway highlights the critical role of transient data in virtual surgery planning and data for clinical decisions.展开更多
Particle-and droplet-laden flows are central to many problems in mechanics and transport.They occur in sedimentladen boundary layers,gas-solid and gas-liquid dispersions,and surface-water films driven by external forc...Particle-and droplet-laden flows are central to many problems in mechanics and transport.They occur in sedimentladen boundary layers,gas-solid and gas-liquid dispersions,and surface-water films driven by external forcing.They also underpin practical applications ranging from environmental transport to high-speed and aerothermal systems.Despite decades of progress,prediction remains difficult.The physics spans a wide range of scales and often couples turbulence,interphase momentum exchange,collisions,and interfacial transport.Reliable computation therefore requires both robust numerical methodology and careful physical interpretation.展开更多
The stability and fracture behavior of a goaf roof beneath an open-pit bench are critical concerns,especially under impact loading.However,the effect of the thickness-to-span ratio on dynamic failure modes remains lar...The stability and fracture behavior of a goaf roof beneath an open-pit bench are critical concerns,especially under impact loading.However,the effect of the thickness-to-span ratio on dynamic failure modes remains largely unexplored,as existing research focuses mainly on static stability.Energy dissipation and instability evolution under impact loading require further study.To address this gap,this study conducts drop-weight impact experiments on specimens with circular perforations,complemented by numerical simulations.By integrating dimensional analysis,cusp catastrophe theory,and strength reduction techniques,the dynamic instability mechanism of goaf roofs with varying thickness-to-span ratios is revealed.Results show that the thickness-to-span ratio significantly influences energy accumulation and dissipation during roof failure.A higher ratio increases both the magnitude and rate of energy dissipation,particularly during crack initiation and stable propagation,while its impact diminishes in the final failure stage.Optimizing the thickness-to-span ratio within a critical range enhances structural stability,improving the safety factor by up to 83%.However,beyond a certain threshold,additional thickness yields diminishing benefits.This study provides new insights into the energy-based instability mechanism of goaf roofs under impact loads,establishing a theoretical foundation for early warning systems and optimized safety design.展开更多
With the change of the main influencing factors such as structural configuration and impact conditions,reinforced concrete slabs exhibit different mechanical behaviors with different failure patterns,and the failure m...With the change of the main influencing factors such as structural configuration and impact conditions,reinforced concrete slabs exhibit different mechanical behaviors with different failure patterns,and the failure modes are transformed.In order to reveal the failure mode and transformation rule of reinforced concrete slabs under impact loads,a dynamic impact response test was carried out using a drop hammer test device.The dynamic data pertaining to the impact force,support reaction force,structural displacement,and reinforcement strain were obtained through the use of digital image correlation technology(DIC),impact force measurement,and strain measurement.The analysis of the ultimate damage state of the reinforced concrete slab identified four distinct types of impact failure modes:local failure by stamping,overall failure by stamping,local-overall coupling failure,and local failure by punching.Additionally,the influence laws of hammerhead shape,hammer height,and reinforcement ratio on the dynamic response and failure mode transformation of the slab were revealed.The results indicate that:(1)The local damage to the slab by the plane hammer is readily apparent,while the overall damage by the spherical hammer is more pronounced.(2)In comparison to the high reinforcement ratio slabs,the overall bending resistance of the low reinforcement ratio slabs is significantly inferior,and the slab back exhibits further cracks.(3)As the hammer height increases,the slab failure mode undergoes a transformation,shifting from local failure by stamping and overall failure by stamping to local-overall coupling failure and local failure by punching.(4)Three failure mode thresholds have been established,and by comparing the peak impact force with the failure thresholds,the failure mode of the slab can be effectively determined.展开更多
The ratio of the pressure drop force to the drag force,C_(P),is concerned for a non-closely fitting spherical particle settling along the central line in long rectangular tubes with different A_(r)(A_(r)is W/H,where W...The ratio of the pressure drop force to the drag force,C_(P),is concerned for a non-closely fitting spherical particle settling along the central line in long rectangular tubes with different A_(r)(A_(r)is W/H,where W,H is length of the longer and shorter side of the rectangle respectively).Under Stokes flow conditions,C_(P0)for an infinitely small sphere in long rectangular tubes and C_(P)for a sphere in a long channel between two parallel layered barriers are both calculated.Then C_(P)of a sphere settling in long rectangular tubes are conducted with the direct-forcing fictitious domain(DF/FD)method.At large Reynolds number,the sphere settles unstably with a fluctuating velocity and C_(P).The fluctuation of Cp is much stronger than that of velocity and both fluctuations are stronger for less confined sphere.The influences of the particle Reynolds number(Re_(p))on C_(P)is similar to the existing experimental results in long circular tubes.At low Re_(p),C_(P)is a determined value and is calculated.For a given d/H(d sphere diameter),Cp gets its maximum value at one A_(r)in the range of[1,1.5].For a given A_(r),C_(P)is a quadratic function of d/H similar to that in a circular tube,and parameters of the quadratic function are got by curve fitting from numerical data.The constant term coefficients got have almost no difference with C_(P0)and are furtherly replaced by the latter to get new quadratic coefficients C_(P1).Lastly,an algebraic correlation of C_(P1)to A_(r)is developed.The predictions of Cp are good with a maximum relative error about 1.5%for a sphere with d/H not greater than0.7,compared to numerical results.展开更多
Allergic conjunctivitis is a common ocular surface condition.Although corticosteroids are potent antiinflammatory agents for its management,their use is often restricted by potential side effects.Conventional eye drop...Allergic conjunctivitis is a common ocular surface condition.Although corticosteroids are potent antiinflammatory agents for its management,their use is often restricted by potential side effects.Conventional eye drops face challenges such as short retention time and poor corneal permeability,resulting in low drug bioavailability.To overcome these limitations,we developed a preservative-free synthetic high-density lipoprotein(sHDL)nanodisc eye drop containing dexamethasone palmitate.This novel formulation enhances drug stability and extends retention time on the ocular surface.In a mouse model of ovalbumin(OVA)-induced allergic conjunctivitis,the nanodisc eye drop significantly alleviated symptoms while reducing corticosteroid concentration,demonstrating excellent safety and biocompatibility.This innovative approach shows great promise for the treatment of allergic conjunctivitis and may lay the groundwork for new therapeutic strategies in anterior ocular disease management.展开更多
With the increasing miniaturization of systems and surging demand for power density,accurate prediction and control of two-phase flow pressure drop have become a core challenge restricting the performance of microchan...With the increasing miniaturization of systems and surging demand for power density,accurate prediction and control of two-phase flow pressure drop have become a core challenge restricting the performance of microchannel heat exchangers.Pressure drop,a critical hydraulic characteristic,serves as both a natural constraint for cooling systems and determines the power required to pump the working fluid through microchannels.This paper reviews the characteristics,prediction models,and optimization measures of two-phase flow pressure drop for low-boiling-point working fluids in microchannels.It systematically analyzes key influencing factors such as fluid physical properties,operating conditions,channel geometry,and flow patterns,and discusses the complex mechanisms of pressure drop under the coupling effect of multi-physical fields.Mainstream prediction models are reviewed:the homogeneous flow model simplifies calculations but shows large deviations at low quality;the separated flow model considers interphase interactions and can be applied to micro-scales after modification;the flow-pattern-based model performs zoned modeling but relies on subjective classification;machine learning improves prediction accuracy but faces the“black-box”problem.In terms of optimization,channel designs are improved through porous structures and micro-rib arrays,and flow rate distribution is optimized using splitters to balance pressure drop and heat transfer performance.This study provides theoretical support for microchannel thermal management in high-power-density devices.展开更多
文摘Since the ban on the use of organochlorine pesticides （OCPs） such as dichloro-diphenyl-trichloroethane （DDT） and hexachlorocyclohexane（HCH） in agriculture, their levels have generally dropped. In a number of cases, however, the levels of these OCPs were found to be unchanging or even increasing after the ban. With the aim to unveil the possible causes of these exceptions, we collected two lake cores from King George Island, West Antarctica, and determined their accumulation flux profiles and temporal trends of these OCPs. In the lake core sediments with glacier meltwater input, the accumulation flux of DDT shows an abnormal peak around 1980s in addition to the expected one in 1960s. In the lake core sediments without glacier meltwater input, the accumulation flux of DDT shows a gradual decline trend after the peak in 1960s. This striking difference in the DDT flux profiles between the two lake cores is most likely caused by the regional climate warming and the resulted discharge of the DDT stored in the Antarctic ice cap into the lakes in the Antarctic glacier frontier. Furthermore, to investigate the change of OCPs loadings in the Antarctic coastal ecosystem, we reconstructed the HCH and DDT concentration profiles in penguin droppings and observed a gradual increase for the former and a continuous decrease for the latter during the past 50 years. The increase of HCH seems to be due to the regional warming from the early 1970s and the resulted HCH discharge to the coastal ecosystem by glaciers＇ meltwater and the illegal use of HCH in the Southern Hemisphere in the recent decade. The different temporal trends of HCH and DDT accumulation rate in the lake core with glacier meltwater input and the aged penguin droppings can be explained by their different water-soluble property.
基金funded by the Key National Research and Development Program Project of China (2016YFD0500509)the National Science and Technology Support Plan Project of China (2012BAD39B02)the Chinese Academy of Agricultural Science and Technology Innovation Team Project (ASTIPIAS07)
文摘The present study aimed to investigate the effect of relative humidity(RH) at either acute or chronic moderate ambient temperature(Ta) on growth performance and droppings' corticosterone metabolites of broilers.Two experiments were conducted: effect of RH(35,60 or 85%) on average daily feed intake(ADFI) and droppings' corticosterone metabolites at acute(1 d: 20–26 or 31–20°C,26 or 31°C for 6 h d–1 at 10:00–16:00) moderate Ta(experiment 1) and effect of RH(35,60 or 85%) on growth performance and droppings' corticosterone metabolites at chronic(step-wisely increasing temperature by 3°C every 3 d from 20 to 32°C within 15 d: 20–23–26–29–32°C) moderate Ta(experiment 2).Droppings were collected at the 2,4,6,8,and 22 h after Ta-RH controlled in experiment 1 and at the 2,4,6,and 22 h after Ta controlled to 32°C in experiment 2.The results showed that: 1) In experiment 1,85% RH increased(P<0.05) the droppings' corticosterone metabolites at the 2,6,8,and 22 h and 35% RH increased(P<0.05) it at the 2 and 22 h compared to the 60% RH.Moreover,85% RH further increased(P<0.05) it compared to the 35% RH,however,no difference(P>0.05) was found in ADFI among the three RH groups at acute moderate 26°C; 35 and 85% RH increased(P<0.05) droppings' corticosterone metabolites at the 2,6,8 and 22 h and decreased(P<0.05) ADFI compared to the 60% RH,moreover,85% RH further increased(P<0.05) droppings' corticosterone metabolites and further decreased(P<0.05) ADFI compared to the 35% RH at acute moderate 31°C; and the average of droppings' corticosterone metabolites in the whole period had a negative correlation(P<0.02) with the ADFI.2) In experiment 2,85% RH increased(P<0.01) droppings' corticosterone metabolites only at the 2 h and decreased(P<0.02) ADFI and average daily gain(ADG) compared to the 60% RH,no difference(P>0.05) in droppings' corticosterone metabolites was found between the 35 and 60% RH,however,35% RH decreased(P<0.01) ADG compared to the 60% RH,and the average of droppings' corticosterone metabolites in the whole period also had a negative correlation(P<0.02) with ADFI and ADG.In conclusion,droppings' corticosterone metabolites could be used as a RH stress index and low and high RH,especially high RH,reduced growth performance possibly through inducing RH stress at moderate temperature.
文摘<span style="font-family:Verdana;">The</span><span><span style="font-family:Verdana;"> use of organic manures, constitute an alternative to that of polluting artificial fertilizers. In this study, the effect of various levels of hen droppings fertilization on the production of biomass, chemical composition and carrying capacity of </span><i><i><span style="font-family:Verdana;">P</span></i><span><span style="font-family:Verdana;">. </span><i><span style="font-family:Verdana;">clandestinum</span></i><span style="font-family:Verdana;"></span></span></i> </span><span style="font-family:Verdana;">were evaluated at the Research and Experimental Farm (REF) and at the Animal Nutrition and Feeding Laboratory of </span><span style="font-family:Verdana;">the University of Dschang, between April and September 2016. A completely randomized block design comparing three nitrogen level of fertilization in hen droppings form (0;100 and 200 kg N/ha) on 4 m</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> plot of </span><span style="font-family:Verdana;"><i></i></span><i><i><span style="font-family:Verdana;">P</span></i><span><span style="font-family:Verdana;">. </span><i><span style="font-family:Verdana;">clandestinum</span></i><span style="font-family:Verdana;"></span></span></i><span style="font-family:Verdana;"> were used. Each treatment was carried out in four replications for a total of 12 experimental plots. Then a sample of 500 g of forage has been collected in the center of each plot, then dried and used for the evaluation of the biomass and the</span><span><span style="font-family:Verdana;"> chemical composition of <i></i></span><i><i><span style="font-family:Verdana;">P</span></i><span><span style="font-family:Verdana;">. </span><i><span style="font-family:Verdana;">clandestinum</span></i><span style="font-family:Verdana;"></span></span></i>, </span><span style="font-family:Verdana;">according to the level of fertilization and the cutting frequency. The results showed that the fertilization with the hen droppings positively influenced (p < 0.05) regenera</span><span style="font-family:Verdana;">tion at the first cutting frequency and the highest value (47.12 cm) was obtained with of 200 kg N/ha rate of fertilization. The biomass of this fodder increased significantly (p < 0.05) with the level of fertilization with hen droppings. Besides, it decrease</span><span style="font-family:Verdana;">s</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> with the increasing cutting of frequency whatever the level of fertilization. Independently of the fertilization and the cutting frequency, the maximum biomass (6.22 t DM/ha) was obtained with the first cutting at the 200 kg N/ha of hen droppings fertilization. The fertilization influenced in variable way the chemical composition of </span><span style="font-family:Verdana;"><i></i></span><i><i><span style="font-family:Verdana;">P</span></i><span><span style="font-family:Verdana;">. </span><i><span style="font-family:Verdana;">clandestinum</span></i><span style="font-family:Verdana;"></span></span></i></span><span style="font-family:Verdana;">. The dry matter and organic matter content decrease with the level of fertilization and the highest values (83.79% and 89.39% respectively for the DM and OM) were obtained on the control plot at the third and the first cutting. Moreover, the ash and crude protein contents increased significantly (p < 0.05) with the cutting frequency of cutting and the level of fertilization applied. The highest ash (19.34% DM) and CP (20.04% DM) contents were obtained with of 200 kg N/ha of hen droppings at the second cutting frequency.</span>
文摘Background:Pseudomonas aeruginosa and Acinetobacter baumannii are common nosocomial pathogens in hospital settings.Recently,they have also been found in non-hospital environments,such as poultry farms.While most studies in Ethiopia have focused on these bacteria's antibiotic resistance patterns in hospitals,information regarding their prevalence and resistance in veterinary settings,particularly poultry farms,is limited.This study aimed to assess the prevalence and antibiotic resistance patterns of P.aeruginosa and A.baumannii isolated from chicken droppings on poultry farms.Methods:A cross-sectional study was conducted from March 2022 to June 2022.A total of 87 poultry farms were included in this study,and pooled chicken dropping samples were collected.The samples were subsequently transferred to buffered peptone water and cultured on MacConkey agar.Species of the isolates were identified via routine biochemical tests,including oxidase,catalase,urease,Simon's citrate,sulfide indole motility medium,triple sugar iron agar and growth at temperatures of 37℃ and 42℃.The Kirby–Bauer disk diffusion technique was used for antibiotic susceptibility testing.The data were entered into EpiData version 4.6 and then exported to SPSS version 26 for analysis.Fisher's exact test was used to observe an appropriate association between independent variables and the occurrence of isolates.The results are presented in the text,figures and tables.Results:Among the 87 poultry farms,41(47.1%)were positive for Pseudomonas and Acinetobacter.Among these strains,24(27.6%)P.aeruginosa strains and 13(14.9%)A.baumannii strains were recovered.P.aeruginosa showed complete resistance to tetracycline(24,100.0%)and trimethoprim-sulfamethoxazole(24,100.0%).Additionally,there was a high rate of resistance to ciprofloxacin(13,54.2%)and amikacin(12,50.0%).Similarly,13(100.0%)A.baumannii isolates were resistant to tetracycline,and 12(92.3%)were resistant to trimethoprim-sulfamethoxazole.However,both isolates presented lower resistance rates to piperacillintazobactam(4,9.8%)and cefepime(7,17.1%).Both A.baumannii and P.aeruginosa exhibited multidrug resistance in 10/13(76.9%)and 16/24(66.7%)of the strains,respectively.The overall prevalence of multidrug resistance in this study was 28/41(68.3%).Conclusion:This study demonstrated that poultry farms may be potential reservoirs for P.aeruginosa and A.baumannii,including antibiotic-resistant strains.This is a significant concern to public health because poultry farmers may be contaminated,increasing their dissemination to the community.Therefore,poultry farmers should improve sanitation and reduce the misuse and overuse of antibiotics at poultry farms.
基金supported by National Natural Science Foundation of Chi-na (Grant Nos.40876104 and 41006118)
文摘Lipid biomarkers in AD2 penguin droppings-amend soil core from the Ardley Island,Western Antarctic,were dated using 210Pb.Changes in the fatty acid ratios of nC18:2/nC18:0 from the penguin droppings reflect climate changes coincident with ENNO events during 1931-2006.The occurrence of the minimum values in the depth of 2-3 and 6-7 cm are consistent with the end of ENSO in 1958 and 1983,respectively,reflecting a lag of the biomarker records in AD2 penguin droppings-amend soil in climatic signatures.This study also reveals that the changes in the relative concentration of n-alkanes nC23,the ratios of nC23/nC17 and nC21 /nC22+,and carbon preferential index(CPI) values collectively indicate the variations of soil microor-ganism and lower plant,which are closely related to climate changes.The ratios of bacterial fatty acids iC15:0/aC15:0 reflect the increasing significance of microorganism activities during the two periods that occurred at the end years of ENSO.Decrease in CPIA value and increase in nC21 /nC22+ indicate that low molecular weight fatty acids are derived from microorganism;and their insignificant correlation with Pr/Ph suggests microorganisms play an important role in the relatively simply ecosystem in the Antarctic and are closely linked to climatic conditions.In addition,the observed penguin community indicates the popula-tion of penguin can largely reflect the impacts of global climate changes on the ecosystem.
基金supported by the 'Zhu Cheng Professorial Workstation of China Agricultural University',and the Science and Technology Cooperation Project between China and the United Kingdom under the National Key Research and Development Program(Envirobot an Autonomous Roving Platform for Environment,Health,and Welfare Monitoring of Poultry(Grant No.2017YFE0122200).
文摘The characteristics of chicken droppings are closely related to the health of chickens.Veterinarians often judge the health of a chicken by looking at whether the chicken poop is normal.At present,the inspection of abnormal chicken droppings in chicken coops relies on manual observation,which is inefficient,accurate varies from person to person,labor-intensive,and has the risk of cross-infection.To achieve efficient,accurate,and intelligent identification of abnormal chicken droppings,an abnormal chicken droppings detection method based on improved Faster Region-based Convolutional Neural Network(Faster R-CNN)was proposed in this study.In the feature extraction network stage,deformable convolution was used and combined with Path Augmentation-Feature Pyramid Network(PA-FPN)to improve the extraction ability of features at different scales.In the Region Proposal Network(RPN)stage,the K-means++algorithm was used to cluster the dataset and obtain the Anchor-ratio which is more suitable for the chicken poop object,and the FocalLoss classification loss function was used to improve the classification ability of difficult samples.In the regional convolutional network stage,the region of interest calibration algorithm was used instead to obtain more accurate localization information.The experimental results show that the improved Faster R-CNN structure can reach an accuracy of 98.8%for abnormal chicken poop detection,and the average accuracy mean value was improved by 27.8%.The results can provide a key core technology support for establishing an efficient abnormal chicken droppings online detection system.
基金financially supported by the National Natural Science Foundation of China (No.52372188)Natural Science Foundation of Henan (Nos.242300421625,252300421333)+4 种基金CAS Henan Industrial Technology Innovation & Incubation Center (No.2024121)Key Scientific Research Project of Education Department of Henan Province (Nos.22A150042,23A150038,and 24A150019)2023 Introduction of studying abroad talent programthe China Postdoctoral Science Foundation (No.2019 M652546)Key Project of Science and Technology of Henan Province (No.252102240007)。
文摘Aqueous zinc-ion batteries(AZIBs) are regarded as one of the most promising energy conversion and storage devices.Nevertheless,side reactions and dendrite growth on the zinc metal anode hinder their widespread application.In this study,hemin was employed as a multi-functional artificial interface for the first time to inhibit the disordered growth of zinc dendrites and mitigate side reactions.Theoretical calculations indicate that hemin is preferentially adsorbed onto the zinc anode,thus blocking the interaction between the active zinc anode and electrolyte.Compared with zinc foil,the Hemin@Zn anode demonstrates enhanced corrosion resistance,a decrease in hydrogen evolution,and more orderly deposition of zinc.As expected,the symmetric cell with Hemin@Zn anode can sustain up to 4000 h at 0.2 mA/cm^(2),0.2 mAh/cm^(2).Asymmetric Zn//Cu cells exhibit an average coulombic efficiency exceeding 99.72 % during 500 cycles.Moreover,the full cell Hemin@Zn//NH_(4)V_(4)O_(10) delivers a superior capacity up to 367 m Ah/g and the discharge capacity retention reaches 124 mAh/g after 1200 cycles even at a current density of 5 A/g.This work provides a simple and effective method for constructing a robust artificial interface to promote the application of long-life AZIBs.
基金supported by the National Natural Science Foundation of China(52475105)Special Fund for Science and Technology Innovation of Jiangsu Province(BE2022610)National Natural Science Foundation of China(U23A20661).
文摘Predicting the precise impacts of climate change on extreme winds remains challenging,yet strong storms are widely expected to occur more frequently in a warming climate.Wind barriers are commonly used on bridges to reduce aerodynamic loads on trains through blocking effects.This study develops a novel wind barrier based on Tesla valves,which not only blocks incoming flow but also dissipates mechanical energy through fluid collision.To demonstrate this energy-dissipation capability,a Tesla plate is placed in a circular duct to examine its influence on pressure drop.Experimental tests and numerical simulations comparing a Tesla channel and a straight channel of equal porosity show that the Tesla configuration produces a substantially higher pressure drop.Validated simulations are then used to conduct a parametric study to optimize the design.By varying the channel ratio,diversion angle,number of dissipation units,and porosity,velocity–pressure-drop relationships for different Tesla plates are obtained.The results show that larger channel ratios,larger diversion angles,and more dissipation units,combined with lower porosity,all increase pressure drop and thus enhance energy dissipation.Finally,the aerodynamic coefficients of a high-speed train on a bridge deck equipped with a Tesla-type barrier are evaluated and compared with those for a traditional straight-channel barrier.The Tesla-type barrier reduces the train’s lateral force coefficient to only 15%–25%of that produced by the traditional barrier,and it generates an additional stabilizing force that further improves running safety.
文摘Heat exchangers play a crucial role in thermal energy systems,with their performance directly impacting efficiency,cost,and environmental impact.Apowerful technique for performance improvement can be given by passive enhancement strategies,which are characterized by their dependability and minimal external power requirements.This comprehensive review critically assesses recent advancements in such passive methods to evaluate their heat transfer mechanisms,performance characteristics,and practical implementation challenges.Our methodology involves a systematic and comprehensive analysis of various heat transfer enhancement techniques,including surface modifications,extended surfaces,swirl flow devices,and tube inserts.This approach synthesizes and integrates findings from a broad spectrum of experimental investigations and numerical simulations to establish a cohesive understanding of their performance characteristics and underlyingmechanisms.Based on the findings,passive heat transfer techniques result in significant improvements in thermal performance;for instance,corrugated and roughened surfaces increase the heat transfer coefficient by 50%–200%,and advanced insert geometries,such as modified twisted tapes,can increase it by more than 300%,typically accompanied by significant pressure-drop penalties.However,an important finding is the general trade-off between enhanced heat transfer and higher frictional loss,which requires optimization depending on the applications.Finally,this review also provides recommendations that will document the gaps of various passive techniques in heat exchangers to future address.
文摘Coiled tube heat exchangers are widely preferred in shell structures due to their superior heat transfer performance,driven by favorable flow characteristics.This study investigates the effect of modifying coil and shell configurations on heat transfer efficiency.Two key enhancements were examined:adding fins to the outer coil surface and integrating longitudinal slots within a hollowed shell.These modifications promote turbulence and extend heat transfer duration,thereby improving performance.However,they also introduce challenges,including increased pressure loss andmanufacturing complexity.Numerical simulationswere conducted usingANSYS Fluent 2024R1 under identical boundary conditions.With a fixed cold-side flow rate of 3 L/min,the input temperatures for the hot and cold fluids were 333.15 and 291.65 K,respectively.The hot-side flow rate varied between 2 and 6 L/min.Simulation outcomes were reported for the objectives of the study that included the improvement in heat exchangers’heat transfer enhancement.As it was indicated in the study outcomes,the average heat transfer rate increased by 15.56%,the overall heat transfer coefficient enhanced by about 29.51%,and the convective heat transfer coefficient improved by about 75.96%compared to the conventional shell-and-coil tube heat exchanger model.However,the modified technique resulted in a significant pressure drop.
基金supported by the National Key Research and Development Program of China(Grant Nos.2021YFA1000200 and 2021YFA1000201)National Natural Science Foundation of China(Grant Nos.12293001 and 12272009)+1 种基金Beijing Natural Science Foundation,China(Grant No.7232050)the Shenzhen Science and Technology Research and Development Grant,China(Grant No.KQTD20180411143400981).
文摘This study examines the hemodynamics of non-Newtonian blood flow in stenosed arteries,focusing on the roles of stenosis severity,guidewire presence,and various non-Newtonian constitutive models.Computational simulations using the generalized power-law,Casson,and Carreau-Yasuda models are conducted for stenosis severities of 50%,70%,80%,and 90%.Results indicate that stenosis severity exerts the greatest influence on pressure and wall shear stress(WSS),with increasing severity leading to higher pressure drops and WSS maxima.Guidewire presence reduces recirculation zone lengths by nearly 60%across different severities and raises the trans-stenotic pressure drop up to 120%.While the choice of constitutive model has minimal impact on hemodynamics within the stenotic region,it becomes crucial in healthy vessels,where non-Newtonian effects are more pronounced.In cases with a guidewire,pressure gradients in the healthy region show up to 18.8%differences between non-Newtonian models.These findings highlight the dominant roles of stenosis severity and guidewire presence in shaping hemodynamics within stenotic regions while emphasizing the need for precise constitutive modeling to capture flow characteristics in healthy vascular segments.
基金the National Natural Science Foundation of China under Grant 52441411,52325402 and 52274057Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project under Grant 2024ZD1004302-04the National Key R&D Program of China under Grant 2023YFB4104200.
文摘This study investigates in-station pressure drop mechanisms in a shale gas gathering system,providing a quantitative basis for flow system optimization.Computational fluid dynamics(CFD)simulations,based on field-measured parameters related to a representative case(a shale gas platform located in Sichuan,China)are conducted to analyze the flow characteristics of specific fittings and manifolds,and to quantify fitting resistance coefficients and manifold inlet interference.The resulting coefficients are integrated into a full-station gathering network model in PipeSim,which,combined with production data,enables evaluation of pressure losses and identification of equivalent pipeline blockages.The results indicate that the resistance coefficients,valid only for fittings under the studied field-specific geometries,are 0.21 for 90◦elbows in the fully open position,0.16 for gate valve passages in the fully open position,and 2.3 for globe valve passages.Manifold interference decreases with lower high-pressure inlet values,whereas inlets farther from the high-pressure side experience stronger disturbances.Interestingly,significant discrepancies between simulated and measured pressure drops reveal partial blockages,corresponding to effective diameter reductions of 65 mm,38 mm,44 mm,38 mm,and 28 mm for Wells 1#,3#,5#,and 6#,respectively.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFF0707601).
文摘The airflow mechanics in adult nasal airways,whether healthy or abnormal,are extensively studied and investigated,but the flow mechanics in child nasal airways remain underexplored.This study investigates the airflow mechanics in the child’s nasal upper airway with adenoid hypertrophy,with an adenoid nasopharyngeal ratio(AN of 0.9),under cyclic inhalation and exhalation.An inlet respiratory cycle with three different flow rates(3.2 L/min calm breathing,8.6 L/min normal breathing,and 19.3 L/min intensive breathing)was simulated by using the computational fluid dynamics approach.To better capture the interaction between airflow and the flexible airway tissue,fluid-structure interaction analysis was performed at the normal breathing rate.Comparing the airflow dynamics during inhalation and exhalation,the pressure drops,nasal resistance,and wall shear stress show significant differences in the nasopharyngeal region for all different flow rates.This observation suggests that the inertial effect associated with the transient flow is important during exhalation and inhalation.Furthermore,the considerable temporal variation in flow rate distribution across a specific cross-section of the nasal airway highlights the critical role of transient data in virtual surgery planning and data for clinical decisions.
文摘Particle-and droplet-laden flows are central to many problems in mechanics and transport.They occur in sedimentladen boundary layers,gas-solid and gas-liquid dispersions,and surface-water films driven by external forcing.They also underpin practical applications ranging from environmental transport to high-speed and aerothermal systems.Despite decades of progress,prediction remains difficult.The physics spans a wide range of scales and often couples turbulence,interphase momentum exchange,collisions,and interfacial transport.Reliable computation therefore requires both robust numerical methodology and careful physical interpretation.
基金support from the Natural Science Foundation of Jiangsu Province(Grant No.BK20242059)the Collaborative Innovation Center for Prevention and Control of Mountain Geological Hazards of Zhejiang Province(PCMGH-2023-02)the opening fund of State Key Laboratory of Coal Mine Disaster Dynamics and Control(2011DA105827-FW202209)are gratefully acknowledged.
文摘The stability and fracture behavior of a goaf roof beneath an open-pit bench are critical concerns,especially under impact loading.However,the effect of the thickness-to-span ratio on dynamic failure modes remains largely unexplored,as existing research focuses mainly on static stability.Energy dissipation and instability evolution under impact loading require further study.To address this gap,this study conducts drop-weight impact experiments on specimens with circular perforations,complemented by numerical simulations.By integrating dimensional analysis,cusp catastrophe theory,and strength reduction techniques,the dynamic instability mechanism of goaf roofs with varying thickness-to-span ratios is revealed.Results show that the thickness-to-span ratio significantly influences energy accumulation and dissipation during roof failure.A higher ratio increases both the magnitude and rate of energy dissipation,particularly during crack initiation and stable propagation,while its impact diminishes in the final failure stage.Optimizing the thickness-to-span ratio within a critical range enhances structural stability,improving the safety factor by up to 83%.However,beyond a certain threshold,additional thickness yields diminishing benefits.This study provides new insights into the energy-based instability mechanism of goaf roofs under impact loads,establishing a theoretical foundation for early warning systems and optimized safety design.
基金Supported by the National Natural Science Foundation of China(Grant No.52078283)Shandong Provincial Natural Science Foundation(Project No.ZR2024MA094)。
文摘With the change of the main influencing factors such as structural configuration and impact conditions,reinforced concrete slabs exhibit different mechanical behaviors with different failure patterns,and the failure modes are transformed.In order to reveal the failure mode and transformation rule of reinforced concrete slabs under impact loads,a dynamic impact response test was carried out using a drop hammer test device.The dynamic data pertaining to the impact force,support reaction force,structural displacement,and reinforcement strain were obtained through the use of digital image correlation technology(DIC),impact force measurement,and strain measurement.The analysis of the ultimate damage state of the reinforced concrete slab identified four distinct types of impact failure modes:local failure by stamping,overall failure by stamping,local-overall coupling failure,and local failure by punching.Additionally,the influence laws of hammerhead shape,hammer height,and reinforcement ratio on the dynamic response and failure mode transformation of the slab were revealed.The results indicate that:(1)The local damage to the slab by the plane hammer is readily apparent,while the overall damage by the spherical hammer is more pronounced.(2)In comparison to the high reinforcement ratio slabs,the overall bending resistance of the low reinforcement ratio slabs is significantly inferior,and the slab back exhibits further cracks.(3)As the hammer height increases,the slab failure mode undergoes a transformation,shifting from local failure by stamping and overall failure by stamping to local-overall coupling failure and local failure by punching.(4)Three failure mode thresholds have been established,and by comparing the peak impact force with the failure thresholds,the failure mode of the slab can be effectively determined.
基金supported by the National Natural Science Foundation of China(12132015,12332015)。
文摘The ratio of the pressure drop force to the drag force,C_(P),is concerned for a non-closely fitting spherical particle settling along the central line in long rectangular tubes with different A_(r)(A_(r)is W/H,where W,H is length of the longer and shorter side of the rectangle respectively).Under Stokes flow conditions,C_(P0)for an infinitely small sphere in long rectangular tubes and C_(P)for a sphere in a long channel between two parallel layered barriers are both calculated.Then C_(P)of a sphere settling in long rectangular tubes are conducted with the direct-forcing fictitious domain(DF/FD)method.At large Reynolds number,the sphere settles unstably with a fluctuating velocity and C_(P).The fluctuation of Cp is much stronger than that of velocity and both fluctuations are stronger for less confined sphere.The influences of the particle Reynolds number(Re_(p))on C_(P)is similar to the existing experimental results in long circular tubes.At low Re_(p),C_(P)is a determined value and is calculated.For a given d/H(d sphere diameter),Cp gets its maximum value at one A_(r)in the range of[1,1.5].For a given A_(r),C_(P)is a quadratic function of d/H similar to that in a circular tube,and parameters of the quadratic function are got by curve fitting from numerical data.The constant term coefficients got have almost no difference with C_(P0)and are furtherly replaced by the latter to get new quadratic coefficients C_(P1).Lastly,an algebraic correlation of C_(P1)to A_(r)is developed.The predictions of Cp are good with a maximum relative error about 1.5%for a sphere with d/H not greater than0.7,compared to numerical results.
基金financially supported by General Scientific Research Project for Higher Education Institutions of Liaoning Provincial Department of Education(Grant No.:LJKMZ20221171)Liaoning Provincial Science and Technology Planning Joint Program(Grant No.:2024-MSLH-580).
文摘Allergic conjunctivitis is a common ocular surface condition.Although corticosteroids are potent antiinflammatory agents for its management,their use is often restricted by potential side effects.Conventional eye drops face challenges such as short retention time and poor corneal permeability,resulting in low drug bioavailability.To overcome these limitations,we developed a preservative-free synthetic high-density lipoprotein(sHDL)nanodisc eye drop containing dexamethasone palmitate.This novel formulation enhances drug stability and extends retention time on the ocular surface.In a mouse model of ovalbumin(OVA)-induced allergic conjunctivitis,the nanodisc eye drop significantly alleviated symptoms while reducing corticosteroid concentration,demonstrating excellent safety and biocompatibility.This innovative approach shows great promise for the treatment of allergic conjunctivitis and may lay the groundwork for new therapeutic strategies in anterior ocular disease management.
基金supported by the Beijing Municipal Science&Technology Commission(Z231100006123010).
文摘With the increasing miniaturization of systems and surging demand for power density,accurate prediction and control of two-phase flow pressure drop have become a core challenge restricting the performance of microchannel heat exchangers.Pressure drop,a critical hydraulic characteristic,serves as both a natural constraint for cooling systems and determines the power required to pump the working fluid through microchannels.This paper reviews the characteristics,prediction models,and optimization measures of two-phase flow pressure drop for low-boiling-point working fluids in microchannels.It systematically analyzes key influencing factors such as fluid physical properties,operating conditions,channel geometry,and flow patterns,and discusses the complex mechanisms of pressure drop under the coupling effect of multi-physical fields.Mainstream prediction models are reviewed:the homogeneous flow model simplifies calculations but shows large deviations at low quality;the separated flow model considers interphase interactions and can be applied to micro-scales after modification;the flow-pattern-based model performs zoned modeling but relies on subjective classification;machine learning improves prediction accuracy but faces the“black-box”problem.In terms of optimization,channel designs are improved through porous structures and micro-rib arrays,and flow rate distribution is optimized using splitters to balance pressure drop and heat transfer performance.This study provides theoretical support for microchannel thermal management in high-power-density devices.
