The global dissemination of antibiotic resistance genes(ARGs),especially via plasmid-mediated horizontal transfer,is becoming a pervasive health threat.While our previous study found that herbicides can accelerate the...The global dissemination of antibiotic resistance genes(ARGs),especially via plasmid-mediated horizontal transfer,is becoming a pervasive health threat.While our previous study found that herbicides can accelerate the horizontal gene transfer(HGT)of ARGs in soil bacteria,the underlying mechanisms by which herbicides promote the HGT of ARGs across and within bacterial genera are still unclear.Here,the underlying mechanism associ-ated with herbicide-promoted HGT was analyzed by detecting intracellular reactive oxygen species(ROS)production,extracellular polymeric substance composition,cell membrane integrity and proton motive force combined with genome-wide RNA sequencing.Exposure to herbicides induced a series of the above bacterial responses to promote HGT except for the ROS response,including compact cell-to-cell contact by enhancing pilus-encoded gene expression and decreasing cell surface charge,increasing cell membrane permeability,and enhancing the proton motive force,providing additional power for DNA uptake.This study provides a mechanistic understanding of the risk of bacterial resistance spread promoted by herbicides,which elucidates a new perspective on nonantibiotic agrochemical acceleration of the HGT of ARGs.展开更多
The current work aims to numerically investigate the impact of using(50%ZnO and 50%Al_(2)O_(3))hybrid nanofluid(HNf)on the performance of convective heat transfer inside a horizontal wavy micro-channel.This issue repr...The current work aims to numerically investigate the impact of using(50%ZnO and 50%Al_(2)O_(3))hybrid nanofluid(HNf)on the performance of convective heat transfer inside a horizontal wavy micro-channel.This issue represents a novel approach that has not been extensively covered in previous research and provides more valuable insights into the performance of HNfs in complex flow geometries.The conjugate heat transfer approach is used to demonstrate the influence of adding hybrid nanoparticles(50%Al_(2)O_(3) and 50%ZnO)to pure water on the rate of heat transfer.The governing equations are numerically solved by using ANSYS FLUENT(2021 R2).The behaviors of convective heat transfer coefficient(HTC),Nusselt number(Nu)and pressure drop are presented under various volume concentrations of(1%,2%and 3%)and Reynolds numbers(Re=600,1200 and 1800).The numerical results are validated against the experimental one,where the validation test shows a good agreement between them.The findings display that the highest HTC enhancement is reached at 59.5%when using a volume concentration of 3%and Re=1800.TheNusselt number is increased with the rise in volume concentration of nanoparticles,where the value of the Nusselt number is improved by 42.25%at 3%volume concentration.The reduction in pressure is raised with an increase in volume concentration and Re.The results also show that the combination of dispersion characteristics,Brownian movement and nanoparticles leads to an improvement in the rate of heat transfer.It is concluded that Nu and the behavior of heat transfer are considerably enhanced when using a hybrid nanofluid inside a wavy micro-channel.展开更多
The activated sludge process is characterized by high microbial density and diversity,both of which facilitate antibiotic resistance gene transfer.Many studies have suggested that antibiotic and non-antibiotic drugs a...The activated sludge process is characterized by high microbial density and diversity,both of which facilitate antibiotic resistance gene transfer.Many studies have suggested that antibiotic and non-antibiotic drugs at sub-inhibitory concentrations are major inducers of conjugative gene transfer.The self-transmissible plasmid pND6-2 is one of the endogenous plasmids harbored in Pseudomonas putida ND6,which can trigger the transfer of another co-occurring naphthalene-degrading plasmid pND6-1.Therefore,to illustrate the potential influence of stimulants on conjugative transfer of pND6-2,we evaluated the effects of four antibiotics (ampicillin,gentamycin,kanamycin,and tetracycline) and naphthalene,on the conjugal transfer efficiency of pND6-2 by filter-mating experiment.Our findings demonstrated that all stimulants within an optimal dose promoted conjugative transfer of pND6-2from Pseudomonas putida GKND6 to P.putida KT2440,with tetracycline being the most effective (100μg/L and 10μg/L),as it enhanced pND6-2-mediated intra-genera transfer by approximately one hundred-fold.Subsequently,seven AS reactors were constructed with the addition of donors and different stimulants to further elucidate the conjugative behavior of pND6-2 in natural environment.The stimulants positively affected the conjugal process of pND6-2,while donors reshaped the host abundance in the sludge.This was likely because stimulant addition enhanced the expression levels of conjugation transfer-related genes.Furthermore,Blastocatella and Chitinimonas were identified as the potential receptors of plasmid pND6-2,which was not affected by donor types.These findings demonstrate the positive role of sub-inhibitory stimulant treatment on pND6-2 conjugal transfer and the function of donors in re-shaping the host spectrum of pND6-2.展开更多
As a new type of environmental pollutant,antibiotic resistance genes(ARGs)pose a huge challenge to global health.Horizontal gene transfer(HGT)represents an important route for the spread of ARGs.The widespread use of ...As a new type of environmental pollutant,antibiotic resistance genes(ARGs)pose a huge challenge to global health.Horizontal gene transfer(HGT)represents an important route for the spread of ARGs.The widespread use of sulfamethazine(SM2)as a broad-spectrum bacteriostatic agent leads to high residual levels in the environment,thereby increasing the spread of ARGs.Therefore,we chose to study the effect of SM2 on the HGT of ARGs mediated by plasmid RP4 from Escherichia coli(E.coli)HB101 to E.coli NK5449 as well as its mechanism of action.The results showed that compared with the control group,SM2 at concentrations of 10 mg/L and 200 mg/L promoted the HGT of ARGs,but transfer frequency decreased at concentrations of 100 mg/L and 500 mg/L.The transfer frequency at 200 mg/L was 3.04×10^(−5),which was 1.34-fold of the control group.The mechanism of SM2 improving conjugation transfer is via enhancement of the mRNA expression of conjugation genes(trbBP,trfAP)and oxidative stress genes,inhibition of the mRNA expression of vertical transfer genes,up regulation of the outer membrane protein genes(ompC,ompA),promotion of the formation of cell pores,and improvement of the permeability of cell membrane to promote the conjugation transfer of plasmid RP4.The results of this study provide theoretical support for studying the spread of ARGs in the environment.展开更多
Temperature-induced cracking during the construction of mass concrete is a significant concern.Numerical simulations of concrete temperature have primarily assumed that the concrete is placed in an open environment.Th...Temperature-induced cracking during the construction of mass concrete is a significant concern.Numerical simulations of concrete temperature have primarily assumed that the concrete is placed in an open environment.The problem of heat transfer between the air and concrete has been simplified to the concrete’s heat dissipation boundary.However,in the case of tubular concrete structures,where air inlet and outlet are relatively limited,the internal air temperature does not dissipate promptly to the external environment as it rises.To accurately simulate the temperature and creep stress in tubular concrete structures with enclosed air spaces during construction,we establish an air–concrete coupled heat transfer model according to the principles of conjugate heat transfer,and the accuracy of the model is verified through experiments.Furthermore,we conduct a case study to analyze the impact of airflow within the ship lock corridor on concrete temperature and creep stress.The results demonstrate that enhancing airflow within the corridor can significantly reduce the maximum concrete temperature.Compared with cases in which airflow within the corridor is neglected,the maximum concrete temperature and maximum tensile stress can be reduced by 12.5℃ and 0.7 MPa,respectively,under a wind speed of 4 m/s.The results of the traditional calculation method are relatively close to those obtained at a wind speed of 1 m/s.However,the temperature reduction process in the traditional method is faster,and the method yields greater tensile stress values for the corridor location.展开更多
In piezoceramic ultrasonic devices,the piezoceramic stacks may fail permanently or function improperly if their working temperatures overstep the Curie temperature of the piezoceramic material.While the end of the hor...In piezoceramic ultrasonic devices,the piezoceramic stacks may fail permanently or function improperly if their working temperatures overstep the Curie temperature of the piezoceramic material.While the end of the horn usually serves near the melting point of the molten metal and is enclosed in an airtight chamber,so that it is difficult to experimentally measure the temperature of the transducer and its variation with time,which bring heavy difficulty to the design of the ultrasonic molten metal treatment system.To find a way out,conjugate heat transfer analysis of an ultrasonic molten metal treatment system is performed with coupled fluid and heat transfer finite element method.In modeling of the system,the RNG model and the SIMPLE algorithm are adopted for turbulence and nonlinear coupling between the momentum equation and the energy equation.Forced air cooling as well as natural air cooling is analyzed to compare the difference of temperature evolution.Numerical results show that,after about 350 s of working time,temperatures in the surface of the ceramic stacks in forced air cooling drop about 7 K compared with that in natural cooling.At 240 s,The molten metal surface emits heat radiation with a maximum rate of about 19 036 W/m2,while the heat insulation disc absorbs heat radiation at a maximum rate of about 7922 W/m2,which indicates the effectiveness of heat insulation of the asbestos pad.Transient heat transfer film coefficient and its distribution,which are difficult to be measured experimentally are also obtained through numerical simulation.At 240 s,the heat transfer film coefficient in the surface of the transducer ranges from–17.86 to 20.17 W/（m2？K）.Compared with the trial and error method based on the test,the proposed research provides a more effective way in the design and analysis of the temperature control of the molten metal treatment system.展开更多
This paper presents a combined finite element method for solving conjugate heat transfer problems where heat conduction in a solid is coupled with heat convection in viscous fluid flow. The streamline upwind finite el...This paper presents a combined finite element method for solving conjugate heat transfer problems where heat conduction in a solid is coupled with heat convection in viscous fluid flow. The streamline upwind finite element method is used for the analysis of thermal viscous flow in the fluid region, whereas the analysis of heat conduction in solid region is performed by the Galerkin method. The method uses the three-node triangular element with equal-order interpolation functions for all the variables of the velocity components, the pressure and the temperature. The main advantage of the proposed method is to consistently couple heat transfer along the fluid-solid interface. Three test cases, i.e. conjugate Couette flow problem in parallel plate channel, counter-flow in heat exchanger, and conjugate natural convection in a square cavity with a conducting wall, are selected to evaluate the efficiency of the present method.展开更多
The accurate simulation of boundary layer transition process plays a very important role in the prediction of turbine blade temperature field. Based on the Abu-Ghannam and Shaw （AGS） and c-Re h transition models, a ...The accurate simulation of boundary layer transition process plays a very important role in the prediction of turbine blade temperature field. Based on the Abu-Ghannam and Shaw （AGS） and c-Re h transition models, a 3D conjugate heat transfer solver is developed, where the fluid domain is discretized by multi-block structured grids, and the solid domain is discretized by unstructured grids. At the unmatched fluid/solid interface, the shape function interpolation method is adopted to ensure the conservation of the interfacial heat flux. Then the shear stress transport （SST） model, SST ＆ AGS model and SST ＆ c-Re h model are used to investigate the flow and heat transfer characteristics of Mark II turbine vane. The results indicate that compared with the full turbulence model （SST model）, the transition models could improve the prediction accuracy of temperature and heat transfer coefficient at the laminar zone near the blade leading edge. Compared with the AGS transition model, the c-Re h model could predict the transition onset location induced by shock/boundary layer interaction more accurately, and the prediction accuracy of temperature field could be greatly improved.展开更多
A better understanding of two-phase flows with evaporation allows leading to an optimal design of evaporators. For that purpose, numerical simulations are very useful. In this paper, a numerical study has been carried...A better understanding of two-phase flows with evaporation allows leading to an optimal design of evaporators. For that purpose, numerical simulations are very useful. In this paper, a numerical study has been carried out in order to model and simulate the combination of a two-phase flow with evaporation in a vertical tube. The VOF （volume-of-fluid） multiphase flow method and a phase-change model for the mass transfer have been used. For an accurate modeling, the effect of axial conduction has been also taken into account using a conjugate heat transfer model. Since thermal oscillations are undesirable as they can lead to the failure of the tube, flow instabilities have also been analyzed, using FFT （fast Fourier transforms）, in order to comprehend their behavior and influence. A control study of the flow instabilities in the tube is also presented. For that purpose tube inlet temperature has been varied using a gain control parameter.展开更多
Numerical simulation on conjugate heat transfer of an internal cooled turbine vane was carried out. Numerical techniques employed included the third-order accuracy TVD scheme, multi-block structured grids and the tech...Numerical simulation on conjugate heat transfer of an internal cooled turbine vane was carried out. Numerical techniques employed included the third-order accuracy TVD scheme, multi-block structured grids and the technique of arbitrary curved mesh. Comparison between results of commercial CFD codes with several turbulence models and those of this code shows that it is incorrect of commercial CFD codes to predict the thermal boundary layer with traditional turbulence models, and that turbulence models considering transition lead to more accurate heat transfer in thermal boundary layer with some reliability and deficiency yet. The results of this code are close to those of CFX with transition model.展开更多
The boiling heat transfer technology with cavity surfaces can provide higher heat flux under lower wall superheat,which is of great significance for the cooling of electronic chips and microelectromechanical devices.I...The boiling heat transfer technology with cavity surfaces can provide higher heat flux under lower wall superheat,which is of great significance for the cooling of electronic chips and microelectromechanical devices.In this paper,the boiling characteristics of the cavity surfaces are investigated based on the lattice Boltzmann(LB)method,focusing on the effects of cavity shapes,sizes,and heater thermal conductivity on the heat transfer performance.The results show that the triangular cavity has the best boiling performance since it has less residual vapor and higher bubble departure frequency than those of the trapezoidal and rectangular cavities.As the cavity size increases,the enhancement of heat transfer by the cavity mouth is suppressed by the heat accumulation effect at the heater bottom.The liquid rewetting process during bubble departure is the reason for the fluctuation of the space-averaged heat flux,and the heater thermal conductivity determines the fluctuation amplitude.The evaporation of liquid in the cavity with high thermal conductivity walls is more intense,resulting in shorter waiting time and higher bubble departure frequency.展开更多
This paper studied a certain blade with ten radial cooling holes which employed conjugate heat transfer method. The cooling air entered the cooling channel from the bottom of the blade and went out from the top, it wa...This paper studied a certain blade with ten radial cooling holes which employed conjugate heat transfer method. The cooling air entered the cooling channel from the bottom of the blade and went out from the top, it was not ejected into the main flow. This paper used different numerical conditions including different turbulence models,turbulence intensities,thermal conduction coefficients and the influence on fluid property via temperature variation. The temperature distribution and pressure distribution of the blade were compared with experimental data. The results show that the numerical results using different turbulence models are almost identical to experimental data even little deviation occurs at shock wave location. The trends of temperature distribution under different numerical conditions are coincident to experimental data,especially Reynolds stress turbulence model. It can be concluded that anisotropic turbulence models can simulate the transition from laminar to turbulence,and the influence of turbulence intensity on laminar region and transition region is more than that on developed turbulent region.展开更多
Concerning the specific demand on solving the long-term conjugate heat transfer （CHT） problem, a new algorithm of the global tightly-coupled transient heat transfer based on the quasi-steady flow field is further pu...Concerning the specific demand on solving the long-term conjugate heat transfer （CHT） problem, a new algorithm of the global tightly-coupled transient heat transfer based on the quasi-steady flow field is further put forward. Compared to the traditional loosely-coupled algorithm, the computational efficiency is further improved with the greatly reduced update frequency of the flow field, and moreover the update step of the flow field can be reasonably determined by using the engineering empirical formula of the Nusselt number based on the changes of the inlet and outlet boundary conditions. Taking a duct heated by inner forced air flow heating process as an example, the comparing results to the tightly-coupled transient calculation by Fluent software shows that the new algorithm can significantly improve the computational efficiency with a reasonable accuracy on the transient temperature distribution, such as the computing time is reduced to 22,8% and 40% while the duct wall temperature deviation are 7% and 5% respectively using two flow update time step of 100 s and 50 s on the variable inlet-flow rate conditions.展开更多
In this paper, a 3D model of a flat circuit board with a heat generating electronic chip mounted on it has been studied numerically. The conjugate heat transfer including the conduction in the chip and convection with...In this paper, a 3D model of a flat circuit board with a heat generating electronic chip mounted on it has been studied numerically. The conjugate heat transfer including the conduction in the chip and convection with the surrounding fluid has been investigated numerically. Computational fluid dynamics using the finite volume method has been used for modeling the conjugate heat transfer through the chip and the circuit board. Conjugate heat transfer has broad applications in engineering and industrial applications in design of cooling off electronic components. Effects of various inlet velocities have been studied on the heat transfer variation and temperature of the circuit board. Numerical results show that the temperature of the chip reduces as the velocity of the inlet fluid flow increases.展开更多
Effectively controlling the deformation and temperature of heated structures is crucial for achieving highperformance active cooling through fluid flow.In this study,the topology optimization design of structures cons...Effectively controlling the deformation and temperature of heated structures is crucial for achieving highperformance active cooling through fluid flow.In this study,the topology optimization design of structures considering fluid–structure interactions and heat transfer performance was investigated,and then optimized designs of two-dimensional/three-dimensional cooling impingement systems obtained using the proposed method were obtained.In the optimization model,the objective function was constructed as a weighted combination of the mechanical deformations at specific locations and the average temperature within the designated solid channel structures.Additionally,explicit functional interpolation models were introduced to establish connections between the thermal,fluid,and solid properties,along with the element densities.In the analysis model,the strongly coupled structural mechanical deformation and fluid velocity field were analyzed via a dynamicgrid-based finite element model with a Winslow elliptic smoother to automatically track the fluid–structure interface during the process of optimization.To solve the optimization problems,the globally convergent moving asymptotic optimizer method was used to adjust the design variables on the basis of the sensitivity analysis.A demonstration of the efficacy of the proposed algorithm is provided through the presentation of several optimization examples.Furthermore,two-and three-dimensional cooling impingement systems were designed with the proposed method.展开更多
Soil microbial fuel cells(MFCs),a novel ecosystem technology,have recently been intensively studied for antibiotic-polluted soils.However,actual agricultural soils are always contaminated by mixed pollutants,especiall...Soil microbial fuel cells(MFCs),a novel ecosystem technology,have recently been intensively studied for antibiotic-polluted soils.However,actual agricultural soils are always contaminated by mixed pollutants,especially plasticizers from extensively used agricultural plastic films.The aim of this study was to investigate the effects of di-2-ethylhexyl phthalate(DEHP),a representative plasticizer in soil,on the removal of sulfadiazine(SDZ),a frequently detected antibiotic in natural environments,and antibiotic resistance genes(ARGs)and microbial community in soil MFCs.Soil MFCs maintained a good antibiotic removal ability even under the influence of residual DEHP and achieved a higher removal performance at higher DEHP concentrations due to enhanced power generation.Specifically,a higher DEHP concentration had a favorable effect on antibiotic removal in soil MFCs,with the SDZ concentration decreased in both the upper and lower layers(from 4.867±0.221 to 0.268±0.021 and 0.293±0.047 mg kg^(-1),respectively)of polluted soils.Moreover,a high DEHP concentration significantly promoted the abundance of bacteria associated with electricity generation compared with a lower DEHP concentration,resulting in the promotion of extracellular electron transfer and enhancing SDZ degradation.The increased ARG abundance may be caused by the enrichment of ARG potential hosts brought about by high DEHP concentration,likely due to the increased conjugative transfer frequencies of plasmid RP4 by decreasing cell membrane permeability and increasing reactive oxygen species content.The results revealed the ecological risk of residual DEHP in soil that promotes ARG transmission in soil MFCs,although it has the potential to reduce SDZ toxicity through horizontal gene transfer.We also highlight concerns regarding the management of antibiotics and plasticizers in soil.The negative effects of plasticizers on antibiotic removal should be carefully evaluated when using soil MFCs for the in-situ remediation of antibiotic-contaminated soil.展开更多
To study the seepage and deformation characteristics of coal at high temperatures,coal samples from six different regions were selected and subjected to computed tomography(CT)scanning studies.In conjunction with ANSY...To study the seepage and deformation characteristics of coal at high temperatures,coal samples from six different regions were selected and subjected to computed tomography(CT)scanning studies.In conjunction with ANSYS software,3 D reconstruction of CT images was used for the establishment of fluidsolid conjugate heat transfer model and coal thermal deformation model based on the microstructures of coal.In addition,the structure of coal was studied in 2 D and 3 D perspectives,followed by the analysis of seepage and deformation characteristics of coal at high temperatures.The results of this study indicated that porosity positively correlated with the fractal dimension,and the connectivity and seepage performances were roughly identical from 2 D and 3 D perspectives.As the porosity increased,the fractal dimension of coal samples became larger and the pore-fracture structures became more complex.As a result,the permeability of coal samples decreased.In the meantime,fluid was fully heated,generating high-temperature water at outlet.However,when the porosity was low,the outlet temperature was very high.The average deformation of coal skeleton with different pore-fracture structures at high temperatures showed a trend of initial increase and subsequent decrease with the increase of porosity and fractal dimension.The maximum deformation of coal skeleton positively correlated with connectivity but negatively correlated with the fractal dimension.展开更多
Attempts for higher output power and thermal efficiency of gas turbines make the inlet temperature of turbine to be far beyond the material melting temperature.Therefore,to protect the airfoil in gas turbine from hot ...Attempts for higher output power and thermal efficiency of gas turbines make the inlet temperature of turbine to be far beyond the material melting temperature.Therefore,to protect the airfoil in gas turbine from hot gas and eventually prolong the lifetime of the blade,internal and film cooling structures with better thermal performance and cooling effectiveness are urgently needed.However,the traditional way of proceeding involves numerous simulations,additional experiments,and separate trials.Optimization of turbine cooling structures is an effective way to achieve better structures with higher overall performances while considering the multiple objectives,disciplines or subsystems.In this context,this paper reviews optimization research works on film cooling structures and internal cooling structures in gas turbines by means of various optimization methods.This review covers the following aspects:(A)optimization of film cooling conducted on flat plates and on turbine blades or vanes;(B)optimization of jet impingement cooling structures;(C)optimization of rib shapes,dimple shapes,pin–fin arrays in the cooling channels;(D)optimization of U-bend shaped cooling channels,and internal cooling systems of turbine blades or vanes.The review shows that through a reliable and accurate optimization procedure combined with conjugate heat transfer analysis,higher overall thermal performance can be acquired for single-objective or multi-objectives balanced by other constrained conditions.Future ways forward are pointed out in this review.展开更多
To study the temperature distribution and thermal-stress field in different service stages, a two-dimensional model of a turbine blade with thermal barrier coatings is developed, in which the conjugate heat transfer a...To study the temperature distribution and thermal-stress field in different service stages, a two-dimensional model of a turbine blade with thermal barrier coatings is developed, in which the conjugate heat transfer analysis and the decoupled thermal-stress calculation method are adopted. Based on the simulation results, it is found that a non-uniform distribution of temperature appears in different positions of the blade surface, which has directly impacted on stress field. The maximum temperature with a value of 1030 ℃ occurs at the leading edge. During the steady stage, the maximum stress of thermally grown oxide （TGO） appears in the middle of the suction side, reaching 3.75 GPa. At the end stage of cooling, the maximum compressive stress of TGO with a value of-3.5 GPa occurs at the leading edge. Thus, it can be predicted that during the steady stage the dangerous regions may locate at the suction side, while the leadine edge mav be more Drone to failure on cooling.展开更多
Focusing on the design problem of high-performance radiators for planar motors in the wafer stage of the lithography machine,a thermal-fluid coupling optimization scheme based on parametric solid components was propos...Focusing on the design problem of high-performance radiators for planar motors in the wafer stage of the lithography machine,a thermal-fluid coupling optimization scheme based on parametric solid components was proposed.The mapping method between component parameters and pseudo-density values was established.An analytical solution for the sensitivity of pseudo-density to component parameters was given.The conjugate heat transfer function with the shallow channel approximation term was solved through the pseudo-density information.In the optimization example,circular components were selected,and the position and the size of solid components were chosen as design variables.In order to eliminate calculation errors caused by pseudo-density,an optimized pseudo-density field was converted into the result based on parametric components.Compared to the reference motor radiator,the average surface temperature rise of the optimized water-cooling motor radiator is reduced by 22.4%,which verifies the feasibility and effectiveness of the proposed method.展开更多
基金This work was supported by the National Natural Science Foundation of China(31972521)the Fujian Agriculture and Forest University Program for Distinguished Young Scholar(No.XJQ2017001).
文摘The global dissemination of antibiotic resistance genes(ARGs),especially via plasmid-mediated horizontal transfer,is becoming a pervasive health threat.While our previous study found that herbicides can accelerate the horizontal gene transfer(HGT)of ARGs in soil bacteria,the underlying mechanisms by which herbicides promote the HGT of ARGs across and within bacterial genera are still unclear.Here,the underlying mechanism associ-ated with herbicide-promoted HGT was analyzed by detecting intracellular reactive oxygen species(ROS)production,extracellular polymeric substance composition,cell membrane integrity and proton motive force combined with genome-wide RNA sequencing.Exposure to herbicides induced a series of the above bacterial responses to promote HGT except for the ROS response,including compact cell-to-cell contact by enhancing pilus-encoded gene expression and decreasing cell surface charge,increasing cell membrane permeability,and enhancing the proton motive force,providing additional power for DNA uptake.This study provides a mechanistic understanding of the risk of bacterial resistance spread promoted by herbicides,which elucidates a new perspective on nonantibiotic agrochemical acceleration of the HGT of ARGs.
文摘The current work aims to numerically investigate the impact of using(50%ZnO and 50%Al_(2)O_(3))hybrid nanofluid(HNf)on the performance of convective heat transfer inside a horizontal wavy micro-channel.This issue represents a novel approach that has not been extensively covered in previous research and provides more valuable insights into the performance of HNfs in complex flow geometries.The conjugate heat transfer approach is used to demonstrate the influence of adding hybrid nanoparticles(50%Al_(2)O_(3) and 50%ZnO)to pure water on the rate of heat transfer.The governing equations are numerically solved by using ANSYS FLUENT(2021 R2).The behaviors of convective heat transfer coefficient(HTC),Nusselt number(Nu)and pressure drop are presented under various volume concentrations of(1%,2%and 3%)and Reynolds numbers(Re=600,1200 and 1800).The numerical results are validated against the experimental one,where the validation test shows a good agreement between them.The findings display that the highest HTC enhancement is reached at 59.5%when using a volume concentration of 3%and Re=1800.TheNusselt number is increased with the rise in volume concentration of nanoparticles,where the value of the Nusselt number is improved by 42.25%at 3%volume concentration.The reduction in pressure is raised with an increase in volume concentration and Re.The results also show that the combination of dispersion characteristics,Brownian movement and nanoparticles leads to an improvement in the rate of heat transfer.It is concluded that Nu and the behavior of heat transfer are considerably enhanced when using a hybrid nanofluid inside a wavy micro-channel.
基金supported by the National Natural Science Foundation of China(No. 31670512)Natural Science Basic Research Plan in Shaanxi Province of China(No. 2018JM3039)。
文摘The activated sludge process is characterized by high microbial density and diversity,both of which facilitate antibiotic resistance gene transfer.Many studies have suggested that antibiotic and non-antibiotic drugs at sub-inhibitory concentrations are major inducers of conjugative gene transfer.The self-transmissible plasmid pND6-2 is one of the endogenous plasmids harbored in Pseudomonas putida ND6,which can trigger the transfer of another co-occurring naphthalene-degrading plasmid pND6-1.Therefore,to illustrate the potential influence of stimulants on conjugative transfer of pND6-2,we evaluated the effects of four antibiotics (ampicillin,gentamycin,kanamycin,and tetracycline) and naphthalene,on the conjugal transfer efficiency of pND6-2 by filter-mating experiment.Our findings demonstrated that all stimulants within an optimal dose promoted conjugative transfer of pND6-2from Pseudomonas putida GKND6 to P.putida KT2440,with tetracycline being the most effective (100μg/L and 10μg/L),as it enhanced pND6-2-mediated intra-genera transfer by approximately one hundred-fold.Subsequently,seven AS reactors were constructed with the addition of donors and different stimulants to further elucidate the conjugative behavior of pND6-2 in natural environment.The stimulants positively affected the conjugal process of pND6-2,while donors reshaped the host abundance in the sludge.This was likely because stimulant addition enhanced the expression levels of conjugation transfer-related genes.Furthermore,Blastocatella and Chitinimonas were identified as the potential receptors of plasmid pND6-2,which was not affected by donor types.These findings demonstrate the positive role of sub-inhibitory stimulant treatment on pND6-2 conjugal transfer and the function of donors in re-shaping the host spectrum of pND6-2.
基金supported by the National Natural Science Foundation of China(No.41671320)the Natural Science Foundation of Shandong Province,China(No.ZR2016JL029)and the Special Funds of Taishan Scholar of Shandong Province,China.
文摘As a new type of environmental pollutant,antibiotic resistance genes(ARGs)pose a huge challenge to global health.Horizontal gene transfer(HGT)represents an important route for the spread of ARGs.The widespread use of sulfamethazine(SM2)as a broad-spectrum bacteriostatic agent leads to high residual levels in the environment,thereby increasing the spread of ARGs.Therefore,we chose to study the effect of SM2 on the HGT of ARGs mediated by plasmid RP4 from Escherichia coli(E.coli)HB101 to E.coli NK5449 as well as its mechanism of action.The results showed that compared with the control group,SM2 at concentrations of 10 mg/L and 200 mg/L promoted the HGT of ARGs,but transfer frequency decreased at concentrations of 100 mg/L and 500 mg/L.The transfer frequency at 200 mg/L was 3.04×10^(−5),which was 1.34-fold of the control group.The mechanism of SM2 improving conjugation transfer is via enhancement of the mRNA expression of conjugation genes(trbBP,trfAP)and oxidative stress genes,inhibition of the mRNA expression of vertical transfer genes,up regulation of the outer membrane protein genes(ompC,ompA),promotion of the formation of cell pores,and improvement of the permeability of cell membrane to promote the conjugation transfer of plasmid RP4.The results of this study provide theoretical support for studying the spread of ARGs in the environment.
基金This work was supported by Construction Simulation and Support Optimization of Hydraulic Tunnel Based on Bonded Block-Synthetic Rock Mass Method and Hubei Province Postdoctoral Innovative Practice Position.
文摘Temperature-induced cracking during the construction of mass concrete is a significant concern.Numerical simulations of concrete temperature have primarily assumed that the concrete is placed in an open environment.The problem of heat transfer between the air and concrete has been simplified to the concrete’s heat dissipation boundary.However,in the case of tubular concrete structures,where air inlet and outlet are relatively limited,the internal air temperature does not dissipate promptly to the external environment as it rises.To accurately simulate the temperature and creep stress in tubular concrete structures with enclosed air spaces during construction,we establish an air–concrete coupled heat transfer model according to the principles of conjugate heat transfer,and the accuracy of the model is verified through experiments.Furthermore,we conduct a case study to analyze the impact of airflow within the ship lock corridor on concrete temperature and creep stress.The results demonstrate that enhancing airflow within the corridor can significantly reduce the maximum concrete temperature.Compared with cases in which airflow within the corridor is neglected,the maximum concrete temperature and maximum tensile stress can be reduced by 12.5℃ and 0.7 MPa,respectively,under a wind speed of 4 m/s.The results of the traditional calculation method are relatively close to those obtained at a wind speed of 1 m/s.However,the temperature reduction process in the traditional method is faster,and the method yields greater tensile stress values for the corridor location.
基金Supported by Beijing Municipal Natural Science Foundation of China(Grant No.3093027)
文摘In piezoceramic ultrasonic devices,the piezoceramic stacks may fail permanently or function improperly if their working temperatures overstep the Curie temperature of the piezoceramic material.While the end of the horn usually serves near the melting point of the molten metal and is enclosed in an airtight chamber,so that it is difficult to experimentally measure the temperature of the transducer and its variation with time,which bring heavy difficulty to the design of the ultrasonic molten metal treatment system.To find a way out,conjugate heat transfer analysis of an ultrasonic molten metal treatment system is performed with coupled fluid and heat transfer finite element method.In modeling of the system,the RNG model and the SIMPLE algorithm are adopted for turbulence and nonlinear coupling between the momentum equation and the energy equation.Forced air cooling as well as natural air cooling is analyzed to compare the difference of temperature evolution.Numerical results show that,after about 350 s of working time,temperatures in the surface of the ceramic stacks in forced air cooling drop about 7 K compared with that in natural cooling.At 240 s,The molten metal surface emits heat radiation with a maximum rate of about 19 036 W/m2,while the heat insulation disc absorbs heat radiation at a maximum rate of about 7922 W/m2,which indicates the effectiveness of heat insulation of the asbestos pad.Transient heat transfer film coefficient and its distribution,which are difficult to be measured experimentally are also obtained through numerical simulation.At 240 s,the heat transfer film coefficient in the surface of the transducer ranges from–17.86 to 20.17 W/（m2？K）.Compared with the trial and error method based on the test,the proposed research provides a more effective way in the design and analysis of the temperature control of the molten metal treatment system.
文摘This paper presents a combined finite element method for solving conjugate heat transfer problems where heat conduction in a solid is coupled with heat convection in viscous fluid flow. The streamline upwind finite element method is used for the analysis of thermal viscous flow in the fluid region, whereas the analysis of heat conduction in solid region is performed by the Galerkin method. The method uses the three-node triangular element with equal-order interpolation functions for all the variables of the velocity components, the pressure and the temperature. The main advantage of the proposed method is to consistently couple heat transfer along the fluid-solid interface. Three test cases, i.e. conjugate Couette flow problem in parallel plate channel, counter-flow in heat exchanger, and conjugate natural convection in a square cavity with a conducting wall, are selected to evaluate the efficiency of the present method.
基金National Natural Science Foundation of China(Grant No.91130013)Innovation Foundation of BUAA for PhD Graduates(YWF-12-RBYJ-010)Specialized Research Fund for the Doctoral Program of Higher Education(20101102110011)for funding this work
文摘The accurate simulation of boundary layer transition process plays a very important role in the prediction of turbine blade temperature field. Based on the Abu-Ghannam and Shaw （AGS） and c-Re h transition models, a 3D conjugate heat transfer solver is developed, where the fluid domain is discretized by multi-block structured grids, and the solid domain is discretized by unstructured grids. At the unmatched fluid/solid interface, the shape function interpolation method is adopted to ensure the conservation of the interfacial heat flux. Then the shear stress transport （SST） model, SST ＆ AGS model and SST ＆ c-Re h model are used to investigate the flow and heat transfer characteristics of Mark II turbine vane. The results indicate that compared with the full turbulence model （SST model）, the transition models could improve the prediction accuracy of temperature and heat transfer coefficient at the laminar zone near the blade leading edge. Compared with the AGS transition model, the c-Re h model could predict the transition onset location induced by shock/boundary layer interaction more accurately, and the prediction accuracy of temperature field could be greatly improved.
文摘A better understanding of two-phase flows with evaporation allows leading to an optimal design of evaporators. For that purpose, numerical simulations are very useful. In this paper, a numerical study has been carried out in order to model and simulate the combination of a two-phase flow with evaporation in a vertical tube. The VOF （volume-of-fluid） multiphase flow method and a phase-change model for the mass transfer have been used. For an accurate modeling, the effect of axial conduction has been also taken into account using a conjugate heat transfer model. Since thermal oscillations are undesirable as they can lead to the failure of the tube, flow instabilities have also been analyzed, using FFT （fast Fourier transforms）, in order to comprehend their behavior and influence. A control study of the flow instabilities in the tube is also presented. For that purpose tube inlet temperature has been varied using a gain control parameter.
基金Sponsored by the National Natural Science Foundation of China (Grant No.5047028 and 50476017)
文摘Numerical simulation on conjugate heat transfer of an internal cooled turbine vane was carried out. Numerical techniques employed included the third-order accuracy TVD scheme, multi-block structured grids and the technique of arbitrary curved mesh. Comparison between results of commercial CFD codes with several turbulence models and those of this code shows that it is incorrect of commercial CFD codes to predict the thermal boundary layer with traditional turbulence models, and that turbulence models considering transition lead to more accurate heat transfer in thermal boundary layer with some reliability and deficiency yet. The results of this code are close to those of CFX with transition model.
基金Project supported by the National Natural Science Foundation of China(Nos.11872083,12172017,12202021)。
文摘The boiling heat transfer technology with cavity surfaces can provide higher heat flux under lower wall superheat,which is of great significance for the cooling of electronic chips and microelectromechanical devices.In this paper,the boiling characteristics of the cavity surfaces are investigated based on the lattice Boltzmann(LB)method,focusing on the effects of cavity shapes,sizes,and heater thermal conductivity on the heat transfer performance.The results show that the triangular cavity has the best boiling performance since it has less residual vapor and higher bubble departure frequency than those of the trapezoidal and rectangular cavities.As the cavity size increases,the enhancement of heat transfer by the cavity mouth is suppressed by the heat accumulation effect at the heater bottom.The liquid rewetting process during bubble departure is the reason for the fluctuation of the space-averaged heat flux,and the heater thermal conductivity determines the fluctuation amplitude.The evaporation of liquid in the cavity with high thermal conductivity walls is more intense,resulting in shorter waiting time and higher bubble departure frequency.
基金Sponsored by the National Natural Science Foundation of China( Grant No. 50576017)
文摘This paper studied a certain blade with ten radial cooling holes which employed conjugate heat transfer method. The cooling air entered the cooling channel from the bottom of the blade and went out from the top, it was not ejected into the main flow. This paper used different numerical conditions including different turbulence models,turbulence intensities,thermal conduction coefficients and the influence on fluid property via temperature variation. The temperature distribution and pressure distribution of the blade were compared with experimental data. The results show that the numerical results using different turbulence models are almost identical to experimental data even little deviation occurs at shock wave location. The trends of temperature distribution under different numerical conditions are coincident to experimental data,especially Reynolds stress turbulence model. It can be concluded that anisotropic turbulence models can simulate the transition from laminar to turbulence,and the influence of turbulence intensity on laminar region and transition region is more than that on developed turbulent region.
文摘Concerning the specific demand on solving the long-term conjugate heat transfer （CHT） problem, a new algorithm of the global tightly-coupled transient heat transfer based on the quasi-steady flow field is further put forward. Compared to the traditional loosely-coupled algorithm, the computational efficiency is further improved with the greatly reduced update frequency of the flow field, and moreover the update step of the flow field can be reasonably determined by using the engineering empirical formula of the Nusselt number based on the changes of the inlet and outlet boundary conditions. Taking a duct heated by inner forced air flow heating process as an example, the comparing results to the tightly-coupled transient calculation by Fluent software shows that the new algorithm can significantly improve the computational efficiency with a reasonable accuracy on the transient temperature distribution, such as the computing time is reduced to 22,8% and 40% while the duct wall temperature deviation are 7% and 5% respectively using two flow update time step of 100 s and 50 s on the variable inlet-flow rate conditions.
文摘In this paper, a 3D model of a flat circuit board with a heat generating electronic chip mounted on it has been studied numerically. The conjugate heat transfer including the conduction in the chip and convection with the surrounding fluid has been investigated numerically. Computational fluid dynamics using the finite volume method has been used for modeling the conjugate heat transfer through the chip and the circuit board. Conjugate heat transfer has broad applications in engineering and industrial applications in design of cooling off electronic components. Effects of various inlet velocities have been studied on the heat transfer variation and temperature of the circuit board. Numerical results show that the temperature of the chip reduces as the velocity of the inlet fluid flow increases.
文摘Effectively controlling the deformation and temperature of heated structures is crucial for achieving highperformance active cooling through fluid flow.In this study,the topology optimization design of structures considering fluid–structure interactions and heat transfer performance was investigated,and then optimized designs of two-dimensional/three-dimensional cooling impingement systems obtained using the proposed method were obtained.In the optimization model,the objective function was constructed as a weighted combination of the mechanical deformations at specific locations and the average temperature within the designated solid channel structures.Additionally,explicit functional interpolation models were introduced to establish connections between the thermal,fluid,and solid properties,along with the element densities.In the analysis model,the strongly coupled structural mechanical deformation and fluid velocity field were analyzed via a dynamicgrid-based finite element model with a Winslow elliptic smoother to automatically track the fluid–structure interface during the process of optimization.To solve the optimization problems,the globally convergent moving asymptotic optimizer method was used to adjust the design variables on the basis of the sensitivity analysis.A demonstration of the efficacy of the proposed algorithm is provided through the presentation of several optimization examples.Furthermore,two-and three-dimensional cooling impingement systems were designed with the proposed method.
基金supported by the National Natural Science Foundation of China(Nos.42477014 and 52070101)Huixiang Wang would like to acknowledge the Postgraduate Research Practice Innovation Program of Jiangsu Province,China(No.181200003023218)。
文摘Soil microbial fuel cells(MFCs),a novel ecosystem technology,have recently been intensively studied for antibiotic-polluted soils.However,actual agricultural soils are always contaminated by mixed pollutants,especially plasticizers from extensively used agricultural plastic films.The aim of this study was to investigate the effects of di-2-ethylhexyl phthalate(DEHP),a representative plasticizer in soil,on the removal of sulfadiazine(SDZ),a frequently detected antibiotic in natural environments,and antibiotic resistance genes(ARGs)and microbial community in soil MFCs.Soil MFCs maintained a good antibiotic removal ability even under the influence of residual DEHP and achieved a higher removal performance at higher DEHP concentrations due to enhanced power generation.Specifically,a higher DEHP concentration had a favorable effect on antibiotic removal in soil MFCs,with the SDZ concentration decreased in both the upper and lower layers(from 4.867±0.221 to 0.268±0.021 and 0.293±0.047 mg kg^(-1),respectively)of polluted soils.Moreover,a high DEHP concentration significantly promoted the abundance of bacteria associated with electricity generation compared with a lower DEHP concentration,resulting in the promotion of extracellular electron transfer and enhancing SDZ degradation.The increased ARG abundance may be caused by the enrichment of ARG potential hosts brought about by high DEHP concentration,likely due to the increased conjugative transfer frequencies of plasmid RP4 by decreasing cell membrane permeability and increasing reactive oxygen species content.The results revealed the ecological risk of residual DEHP in soil that promotes ARG transmission in soil MFCs,although it has the potential to reduce SDZ toxicity through horizontal gene transfer.We also highlight concerns regarding the management of antibiotics and plasticizers in soil.The negative effects of plasticizers on antibiotic removal should be carefully evaluated when using soil MFCs for the in-situ remediation of antibiotic-contaminated soil.
基金supported by the National Natural Science Foundation of China(Project Nos.51934004,51674158,51574158,and 51474106)the Major Program of Shandong Province Natural Science Foundation(ZR2018ZA0602)+2 种基金the Taishan Scholar Talent Team Support Plan for Advantaged&Unique Discipline Areasthe Science and technology support plan for Youth Innovation of colleges and universities in Shandong Province(2019KJH006)the special funds for Taishan scholar project(TS20190935)。
文摘To study the seepage and deformation characteristics of coal at high temperatures,coal samples from six different regions were selected and subjected to computed tomography(CT)scanning studies.In conjunction with ANSYS software,3 D reconstruction of CT images was used for the establishment of fluidsolid conjugate heat transfer model and coal thermal deformation model based on the microstructures of coal.In addition,the structure of coal was studied in 2 D and 3 D perspectives,followed by the analysis of seepage and deformation characteristics of coal at high temperatures.The results of this study indicated that porosity positively correlated with the fractal dimension,and the connectivity and seepage performances were roughly identical from 2 D and 3 D perspectives.As the porosity increased,the fractal dimension of coal samples became larger and the pore-fracture structures became more complex.As a result,the permeability of coal samples decreased.In the meantime,fluid was fully heated,generating high-temperature water at outlet.However,when the porosity was low,the outlet temperature was very high.The average deformation of coal skeleton with different pore-fracture structures at high temperatures showed a trend of initial increase and subsequent decrease with the increase of porosity and fractal dimension.The maximum deformation of coal skeleton positively correlated with connectivity but negatively correlated with the fractal dimension.
基金supported by the National Natural Science Foundation of China (No. 51676163)the National 111 Project, China (No. B18041the Guangdong Basic and Applied Basic Research Foundation, China (No. 2019A1515111146)
文摘Attempts for higher output power and thermal efficiency of gas turbines make the inlet temperature of turbine to be far beyond the material melting temperature.Therefore,to protect the airfoil in gas turbine from hot gas and eventually prolong the lifetime of the blade,internal and film cooling structures with better thermal performance and cooling effectiveness are urgently needed.However,the traditional way of proceeding involves numerous simulations,additional experiments,and separate trials.Optimization of turbine cooling structures is an effective way to achieve better structures with higher overall performances while considering the multiple objectives,disciplines or subsystems.In this context,this paper reviews optimization research works on film cooling structures and internal cooling structures in gas turbines by means of various optimization methods.This review covers the following aspects:(A)optimization of film cooling conducted on flat plates and on turbine blades or vanes;(B)optimization of jet impingement cooling structures;(C)optimization of rib shapes,dimple shapes,pin–fin arrays in the cooling channels;(D)optimization of U-bend shaped cooling channels,and internal cooling systems of turbine blades or vanes.The review shows that through a reliable and accurate optimization procedure combined with conjugate heat transfer analysis,higher overall thermal performance can be acquired for single-objective or multi-objectives balanced by other constrained conditions.Future ways forward are pointed out in this review.
基金supported by the National Natural Science Foundation of China(Grant Nos.51172192,11272275 and 11002122)the Natural Science Foundation of Hunan Province(Grant No.11JJ4003)the Doctoral Scientific Research Foundation of Xiangtan University(Grant Nos.KZ08022,KZ03013 and KF20140303)
文摘To study the temperature distribution and thermal-stress field in different service stages, a two-dimensional model of a turbine blade with thermal barrier coatings is developed, in which the conjugate heat transfer analysis and the decoupled thermal-stress calculation method are adopted. Based on the simulation results, it is found that a non-uniform distribution of temperature appears in different positions of the blade surface, which has directly impacted on stress field. The maximum temperature with a value of 1030 ℃ occurs at the leading edge. During the steady stage, the maximum stress of thermally grown oxide （TGO） appears in the middle of the suction side, reaching 3.75 GPa. At the end stage of cooling, the maximum compressive stress of TGO with a value of-3.5 GPa occurs at the leading edge. Thus, it can be predicted that during the steady stage the dangerous regions may locate at the suction side, while the leadine edge mav be more Drone to failure on cooling.
基金Supported by the National Natural Science Foundation of China(51677104)。
文摘Focusing on the design problem of high-performance radiators for planar motors in the wafer stage of the lithography machine,a thermal-fluid coupling optimization scheme based on parametric solid components was proposed.The mapping method between component parameters and pseudo-density values was established.An analytical solution for the sensitivity of pseudo-density to component parameters was given.The conjugate heat transfer function with the shallow channel approximation term was solved through the pseudo-density information.In the optimization example,circular components were selected,and the position and the size of solid components were chosen as design variables.In order to eliminate calculation errors caused by pseudo-density,an optimized pseudo-density field was converted into the result based on parametric components.Compared to the reference motor radiator,the average surface temperature rise of the optimized water-cooling motor radiator is reduced by 22.4%,which verifies the feasibility and effectiveness of the proposed method.
