To study the anti-explosion protection effect of polyurea coating on reinforced concrete box girder,two segmental girder specimens were made at a scale of 1:3,numbered as G(without polyurea coating)and PCG(with polyur...To study the anti-explosion protection effect of polyurea coating on reinforced concrete box girder,two segmental girder specimens were made at a scale of 1:3,numbered as G(without polyurea coating)and PCG(with polyurea coating).The failure characteristics and dynamic responses of the specimens were compared through conducting explosion tests.The reliability of the numerical simulation using LS-DYNA software was verified by the test results.The effects of different scaled distances,reinforcement ratios,concrete strengths,coating thicknesses and ranges of polyurea were studied.The results show that the polyurea coating can effectively enhance the anti-explosion performance of the girder.The top plate of middle chamber in specimen G forms an elliptical penetrating hole,while that in specimen PCG only shows a very slight local dent.The peak vertical displacement and residual displacement of PCG decrease by 74.8% and 73.7%,respectively,compared with those of specimen G.For the TNT explosion with small equivalent,the polyurea coating has a more significant protective effect on reducing the size of fracture.With the increase of TNT equivalent,the protective effect of polyurea on reducing girder displacement becomes more significant.The optimal reinforcement ratio,concrete strength,thickness and range of polyurea coating were also drawn.展开更多
As drilling wells continue to move into deep ultra-deep layers,the requirements for temperature resistance of drilling fluid treatments are getting higher and higher.Among them,blocking agent,as one of the key treatme...As drilling wells continue to move into deep ultra-deep layers,the requirements for temperature resistance of drilling fluid treatments are getting higher and higher.Among them,blocking agent,as one of the key treatment agents,has also become a hot spot of research.In this study,a high temperature resistant strong adsorption rigid blocking agent(QW-1)was prepared using KH570 modified silica,acrylamide(AM)and allyltrimethylammonium chloride(TMAAC).QW-1 has good thermal stability,average particle size of 1.46μm,water contact angle of 10.5.,has a strong hydrophilicity,can be well dispersed in water.The experimental results showed that when 2 wt%QW-1 was added to recipe A(4 wt%bentonite slurry+0.5 wt%DSP-1(filtration loss depressant)),the API filtration loss decreased from 7.8to 6.4 m L.After aging at 240.C,the API loss of filtration was reduced from 21 to 14 m L,which has certain performance of high temperature loss of filtration.At the same time,it is effective in sealing 80-100mesh and 100-120 mesh sand beds as well as 3 and 5μm ceramic sand discs.Under the same conditions,the blocking performance was superior to silica(5μm)and calcium carbonate(2.6μm).In addition,the mechanism of action of QW-1 was further investigated.The results show that QW-1 with amide and quaternary ammonium groups on the molecular chain can be adsorbed onto the surface of clay particles through hydrogen bonding and electrostatic interaction to form a dense blocking layer,thus preventing further intrusion of drilling fluid into the formation.展开更多
Magnesium(Mg)alloys,the lightest metal construction material used in industry,play a vital role in future development.However,the poor corrosion resistance of Mg alloys in corrosion environments largely limits their p...Magnesium(Mg)alloys,the lightest metal construction material used in industry,play a vital role in future development.However,the poor corrosion resistance of Mg alloys in corrosion environments largely limits their potential wide applications.Therefore,a micro-arc oxidation/graphene oxide/stearic acid(MAO/GO/SA)superhydrophobic composite coating with superior corrosion resistance was fabricated on a Mg alloy AZ91D through micro-arc oxidation(MAO)technology,electrodeposition technique,and self-assembly technology.The composition and microstructure of the coating were characterized by scanning electron microscopy,X-ray diffraction,energy dispersive spectroscopy,and Raman spectroscopy.The effective protection of the MAO/GO/SA composite coating applied to a substrate was evaluated using potentiodynamic polarization,electrochemical impedance spectroscopy tests,and salt spray tests.The results showed that the MAO/GO/SA composite coating with a petal spherical structure had the best superhydrophobicity,and it attained a contact angle of 159.53°±2°.The MAO/GO/SA composite coating exhibited high resistance to corrosion,according to electrochemical and salt spray tests.展开更多
In recent years,water collecting systems,with the associated advantages of energy saving and noise reduction,have become the foundation for the development of a scheme to optimize the structure of cooling towers.To ex...In recent years,water collecting systems,with the associated advantages of energy saving and noise reduction,have become the foundation for the development of a scheme to optimize the structure of cooling towers.To explore the feasibility of this approach for mechanical draft cooling towers,a small-scale experimental device has been built to study the resistance and splash performances of three U-type water collecting devices(WCDs)for different water flow rates and wind speeds.The experimental results show that within the considered ranges of wind speed and water flow rate,the pressure drop of the different WCDs can vary significantly.The resistance and local splash performances can also be remarkably different.Some recommendations about the most suitable system are provided.Moreover,a regression analysis of the experimental data is conducted,and the resulting fitting formulas for resistance and splash performance of WCD are reported.展开更多
The impact properties of normal concrete (NC) and reinforced concrete (RC) specimens,steel fibre reinforced concrete (SFRC) specimens and RC+SFRC specimens with different steel fibre dosages were investigated with the...The impact properties of normal concrete (NC) and reinforced concrete (RC) specimens,steel fibre reinforced concrete (SFRC) specimens and RC+SFRC specimens with different steel fibre dosages were investigated with the drop-weight impact test recommended by ACI Committee 544.The results indicate that the number of blows to final failure is greatly increased by addition of steel fibres.Moreover,the combination of steel fibres and steel rebars demonstrates a significant positive composite effect on the impact resistance,which results in the improvement in impact toughness of concrete specimens.In the view of variation of impact test results,the two-parameter Weibull distribution was adopted to analyze the experimental data.It is proved that the probabilistic distributions of the blows to first crack and to final failure of six types of samples approximately follow two-parameter Weibull distribution.展开更多
Epoxy resin powder coating has been successfully applied on the corrosion protection of magnesium lithium alloys.However,poor wear resistance and microcracks formed during the solidification have limited it extensive ...Epoxy resin powder coating has been successfully applied on the corrosion protection of magnesium lithium alloys.However,poor wear resistance and microcracks formed during the solidification have limited it extensive application.There are limited approaches to exploit such anti-corrosion and mechanical properties of magnesium lithium alloys.Herein,the epoxy resin powder coating with polydopamine modified molybdenum disulfide(MoS_(2)@PDA-EP powder coating with 0,0.1,0.2,0.5,1.0 wt.%loading)was well prepared by melt extrusion to investigate its anticorrosion performance and wear resistance.The results revealed that the addition of MoS_(2)@PDA enhanced the adhesion strength between coatings and alloys,wear resistance and corrosion protection of the powder coatings.Among them,the optimum was obtained by 0.2 wt.%MoS_(2)@PDA-EP powder coating which could be attributed to well dispersion and efficient adhesion with coating matrix.To conclude,MoS_(2)@PDA-EP powder coating is meaningfully beneficial for the anticorrosive and wear performance improvement of magnesium lithium alloys.展开更多
[Objectives]To explore the effects of nano compound Chinese herbal medicine feed additive on growth performance,meat quality and disease resistance of chickens.[Methods]Chickens were fed with nano compound Chinese her...[Objectives]To explore the effects of nano compound Chinese herbal medicine feed additive on growth performance,meat quality and disease resistance of chickens.[Methods]Chickens were fed with nano compound Chinese herbal medicine feed additive developed by Hunan Polytechnic of Environment and Biology,including 120 chickens in the treatment group and 120 chickens in the control group(CK).The growth performance indices(body weight gain,feed to gain ratio and slaughter index),meat quality indices(pH value,color,drip loss,shear force)and disease resistance indices(morbidity and mortality)of the chickens in the treatment and CK groups were recorded and determined,respectively.[Results]The inclusion of 2%nano compound Chinese herbal medicine feed additive in the diet significantly increased the growth rate,reduced the feed-to-gain ratio and improved the meat quality of the chickens.Supplementing Chinese herbal medicine could increase the pH value and reduce the drip loss and shear force of chicken meat.At the same time,the body's immune function,antioxidant level and resistance against diseases of the chickens fed with nano compound Chinese herbal medicine feed additive were improved.[Conclusions]The inclusion of nano compound Chinese herbal medicine feed additive in the diet can improve the growth performance,meat quality and disease resistance of chickens.展开更多
To simulate ballast performance accurately and efficiently,the input in discrete element models should be carefully selected,including the contact model and applied particle shape.To study the effects of the contact m...To simulate ballast performance accurately and efficiently,the input in discrete element models should be carefully selected,including the contact model and applied particle shape.To study the effects of the contact model and applied particle shape on the ballast performance(shear strength and deformation),the direct shear test(DST)model and the large-scale process simulation test(LPST)model were developed on the basis of two types of contact models,namely the rolling resistance linear(RRL)model and the linear contact(LC)model.Particle shapes are differentiated by clumps.A clump is a sphere assembly for one ballast particle.The results show that compared with the typical LC model,the RRL method is more efficient and realistic to predict shear strength results of ballast assemblies in DSTs.In addition,the RRL contact model can also provide accurate vertical and lateral ballast deformation under the cyclic loading in LPSTs.展开更多
This paper presented the results of an experimental investigation into the resistance performance of a wave-piercing trimaran with three alternative side hull forms,including asymmetric inboard,asymmetric outboard,and...This paper presented the results of an experimental investigation into the resistance performance of a wave-piercing trimaran with three alternative side hull forms,including asymmetric inboard,asymmetric outboard,and symmetric at various stagger/separation positions.Model tests were carried out at the National Iranian Marine Laboratory(NIMALA)towing tank using a scale model of a trimaran at the Froude numbers from 0.225 to 0.60.Results showed that by moving the side hulls to the forward of the main hull transom,the total resistance coefficient of trimaran decreased.Findings,furthermore,demonstrated that the symmetry shape of the side hull had the best performance on total resistance among three side hull forms.Results of this study are useful for selecting the side hull configuration from the resistance viewpoint.展开更多
It is found that the incorporation of Nitrite Corrosion Inhibitor (NCI) greatly weakens the resistance of mixtures to sulfate attack. To study the mechanism of this phenomenon, in this paper, the influence of NCI add...It is found that the incorporation of Nitrite Corrosion Inhibitor (NCI) greatly weakens the resistance of mixtures to sulfate attack. To study the mechanism of this phenomenon, in this paper, the influence of NCI addition on the cement paste and microstructure change of high performance concrete specimens is studied by means of quantitative XRD, SEM tests. The results demonstrate that the incorporation of NCI accelerates the formation of calcium hydroxide and ettringite crystals, and weakens the pore refinement effect caused by the secondary hydration reaction of fly ash and microsilica. At the age up to one year, the relative crystal quantity in mixture containing NCI is always higher than that in control mixture. The reasons for the degradation in sulfate resistance of mixtures may be attributed to the increase and stability of the calcium hydroxide and ettringite crystals formed and the weakening of secondary hydration reaction. Based on the results, conclusion can be drawn that NCI should be used cautiously in practical engineering where high resistance to sulfate attack is required. (Author abstract) 7 Refs.展开更多
Fracture behavior is one of the most important,yet still little understood properties of ultra-high performance cementitious composites(UHPCC),a new marine structural engineering material. Research on the fracture and...Fracture behavior is one of the most important,yet still little understood properties of ultra-high performance cementitious composites(UHPCC),a new marine structural engineering material. Research on the fracture and direct tension behavior of UHPCC was carried out.The constitution law of UHPCC was divided into three phases:pre-partial debonding,partial debonding,and pullout phases.A direct tension constitution law was constructed based on the proposed fiber reinforcing parameter as a function of fiber volume fraction,fiber diameter and length,and fiber bonding strength.With the definition of linear crack shape,the energy release rate of UHPCC was derived and the R-curve equation was calculated from this.Loading tests of UHPCC using a three-point bending beam with an initial notch were carried out.The predictions from the proposed R-curve were in good agreement with the test results, indicating that the proposed R-curve accurately describes the fracture resistance of UHPCC.Introduction of a fiber reinforcement parameter bridges the fracture property R-curve and micro-composites’ mechanics parameters together.This has laid the foundation for further research into fracture properties based on micro-mechanics.The proposed tension constitution law and R-curve can be references for future UHPCC fracture evaluation.展开更多
We investigate the effect of the formation process under pulse and dc modes on the performance of one transistor and one resistor （1 T1R） resistance random access memory （RRAM） device. All the devices are operated...We investigate the effect of the formation process under pulse and dc modes on the performance of one transistor and one resistor （1 T1R） resistance random access memory （RRAM） device. All the devices are operated under the same test conditions, except for the initial formation process with different modes. Based on the statistical results, the high resistance state （FIRS） under the dc forming mode shows a lower value with better distribution compared with that under the pulse mode. One of the possible reasons for such a phenomenon originates from different properties of conductive filament （CF） formed in the resistive switching layer under two different modes. For the dc forming mode, the formed filament is thought to be continuous, which is hard to be ruptured, resulting in a lower HRS. However, in the case of pulse forming, the filament is discontinuous where the transport mechanism is governed by hopping. The low resistance state （LRS） can be easily changed by removing a few trapping states from the conducting path. Hence, a higher FIRS is thus observed. However, the HRS resistance is highly dependent on the length of the gap opened. A slight variation of the gap length will cause wide dispersion of resistance.展开更多
Background:Hemodialysis is the major treatment option for patients with chronic kidney disease.With the increase in the number of maintenance hemodialysis patients,debilitating conditions of muscle willing and atrophy...Background:Hemodialysis is the major treatment option for patients with chronic kidney disease.With the increase in the number of maintenance hemodialysis patients,debilitating conditions of muscle willing and atrophy and numerous health problems associated with chronic kidney disease and hemodialysis have become the most significant concerns.Methods:This randomized controlled trial study design will be conducted at Al-Najaf city in the southern region of Iraq and carried out on 68 patients with chronic kidney disease undergoing hemodialysis for at least six months and who had a medically stable condition,which will be randomly divided into training group;exercise therapy and control,groups.The training group participated in 8-week(3 sessions per week)resistance exercise therapy in three sets of 10 repetitions of knee extension,hip flexion,and hip abduction with the use of an elastic band under the supervision of a training physiotherapist and researcher during the first hour of the three routine hemodialysis treatment session per week.But the control group did not experience any intervention.To analyze the data,two-way analysis of variance and Bonferroni statistical tests will be used at the significant level of(P=0.05).Discussion:Important features of this study include the randomization procedures,double-blind,large sample size,and a standardized protocol for resistance exercise training on the physical performance of hemodialysis patients.This study aims to determine the effectiveness of resistance exercise for the patient with chronic kidney disease and undergoing hemodialysis.Therefore,our results will be useful for patients with chronic kidney diseases,medical staff,and healthcare decision-makers.展开更多
The surface of carbon nanotubes(CNTs)was modified by plasma to improve the dispersion,conductivity and adsorption properties of carbon nanotubes.Cement-based composites made with plasmatreated carbon nanotubes(P-CNTs)...The surface of carbon nanotubes(CNTs)was modified by plasma to improve the dispersion,conductivity and adsorption properties of carbon nanotubes.Cement-based composites made with plasmatreated carbon nanotubes(P-CNTs)at different perntages were tested under repeated cyclic axial compressive stress by four electrode methods to measure the electric resistance.Those made with CNTs without plasma treatment as controls were tested also.The results showed that electric resistance change values of the cement mortar with P-CNT and CNT were all monatomic corresponding to the cyclic loading.When the water-cement ratio of the mortar was fixed,increasing of the P-CNT/CNT content would increase the resistance change value of the mortars added with P-CNT/CNT,and the sensitivity performance.It has certain engineering application value.展开更多
Although there are many kinds of fracture tests to choose from in evaluating the crack resistance of asphalt mixture,the semi-circular bending(SCB)test has attracted a lot of attention in the academic road engineering...Although there are many kinds of fracture tests to choose from in evaluating the crack resistance of asphalt mixture,the semi-circular bending(SCB)test has attracted a lot of attention in the academic road engineering community because of its simplicity,stability,and flexibility in testing and evaluation.The SCB test has become a common method to study the cracking resistance of asphalt mixture in recent years.This paper mainly summarizes the overview of the SCB test,summarizes some research results and common characterization parameters of the SCB test method in monotone test and fatigue test in recent years,and predicts and suggests the research direction of the SCB test in the future.It is found that the research on the monotonic SCB test is more comprehensive,and the research on the SCB fatigue test needs to be further improved in the aspects of loading mode,characterization parameter selection,and so on.Researchers can flexibly adjust the geometric dimensions and the test parameters of semi-cylindrical specimens,and conduct comprehensive analysis combined with the results of numerical simulation.The crack resistance of asphalt mixture can be comprehensively evaluated by fracture energy,fracture toughness,stiffness,flexibility index and other fracture indicators,combined with the crack propagation of the specimen.The analysis of numerical simulation can confirm the test results.In order to standardize the setting of fatigue parameters for future application,it is necessary to standardize the setting of bending performance.展开更多
We present systematic investigations on the physics,detection performance and inversion of logging-while-drilling extradeep azimuthal resistivity measurements(EDARM).First,the definitions of EDRAM measurements are dis...We present systematic investigations on the physics,detection performance and inversion of logging-while-drilling extradeep azimuthal resistivity measurements(EDARM).First,the definitions of EDRAM measurements are discussed,followed by the derivation of the attenuation and phase-shift geometrical factors to illustrate the relative contributions of formation units to the observed signals.Then,a new definition of detection depth,which considers the uncertainty of inversion results caused by the data noise,is proposed to quantify the detection capability of ED ARM.Finally,the B ayesian theory associated with Markov chain Monte Carlo sampling is introduced for fast processing of EDARM data.Numerical results show that ED ARM is capable of detecting the azimuth and distance of remote bed boundaries,and the detection capability increases with increasing spacing and resistivity contrast.The EDARM tool can accommodate a large range of formation resistivity and is able to provide the resistivity anisotropy at arbitrary relative dipping angles.In addition,multiple bed boundaries and reservoir images near the borehole are readily obtained by using the Bayesian inversion.展开更多
Background Antimicrobial alternatives are urgently needed,including for poultry production systems.In this study,we tested the potential broad-range antimicrobial alternative peracetic acid,delivered in feed via the h...Background Antimicrobial alternatives are urgently needed,including for poultry production systems.In this study,we tested the potential broad-range antimicrobial alternative peracetic acid,delivered in feed via the hydrolysis of encapsulated precursors through a 28-day study using 375 Ross 308 broiler chickens.We tested two peracetic acid concentrations,30 and 80 mg/kg on birds housed on re-used litter,and we evaluated the impact of both levels on gut microbial communities,bacterial concentration,antimicrobial resistance genes relative abundance and growth performance when compared to control birds housed on either clean or re-used litter.Results Body weight gain and feed conversion ratio improved in peracetic acid fed birds.At d 28,birds given 30 mg/kg of peracetic acid had a decreased Firmicutes and an increased Proteobacteria abundance in the jejunum,accompanied by an increase in Bacillus,Flavonifractor and Rombustia in the caeca,and a decreased abundance of tetracycline resistance genes.Chicken given 80 mg/kg of peracetic acid had greater caecal abundance of macrolides lincosamides and streptogramins resistance genes.Growth performance on clean litter was reduced compared to reused litter,which concurred with increased caecal abundance of Blautia,decreased caecal abundance of Escherichia/Shigella,Anaerostipes and Jeotgalicoccus,and greater gene abundance of vancomycin,tetracycline,and macrolides resistance genes.Conclusions Peracetic acid could be used as a safe broad-spectrum antimicrobial alternative in broilers.Encapsulated precursors were able to reduce the bacterial concentration in the jejunum whilst promoting the proliferation of probiotic genera in the caeca,especially at the low peracetic acid concentrations tested,and improve growth performance.Moreover,our findings offer further insights on potential benefits of rearing birds on re-used litter,suggesting that the latter could be associated with better performance and reduced antimicrobial resistance risk compared to clean litter rearing.展开更多
In this study,acrylic acid was used as a neutralizer to prepare bio-based WPU with an interpenetrating polymer network structure by thermally induced free radical emulsion polymerization.The effects of the content of ...In this study,acrylic acid was used as a neutralizer to prepare bio-based WPU with an interpenetrating polymer network structure by thermally induced free radical emulsion polymerization.The effects of the content of acrylic acid on the properties of the resulting waterborne polyurethane-poly(acrylic acid)(WPU-PAA)dispersion and the films were systematically investigated.The results showed that the cross-linking density of the interpenetrating network polymers was increased and the interlocking structure of the soft and hard phase dislocations in the molecular segments of the double networks was tailored with increasing the content of acrylic acid,leading to enhancement of the mechanical properties and water resistance of WPU-PAA films.Notably,with the increase in content of acrylic acid,the tensile strength,Young’s modulus,and toughness of the WPU-PAA-110 film increased by 3 times,and 8 times,and 2.4 times compared with WPU-PAA-80,respectively.The WPU-PAA-100 film showed the best water resistance,and the water absorption rate at 96 h was only 3.27%.This work provided a new design scheme for constructing bio-based WPU materials with excellent properties.展开更多
Multi⁃performance optimization of tread rubber composites is a key issue of great concern in automotive industry.Traditional experimental design approach via“trial and error”or intuition is ineffective due to mutual...Multi⁃performance optimization of tread rubber composites is a key issue of great concern in automotive industry.Traditional experimental design approach via“trial and error”or intuition is ineffective due to mutual inhibition among multiple properties.A“Uniform design⁃Machine learning”strategy for performance prediction and multi⁃performance optimization of tread rubber composites was proposed.The wear resistance,rolling resistance,tensile strength and wet skid resistance were simultaneously optimized.A series of feasible optimization designs were screened via statistical analysis and machine learning analysis,and were experimentally prepared.The verification experiments demonstrate that the optimization design via machine learning analysis meets the optimization requirements of all target performance,especially for Akron abrasion and 60℃tanδ(about 21%and 9%lower than the design targets,respectively)due to the inhibition of mechanical degradation and good dispersion of fillers.展开更多
One dimensional(1D) and three dimensional(3D) ultrasound sources were applied to the solidification process of Mg_(71.5)Zn_(26.1)Y_(2.4) alloy.The acoustic spectra were in-situ measured, based on which the cavitation ...One dimensional(1D) and three dimensional(3D) ultrasound sources were applied to the solidification process of Mg_(71.5)Zn_(26.1)Y_(2.4) alloy.The acoustic spectra were in-situ measured, based on which the cavitation intensities and dynamic solidification mechanism were further investigated. With the increase of ultrasonic dimension and amplitude, the primary Mg_(3)Zn_(6)Y phase was significantly refined from petals to nearly pentagonal shape. The sound field measurements showed that the transient cavitation played a decisive role in generating a high local undercooling, which facilitated the formation of icosahedral clusters and promoted the nucleation of primary Mg_(3)Zn_(6)Y phase. The morphological transition of(α-Mg+Mg_(3)Zn_(6)Y) eutectic from lamellar to anomalous structure occurred under 3D ultrasonic condition. The stable cavitation took the main responsibility because the high pressure excited by nonlinearly oscillating bubbles induced the preferential nucleation of α-Mg phase rather than Mg_(3)Zn_(6)Y phase. As compared with its static values, the tensile strength and compression plasticity of this alloy were increased by the factors of 1.9 and 2.1, and its corrosion resistance was also improved with the corrosion current density decreased by one order of magnitude.展开更多
基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20200494)China Postdoctoral Science Foundation(Grant No.2021M701725)+3 种基金Jiangsu Postdoctoral Research Funding Program(Grant No.2021K522C)Fundamental Research Funds for the Central Universities(Grant No.30919011246)National Natural Science Foundation of China(Grant No.52278188)Natural Science Foundation of Jiangsu Province(Grant No.BK20211196)。
文摘To study the anti-explosion protection effect of polyurea coating on reinforced concrete box girder,two segmental girder specimens were made at a scale of 1:3,numbered as G(without polyurea coating)and PCG(with polyurea coating).The failure characteristics and dynamic responses of the specimens were compared through conducting explosion tests.The reliability of the numerical simulation using LS-DYNA software was verified by the test results.The effects of different scaled distances,reinforcement ratios,concrete strengths,coating thicknesses and ranges of polyurea were studied.The results show that the polyurea coating can effectively enhance the anti-explosion performance of the girder.The top plate of middle chamber in specimen G forms an elliptical penetrating hole,while that in specimen PCG only shows a very slight local dent.The peak vertical displacement and residual displacement of PCG decrease by 74.8% and 73.7%,respectively,compared with those of specimen G.For the TNT explosion with small equivalent,the polyurea coating has a more significant protective effect on reducing the size of fracture.With the increase of TNT equivalent,the protective effect of polyurea on reducing girder displacement becomes more significant.The optimal reinforcement ratio,concrete strength,thickness and range of polyurea coating were also drawn.
基金supported by the National Natural Science Foundation of China (No.52074330,No.52288101)。
文摘As drilling wells continue to move into deep ultra-deep layers,the requirements for temperature resistance of drilling fluid treatments are getting higher and higher.Among them,blocking agent,as one of the key treatment agents,has also become a hot spot of research.In this study,a high temperature resistant strong adsorption rigid blocking agent(QW-1)was prepared using KH570 modified silica,acrylamide(AM)and allyltrimethylammonium chloride(TMAAC).QW-1 has good thermal stability,average particle size of 1.46μm,water contact angle of 10.5.,has a strong hydrophilicity,can be well dispersed in water.The experimental results showed that when 2 wt%QW-1 was added to recipe A(4 wt%bentonite slurry+0.5 wt%DSP-1(filtration loss depressant)),the API filtration loss decreased from 7.8to 6.4 m L.After aging at 240.C,the API loss of filtration was reduced from 21 to 14 m L,which has certain performance of high temperature loss of filtration.At the same time,it is effective in sealing 80-100mesh and 100-120 mesh sand beds as well as 3 and 5μm ceramic sand discs.Under the same conditions,the blocking performance was superior to silica(5μm)and calcium carbonate(2.6μm).In addition,the mechanism of action of QW-1 was further investigated.The results show that QW-1 with amide and quaternary ammonium groups on the molecular chain can be adsorbed onto the surface of clay particles through hydrogen bonding and electrostatic interaction to form a dense blocking layer,thus preventing further intrusion of drilling fluid into the formation.
基金financially supported by the Guangxi Natural Science Foundation,China(No.2020GXNSFAA 159011)the National Natural Science Foundation of China(No.51664011).
文摘Magnesium(Mg)alloys,the lightest metal construction material used in industry,play a vital role in future development.However,the poor corrosion resistance of Mg alloys in corrosion environments largely limits their potential wide applications.Therefore,a micro-arc oxidation/graphene oxide/stearic acid(MAO/GO/SA)superhydrophobic composite coating with superior corrosion resistance was fabricated on a Mg alloy AZ91D through micro-arc oxidation(MAO)technology,electrodeposition technique,and self-assembly technology.The composition and microstructure of the coating were characterized by scanning electron microscopy,X-ray diffraction,energy dispersive spectroscopy,and Raman spectroscopy.The effective protection of the MAO/GO/SA composite coating applied to a substrate was evaluated using potentiodynamic polarization,electrochemical impedance spectroscopy tests,and salt spray tests.The results showed that the MAO/GO/SA composite coating with a petal spherical structure had the best superhydrophobicity,and it attained a contact angle of 159.53°±2°.The MAO/GO/SA composite coating exhibited high resistance to corrosion,according to electrochemical and salt spray tests.
基金This work was supported by the Shandong Natural Science Foundation(Grant No.ZR2022ME008)the Shenzhen Science and Technology Program(KCXFZ20201221173409026)+2 种基金the Young Scholars Program of Shandong University(YSPSDU,No.2018WLJH73)the Open Project of State Key Laboratory of Clean Energy Utilization,Zhejiang University(Program No.ZJUCEU2020011)the Shandong Natural Science Foundation(Grant No.ZR2021ME118).
文摘In recent years,water collecting systems,with the associated advantages of energy saving and noise reduction,have become the foundation for the development of a scheme to optimize the structure of cooling towers.To explore the feasibility of this approach for mechanical draft cooling towers,a small-scale experimental device has been built to study the resistance and splash performances of three U-type water collecting devices(WCDs)for different water flow rates and wind speeds.The experimental results show that within the considered ranges of wind speed and water flow rate,the pressure drop of the different WCDs can vary significantly.The resistance and local splash performances can also be remarkably different.Some recommendations about the most suitable system are provided.Moreover,a regression analysis of the experimental data is conducted,and the resulting fitting formulas for resistance and splash performance of WCD are reported.
基金Project(50578026) supported by the National Natural Science Foundation of ChinaProject supported by FCT (SFRH/BPD/22680/2005)and Research Center of Mathematics of the University of Minho through the FCT Pluriannual Funding Program
文摘The impact properties of normal concrete (NC) and reinforced concrete (RC) specimens,steel fibre reinforced concrete (SFRC) specimens and RC+SFRC specimens with different steel fibre dosages were investigated with the drop-weight impact test recommended by ACI Committee 544.The results indicate that the number of blows to final failure is greatly increased by addition of steel fibres.Moreover,the combination of steel fibres and steel rebars demonstrates a significant positive composite effect on the impact resistance,which results in the improvement in impact toughness of concrete specimens.In the view of variation of impact test results,the two-parameter Weibull distribution was adopted to analyze the experimental data.It is proved that the probabilistic distributions of the blows to first crack and to final failure of six types of samples approximately follow two-parameter Weibull distribution.
基金financial support provided by the National Natural Science Foundation of China(Grant No.U1806225)the National Natural Science Foundation of China(Grant No.51908092)the Joint Funds of the National Natural Science Foundation of China-Guangdong(Grant No.U1801254)。
文摘Epoxy resin powder coating has been successfully applied on the corrosion protection of magnesium lithium alloys.However,poor wear resistance and microcracks formed during the solidification have limited it extensive application.There are limited approaches to exploit such anti-corrosion and mechanical properties of magnesium lithium alloys.Herein,the epoxy resin powder coating with polydopamine modified molybdenum disulfide(MoS_(2)@PDA-EP powder coating with 0,0.1,0.2,0.5,1.0 wt.%loading)was well prepared by melt extrusion to investigate its anticorrosion performance and wear resistance.The results revealed that the addition of MoS_(2)@PDA enhanced the adhesion strength between coatings and alloys,wear resistance and corrosion protection of the powder coatings.Among them,the optimum was obtained by 0.2 wt.%MoS_(2)@PDA-EP powder coating which could be attributed to well dispersion and efficient adhesion with coating matrix.To conclude,MoS_(2)@PDA-EP powder coating is meaningfully beneficial for the anticorrosive and wear performance improvement of magnesium lithium alloys.
基金Project of Hunan Province for Science of Education during 13th Five-Year Plan Period[XJK18BZY066]Hengyang Social Science Foundation Project[2017B(1)010].
文摘[Objectives]To explore the effects of nano compound Chinese herbal medicine feed additive on growth performance,meat quality and disease resistance of chickens.[Methods]Chickens were fed with nano compound Chinese herbal medicine feed additive developed by Hunan Polytechnic of Environment and Biology,including 120 chickens in the treatment group and 120 chickens in the control group(CK).The growth performance indices(body weight gain,feed to gain ratio and slaughter index),meat quality indices(pH value,color,drip loss,shear force)and disease resistance indices(morbidity and mortality)of the chickens in the treatment and CK groups were recorded and determined,respectively.[Results]The inclusion of 2%nano compound Chinese herbal medicine feed additive in the diet significantly increased the growth rate,reduced the feed-to-gain ratio and improved the meat quality of the chickens.Supplementing Chinese herbal medicine could increase the pH value and reduce the drip loss and shear force of chicken meat.At the same time,the body's immune function,antioxidant level and resistance against diseases of the chickens fed with nano compound Chinese herbal medicine feed additive were improved.[Conclusions]The inclusion of nano compound Chinese herbal medicine feed additive in the diet can improve the growth performance,meat quality and disease resistance of chickens.
基金by the China Scholarship Council and the Natural Science Foundation of China(Grant No.51578469)We also would like to acknowledge the support of the Chinese Program of Introducing Talents of Discipline to Universities(111 Project,Grant No.B16041)。
文摘To simulate ballast performance accurately and efficiently,the input in discrete element models should be carefully selected,including the contact model and applied particle shape.To study the effects of the contact model and applied particle shape on the ballast performance(shear strength and deformation),the direct shear test(DST)model and the large-scale process simulation test(LPST)model were developed on the basis of two types of contact models,namely the rolling resistance linear(RRL)model and the linear contact(LC)model.Particle shapes are differentiated by clumps.A clump is a sphere assembly for one ballast particle.The results show that compared with the typical LC model,the RRL method is more efficient and realistic to predict shear strength results of ballast assemblies in DSTs.In addition,the RRL contact model can also provide accurate vertical and lateral ballast deformation under the cyclic loading in LPSTs.
文摘This paper presented the results of an experimental investigation into the resistance performance of a wave-piercing trimaran with three alternative side hull forms,including asymmetric inboard,asymmetric outboard,and symmetric at various stagger/separation positions.Model tests were carried out at the National Iranian Marine Laboratory(NIMALA)towing tank using a scale model of a trimaran at the Froude numbers from 0.225 to 0.60.Results showed that by moving the side hulls to the forward of the main hull transom,the total resistance coefficient of trimaran decreased.Findings,furthermore,demonstrated that the symmetry shape of the side hull had the best performance on total resistance among three side hull forms.Results of this study are useful for selecting the side hull configuration from the resistance viewpoint.
文摘It is found that the incorporation of Nitrite Corrosion Inhibitor (NCI) greatly weakens the resistance of mixtures to sulfate attack. To study the mechanism of this phenomenon, in this paper, the influence of NCI addition on the cement paste and microstructure change of high performance concrete specimens is studied by means of quantitative XRD, SEM tests. The results demonstrate that the incorporation of NCI accelerates the formation of calcium hydroxide and ettringite crystals, and weakens the pore refinement effect caused by the secondary hydration reaction of fly ash and microsilica. At the age up to one year, the relative crystal quantity in mixture containing NCI is always higher than that in control mixture. The reasons for the degradation in sulfate resistance of mixtures may be attributed to the increase and stability of the calcium hydroxide and ettringite crystals formed and the weakening of secondary hydration reaction. Based on the results, conclusion can be drawn that NCI should be used cautiously in practical engineering where high resistance to sulfate attack is required. (Author abstract) 7 Refs.
基金the Center of Concrete Corea,Korea Development and Application of High Performance and Multi-Function Concrete(05-CCT-D11)
文摘Fracture behavior is one of the most important,yet still little understood properties of ultra-high performance cementitious composites(UHPCC),a new marine structural engineering material. Research on the fracture and direct tension behavior of UHPCC was carried out.The constitution law of UHPCC was divided into three phases:pre-partial debonding,partial debonding,and pullout phases.A direct tension constitution law was constructed based on the proposed fiber reinforcing parameter as a function of fiber volume fraction,fiber diameter and length,and fiber bonding strength.With the definition of linear crack shape,the energy release rate of UHPCC was derived and the R-curve equation was calculated from this.Loading tests of UHPCC using a three-point bending beam with an initial notch were carried out.The predictions from the proposed R-curve were in good agreement with the test results, indicating that the proposed R-curve accurately describes the fracture resistance of UHPCC.Introduction of a fiber reinforcement parameter bridges the fracture property R-curve and micro-composites’ mechanics parameters together.This has laid the foundation for further research into fracture properties based on micro-mechanics.The proposed tension constitution law and R-curve can be references for future UHPCC fracture evaluation.
基金Supported by the National Basic Research Program of China under Grant Nos 2011CBA00602,2010CB934200,2011CB921804,2011CB707600,2011AA010401,and 2011AA010402the National Natural Science Foundation of China under Grant Nos61322408,61334007,61376112,61221004,61274091,61106119,61106082,and 61006011
文摘We investigate the effect of the formation process under pulse and dc modes on the performance of one transistor and one resistor （1 T1R） resistance random access memory （RRAM） device. All the devices are operated under the same test conditions, except for the initial formation process with different modes. Based on the statistical results, the high resistance state （FIRS） under the dc forming mode shows a lower value with better distribution compared with that under the pulse mode. One of the possible reasons for such a phenomenon originates from different properties of conductive filament （CF） formed in the resistive switching layer under two different modes. For the dc forming mode, the formed filament is thought to be continuous, which is hard to be ruptured, resulting in a lower HRS. However, in the case of pulse forming, the filament is discontinuous where the transport mechanism is governed by hopping. The low resistance state （LRS） can be easily changed by removing a few trapping states from the conducting path. Hence, a higher FIRS is thus observed. However, the HRS resistance is highly dependent on the length of the gap opened. A slight variation of the gap length will cause wide dispersion of resistance.
文摘Background:Hemodialysis is the major treatment option for patients with chronic kidney disease.With the increase in the number of maintenance hemodialysis patients,debilitating conditions of muscle willing and atrophy and numerous health problems associated with chronic kidney disease and hemodialysis have become the most significant concerns.Methods:This randomized controlled trial study design will be conducted at Al-Najaf city in the southern region of Iraq and carried out on 68 patients with chronic kidney disease undergoing hemodialysis for at least six months and who had a medically stable condition,which will be randomly divided into training group;exercise therapy and control,groups.The training group participated in 8-week(3 sessions per week)resistance exercise therapy in three sets of 10 repetitions of knee extension,hip flexion,and hip abduction with the use of an elastic band under the supervision of a training physiotherapist and researcher during the first hour of the three routine hemodialysis treatment session per week.But the control group did not experience any intervention.To analyze the data,two-way analysis of variance and Bonferroni statistical tests will be used at the significant level of(P=0.05).Discussion:Important features of this study include the randomization procedures,double-blind,large sample size,and a standardized protocol for resistance exercise training on the physical performance of hemodialysis patients.This study aims to determine the effectiveness of resistance exercise for the patient with chronic kidney disease and undergoing hemodialysis.Therefore,our results will be useful for patients with chronic kidney diseases,medical staff,and healthcare decision-makers.
基金Funded by National Natural Science Foundation of China(No.52178149)。
文摘The surface of carbon nanotubes(CNTs)was modified by plasma to improve the dispersion,conductivity and adsorption properties of carbon nanotubes.Cement-based composites made with plasmatreated carbon nanotubes(P-CNTs)at different perntages were tested under repeated cyclic axial compressive stress by four electrode methods to measure the electric resistance.Those made with CNTs without plasma treatment as controls were tested also.The results showed that electric resistance change values of the cement mortar with P-CNT and CNT were all monatomic corresponding to the cyclic loading.When the water-cement ratio of the mortar was fixed,increasing of the P-CNT/CNT content would increase the resistance change value of the mortars added with P-CNT/CNT,and the sensitivity performance.It has certain engineering application value.
基金The authors acknowledge the financial support from the National Natural Science Foundation of China(No.51968006).
文摘Although there are many kinds of fracture tests to choose from in evaluating the crack resistance of asphalt mixture,the semi-circular bending(SCB)test has attracted a lot of attention in the academic road engineering community because of its simplicity,stability,and flexibility in testing and evaluation.The SCB test has become a common method to study the cracking resistance of asphalt mixture in recent years.This paper mainly summarizes the overview of the SCB test,summarizes some research results and common characterization parameters of the SCB test method in monotone test and fatigue test in recent years,and predicts and suggests the research direction of the SCB test in the future.It is found that the research on the monotonic SCB test is more comprehensive,and the research on the SCB fatigue test needs to be further improved in the aspects of loading mode,characterization parameter selection,and so on.Researchers can flexibly adjust the geometric dimensions and the test parameters of semi-cylindrical specimens,and conduct comprehensive analysis combined with the results of numerical simulation.The crack resistance of asphalt mixture can be comprehensively evaluated by fracture energy,fracture toughness,stiffness,flexibility index and other fracture indicators,combined with the crack propagation of the specimen.The analysis of numerical simulation can confirm the test results.In order to standardize the setting of fatigue parameters for future application,it is necessary to standardize the setting of bending performance.
基金co-funded by Chinese Postdoctoral Science Foundation(2018M640663)the National Natural Science Foundation of China(41474100,41574118,41674131)National Science and Technology Major Project of the Ministry of Science and Technology of China(2017ZX05009-001)
文摘We present systematic investigations on the physics,detection performance and inversion of logging-while-drilling extradeep azimuthal resistivity measurements(EDARM).First,the definitions of EDRAM measurements are discussed,followed by the derivation of the attenuation and phase-shift geometrical factors to illustrate the relative contributions of formation units to the observed signals.Then,a new definition of detection depth,which considers the uncertainty of inversion results caused by the data noise,is proposed to quantify the detection capability of ED ARM.Finally,the B ayesian theory associated with Markov chain Monte Carlo sampling is introduced for fast processing of EDARM data.Numerical results show that ED ARM is capable of detecting the azimuth and distance of remote bed boundaries,and the detection capability increases with increasing spacing and resistivity contrast.The EDARM tool can accommodate a large range of formation resistivity and is able to provide the resistivity anisotropy at arbitrary relative dipping angles.In addition,multiple bed boundaries and reservoir images near the borehole are readily obtained by using the Bayesian inversion.
基金funded by the UK Department of Health and Social Care as part of the Global AMR Innovation Fund(GAMRIF,Project 104990)supports early-stage innovative research in underfunded areas of antimicrobial resistance(AMR)research and development for the benefit of those in low-and middle-income countries(LMICs),who bear the greatest burden of AMR.
文摘Background Antimicrobial alternatives are urgently needed,including for poultry production systems.In this study,we tested the potential broad-range antimicrobial alternative peracetic acid,delivered in feed via the hydrolysis of encapsulated precursors through a 28-day study using 375 Ross 308 broiler chickens.We tested two peracetic acid concentrations,30 and 80 mg/kg on birds housed on re-used litter,and we evaluated the impact of both levels on gut microbial communities,bacterial concentration,antimicrobial resistance genes relative abundance and growth performance when compared to control birds housed on either clean or re-used litter.Results Body weight gain and feed conversion ratio improved in peracetic acid fed birds.At d 28,birds given 30 mg/kg of peracetic acid had a decreased Firmicutes and an increased Proteobacteria abundance in the jejunum,accompanied by an increase in Bacillus,Flavonifractor and Rombustia in the caeca,and a decreased abundance of tetracycline resistance genes.Chicken given 80 mg/kg of peracetic acid had greater caecal abundance of macrolides lincosamides and streptogramins resistance genes.Growth performance on clean litter was reduced compared to reused litter,which concurred with increased caecal abundance of Blautia,decreased caecal abundance of Escherichia/Shigella,Anaerostipes and Jeotgalicoccus,and greater gene abundance of vancomycin,tetracycline,and macrolides resistance genes.Conclusions Peracetic acid could be used as a safe broad-spectrum antimicrobial alternative in broilers.Encapsulated precursors were able to reduce the bacterial concentration in the jejunum whilst promoting the proliferation of probiotic genera in the caeca,especially at the low peracetic acid concentrations tested,and improve growth performance.Moreover,our findings offer further insights on potential benefits of rearing birds on re-used litter,suggesting that the latter could be associated with better performance and reduced antimicrobial resistance risk compared to clean litter rearing.
基金by the Research and Development Program in Key Areas of Guangdong Province(Grant No.2020B0202010008)Guangdong Province Science&Technology Program(2018B030306016)+1 种基金Guangdong Provincial Innovation Team for General Key Technologies in Modern Agricultural Industry(2019KJ133)Key Projects of Basic Research and Applied Basic Research of the Higher Education Institutions of Guangdong Province(2018KZDXM014).
文摘In this study,acrylic acid was used as a neutralizer to prepare bio-based WPU with an interpenetrating polymer network structure by thermally induced free radical emulsion polymerization.The effects of the content of acrylic acid on the properties of the resulting waterborne polyurethane-poly(acrylic acid)(WPU-PAA)dispersion and the films were systematically investigated.The results showed that the cross-linking density of the interpenetrating network polymers was increased and the interlocking structure of the soft and hard phase dislocations in the molecular segments of the double networks was tailored with increasing the content of acrylic acid,leading to enhancement of the mechanical properties and water resistance of WPU-PAA films.Notably,with the increase in content of acrylic acid,the tensile strength,Young’s modulus,and toughness of the WPU-PAA-110 film increased by 3 times,and 8 times,and 2.4 times compared with WPU-PAA-80,respectively.The WPU-PAA-100 film showed the best water resistance,and the water absorption rate at 96 h was only 3.27%.This work provided a new design scheme for constructing bio-based WPU materials with excellent properties.
基金the State Key Program of National Natural Science of China(Grant No.51333004).
文摘Multi⁃performance optimization of tread rubber composites is a key issue of great concern in automotive industry.Traditional experimental design approach via“trial and error”or intuition is ineffective due to mutual inhibition among multiple properties.A“Uniform design⁃Machine learning”strategy for performance prediction and multi⁃performance optimization of tread rubber composites was proposed.The wear resistance,rolling resistance,tensile strength and wet skid resistance were simultaneously optimized.A series of feasible optimization designs were screened via statistical analysis and machine learning analysis,and were experimentally prepared.The verification experiments demonstrate that the optimization design via machine learning analysis meets the optimization requirements of all target performance,especially for Akron abrasion and 60℃tanδ(about 21%and 9%lower than the design targets,respectively)due to the inhibition of mechanical degradation and good dispersion of fillers.
基金financially supported by National Natural Science Foundation of China (nos.52088101 and 52130405)Basic Research Project of Shaanxi Natural Science Foundation (no: 2021JCW-09 and 2023-JC-JQ-28)Key R&D Plan of Shaanxi Province-Key Industrial Innovation Chain Project (no: 2020ZDLGY13-03)。
文摘One dimensional(1D) and three dimensional(3D) ultrasound sources were applied to the solidification process of Mg_(71.5)Zn_(26.1)Y_(2.4) alloy.The acoustic spectra were in-situ measured, based on which the cavitation intensities and dynamic solidification mechanism were further investigated. With the increase of ultrasonic dimension and amplitude, the primary Mg_(3)Zn_(6)Y phase was significantly refined from petals to nearly pentagonal shape. The sound field measurements showed that the transient cavitation played a decisive role in generating a high local undercooling, which facilitated the formation of icosahedral clusters and promoted the nucleation of primary Mg_(3)Zn_(6)Y phase. The morphological transition of(α-Mg+Mg_(3)Zn_(6)Y) eutectic from lamellar to anomalous structure occurred under 3D ultrasonic condition. The stable cavitation took the main responsibility because the high pressure excited by nonlinearly oscillating bubbles induced the preferential nucleation of α-Mg phase rather than Mg_(3)Zn_(6)Y phase. As compared with its static values, the tensile strength and compression plasticity of this alloy were increased by the factors of 1.9 and 2.1, and its corrosion resistance was also improved with the corrosion current density decreased by one order of magnitude.
