The effects of different curing systems on the properties of high volume fine mineral powder RPC （reactive powder concrete） and the appearances of hydrates were studied. The experimental results show that dry-heatin...The effects of different curing systems on the properties of high volume fine mineral powder RPC （reactive powder concrete） and the appearances of hydrates were studied. The experimental results show that dry-heating curing promotes the development of pozzolanic reactivity of fine mineral powder; due to low cement content, 0.20 water-bind ratio and high reactive fine mineral powder content, the strength of RPC increases by around 200% after steam curing and subsequent dry-heating curing. Scanning electron microscopy and energy spectrum diagram showed that： after the high volume fine mineral powder RPC with 0.16 water-bind ratio underwent steam curing and dry-heating curing, there was no significant change in the appearance of hydrates; after the RPC with 0.20 water-bind ratio, the cement content of 150 kg/m3 and more steel slag powder underwent dry-heating curing, there was a certain change in the appearance of C-S-H, the structure of gel was more compact and was uniformly distributed, and the Ca/Si of C-S-H gel decreased from 1.41 to around 1.20.展开更多
The crystal structure and morphology of the mineralization products were studied by scanning electron microscopy(SEM)and X-ray diffraction(XRD),and the thermal properties were studied by thermogravimetric-differential...The crystal structure and morphology of the mineralization products were studied by scanning electron microscopy(SEM)and X-ray diffraction(XRD),and the thermal properties were studied by thermogravimetric-differential scanning calorimetry(DSC)analysis.The changes of microorganism quantity and enzyme activity in pore solution with time were measured.The experimental results show that microorganism quantity and enzyme activity in pore solution reach the maximum at 50-60 h,mineralization curing begins at this time,the strength of microbial mineralized steel slag reaches the maximum.This study provides a good selection basis for selecting the optimum mineralization system for the production of microbial mineralized steel slag products.Bacterial mineralization can accelerate the rate of carbon sequestration in the mineralization process.The compressive strength of steel slag with 1.5% bacterial can reach up to 55.6 MPa.The microstructure and thermal properties of calcium carbonate precipitate induced by the enzymes of bacillus subtilis differs from the chemical precipitation in pore solution of steel slag.Through the analysis of the mineralized products of steel slag,the reaction rate of free calcium oxide and free magnesium oxide in steel slag after the addition of microorganisms is significantly increased,which improves the stability of steel slag as cementitious material.Meanwhile,the production of calcium carbonate,the main mineralized product,is significantly increased.展开更多
High durability and high tensile strength makes ultra-high performance concrete( UHPC) an ideal material for bridges,while its early shrinkage in the construction of cast-in-situ mass concrete leads structure crack-ea...High durability and high tensile strength makes ultra-high performance concrete( UHPC) an ideal material for bridges,while its early shrinkage in the construction of cast-in-situ mass concrete leads structure crack-easily,which restricts the application of UHPC in deck system. Whether reasonable amount of coarse aggregate can influence the strength of UHPC and improve the shrinkage performance or reduce the cost is still in doubt. Besides,in order to improve its constructability and workability, whether autoclaved curing system of UHPC can be changed remains to be further researched. In response to these circumstances, a systematic experimental study on the strength of UHPC mixed with coarse aggregate in different ratios has been presented in this paper. The three curing systems,namely standard curing,180-200 ℃/1. 1 MPa autoclaved curing,and hot water curing were tested to reveal the relationship between UHPC's properties and curing systems,and the UHPC ' s microstructure was also preliminarily studied by scanning electron microscope( SEM). The experimental research can draw the following conclusions. Under the condition of the same mix ratio, autoclaved curing guarantees the highest compressive strength,followed by hot water curing and standard curing. The compressive strength of concrete increases with the temperature in the range of 25 to 90 ℃ hot water curing,and high temperature in precuring period can speed up the strength development of UHPC,but the sequence of precuring period does not obviously affect the results. In 90 ℃ hot water and autoclaved curing,the strength is over 150 MPa,and it has little relation with gravel ratio. While the value increases first and then decreases in a lower temperature curing with the increasing of gravel amount,even only about 80 MPa at room temperature. The strength increases moderately along with the increase of the curing age by standard curing,especially in the initial stage.展开更多
By using diphenyliodonium salts with different counterions as photo acid generators (PAGs), the effect of acidity on ring-opening polymerization of epoxy monomers and polycondensation of polyol with hexamethoxymethyl ...By using diphenyliodonium salts with different counterions as photo acid generators (PAGs), the effect of acidity on ring-opening polymerization of epoxy monomers and polycondensation of polyol with hexamethoxymethyl melamine (HMMM) was studied. The result shows that the rate of ring-opening polymerization is evidently dependent on the acidity of the acid and strong photo-generated acid is required. However, there is a leveling effect in the polycondensation system; if the photo-generated acid is stronger than protonated HMMM, the acidity does not obviously affect the polycondensation rate.展开更多
To address the energy shortage and meet the requirements of environmental protection policies,the feasibility of premixed fuel 1(natural gas(NG),syngas,and hydrogen)and premixed fuel 2(NG and hydrogen)in the tobacco c...To address the energy shortage and meet the requirements of environmental protection policies,the feasibility of premixed fuel 1(natural gas(NG),syngas,and hydrogen)and premixed fuel 2(NG and hydrogen)in the tobacco curing system was studied.First,according to the law of conservation of energy and mass,a tobacco leaf curing system model was established.Then,the interchangeability index of the premixed fuels was analyzed,and their volume ratios were obtained.Finally,a numerical simulation analysis of the premixed fuel combustion was conducted based on the indicators of emission,temperature,and economy.On this basis,the comprehensive performance indexes of the system composed of different premixed fuels were evaluated.The results obtained indicate that with the increase in the hydrogen volume ratio in premixed fuel 1,NO_(X) emissions will gradually increase.Moreover,with the increase in the hydrogen volume ratio in premixed fuel 2,CO emissions will gradually decrease.Because premixed fuel 2 contains more hydrogen than premixed fuel 1,CO emissions are reduced by 9.39%and 16.72%as compared with the NG system when the volume ratio of NG to hydrogen is 95∶5 and 90∶10,but the NO emissions of the latter are beyond the acceptable range.Finally,the overall performance is good when the volume ratio of NG to hydrogen is 95∶5,and the volume ratio of NG to syngas to hydrogen is 90∶5∶5.展开更多
In this study, monoglycidyl silyl etherated eugenol(GSE) was synthesized as reactive epoxy diluent, and the chemical structure of GSE, intermediates, and products were characterized by Fourier transform infrared spect...In this study, monoglycidyl silyl etherated eugenol(GSE) was synthesized as reactive epoxy diluent, and the chemical structure of GSE, intermediates, and products were characterized by Fourier transform infrared spectroscopy(FTIR) and nuclear magnetic resonance(~1 H-NMR). GSE existed as a potential bio-based reactive diluent for petroleum-based epoxy resin. The curing kinetics of EP/HHPA/GSE system was studied by non-isothermal DSC method. The kinetics parameters were calculated by using the Kissinger model, Crane model, Ozawa model, and β-T(temperature-heating rate) extrapolation, respectively. In addition, the effects of GSE on the thermo-mechanical properties and thermal stability of EP/HHPA/GSE systems were studied, indicating that GSE can effectively improve the toughness and thermal decomposition temperature of the epoxy system.展开更多
Circulating fluidized bed combustion （CFBC） ash can be used as supplementary cementitious material for concrete production for its high pozzolanic activity. We investigated the effect of curing conditions on the hyd...Circulating fluidized bed combustion （CFBC） ash can be used as supplementary cementitious material for concrete production for its high pozzolanic activity. We investigated the effect of curing conditions on the hydration and performance of CFBC ash-Portland cement system （30： 70, by mass） including hydration products, paste microstructure, linear expansion ratio, chemically combined water content and compressive strength. The results show that tobermorite rather than ettringite is generated under the condition of autoclaved curing. The expansion and mortar strength of the system cured in water is higher than those cured in air at a given age, and the strength and bulk volume may retract under the condition of air curing. In addition, autoclaved curing facilitates the increase of strength gain at early curing ages （the increase rate lowers down in the following ages） and the improvement of system volume stability. It is suggested that sufficient water is necessary for the curing of CFBC ash cementitious system, and autoclaved curing may be considered where volume stability is a primary concern.展开更多
An octa-functional acrylate of C-tetramethyl calix[4]resorcinarene（CMC-4-RA） was facilely synthesized and characterized with ^1H NMR, ^13C NMR and FTIR spectroscopy. The CMC-4-RA was added to a thiol-acrylate system...An octa-functional acrylate of C-tetramethyl calix[4]resorcinarene（CMC-4-RA） was facilely synthesized and characterized with ^1H NMR, ^13C NMR and FTIR spectroscopy. The CMC-4-RA was added to a thiol-acrylate system with different mass ratios, and exposed to a middle pressure mercury lamp. The maximum photopolymerization rate and final vinyl group conversion in the cured film increased greatly along with CMC-4-RA addition that was monitored with Photo-DSC. The tensile strength and pendulum hardness were improved significantly after the addition of CMC-4-RA. With increasing the content of CMC-4-RA to 60%（mass fraction）, the glass transition temperature increased from 34.2 ℃ to 84.1 ℃; the cross-link density was calculated to be increased from 23.83 mmol/cm^3 to 82.40 mmol/cm^3 according to dynamic mechanical thermal analysis; the thermostability was greatly improved.展开更多
To overcome reliance on molds and the difficulty of fabricating complex geometries with traditional C/C composites,direct ink writing(DIW)with UV/heat dual curing was employed to produce high-performance C/C composite...To overcome reliance on molds and the difficulty of fabricating complex geometries with traditional C/C composites,direct ink writing(DIW)with UV/heat dual curing was employed to produce high-performance C/C composites.The rheological properties of the composite inks were systematically analyzed to assess the effects of phenolic resin(PR)and carbon fiber(CF)content.Results show pronounced shear-thinning behavior and strong thixotropy-both essential for stable DIW.Additionally,UV/heat curing behavior was characterized to provide theoretical insights for optimizing curing parameters.Notably,CF addition is found to significantly attenuate UV light penetration compared to pure PR.As CF content increases,the critical UV irradiation energy rises sharply from 68.47 to 911.19 mJ/cm^(2),necessitating precise adjustments to curing parameters.Preforms were pyrolyzed in a carbon tube furnace to examine pore-formation characteristics,and chemical vapor infiltration(CVI)was applied to filling the resulting pores,yielding C/C composites with a flexural strength of 115.19 MPa.展开更多
[2-(3,4-epoxy-cyclohexyl)ethyl]dimethyltert-butylsilane was synthesized,using tert-butyldimethylsilane(TBDMS)and 1,2-epoxy-4-vinylcyclohexane(EVC)as the main raw materials and tris(triphenylphosphine)chlororhodium(I)[...[2-(3,4-epoxy-cyclohexyl)ethyl]dimethyltert-butylsilane was synthesized,using tert-butyldimethylsilane(TBDMS)and 1,2-epoxy-4-vinylcyclohexane(EVC)as the main raw materials and tris(triphenylphosphine)chlororhodium(I)[RhCl(Ph3P)3]as the catalyst.[2-(3,4-epoxy-cyclohexyl)ethyl]dimethyltert-butylsilane is a novel kind of silicon-containing epoxide.The factors affecting the reaction yield,such as catalyst use,reaction time and reaction temperature,were investigated,and the synthesized product was characterized and analyzed by FT-IR and 1H-NMR.A series of amine-curing resins were prepared with[2-(3,4-epoxy-cyclohexyl)ethyl]dimethyltert-butylsilane,bisphenol A epoxy resin(E-51)and modified amine(593 amine).The mechanical properties of cured splines with the different proportions of amine-curing resins were tested.When the content of 593 amine was 20%,the content of E-51 was 75%and the amount of[2-(3,4-epoxy-cyclohexyl)ethyl]dimethyltert-butylsilane was 5%,the mechanical properties of the cured splines were the best with the tensile strength being 23.3 MPa,the elongation at break being 7.8%,and the Young's modulus being 421.3 MPa.展开更多
To address the negative impact of an internal curing agent on strength while preserving its ability to resist autogenous shrinkage,we investigated the incorporation of triethanolamine and triisopropanolamine as early-...To address the negative impact of an internal curing agent on strength while preserving its ability to resist autogenous shrinkage,we investigated the incorporation of triethanolamine and triisopropanolamine as early-strength components.These additives were combined with an internal curing agent to prepare a compound early-strength internal curing agent so as to investigate how compound early-strength internal curing agents affect the mechanical characteristics and volume stability of mortar.This was assessed using a battery of tests,including strength,autogenous shrinkage,internal relative humidity,mercury intrusion porosimetry,X-ray powder diffraction,and scanning electron microscopy.These results indicate that the compound early-strength internal curing agent effectively maintains the volume stability of the mortar without compromising its early mechanical properties.The compressive strength ratios of the mortar mixed with the compound early-strength internal curing agent were 109.45% at 3 days and 119% at 7 days,indicating significant improvement compared with the internal curing agent.Furthermore,the 7-day autogenous shrinkage rate of the mortar was-56.78μm/m.The proportion of hazardous-grade pores larger than 100 nm was reduced to 3.54%,and the pore distribution was uniform.This study introduces innovative ideas and methods for mitigating the adverse effects of internal curing agents on the early strength of mortar.展开更多
The size effects were experimentally investigated and the underlying mechanism was analyzed.The results reveal that,as the specimen size increases,the interconnectivity of macropores slightly decreases.This in turn co...The size effects were experimentally investigated and the underlying mechanism was analyzed.The results reveal that,as the specimen size increases,the interconnectivity of macropores slightly decreases.This in turn constrains the diffusion of CO_(2) and moisture in the specimens,resulting in an increase in the discrepancy between the internal and external carbonation degrees.An increase in cement paste thickness simultaneously decreases the quantity,average size,and interconnectivity of macropores,lowering the diffusion efficacy of CO_(2) and moisture and exacerbating the overall heterogeneity in carbonation.Moreover,the gradual blockage of macropores leads to the emergence of localized ‘occluded zones’ with much lower carbonation degree.The reduction in aggregate size significantly alters the average diameter and connectivity of macropores,leading to notable change to overall non-uniformity.This study provides insight into improving the CO_(2) curing effect of pervious concrete products and developing uniform curing methods.展开更多
Using solid waste as a substitute for conventional cement has become an important way to reduce carbon emissions.This paper attempted to utilize steel slag(SS)and fly ash(FA)as supplementary cementitious material by u...Using solid waste as a substitute for conventional cement has become an important way to reduce carbon emissions.This paper attempted to utilize steel slag(SS)and fly ash(FA)as supplementary cementitious material by utilizing CO_(2)mineralization curing technology.This study examined the dominant and interactive influences of the residual water/cement ratio,CO_(2)pressure,curing time,and SS content on the mechanical properties and CO_(2)uptake rate of CO_(2)mineralization curing SS-FA-Portland cement ternary paste specimens.Additionally,microstructural development was analyzed.The findings demonstrated that each factor significantly affected compressive strength and CO_(2)uptake rate,with factor interactions becoming more pronounced at higher SS dosages(>30%),lower residual water/cement ratios(0.1-0.15),and CO_(2)pressures of 0.1-0.3 MPa.Microscopic examinations revealed that mineralization primarily yielded CaCO_(3)and silica gel.The residual w/c ratio and SS content significantly influenced the CaCO_(3)content and crystallinity of the mineralization products.Post-mineralization curing,the percentage of pores larger than 50 nm significantly decreased,the proportion of harmless pores smaller than 20 nm increased,and pore structure improved.This study also found that using CO_(2)mineralization curing SS-FA-Portland cement solid waste concrete can significantly reduce the negative impact on the environment.展开更多
[Objective]The aim was to explore effects of curing technique parameters on chemical components and aromatic material accumulation to formulate a suitable curing technique and for and to achieve tobacco scalding, dryi...[Objective]The aim was to explore effects of curing technique parameters on chemical components and aromatic material accumulation to formulate a suitable curing technique and for and to achieve tobacco scalding, drying and giving aromat- ic flavor. [Method] With tobacco variety KRK 26 as test materials, the test involved parameters of three curing-techniques in down, middle and upper parts of flue-cured tobaccos in an oven to measure chemical components and aromatic substances in tobaccos. [Result] The effects of curing techniques on total sugar and reducing sug- ar differed upon temperature and humidity. The contents of chemical components, such as total alkaloid, total N and the ratio of sugar/ alkali by moderate temperature and high humidity technique were of significant differences with those by moderate temperature and moderate humidity technique and with low temperature and low hu- midity technique; the chemical components by moderate temperature and moderate humidity were of insignificant differences with the treatment by low temperature and low humidity technique. Total amount of aroma components by different curing tech- niques from high to low was the treatment by low temperature and low humidity technique （461.72 μg/g）, the treatment by moderate temperature and moderate hu- midity technique （450.06μg/g） and the treatment by moderate temperature and high humidity technique （385.12μg/g）, suggesting the content of aromatic substances is high at low temperature and low humidity. [Conclusion] Moderate temperature and high humidity curing technique has significant effects on total alkaloid, total N and the ratio of sugar/ alkali of tobaccos and different curing techniques also affect the total amount of aromatic substances of flue-cured tobaccos.展开更多
To compare the efficacy and safety of fidaxomicin and vancomycin for the treatment of patients with Clostridium difficile infection （CD1）, randomized controlled trials （RCTs） of fidaxomicin versus vancomycin for t...To compare the efficacy and safety of fidaxomicin and vancomycin for the treatment of patients with Clostridium difficile infection （CD1）, randomized controlled trials （RCTs） of fidaxomicin versus vancomycin for the treatment of CDI published in Pubmed, Embase, Web of Science and the Cochrane library were searched. Two reviewers independently extracted the data. The primary outcome was the rates of clinical cure. The secondary endpoints were the rates of CDI recurrence in the 4 weeks period after the end of therapy and rates of global cure, adverse events. Meta-analysis was performed using the Mantle-Haenszel fixed effect method （FEM）. Odds ratios （ORs） with 95% confidence intervals （95% CIs） were reported. The results indicated that two large randomized controlled trials were included in the meta-analysis. Clinical cure with fidaxomicin was similar to with vancomycin both in the modified intention to treat （OR = 1.17, 95% CI 0.82-1.66, P = 0.40） and in the per-protocol population （OR = 1.24, 95% CI 0.80-1.92, P = 0.34）. There were no significant differences in the rates of clinical cure between fidaxomicin and vancomycin in the subgroups analyzed by age, patients＇ status, and previous CDI, infection with B 1 strain, severity baseline, and exposure to concomitant antibiotics. Recurrence of CDI was significantly less common among fidaxomicin-treated patients compared with vancomycin-treated patients both in the modified intention-to-treat population （OR = 0.47, 95% CI 0.34-0.65, P〈0.00001） and in the per-protocol population （OR = 0.45, 95% CI 0.31-0.62, P〈0.0001）. Treatment with fidaxomicin compared with vancomycin was associated with significantly higher rates of global cure both in the modifed intention-to-treat population （OR = 1.75, 95% CI 1.35-2.27, P〈0.0001） and in the per-protocol population （OR = 1.86, 95% CI 1.40-2.47, P〈0.0001）. Our recta-analysis suggests that fidaxomicin is not superior to vancomycin in rates of clinical cure, while fidaxomicin significantly decreases the rates of CDI recurrence and significantly improves the rates of global cure compared with vancomycin. Thus, fidaxomicin is a promising candidate for treatment of the CDI, especially in decreasing the rates of CDI recurrence and improving the rates of global cure.展开更多
Curing of Bacillus subtilis plasmid using sodium dodecyl sulfate (SDS)was studied in order to obtain a host strain. An overnight culture of Bacillus subtilis 24/pMX45 was used to inoculate fresh LB containing SDS (0-0...Curing of Bacillus subtilis plasmid using sodium dodecyl sulfate (SDS)was studied in order to obtain a host strain. An overnight culture of Bacillus subtilis 24/pMX45 was used to inoculate fresh LB containing SDS (0-0.008%). No growth of 24/pMX45 was observed when LB contained an SDS concentration of 0.006% or greater, and the sublethal concentration (w/v) of SDS was 0.005% with a killing rate of 99%. Samples were diluted and plated on LB agar, individual colonies were randomly picked to a selective agar medium by tooth to screen for loss of plasmid-encoded erythomycin resistance. CsCl-EtBr gradient centrifugation and plasmid DNA profile demonstrated that plasmid-cured derivative A7 has completely lost its plasmid. A7 had a shorter lag, and its cell concentration was consistently higher than that of the 24/pMX45. Elimination of the plasmid was first observed after 24/pMX45 had been treated with SDS for 8 h. The percent elimination then continued to increase until about 22 h, after which the fraction of cured cell in the population remained constant. Plasmid cured cell numbers were measured in a separate control culture of 24/pMX45 untreated by SDS. No spontaneous loss of pMX45 was observed after 24/pMX45 were incubated for 24 h and 48 h with shaking at 37 ℃.These results suggested that SDS can be used as curing agent to eliminate the plasmid of Bacillus subtilis.展开更多
[Objective] The aim was to compare effects of three curing techniques （Chinese tobacco curing-method for improving tobacco quality and fragrance, Chi-nese （three-phase） tobacco curing technique, and Zimbabwe tobac...[Objective] The aim was to compare effects of three curing techniques （Chinese tobacco curing-method for improving tobacco quality and fragrance, Chi-nese （three-phase） tobacco curing technique, and Zimbabwe tobacco curing tech-nique） on quality of tobacco and to select optimal curing method. [Method] In Peng-shui county in Chongqing, tobacco variety K326 was chosen as test materials to conduct tobacco curing tests as per three techniques to analyze key components of raw tobacco, grade quality and evaluation quality. [Result] The content of starch in tobacco was reduced by Chinese tobacco curing-method for improving tobacco quality and fragrance, and the ratio of middle and high quality grade tobaccos improved by 1.8%-7.95%; average price increased by 1.64-3.21 yuan/kg; evaluation grade grew by 1.5-4.4. The technique is proved in enhancing tobacco fragrance quality and quantity as wel as improving and adjusting fragrance, taste and flavor. [Conclusion] Chinese （three-phase） tobacco curing technique improves tobacco quality and provides references for production demonstration areas of tobacco curing.展开更多
The research investigated application effects of alcohol-based fuels in in- tensive curing. The results showed that alcohol-based fuels allow flexible adjustment of temperature and heat supplying. What＇s more, in tre...The research investigated application effects of alcohol-based fuels in in- tensive curing. The results showed that alcohol-based fuels allow flexible adjustment of temperature and heat supplying. What＇s more, in treatment A, the cured tobac- cos are softer and brighter, with more oil content and higher proportion of first-class tobaccos. Per leaf weight increased by 0.13 g and output value per kang （a heat- able brick bed） deducting energy cost grew by 188.66 yuan. In addition, the con- tents of reducing sugar and potassium enhanced within the ranges of high-quality tobacco, and chemical components are more coordinated.展开更多
[Objective]This study aimed to optimize the conditions for curing tobacco leaf, so as to improve its flavor and quality. [Method] Leaves of Yuanyan 87 were col ected and cured by three different techniques （moderate-...[Objective]This study aimed to optimize the conditions for curing tobacco leaf, so as to improve its flavor and quality. [Method] Leaves of Yuanyan 87 were col ected and cured by three different techniques （moderate-intensity conditions throughout the curing course; high-intensity conditions at leaf yel owing and wilting stages, moderate-intensity conditions at leaf drying and vein drying stages; high-in-tensity conditions throughout the curing course）, and then the contents of 48 aroma substances and taste indices of the finished tobacco leaves were measured. [Result] The contents of 28 aroma substances in the tobacco leaves cured under high-inten-sity conditions throughout the course were higher and the taste indices of these to-bacco leaves were better, compared with those flue-cured by the other two tech-niques. The contents of the other 20 aroma substances were not significantly af-fected by the curing techniques. The second best technique was high-intensity con-ditions at leaf yel owing and wilting stages and moderate-intensity conditions at leaf drying and vein drying stages. Curing tobacco leaves at moderate-intensity condi-tions throughout the course was the worst one. [Conclusion] Compared with the oth-er two methods, the contents of aroma substances and taste indices of the tobacco leaves cured under high-intensive conditions throughout the course were the best.展开更多
Four mineral admixture concrete specimens werefabricated to study the negative effect improvements ofaccelerated curing on the chloride penetration resistance ofordinary concrete. After reaching different initial stre...Four mineral admixture concrete specimens werefabricated to study the negative effect improvements ofaccelerated curing on the chloride penetration resistance ofordinary concrete. After reaching different initial strengths, the specimens were placed in 40, 60, or 80 t water tanks foraccelerated curing. The Coulomb values of the specimens weemeasured with ASTM C1202 experiment at 28, 100, 200, ad300 d. Partial specimens were also selected for rapid chlorideion migration coefficient and mercury intrusion porosimetryexperiments. The experimental results show that theaccelerated curing for ordinary concrete linealy deterioratesthe chloride penetration resistance, whereas the incorporationof mineral admixtures improves the concrete microscopic pore-structures and negative effects. An upper temperature limit of60 t of the accelerated curing is suitable for obtainingsuperior chloride penetration resistance for the mineraladmixture concrete. Pre-curing at a normal temperature of 20t is beneficial for improving the negative effect, which isalso aieviated with increasing testing age as a result of thesuccessive hydration of binder materials in concrete.展开更多
基金Funded by the Science and Technology Foundation of Beijing Municipal Education Commission (KM200410016004)
文摘The effects of different curing systems on the properties of high volume fine mineral powder RPC （reactive powder concrete） and the appearances of hydrates were studied. The experimental results show that dry-heating curing promotes the development of pozzolanic reactivity of fine mineral powder; due to low cement content, 0.20 water-bind ratio and high reactive fine mineral powder content, the strength of RPC increases by around 200% after steam curing and subsequent dry-heating curing. Scanning electron microscopy and energy spectrum diagram showed that： after the high volume fine mineral powder RPC with 0.16 water-bind ratio underwent steam curing and dry-heating curing, there was no significant change in the appearance of hydrates; after the RPC with 0.20 water-bind ratio, the cement content of 150 kg/m3 and more steel slag powder underwent dry-heating curing, there was a certain change in the appearance of C-S-H, the structure of gel was more compact and was uniformly distributed, and the Ca/Si of C-S-H gel decreased from 1.41 to around 1.20.
基金Funded by the National Natural Science Foundation of China(No.51972047)。
文摘The crystal structure and morphology of the mineralization products were studied by scanning electron microscopy(SEM)and X-ray diffraction(XRD),and the thermal properties were studied by thermogravimetric-differential scanning calorimetry(DSC)analysis.The changes of microorganism quantity and enzyme activity in pore solution with time were measured.The experimental results show that microorganism quantity and enzyme activity in pore solution reach the maximum at 50-60 h,mineralization curing begins at this time,the strength of microbial mineralized steel slag reaches the maximum.This study provides a good selection basis for selecting the optimum mineralization system for the production of microbial mineralized steel slag products.Bacterial mineralization can accelerate the rate of carbon sequestration in the mineralization process.The compressive strength of steel slag with 1.5% bacterial can reach up to 55.6 MPa.The microstructure and thermal properties of calcium carbonate precipitate induced by the enzymes of bacillus subtilis differs from the chemical precipitation in pore solution of steel slag.Through the analysis of the mineralized products of steel slag,the reaction rate of free calcium oxide and free magnesium oxide in steel slag after the addition of microorganisms is significantly increased,which improves the stability of steel slag as cementitious material.Meanwhile,the production of calcium carbonate,the main mineralized product,is significantly increased.
基金National Natural Science Foundations of China(Nos.51478120,U1305245)
文摘High durability and high tensile strength makes ultra-high performance concrete( UHPC) an ideal material for bridges,while its early shrinkage in the construction of cast-in-situ mass concrete leads structure crack-easily,which restricts the application of UHPC in deck system. Whether reasonable amount of coarse aggregate can influence the strength of UHPC and improve the shrinkage performance or reduce the cost is still in doubt. Besides,in order to improve its constructability and workability, whether autoclaved curing system of UHPC can be changed remains to be further researched. In response to these circumstances, a systematic experimental study on the strength of UHPC mixed with coarse aggregate in different ratios has been presented in this paper. The three curing systems,namely standard curing,180-200 ℃/1. 1 MPa autoclaved curing,and hot water curing were tested to reveal the relationship between UHPC's properties and curing systems,and the UHPC ' s microstructure was also preliminarily studied by scanning electron microscope( SEM). The experimental research can draw the following conclusions. Under the condition of the same mix ratio, autoclaved curing guarantees the highest compressive strength,followed by hot water curing and standard curing. The compressive strength of concrete increases with the temperature in the range of 25 to 90 ℃ hot water curing,and high temperature in precuring period can speed up the strength development of UHPC,but the sequence of precuring period does not obviously affect the results. In 90 ℃ hot water and autoclaved curing,the strength is over 150 MPa,and it has little relation with gravel ratio. While the value increases first and then decreases in a lower temperature curing with the increasing of gravel amount,even only about 80 MPa at room temperature. The strength increases moderately along with the increase of the curing age by standard curing,especially in the initial stage.
基金This project was supported by the National Natural Science Foundation of China(59633110 and 59773007)
文摘By using diphenyliodonium salts with different counterions as photo acid generators (PAGs), the effect of acidity on ring-opening polymerization of epoxy monomers and polycondensation of polyol with hexamethoxymethyl melamine (HMMM) was studied. The result shows that the rate of ring-opening polymerization is evidently dependent on the acidity of the acid and strong photo-generated acid is required. However, there is a leveling effect in the polycondensation system; if the photo-generated acid is stronger than protonated HMMM, the acidity does not obviously affect the polycondensation rate.
基金National Key Research and Development Program of China(No.2019YFE0100100-08).
文摘To address the energy shortage and meet the requirements of environmental protection policies,the feasibility of premixed fuel 1(natural gas(NG),syngas,and hydrogen)and premixed fuel 2(NG and hydrogen)in the tobacco curing system was studied.First,according to the law of conservation of energy and mass,a tobacco leaf curing system model was established.Then,the interchangeability index of the premixed fuels was analyzed,and their volume ratios were obtained.Finally,a numerical simulation analysis of the premixed fuel combustion was conducted based on the indicators of emission,temperature,and economy.On this basis,the comprehensive performance indexes of the system composed of different premixed fuels were evaluated.The results obtained indicate that with the increase in the hydrogen volume ratio in premixed fuel 1,NO_(X) emissions will gradually increase.Moreover,with the increase in the hydrogen volume ratio in premixed fuel 2,CO emissions will gradually decrease.Because premixed fuel 2 contains more hydrogen than premixed fuel 1,CO emissions are reduced by 9.39%and 16.72%as compared with the NG system when the volume ratio of NG to hydrogen is 95∶5 and 90∶10,but the NO emissions of the latter are beyond the acceptable range.Finally,the overall performance is good when the volume ratio of NG to hydrogen is 95∶5,and the volume ratio of NG to syngas to hydrogen is 90∶5∶5.
基金the financial support provided by "One Hundred Talented People" of the Chinese Academy of Sciences–China (No. Y60707WR04)Natural Science Foundation of Zhejiang Province (No. Y16B040008)
文摘In this study, monoglycidyl silyl etherated eugenol(GSE) was synthesized as reactive epoxy diluent, and the chemical structure of GSE, intermediates, and products were characterized by Fourier transform infrared spectroscopy(FTIR) and nuclear magnetic resonance(~1 H-NMR). GSE existed as a potential bio-based reactive diluent for petroleum-based epoxy resin. The curing kinetics of EP/HHPA/GSE system was studied by non-isothermal DSC method. The kinetics parameters were calculated by using the Kissinger model, Crane model, Ozawa model, and β-T(temperature-heating rate) extrapolation, respectively. In addition, the effects of GSE on the thermo-mechanical properties and thermal stability of EP/HHPA/GSE systems were studied, indicating that GSE can effectively improve the toughness and thermal decomposition temperature of the epoxy system.
基金Funded by the National Natural Science Foundation of China(Nos.51132010 and 51272222)the Programs for Science and Technology Development of Yantai City,Shandong Province,China(No.2012ZH249)
文摘Circulating fluidized bed combustion （CFBC） ash can be used as supplementary cementitious material for concrete production for its high pozzolanic activity. We investigated the effect of curing conditions on the hydration and performance of CFBC ash-Portland cement system （30： 70, by mass） including hydration products, paste microstructure, linear expansion ratio, chemically combined water content and compressive strength. The results show that tobermorite rather than ettringite is generated under the condition of autoclaved curing. The expansion and mortar strength of the system cured in water is higher than those cured in air at a given age, and the strength and bulk volume may retract under the condition of air curing. In addition, autoclaved curing facilitates the increase of strength gain at early curing ages （the increase rate lowers down in the following ages） and the improvement of system volume stability. It is suggested that sufficient water is necessary for the curing of CFBC ash cementitious system, and autoclaved curing may be considered where volume stability is a primary concern.
基金Supported by the National Natural Science Foundation of China(No.50233030)Granted by China NKBRSF Project (No.2001CB409600)
文摘An octa-functional acrylate of C-tetramethyl calix[4]resorcinarene（CMC-4-RA） was facilely synthesized and characterized with ^1H NMR, ^13C NMR and FTIR spectroscopy. The CMC-4-RA was added to a thiol-acrylate system with different mass ratios, and exposed to a middle pressure mercury lamp. The maximum photopolymerization rate and final vinyl group conversion in the cured film increased greatly along with CMC-4-RA addition that was monitored with Photo-DSC. The tensile strength and pendulum hardness were improved significantly after the addition of CMC-4-RA. With increasing the content of CMC-4-RA to 60%（mass fraction）, the glass transition temperature increased from 34.2 ℃ to 84.1 ℃; the cross-link density was calculated to be increased from 23.83 mmol/cm^3 to 82.40 mmol/cm^3 according to dynamic mechanical thermal analysis; the thermostability was greatly improved.
基金supported by State Key Laboratory of Powder Metallurgy,Central South University,Changsha,China.
文摘To overcome reliance on molds and the difficulty of fabricating complex geometries with traditional C/C composites,direct ink writing(DIW)with UV/heat dual curing was employed to produce high-performance C/C composites.The rheological properties of the composite inks were systematically analyzed to assess the effects of phenolic resin(PR)and carbon fiber(CF)content.Results show pronounced shear-thinning behavior and strong thixotropy-both essential for stable DIW.Additionally,UV/heat curing behavior was characterized to provide theoretical insights for optimizing curing parameters.Notably,CF addition is found to significantly attenuate UV light penetration compared to pure PR.As CF content increases,the critical UV irradiation energy rises sharply from 68.47 to 911.19 mJ/cm^(2),necessitating precise adjustments to curing parameters.Preforms were pyrolyzed in a carbon tube furnace to examine pore-formation characteristics,and chemical vapor infiltration(CVI)was applied to filling the resulting pores,yielding C/C composites with a flexural strength of 115.19 MPa.
基金Funded by the National Natural Science Foundation of China(No.21865017)。
文摘[2-(3,4-epoxy-cyclohexyl)ethyl]dimethyltert-butylsilane was synthesized,using tert-butyldimethylsilane(TBDMS)and 1,2-epoxy-4-vinylcyclohexane(EVC)as the main raw materials and tris(triphenylphosphine)chlororhodium(I)[RhCl(Ph3P)3]as the catalyst.[2-(3,4-epoxy-cyclohexyl)ethyl]dimethyltert-butylsilane is a novel kind of silicon-containing epoxide.The factors affecting the reaction yield,such as catalyst use,reaction time and reaction temperature,were investigated,and the synthesized product was characterized and analyzed by FT-IR and 1H-NMR.A series of amine-curing resins were prepared with[2-(3,4-epoxy-cyclohexyl)ethyl]dimethyltert-butylsilane,bisphenol A epoxy resin(E-51)and modified amine(593 amine).The mechanical properties of cured splines with the different proportions of amine-curing resins were tested.When the content of 593 amine was 20%,the content of E-51 was 75%and the amount of[2-(3,4-epoxy-cyclohexyl)ethyl]dimethyltert-butylsilane was 5%,the mechanical properties of the cured splines were the best with the tensile strength being 23.3 MPa,the elongation at break being 7.8%,and the Young's modulus being 421.3 MPa.
基金Funded by the Guangxi Key Research and Development Program(No.GK AB19259008)the Director's Fund of Key Laboratory of Non-ferrous Metals and Materials Processing New Technology of Ministry of Education(No.22AA-6)。
文摘To address the negative impact of an internal curing agent on strength while preserving its ability to resist autogenous shrinkage,we investigated the incorporation of triethanolamine and triisopropanolamine as early-strength components.These additives were combined with an internal curing agent to prepare a compound early-strength internal curing agent so as to investigate how compound early-strength internal curing agents affect the mechanical characteristics and volume stability of mortar.This was assessed using a battery of tests,including strength,autogenous shrinkage,internal relative humidity,mercury intrusion porosimetry,X-ray powder diffraction,and scanning electron microscopy.These results indicate that the compound early-strength internal curing agent effectively maintains the volume stability of the mortar without compromising its early mechanical properties.The compressive strength ratios of the mortar mixed with the compound early-strength internal curing agent were 109.45% at 3 days and 119% at 7 days,indicating significant improvement compared with the internal curing agent.Furthermore,the 7-day autogenous shrinkage rate of the mortar was-56.78μm/m.The proportion of hazardous-grade pores larger than 100 nm was reduced to 3.54%,and the pore distribution was uniform.This study introduces innovative ideas and methods for mitigating the adverse effects of internal curing agents on the early strength of mortar.
基金Funded by the National Natural Science Foundation of China (No.22203066)the 6th Young Elite Scientist Sponsorship Program by China Association for Science and Technology (No.2020QNRC001)。
文摘The size effects were experimentally investigated and the underlying mechanism was analyzed.The results reveal that,as the specimen size increases,the interconnectivity of macropores slightly decreases.This in turn constrains the diffusion of CO_(2) and moisture in the specimens,resulting in an increase in the discrepancy between the internal and external carbonation degrees.An increase in cement paste thickness simultaneously decreases the quantity,average size,and interconnectivity of macropores,lowering the diffusion efficacy of CO_(2) and moisture and exacerbating the overall heterogeneity in carbonation.Moreover,the gradual blockage of macropores leads to the emergence of localized ‘occluded zones’ with much lower carbonation degree.The reduction in aggregate size significantly alters the average diameter and connectivity of macropores,leading to notable change to overall non-uniformity.This study provides insight into improving the CO_(2) curing effect of pervious concrete products and developing uniform curing methods.
基金Project(52479115)supported by the National Natural Science Foundation of ChinaProject(2024SF-YBXM-615)supported by the Key Research and Development Program of Shaanxi Province,China+1 种基金Project(2022943)supported by the Youth Innovation Team of Shaanxi Universities,ChinaProject(300102283721)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Using solid waste as a substitute for conventional cement has become an important way to reduce carbon emissions.This paper attempted to utilize steel slag(SS)and fly ash(FA)as supplementary cementitious material by utilizing CO_(2)mineralization curing technology.This study examined the dominant and interactive influences of the residual water/cement ratio,CO_(2)pressure,curing time,and SS content on the mechanical properties and CO_(2)uptake rate of CO_(2)mineralization curing SS-FA-Portland cement ternary paste specimens.Additionally,microstructural development was analyzed.The findings demonstrated that each factor significantly affected compressive strength and CO_(2)uptake rate,with factor interactions becoming more pronounced at higher SS dosages(>30%),lower residual water/cement ratios(0.1-0.15),and CO_(2)pressures of 0.1-0.3 MPa.Microscopic examinations revealed that mineralization primarily yielded CaCO_(3)and silica gel.The residual w/c ratio and SS content significantly influenced the CaCO_(3)content and crystallinity of the mineralization products.Post-mineralization curing,the percentage of pores larger than 50 nm significantly decreased,the proportion of harmless pores smaller than 20 nm increased,and pore structure improved.This study also found that using CO_(2)mineralization curing SS-FA-Portland cement solid waste concrete can significantly reduce the negative impact on the environment.
基金Supported by China National Tobacco Corporation General Project(〔2012〕122)Chongqing Branch Company S&T Project of China National Tobacco Corporation(NY20110601070010)~~
文摘[Objective]The aim was to explore effects of curing technique parameters on chemical components and aromatic material accumulation to formulate a suitable curing technique and for and to achieve tobacco scalding, drying and giving aromat- ic flavor. [Method] With tobacco variety KRK 26 as test materials, the test involved parameters of three curing-techniques in down, middle and upper parts of flue-cured tobaccos in an oven to measure chemical components and aromatic substances in tobaccos. [Result] The effects of curing techniques on total sugar and reducing sug- ar differed upon temperature and humidity. The contents of chemical components, such as total alkaloid, total N and the ratio of sugar/ alkali by moderate temperature and high humidity technique were of significant differences with those by moderate temperature and moderate humidity technique and with low temperature and low hu- midity technique; the chemical components by moderate temperature and moderate humidity were of insignificant differences with the treatment by low temperature and low humidity technique. Total amount of aroma components by different curing tech- niques from high to low was the treatment by low temperature and low humidity technique （461.72 μg/g）, the treatment by moderate temperature and moderate hu- midity technique （450.06μg/g） and the treatment by moderate temperature and high humidity technique （385.12μg/g）, suggesting the content of aromatic substances is high at low temperature and low humidity. [Conclusion] Moderate temperature and high humidity curing technique has significant effects on total alkaloid, total N and the ratio of sugar/ alkali of tobaccos and different curing techniques also affect the total amount of aromatic substances of flue-cured tobaccos.
文摘To compare the efficacy and safety of fidaxomicin and vancomycin for the treatment of patients with Clostridium difficile infection （CD1）, randomized controlled trials （RCTs） of fidaxomicin versus vancomycin for the treatment of CDI published in Pubmed, Embase, Web of Science and the Cochrane library were searched. Two reviewers independently extracted the data. The primary outcome was the rates of clinical cure. The secondary endpoints were the rates of CDI recurrence in the 4 weeks period after the end of therapy and rates of global cure, adverse events. Meta-analysis was performed using the Mantle-Haenszel fixed effect method （FEM）. Odds ratios （ORs） with 95% confidence intervals （95% CIs） were reported. The results indicated that two large randomized controlled trials were included in the meta-analysis. Clinical cure with fidaxomicin was similar to with vancomycin both in the modified intention to treat （OR = 1.17, 95% CI 0.82-1.66, P = 0.40） and in the per-protocol population （OR = 1.24, 95% CI 0.80-1.92, P = 0.34）. There were no significant differences in the rates of clinical cure between fidaxomicin and vancomycin in the subgroups analyzed by age, patients＇ status, and previous CDI, infection with B 1 strain, severity baseline, and exposure to concomitant antibiotics. Recurrence of CDI was significantly less common among fidaxomicin-treated patients compared with vancomycin-treated patients both in the modified intention-to-treat population （OR = 0.47, 95% CI 0.34-0.65, P〈0.00001） and in the per-protocol population （OR = 0.45, 95% CI 0.31-0.62, P〈0.0001）. Treatment with fidaxomicin compared with vancomycin was associated with significantly higher rates of global cure both in the modifed intention-to-treat population （OR = 1.75, 95% CI 1.35-2.27, P〈0.0001） and in the per-protocol population （OR = 1.86, 95% CI 1.40-2.47, P〈0.0001）. Our recta-analysis suggests that fidaxomicin is not superior to vancomycin in rates of clinical cure, while fidaxomicin significantly decreases the rates of CDI recurrence and significantly improves the rates of global cure compared with vancomycin. Thus, fidaxomicin is a promising candidate for treatment of the CDI, especially in decreasing the rates of CDI recurrence and improving the rates of global cure.
文摘Curing of Bacillus subtilis plasmid using sodium dodecyl sulfate (SDS)was studied in order to obtain a host strain. An overnight culture of Bacillus subtilis 24/pMX45 was used to inoculate fresh LB containing SDS (0-0.008%). No growth of 24/pMX45 was observed when LB contained an SDS concentration of 0.006% or greater, and the sublethal concentration (w/v) of SDS was 0.005% with a killing rate of 99%. Samples were diluted and plated on LB agar, individual colonies were randomly picked to a selective agar medium by tooth to screen for loss of plasmid-encoded erythomycin resistance. CsCl-EtBr gradient centrifugation and plasmid DNA profile demonstrated that plasmid-cured derivative A7 has completely lost its plasmid. A7 had a shorter lag, and its cell concentration was consistently higher than that of the 24/pMX45. Elimination of the plasmid was first observed after 24/pMX45 had been treated with SDS for 8 h. The percent elimination then continued to increase until about 22 h, after which the fraction of cured cell in the population remained constant. Plasmid cured cell numbers were measured in a separate control culture of 24/pMX45 untreated by SDS. No spontaneous loss of pMX45 was observed after 24/pMX45 were incubated for 24 h and 48 h with shaking at 37 ℃.These results suggested that SDS can be used as curing agent to eliminate the plasmid of Bacillus subtilis.
基金Supported by China National Tobacco Corporation General Project[(2012)No.122]Chongqing Branch Company S&T Project of China National Tobacco Corporation(NY20110601070010)~~
文摘[Objective] The aim was to compare effects of three curing techniques （Chinese tobacco curing-method for improving tobacco quality and fragrance, Chi-nese （three-phase） tobacco curing technique, and Zimbabwe tobacco curing tech-nique） on quality of tobacco and to select optimal curing method. [Method] In Peng-shui county in Chongqing, tobacco variety K326 was chosen as test materials to conduct tobacco curing tests as per three techniques to analyze key components of raw tobacco, grade quality and evaluation quality. [Result] The content of starch in tobacco was reduced by Chinese tobacco curing-method for improving tobacco quality and fragrance, and the ratio of middle and high quality grade tobaccos improved by 1.8%-7.95%; average price increased by 1.64-3.21 yuan/kg; evaluation grade grew by 1.5-4.4. The technique is proved in enhancing tobacco fragrance quality and quantity as wel as improving and adjusting fragrance, taste and flavor. [Conclusion] Chinese （three-phase） tobacco curing technique improves tobacco quality and provides references for production demonstration areas of tobacco curing.
基金Supported by Longyan Tobacco Company S&T Project(2014-18)~~
文摘The research investigated application effects of alcohol-based fuels in in- tensive curing. The results showed that alcohol-based fuels allow flexible adjustment of temperature and heat supplying. What＇s more, in treatment A, the cured tobac- cos are softer and brighter, with more oil content and higher proportion of first-class tobaccos. Per leaf weight increased by 0.13 g and output value per kang （a heat- able brick bed） deducting energy cost grew by 188.66 yuan. In addition, the con- tents of reducing sugar and potassium enhanced within the ranges of high-quality tobacco, and chemical components are more coordinated.
基金Supported by the General Program of Science and Technology Research of ChinaNational Tobacco Corporation[(2012)122]Science and Technology Research Programof Chongqing Branch of China National Tobacco Corporation(NY20110601070010)~~
文摘[Objective]This study aimed to optimize the conditions for curing tobacco leaf, so as to improve its flavor and quality. [Method] Leaves of Yuanyan 87 were col ected and cured by three different techniques （moderate-intensity conditions throughout the curing course; high-intensity conditions at leaf yel owing and wilting stages, moderate-intensity conditions at leaf drying and vein drying stages; high-in-tensity conditions throughout the curing course）, and then the contents of 48 aroma substances and taste indices of the finished tobacco leaves were measured. [Result] The contents of 28 aroma substances in the tobacco leaves cured under high-inten-sity conditions throughout the course were higher and the taste indices of these to-bacco leaves were better, compared with those flue-cured by the other two tech-niques. The contents of the other 20 aroma substances were not significantly af-fected by the curing techniques. The second best technique was high-intensity con-ditions at leaf yel owing and wilting stages and moderate-intensity conditions at leaf drying and vein drying stages. Curing tobacco leaves at moderate-intensity condi-tions throughout the course was the worst one. [Conclusion] Compared with the oth-er two methods, the contents of aroma substances and taste indices of the tobacco leaves cured under high-intensive conditions throughout the course were the best.
基金The National Natural Science Foundation of China(No.51178455)the Transformation Program of Science and Technology Achievements of Jiangsu Province(No.BA2015133)
文摘Four mineral admixture concrete specimens werefabricated to study the negative effect improvements ofaccelerated curing on the chloride penetration resistance ofordinary concrete. After reaching different initial strengths, the specimens were placed in 40, 60, or 80 t water tanks foraccelerated curing. The Coulomb values of the specimens weemeasured with ASTM C1202 experiment at 28, 100, 200, ad300 d. Partial specimens were also selected for rapid chlorideion migration coefficient and mercury intrusion porosimetryexperiments. The experimental results show that theaccelerated curing for ordinary concrete linealy deterioratesthe chloride penetration resistance, whereas the incorporationof mineral admixtures improves the concrete microscopic pore-structures and negative effects. An upper temperature limit of60 t of the accelerated curing is suitable for obtainingsuperior chloride penetration resistance for the mineraladmixture concrete. Pre-curing at a normal temperature of 20t is beneficial for improving the negative effect, which isalso aieviated with increasing testing age as a result of thesuccessive hydration of binder materials in concrete.
