The acid-base buffer characteristics of fulvic acid (FA) and barium fulvate (BaFA)were analyzed. Each share of the sample or model agents (phthalic acid and salicylic acid)were separately mixed into a series of shares...The acid-base buffer characteristics of fulvic acid (FA) and barium fulvate (BaFA)were analyzed. Each share of the sample or model agents (phthalic acid and salicylic acid)were separately mixed into a series of shares of dilute solutions of HCI or NaOH with a series of concentration. The original pH values of the solutions were arranged from 2 to 13.Final balanced pH of each share was measured. The pH changes show that FA and BaFApossess buffer ability, whereas the model agents do not. The tendency of balanced pHvalues was 5.4 for FA and 7.4 for BaFA, whereas the original pH was 4.0-8.5; balancedpH changed little. At room temperature, the maximum buffer capacities were as follows:18.11 mmol hydroxyl per gram FA, 11.25 mmol hydroxyl per gram BaFA, 1.19 mmol protonper gram FA, and 1.45 mmol proton per gram BaFA. Mathematics analysis shows thatlogarithm of buffer capacities of FA and BaFA is linearly dependent on original pH. Compared with BaFA and model agents, it is concluded that FA buffer capacity against hydroxylrelies not only on its acidic groups, BaFA buffer capacity against hydroxyl does not rely onits acidic groups, and FA buffer capacity against proton is not related with its carboxyl andphenolic hydroxyl group. The pH values of FA-water solutions with different concentrationsfrom 1 to 10 grams per liter were measured. Their pH values were slightly affected by itsconcentration. Thus, FA possesses a much stronger buffer ability against water dilutionthan common buffer agent. All the pH values of FA water solutions were very nearby 5.4,just the same as the balanced pH tendency for adding FA.展开更多
Two methods of irrigation,drip,and sprinkler were studied to determine the response of the Javits green roof to irrigation.The control study was dry unirrigated plots.Drip irrigation consisted of irrigation tubes runn...Two methods of irrigation,drip,and sprinkler were studied to determine the response of the Javits green roof to irrigation.The control study was dry unirrigated plots.Drip irrigation consisted of irrigation tubes running through the green roof that would water the soil throughout and sprinkler irrigation used a sprinkler system to irrigate the green roof from above.In all cases,the irrigated roofs had increased the soil moisture,reduced temperatures of both the upper and lower surfaces,reduced growing medium temperatures and reduced air temperatures above the green roof relative to the unirrigated roof.The buffered temperature fluctuations were also studied via air conditioner energy consumption.There was a 28%reduction in air conditioner energy consumption and a 33%reduction in overall energy consumption between dry and irrigated plots.Values of thermal resistance or S were determined for accuracy and for this study,there was little change which is ideal.A series of infra-red and thermal probe measurements were used to determine temperatures in the air and sedum.It was determined that the sprinkler irrigation did a better job than the drip irrigation in keeping cooler temperatures within the green roof.A Mann-Whitney U test was performed to verify the variation in moisture temperatures buffering energy consumption.By getting a p-value<0.05,it indicates that the model is accurate for prediction and medium temperatures were statistically different.展开更多
Heavy oil millisecond gas-phase in-line catalytic dehydrogenation over bifunctional catalysts was adopted to produce low-carbon olefins.In this study,the effect of the uncatalyzed reaction composition and distribution...Heavy oil millisecond gas-phase in-line catalytic dehydrogenation over bifunctional catalysts was adopted to produce low-carbon olefins.In this study,the effect of the uncatalyzed reaction composition and distribution of atmosphere residue(AR)pyrolysis vapor at 650℃ was investigated for the first time.In the pyrolysis vapor,the yield of low-carbon olefins was only 15.2%.The yield of 1-olefin and n-alkanes,which are the primary products of rapid heavy oil pyrolysis,reached approximately 54.0%.To achieve further catalytic dehydrogenation,AR pyrolysis volatiles were catalyzed over single calcium aluminate(C_(12)A_(7)),ZSM-5,and C_(12)A_(7)-ZSM-5(CZ)catalysts at 650℃,which possess different pore structures,and acid-base properties.The ZSM-5 catalyst obtained the highest low-carbon olefin yield after catalytic dehydrogenation of pyrolysis volatiles.Finally,the C_(12)A_(7) and CZ stepwise coupling bifunctional catalysts increased the catalytic activity,and thus increased the higher low-carbon olefin yield but reduced the yields of alkanes and aromatics fraction.Notably,the yields of propylene and butane were important sources of the low-carbon olefins.Thus,heavy oil millisecond gas-phase in-line catalytic dehydrogenation could achieve the maximum conversion of these residues to produce low-carbon olefins.展开更多
The squeezing deformation of surrounding rock is an important factor restricting the safe construction and long-term operation of tunnels when a tunnel passes through soft strata with high ground stress.Under such sof...The squeezing deformation of surrounding rock is an important factor restricting the safe construction and long-term operation of tunnels when a tunnel passes through soft strata with high ground stress.Under such soft rock geological conditions,the large deformation of the surrounding rock can easily lead to the failure of supporting structures,including shotcrete cracks,spalling,and steel arch distortion.To improve the lining support performance during the large deformation of squeezed surrounding rock,this work selects aluminum foam with densities of 0.25 g/cm3,0.42 g/cm3 and 0.61 g/cm3 as the buffer layer material and carries out uniaxial confined compression tests.Through the evaluation and analysis of energy absorption and the comparison of the yield pressure of aluminum foam with those of other cushioning materials and yield pressure support systems,the strength,deformation and energy absorption of aluminum foam with a density of 0.25 g/cm3 meet the yield pressure performance requirements.The numerical model of the buffer layer yielding support system is then established via the finite element analysis software ABAQUS,and the influence of the buffer layer setting on the lining support is analyzed.Compared with the conventional support scheme,the addition of an aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining.The maximum and minimum principal stresses of the primary support are reduced by 13%and 15%,respectively.The maximum and minimum principal stresses of the secondary lining are reduced by 15%and 12%,respectively,and the displacement deformation of the secondary lining position is reduced by 15%.In summary,the application of aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining,improve the stress safety of the support and reduce the deformation of the support.展开更多
The role of forest litter as an acid-base buffering system was assessed by litter from plantation and natural forests in South China. Samples were either extracted with acid solutions or titrated with acid or base sol...The role of forest litter as an acid-base buffering system was assessed by litter from plantation and natural forests in South China. Samples were either extracted with acid solutions or titrated with acid or base solutions. Litter was found to be a strong acid-base buffering system. Two legume species, Acacia mangium Willd and A. auriculaiformis A. Cunn, had very high litter pH values of around 6, which was 2 pH units higher than that of the soil where they grew. Litter of all other plantation species had litter pH of around 4, similar to that of the soil. Both legume species have high potential to neutralize soil acidity and the litter layer could act to shield soil against acid rain. The current stand of two legume species was estimated to be able to raise rain acidity by 0.1 to 0.4 pH units. Inorganic ions did not fully explain the pH pattern of different litter extracts, but high sodium and low nitrate partly accounted for the high pH of the two legume species. Some natural forest species had extremely low pH. As a whole, the litter of the natural climax forest was the driving force of soil acidification. Although plant residues are strong acid-base buffering system and able to adjust acidity of environment, only a few species can be expected to make soil more acid or alkaline through this mechanism since most species have litter pH values similar to those of soil where they grow.展开更多
The dynamic math model of shift clutch in engagement process was determined on the basis of hydraulic buffering valve and shift clutch of a power shift steering transmission. The influence of buffering pressure chara...The dynamic math model of shift clutch in engagement process was determined on the basis of hydraulic buffering valve and shift clutch of a power shift steering transmission. The influence of buffering pressure characteristic on shift clutch engagement process was analyzed. The study results could be used to the characteristics match of the shift clutch with the hydraulic system of the high speed tracked vehicle power shift steering transmission and the performance prediction.展开更多
In this paper, the efficiencies of two production lines, one is with commonly, the other is with separately buffer capacities are compared, the result is that the former one is better than the latter
The effects of soil solid components on soil sensitivity to acid deposition by sequential extraction method were studied. A multiple regression equation of soil sensitivity was set up on the basis of stepwise regressi...The effects of soil solid components on soil sensitivity to acid deposition by sequential extraction method were studied. A multiple regression equation of soil sensitivity was set up on the basis of stepwise regression analysis. The results showed that organic matter expressed dual effects that were decided by soil original pH value and exchangeable cation composition on acid buffering reactions. The hydrolysis of activated oxides was a very important proton buffering reaction when in low pH situation. The crystalline oxides also played a role in the buffering reactions, but the role was restricted by the rate of activation of oxides. Meanwhile, the results by stepwise analysis showed that factors that had significant effect on soil acid buffering capacity were content of montmorillite, soil original pH value, Al 0, Mn 0 and CEC in decreasing order. Finally, sixteen soils were classified into four types of sensitive with single index cluster and multiple fuzzy cluster analysis respectively.展开更多
Acetol is a major light oxygenate and readily produced from staged or fast pyrolysis of lignocellulose biomass. Herein we report that acetol can be selectively converted to methyl pyruvate, an important fine chemical,...Acetol is a major light oxygenate and readily produced from staged or fast pyrolysis of lignocellulose biomass. Herein we report that acetol can be selectively converted to methyl pyruvate, an important fine chemical, through oxidative esterification over Au-based catalysts. Detailed experimental studies showed that Au on amphoteric supports with appropriate strength and balanced ratio of acid and base sites can facilitate the desired oxidative-esterification pathway without accelerating undesired aldol-condensation or Cannizzaro reactions. In particular, hydroxyapatite (with a Ca/P ratio of 1.62) supported Au achieved 87% selectivity to methyl pyruvate at an acetol conversion of 62%.展开更多
Compared with wheeled or tracked robots,legged robots exhibit advantages on agile locomotion and higher survival chance for deadly impacts. A buffering strategy is proposed for quadruped robots with non-extreme initia...Compared with wheeled or tracked robots,legged robots exhibit advantages on agile locomotion and higher survival chance for deadly impacts. A buffering strategy is proposed for quadruped robots with non-extreme initial attitudes from the end of air-righting to the steady standing on the ground.This approach consists of landing phase,buffering phase and recovering phase. The variable stiffness control,proportional-derivative( PD) force control and foot trajectory planning are applied to the joints of quadruped robots until the end of the recovering phase. The PD parameters are tuned according to the desired performance of each phase. The above approach is verified on a virtual platform.展开更多
Objective:To improve the diagnosis and therapeutic effect of occurrence and development of hyponatremia and disorder of acid-base balance among patients with hepatic encephalopathy(HE) by elucidating the regularity an...Objective:To improve the diagnosis and therapeutic effect of occurrence and development of hyponatremia and disorder of acid-base balance among patients with hepatic encephalopathy(HE) by elucidating the regularity and mechanism,as well as its influence on prognosis.Methods:327 HE patients admitted to our hospital from January 1990 to June 2010 were enrolled.Meanwhile 316 patients hospitalized in the medical department of the same hospital were chosen as the control group.Patients in both groups were given the same methods to measure arterial blood gas parameters(pH value,PaCO2,[HCO3-],TCO2,BE and SaO2),blood biochemistry([Na+],[K+],[Cl-]),liver function,kidney function and blood glucose,serum sodium,and thereupon tocalculate the anion gap(AG) and the potential [HCO3-],and acid-base balance disorder.Results:Among the 327 HE patients,hyponatremia was found in 188 cases(57.4%),of whom 132 patients died(70.2%).While among the 316 patients in control group,68 presented with hyponatremia(21.5%),and 19 died(27.9%).The incidence and mortality were significantly different between the two groups(P<0.001).All the 327 patients presented with different degrees of acid-base balance disorder and 178 died(54.4%),in whom 164(50.2%) belonged to simple acid-base balance disorder and 74(45.1%) died,136(41.6%) were dual acid-base balance disorder and 80(58.8%) died,27(8.2%) were triple acid-base disturbance and 24(88.9%) died.Whereas in the control group only 83 patients(26.2%) were recognized as simple and dual acid-base balance disorder,and 18(21.7%) died.There was higher incidence of acid-base balance disorder and mortality rate in HE group than control one(P<0.001).Conclusion:Hyponatremia is valuable to judge HE patients' prognosis.The key parameters in the judgment and evaluation on acid-base balance disorder among HE patients are the change of pH values and serum electrolyte values.When pH value ≤ 7.30 or > 7.55,it generally suggests a poor prognosis.展开更多
Two dehydroabietic acid-based arylamines have been synthesized and characterized by FTIR, 1H NMR, 13C NMR, MS spectra and elemental analysis. Their spatial structures were determined by X-ray diffraction analysis. UV-...Two dehydroabietic acid-based arylamines have been synthesized and characterized by FTIR, 1H NMR, 13C NMR, MS spectra and elemental analysis. Their spatial structures were determined by X-ray diffraction analysis. UV-Vis absorption and fluorescence spectral characteristics of these compounds in methanol were investigated. Their fluorescence emission spectra in different polarity solvents were further evaluated. Fluorescent properties and structural relationship of the compounds showed that fluorescence intensity and quantum yield inversely increase with the non-coplanar degree. In addition, the solvent polarity has different effects on the fluorescence emission spectra of two compounds.展开更多
As a mono-sodium salt form of alendronic acid,alendronate sodium presents multi-level ionization for the dissociation of its four hydroxyl groups.The dissociation constants of alendronate sodium were determined in thi...As a mono-sodium salt form of alendronic acid,alendronate sodium presents multi-level ionization for the dissociation of its four hydroxyl groups.The dissociation constants of alendronate sodium were determined in this work by studying the piecewise linear relationship between volume of titrant and p H value based on acidbase potentiometric titration reaction.The distribution curves of alendronate sodium were drawn according to the determined p Ka values.There were 4 dissociation constants(pKa_1=2.43,pKa_2=7.55,pKa_3=10.80,pKa_4=11.99,respectively) of alendronate sodium,and 12 existing forms,of which 4 could be ignored,existing in different p H environments.展开更多
The amphoteric properties of four sulfide minerals were characterized byacidimetric-alkalimetric titration. Chalcocite, galena, and sphalerite were found to bediprotic acids, while pyrite was determined to be a tripro...The amphoteric properties of four sulfide minerals were characterized byacidimetric-alkalimetric titration. Chalcocite, galena, and sphalerite were found to bediprotic acids, while pyrite was determined to be a triprotic acid. Intrinsic acidity con-stants for the four minerals are as follows: chalcocite-pK_(a1)=5.25, pK_(a2)=9.68;galena- pK_(a1)=5.26, pK_(a2)=9.62; sphalente- pK_(a1)= 5.08, pK_(a2)= 9.13;and pyrite - pK_(a1) = 3.50,pK_(a2)=5.32, pK_(a3)=9.81.展开更多
Cerium oxide(ceria)plays an important and fascinating role in heterogeneous catalysis as illustrated by its versatile use as a catalyst,a catalyst support,or a promotor in various oxidation and reduction reactions.Cen...Cerium oxide(ceria)plays an important and fascinating role in heterogeneous catalysis as illustrated by its versatile use as a catalyst,a catalyst support,or a promotor in various oxidation and reduction reactions.Central to these reactions is the rich defect chemistry,facile redox capability,and unusual acid-base properties of ceria.Understanding the unique redox and acid-base properties of ceria is essential to build the structure-catalysis relationship so that improved catalytic functions can be achieved for ceria-based materials.Among the characterization toolbox,spectroscopic approach indisputably stands out for its unparalleled power in offering chemical insights into the surface properties of ceria at atomic and molecular level.In this review,we summarize advances in revealing the redox and acid-base properties of ceria via a variety of spectroscopic methods including optical,X-ray,neutron,electronic and nuclear spectroscopy.Both direct spectroscopy characterization and its coupling with probe molecules are analyzed to illustrate how the nature,strength and density of different surface sites are influenced by the pretreatment,the morphology and size of ceria nanoparticles.Further directions in taking advantage of in situ/operando spectroscopy for better understanding the catalysis of ceria-based materials are proposed in the summary and outlook section.展开更多
5-Hydroxymethylfurfural(5-HMF),as a key platform compound for the conversion of biomass to various biomass-derived chemicals and biofuels,has been attracted extensive attention.In this research,using Pickering high in...5-Hydroxymethylfurfural(5-HMF),as a key platform compound for the conversion of biomass to various biomass-derived chemicals and biofuels,has been attracted extensive attention.In this research,using Pickering high internal phase emulsions(Pickering HIPEs)as template and functional metal-organic frameworks(MOFs,UiO-66-SO;H and UiO-66-NH;)/Tween 85 as co-stabilizers to synthesis the dual acid-base bifunctional macroporous polymer catalyst by one-pot process,which has excellent catalytic activity in the cascade reaction of converting cellulose to 5-HMF.The effects of the emulsion parameters including the amount of surfactant(ranging from 0.5%to 2.0%(mass)),the internal phase volume fraction(ranging from 75%to 90%)and the acid/base Pickering particles mass ratio(ranging from 0:6 to 6:0)on the morphology and catalytic performance of solid catalyst were systematically researched.The results of catalytic experiments suggested that the connected large pore size of catalyst can effectively improve the cellulose conversion,and the synergistic effect of acid and base active sites can effectively improve the 5-HMF yield.The highest 5-HMF yield,about 40.5%,can be obtained by using polymer/MOFs composite as catalyst(Poly-P12,the pore size of(53.3±11.3)μm,the acid density of 1.99 mmol·g^(-1)and the base density of 1.13 mol·g^(-1))under the optimal reaction conditions(130℃,3 h).Herein,the polymer/MOFs composite with open-cell structure was prepared by the Pickering HIPEs templating method,which provided a favorable experimental basis and theoretical reference for achieving efficient production of high addedvalue product from abundant biomass.展开更多
The latest view suggests the inactive core,surface pulverization,and poly sulfide shuttling effect of metal sulfides are responsible for their low capacity and poor cycling performance in sodium-ion batteries(SIBs).Wh...The latest view suggests the inactive core,surface pulverization,and poly sulfide shuttling effect of metal sulfides are responsible for their low capacity and poor cycling performance in sodium-ion batteries(SIBs).Whereas overcoming the above problems based on conventional nanoengineering is not efficient enough.In this work,erythrocyte-like CuS microspheres with an elastic buffering layer of ultrathin poly aniline(PANI) were synthesized through one-step selfassembly growth,followed by in situ polymerization of aniline.When CuS@PANI is used as anode electrode in SIBs,it delivers high capacity,ultrahigh rate capability(500 mAh gat 0.1 A g,and 214.5 mAh gat 40 A g),and superior cycling life of over 7500 cycles at 20 A g.A series of in/ex situ characterization techniques were applied to investigate the structural evolution and sodium-ion storage mechanism.The PANI swollen with electrolyte can stabilize solid electrolyte interface layer,benefit the ion transport/charge transfer at the PANI/electrolyte interface,and restrain the size growth of Cu particles in confined space.Moreover,finite element analyses and density functional simulations confirm that the PANI film effectively buffers the volume expansion,suppresses the surface pulverization,and traps the poly sulfide.展开更多
Sulfonated poly（phthalazinone）s （SPPENK, SPPESK and SPPBEK） were prepared by direct polymerization reaction from sulfonated monomers. The novel acid-base membranes were composed of sulfonated polymers as the acidi...Sulfonated poly（phthalazinone）s （SPPENK, SPPESK and SPPBEK） were prepared by direct polymerization reaction from sulfonated monomers. The novel acid-base membranes were composed of sulfonated polymers as the acidic compounds, and polyetherimide （PEI） as the basic compounds, casting from their N-methylpyrrolidone （NMP） solution directly onto clean glass plates at 60 ℃ aiming at enhancing membrane toughness and other relative properties. The resulted acid-base composite membranes had excellent resistance to swelling, thermo-stability, hydrolysis resistance and oxidative resistance properties with highly ion-exchange capacity （IEC）.展开更多
In this review,we discuss recent advances in nucleic acid-based therapeutic technologies that target hepatitis C virus(HCV)infection.Because the HCV genome is present exclusively in RNA form during replication,various...In this review,we discuss recent advances in nucleic acid-based therapeutic technologies that target hepatitis C virus(HCV)infection.Because the HCV genome is present exclusively in RNA form during replication,various nucleic acid-based therapeutic approaches targeting the HCV genome,such as ribozymes,aptamers,siRNAs,and antisense oligonucleotides,have been suggested as potential tools against HCV.Nucleic acids are potentially immunogenic and typically require a delivery tool to be utilized as therapeutics.These limitations have hampered the clinical development of nucleic acid-based therapeutics.However,despite these limitations,nucleic acid-based therapeutics has clinical value due to their great specificity,easy and large-scale synthesis with chemical methods,and pharmaceutical flexibility.Moreover,nucleic acid therapeutics are expected to broaden the range of targetable molecules essential for the HCV replication cycle,and therefore they may prove to be more effective than existing therapeutics,such as interferon-αand ribavirin combination therapy.This review focuses on the current status and future prospects of ribozymes,aptamers,siRNAs,and antisense oligonucleotides as therapeutic reagents against HCV.展开更多
The structure and working principle of a hydraulic buffering valve for a power-shift transmission ZF-4WG308 were studied comprehensively, and a model of the hydraulic buffering valve was developed with AMESim. A bench...The structure and working principle of a hydraulic buffering valve for a power-shift transmission ZF-4WG308 were studied comprehensively, and a model of the hydraulic buffering valve was developed with AMESim. A bench test was conducted on a buffering valve for transmissions(ZF-4WG308) and the test results agree well with the simulated results. Further more, the influences of the key parameters of the valve on the buffering performance were also studied in details.展开更多
文摘The acid-base buffer characteristics of fulvic acid (FA) and barium fulvate (BaFA)were analyzed. Each share of the sample or model agents (phthalic acid and salicylic acid)were separately mixed into a series of shares of dilute solutions of HCI or NaOH with a series of concentration. The original pH values of the solutions were arranged from 2 to 13.Final balanced pH of each share was measured. The pH changes show that FA and BaFApossess buffer ability, whereas the model agents do not. The tendency of balanced pHvalues was 5.4 for FA and 7.4 for BaFA, whereas the original pH was 4.0-8.5; balancedpH changed little. At room temperature, the maximum buffer capacities were as follows:18.11 mmol hydroxyl per gram FA, 11.25 mmol hydroxyl per gram BaFA, 1.19 mmol protonper gram FA, and 1.45 mmol proton per gram BaFA. Mathematics analysis shows thatlogarithm of buffer capacities of FA and BaFA is linearly dependent on original pH. Compared with BaFA and model agents, it is concluded that FA buffer capacity against hydroxylrelies not only on its acidic groups, BaFA buffer capacity against hydroxyl does not rely onits acidic groups, and FA buffer capacity against proton is not related with its carboxyl andphenolic hydroxyl group. The pH values of FA-water solutions with different concentrationsfrom 1 to 10 grams per liter were measured. Their pH values were slightly affected by itsconcentration. Thus, FA possesses a much stronger buffer ability against water dilutionthan common buffer agent. All the pH values of FA water solutions were very nearby 5.4,just the same as the balanced pH tendency for adding FA.
文摘Two methods of irrigation,drip,and sprinkler were studied to determine the response of the Javits green roof to irrigation.The control study was dry unirrigated plots.Drip irrigation consisted of irrigation tubes running through the green roof that would water the soil throughout and sprinkler irrigation used a sprinkler system to irrigate the green roof from above.In all cases,the irrigated roofs had increased the soil moisture,reduced temperatures of both the upper and lower surfaces,reduced growing medium temperatures and reduced air temperatures above the green roof relative to the unirrigated roof.The buffered temperature fluctuations were also studied via air conditioner energy consumption.There was a 28%reduction in air conditioner energy consumption and a 33%reduction in overall energy consumption between dry and irrigated plots.Values of thermal resistance or S were determined for accuracy and for this study,there was little change which is ideal.A series of infra-red and thermal probe measurements were used to determine temperatures in the air and sedum.It was determined that the sprinkler irrigation did a better job than the drip irrigation in keeping cooler temperatures within the green roof.A Mann-Whitney U test was performed to verify the variation in moisture temperatures buffering energy consumption.By getting a p-value<0.05,it indicates that the model is accurate for prediction and medium temperatures were statistically different.
基金the financial sponsored by the CNPC Innovation Found(No.2022DQ02-0402)the Natural Science Basic Research Program of Shaanxi(No.2024JC-YBMS-085)+2 种基金Shandong Provincial Postdoctoral Science Foundation(No.SDCX-ZG-202303044)the State Key Laboratory of Heavy Oil Processing(No.SKLHOP202201004,No.SKLHOP202403001)the Graduate Student Innovation and Practical Ability Training Program of Xi'an Shiyou University(No.YCS23213078).
文摘Heavy oil millisecond gas-phase in-line catalytic dehydrogenation over bifunctional catalysts was adopted to produce low-carbon olefins.In this study,the effect of the uncatalyzed reaction composition and distribution of atmosphere residue(AR)pyrolysis vapor at 650℃ was investigated for the first time.In the pyrolysis vapor,the yield of low-carbon olefins was only 15.2%.The yield of 1-olefin and n-alkanes,which are the primary products of rapid heavy oil pyrolysis,reached approximately 54.0%.To achieve further catalytic dehydrogenation,AR pyrolysis volatiles were catalyzed over single calcium aluminate(C_(12)A_(7)),ZSM-5,and C_(12)A_(7)-ZSM-5(CZ)catalysts at 650℃,which possess different pore structures,and acid-base properties.The ZSM-5 catalyst obtained the highest low-carbon olefin yield after catalytic dehydrogenation of pyrolysis volatiles.Finally,the C_(12)A_(7) and CZ stepwise coupling bifunctional catalysts increased the catalytic activity,and thus increased the higher low-carbon olefin yield but reduced the yields of alkanes and aromatics fraction.Notably,the yields of propylene and butane were important sources of the low-carbon olefins.Thus,heavy oil millisecond gas-phase in-line catalytic dehydrogenation could achieve the maximum conversion of these residues to produce low-carbon olefins.
基金the support of the National Natural Science Foundation of China(Grant No.42207199)Scientific Research Project of Education of Zhejiang Province(No.Y202351343)+1 种基金Zhejiang Postdoctoral Scientific Research Project(Grant Nos.ZJ2022155,ZJ2022156)Zhejiang Province International Science and Technology Cooperation Base Open Fund Project(IBGDP-2023-01)。
文摘The squeezing deformation of surrounding rock is an important factor restricting the safe construction and long-term operation of tunnels when a tunnel passes through soft strata with high ground stress.Under such soft rock geological conditions,the large deformation of the surrounding rock can easily lead to the failure of supporting structures,including shotcrete cracks,spalling,and steel arch distortion.To improve the lining support performance during the large deformation of squeezed surrounding rock,this work selects aluminum foam with densities of 0.25 g/cm3,0.42 g/cm3 and 0.61 g/cm3 as the buffer layer material and carries out uniaxial confined compression tests.Through the evaluation and analysis of energy absorption and the comparison of the yield pressure of aluminum foam with those of other cushioning materials and yield pressure support systems,the strength,deformation and energy absorption of aluminum foam with a density of 0.25 g/cm3 meet the yield pressure performance requirements.The numerical model of the buffer layer yielding support system is then established via the finite element analysis software ABAQUS,and the influence of the buffer layer setting on the lining support is analyzed.Compared with the conventional support scheme,the addition of an aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining.The maximum and minimum principal stresses of the primary support are reduced by 13%and 15%,respectively.The maximum and minimum principal stresses of the secondary lining are reduced by 15%and 12%,respectively,and the displacement deformation of the secondary lining position is reduced by 15%.In summary,the application of aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining,improve the stress safety of the support and reduce the deformation of the support.
文摘The role of forest litter as an acid-base buffering system was assessed by litter from plantation and natural forests in South China. Samples were either extracted with acid solutions or titrated with acid or base solutions. Litter was found to be a strong acid-base buffering system. Two legume species, Acacia mangium Willd and A. auriculaiformis A. Cunn, had very high litter pH values of around 6, which was 2 pH units higher than that of the soil where they grew. Litter of all other plantation species had litter pH of around 4, similar to that of the soil. Both legume species have high potential to neutralize soil acidity and the litter layer could act to shield soil against acid rain. The current stand of two legume species was estimated to be able to raise rain acidity by 0.1 to 0.4 pH units. Inorganic ions did not fully explain the pH pattern of different litter extracts, but high sodium and low nitrate partly accounted for the high pH of the two legume species. Some natural forest species had extremely low pH. As a whole, the litter of the natural climax forest was the driving force of soil acidification. Although plant residues are strong acid-base buffering system and able to adjust acidity of environment, only a few species can be expected to make soil more acid or alkaline through this mechanism since most species have litter pH values similar to those of soil where they grow.
文摘The dynamic math model of shift clutch in engagement process was determined on the basis of hydraulic buffering valve and shift clutch of a power shift steering transmission. The influence of buffering pressure characteristic on shift clutch engagement process was analyzed. The study results could be used to the characteristics match of the shift clutch with the hydraulic system of the high speed tracked vehicle power shift steering transmission and the performance prediction.
文摘In this paper, the efficiencies of two production lines, one is with commonly, the other is with separately buffer capacities are compared, the result is that the former one is better than the latter
文摘The effects of soil solid components on soil sensitivity to acid deposition by sequential extraction method were studied. A multiple regression equation of soil sensitivity was set up on the basis of stepwise regression analysis. The results showed that organic matter expressed dual effects that were decided by soil original pH value and exchangeable cation composition on acid buffering reactions. The hydrolysis of activated oxides was a very important proton buffering reaction when in low pH situation. The crystalline oxides also played a role in the buffering reactions, but the role was restricted by the rate of activation of oxides. Meanwhile, the results by stepwise analysis showed that factors that had significant effect on soil acid buffering capacity were content of montmorillite, soil original pH value, Al 0, Mn 0 and CEC in decreasing order. Finally, sixteen soils were classified into four types of sensitive with single index cluster and multiple fuzzy cluster analysis respectively.
基金supported by the National Natural Science Foundation of China(91545114,91545203,and 21576227)the 985 Program of the Chemistry and Chemical Engineering disciplines of Xiamen University~~
文摘Acetol is a major light oxygenate and readily produced from staged or fast pyrolysis of lignocellulose biomass. Herein we report that acetol can be selectively converted to methyl pyruvate, an important fine chemical, through oxidative esterification over Au-based catalysts. Detailed experimental studies showed that Au on amphoteric supports with appropriate strength and balanced ratio of acid and base sites can facilitate the desired oxidative-esterification pathway without accelerating undesired aldol-condensation or Cannizzaro reactions. In particular, hydroxyapatite (with a Ca/P ratio of 1.62) supported Au achieved 87% selectivity to methyl pyruvate at an acetol conversion of 62%.
基金Supported by the National High Technology Research and Development Program of China(No.2015AA042201)the National Natural Science Foundation of China(No.61233014,61305130)+1 种基金the Shandong Provincial Natural Science Foundation(No.ZR2013FQ003,ZR2013EEM027)China Postdoctoral Science Foundation(No.2013M541912)
文摘Compared with wheeled or tracked robots,legged robots exhibit advantages on agile locomotion and higher survival chance for deadly impacts. A buffering strategy is proposed for quadruped robots with non-extreme initial attitudes from the end of air-righting to the steady standing on the ground.This approach consists of landing phase,buffering phase and recovering phase. The variable stiffness control,proportional-derivative( PD) force control and foot trajectory planning are applied to the joints of quadruped robots until the end of the recovering phase. The PD parameters are tuned according to the desired performance of each phase. The above approach is verified on a virtual platform.
文摘Objective:To improve the diagnosis and therapeutic effect of occurrence and development of hyponatremia and disorder of acid-base balance among patients with hepatic encephalopathy(HE) by elucidating the regularity and mechanism,as well as its influence on prognosis.Methods:327 HE patients admitted to our hospital from January 1990 to June 2010 were enrolled.Meanwhile 316 patients hospitalized in the medical department of the same hospital were chosen as the control group.Patients in both groups were given the same methods to measure arterial blood gas parameters(pH value,PaCO2,[HCO3-],TCO2,BE and SaO2),blood biochemistry([Na+],[K+],[Cl-]),liver function,kidney function and blood glucose,serum sodium,and thereupon tocalculate the anion gap(AG) and the potential [HCO3-],and acid-base balance disorder.Results:Among the 327 HE patients,hyponatremia was found in 188 cases(57.4%),of whom 132 patients died(70.2%).While among the 316 patients in control group,68 presented with hyponatremia(21.5%),and 19 died(27.9%).The incidence and mortality were significantly different between the two groups(P<0.001).All the 327 patients presented with different degrees of acid-base balance disorder and 178 died(54.4%),in whom 164(50.2%) belonged to simple acid-base balance disorder and 74(45.1%) died,136(41.6%) were dual acid-base balance disorder and 80(58.8%) died,27(8.2%) were triple acid-base disturbance and 24(88.9%) died.Whereas in the control group only 83 patients(26.2%) were recognized as simple and dual acid-base balance disorder,and 18(21.7%) died.There was higher incidence of acid-base balance disorder and mortality rate in HE group than control one(P<0.001).Conclusion:Hyponatremia is valuable to judge HE patients' prognosis.The key parameters in the judgment and evaluation on acid-base balance disorder among HE patients are the change of pH values and serum electrolyte values.When pH value ≤ 7.30 or > 7.55,it generally suggests a poor prognosis.
基金supported by the National Natural Science Foundation of China (No. 31170539)
文摘Two dehydroabietic acid-based arylamines have been synthesized and characterized by FTIR, 1H NMR, 13C NMR, MS spectra and elemental analysis. Their spatial structures were determined by X-ray diffraction analysis. UV-Vis absorption and fluorescence spectral characteristics of these compounds in methanol were investigated. Their fluorescence emission spectra in different polarity solvents were further evaluated. Fluorescent properties and structural relationship of the compounds showed that fluorescence intensity and quantum yield inversely increase with the non-coplanar degree. In addition, the solvent polarity has different effects on the fluorescence emission spectra of two compounds.
基金the support of Key Laboratory of Chinese Medicine Preparation of Solid Dispersion,Gansu Longshenrongfa Pharmaceutical Industry Co.,Ltd.,Gansu Province,China
文摘As a mono-sodium salt form of alendronic acid,alendronate sodium presents multi-level ionization for the dissociation of its four hydroxyl groups.The dissociation constants of alendronate sodium were determined in this work by studying the piecewise linear relationship between volume of titrant and p H value based on acidbase potentiometric titration reaction.The distribution curves of alendronate sodium were drawn according to the determined p Ka values.There were 4 dissociation constants(pKa_1=2.43,pKa_2=7.55,pKa_3=10.80,pKa_4=11.99,respectively) of alendronate sodium,and 12 existing forms,of which 4 could be ignored,existing in different p H environments.
文摘The amphoteric properties of four sulfide minerals were characterized byacidimetric-alkalimetric titration. Chalcocite, galena, and sphalerite were found to bediprotic acids, while pyrite was determined to be a triprotic acid. Intrinsic acidity con-stants for the four minerals are as follows: chalcocite-pK_(a1)=5.25, pK_(a2)=9.68;galena- pK_(a1)=5.26, pK_(a2)=9.62; sphalente- pK_(a1)= 5.08, pK_(a2)= 9.13;and pyrite - pK_(a1) = 3.50,pK_(a2)=5.32, pK_(a3)=9.81.
文摘Cerium oxide(ceria)plays an important and fascinating role in heterogeneous catalysis as illustrated by its versatile use as a catalyst,a catalyst support,or a promotor in various oxidation and reduction reactions.Central to these reactions is the rich defect chemistry,facile redox capability,and unusual acid-base properties of ceria.Understanding the unique redox and acid-base properties of ceria is essential to build the structure-catalysis relationship so that improved catalytic functions can be achieved for ceria-based materials.Among the characterization toolbox,spectroscopic approach indisputably stands out for its unparalleled power in offering chemical insights into the surface properties of ceria at atomic and molecular level.In this review,we summarize advances in revealing the redox and acid-base properties of ceria via a variety of spectroscopic methods including optical,X-ray,neutron,electronic and nuclear spectroscopy.Both direct spectroscopy characterization and its coupling with probe molecules are analyzed to illustrate how the nature,strength and density of different surface sites are influenced by the pretreatment,the morphology and size of ceria nanoparticles.Further directions in taking advantage of in situ/operando spectroscopy for better understanding the catalysis of ceria-based materials are proposed in the summary and outlook section.
基金financially supported by the National Natural Science Foundation of China(No.21606100)the Natural Science Foundation of Jiangsu Province(No.BK20180850)+1 种基金the China Postdoctoral Science Foundation(Nos.2019M651740 and 2019T120397)the Young Talent Cultivate Programme of Jiangsu University。
文摘5-Hydroxymethylfurfural(5-HMF),as a key platform compound for the conversion of biomass to various biomass-derived chemicals and biofuels,has been attracted extensive attention.In this research,using Pickering high internal phase emulsions(Pickering HIPEs)as template and functional metal-organic frameworks(MOFs,UiO-66-SO;H and UiO-66-NH;)/Tween 85 as co-stabilizers to synthesis the dual acid-base bifunctional macroporous polymer catalyst by one-pot process,which has excellent catalytic activity in the cascade reaction of converting cellulose to 5-HMF.The effects of the emulsion parameters including the amount of surfactant(ranging from 0.5%to 2.0%(mass)),the internal phase volume fraction(ranging from 75%to 90%)and the acid/base Pickering particles mass ratio(ranging from 0:6 to 6:0)on the morphology and catalytic performance of solid catalyst were systematically researched.The results of catalytic experiments suggested that the connected large pore size of catalyst can effectively improve the cellulose conversion,and the synergistic effect of acid and base active sites can effectively improve the 5-HMF yield.The highest 5-HMF yield,about 40.5%,can be obtained by using polymer/MOFs composite as catalyst(Poly-P12,the pore size of(53.3±11.3)μm,the acid density of 1.99 mmol·g^(-1)and the base density of 1.13 mol·g^(-1))under the optimal reaction conditions(130℃,3 h).Herein,the polymer/MOFs composite with open-cell structure was prepared by the Pickering HIPEs templating method,which provided a favorable experimental basis and theoretical reference for achieving efficient production of high addedvalue product from abundant biomass.
基金This work was financially supported by the National Natural Science Foundation of China(NSFC.U1904190,51925207,U1910210,52161145101 and 51872277)the Natural Science Foundation for Excellent Young Scholars of Henan Province(Grant No.212300410091)+5 种基金Program for Science and Technology Innovation Talents in Universities of Henan Province(Grant No.22HASTIT005)Key Program of Henan Province for Science and Technology(222102240029)the“Transformational Technologies for Clean Energy and Demonstration”Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDA21000000)the National Synchrotron Radiation Laboratory(KY2060000173)the Joint Fund of the Yulin University and the Dalian National Laboratory for Clean Energy(Grant.YLU-DNL Fund 2021002)the Fundamental Research Funds for the Central Universities(WK2060140026).
文摘The latest view suggests the inactive core,surface pulverization,and poly sulfide shuttling effect of metal sulfides are responsible for their low capacity and poor cycling performance in sodium-ion batteries(SIBs).Whereas overcoming the above problems based on conventional nanoengineering is not efficient enough.In this work,erythrocyte-like CuS microspheres with an elastic buffering layer of ultrathin poly aniline(PANI) were synthesized through one-step selfassembly growth,followed by in situ polymerization of aniline.When CuS@PANI is used as anode electrode in SIBs,it delivers high capacity,ultrahigh rate capability(500 mAh gat 0.1 A g,and 214.5 mAh gat 40 A g),and superior cycling life of over 7500 cycles at 20 A g.A series of in/ex situ characterization techniques were applied to investigate the structural evolution and sodium-ion storage mechanism.The PANI swollen with electrolyte can stabilize solid electrolyte interface layer,benefit the ion transport/charge transfer at the PANI/electrolyte interface,and restrain the size growth of Cu particles in confined space.Moreover,finite element analyses and density functional simulations confirm that the PANI film effectively buffers the volume expansion,suppresses the surface pulverization,and traps the poly sulfide.
基金This study was supported by the National Natural Science Foundation of China （No. 50373005）；the Chinese National Programs for High Technology Research and Development （＂863＂ plan, No. 2003AA33G030）.
文摘Sulfonated poly（phthalazinone）s （SPPENK, SPPESK and SPPBEK） were prepared by direct polymerization reaction from sulfonated monomers. The novel acid-base membranes were composed of sulfonated polymers as the acidic compounds, and polyetherimide （PEI） as the basic compounds, casting from their N-methylpyrrolidone （NMP） solution directly onto clean glass plates at 60 ℃ aiming at enhancing membrane toughness and other relative properties. The resulted acid-base composite membranes had excellent resistance to swelling, thermo-stability, hydrolysis resistance and oxidative resistance properties with highly ion-exchange capacity （IEC）.
基金Supported by National Research Foundation of Korea(NRF)funded by the Ministry of Science,ICT and Future Planning No.2012M3A9B6055200,No.2013R1A2A2A01004649
文摘In this review,we discuss recent advances in nucleic acid-based therapeutic technologies that target hepatitis C virus(HCV)infection.Because the HCV genome is present exclusively in RNA form during replication,various nucleic acid-based therapeutic approaches targeting the HCV genome,such as ribozymes,aptamers,siRNAs,and antisense oligonucleotides,have been suggested as potential tools against HCV.Nucleic acids are potentially immunogenic and typically require a delivery tool to be utilized as therapeutics.These limitations have hampered the clinical development of nucleic acid-based therapeutics.However,despite these limitations,nucleic acid-based therapeutics has clinical value due to their great specificity,easy and large-scale synthesis with chemical methods,and pharmaceutical flexibility.Moreover,nucleic acid therapeutics are expected to broaden the range of targetable molecules essential for the HCV replication cycle,and therefore they may prove to be more effective than existing therapeutics,such as interferon-αand ribavirin combination therapy.This review focuses on the current status and future prospects of ribozymes,aptamers,siRNAs,and antisense oligonucleotides as therapeutic reagents against HCV.
基金Project(51077096)supported by the National Natural Science Foundation of ChinaProject(2012940-15-3)supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry
文摘The structure and working principle of a hydraulic buffering valve for a power-shift transmission ZF-4WG308 were studied comprehensively, and a model of the hydraulic buffering valve was developed with AMESim. A bench test was conducted on a buffering valve for transmissions(ZF-4WG308) and the test results agree well with the simulated results. Further more, the influences of the key parameters of the valve on the buffering performance were also studied in details.
