It was proposed how the concentration distribution was calculated in the treble lager wall of hgdrogenation reactor according to the principle of hydrogen diffusion at the steady state in this paper. Based on the stea...It was proposed how the concentration distribution was calculated in the treble lager wall of hgdrogenation reactor according to the principle of hydrogen diffusion at the steady state in this paper. Based on the steady hydrogen permeation current density i∞ measund with the hydrogen probe at a given temperature, the hydmpen concentrationson the key interfaces and hydrogen distribution at any given mdial profile in the single, double or treble layer wall of hydrogenation reactor could be found by applying the presented equations throoph suitable parmeters ioput. The theoretical bases were provided for developing the nondestructive probing technique of the concentration of atomic hydmpen in the wallS of hydrogenation reactors.展开更多
The recognition and monitoring of localized corrosion at the early stage on the inner wall surface of pipes are extremely difficult and simultaneously the reliable approach for recognition and monitoring is missing.He...The recognition and monitoring of localized corrosion at the early stage on the inner wall surface of pipes are extremely difficult and simultaneously the reliable approach for recognition and monitoring is missing.Here we report a spatially resolved method to recognize and monitor the localized corrosion in a non-destructive way based on the permeating hydrogen signal generated from localized corrosion itself.A simulative localized corrosion was created on one side surface of the carbon steel specimen where a dot of wet elemental sulfur was introduced to accelerate the corrosion on the local region.While,the potential on the other side surface(the reverse side of the corrosion site)of the specimen was measured using a scanning Kelvin probe.The results show that the permeating hydrogen generated from localized corrosion easily arrives on the reverse side surface of the corrosion site and then causes a huge change in surface potential.The location resolution of potential distribution can be revealed with micron level.Therefore,it is thought that the location of localized corrosion can be recognized by the permeating hydrogen signal distribution on the reverse side surface of the corrosion site since the region of potential decreasing is highly corresponding to the corrosion site.Moreover,the strength of the permeating hydrogen signal is highly related to the corrosion depth and transient corrosion rate of localized corrosion.This means that the localized corrosion development can also be monitored using the permeating hydrogen signal.Therefore,it can be expected that the localized corrosion occurring on the inner wall surface of pipes or equipment can be recognized and monitored successfully on the outer wall surface in a non-destructive way once the permeating hydrogen is present during the localized corrosion proceeding.展开更多
The androgenetic alopecia(AGA)is the most prevalent clinical manifestation of hair loss,believed to be associated with excessive dihydrotestosterone(DHT)caused by typeⅡ5α-reductase(5αR2).The utilization of oral fin...The androgenetic alopecia(AGA)is the most prevalent clinical manifestation of hair loss,believed to be associated with excessive dihydrotestosterone(DHT)caused by typeⅡ5α-reductase(5αR2).The utilization of oral finasteride(FNS),which selectively inhibits 5αR2,is frequently constrained by its adverse effects.Topical FNS formulations can mitigate adverse effects but often exhibit limited dermal permeability.Nanocarriers show great potential in augmenting the cutaneous permeation of loaded FNS due to their inherent properties of selective accumulation within the hair follicles(HFs).In this study,hollow mesoporous silica nanoparticles(HMSN)with varying sizes were utilized as the nanocarriers for FNS,following mixing with the Carbopol hydrogel(F@H/Gel)for direct topical application.Specifically,the influence of size on the targeted delivery of FNS to HFs,and its enhanced therapeutic efficacy for the AGA mice model was evaluated.Results showed that the HMSN,with a diameter of approximately 300 nm,exhibited significant enhancement in FNS retention within skin and HFs,as well as remarkably accelerated hair regrowth on an AGA mouse model.In conclusion,this FNS topical formulation has proved to be a viable approach in offering a secure and efficient treatment modality for AGA.展开更多
A GC-MS method for the determination of 27 organochlorine pesticides and 15 Pyrethroid pesticides in animal food is established.The method was based on Gel Permeation chromatography combined with solid-phase extractio...A GC-MS method for the determination of 27 organochlorine pesticides and 15 Pyrethroid pesticides in animal food is established.The method was based on Gel Permeation chromatography combined with solid-phase extraction for sample preparation.Rapid qualitative and quantitative analyses was carried out by gas chromatography-mass spectrometry under the selective-ion monitoring mode.The experimental results showed that the correlation coefficients were better than 0.99,the recoveries for spiked standards were 70%-104%,the relative standard deviations were 2.1%-15.9%.展开更多
One major problem encountered in transdermal drug delivery is the low permeability of drugs through the skin barrier. In the present study, we developed a surfactant-ethanolic liposomal system to improve the transderm...One major problem encountered in transdermal drug delivery is the low permeability of drugs through the skin barrier. In the present study, we developed a surfactant-ethanolic liposomal system to improve the transdermal delivery of docetaxel （DTX）, a model drug for high molecular weight and poorly water-soluble drugs. Surfactant-ethanolic liposomes （SEL） were composed of phospholipids, ethanol, sodium cholate, DTX and PBS which were prepared by thin film dispersion method. The developed formulations were characterized by determining the vesicle shape and surface morphology, size and size distribution, entrapment efficiency and drug loading capacity. The effects of the developed formulations on the permeation of DTX across rat skin in vitro were investigated using the modified Franz diffusion cell under both occlusive and non-occlusive application condi- tions. The DTX SELs with optimum composition （phospholipid-surfactant, 85：15, w/w） provided a significantly higher steadystate amount of flux and cumulative permeation, compared to the tranditional liposomes, surfactant liposomes and ethanolic liposomes. The optimal SELs exhibited stable vesicle size, morphology and drug loading capacity. Our results indicated that SELs were promising carriers to enhance the transdermal delivery of DTX.展开更多
For the production of reactive polyurethane cross-linkinger and curing agents, 2, 4-diisocyanate toluene （TDI） terpolymer, which possesses the rigid structures of hexatomic ring and three reactive functional groups,...For the production of reactive polyurethane cross-linkinger and curing agents, 2, 4-diisocyanate toluene （TDI） terpolymer, which possesses the rigid structures of hexatomic ring and three reactive functional groups, was synthesized and characterized by the Fourier transform infrared （FFIR）, the gel permeation chromatography （GPC） and the chemical analysis methods. The reaction conditions were studied and optimized. A tracking research on the polymerization process of TDI was taken by using the GPC. The formation processes of the terpolymer, oligomers and higher-polymers were also dealt with. Results show that the TDI terpolymer can be prepared in the presence of Cat-3 catalyst and at the reaction temperature of （60 ±2）℃. The reaction time is short, its outcomes have narrow molecular weights distribution, namely molecular weights from 530 to 550, Mw/Mn =1.10, and the mass fraction of NCO is （25. 0 ± 0. 5）%. With the reaction time prolonging, however, TDI can be further higher-polymedzed to form higher-polymers. Benzoyl chloride （0. 4%, mass fraction）, as the stabilizing agent, can effectively inhibit the occurrence of higher-polymerization. The obtained TDI terpolymer can be stable for more than half a year.展开更多
The effect of pH on the permeation of Lidocaine hydrochloride (LH) across excised rat skin was studied, the steady state flux (JSS) at different pH being determined using improved Valia-Chien diffusion cells. JSS incr...The effect of pH on the permeation of Lidocaine hydrochloride (LH) across excised rat skin was studied, the steady state flux (JSS) at different pH being determined using improved Valia-Chien diffusion cells. JSS increased substantially when pH was close to the pKa of LH. The profile of JSS versus pH showed an 慡?shaped curve. JSS of Lidocaine free base (LFB) was fourteen times that of LH. The pH of vehicle influences the permeation of LH significantly and should be considered as an important factor when a formulation is developed.展开更多
The phase composition, microstructure, thermal expansion coefficients, oxygen permeation properties and chemical stability of SrCo0.8Fe0.2O3-δ （SCFM） were investigated and compared with those of SrCo0.8Fe0.2O3-δ（...The phase composition, microstructure, thermal expansion coefficients, oxygen permeation properties and chemical stability of SrCo0.8Fe0.2O3-δ （SCFM） were investigated and compared with those of SrCo0.8Fe0.2O3-δ（SCF）. Single phase SCFM was successfully prepared by a combined EDTA-citric method. SCFM shows a lower thermal expansion coefficient （24× 10^-6-29× 10^-6/K） than SCF between 500 and 1050 ℃, indicating a more stable structure. SCFM shows a high oxygen permeation flux, although the oxygen flux of SCFM decreases slightly because of Mo dopant. Furthermore, it was demonstrated that the doping of Mo in SCF can prevent the order-disorder transition and improves the chemical stability to CO2.展开更多
Rare earth (RE) atoms were permeated into the surface of Al bronze (Cu-7. gA1-1. 9 Sn) by the method of chemical heat treatment. The permeated layer was then analysed by TEM (Transmission Electron Microscope) , EPMA (...Rare earth (RE) atoms were permeated into the surface of Al bronze (Cu-7. gA1-1. 9 Sn) by the method of chemical heat treatment. The permeated layer was then analysed by TEM (Transmission Electron Microscope) , EPMA (Electronic Probe Microanalysis) and IMA (Ion Microprobe Appratus). The results show that CuREAl and dispersed η phase (Cu6Sn5) distribute in the layer, RE content decreases in the depth direction, and alloying elements (Al, Sn) are enriched in the outer layer and dilute in the second layer.展开更多
Membrane fouling is the main problem of membrane bioreactors (MBR), which seriously influ- ences its wastewater treatment effect and running. The characteristics of microbiology and hydrodynamics concerning membrane f...Membrane fouling is the main problem of membrane bioreactors (MBR), which seriously influ- ences its wastewater treatment effect and running. The characteristics of microbiology and hydrodynamics concerning membrane fouling were investigated and the measure was put forward for optimum operation of MBR. The measure is that 1) the parameters of activated sludge concentration (X) and membrane flux should be lower than the critical values of X and membrane flux respectively, and 2) the activated sludge should be discharged periodically. The experimental results show that the combination backwashing of gas and perme- ated effluent is better than single gas backwashing or single permeated effluent backwashing. This technique can remove the cake layer deposited on the membrane surface, decrease the membrane fouling, and recover the membrane flux effectively. So it is effective for prevention of membrane fouling.展开更多
In order to reveal the permeability rule of leaching agent solution and the effects of anions in the leaching process of weathered crust elution-deposited rare earth（RE） ores, the effects of ammonium concentration, ...In order to reveal the permeability rule of leaching agent solution and the effects of anions in the leaching process of weathered crust elution-deposited rare earth（RE） ores, the effects of ammonium concentration, temperature, particle size and porosity on the permeability were discussed in detail with（NH4）2SO4, NH4Cl and NH4NO3 as the leaching agent. It was found that the permeation velocity of ammonium salts increased linearly with the increase of hydraulic gradient. The seepage of ammonium salts solution in the RE ores followed Darcy’s law and displayed a laminar flow. The properties of the leaching agent solution and RE ores were the main factors that affect the permeability of RE ores. With the decrease of ammonium concentration and increase of temperature, the viscosity of solution decreased and the permeability coefficients of RE ores increased. And the effects of temperature on the viscosity and permeability were larger than ammonium concentration. The permeability of RE ores became worse with the decrease of particle size and porosity, and the particle size played a more important role compared with porosity. The permeability coefficient of RE ores increased and the viscosity of ammonium salts solution decreased in the order of（NH4）2SO4, NH4Cl and NH4NO3, implying that the penetrating power of anions increased in the order of SO42-, Cl- and NO3-. The results may play a vital role in improving the permeability of weathered crust elution-deposited RE ores.展开更多
Different from the grain boundary diffusion process(GBDP),which is suitable for modifying thin magnet,a green-pressing agents permeation process(GAPP)that uses low melting point alloys was applied to the Nd-Fe-B green...Different from the grain boundary diffusion process(GBDP),which is suitable for modifying thin magnet,a green-pressing agents permeation process(GAPP)that uses low melting point alloys was applied to the Nd-Fe-B green compact with a thickness over 15 mm to reconstruct the boundary microstructure of a sintered Nd-Fe-B magnet.The coercivity increases from 12.3 kOe for the sample free of Pr80Al20 to16.8 kOe for the sample with 2 wt%Pr80Al20.By further increasing the Pr80Al20 content to 3 wt%,the coercivity increases slightly,but the remanence and Hk/Hcj deteriorate obviously.The optimal comprehensive properties of Hcj=16.8 kOe,Br=13.4 kG and Hk/Hcj=0.975 are obtained at 2 wt%Pr80Al20,since matrix phase grains are separated by relatively continuous thin grain boundary layers,which weaken the magnetic coupling between adjacent grains.The coercivities of the samples from the GAPP that use2 wt%Pr80Al20,Pr70Al30 and Pr60Tb20Al20 alloys,respectively,can be enhanced to a large extent.However,the coercivity of the magnet reconstructed with Pr80Al20 is lower than that of the sample with Pr60Tb20Al20 but is higher than that of the sample reconstructed with Pr70Cu30 alloy.Moreover,the coercivity of the sample from the GAPP using 2 wt%Pr80Al20 is much higher than that of the sample from the GBDP,which is due to a nearly uniform boundary microstructure from the surface to the interior of the thick magnet from the GAPP,thus providing new insights into the fabrication of thick and bulky permanent magnets with high coercivity.展开更多
Influence of vanadium and/or niobium additions on delayed fracture behavior in high strength spring steel was studied by hydrogen permeation method and slow strain rate technique （8SRT）, and its mechanism was analyz...Influence of vanadium and/or niobium additions on delayed fracture behavior in high strength spring steel was studied by hydrogen permeation method and slow strain rate technique （8SRT）, and its mechanism was analyzed. The results show that apparent diffusion coefficient of hydrogen in microalloyed spring steels Nb-V-steel and Nb-steel is lower than that in non-microalloyed steel 60Si2MnA. Percentage of strength reduction in SSRT in air after precharged hydrogen of the microalloyed steels is smaller than that of 60Si2MnA. Addition of the microalloys changes the fracture characteristics. Thence, vanadium and/or niobium additions are a very effective and economy means to improve the hydrogen-induced delayed fracture resistance of high strength spring steel.展开更多
Grout injection is used for sealing or strengthening the ground in order to prevent water entrance or any failure after excavation.There are many methods of grouting.Permeation grouting is one of the most common types...Grout injection is used for sealing or strengthening the ground in order to prevent water entrance or any failure after excavation.There are many methods of grouting.Permeation grouting is one of the most common types in which the grout material is injected to the pore spaces of the ground.In grouting operations,the grout quality is important to achieve the best results.There are four main characteristics for a grout mixture including bleeding,setting time,strength,and viscosity.In this paper,we try to build some efficient grouting mixtures with different water to cement ratios considering these characteristics.The ingredients of grout mixtures built in this study are cement,water,bentonite,and some chemical additives such as sodium silicate,sodium carbonate,and triethanolamine(TEA).The grout mixtures are prepared for both of the sealing and strengthening purposes for a structural project.Effect of each abovementioned ingredient is profoundly investigated.Since each ingredient may have positive or negative aspect,an optimization of appropriate amount of each ingredient is determined.The optimization is based on 200 grout mixture samples with different percentages of ingredients.Finally,some of these grout mixtures are chosen for the introduced project.It should be mentioned that grouting operations depend on various factors such as pressure of injection,ground structure and grain size of soils.However,quality of a grout can be helpful to make an injection easier and reasonable.For example,during the injection,a wrong estimated setting time can destroy the injected grout by washing the grout or setting early which prevents grouting.This paper tries to show some tests in easy way to achieve a desirable sample of grout.展开更多
Polyvinylidenefluoride （PVDF） hollow fiber ultrafiltration membrane is frequently employed in water treatment. However, the fouling of ultrafiltration membranes affects the economic effectiveness of such process sig...Polyvinylidenefluoride （PVDF） hollow fiber ultrafiltration membrane is frequently employed in water treatment. However, the fouling of ultrafiltration membranes affects the economic effectiveness of such process significantly. The ultrasound generated by flat plate transducer （UFPT） was used to clean the polluted PVDF ultrafiltration membrane with 2 g·L^-1 of citric acid aqueous solution in our study. The effects of UFPT intensity on the membrane surface were studied. The new membrane was easy to be polluted by the saturated CaCl2 solution. A synergistic effect of UFPT and 2 g·L^-1 citric acid aqueous solution could remove the foul of the membrane, and its flux could be recovered about 81%. The flux recovery of old membrane polluted was increased to 73.2% after 7 h soaking in citric acid aqueous solution, but its flux recovery without soaking was only increased to 56.2%.展开更多
A hydrogen permeation barrier was manufactured by the in situ reaction of zirconium hydride with oxygen. A reduction in the hydrogen permeation of the oxide films was detected by measuring the mass difference of the z...A hydrogen permeation barrier was manufactured by the in situ reaction of zirconium hydride with oxygen. A reduction in the hydrogen permeation of the oxide films was detected by measuring the mass difference of the zirconium hydride samples after the dehydrogenation experiment. The reaction of zirconium hydride with oxygen occurs only under the condition that the temperature is higher than 673 K in the oxygen partial pressure of 0.1 MPa. The oxide film is composed of two layers, a permeable oxide layer and a dense oxide layer, and the main phase of the oxide film is ZrO2 with baddeleyite structure. The XPS analysis shows that O-H bonds exist in the oxide film, which are helpful for resisting hydrogen diffusion through the oxide film.展开更多
Permeabilities and selectivities of gases such as carbon dioxide （CO2）, sulfur dioxide （SO2）, nitrogen （N2） and methane （CH4） in six imidazolium-based ionic liquids （[emim][BF4], [bmim][BF4], [bmim][PF6], [ba...Permeabilities and selectivities of gases such as carbon dioxide （CO2）, sulfur dioxide （SO2）, nitrogen （N2） and methane （CH4） in six imidazolium-based ionic liquids （[emim][BF4], [bmim][BF4], [bmim][PF6], [banim][BF4], [bmim][Tf2N] and [emim][CF3SO3]） supported on polyethersulfone microfiltration membranes are investigated in a single gas feed system using nitrogen as the environment and reference component at temperature from 25 to 45℃ and pressure of N2 from 100 to 400 kPa. It is found that SO2 has the highest permeability in the tested supported ionic liquid membranes, being an order of magnitude higher than that of CO2, and about 2 to 3 orders of magnitude larger than those of N2 and CH4. The observed selectivity of SO2 over the two ordinary gas components is also striking. It is shown experimentally that the dissolution and transport of gas components in the supported ionic liquid membranes, as well as the nature of ionic liquids play important roles in the gas permeation. A nonlinear increase of permeation rate with temperature and operation pressure is also observed for all sample gases. By considering the factors that influence the permeabilities and selectivities of CO2 and SO2, it is expected to develop an optimal supported ionic liquid membrane technology for the isolation of acidic gases in the near future.展开更多
This paper reports a study on the role of fluid flow pattern and dynamic pressure on the permeate flux through a micro filtration membrane in laboratory scale.For this purpose,a dead-end membrane cell equipped with a ...This paper reports a study on the role of fluid flow pattern and dynamic pressure on the permeate flux through a micro filtration membrane in laboratory scale.For this purpose,a dead-end membrane cell equipped with a marine type impeller was used.The impeller was set to rotate in the clockwise and counter clockwise directions with the same angular velocities in order to illustrate the effect of rotation direction on permeate flux.Consequently, permeate fluxes were measured at various impeller rotational speeds.The computational fluid dynamics（CFD）predicted dynamic pressure was related to the fluxes obtained in the experiments.Using the CFD modeling,it is proven that the change in dynamic pressure upon the membrane surface has direct effect on the permeate flux.展开更多
文摘It was proposed how the concentration distribution was calculated in the treble lager wall of hgdrogenation reactor according to the principle of hydrogen diffusion at the steady state in this paper. Based on the steady hydrogen permeation current density i∞ measund with the hydrogen probe at a given temperature, the hydmpen concentrationson the key interfaces and hydrogen distribution at any given mdial profile in the single, double or treble layer wall of hydrogenation reactor could be found by applying the presented equations throoph suitable parmeters ioput. The theoretical bases were provided for developing the nondestructive probing technique of the concentration of atomic hydmpen in the wallS of hydrogenation reactors.
基金support from the National Natural Science Foundation of China(No.52171080)。
文摘The recognition and monitoring of localized corrosion at the early stage on the inner wall surface of pipes are extremely difficult and simultaneously the reliable approach for recognition and monitoring is missing.Here we report a spatially resolved method to recognize and monitor the localized corrosion in a non-destructive way based on the permeating hydrogen signal generated from localized corrosion itself.A simulative localized corrosion was created on one side surface of the carbon steel specimen where a dot of wet elemental sulfur was introduced to accelerate the corrosion on the local region.While,the potential on the other side surface(the reverse side of the corrosion site)of the specimen was measured using a scanning Kelvin probe.The results show that the permeating hydrogen generated from localized corrosion easily arrives on the reverse side surface of the corrosion site and then causes a huge change in surface potential.The location resolution of potential distribution can be revealed with micron level.Therefore,it is thought that the location of localized corrosion can be recognized by the permeating hydrogen signal distribution on the reverse side surface of the corrosion site since the region of potential decreasing is highly corresponding to the corrosion site.Moreover,the strength of the permeating hydrogen signal is highly related to the corrosion depth and transient corrosion rate of localized corrosion.This means that the localized corrosion development can also be monitored using the permeating hydrogen signal.Therefore,it can be expected that the localized corrosion occurring on the inner wall surface of pipes or equipment can be recognized and monitored successfully on the outer wall surface in a non-destructive way once the permeating hydrogen is present during the localized corrosion proceeding.
基金funded by the National Natural Science Foundation of China Regional Innovation and Development Joint Fund(Sichuan)(No.U21A20417)the National Natural Science Foundation of China(No.31930067)。
文摘The androgenetic alopecia(AGA)is the most prevalent clinical manifestation of hair loss,believed to be associated with excessive dihydrotestosterone(DHT)caused by typeⅡ5α-reductase(5αR2).The utilization of oral finasteride(FNS),which selectively inhibits 5αR2,is frequently constrained by its adverse effects.Topical FNS formulations can mitigate adverse effects but often exhibit limited dermal permeability.Nanocarriers show great potential in augmenting the cutaneous permeation of loaded FNS due to their inherent properties of selective accumulation within the hair follicles(HFs).In this study,hollow mesoporous silica nanoparticles(HMSN)with varying sizes were utilized as the nanocarriers for FNS,following mixing with the Carbopol hydrogel(F@H/Gel)for direct topical application.Specifically,the influence of size on the targeted delivery of FNS to HFs,and its enhanced therapeutic efficacy for the AGA mice model was evaluated.Results showed that the HMSN,with a diameter of approximately 300 nm,exhibited significant enhancement in FNS retention within skin and HFs,as well as remarkably accelerated hair regrowth on an AGA mouse model.In conclusion,this FNS topical formulation has proved to be a viable approach in offering a secure and efficient treatment modality for AGA.
文摘A GC-MS method for the determination of 27 organochlorine pesticides and 15 Pyrethroid pesticides in animal food is established.The method was based on Gel Permeation chromatography combined with solid-phase extraction for sample preparation.Rapid qualitative and quantitative analyses was carried out by gas chromatography-mass spectrometry under the selective-ion monitoring mode.The experimental results showed that the correlation coefficients were better than 0.99,the recoveries for spiked standards were 70%-104%,the relative standard deviations were 2.1%-15.9%.
基金The Key Direction Program of Chinese Academy of Sciences(Grant No.kjcx2-sw-h12-01)
文摘One major problem encountered in transdermal drug delivery is the low permeability of drugs through the skin barrier. In the present study, we developed a surfactant-ethanolic liposomal system to improve the transdermal delivery of docetaxel （DTX）, a model drug for high molecular weight and poorly water-soluble drugs. Surfactant-ethanolic liposomes （SEL） were composed of phospholipids, ethanol, sodium cholate, DTX and PBS which were prepared by thin film dispersion method. The developed formulations were characterized by determining the vesicle shape and surface morphology, size and size distribution, entrapment efficiency and drug loading capacity. The effects of the developed formulations on the permeation of DTX across rat skin in vitro were investigated using the modified Franz diffusion cell under both occlusive and non-occlusive application condi- tions. The DTX SELs with optimum composition （phospholipid-surfactant, 85：15, w/w） provided a significantly higher steadystate amount of flux and cumulative permeation, compared to the tranditional liposomes, surfactant liposomes and ethanolic liposomes. The optimal SELs exhibited stable vesicle size, morphology and drug loading capacity. Our results indicated that SELs were promising carriers to enhance the transdermal delivery of DTX.
文摘For the production of reactive polyurethane cross-linkinger and curing agents, 2, 4-diisocyanate toluene （TDI） terpolymer, which possesses the rigid structures of hexatomic ring and three reactive functional groups, was synthesized and characterized by the Fourier transform infrared （FFIR）, the gel permeation chromatography （GPC） and the chemical analysis methods. The reaction conditions were studied and optimized. A tracking research on the polymerization process of TDI was taken by using the GPC. The formation processes of the terpolymer, oligomers and higher-polymers were also dealt with. Results show that the TDI terpolymer can be prepared in the presence of Cat-3 catalyst and at the reaction temperature of （60 ±2）℃. The reaction time is short, its outcomes have narrow molecular weights distribution, namely molecular weights from 530 to 550, Mw/Mn =1.10, and the mass fraction of NCO is （25. 0 ± 0. 5）%. With the reaction time prolonging, however, TDI can be further higher-polymedzed to form higher-polymers. Benzoyl chloride （0. 4%, mass fraction）, as the stabilizing agent, can effectively inhibit the occurrence of higher-polymerization. The obtained TDI terpolymer can be stable for more than half a year.
文摘The effect of pH on the permeation of Lidocaine hydrochloride (LH) across excised rat skin was studied, the steady state flux (JSS) at different pH being determined using improved Valia-Chien diffusion cells. JSS increased substantially when pH was close to the pKa of LH. The profile of JSS versus pH showed an 慡?shaped curve. JSS of Lidocaine free base (LFB) was fourteen times that of LH. The pH of vehicle influences the permeation of LH significantly and should be considered as an important factor when a formulation is developed.
文摘The phase composition, microstructure, thermal expansion coefficients, oxygen permeation properties and chemical stability of SrCo0.8Fe0.2O3-δ （SCFM） were investigated and compared with those of SrCo0.8Fe0.2O3-δ（SCF）. Single phase SCFM was successfully prepared by a combined EDTA-citric method. SCFM shows a lower thermal expansion coefficient （24× 10^-6-29× 10^-6/K） than SCF between 500 and 1050 ℃, indicating a more stable structure. SCFM shows a high oxygen permeation flux, although the oxygen flux of SCFM decreases slightly because of Mo dopant. Furthermore, it was demonstrated that the doping of Mo in SCF can prevent the order-disorder transition and improves the chemical stability to CO2.
文摘Rare earth (RE) atoms were permeated into the surface of Al bronze (Cu-7. gA1-1. 9 Sn) by the method of chemical heat treatment. The permeated layer was then analysed by TEM (Transmission Electron Microscope) , EPMA (Electronic Probe Microanalysis) and IMA (Ion Microprobe Appratus). The results show that CuREAl and dispersed η phase (Cu6Sn5) distribute in the layer, RE content decreases in the depth direction, and alloying elements (Al, Sn) are enriched in the outer layer and dilute in the second layer.
文摘Membrane fouling is the main problem of membrane bioreactors (MBR), which seriously influ- ences its wastewater treatment effect and running. The characteristics of microbiology and hydrodynamics concerning membrane fouling were investigated and the measure was put forward for optimum operation of MBR. The measure is that 1) the parameters of activated sludge concentration (X) and membrane flux should be lower than the critical values of X and membrane flux respectively, and 2) the activated sludge should be discharged periodically. The experimental results show that the combination backwashing of gas and perme- ated effluent is better than single gas backwashing or single permeated effluent backwashing. This technique can remove the cake layer deposited on the membrane surface, decrease the membrane fouling, and recover the membrane flux effectively. So it is effective for prevention of membrane fouling.
基金supported by the National Natural Science Foundation of China(51274152,41472071)the Fundamental Research Funds for the Central Universities,South-Central University for Nationalities(CZQ17011,CZP17070)the Scientific Research Foundation of South-Central University for Nationalities(YZZ16002)
文摘In order to reveal the permeability rule of leaching agent solution and the effects of anions in the leaching process of weathered crust elution-deposited rare earth（RE） ores, the effects of ammonium concentration, temperature, particle size and porosity on the permeability were discussed in detail with（NH4）2SO4, NH4Cl and NH4NO3 as the leaching agent. It was found that the permeation velocity of ammonium salts increased linearly with the increase of hydraulic gradient. The seepage of ammonium salts solution in the RE ores followed Darcy’s law and displayed a laminar flow. The properties of the leaching agent solution and RE ores were the main factors that affect the permeability of RE ores. With the decrease of ammonium concentration and increase of temperature, the viscosity of solution decreased and the permeability coefficients of RE ores increased. And the effects of temperature on the viscosity and permeability were larger than ammonium concentration. The permeability of RE ores became worse with the decrease of particle size and porosity, and the particle size played a more important role compared with porosity. The permeability coefficient of RE ores increased and the viscosity of ammonium salts solution decreased in the order of（NH4）2SO4, NH4Cl and NH4NO3, implying that the penetrating power of anions increased in the order of SO42-, Cl- and NO3-. The results may play a vital role in improving the permeability of weathered crust elution-deposited RE ores.
基金Project supported by the National Natural Science Foundation of China(51401021)the State Key Laboratory Advanced Metals and Materials(20162-14).
文摘Different from the grain boundary diffusion process(GBDP),which is suitable for modifying thin magnet,a green-pressing agents permeation process(GAPP)that uses low melting point alloys was applied to the Nd-Fe-B green compact with a thickness over 15 mm to reconstruct the boundary microstructure of a sintered Nd-Fe-B magnet.The coercivity increases from 12.3 kOe for the sample free of Pr80Al20 to16.8 kOe for the sample with 2 wt%Pr80Al20.By further increasing the Pr80Al20 content to 3 wt%,the coercivity increases slightly,but the remanence and Hk/Hcj deteriorate obviously.The optimal comprehensive properties of Hcj=16.8 kOe,Br=13.4 kG and Hk/Hcj=0.975 are obtained at 2 wt%Pr80Al20,since matrix phase grains are separated by relatively continuous thin grain boundary layers,which weaken the magnetic coupling between adjacent grains.The coercivities of the samples from the GAPP that use2 wt%Pr80Al20,Pr70Al30 and Pr60Tb20Al20 alloys,respectively,can be enhanced to a large extent.However,the coercivity of the magnet reconstructed with Pr80Al20 is lower than that of the sample with Pr60Tb20Al20 but is higher than that of the sample reconstructed with Pr70Cu30 alloy.Moreover,the coercivity of the sample from the GAPP using 2 wt%Pr80Al20 is much higher than that of the sample from the GBDP,which is due to a nearly uniform boundary microstructure from the surface to the interior of the thick magnet from the GAPP,thus providing new insights into the fabrication of thick and bulky permanent magnets with high coercivity.
基金Item Sponsored by CITIC-CBMM Niobium Steel Research and Development Projects of China(2007RMJS-D031)
文摘Influence of vanadium and/or niobium additions on delayed fracture behavior in high strength spring steel was studied by hydrogen permeation method and slow strain rate technique （8SRT）, and its mechanism was analyzed. The results show that apparent diffusion coefficient of hydrogen in microalloyed spring steels Nb-V-steel and Nb-steel is lower than that in non-microalloyed steel 60Si2MnA. Percentage of strength reduction in SSRT in air after precharged hydrogen of the microalloyed steels is smaller than that of 60Si2MnA. Addition of the microalloys changes the fracture characteristics. Thence, vanadium and/or niobium additions are a very effective and economy means to improve the hydrogen-induced delayed fracture resistance of high strength spring steel.
文摘Grout injection is used for sealing or strengthening the ground in order to prevent water entrance or any failure after excavation.There are many methods of grouting.Permeation grouting is one of the most common types in which the grout material is injected to the pore spaces of the ground.In grouting operations,the grout quality is important to achieve the best results.There are four main characteristics for a grout mixture including bleeding,setting time,strength,and viscosity.In this paper,we try to build some efficient grouting mixtures with different water to cement ratios considering these characteristics.The ingredients of grout mixtures built in this study are cement,water,bentonite,and some chemical additives such as sodium silicate,sodium carbonate,and triethanolamine(TEA).The grout mixtures are prepared for both of the sealing and strengthening purposes for a structural project.Effect of each abovementioned ingredient is profoundly investigated.Since each ingredient may have positive or negative aspect,an optimization of appropriate amount of each ingredient is determined.The optimization is based on 200 grout mixture samples with different percentages of ingredients.Finally,some of these grout mixtures are chosen for the introduced project.It should be mentioned that grouting operations depend on various factors such as pressure of injection,ground structure and grain size of soils.However,quality of a grout can be helpful to make an injection easier and reasonable.For example,during the injection,a wrong estimated setting time can destroy the injected grout by washing the grout or setting early which prevents grouting.This paper tries to show some tests in easy way to achieve a desirable sample of grout.
文摘Polyvinylidenefluoride （PVDF） hollow fiber ultrafiltration membrane is frequently employed in water treatment. However, the fouling of ultrafiltration membranes affects the economic effectiveness of such process significantly. The ultrasound generated by flat plate transducer （UFPT） was used to clean the polluted PVDF ultrafiltration membrane with 2 g·L^-1 of citric acid aqueous solution in our study. The effects of UFPT intensity on the membrane surface were studied. The new membrane was easy to be polluted by the saturated CaCl2 solution. A synergistic effect of UFPT and 2 g·L^-1 citric acid aqueous solution could remove the foul of the membrane, and its flux could be recovered about 81%. The flux recovery of old membrane polluted was increased to 73.2% after 7 h soaking in citric acid aqueous solution, but its flux recovery without soaking was only increased to 56.2%.
基金the National Natural Science Foundation of China (No. 50674015)
文摘A hydrogen permeation barrier was manufactured by the in situ reaction of zirconium hydride with oxygen. A reduction in the hydrogen permeation of the oxide films was detected by measuring the mass difference of the zirconium hydride samples after the dehydrogenation experiment. The reaction of zirconium hydride with oxygen occurs only under the condition that the temperature is higher than 673 K in the oxygen partial pressure of 0.1 MPa. The oxide film is composed of two layers, a permeable oxide layer and a dense oxide layer, and the main phase of the oxide film is ZrO2 with baddeleyite structure. The XPS analysis shows that O-H bonds exist in the oxide film, which are helpful for resisting hydrogen diffusion through the oxide film.
基金Supported by the National Natural Science Foundation of China （20776065）, the Natural Science Foundation of Jiangsu Province （BK2008023）, and the National Found for Fostering Talents of Basic Science 00630425）.
文摘Permeabilities and selectivities of gases such as carbon dioxide （CO2）, sulfur dioxide （SO2）, nitrogen （N2） and methane （CH4） in six imidazolium-based ionic liquids （[emim][BF4], [bmim][BF4], [bmim][PF6], [banim][BF4], [bmim][Tf2N] and [emim][CF3SO3]） supported on polyethersulfone microfiltration membranes are investigated in a single gas feed system using nitrogen as the environment and reference component at temperature from 25 to 45℃ and pressure of N2 from 100 to 400 kPa. It is found that SO2 has the highest permeability in the tested supported ionic liquid membranes, being an order of magnitude higher than that of CO2, and about 2 to 3 orders of magnitude larger than those of N2 and CH4. The observed selectivity of SO2 over the two ordinary gas components is also striking. It is shown experimentally that the dissolution and transport of gas components in the supported ionic liquid membranes, as well as the nature of ionic liquids play important roles in the gas permeation. A nonlinear increase of permeation rate with temperature and operation pressure is also observed for all sample gases. By considering the factors that influence the permeabilities and selectivities of CO2 and SO2, it is expected to develop an optimal supported ionic liquid membrane technology for the isolation of acidic gases in the near future.
文摘This paper reports a study on the role of fluid flow pattern and dynamic pressure on the permeate flux through a micro filtration membrane in laboratory scale.For this purpose,a dead-end membrane cell equipped with a marine type impeller was used.The impeller was set to rotate in the clockwise and counter clockwise directions with the same angular velocities in order to illustrate the effect of rotation direction on permeate flux.Consequently, permeate fluxes were measured at various impeller rotational speeds.The computational fluid dynamics（CFD）predicted dynamic pressure was related to the fluxes obtained in the experiments.Using the CFD modeling,it is proven that the change in dynamic pressure upon the membrane surface has direct effect on the permeate flux.
