Non-aqueous emulsions have a wide range of applications in cosmetics,drug-controlled release,and the preparation of functional nanoparticles.However,due to the weaker polarity of non-aqueous solvents,these emulsions o...Non-aqueous emulsions have a wide range of applications in cosmetics,drug-controlled release,and the preparation of functional nanoparticles.However,due to the weaker polarity of non-aqueous solvents,these emulsions often exhibit inferior stability compared to their aqueous counterparts.In this experiment,the properties of quaternary ammonium surfactants in glycerol were investigated through surface tension measurements,to further enhance the stability of n-decane/glycerol emulsions,hydrophilic nanoparticles SiO_(2) were modified in situ using double tailed quaternary ammonium surfactants Di-C_(12)DAB and Di-C_(16)DAB.Stable n-decane/glycerol Pickering emulsions were successfully prepared.These emulsions were stable at 45℃for over six months,and no significant changes in droplet size occurred.The minimum droplet size of the emulsion was only 2-3μm.Contact angle measurements showed that the wettability of the silica surface was tremendously affected by the concentration and the alkyl chain length of the double-tailed surfactants.In the presence of Di-C_(12)DAB,the contact angle of glycerol on the silica surface increased monotonically with the surfactant concentration.This explains the phenomenon that the Pickering emulsions containing Di-C_(12)DAB and silica particles were stable within the contact angle range of 80°-120°.Comparatively,the contact angle of the glycerol on the silica surface in the presence of Di-C_(16)DAB first increased with surfactant concentrations and then decreased,reaching a maximum at 0.6 mmol/L.It can be concluded that Di-C_(12)DAB formed monolayers at the surface of silica particles within all investigated concentrations.On the contrary,Di-C_(16)DAB formed monolayers at concentrations below 0.6 mmol/L and formed double layers at concentrations above 0.6 mmol/L,leading to a non-monotonic change in the contact angle with respect to concentration.Using these stable non-aqueous Pickering emulsions as templates,polymer microspheres with a particle size of 2-3μm were successfully prepared with high yield.This work is helpful to expand the potential applications of non-aqueous emulsions in the encapsulation of drug,controlled release,material preparation,and cosmetic formulations.展开更多
High-overload shocks are very likely to cause damage to the microstructure of MEMS devices, especially the continuous multiple high-overload shocks generated by the penetration of the multilayer target environment pos...High-overload shocks are very likely to cause damage to the microstructure of MEMS devices, especially the continuous multiple high-overload shocks generated by the penetration of the multilayer target environment pose more stringent challenges to its protective structure. In this study, the kinetic response model of the protective structure under single-pulse and continuous double-pulse impact is established,and a continuous double-pulse high overload impact test impact platform based on the sleeve-type bullet is constructed, and the protective performance of the multi-layer structure under multi-pulse is analyzed based on the acceleration decay ratio, and the results show that the protective performance of the structure has a positive correlation with its thickness, and it is not sensitive to the change of the load of the first impact;the first impact under double-pulse impact will cause damage to the microstructure through the superposition of the second impact. The first impact under double-pulse impact will cause an increase in the overload amplitude of the second impact through superposition;compared with the single-layer structure, the acceleration attenuation ratio of the double-layer structure can be increased by up to 26.13%, among which the epoxy-polyurethane combination has the best protection performance, with an acceleration attenuation ratio of up to 44.68%. This work provides a robust theoretical foundation and experimental basis for the reliable operation of MEMS devices, as well as for the design of protective structures in extreme environments.展开更多
In the traditional strength reduction method,the cohesion and the friction angle adopt the same reduction parameter,resulting in equivalent proportional reduction.This method does not consider the different effects of...In the traditional strength reduction method,the cohesion and the friction angle adopt the same reduction parameter,resulting in equivalent proportional reduction.This method does not consider the different effects of the cohesion and friction angle on the stability of the same slope and is defective to some extent.Regarding this defect,a strength reduction method based on double reduction parameters,which adopts different reduction parameters,is proposed.The core of the double-parameter reduction method is the matching reduction principle of the slope with different angles.This principle is represented by the ratio of the reduction parameter of the cohesion to that of the friction angle,described as η.With the increase in the slopeangle,ηincreases; in particular,when the slope angle is 45°,tηis 1.0.Through the matching reduction principle,different safety margin factors can be calculated for the cohesion and friction angle.In combination with these two safety margin factors,a formula for calculating the overall safety factor of the slope is proposed,reflecting the different contributions of the cohesion and friction angle to the slope stability.Finally,it is shown that the strength reduction method based on double reduction parameters acquires a larger safety factor than the classic limit equilibrium method,but the calculation results are very close to those obtained by the limit equilibrium method.展开更多
Preparation of cast double-propellant grains depends on the ability of nitrocellulose powder to swell and coalesce into a coherent mass when treated with a suitable solvent.The cast double-base process has been develo...Preparation of cast double-propellant grains depends on the ability of nitrocellulose powder to swell and coalesce into a coherent mass when treated with a suitable solvent.The cast double-base process has been developed into a highly versatile technique for manufacturing solid rocket charges.Propellants manufactured by this process provide a wide range of energies and burning rates.Successful preparation of cast double-base propellant grains has been performed using compatible casting liquid with the casting powder.BuNENA was used as an energetic plasticizer for manufacturing of casting powder.Burning rate measurements have been performed using closed bomb SV-2to investigate the burning behavior along a wide range of operating pressure.Plateau burning had been detected in pressure range(50-70)×105 Pa for the composition included BuNENA.DTA and TGA thermal analysis were conducted to evaluate the thermal behavior of the prepared cast double-base propellants.Results from DTA were used to calculate the apparent activation energy.展开更多
On the basis of the gain-scheduled H∞ design strategy, a novel active fault-tolerant control scheme is proposed. Under the assumption that the effects of faults on the state-space matrices of systems can be of affine...On the basis of the gain-scheduled H∞ design strategy, a novel active fault-tolerant control scheme is proposed. Under the assumption that the effects of faults on the state-space matrices of systems can be of affine parameter dependence, a reconfigurable robust H∞ linear parameter varying controller is developed. The designed controller is a function of the fault effect factors that can be derived online by using a well-trained neural network. To demonstrate the effectiveness of the proposed method, a double inverted pendulum system, with a fault in the motor tachometer loop, is considered.展开更多
The purpose of initial orbit determination,especially in the case of angles-only data for observation,is to obtain an initial estimate that is close enough to the true orbit to enable subsequent precision orbit determ...The purpose of initial orbit determination,especially in the case of angles-only data for observation,is to obtain an initial estimate that is close enough to the true orbit to enable subsequent precision orbit determination processing to be successful.However,the classical angles-only initial orbit determination methods cannot deal with the observation data whose Earth-central angle is larger than 360°.In this paper,an improved double r-iteration initial orbit determination method to deal with the above case is presented to monitor geosynchronous Earth orbit objects for a spacebased surveillance system.Simulation results indicate that the improved double r-iteration method is feasible,and the accuracy of the obtained initial orbit meets the requirements of re-acquiring the object.展开更多
Pt and Ir coatings were produced by double glow plasma technology on the surface of Ti alloy substrates. The chemical compositions of the coatings were determined by X-ray diffraction and X-ray photoelectron spectrosc...Pt and Ir coatings were produced by double glow plasma technology on the surface of Ti alloy substrates. The chemical compositions of the coatings were determined by X-ray diffraction and X-ray photoelectron spectroscopy. The microstructure and morphology of the coatings were observed by scanning electron microscopy. The hardness and elastic modulus of the coatings were estimated by nanoindentation. The measurements of adhesive forces of the coatings were performed with scratch tester. The results indicated that the Pt and Ir coatings displayed the preferred (220) orientation due to the initial nuclei with preferred growth on the surface of the substrates. The interface between the Pt coating and substrate exhibited no evidence of delamination. The Ir coating was composed of irregular columnar grains with many nanovoids at the interface between the coating and substrate. The mean values of hardness for Pt and Ir coatings were 0.9 GPa and 9 GPa, respectively. The elastic modulus of Pt and Ir coatings were 178 GPa and 339 GPa, respectively. The adhesive forces of the Pt and Ir coatings were about 66.4 N and 55 N, respectively. The Pt and Ir coatings adhered well to the Ti alloy substrates.展开更多
文摘Non-aqueous emulsions have a wide range of applications in cosmetics,drug-controlled release,and the preparation of functional nanoparticles.However,due to the weaker polarity of non-aqueous solvents,these emulsions often exhibit inferior stability compared to their aqueous counterparts.In this experiment,the properties of quaternary ammonium surfactants in glycerol were investigated through surface tension measurements,to further enhance the stability of n-decane/glycerol emulsions,hydrophilic nanoparticles SiO_(2) were modified in situ using double tailed quaternary ammonium surfactants Di-C_(12)DAB and Di-C_(16)DAB.Stable n-decane/glycerol Pickering emulsions were successfully prepared.These emulsions were stable at 45℃for over six months,and no significant changes in droplet size occurred.The minimum droplet size of the emulsion was only 2-3μm.Contact angle measurements showed that the wettability of the silica surface was tremendously affected by the concentration and the alkyl chain length of the double-tailed surfactants.In the presence of Di-C_(12)DAB,the contact angle of glycerol on the silica surface increased monotonically with the surfactant concentration.This explains the phenomenon that the Pickering emulsions containing Di-C_(12)DAB and silica particles were stable within the contact angle range of 80°-120°.Comparatively,the contact angle of the glycerol on the silica surface in the presence of Di-C_(16)DAB first increased with surfactant concentrations and then decreased,reaching a maximum at 0.6 mmol/L.It can be concluded that Di-C_(12)DAB formed monolayers at the surface of silica particles within all investigated concentrations.On the contrary,Di-C_(16)DAB formed monolayers at concentrations below 0.6 mmol/L and formed double layers at concentrations above 0.6 mmol/L,leading to a non-monotonic change in the contact angle with respect to concentration.Using these stable non-aqueous Pickering emulsions as templates,polymer microspheres with a particle size of 2-3μm were successfully prepared with high yield.This work is helpful to expand the potential applications of non-aqueous emulsions in the encapsulation of drug,controlled release,material preparation,and cosmetic formulations.
基金supported by Fund of the National Natural Science Foundation of China (Grant No. 52375553)。
文摘High-overload shocks are very likely to cause damage to the microstructure of MEMS devices, especially the continuous multiple high-overload shocks generated by the penetration of the multilayer target environment pose more stringent challenges to its protective structure. In this study, the kinetic response model of the protective structure under single-pulse and continuous double-pulse impact is established,and a continuous double-pulse high overload impact test impact platform based on the sleeve-type bullet is constructed, and the protective performance of the multi-layer structure under multi-pulse is analyzed based on the acceleration decay ratio, and the results show that the protective performance of the structure has a positive correlation with its thickness, and it is not sensitive to the change of the load of the first impact;the first impact under double-pulse impact will cause damage to the microstructure through the superposition of the second impact. The first impact under double-pulse impact will cause an increase in the overload amplitude of the second impact through superposition;compared with the single-layer structure, the acceleration attenuation ratio of the double-layer structure can be increased by up to 26.13%, among which the epoxy-polyurethane combination has the best protection performance, with an acceleration attenuation ratio of up to 44.68%. This work provides a robust theoretical foundation and experimental basis for the reliable operation of MEMS devices, as well as for the design of protective structures in extreme environments.
基金Project(KZCX2-YW-T12)supported by the Chinese Academy of Science,China
文摘In the traditional strength reduction method,the cohesion and the friction angle adopt the same reduction parameter,resulting in equivalent proportional reduction.This method does not consider the different effects of the cohesion and friction angle on the stability of the same slope and is defective to some extent.Regarding this defect,a strength reduction method based on double reduction parameters,which adopts different reduction parameters,is proposed.The core of the double-parameter reduction method is the matching reduction principle of the slope with different angles.This principle is represented by the ratio of the reduction parameter of the cohesion to that of the friction angle,described as η.With the increase in the slopeangle,ηincreases; in particular,when the slope angle is 45°,tηis 1.0.Through the matching reduction principle,different safety margin factors can be calculated for the cohesion and friction angle.In combination with these two safety margin factors,a formula for calculating the overall safety factor of the slope is proposed,reflecting the different contributions of the cohesion and friction angle to the slope stability.Finally,it is shown that the strength reduction method based on double reduction parameters acquires a larger safety factor than the classic limit equilibrium method,but the calculation results are very close to those obtained by the limit equilibrium method.
文摘Preparation of cast double-propellant grains depends on the ability of nitrocellulose powder to swell and coalesce into a coherent mass when treated with a suitable solvent.The cast double-base process has been developed into a highly versatile technique for manufacturing solid rocket charges.Propellants manufactured by this process provide a wide range of energies and burning rates.Successful preparation of cast double-base propellant grains has been performed using compatible casting liquid with the casting powder.BuNENA was used as an energetic plasticizer for manufacturing of casting powder.Burning rate measurements have been performed using closed bomb SV-2to investigate the burning behavior along a wide range of operating pressure.Plateau burning had been detected in pressure range(50-70)×105 Pa for the composition included BuNENA.DTA and TGA thermal analysis were conducted to evaluate the thermal behavior of the prepared cast double-base propellants.Results from DTA were used to calculate the apparent activation energy.
文摘On the basis of the gain-scheduled H∞ design strategy, a novel active fault-tolerant control scheme is proposed. Under the assumption that the effects of faults on the state-space matrices of systems can be of affine parameter dependence, a reconfigurable robust H∞ linear parameter varying controller is developed. The designed controller is a function of the fault effect factors that can be derived online by using a well-trained neural network. To demonstrate the effectiveness of the proposed method, a double inverted pendulum system, with a fault in the motor tachometer loop, is considered.
文摘The purpose of initial orbit determination,especially in the case of angles-only data for observation,is to obtain an initial estimate that is close enough to the true orbit to enable subsequent precision orbit determination processing to be successful.However,the classical angles-only initial orbit determination methods cannot deal with the observation data whose Earth-central angle is larger than 360°.In this paper,an improved double r-iteration initial orbit determination method to deal with the above case is presented to monitor geosynchronous Earth orbit objects for a spacebased surveillance system.Simulation results indicate that the improved double r-iteration method is feasible,and the accuracy of the obtained initial orbit meets the requirements of re-acquiring the object.
基金supported by the National Natural Science Foundation of China(50872055/E020703)Funding for Outstanding Doctoral Dissertation in NUAA(BCXJ1109)the Funding of Jiangsu Innovation Program for Graduate Education(CXLX11_0207)
文摘Pt and Ir coatings were produced by double glow plasma technology on the surface of Ti alloy substrates. The chemical compositions of the coatings were determined by X-ray diffraction and X-ray photoelectron spectroscopy. The microstructure and morphology of the coatings were observed by scanning electron microscopy. The hardness and elastic modulus of the coatings were estimated by nanoindentation. The measurements of adhesive forces of the coatings were performed with scratch tester. The results indicated that the Pt and Ir coatings displayed the preferred (220) orientation due to the initial nuclei with preferred growth on the surface of the substrates. The interface between the Pt coating and substrate exhibited no evidence of delamination. The Ir coating was composed of irregular columnar grains with many nanovoids at the interface between the coating and substrate. The mean values of hardness for Pt and Ir coatings were 0.9 GPa and 9 GPa, respectively. The elastic modulus of Pt and Ir coatings were 178 GPa and 339 GPa, respectively. The adhesive forces of the Pt and Ir coatings were about 66.4 N and 55 N, respectively. The Pt and Ir coatings adhered well to the Ti alloy substrates.
