The growth of vitamin C single crystals was studied by direct observation In flowing solution, the linear growth rates of three orientations (, , ) were measured for vitamin C water system The experiments were designe...The growth of vitamin C single crystals was studied by direct observation In flowing solution, the linear growth rates of three orientations (, , ) were measured for vitamin C water system The experiments were designed as orthogonal test to investigate the effect of various factors Comparing with temperature and velocity, supersaturation is the most important factor And the relations between growth and supersaturation were different with crystal directions, which obviously show anisotropy The order of magnitude of G , G , G and their dependency on supersaturation ( g , g , g ) were in good agreement with analysis of maximum difference The effect of solution diffusion could be neglected and crystal growth was controlled by surface reaction According to the growth models, the growth mechanism was展开更多
This paper reports the influence of heat transfer surface treatment on the formation of calcium sulphate de-posit during flow boiling heat transfer. The surface of several test heaters was treated by surface modificat...This paper reports the influence of heat transfer surface treatment on the formation of calcium sulphate de-posit during flow boiling heat transfer. The surface of several test heaters was treated by surface modification techniques, such as dynamic mixing magnetron sputtering [DLC (diamond-like carbon), DLC-F (diamond-like carbon-fluorine) and AC (amorphous carbon)] and polishing to reduce surface energy. The results showed that heat transfer surface with low surface energy experienced significant reduction of formation of CaSO4 deposit. (1) Magnetron sputtering stainless steel heat transfer surface with DLC, DLC-F and plasma arc sputtering with AC did not change the surface roughness, but they reduced surface energy and improved heat transfer coefficient, so hindered CaSO4 deposit formation significantly. The DLC-F surface performed better than the DLC surface. (2) Surface energy played an important pole in improving heat transfer coefficient. The less the surface energy the more significant the heat transfer coefficient improved with other ex-perimental conditions identical. (3) The polished surface improved the roughness of the heater, but owing to the high sur-face energy it was not better than the DLC-F surface for a long-term consideration on improving the heat transfer coeffi-cient.展开更多
By means of HAAKE RS105L cone and plate rheometer the concentrated solution, including viscous flow activation energy, non-Newtonian index, structural viscosity index and relaxation time of the PMIA solution were stud...By means of HAAKE RS105L cone and plate rheometer the concentrated solution, including viscous flow activation energy, non-Newtonian index, structural viscosity index and relaxation time of the PMIA solution were studied. The effect of concentration and temperature of the solution and molecular weight of the polymer on its non-Newtonian behavior was investigated. The results showed that PMIA concentrated solution prepared via low temperature condensation was of non-Newtonian fluid. With the decrease of temperature, increase of solution concentration and PMIA molecular weight, the deviation of the solution from Newtonian behavior decreased. The molecular weight of the polymer and the concentration of the solution affected the non- Newtonian behavior mete intensively.展开更多
Plasma like concept of ions in electrolyte solutions is accepted as a basis for development of equation mobility for transfer processes （viscosity, diffusion, thermal conductivity and electrical conductivity）. The e...Plasma like concept of ions in electrolyte solutions is accepted as a basis for development of equation mobility for transfer processes （viscosity, diffusion, thermal conductivity and electrical conductivity）. The examples of isomorphism of dissipative processes are given in the article. The integrated assessment equation of transfer properties is developed based on the ion-dipole, dipole-dipole and ion-ion interactions and the force of liquid dielectric resistance to oscillating solvated particles. It is shown that the estimated magnitude of viscosity, diffusion, electrical conductivity and thermal conductivity are comparable with the current knowledge and experimental values in a wide range of electrolyte concentrations.展开更多
Egg yolk phosphatidylcholine(EYPC) is being widely used in food and pharmaceutical industries nowadays owing to its surface activity,pharmaceutical usefulness,and so on.Common determination methods of phospholipids we...Egg yolk phosphatidylcholine(EYPC) is being widely used in food and pharmaceutical industries nowadays owing to its surface activity,pharmaceutical usefulness,and so on.Common determination methods of phospholipids were based on the American Oil Chemists' Society(AOCS) Official Method Ja7b-91,in which n-hexane/2-propanol/acetate buffer was used as the mobile phase.In order to achieve desired results,gradient elu-tion or buffer solution was used,which made the detection process more complicated.Moreover,water or buffer solution could affect the silica gel column both on its lifespan and the separation efficiency significantly.In this study,different mobile phase and detector were used to simplify EYPC analyzing process instead of using water within the mobile phase.The optimized HPLC operating conditions are as follows:pure methanol as a mobile phase,flow rate of 1.0 ml·min-1,silica gel column(250 mm×4.6 mm,5 μm,Inertsil GLTM),column temperature 30 ℃ and low temperature evaporative light scattering detector(40 ℃,0.35 MPa) as used.Under this optimal condition,the linear relative coefficient of the standard curve is 0.998 and the recovery was in the range of 96.83%-101.58% with a relative standard deviation of 1.79%(n=6).展开更多
Direct numerical simulation(DNS) of forcing homogeneous isotropic turbulence with polymers was performed.In order to understand the polymers effect on turbulent coherent structures,proper orthogonal decomposition was ...Direct numerical simulation(DNS) of forcing homogeneous isotropic turbulence with polymers was performed.In order to understand the polymers effect on turbulent coherent structures,proper orthogonal decomposition was performed to identify coherent structures based on DNS data,so as to analyze the remarkable difference due to the addition of polymers.The results showed that the numbers for eigenmodes required for capturing coherent structures were 32 and 24 for the Newtonian fluid and polymer solution flows,respectively,which means the decrease of the complexity in polymer solution flow.Through the POD energy spectrum,it was found that the turbulent kinetic energy is distributed onto a large number of eigenmodes whether in the Newtonian fluid flow or polymer solution flow,suggesting that polymer solution flow is still turbulent in one aspect.Besides,the POD eigenmodes were investigated,which found that the small-scale structures are inhibited in polymer solution flow.展开更多
The changes of free solution amount, fluidity and the time-depended fluidity loss of cement paste were examined by varying the water-cement ratio and the dosages of superplasticizer. The distribution of solution and f...The changes of free solution amount, fluidity and the time-depended fluidity loss of cement paste were examined by varying the water-cement ratio and the dosages of superplasticizer. The distribution of solution and flocculation microstructure in flesh cement paste was observed with optical microscope. The change of free solution amount and its effect on the fluidity and bleeding of cement paste was studied. The results show that the adsorbed solution amount has a great influence on the com- patibility of cement-superplasticizer system, including the bleeding degree, the fluidity and the time-depended fluidity loss of cement paste. Superplasticizer increases the fluidity of cement paste by destroying the flocculated cement particle structure and increasing the amount of adsorbed solution. Polycarboxylate superplasticizer shows higher ability of adsorption than naphtha- lene superplasticizer. Over dosage of superplasticizer is not the primary cause of bleeding. The principle reason of bleeding is the high water-cement ratio and the insufficient enhancing ability of water adsorption of superplasticizer.展开更多
Pressure-sensitive paint(PSP) technique was employed to experimentally investigate the aerodynamic force effect of vacuum plume in this study. The characterization and comparison for two types of PSP were firstly cond...Pressure-sensitive paint(PSP) technique was employed to experimentally investigate the aerodynamic force effect of vacuum plume in this study. The characterization and comparison for two types of PSP were firstly conducted in an air pressure range from0.05 to 5000 Pa. The PSPs were prepared using PtTFPP as the active dye and different binders, i.e., polymer-ceramic(PC) and poly(1-trimethylsilyl-1-propyne) [poly(TMSP)]. The static calibrations showed that PtTFPP/poly(TMSP) had a higher pressure sensitivity and a lower temperature dependency compared to PtTFPP/PC in this pressure range. The pressure distributions of a single and two interacting plumes impinging onto a flat plate model were measured using PSP technique. The experimental data were compared to numerical solutions that combined both the computed fluid dynamics(CFD) and direct simulation Monte Carlo(DSMC) methods. Remarkable agreements were achieved, demonstrating the feasibility and accuracy of the numerical approach.Finally, the aerodynamic force effect of interacting plumes at different separation distances was investigated numerically.展开更多
文摘The growth of vitamin C single crystals was studied by direct observation In flowing solution, the linear growth rates of three orientations (, , ) were measured for vitamin C water system The experiments were designed as orthogonal test to investigate the effect of various factors Comparing with temperature and velocity, supersaturation is the most important factor And the relations between growth and supersaturation were different with crystal directions, which obviously show anisotropy The order of magnitude of G , G , G and their dependency on supersaturation ( g , g , g ) were in good agreement with analysis of maximum difference The effect of solution diffusion could be neglected and crystal growth was controlled by surface reaction According to the growth models, the growth mechanism was
基金Supported by the Special Fund for Excellent Talents from Beijing Communist Party Organization Division, fund for Excellent Talents Reinforce Education Plan for Universities under Beijing City Administration (Z03-16).
文摘This paper reports the influence of heat transfer surface treatment on the formation of calcium sulphate de-posit during flow boiling heat transfer. The surface of several test heaters was treated by surface modification techniques, such as dynamic mixing magnetron sputtering [DLC (diamond-like carbon), DLC-F (diamond-like carbon-fluorine) and AC (amorphous carbon)] and polishing to reduce surface energy. The results showed that heat transfer surface with low surface energy experienced significant reduction of formation of CaSO4 deposit. (1) Magnetron sputtering stainless steel heat transfer surface with DLC, DLC-F and plasma arc sputtering with AC did not change the surface roughness, but they reduced surface energy and improved heat transfer coefficient, so hindered CaSO4 deposit formation significantly. The DLC-F surface performed better than the DLC surface. (2) Surface energy played an important pole in improving heat transfer coefficient. The less the surface energy the more significant the heat transfer coefficient improved with other ex-perimental conditions identical. (3) The polished surface improved the roughness of the heater, but owing to the high sur-face energy it was not better than the DLC-F surface for a long-term consideration on improving the heat transfer coeffi-cient.
文摘By means of HAAKE RS105L cone and plate rheometer the concentrated solution, including viscous flow activation energy, non-Newtonian index, structural viscosity index and relaxation time of the PMIA solution were studied. The effect of concentration and temperature of the solution and molecular weight of the polymer on its non-Newtonian behavior was investigated. The results showed that PMIA concentrated solution prepared via low temperature condensation was of non-Newtonian fluid. With the decrease of temperature, increase of solution concentration and PMIA molecular weight, the deviation of the solution from Newtonian behavior decreased. The molecular weight of the polymer and the concentration of the solution affected the non- Newtonian behavior mete intensively.
文摘Plasma like concept of ions in electrolyte solutions is accepted as a basis for development of equation mobility for transfer processes （viscosity, diffusion, thermal conductivity and electrical conductivity）. The examples of isomorphism of dissipative processes are given in the article. The integrated assessment equation of transfer properties is developed based on the ion-dipole, dipole-dipole and ion-ion interactions and the force of liquid dielectric resistance to oscillating solvated particles. It is shown that the estimated magnitude of viscosity, diffusion, electrical conductivity and thermal conductivity are comparable with the current knowledge and experimental values in a wide range of electrolyte concentrations.
文摘Egg yolk phosphatidylcholine(EYPC) is being widely used in food and pharmaceutical industries nowadays owing to its surface activity,pharmaceutical usefulness,and so on.Common determination methods of phospholipids were based on the American Oil Chemists' Society(AOCS) Official Method Ja7b-91,in which n-hexane/2-propanol/acetate buffer was used as the mobile phase.In order to achieve desired results,gradient elu-tion or buffer solution was used,which made the detection process more complicated.Moreover,water or buffer solution could affect the silica gel column both on its lifespan and the separation efficiency significantly.In this study,different mobile phase and detector were used to simplify EYPC analyzing process instead of using water within the mobile phase.The optimized HPLC operating conditions are as follows:pure methanol as a mobile phase,flow rate of 1.0 ml·min-1,silica gel column(250 mm×4.6 mm,5 μm,Inertsil GLTM),column temperature 30 ℃ and low temperature evaporative light scattering detector(40 ℃,0.35 MPa) as used.Under this optimal condition,the linear relative coefficient of the standard curve is 0.998 and the recovery was in the range of 96.83%-101.58% with a relative standard deviation of 1.79%(n=6).
基金supported by the National Natural Science Foundation of China (Grant No.10872060)the Fundamental Research Funds for the Central Universities (Grant Nos.HIT.BRET1.2010008, HIT.NSRIF.2012070)+1 种基金the Doctoral Fund of Ministry of Education of China (Grant No.20112302110020)the China Postdoctoral Science Foundation (Grant No.2011M500652)
文摘Direct numerical simulation(DNS) of forcing homogeneous isotropic turbulence with polymers was performed.In order to understand the polymers effect on turbulent coherent structures,proper orthogonal decomposition was performed to identify coherent structures based on DNS data,so as to analyze the remarkable difference due to the addition of polymers.The results showed that the numbers for eigenmodes required for capturing coherent structures were 32 and 24 for the Newtonian fluid and polymer solution flows,respectively,which means the decrease of the complexity in polymer solution flow.Through the POD energy spectrum,it was found that the turbulent kinetic energy is distributed onto a large number of eigenmodes whether in the Newtonian fluid flow or polymer solution flow,suggesting that polymer solution flow is still turbulent in one aspect.Besides,the POD eigenmodes were investigated,which found that the small-scale structures are inhibited in polymer solution flow.
基金supported by the National Natural Science Foundation of China (Grant No.50772053)
文摘The changes of free solution amount, fluidity and the time-depended fluidity loss of cement paste were examined by varying the water-cement ratio and the dosages of superplasticizer. The distribution of solution and flocculation microstructure in flesh cement paste was observed with optical microscope. The change of free solution amount and its effect on the fluidity and bleeding of cement paste was studied. The results show that the adsorbed solution amount has a great influence on the com- patibility of cement-superplasticizer system, including the bleeding degree, the fluidity and the time-depended fluidity loss of cement paste. Superplasticizer increases the fluidity of cement paste by destroying the flocculated cement particle structure and increasing the amount of adsorbed solution. Polycarboxylate superplasticizer shows higher ability of adsorption than naphtha- lene superplasticizer. Over dosage of superplasticizer is not the primary cause of bleeding. The principle reason of bleeding is the high water-cement ratio and the insufficient enhancing ability of water adsorption of superplasticizer.
文摘Pressure-sensitive paint(PSP) technique was employed to experimentally investigate the aerodynamic force effect of vacuum plume in this study. The characterization and comparison for two types of PSP were firstly conducted in an air pressure range from0.05 to 5000 Pa. The PSPs were prepared using PtTFPP as the active dye and different binders, i.e., polymer-ceramic(PC) and poly(1-trimethylsilyl-1-propyne) [poly(TMSP)]. The static calibrations showed that PtTFPP/poly(TMSP) had a higher pressure sensitivity and a lower temperature dependency compared to PtTFPP/PC in this pressure range. The pressure distributions of a single and two interacting plumes impinging onto a flat plate model were measured using PSP technique. The experimental data were compared to numerical solutions that combined both the computed fluid dynamics(CFD) and direct simulation Monte Carlo(DSMC) methods. Remarkable agreements were achieved, demonstrating the feasibility and accuracy of the numerical approach.Finally, the aerodynamic force effect of interacting plumes at different separation distances was investigated numerically.
