To simulate the concrete shrinkage in varying temperature and moisture environments, a simulate procedure comprising an analytical process and a finite element analysis is proposed based on the coupled partial differe...To simulate the concrete shrinkage in varying temperature and moisture environments, a simulate procedure comprising an analytical process and a finite element analysis is proposed based on the coupled partial differential equations describing heat and moisture transfer in a porous medium. Using the Laplace transformation method and transfer function to simplify and solve the coupled equations in Laplace domain, the moisture and temperature distribution in time domain are obtained by inverse Laplace transformation. The shrinkage deformations of concrete are numerically simulated by the finite element method （FEM） based on the obtained temperature and moisture distribution. This approach avoids the complex eigenvalues, coupling difficulty and low accuracy found in other solving methods, and also effectively calculates the moisture induced shrinkage which is almost impossible using familiar FEM software. The validity of the simulation procedure is verified by Hundt＇s test data. The results reveal that the proposed approach can be considered a reliable and efficient method to simulate the coupling moisture and temperature shrinkage of concrete.展开更多
The gel filtration was carried out for purification of cellulase. The influences of chromatographic parameters on the resolution were studied to determine the optimal conditions for purification. The purified endogluc...The gel filtration was carried out for purification of cellulase. The influences of chromatographic parameters on the resolution were studied to determine the optimal conditions for purification. The purified endoglucanase was obtained by gel filtration by Superdex 75 prep grade with an activity recovery of 92.8% and the purification factor 4.2. The sample volume should be below 6% of the column bed volume and the column bed height L≥12.0 cm. The optimum catalysis temperature and pH for the enzyme were 55 ℃ and 4.5—5.0, respectively. The cellulase was stable at pH ranging from 4.0 to 6.0 and temperature below 60 ℃.展开更多
By using metal nitrates as starting materials and citric acid as a complexing agent, Y2Si207：Re3＋ （Re=Eu, Tb） phosphors were prepared by a sol-gel method. X-ray diffraction was employed to characterize the resulti...By using metal nitrates as starting materials and citric acid as a complexing agent, Y2Si207：Re3＋ （Re=Eu, Tb） phosphors were prepared by a sol-gel method. X-ray diffraction was employed to characterize the resulting samples. The results of XRD indicate that the α-Y2Si2O7 nanocrystal with size of 27 nm is obtained at 1000 ℃ and the doping ion content does not influence the structure. The excitation spectra in the UV and VUV ranges and the emission spectra of Re^3＋ doped samples were measured. The excitation spectra in the VUV range is due to absorption of host, that in the UV range is ascribed to absorption transitions from 4f to 5d state of the Tb^3＋ and the charge transfer in the En^3＋-O^2- bond. The spectral energy distribution of the Tb^3＋ emission depends strongly on the Tb3＋ concentration. The dependence of photolumineseenee intensity on Re^3＋ concentration is also discussed in detail. The fluorescent decay curves at room temperature were measured and analyzed.展开更多
The present study is an investigation of the properties of poly(vinyl alcohol),which would be a better contact lens mate- rial than conventional HEMA in some ways.A transparent PVA hydrogel was prepared from a PVA sol...The present study is an investigation of the properties of poly(vinyl alcohol),which would be a better contact lens mate- rial than conventional HEMA in some ways.A transparent PVA hydrogel was prepared from a PVA solution in a mixed solvent consisting of water and a water-miscible organic solvent,DMSO,by the freezing-thawing method.The water content,visible light transmittance,mechanical and swelling properties of the hydrogels were evaluated as a function of PVA concentration and number of freeze-thaw cycles.The results show that the properties of PVA hydrogels depend on the polymer concentration,the number of freeze-thaw cycles and the addition of the organic solvent.展开更多
With the increasing development of Brazil in recent years, major engineering construction works have been designed and built, partieutarly those involving large volumes of mass concrete, such as in the case of dams. M...With the increasing development of Brazil in recent years, major engineering construction works have been designed and built, partieutarly those involving large volumes of mass concrete, such as in the case of dams. Mass concrete, due to its large size and volume, presents a considerable temperature rise caused by cement grain hydration. This temperature rise can be sufficient to cause concrete crack and/or cracking, which may lead to serious problems. In this paper, we sought to study heat generation and temperature field in mass concrete through ANSYS software, which uses finite element method to analyze the problem. This program allows temperatures to be checked for different concrete ages. With that, it is possible to evaluate the temperatures obtained and the factors influencing the results in a short period of time at a low cost. With the help of the software, it is possible to check the temperatures for different concrete properties by analyzing them on different concreting days. Therefore, it was possible to establish that the properties of the concrete directly influence the temperature evolution phenomenon.展开更多
We focused in this study on two verbs of motion ba （come） and hevi （bring） used in contemporary Hebrew pointing to a number of semantic shifts occurring in each of them and to categorical shifts that occurred in t...We focused in this study on two verbs of motion ba （come） and hevi （bring） used in contemporary Hebrew pointing to a number of semantic shifts occurring in each of them and to categorical shifts that occurred in the verb ha. We conducted a semantic and syntactic analysis of these shifts in which we observed： a change in the syntactic valuation of ba and hevi, the semantic characteristic of the nominal collocations which form their syntactic setting, and the semantic connection between their original and new meanings. The article starts out with a presentation of the original meanings of the two verbs as belonging to the family of concrete verbs of motion. It then presents the semantic shifts each undergoing from designating motion to designating giving, existing, and modality （capability, intent and aspect） and concludes with the categorical shift of the verb ba to impersonal （ロ＂λ∏） and to discourse marker. It is noteworthy that in each of the shifts observed we noticed relation between the meaning stemming from the shift and the original meaning of ba and hevi as verbs of motion. We were able to prove that the original meaning is still echoed both in the semantic and category categorical shifts.展开更多
Li2Fe0.5Mn0.5SiO4 material was synthesized by a citric acid-assisted sol-gel method. The influence of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+) on the electrochemical properties of Li2Fe0.5Mn0.5...Li2Fe0.5Mn0.5SiO4 material was synthesized by a citric acid-assisted sol-gel method. The influence of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+) on the electrochemical properties of Li2Fe0.5Mn0.5SiO4 was studied. The final sample was identified as Li2Fe0.5Mn0.5SiO4 with a Pmn21 monoclinic structure by X-ray diffraction analysis. The crystal phases components and crystal phase structure of the Li2Fe0.5Mn0.4SiO4 material were improved as the increase of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+). Field-emission scanning electron microscopy verified that the Li2Fe0.5Mn0.5SiO4 particles are agglomerates of Li2Fe0.5Mn0.5SiO4 primary particles with a geometric mean diameter of 220 nm. The Li2Fe0.5Mn0.5SiO4 sample was used as an electrode material for rechargeable lithium ion batteries, and the electrochemical measurements were carried out at room temperature. The Li2Fe0.5Mn0.5SiO4 electrode delivered a first discharge capacity of 230.1 mAh/g at the current density of 10 mA/g in first cycle and about 162 mAh/g after 20 cycles at the current density of 20 mA/g.展开更多
基金The National Natural Science Foundation of China(No50539040)the Trans-Century Training Programme Foundation forthe Talents by the State Education Commission (NoNCET-05-0473)
文摘To simulate the concrete shrinkage in varying temperature and moisture environments, a simulate procedure comprising an analytical process and a finite element analysis is proposed based on the coupled partial differential equations describing heat and moisture transfer in a porous medium. Using the Laplace transformation method and transfer function to simplify and solve the coupled equations in Laplace domain, the moisture and temperature distribution in time domain are obtained by inverse Laplace transformation. The shrinkage deformations of concrete are numerically simulated by the finite element method （FEM） based on the obtained temperature and moisture distribution. This approach avoids the complex eigenvalues, coupling difficulty and low accuracy found in other solving methods, and also effectively calculates the moisture induced shrinkage which is almost impossible using familiar FEM software. The validity of the simulation procedure is verified by Hundt＇s test data. The results reveal that the proposed approach can be considered a reliable and efficient method to simulate the coupling moisture and temperature shrinkage of concrete.
基金Supported by the National Natural Science Foundation of China (No. 29736180).
文摘The gel filtration was carried out for purification of cellulase. The influences of chromatographic parameters on the resolution were studied to determine the optimal conditions for purification. The purified endoglucanase was obtained by gel filtration by Superdex 75 prep grade with an activity recovery of 92.8% and the purification factor 4.2. The sample volume should be below 6% of the column bed volume and the column bed height L≥12.0 cm. The optimum catalysis temperature and pH for the enzyme were 55 ℃ and 4.5—5.0, respectively. The cellulase was stable at pH ranging from 4.0 to 6.0 and temperature below 60 ℃.
文摘By using metal nitrates as starting materials and citric acid as a complexing agent, Y2Si207：Re3＋ （Re=Eu, Tb） phosphors were prepared by a sol-gel method. X-ray diffraction was employed to characterize the resulting samples. The results of XRD indicate that the α-Y2Si2O7 nanocrystal with size of 27 nm is obtained at 1000 ℃ and the doping ion content does not influence the structure. The excitation spectra in the UV and VUV ranges and the emission spectra of Re^3＋ doped samples were measured. The excitation spectra in the VUV range is due to absorption of host, that in the UV range is ascribed to absorption transitions from 4f to 5d state of the Tb^3＋ and the charge transfer in the En^3＋-O^2- bond. The spectral energy distribution of the Tb^3＋ emission depends strongly on the Tb3＋ concentration. The dependence of photolumineseenee intensity on Re^3＋ concentration is also discussed in detail. The fluorescent decay curves at room temperature were measured and analyzed.
基金Projects 50575106 supported by the National Natural Science Foundation of ChinaBG2007046 by the High Technology Project of Jiangsu Province
文摘The present study is an investigation of the properties of poly(vinyl alcohol),which would be a better contact lens mate- rial than conventional HEMA in some ways.A transparent PVA hydrogel was prepared from a PVA solution in a mixed solvent consisting of water and a water-miscible organic solvent,DMSO,by the freezing-thawing method.The water content,visible light transmittance,mechanical and swelling properties of the hydrogels were evaluated as a function of PVA concentration and number of freeze-thaw cycles.The results show that the properties of PVA hydrogels depend on the polymer concentration,the number of freeze-thaw cycles and the addition of the organic solvent.
文摘With the increasing development of Brazil in recent years, major engineering construction works have been designed and built, partieutarly those involving large volumes of mass concrete, such as in the case of dams. Mass concrete, due to its large size and volume, presents a considerable temperature rise caused by cement grain hydration. This temperature rise can be sufficient to cause concrete crack and/or cracking, which may lead to serious problems. In this paper, we sought to study heat generation and temperature field in mass concrete through ANSYS software, which uses finite element method to analyze the problem. This program allows temperatures to be checked for different concrete ages. With that, it is possible to evaluate the temperatures obtained and the factors influencing the results in a short period of time at a low cost. With the help of the software, it is possible to check the temperatures for different concrete properties by analyzing them on different concreting days. Therefore, it was possible to establish that the properties of the concrete directly influence the temperature evolution phenomenon.
文摘We focused in this study on two verbs of motion ba （come） and hevi （bring） used in contemporary Hebrew pointing to a number of semantic shifts occurring in each of them and to categorical shifts that occurred in the verb ha. We conducted a semantic and syntactic analysis of these shifts in which we observed： a change in the syntactic valuation of ba and hevi, the semantic characteristic of the nominal collocations which form their syntactic setting, and the semantic connection between their original and new meanings. The article starts out with a presentation of the original meanings of the two verbs as belonging to the family of concrete verbs of motion. It then presents the semantic shifts each undergoing from designating motion to designating giving, existing, and modality （capability, intent and aspect） and concludes with the categorical shift of the verb ba to impersonal （ロ＂λ∏） and to discourse marker. It is noteworthy that in each of the shifts observed we noticed relation between the meaning stemming from the shift and the original meaning of ba and hevi as verbs of motion. We were able to prove that the original meaning is still echoed both in the semantic and category categorical shifts.
基金Projects(13A047,10B054)supported by the Scientific Research Fund of Hunan Provincial Education Department,ChinaProjects(2011GK2002,2011FJ3160)supported by the Planned Science and Technology Project of Hunan Province,China
文摘Li2Fe0.5Mn0.5SiO4 material was synthesized by a citric acid-assisted sol-gel method. The influence of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+) on the electrochemical properties of Li2Fe0.5Mn0.5SiO4 was studied. The final sample was identified as Li2Fe0.5Mn0.5SiO4 with a Pmn21 monoclinic structure by X-ray diffraction analysis. The crystal phases components and crystal phase structure of the Li2Fe0.5Mn0.4SiO4 material were improved as the increase of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+). Field-emission scanning electron microscopy verified that the Li2Fe0.5Mn0.5SiO4 particles are agglomerates of Li2Fe0.5Mn0.5SiO4 primary particles with a geometric mean diameter of 220 nm. The Li2Fe0.5Mn0.5SiO4 sample was used as an electrode material for rechargeable lithium ion batteries, and the electrochemical measurements were carried out at room temperature. The Li2Fe0.5Mn0.5SiO4 electrode delivered a first discharge capacity of 230.1 mAh/g at the current density of 10 mA/g in first cycle and about 162 mAh/g after 20 cycles at the current density of 20 mA/g.
