Casting titanium alloy TC4(ZTC4) after hot isostatic pressing(HIP) is one of the preferred materials in the field of aerospace manufacturing. In this paper, HIPZTC4 after a long-term thermal exposure was investigated....Casting titanium alloy TC4(ZTC4) after hot isostatic pressing(HIP) is one of the preferred materials in the field of aerospace manufacturing. In this paper, HIPZTC4 after a long-term thermal exposure was investigated.In order to evaluate the variation of mechanical properties with service time, the tensile properties of this alloy after exposure at 400 °C for 100, 500, and 1,000 h were investigated. Microstructure of samples was observed by the means of optical microscopy(OM), scanning electron microscopy(SEM), and transmission electron microscopy(TEM). Tensile test was carried out under different test temperatures and fracture appearance was studied. The results show that the strength increases with exposure time due to the harder a2(Ti3Al) phase precipitated in the a phase and superficial oxygen layer formed, which results in the fact that the resistance of crack propagation could be increased and cracks first initiate between surface oxidation and the matrix. Besides, the tensile temperature also has a significant effect on the mechanical properties of HIPZTC4. The yield strength and tensile strength decrease with the increase of tensile temperature, while the total elongation increases.展开更多
A new ferritic creep resistant steel has been developed by eliminating Nb and adding 1.5 mass % Re to a ferritic steel grade T/P23 with the aim of enhancing its mechanical properties at high temperature.Cast ingots of...A new ferritic creep resistant steel has been developed by eliminating Nb and adding 1.5 mass % Re to a ferritic steel grade T/P23 with the aim of enhancing its mechanical properties at high temperature.Cast ingots of both steels, new grade and ASTM T/P 23, were hot rolled at 900℃ and then submitted to a thermal treatment consisting of solubilization at 1050℃ and tempering at 700℃. Tempered bainitic microstructures obtained contain second phases reinforcing carbide particles, mainly M_6C and M_（23）C_6 at the boundaries of both, prior austenite grains and bainitic ferrite laths, as well as MC within the grains. Mechanical properties at temperatures ranging from 540 to 600℃ were studied by strain-ratechange tests in compression at strain rates between 10^（-7） and 10^（-4）s^（-1）. These tests showed high stress exponents（n ≥ 20） and activation energies（Q ≈ 400 k J/mol） for both alloys, which were associated with a dislocation movement mechanism with a strong interaction between dislocations and precipitates. On the other hand, a creep exponent of 5 was derived for the stress dependence of minimum creep rate from conventional-type creep tests at 600℃. Although this stress exponent is usually related to a dislocation climb controlled creep mechanism, remarkable microstructural degradation observed with increasing creep time makes difficult to elucidate the true deformation mechanism controlling creep.展开更多
To understand the earthquake characteristics in Xinfengjiang (XFJ for short) reservoir area, we collected the small earthquakes occurred in the area from 1961 to 1999. We segmented this 40-year period, parted the rese...To understand the earthquake characteristics in Xinfengjiang (XFJ for short) reservoir area, we collected the small earthquakes occurred in the area from 1961 to 1999. We segmented this 40-year period, parted the research region and calculated the composite fault plane solution of each block, disscussed the effect characteristics of stress field of water pressure using Mohrs stress circle. The final result shows that the main rupture pattern was very different before and after the M = 6.1 main shock, changing from strike slip to normal rupture. The maximum principal stress axes of composite fault plane solutions are characterized by synchronous change with water level.展开更多
To develop a unitary quantum theory with probabilistic description for pseudo-Hermitian systems one needs to consider the theories in a different Hilbert space endowed with a positive definite metric operator. There a...To develop a unitary quantum theory with probabilistic description for pseudo-Hermitian systems one needs to consider the theories in a different Hilbert space endowed with a positive definite metric operator. There are different approaches to find such metric operators. We compare the different approaches of calculating positive definite metric operators in pseudo-Hermitian theories with the help of several explicit examples in non-relativistic as well as in relativistic situations. Exceptional points and spontaneous symmetry breaking are also discussed in these models.展开更多
The properties and collecting ability of a new collector,monoalkyl ester phosphoric acid(P538),for the flotation of rare earth minerals are described in the paper.The mechanism of P538 adsorption on the surfaces of mo...The properties and collecting ability of a new collector,monoalkyl ester phosphoric acid(P538),for the flotation of rare earth minerals are described in the paper.The mechanism of P538 adsorption on the surfaces of monazite or bastnaesite is explored by modern measuring techniques,such as IR and ESCA,etc.展开更多
The tumour suppressor p53 is a transcription factor that regulates multiple biological functions including metabolism, DNA repair, cell cycle arrest, apoptosis and senescence. About half of human cancers show a normal...The tumour suppressor p53 is a transcription factor that regulates multiple biological functions including metabolism, DNA repair, cell cycle arrest, apoptosis and senescence. About half of human cancers show a normal TP53 gene and aberrant overexpression of Mdm2. This fact promotes a promising cancer therapeutic strategy by inhibiting the interactions between p53 and Mdm2. Various inhibitors have been designed to achieve this novel approach for cancer therapy. However, the detailed competition mechanism between these inhibitors and the p53 molecule in their binding process to Mdm2 is still unclear. We investigate this competition mechanism between Nutlin3 and p53 using molecular dynamics simulations. It is found that Nutlin3 binds faster than the p53 molecule to Mdm2 to prevent p53 binding to Mdm2 when Nutlin3 and p53 have equal distance from Mdm2. Nutlin3 can also bind to the p53-Mdm2 complex to disturb and weaken the interactions between p53 and Mdm2. Consequently, p53 cannot bind to Mdm2 and its tumour suppression function is reactivated. These results provide the detailed competition mechanism between Nutlin3 and p53 in their binding to Mdm2. Because the binding site of most other inhibitors to Mdm2 is the same as Nutlin3, therefore this competition mechanism can extend to most inhibitors which target the p53-Mdm2 interaction.展开更多
The intrinsic conduction mechanism and optimal sintering atmosphere of(Ba_(0.85)Ca_(0.15))(Zr_(0.1)Ti_(0.9))O_(3)(BCZT)ceramics were regulated by Mn-doping element in this work.By Hall and impedance analysis,the undop...The intrinsic conduction mechanism and optimal sintering atmosphere of(Ba_(0.85)Ca_(0.15))(Zr_(0.1)Ti_(0.9))O_(3)(BCZT)ceramics were regulated by Mn-doping element in this work.By Hall and impedance analysis,the undoped BCZT ceramics exhibit a typical n-type conduction mechanism,and the electron concentration decreases with the increasing oxygen partial pressure.Therefore,the undoped ceramics exhibit best electrical properties(piezoelectrical constant<733=585 pC·N^(-1),electro-mechanical coupling factor k_(p)=56%)in O_(2).A handful of Mn-doping element would transfer the conduction mechanism from n-type into p-type.And the hole concentration reduces with the decreasing oxygen partial pressure for Mn-doped BCZT ceramics.Therefore,the Mn-doped ceramics sintered in N_(2)have the highest insulation resistance and best piezoelectric properties(d_(33)=505 pC·N^(-1),k_(p)=50%).The experimental results demonstrate that the Mn-doping element can effectively adjust the intrinsic conduction mechanism and then predict the optimal atmosphere.展开更多
Objective To study the role and mechanism of sphingosine-phosphate(S1P)/sphingosine-1-phosphate receptor 1(S1P1)signal pathway during post conditioning of hypertrophic cardiomyocytes.Methods Neonatal rat cardiomyocyte...Objective To study the role and mechanism of sphingosine-phosphate(S1P)/sphingosine-1-phosphate receptor 1(S1P1)signal pathway during post conditioning of hypertrophic cardiomyocytes.Methods Neonatal rat cardiomyocytes were isolated and cultured,then stimulated by norepinephrine(NE)to induce cardiomyocytes hypertrophy.Using tri-gas incubator to create展开更多
基金financially supported by the National Natural Science Foundation of China(No.50804005)
文摘Casting titanium alloy TC4(ZTC4) after hot isostatic pressing(HIP) is one of the preferred materials in the field of aerospace manufacturing. In this paper, HIPZTC4 after a long-term thermal exposure was investigated.In order to evaluate the variation of mechanical properties with service time, the tensile properties of this alloy after exposure at 400 °C for 100, 500, and 1,000 h were investigated. Microstructure of samples was observed by the means of optical microscopy(OM), scanning electron microscopy(SEM), and transmission electron microscopy(TEM). Tensile test was carried out under different test temperatures and fracture appearance was studied. The results show that the strength increases with exposure time due to the harder a2(Ti3Al) phase precipitated in the a phase and superficial oxygen layer formed, which results in the fact that the resistance of crack propagation could be increased and cracks first initiate between surface oxidation and the matrix. Besides, the tensile temperature also has a significant effect on the mechanical properties of HIPZTC4. The yield strength and tensile strength decrease with the increase of tensile temperature, while the total elongation increases.
基金supported by the Spanish Ministry of Economy and Competitiveness(MINECO)under Grant MAT2012-39124,MAT2015-68919,and MAT2016-80875
文摘A new ferritic creep resistant steel has been developed by eliminating Nb and adding 1.5 mass % Re to a ferritic steel grade T/P23 with the aim of enhancing its mechanical properties at high temperature.Cast ingots of both steels, new grade and ASTM T/P 23, were hot rolled at 900℃ and then submitted to a thermal treatment consisting of solubilization at 1050℃ and tempering at 700℃. Tempered bainitic microstructures obtained contain second phases reinforcing carbide particles, mainly M_6C and M_（23）C_6 at the boundaries of both, prior austenite grains and bainitic ferrite laths, as well as MC within the grains. Mechanical properties at temperatures ranging from 540 to 600℃ were studied by strain-ratechange tests in compression at strain rates between 10^（-7） and 10^（-4）s^（-1）. These tests showed high stress exponents（n ≥ 20） and activation energies（Q ≈ 400 k J/mol） for both alloys, which were associated with a dislocation movement mechanism with a strong interaction between dislocations and precipitates. On the other hand, a creep exponent of 5 was derived for the stress dependence of minimum creep rate from conventional-type creep tests at 600℃. Although this stress exponent is usually related to a dislocation climb controlled creep mechanism, remarkable microstructural degradation observed with increasing creep time makes difficult to elucidate the true deformation mechanism controlling creep.
文摘To understand the earthquake characteristics in Xinfengjiang (XFJ for short) reservoir area, we collected the small earthquakes occurred in the area from 1961 to 1999. We segmented this 40-year period, parted the research region and calculated the composite fault plane solution of each block, disscussed the effect characteristics of stress field of water pressure using Mohrs stress circle. The final result shows that the main rupture pattern was very different before and after the M = 6.1 main shock, changing from strike slip to normal rupture. The maximum principal stress axes of composite fault plane solutions are characterized by synchronous change with water level.
文摘To develop a unitary quantum theory with probabilistic description for pseudo-Hermitian systems one needs to consider the theories in a different Hilbert space endowed with a positive definite metric operator. There are different approaches to find such metric operators. We compare the different approaches of calculating positive definite metric operators in pseudo-Hermitian theories with the help of several explicit examples in non-relativistic as well as in relativistic situations. Exceptional points and spontaneous symmetry breaking are also discussed in these models.
文摘The properties and collecting ability of a new collector,monoalkyl ester phosphoric acid(P538),for the flotation of rare earth minerals are described in the paper.The mechanism of P538 adsorption on the surfaces of monazite or bastnaesite is explored by modern measuring techniques,such as IR and ESCA,etc.
基金Supported by the National Natural Science Foundation of China under Grant No 11675018the Beijing Natural Science Foundation under Grant No 1172008the Fundamental Research Funds for the Central Universities under Grant No 2015KJJCB01
文摘The tumour suppressor p53 is a transcription factor that regulates multiple biological functions including metabolism, DNA repair, cell cycle arrest, apoptosis and senescence. About half of human cancers show a normal TP53 gene and aberrant overexpression of Mdm2. This fact promotes a promising cancer therapeutic strategy by inhibiting the interactions between p53 and Mdm2. Various inhibitors have been designed to achieve this novel approach for cancer therapy. However, the detailed competition mechanism between these inhibitors and the p53 molecule in their binding process to Mdm2 is still unclear. We investigate this competition mechanism between Nutlin3 and p53 using molecular dynamics simulations. It is found that Nutlin3 binds faster than the p53 molecule to Mdm2 to prevent p53 binding to Mdm2 when Nutlin3 and p53 have equal distance from Mdm2. Nutlin3 can also bind to the p53-Mdm2 complex to disturb and weaken the interactions between p53 and Mdm2. Consequently, p53 cannot bind to Mdm2 and its tumour suppression function is reactivated. These results provide the detailed competition mechanism between Nutlin3 and p53 in their binding to Mdm2. Because the binding site of most other inhibitors to Mdm2 is the same as Nutlin3, therefore this competition mechanism can extend to most inhibitors which target the p53-Mdm2 interaction.
基金supported by the National Natural Science Foundation of China(Grant Nos.52072150 and 51972146)the Young Elite Scientists Sponsorship Program by CAST,the State Key Laboratory of New Ceramics and Fine Processing Tsinghua University(Grant No.KF202002)the Open Foundation of Guangdong Provincial Key Laboratory of Electronic Functional Materials and Devices(Grant No.EFMD2021002Z).
文摘The intrinsic conduction mechanism and optimal sintering atmosphere of(Ba_(0.85)Ca_(0.15))(Zr_(0.1)Ti_(0.9))O_(3)(BCZT)ceramics were regulated by Mn-doping element in this work.By Hall and impedance analysis,the undoped BCZT ceramics exhibit a typical n-type conduction mechanism,and the electron concentration decreases with the increasing oxygen partial pressure.Therefore,the undoped ceramics exhibit best electrical properties(piezoelectrical constant<733=585 pC·N^(-1),electro-mechanical coupling factor k_(p)=56%)in O_(2).A handful of Mn-doping element would transfer the conduction mechanism from n-type into p-type.And the hole concentration reduces with the decreasing oxygen partial pressure for Mn-doped BCZT ceramics.Therefore,the Mn-doped ceramics sintered in N_(2)have the highest insulation resistance and best piezoelectric properties(d_(33)=505 pC·N^(-1),k_(p)=50%).The experimental results demonstrate that the Mn-doping element can effectively adjust the intrinsic conduction mechanism and then predict the optimal atmosphere.
文摘Objective To study the role and mechanism of sphingosine-phosphate(S1P)/sphingosine-1-phosphate receptor 1(S1P1)signal pathway during post conditioning of hypertrophic cardiomyocytes.Methods Neonatal rat cardiomyocytes were isolated and cultured,then stimulated by norepinephrine(NE)to induce cardiomyocytes hypertrophy.Using tri-gas incubator to create
