Through introducing the analytical problem of the plate with convection into the solution of the transient heat conduction thermal stress field model of the elastic plate, the stress reduction factor is presented expl...Through introducing the analytical problem of the plate with convection into the solution of the transient heat conduction thermal stress field model of the elastic plate, the stress reduction factor is presented explicitly in its dimensionless form. A new stress reduction factor is introduced for the purpose of comparison. The proper- ties and appropriate conditions of the stress reduction factor, the first and second ther- mal shock resistance （TSR） parameters for the high and low Biot numbers, respectively, and the approximation formulas for the intermediate Blot number-interval are discussed. To investigate the TSR of ceramics more accurately, it is recommended to combine the heat transfer theory with the theory of thermoelasticity or fracture mechanics or use a numerical method. The critical rupture temperature difference and the critical rup- ture dimensionless time can be used to characterize the TSR of ceramics intuitively and legibly.展开更多
An experiment was conducted to assess the impact of fused calcia-stabilized zirconia micro-powder on the thermal shock behavior of magnesia–spinel refractories.The effects of calcia-stabilized zirconia on the microst...An experiment was conducted to assess the impact of fused calcia-stabilized zirconia micro-powder on the thermal shock behavior of magnesia–spinel refractories.The effects of calcia-stabilized zirconia on the microstructure evolution and properties of magnesia–spinel refractories were characterized by the high-temperature elastic modulus,thermal shock damage resistance parameters,retainment of elastic modulus after thermal shock,and scanning electron microscopy.The results indicated that the incorporation of calcia-stabilized zirconia improved the thermomechanical properties and thermal shock behavior of magnesia–spinel specimens.The hot modulus of rupture of magnesia–spinel specimens increased by 2.5-fold due to the incorporation of calcia-stabilized zirconia micro-powder.The presence of a martensitic phase transformation in partially unstable ZrO2 and thermal mismatches among various phases contributed to a controlled formation of microcracks.And the pinning effect caused by the calcia-stabilized zirconia particles surrounding the grain boundaries played a crucial role in preventing the propagation of microcracks.This phenomenon significantly bolstered the thermal shock stability of magnesia–spinel refractories,consequently prolonging their service life.展开更多
Stone structures with dry joints, that is, without mortar, have shown a surprising behavior when earthquakes occur. An example of this behavior is the perennially of the so-called Inca wall in Peru, which despite havi...Stone structures with dry joints, that is, without mortar, have shown a surprising behavior when earthquakes occur. An example of this behavior is the perennially of the so-called Inca wall in Peru, which despite having suffered several earthquakes over time has remained stable without collapsing. This article presents the research carried out on stone masonry wails with dry joint, without mortar, subject to a seismic action. In order to understand the behavior of the masonry without mortar, it designs a Grid mode/ of Finite Elements. From the results, it is concluded that these walls with a certain thickness have ductility that allows them to withstand high displacement and rotation values, thus accommodating the movement of the earth subject to an earthquake. The individual stone blocks move relative to each other through rotations and displacements, which are processed in the free joints of any mortar. The joints work as energy sinks. The free movements in the joints dissipate the energy transmitted by the earthquake, not causing in this way the rupture of the stone blocks. The goal of this article is to understand the p importance of lack of mortar in the seismic behavior of the mansonry.展开更多
In an effort to understand the recombination of a B2 metallo-β-lactamase（MβL）,the binding of metals to apo-ImiS was studied by isothermal titration calorimetry and fluorescence spectra.The binding of Zn（Ⅱ）,Co...In an effort to understand the recombination of a B2 metallo-β-lactamase（MβL）,the binding of metals to apo-ImiS was studied by isothermal titration calorimetry and fluorescence spectra.The binding of Zn（Ⅱ）,Co（Ⅱ） to apo-lmiS resulted in activation free energies △G_≠~θ values of 93.719 and 92.948 kJ mol^（-1）,respectively,and increasing of fluorescence intensity at maxima emission of 340 nm.展开更多
基金Project supported by the National Natural Science Foundation of China (Nos. 90916009 and11172336)
文摘Through introducing the analytical problem of the plate with convection into the solution of the transient heat conduction thermal stress field model of the elastic plate, the stress reduction factor is presented explicitly in its dimensionless form. A new stress reduction factor is introduced for the purpose of comparison. The proper- ties and appropriate conditions of the stress reduction factor, the first and second ther- mal shock resistance （TSR） parameters for the high and low Biot numbers, respectively, and the approximation formulas for the intermediate Blot number-interval are discussed. To investigate the TSR of ceramics more accurately, it is recommended to combine the heat transfer theory with the theory of thermoelasticity or fracture mechanics or use a numerical method. The critical rupture temperature difference and the critical rup- ture dimensionless time can be used to characterize the TSR of ceramics intuitively and legibly.
基金supported by the Key Project of the National Natural Science Foundation of China(Grant No.U21A2058)the Hebei Guoliang New Materials Co.,Ltd.(Grant No.22150239J).
文摘An experiment was conducted to assess the impact of fused calcia-stabilized zirconia micro-powder on the thermal shock behavior of magnesia–spinel refractories.The effects of calcia-stabilized zirconia on the microstructure evolution and properties of magnesia–spinel refractories were characterized by the high-temperature elastic modulus,thermal shock damage resistance parameters,retainment of elastic modulus after thermal shock,and scanning electron microscopy.The results indicated that the incorporation of calcia-stabilized zirconia improved the thermomechanical properties and thermal shock behavior of magnesia–spinel specimens.The hot modulus of rupture of magnesia–spinel specimens increased by 2.5-fold due to the incorporation of calcia-stabilized zirconia micro-powder.The presence of a martensitic phase transformation in partially unstable ZrO2 and thermal mismatches among various phases contributed to a controlled formation of microcracks.And the pinning effect caused by the calcia-stabilized zirconia particles surrounding the grain boundaries played a crucial role in preventing the propagation of microcracks.This phenomenon significantly bolstered the thermal shock stability of magnesia–spinel refractories,consequently prolonging their service life.
文摘Stone structures with dry joints, that is, without mortar, have shown a surprising behavior when earthquakes occur. An example of this behavior is the perennially of the so-called Inca wall in Peru, which despite having suffered several earthquakes over time has remained stable without collapsing. This article presents the research carried out on stone masonry wails with dry joint, without mortar, subject to a seismic action. In order to understand the behavior of the masonry without mortar, it designs a Grid mode/ of Finite Elements. From the results, it is concluded that these walls with a certain thickness have ductility that allows them to withstand high displacement and rotation values, thus accommodating the movement of the earth subject to an earthquake. The individual stone blocks move relative to each other through rotations and displacements, which are processed in the free joints of any mortar. The joints work as energy sinks. The free movements in the joints dissipate the energy transmitted by the earthquake, not causing in this way the rupture of the stone blocks. The goal of this article is to understand the p importance of lack of mortar in the seismic behavior of the mansonry.
基金supported by the National Natural Science Foundation of China (Nos.21272186 and 81361138018)
文摘In an effort to understand the recombination of a B2 metallo-β-lactamase（MβL）,the binding of metals to apo-ImiS was studied by isothermal titration calorimetry and fluorescence spectra.The binding of Zn（Ⅱ）,Co（Ⅱ） to apo-lmiS resulted in activation free energies △G_≠~θ values of 93.719 and 92.948 kJ mol^（-1）,respectively,and increasing of fluorescence intensity at maxima emission of 340 nm.
