The potential energy surface of O（^1D）＋C2H5Cl reaction was studied using QCISD（T）/6- 311＋＋G（d,p）//MP2/6-31G（d,p） method. The calculations reveal an insertion-elimination mechanism. The insertion reaction o...The potential energy surface of O（^1D）＋C2H5Cl reaction was studied using QCISD（T）/6- 311＋＋G（d,p）//MP2/6-31G（d,p） method. The calculations reveal an insertion-elimination mechanism. The insertion reaction of O（^1D） and C2H5Cl produces two energy-rich intermediates, IM1 and IM2, which subsequently decompose into various products. The calculations of the branching ratios of various products formed through the two intermediates were carried out using RRKM （Rice-Ramsperger-Kassel-Marcus） theory at the collision energies of 0, 20.9, 41.8, 62.7, 83.6, 104.5, and 125.4 kJ/mol. HCl is the main decomposition product for IM1; CH2OH is the main decomposition product for IM2. Since IM1 is more stable than IM2, HCl is probably the main product of the O（^1D）＋C2H5Cl reaction.展开更多
The hydrogenation of CO_(2) into methanol has attracted much attention and In_(2)O_(3) is a promising catalyst.Introducing metal elements into In_(2)O_(3)(M/In_(2)O_(3))is one of the main strategies to improve its per...The hydrogenation of CO_(2) into methanol has attracted much attention and In_(2)O_(3) is a promising catalyst.Introducing metal elements into In_(2)O_(3)(M/In_(2)O_(3))is one of the main strategies to improve its performance.However,its mechanism and active sites remain unclear and need to be further elucidated.Here,the noble‐metal‐free In_(x)‐Co_(y) oxides catalysts were prepared.Much‐improved performance and obvious product selectivity shift were observed.The optimized catalyst(In_(1)‐Co_(4))(9.7 mmol g_(cat)^(–1) h^(–1))showed five times methanol yields than pure In_(2)O_(3)(2.2 mmol g_(cat)^(–1) h^(–1))(P=4.0 MPa,T=300°C,GHSV=24000 cm^(3)_(STP) g_(cat)^(–1) h^(–1),H_(2):CO_(2)=3).And the cobalt‐catalyzed CO_(2) methanation activity was suppressed,although cobalt was most of the metal element.To unravel this selectivity shift,detailed catalysts performance evaluation,together with several in‐situ and ex‐situ characterizations,were employed on cobalt and In‐Co for comparative study.The results indicated CO_(2) hydrogenation on cobalt and In‐Co catalyst both followed the formate pathway,and In‐Co reconstructed and generated a surface In_(2)O_(3)‐enriched core‐shell‐like structure under a reductive atmosphere.The enriched In_(2)O_(3) at the surface significantly enhanced CO_(2) adsorption capacity and well stabilized the intermediates of CO_(2) hydrogenation.CO_(2) and carbon‐containing intermediates adsorbed much stronger on In‐Co than cobalt led to a feasible surface C/H ratio,thus allowing the*CH_(3)O to desorb to produce CH_(3)OH instead of being over‐hydrogenated to CH_(4).展开更多
Although pre-Northridge earthquake steel moment resisting frame buildings have been shown to be susceptible to brittle connection failures,they still represent a large fraction of the existing steel buildings in the U...Although pre-Northridge earthquake steel moment resisting frame buildings have been shown to be susceptible to brittle connection failures,they still represent a large fraction of the existing steel buildings in the United States of America.In this study,the performance of the 3-and 9-story Los Angeles pre-Northridge SAC buildings are analyzed considering ductile and brittle beam-column connection failures,and their uncertainty.This paper contributes to understanding the influence of uncertainty associated with connections brittle fracture on building interstory deformation capacity and its impact on bias and variability of fragility functions and loss assessment.The results show that considering brittle connections leads to significantly l arger d rift demands a nd t o h igher r epair costs,particularly under intense ground shaking.New fragility curve parameters are derived that account for the effect of the uncertainty of the strength and deformation capacity of brittle connections.展开更多
The effect of two different curing regimes on the polymerization degree of C-S-H in hardened cement pastes within 28 d were investigated by measuring the chemical environments of 29Si with magic angle spinning （MAS）...The effect of two different curing regimes on the polymerization degree of C-S-H in hardened cement pastes within 28 d were investigated by measuring the chemical environments of 29Si with magic angle spinning （MAS） nuclear magnetic resonance （NMR） and by analyzing the 29Si NMR spectra with deconvolution technique. The experimental results indicate that, at curing regime of constant temperature of 20℃, the polymerization of C-S-H increases and then decreases with curing age, and the A1/Si ratio increases gradually with curing age, furthermore, the two non-bridging oxygen bonds of bridging silicate tetrahedra in C-S-H structure mainly bond to H＋. At curing regime of variable temperature, the polymerization of C-S-H firstly increases then changes slightly and subsequently decreases with the temperature from low to high and then to low, and the A1/Si ratio firstly increases then keeps invariant and subsequently slightly decreases. Moreover, the temperature decreasing is advantageous for the Ca2＋ to be bonded to the bridging silicate tetrahedra and entering into the interlayer of C-S-H structure. The polymerization of C-S-H at curing regime of variable temperature is higher than that cured at constant temperature, but the curing regime of constant temperature is more beneficial to the substitution of AP for Si4＋ than that of variable temperature.展开更多
基金ACKNOWLEDGMENT This work was supported Science Foundation of China by the National Natural （No.50772107）.
文摘The potential energy surface of O（^1D）＋C2H5Cl reaction was studied using QCISD（T）/6- 311＋＋G（d,p）//MP2/6-31G（d,p） method. The calculations reveal an insertion-elimination mechanism. The insertion reaction of O（^1D） and C2H5Cl produces two energy-rich intermediates, IM1 and IM2, which subsequently decompose into various products. The calculations of the branching ratios of various products formed through the two intermediates were carried out using RRKM （Rice-Ramsperger-Kassel-Marcus） theory at the collision energies of 0, 20.9, 41.8, 62.7, 83.6, 104.5, and 125.4 kJ/mol. HCl is the main decomposition product for IM1; CH2OH is the main decomposition product for IM2. Since IM1 is more stable than IM2, HCl is probably the main product of the O（^1D）＋C2H5Cl reaction.
文摘The hydrogenation of CO_(2) into methanol has attracted much attention and In_(2)O_(3) is a promising catalyst.Introducing metal elements into In_(2)O_(3)(M/In_(2)O_(3))is one of the main strategies to improve its performance.However,its mechanism and active sites remain unclear and need to be further elucidated.Here,the noble‐metal‐free In_(x)‐Co_(y) oxides catalysts were prepared.Much‐improved performance and obvious product selectivity shift were observed.The optimized catalyst(In_(1)‐Co_(4))(9.7 mmol g_(cat)^(–1) h^(–1))showed five times methanol yields than pure In_(2)O_(3)(2.2 mmol g_(cat)^(–1) h^(–1))(P=4.0 MPa,T=300°C,GHSV=24000 cm^(3)_(STP) g_(cat)^(–1) h^(–1),H_(2):CO_(2)=3).And the cobalt‐catalyzed CO_(2) methanation activity was suppressed,although cobalt was most of the metal element.To unravel this selectivity shift,detailed catalysts performance evaluation,together with several in‐situ and ex‐situ characterizations,were employed on cobalt and In‐Co for comparative study.The results indicated CO_(2) hydrogenation on cobalt and In‐Co catalyst both followed the formate pathway,and In‐Co reconstructed and generated a surface In_(2)O_(3)‐enriched core‐shell‐like structure under a reductive atmosphere.The enriched In_(2)O_(3) at the surface significantly enhanced CO_(2) adsorption capacity and well stabilized the intermediates of CO_(2) hydrogenation.CO_(2) and carbon‐containing intermediates adsorbed much stronger on In‐Co than cobalt led to a feasible surface C/H ratio,thus allowing the*CH_(3)O to desorb to produce CH_(3)OH instead of being over‐hydrogenated to CH_(4).
文摘Although pre-Northridge earthquake steel moment resisting frame buildings have been shown to be susceptible to brittle connection failures,they still represent a large fraction of the existing steel buildings in the United States of America.In this study,the performance of the 3-and 9-story Los Angeles pre-Northridge SAC buildings are analyzed considering ductile and brittle beam-column connection failures,and their uncertainty.This paper contributes to understanding the influence of uncertainty associated with connections brittle fracture on building interstory deformation capacity and its impact on bias and variability of fragility functions and loss assessment.The results show that considering brittle connections leads to significantly l arger d rift demands a nd t o h igher r epair costs,particularly under intense ground shaking.New fragility curve parameters are derived that account for the effect of the uncertainty of the strength and deformation capacity of brittle connections.
基金Funded by the Major State Basic Research Development Program of China(973Program)(No.2009CB623201)
文摘The effect of two different curing regimes on the polymerization degree of C-S-H in hardened cement pastes within 28 d were investigated by measuring the chemical environments of 29Si with magic angle spinning （MAS） nuclear magnetic resonance （NMR） and by analyzing the 29Si NMR spectra with deconvolution technique. The experimental results indicate that, at curing regime of constant temperature of 20℃, the polymerization of C-S-H increases and then decreases with curing age, and the A1/Si ratio increases gradually with curing age, furthermore, the two non-bridging oxygen bonds of bridging silicate tetrahedra in C-S-H structure mainly bond to H＋. At curing regime of variable temperature, the polymerization of C-S-H firstly increases then changes slightly and subsequently decreases with the temperature from low to high and then to low, and the A1/Si ratio firstly increases then keeps invariant and subsequently slightly decreases. Moreover, the temperature decreasing is advantageous for the Ca2＋ to be bonded to the bridging silicate tetrahedra and entering into the interlayer of C-S-H structure. The polymerization of C-S-H at curing regime of variable temperature is higher than that cured at constant temperature, but the curing regime of constant temperature is more beneficial to the substitution of AP for Si4＋ than that of variable temperature.
