采用优化的RDG (Rappaz-Drezet-Gremaud)热裂模型预测了Mg-5Zn-x Er (x=0.83、1.25、2.5、5,质量分数,%)三元多相合金的铸造热裂敏感性,并利用"约束杆"钢模铸造(CRC)实验评价了该合金的热裂敏感性。结果表明,优化的RDG热裂模...采用优化的RDG (Rappaz-Drezet-Gremaud)热裂模型预测了Mg-5Zn-x Er (x=0.83、1.25、2.5、5,质量分数,%)三元多相合金的铸造热裂敏感性,并利用"约束杆"钢模铸造(CRC)实验评价了该合金的热裂敏感性。结果表明,优化的RDG热裂模型可准确地预测Mg-5Zn-x Er镁合金的热裂敏感性:随着Er含量的增加,合金的热裂敏感性呈先增加后降低的趋势,当Er含量为2.5%时合金的热裂敏感性最高,当Er含量为5.0%时合金的热裂敏感性最低,与实验结果相一致。对铸件凝固曲线、相组成、微观组织等进一步分析表明,当Er含量提高至2.5%时,合金凝固过程发生包晶反应生成I相的同时消耗了液相,并且扩大了合金的凝固温度区间,使合金的热裂敏感性上升;Er含量继续提高至5.0%时,合金在凝固过程中发生L→α-Mg+W的共晶反应,凝固温度区间减小,有利于凝固后期枝晶间裂纹的补缩,显著降低了合金的热裂敏感性。展开更多
The hot cracking tendency of 7075 semi-solid alloy under different conditions was studied by critical diameter method.The experiment and simulation results show that the dendrite arms of the rod grow from the edge to ...The hot cracking tendency of 7075 semi-solid alloy under different conditions was studied by critical diameter method.The experiment and simulation results show that the dendrite arms of the rod grow from the edge to the center.The smaller the diameter of the rod is,the more obvious the directional growth of dendrite is,and the greater the tendency of hot cracking is.Compared with ordinary melt,for semi-solid slurry,increasing mould temperature or decreasing pouring temperature can significantly decrease hot cracking tendency of 7075 alloy,decreasing hot cracking grade from 256 to 100 mm^2.Furthermore,based on the RDG criterion,the effects of solidification conditions on the hot cracking tendency were discussed combined with simulation.At the same time,the application and development of RDG criterion were also researched.展开更多
Anion can be identified by pyromellitic imide-azacyclophane which is one of the host compounds.This article investigated the interaction between the host and organic pollution compounds.The host and other eight compou...Anion can be identified by pyromellitic imide-azacyclophane which is one of the host compounds.This article investigated the interaction between the host and organic pollution compounds.The host and other eight compounds were optimized by DFT（density functional theory） B3LYP/6-31G level and the energy of compounds was corrected using Boys-Bemardi method.On the basis of B3LYP/6-31G optimized geometries,the RDG function and sign（λ2（r））ρ（r） function values of space points were calculated,and color RDG isosurface map was drawn.3He chemical shift was calculated by the B3LYP/6-31G method.The results showed that the eight organic pollution molecules with the host one shaped stable configurations by hydrogen bonds,respectively.The stabilization energy of complexes 4 and 7 showed repulsion（steric effects） of cyclophane cage observably affecting the stability of the complexes.The location,intensity and the type of interaction in complex 1 were analyzed through color-filled RDG isosurface map.Aromaticity calculations showed that the weak interaction reduced the transverse induction ring current in the host rings,and deteriorated the aromaticity of compounds.展开更多
Intermolecular interactions between PH2Cl and Ar–R（R = H,OH,NH2,CH3,Br,Cl,F,CN,NO2） were calculated by using MP2/aug-cc-p VDZ quantum chemical method.It has been shown from our calculations that the aromatic rings ...Intermolecular interactions between PH2Cl and Ar–R（R = H,OH,NH2,CH3,Br,Cl,F,CN,NO2） were calculated by using MP2/aug-cc-p VDZ quantum chemical method.It has been shown from our calculations that the aromatic rings with electron-withdrawing groups represent much weaker binding affinities than those with electron-donating groups.The charge-transfer interaction between PH2Cl and Ar–R plays an important role in the formation of pnicogen bond complexes,as revealed by NBO analysis.Nevertheless,AIM analysis shows that the nature of the interactions between PH2Cl and Ar–R is electrostatic,and the interaction energies of the complexes are correlated positively with the electron densities in the bond critical points（BCPs）.RDG/ELF graphical analyses were performed to visualize the positions and strengths of the pnicogen bonding,as well as the spatial change of the electron localization upon the formation of complexes.The π-type halogen bond was also calculated,and it has been revealed that the π-type pnicogen bond systems are more stable than the halogen bond ones.展开更多
The excited state intramolecular proton transfer of four derivatives(FM, BFM, BFBC, CCM) of 3-hydroxychromone is investigated.The geometries of different substituents are optimized to study the substituent effects on ...The excited state intramolecular proton transfer of four derivatives(FM, BFM, BFBC, CCM) of 3-hydroxychromone is investigated.The geometries of different substituents are optimized to study the substituent effects on proton transfer.The mechanism of hydrogen bond enhancement is qualitatively elucidated by comparing the infrared spectra, the reduced density gradient, and the frontier molecular orbitals.The calculated electronic spectra are consistent with the experimental results.To quantify the proton transfer, the potential energy curves(PECs) of the four derivatives in S0 and S1 states are scanned.It is concluded that the ability of proton transfer follows the order: FM > BFM > BFBC > CCM.展开更多
By utilizing the density functional theory （DFT） and the time-dependent density functional theory （TDDFT）, the excited state intramolecular proton transfer （ESIPT） mechanism of o-hydroxynaphthyl phenanthroimidaz...By utilizing the density functional theory （DFT） and the time-dependent density functional theory （TDDFT）, the excited state intramolecular proton transfer （ESIPT） mechanism of o-hydroxynaphthyl phenanthroimidazole （HNPI） is studied in detail. Upon photo is excited, the intramolecular hydrogen bond is obviously enhanced in the Sl state, which thus promotes the ESIPT process. Hydrogen bond is shown to be strengthened via comparing the molecular structures and the infrared vibration spectra of the So and S1 states. Through analyzing the frontier molecular orbitals, we can conclude that the excitation is a type of the intramolecular charge transfer excitation, which also indicates the trend of proton transfer in SI state. The vertical excitation based on TDDFT calculation can effectively repeat the absorption and fluorescence spectra of the experiment. However, the fluorescence spectrum of normal structure, which is similar to the spectrum of isomer structure is not detected in the experiment. It can be concluded that the fluorescence measured in the experiment is attributed to both structures. In addition, by analyzing the potential energy curves （PECs） calculated by the B3LYP functional method, it can be derived that since the molecule to cross the potential barrier in the S 1 state is smaller than in the So state and the reverse proton transfer process in the $1 state is more difficult than in the So state, the ESIPT occurs in the S1 state.展开更多
The pnicogen bond interaction between different electron donors(anion, π-electron, heteroatom) and ECl3(E = As, P) was calculated by the method of MP2/aug-cc-p VTZ. It has been indicated that the pnicogen bonds of co...The pnicogen bond interaction between different electron donors(anion, π-electron, heteroatom) and ECl3(E = As, P) was calculated by the method of MP2/aug-cc-p VTZ. It has been indicated that the pnicogen bonds of complex formed by the anion and ECl3 are more stable than that by the neutral electron donor, in which the pnicogen bonds of complex formed by NH3 and ECl3 are the most stable, and that by H2S and ECl3 is the least stable. The nature of pnicogen bond interaction is the closed shell interaction by AIM analysis, and BCP electron density is positively correlated to the complex interaction energy. RDG and DDF graphical analyses are performed to visualize the nature of pnicogen bond interaction from different donors, the position and strength of the pnicogen bond interaction, as well as the rearrangement of electron density after the formation of pnicogen bond system.展开更多
In remote regions with availability of wind energy, a RDG （renewable distributed generation） system is an advantageous alternative to increase the provision of electrical supply. Usually, these systems are structure...In remote regions with availability of wind energy, a RDG （renewable distributed generation） system is an advantageous alternative to increase the provision of electrical supply. Usually, these systems are structured on the basis of a connection to an existing weak grid. When the grid is out of service, the system may operate in islanding mode, if the RDG configuration allows it, continuing the provision of energy with standard voltage and frequency values. Facing the latter situation, a wind-diesel/gas generation system is proposed, with a conversion and control strategies based on a variable speed wind turbine employing a DFIG （doubly fed induction generator）, a SC （ultracapacitor） storage system and a SG （synchronous generator） driven by a diesel/gas engine.展开更多
Due to the high penetration of renewable distributed generation(RDG),many issues have become conspicuous during the intentional island operation such as the power mismatch of load shedding during the transition proces...Due to the high penetration of renewable distributed generation(RDG),many issues have become conspicuous during the intentional island operation such as the power mismatch of load shedding during the transition process and the power imbalance during the restoration process.In this paper,a phase measurement unit(PMU)based online load shedding strategy and a conservation voltage reduction(CVR)based multi-period restoration strategy are proposed for the intentional island with RDG.The proposed load shedding strategy,which is driven by the blackout event,consists of the load shedding optimization and correction table.Before the occurrence of the large-scale blackout,the load shedding optimization is solved periodically to obtain the optimal load shedding plan,which meets the dynamic and steady constraints.When the blackout occurs,the correction table updated in real time based on the PMU data is used to modify the load shedding plan to eliminate the power mismatch caused by the fluctuation of RDG.After the system transits to the intentional island seamlessly,multi-period restoration plans are generated to optimize the restoration performance while maintaining power balance until the main grid is repaired.Besides,CVR technology is implemented to restore more loads by regulating load demand.The proposed load shedding optimization and restoration optimization are linearized to mixed-integer quadratic constraint programming(MIQCP)models.The effectiveness of the proposed strategies is verified with the modified IEEE 33-node system on the real-time digital simulation(RTDS)platform.展开更多
文摘采用优化的RDG (Rappaz-Drezet-Gremaud)热裂模型预测了Mg-5Zn-x Er (x=0.83、1.25、2.5、5,质量分数,%)三元多相合金的铸造热裂敏感性,并利用"约束杆"钢模铸造(CRC)实验评价了该合金的热裂敏感性。结果表明,优化的RDG热裂模型可准确地预测Mg-5Zn-x Er镁合金的热裂敏感性:随着Er含量的增加,合金的热裂敏感性呈先增加后降低的趋势,当Er含量为2.5%时合金的热裂敏感性最高,当Er含量为5.0%时合金的热裂敏感性最低,与实验结果相一致。对铸件凝固曲线、相组成、微观组织等进一步分析表明,当Er含量提高至2.5%时,合金凝固过程发生包晶反应生成I相的同时消耗了液相,并且扩大了合金的凝固温度区间,使合金的热裂敏感性上升;Er含量继续提高至5.0%时,合金在凝固过程中发生L→α-Mg+W的共晶反应,凝固温度区间减小,有利于凝固后期枝晶间裂纹的补缩,显著降低了合金的热裂敏感性。
基金Project(17YF1407100)supported by the Shanghai Sailing Program of ChinaProject(17PJ1408600)supported by Shanghai Pujiang Program of China
文摘The hot cracking tendency of 7075 semi-solid alloy under different conditions was studied by critical diameter method.The experiment and simulation results show that the dendrite arms of the rod grow from the edge to the center.The smaller the diameter of the rod is,the more obvious the directional growth of dendrite is,and the greater the tendency of hot cracking is.Compared with ordinary melt,for semi-solid slurry,increasing mould temperature or decreasing pouring temperature can significantly decrease hot cracking tendency of 7075 alloy,decreasing hot cracking grade from 256 to 100 mm^2.Furthermore,based on the RDG criterion,the effects of solidification conditions on the hot cracking tendency were discussed combined with simulation.At the same time,the application and development of RDG criterion were also researched.
文摘Anion can be identified by pyromellitic imide-azacyclophane which is one of the host compounds.This article investigated the interaction between the host and organic pollution compounds.The host and other eight compounds were optimized by DFT（density functional theory） B3LYP/6-31G level and the energy of compounds was corrected using Boys-Bemardi method.On the basis of B3LYP/6-31G optimized geometries,the RDG function and sign（λ2（r））ρ（r） function values of space points were calculated,and color RDG isosurface map was drawn.3He chemical shift was calculated by the B3LYP/6-31G method.The results showed that the eight organic pollution molecules with the host one shaped stable configurations by hydrogen bonds,respectively.The stabilization energy of complexes 4 and 7 showed repulsion（steric effects） of cyclophane cage observably affecting the stability of the complexes.The location,intensity and the type of interaction in complex 1 were analyzed through color-filled RDG isosurface map.Aromaticity calculations showed that the weak interaction reduced the transverse induction ring current in the host rings,and deteriorated the aromaticity of compounds.
基金Supported by the Science and Technology Project of Zhejiang Province(2016C33039)Natural Science Foundation of Zhejiang Province(LY14C030004)+2 种基金National Natural Science Foundation of China(21272211)Project of the Special Foundation for Provincial Research Institutes of Zhejiang Province,China(2017F50002)Science and Technology Planning Project of the Zhejiang Provincial Department of Water Resources(RB1608)
文摘Intermolecular interactions between PH2Cl and Ar–R（R = H,OH,NH2,CH3,Br,Cl,F,CN,NO2） were calculated by using MP2/aug-cc-p VDZ quantum chemical method.It has been shown from our calculations that the aromatic rings with electron-withdrawing groups represent much weaker binding affinities than those with electron-donating groups.The charge-transfer interaction between PH2Cl and Ar–R plays an important role in the formation of pnicogen bond complexes,as revealed by NBO analysis.Nevertheless,AIM analysis shows that the nature of the interactions between PH2Cl and Ar–R is electrostatic,and the interaction energies of the complexes are correlated positively with the electron densities in the bond critical points（BCPs）.RDG/ELF graphical analyses were performed to visualize the positions and strengths of the pnicogen bonding,as well as the spatial change of the electron localization upon the formation of complexes.The π-type halogen bond was also calculated,and it has been revealed that the π-type pnicogen bond systems are more stable than the halogen bond ones.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11874241,11847224,and 11804195)the Shandong Province Higher Educational Science and Technology Program,China(Grant No.J15LJ03)+1 种基金the Taishan Scholar Project of Shandong Province,China,China Post-Doctoral Foundation(Grant No.2018M630796)the Natural Science Foundation of Shandong Province,China(Grant No.ZR2018BA034)
文摘The excited state intramolecular proton transfer of four derivatives(FM, BFM, BFBC, CCM) of 3-hydroxychromone is investigated.The geometries of different substituents are optimized to study the substituent effects on proton transfer.The mechanism of hydrogen bond enhancement is qualitatively elucidated by comparing the infrared spectra, the reduced density gradient, and the frontier molecular orbitals.The calculated electronic spectra are consistent with the experimental results.To quantify the proton transfer, the potential energy curves(PECs) of the four derivatives in S0 and S1 states are scanned.It is concluded that the ability of proton transfer follows the order: FM > BFM > BFBC > CCM.
基金Project supported by the Shandong Provincial Higher Educational Science and Technology Program,China(Grant No.J17KA186)the Taishan Scholar Project of Shandong Province,China+1 种基金the Natural Science Foundation of Liaoning Province,China(Grant No.20170540408)the Science and Technology Plan Project of Shenyang City,China(Grant No.17-231-1-06)
文摘By utilizing the density functional theory （DFT） and the time-dependent density functional theory （TDDFT）, the excited state intramolecular proton transfer （ESIPT） mechanism of o-hydroxynaphthyl phenanthroimidazole （HNPI） is studied in detail. Upon photo is excited, the intramolecular hydrogen bond is obviously enhanced in the Sl state, which thus promotes the ESIPT process. Hydrogen bond is shown to be strengthened via comparing the molecular structures and the infrared vibration spectra of the So and S1 states. Through analyzing the frontier molecular orbitals, we can conclude that the excitation is a type of the intramolecular charge transfer excitation, which also indicates the trend of proton transfer in SI state. The vertical excitation based on TDDFT calculation can effectively repeat the absorption and fluorescence spectra of the experiment. However, the fluorescence spectrum of normal structure, which is similar to the spectrum of isomer structure is not detected in the experiment. It can be concluded that the fluorescence measured in the experiment is attributed to both structures. In addition, by analyzing the potential energy curves （PECs） calculated by the B3LYP functional method, it can be derived that since the molecule to cross the potential barrier in the S 1 state is smaller than in the So state and the reverse proton transfer process in the $1 state is more difficult than in the So state, the ESIPT occurs in the S1 state.
基金supported by the Public Technology Research Project(Analysis and Measurement)of Zhejiang Province(LGC19B070004)State Key Laboratory of Environmental Chemistry and Ecotoxicology,Research Center for Eco-environmental Sciences,Chinese Academy of Sciences(KF2018-15)Program for the Philosophy and Social Research in Zhejiang Province(19NDJC262YB)
文摘The pnicogen bond interaction between different electron donors(anion, π-electron, heteroatom) and ECl3(E = As, P) was calculated by the method of MP2/aug-cc-p VTZ. It has been indicated that the pnicogen bonds of complex formed by the anion and ECl3 are more stable than that by the neutral electron donor, in which the pnicogen bonds of complex formed by NH3 and ECl3 are the most stable, and that by H2S and ECl3 is the least stable. The nature of pnicogen bond interaction is the closed shell interaction by AIM analysis, and BCP electron density is positively correlated to the complex interaction energy. RDG and DDF graphical analyses are performed to visualize the nature of pnicogen bond interaction from different donors, the position and strength of the pnicogen bond interaction, as well as the rearrangement of electron density after the formation of pnicogen bond system.
文摘In remote regions with availability of wind energy, a RDG （renewable distributed generation） system is an advantageous alternative to increase the provision of electrical supply. Usually, these systems are structured on the basis of a connection to an existing weak grid. When the grid is out of service, the system may operate in islanding mode, if the RDG configuration allows it, continuing the provision of energy with standard voltage and frequency values. Facing the latter situation, a wind-diesel/gas generation system is proposed, with a conversion and control strategies based on a variable speed wind turbine employing a DFIG （doubly fed induction generator）, a SC （ultracapacitor） storage system and a SG （synchronous generator） driven by a diesel/gas engine.
基金This work was supported in part by the National Key R&D Program of China(No.2017YFB0902900)the National Natural Science Foundation of China(No.51707136)the Natural Science Foundation of Hubei Province(No.2018CFA080).
文摘Due to the high penetration of renewable distributed generation(RDG),many issues have become conspicuous during the intentional island operation such as the power mismatch of load shedding during the transition process and the power imbalance during the restoration process.In this paper,a phase measurement unit(PMU)based online load shedding strategy and a conservation voltage reduction(CVR)based multi-period restoration strategy are proposed for the intentional island with RDG.The proposed load shedding strategy,which is driven by the blackout event,consists of the load shedding optimization and correction table.Before the occurrence of the large-scale blackout,the load shedding optimization is solved periodically to obtain the optimal load shedding plan,which meets the dynamic and steady constraints.When the blackout occurs,the correction table updated in real time based on the PMU data is used to modify the load shedding plan to eliminate the power mismatch caused by the fluctuation of RDG.After the system transits to the intentional island seamlessly,multi-period restoration plans are generated to optimize the restoration performance while maintaining power balance until the main grid is repaired.Besides,CVR technology is implemented to restore more loads by regulating load demand.The proposed load shedding optimization and restoration optimization are linearized to mixed-integer quadratic constraint programming(MIQCP)models.The effectiveness of the proposed strategies is verified with the modified IEEE 33-node system on the real-time digital simulation(RTDS)platform.
