A novel tetra-europium(III)-containing antimonotungstate,Na_(8.2)[H_(2)N(CH_(3))_(2)]_(9)[Na_(10.8)(tar)_(4)(H_(2)O)_(20)(Eu_(2)Sb_(2)W_(21)O_(72))_(2)]·44.5H_(2)O(EuSbW,H_(4)tar=dl-tartaric acid),has been synthe...A novel tetra-europium(III)-containing antimonotungstate,Na_(8.2)[H_(2)N(CH_(3))_(2)]_(9)[Na_(10.8)(tar)_(4)(H_(2)O)_(20)(Eu_(2)Sb_(2)W_(21)O_(72))_(2)]·44.5H_(2)O(EuSbW,H_(4)tar=dl-tartaric acid),has been synthesized and characterized.The dimeric polyoxoanion of EuSbW consists of two Dawson-like{Eu_(2)Sb_(2)W_(21)}units bridged by four dl-tartaric acid ligands.The adjacent carboxyl and hydroxy groups in each tartaric acid simultaneously chelate with W and Eu atoms from different{Eu_(2)Sb_(2)W_(21)}units,thereby forming the dimeric structure.EuSbW represents an extremely rare polyoxometalate where four tartaric acid ligands function as connectors to bridge two{Eu_(2)Sb_(2)W_(21)}units.Additionally,EuSbW exhibits excellent catalytic activity and reusability in the oxidation of thioethers and alcohols,achieving 100%conversion and>99%selectivity for various thioethers,and 85–100%conversion with 90–99%selectivity for diverse alcohols under mild conditions.展开更多
By introduction of hydrogen peroxide into the reaction system of ZrOCl_(2)·8H_(2)O and K14[As_(2)W_(19)O_(67)(H_(2)O)],a novel polyoxometalate K_(8)Na_(19.5)H_(0.5)[Zr_(2)(O_(2))_(2)(β-AsVW_(10)O_(38))]4·68...By introduction of hydrogen peroxide into the reaction system of ZrOCl_(2)·8H_(2)O and K14[As_(2)W_(19)O_(67)(H_(2)O)],a novel polyoxometalate K_(8)Na_(19.5)H_(0.5)[Zr_(2)(O_(2))_(2)(β-AsVW_(10)O_(38))]4·68H_(2)O(1)has been successfully obtained via one-pot method and systematically characterized by IR,XPS,solid UV spectra,PXRD pattern,and TGA analysis.The analysis of X-ray crystallography exhibits that compound 1 crystallizes in the triclinic space group P-1 and presents a novel square-shaped Zr-substituted tetrameric polyoxometalate.The catalytic oxidation of sulfides by 1 are carried out,which demonstrate that 1 exhibits a good performance for the catalytic oxidation of sulfides to sulfones with high conversion(100%)and high selectivity(100%).展开更多
Three lanthanide ions and a rigid(1,1'-biphenyl)-2,4,6-tricarboxylic acid(H_(3)bptc) ligand led to the isostructural lanthanide metal-organic frameworks(Ln-MOFs) {[Ln(bptc)(H_(2)O)_(3)]·3H_(2)O}_n(Lnbptc, Ln ...Three lanthanide ions and a rigid(1,1'-biphenyl)-2,4,6-tricarboxylic acid(H_(3)bptc) ligand led to the isostructural lanthanide metal-organic frameworks(Ln-MOFs) {[Ln(bptc)(H_(2)O)_(3)]·3H_(2)O}_n(Lnbptc, Ln = Eu,Tb, Gd, Eu_(x)Tb_(1—x), Eu_(x)Gd_(1-x), Tb_(x)Gd_(1-x), and Eu_(0.12)Tb_(0.52)Gd_(0.36)). The density functional theory(DFT) and time-dependent DFT calculation were expanded on H_3bptc, which point to the occurrence of “antenna effect”. The minor diameter samples of Eubptc, Tbbptc, and Gdbptc can also be attained via the microwave synthesis and employed for handwriting anticounterfeiting. Interestingly, the typical red emission of Eu^(3+) and green emission of Tb~(3+) could be fine-tuned by Gd^(3+) via chemical mixing to be full-color emissions bimetallic doped Eu_(x)Tb_(1-x)bptc, Eu_(x)Gd_(1-x)bptc, and Tb_(x)Gd_(1-x)bptc. The above synthetic bimetallic MOFs can be fixed in positioning boxes of quick response(QR) codes with diverse emission for anticounterfeiting. The message can be decoded under the irradiation of 365 nm ultraviolet lamp while invisible in the daylight. Notably, the trimetallic doped Eu_(0.12)Tb_(0.52)Gd_(0.36)bptc emits white light with the CIE color coordinate(0.34, 0.34). Furthermore, Tbbptc is demonstrated to be a sensitive probe toward nitrobenzene and acetone with multiple mechanisms.展开更多
A H_(4)SiW_(12)O_(40)-catalyzed three-component tandem reaction of 2-acylbenzoic acids,primary amines and phosphine oxides to form 3,3-disubstituted isoindolinones was developed.By employing A H_(4)SiW_(12)O_(40)as th...A H_(4)SiW_(12)O_(40)-catalyzed three-component tandem reaction of 2-acylbenzoic acids,primary amines and phosphine oxides to form 3,3-disubstituted isoindolinones was developed.By employing A H_(4)SiW_(12)O_(40)as the catalyst and dimethyl carbonate(DMC)as the solvent,a diverse range of 2-acylbenzoic acid derivatives and primary amines worked well to give the C3-phosphinoyl-functionalized 3,3-disubstituted isoindolinones with the yield range of 61%-87%.Advantages of this transformation include green catalyst and solvent,available starting materials,broad substrate scope,high efficiency and operational simplicity with water as the sole by-product.The strategy achieved an efficient and green molecular fragment assembly to access isoindolinones,which would provide opportunities for the synthesis of potential biologically active molecules in a green manner.展开更多
The objective of this study was to investigate the influence of strengthening mechanisms on the high-temperature mechanical properties of China low-activation ferrite(CLF-1)steel,which underwent thermodynamic design a...The objective of this study was to investigate the influence of strengthening mechanisms on the high-temperature mechanical properties of China low-activation ferrite(CLF-1)steel,which underwent thermodynamic design and thermo-mechanical treatment(TMT).The microstructure characterization in the normalized and tempered condition and the TMT condition was carried out using optical microscopy,X-ray diffractometer,and scanning electron microscopy with electron backscatter diffraction.High-resolution transmission electron microscopy was employed to determine the crystallographic structures of precipitated phases.The results indicated that the addition of Ti led to an increase in the allocation of C in MC phase and an enhancement in the content of MC phase.Compared to CLF-P steel in the normalized and tempered condition,a 1.5-fold increase in dislocation density and an order of magnitude improvement in MX phase density were achieved after TMT.The formation of high-density nano-scale MC phases during TMT played a significant role in precipitation strengthening due to their favorable coherent relationship with the matrix and low interfacial free energy.The excellent high-temperature mechanical properties observed in CLF-P steel after TMT can be attributed to the combined effects of precipitation strengthening,dislocation strengthening,and lath strengthening.展开更多
Nitroaromatic hydrogenation catalysis without precious metals remains a longstanding challenge.The rate of electron transfer is the crucial factor affecting hydrogenation catalysis.Herein,an ionic Cd-based metal-organ...Nitroaromatic hydrogenation catalysis without precious metals remains a longstanding challenge.The rate of electron transfer is the crucial factor affecting hydrogenation catalysis.Herein,an ionic Cd-based metal-organic framework(I-Cd-MOF)exhibiting a unique structure with one-dimensional(1D)opening nanochannels and good electron transfer ability was synthesized for catalyzing hydrogenation of 4-nitrophenol(4-NP).The catalytic activity of the unique I-Cd-MOF without noble metals is detected,which is higher than most reported noble metal catalysts.Remarkably,the reaction rate of I-Cd-MOF(4.28 min^(-1))is about 47.6 times higher than that of the Cd-based neutral MOF(N-Cd-MOF)with the similar crystalline structure.Liquid chromatograph mass spectrometer(LC-MS)and theoretical results demonstrate that 4-NP and five intermediates are stabilized in the channels of I-Cd-MOF,which increases the possibility of contact with H^*and H_(2)g enerated at the Cd sites.The I-Cd-MOF was extended to other nitroaromatic hydrogenation catalysis,which still displays excellent activity.More importantly,the I-MOF@Filter membrane was successfully constructed for continuous hydrogenation catalytic reactions,which maintains a high catalytic performance after 7 cycles of recycling without washing.This work fills in the application of the I-MOFs in hydrogenation catalytic reactions and provides an effective way for the rapid and green degradation of nitroaromatic compounds.展开更多
A dimeric Y(III)-containing antimonotungstate[Y_(4)(H_(2)O)_(8)(mal)_(2)(OAc)O(Sb_(2)W_(2)^(V)W_(19)^(VI)O_(72))_(2)]^(21-)(Y_(4)mal_(2),H_(3)mal=DL-malic acid),resembling a“handshake”configuration,was synthesized a...A dimeric Y(III)-containing antimonotungstate[Y_(4)(H_(2)O)_(8)(mal)_(2)(OAc)O(Sb_(2)W_(2)^(V)W_(19)^(VI)O_(72))_(2)]^(21-)(Y_(4)mal_(2),H_(3)mal=DL-malic acid),resembling a“handshake”configuration,was synthesized and characterized.The polyanion of Y_(4)mal_(2)consists of two Dawson-derived{Y_(2)Sb_(2)W_(21)}moieties that are further linked by two mal ligands and oneμ_(2)-bridging acetate to form an asymmetric polyanion.Notably,the chiral configuration induced by the D-or L-configuration of the mal ligand results in both{Y_(2)Sb_(2)W_(21)}moieties within one polyanion exhibiting identical chirality,leading to the racemate crystallization of Y_(4)mal_(2).Moreover,Y_(4)mal_(2)exhibits excellent Lewis acid catalytic activity for environmentally friendly synthesis of imidazoles.展开更多
The upper montane evergreen broad-leaved forest in Yunnan occurs mainly in the zone of persistent cloud and has a discontinuous,island-like,distribution.It is diverse,rich in endemic species,and likely to be sensitive...The upper montane evergreen broad-leaved forest in Yunnan occurs mainly in the zone of persistent cloud and has a discontinuous,island-like,distribution.It is diverse,rich in endemic species,and likely to be sensitive to climate change.Six 1-ha sampling plots were established across the main distribution area of the upper montane evergreen broad-leaved forest in Yunnan.All trees with d.b.h.>1 cm in each plot were identified.Patterns of seed plant distributions were quantified at the specific,generic and family levels.The forests are dominated by the families Fagaceae,Lauraceae,Theaceae and Magnoliaceae,but are very diverse with only a few species shared between sites.Floristic similarities at the family and generic level were high,but they were low at the specific level,with species complementarity between plots.Diversity varied greatly among sites,with greater species richness and more rare species in western Yunnan than central Yunnan.The flora is dominated by tropical biogeographical elements,mainly the pantropic and the tropical Asian distributions at the family and genus levels.In contrast,at the species level,the flora is dominated by the southwest or the southeast China distributions,including Yunnan endemics.This suggests that the flora of the upper montane forest in Yunnan could have a tropical floristic origin,and has adapted to cooler temperatures with the uplift of the Himalayas.Due to great sensitivity to climate,high endemism and species complementarity,as well as the discontinuous,island-like,distribution patterns of the upper montane forest in Yunnan,the regional conservation of the forest is especially needed.展开更多
Rotationally symmetric workpieces of Ti_(2)AlNb-based alloys have great potential for high-temperature service condition in aviation industry,while the poor workability limits their application until now.In this study...Rotationally symmetric workpieces of Ti_(2)AlNb-based alloys have great potential for high-temperature service condition in aviation industry,while the poor workability limits their application until now.In this study,shear spinning and heat treatment were first conducted to investigate the corresponding microstructure evolution and mechanical properties of Ti_(2)AlNb conical workpieces.The microstructure of the 1^(st) and 2^(nd) pass spun workpieces(SP1 and SP2)mainly consisted of B2+retainedα2phases.After two passes spinning,the B2 phase texture changed from<111>//ND of as-received alloy to be<001>//ND.The ultimate tensile stress(UTS)of SP1 and SP2 was increased to 1163 MPa and 932 MPa,respectively,compared with 782 MPa of as-received alloy at 650℃.Also,the yield stress anomaly(YSA)occurred in SP1 and SP2 because{110}<111>and{112}<111>cross slip systems of B2 phase were difficult to slip at or below room temperature(RT),but they became active at 650℃ and above.As an essential step for increasing the spinnability of multi-pass spinning process of the Ti_(2)AlNb alloy,the H3heat treatment scheme,i.e.960℃/2 h+850℃/12 h,was carried out between two successive passes to increase the hot workability,by which the ductility of the heat treated as-spun workpieces with the microstructure of B2+primary O+acicular secondary O+high amount spheroidizedα2phases reached 72.1%at 900℃.After being subject to the H1 heat treatment scheme,i.e.960℃-2 h,the spun workpieces with the microstructure of B2+primary O+intergranular primaryα2phases achieved an optimized comprehensive mechanical properties both at room temperature and 650℃,which should be chosen as the post-spinning heat treatment process for the service requirement.展开更多
A versatile heteropoly acid(H_(3)PMo_(12)O_(40))-catalyzed coupling of diarylmethanols with epoxides was established for the synthesis of polyaryl-substituted aldehydes.Furthermore,the catalytic system was also suitab...A versatile heteropoly acid(H_(3)PMo_(12)O_(40))-catalyzed coupling of diarylmethanols with epoxides was established for the synthesis of polyaryl-substituted aldehydes.Furthermore,the catalytic system was also suitable for the reaction of diarylmethanols and diols/aldehydes.The application of such an earthabundant,readily accessible,and nontoxic catalyst provides a green approach for the construction of polyaryl-substituted aldehydes.展开更多
An excellent cardinality estimation can make the query optimiser produce a good execution plan.Although there are some studies on cardinality estimation,the prediction results of existing cardinality estimators are in...An excellent cardinality estimation can make the query optimiser produce a good execution plan.Although there are some studies on cardinality estimation,the prediction results of existing cardinality estimators are inaccurate and the query efficiency cannot be guaranteed as well.In particular,they are difficult to accurately obtain the complex relationships between multiple tables in complex database systems.When dealing with complex queries,the existing cardinality estimators cannot achieve good results.In this study,a novel cardinality estimator is proposed.It uses the core techniques with the BiLSTM network structure and adds the attention mechanism.First,the columns involved in the query statements in the training set are sampled and compressed into bitmaps.Then,the Word2vec model is used to embed the word vectors about the query statements.Finally,the BiLSTM network and attention mechanism are employed to deal with word vectors.The proposed model takes into consideration not only the correlation between tables but also the processing of complex predicates.Extensive experiments and the evaluation of BiLSTM-Attention Cardinality Estimator(BACE)on the IMDB datasets are conducted.The results show that the deep learning model can significantly improve the quality of cardinality estimation,which is a vital role in query optimisation for complex databases.展开更多
We present the synthesis,characterization and photoluminescence properties of uranium-containing selenotungstate,[(UO_(2))_(3)(SeO_(3))_(3)Na_(5)(H_(2)O)_(6)(SeW_(6)O_(21))(SeW_(9)O_(33))_(3)]^(21–),which was isolate...We present the synthesis,characterization and photoluminescence properties of uranium-containing selenotungstate,[(UO_(2))_(3)(SeO_(3))_(3)Na_(5)(H_(2)O)_(6)(SeW_(6)O_(21))(SeW_(9)O_(33))_(3)]^(21–),which was isolated by a one-pot reaction of uranium nitrate with sodium tungstate and sodium selenite in a pH 5.2 aqueous solution at 90°C.In this study,the effect of the introduction of lone-electron pair containing heteroatoms on the structure is demonstrated,a three-layered heterometallic{Se_(3)U_(3)Na_(5)}cluster is encapsulated by two different anionic building block units:three trivacant Keggin{B-α-Se W_(9)O_(33)}and one Anderson{SeW_(6)O_(21)}.To our knowledge,the{Se_(3)U_(3)Na_(5)}cluster has never been observed in the polyoxometalate chemistry.The solidstate photoluminescence properties and lifetime decay behaviours of the title compound(1)have been measured at room temperature,and the photoluminescence spectrum displays the characteristic emission bands of corresponding uranyl cations.In addition,the photoluminescence quantum yield of 1 is 72%,which is almost three times that of starting material UO_(2)(NO_(3))_(2)·6H_(2)O(27%).By using this strategy,we envision that an increasing number of assemblies with‘open’clusters may be designed and obtained,in which the exposed oxygen atoms show strong affinity towards metal ions,providing new opportunities to generate bigger clusters or to tune existing properties.展开更多
Two novel uranium-containing selenotungstates Na_(3)[H_(19)(UO_(2))_(2)(μ_(2)-O)(Se_(2)W_(14)O_(52))_(2)]·41 H_(2)O(U_(2))and(NH_(4))_(10)[H_(4)(SeO)_(2)(UO_(2))_(2)(H_(2)O)_(2)(H_(2)Se_(2)W_(14)O_(52))(Se_(2)W_...Two novel uranium-containing selenotungstates Na_(3)[H_(19)(UO_(2))_(2)(μ_(2)-O)(Se_(2)W_(14)O_(52))_(2)]·41 H_(2)O(U_(2))and(NH_(4))_(10)[H_(4)(SeO)_(2)(UO_(2))_(2)(H_(2)O)_(2)(H_(2)Se_(2)W_(14)O_(52))(Se_(2)W_(14)O_(52))]·66 H_(2)O(Se_(2)U_(2))based on the{Se_(2)W_(14)O_(52)}unit were successfully prepared and fully characterized.To our knowledge,the uranium is firstly introduced into the selenotungstates.Moreover,it is notable that U_(2)exhibits excellent Lewis acid-base catalytic activities in the condensation cyclization of sulfonyl hydrazides with diketones to synthesize polysubstituted pyrazoles.All the desired products were obtained in moderate to good yields(up to 99%).展开更多
Three imidazole-modified Ag-polyoxovanadates frameworks(APFs)with a controllable molar ratio of Ag+to polyoxovanadates(POVs)[Ag(IM)_(2)]_(2)V_(4)O_(12)·2Ag(IM)_(2)(APF-1),[Ag_(2)(1-eIM)_(4)]_(2)[Ag(1-eIM)_(2)]_(3...Three imidazole-modified Ag-polyoxovanadates frameworks(APFs)with a controllable molar ratio of Ag+to polyoxovanadates(POVs)[Ag(IM)_(2)]_(2)V_(4)O_(12)·2Ag(IM)_(2)(APF-1),[Ag_(2)(1-eIM)_(4)]_(2)[Ag(1-eIM)_(2)]_(3)·2Ag(1-eIM)_(2)·3(1-HeIM)[V_(10)O_(28)]_(2)(APF-2)and[Ag(1-pIM)_(2)]_(3)[HV_(10)O_(28)]·2Ag(1-pIM)_(2)·2H_(2)O(APF-3)(IM=imida-zole;1-eIM=1-ethylimidazole and 1-pIM=1-propylimidazole)have been successfully achieved by self-assembly of POVs,Ag+cations,and three different imidazole derivatives.Interestingly,the molar ratios of Ag+to POVs vary from 4:1,4.5:1 to 5:1 by changing the vanadium resources and imidazole deriva-tives.Notably,the coordination environment of Ag+cations and the structure of POVs in the APFs are also different.Specifically,for APF-1,the four Ag atoms adopt three-coordinated and four-coordinated geometries,respectively,and Ag-imidazole complexes and[V_(4)O 1_(2)]_(4)−cluster form the one-dimensional polymeric chains.While Ag atoms in APF-2 and APF-3 exhibit two-,four-and five-coordinated geome-tries for APF-2,four-,five-and six-coordinated geometries for APF-3,respectively.These Ag+cations and decavanadate clusters are assembled into the 2D supramolecular structure through the Ag-O bonds and Ag…Ag argentophilic interaction.Remarkably,thus-obtained APF-2 can serve as powerful efficient hetero-geneous catalyst for construction of C–N bond and detoxification of simulant sulfur mustard(yields up to 99%),which enable successful recycling for three cycles with remained catalytic activities and structure stability.展开更多
A simple and efficient method for the synthesis of pyrazoles through a silicotungstic acid (H_(4)SiW_(12)O_(40))-catalyzed cyclization of epoxides/aldehydes and sulfonyl hydrazides has been developed. Various epoxides...A simple and efficient method for the synthesis of pyrazoles through a silicotungstic acid (H_(4)SiW_(12)O_(40))-catalyzed cyclization of epoxides/aldehydes and sulfonyl hydrazides has been developed. Various epoxides/aldehydes were smoothly reacted with sulfonyl hydrazides to furnish regioselectivity 3,4-disubstituted 1H-pyrazoles. The application of such an earth-abundant, readily accessible, and nontoxic catalyst provides a green approach for the construction of 3,4-disubstituted 1H-pyrazoles. A plausible reaction mechanism has been proposed on the basis of control experiments, GC-MS and DFT calculations.展开更多
In order to improve the impactor performance, the dynamic performance of gas-liquid united hydraulic hammer should be optimized. Based on the analysis of the operating principle for the hydraulic impactor, one simulat...In order to improve the impactor performance, the dynamic performance of gas-liquid united hydraulic hammer should be optimized. Based on the analysis of the operating principle for the hydraulic impactor, one simulation model of gas-liquid united hydraulic impactor was built with AMESim software. By setting different simulation parameters, curves of displacement, velocity, acceleration and cavity pressure were obtained under different working conditions. The key component can be obtained by the analysis of activity index. The whole simulation results provide a reliable basis for component selection and parameter optimization of hydraulic impactor.展开更多
The structure and operational principle on a new type reversing valve of hydraulic breaker are introduced. The nonlinear mathematic model and simulation model of the new type reversing valve are built. The dynamic sim...The structure and operational principle on a new type reversing valve of hydraulic breaker are introduced. The nonlinear mathematic model and simulation model of the new type reversing valve are built. The dynamic simulation research of the new type reversing valve is conducted. The effects of the system parameters on the working performance are researched systematically and deeply. The regular understanding on the motion of the reversing valve is obtained, which provides theoretical basis for the innovation and manufacturing of a new generation of hydraulic breaker reversing valve.展开更多
In order to improve the impact performance, the structure of hydraulic hammer should be optimized. In this paper, the ranges of eight vital structure parameters of piston and reversing valve system of hydraulic hammer...In order to improve the impact performance, the structure of hydraulic hammer should be optimized. In this paper, the ranges of eight vital structure parameters of piston and reversing valve system of hydraulic hammer were selected firstly;and then found the best value of different parameters under experiments with the method of computer optimization and the parametric analysis method provided by ADAMS software. These methods worked and the best design values of parameters of hydraulic hammer were obtained. At last, the optimal impact energy of virtual prototype of hydraulic breaking hammer was calculated and compared with the original impact performance. The results reveal that impact performance of hydraulic hammer has been improved significantly.展开更多
基金supported by the Natural Science Foundation of Jiangxi Province(20232ACB213005).
文摘A novel tetra-europium(III)-containing antimonotungstate,Na_(8.2)[H_(2)N(CH_(3))_(2)]_(9)[Na_(10.8)(tar)_(4)(H_(2)O)_(20)(Eu_(2)Sb_(2)W_(21)O_(72))_(2)]·44.5H_(2)O(EuSbW,H_(4)tar=dl-tartaric acid),has been synthesized and characterized.The dimeric polyoxoanion of EuSbW consists of two Dawson-like{Eu_(2)Sb_(2)W_(21)}units bridged by four dl-tartaric acid ligands.The adjacent carboxyl and hydroxy groups in each tartaric acid simultaneously chelate with W and Eu atoms from different{Eu_(2)Sb_(2)W_(21)}units,thereby forming the dimeric structure.EuSbW represents an extremely rare polyoxometalate where four tartaric acid ligands function as connectors to bridge two{Eu_(2)Sb_(2)W_(21)}units.Additionally,EuSbW exhibits excellent catalytic activity and reusability in the oxidation of thioethers and alcohols,achieving 100%conversion and>99%selectivity for various thioethers,and 85–100%conversion with 90–99%selectivity for diverse alcohols under mild conditions.
基金financially supported by the National Natural Science Foundation of China(No.22071043).
文摘By introduction of hydrogen peroxide into the reaction system of ZrOCl_(2)·8H_(2)O and K14[As_(2)W_(19)O_(67)(H_(2)O)],a novel polyoxometalate K_(8)Na_(19.5)H_(0.5)[Zr_(2)(O_(2))_(2)(β-AsVW_(10)O_(38))]4·68H_(2)O(1)has been successfully obtained via one-pot method and systematically characterized by IR,XPS,solid UV spectra,PXRD pattern,and TGA analysis.The analysis of X-ray crystallography exhibits that compound 1 crystallizes in the triclinic space group P-1 and presents a novel square-shaped Zr-substituted tetrameric polyoxometalate.The catalytic oxidation of sulfides by 1 are carried out,which demonstrate that 1 exhibits a good performance for the catalytic oxidation of sulfides to sulfones with high conversion(100%)and high selectivity(100%).
基金Project supported by the National Natural Science Foundation of China(22071194,21971207)。
文摘Three lanthanide ions and a rigid(1,1'-biphenyl)-2,4,6-tricarboxylic acid(H_(3)bptc) ligand led to the isostructural lanthanide metal-organic frameworks(Ln-MOFs) {[Ln(bptc)(H_(2)O)_(3)]·3H_(2)O}_n(Lnbptc, Ln = Eu,Tb, Gd, Eu_(x)Tb_(1—x), Eu_(x)Gd_(1-x), Tb_(x)Gd_(1-x), and Eu_(0.12)Tb_(0.52)Gd_(0.36)). The density functional theory(DFT) and time-dependent DFT calculation were expanded on H_3bptc, which point to the occurrence of “antenna effect”. The minor diameter samples of Eubptc, Tbbptc, and Gdbptc can also be attained via the microwave synthesis and employed for handwriting anticounterfeiting. Interestingly, the typical red emission of Eu^(3+) and green emission of Tb~(3+) could be fine-tuned by Gd^(3+) via chemical mixing to be full-color emissions bimetallic doped Eu_(x)Tb_(1-x)bptc, Eu_(x)Gd_(1-x)bptc, and Tb_(x)Gd_(1-x)bptc. The above synthetic bimetallic MOFs can be fixed in positioning boxes of quick response(QR) codes with diverse emission for anticounterfeiting. The message can be decoded under the irradiation of 365 nm ultraviolet lamp while invisible in the daylight. Notably, the trimetallic doped Eu_(0.12)Tb_(0.52)Gd_(0.36)bptc emits white light with the CIE color coordinate(0.34, 0.34). Furthermore, Tbbptc is demonstrated to be a sensitive probe toward nitrobenzene and acetone with multiple mechanisms.
基金the National Natural Science Foundation of China(No.22001034)Jiangxi Provincial Natural Science Foundation(No.20212BAB213001).
文摘A H_(4)SiW_(12)O_(40)-catalyzed three-component tandem reaction of 2-acylbenzoic acids,primary amines and phosphine oxides to form 3,3-disubstituted isoindolinones was developed.By employing A H_(4)SiW_(12)O_(40)as the catalyst and dimethyl carbonate(DMC)as the solvent,a diverse range of 2-acylbenzoic acid derivatives and primary amines worked well to give the C3-phosphinoyl-functionalized 3,3-disubstituted isoindolinones with the yield range of 61%-87%.Advantages of this transformation include green catalyst and solvent,available starting materials,broad substrate scope,high efficiency and operational simplicity with water as the sole by-product.The strategy achieved an efficient and green molecular fragment assembly to access isoindolinones,which would provide opportunities for the synthesis of potential biologically active molecules in a green manner.
基金This work was supported by the State Key Laboratory of Nuclear Physics and Technology,Peking University(No.NPT2021KF-ZX).
文摘The objective of this study was to investigate the influence of strengthening mechanisms on the high-temperature mechanical properties of China low-activation ferrite(CLF-1)steel,which underwent thermodynamic design and thermo-mechanical treatment(TMT).The microstructure characterization in the normalized and tempered condition and the TMT condition was carried out using optical microscopy,X-ray diffractometer,and scanning electron microscopy with electron backscatter diffraction.High-resolution transmission electron microscopy was employed to determine the crystallographic structures of precipitated phases.The results indicated that the addition of Ti led to an increase in the allocation of C in MC phase and an enhancement in the content of MC phase.Compared to CLF-P steel in the normalized and tempered condition,a 1.5-fold increase in dislocation density and an order of magnitude improvement in MX phase density were achieved after TMT.The formation of high-density nano-scale MC phases during TMT played a significant role in precipitation strengthening due to their favorable coherent relationship with the matrix and low interfacial free energy.The excellent high-temperature mechanical properties observed in CLF-P steel after TMT can be attributed to the combined effects of precipitation strengthening,dislocation strengthening,and lath strengthening.
基金the financial support provided by the NSFC(No.21531007)the Shaanxi Provincial Natural Science Basic Research Program(No.2019JM-590)the Shaanxi Science and Technology Department(Nos.2022GY-384,2022JBGS2–07,2021LLRH05–21,2022QFY06–06)。
文摘Nitroaromatic hydrogenation catalysis without precious metals remains a longstanding challenge.The rate of electron transfer is the crucial factor affecting hydrogenation catalysis.Herein,an ionic Cd-based metal-organic framework(I-Cd-MOF)exhibiting a unique structure with one-dimensional(1D)opening nanochannels and good electron transfer ability was synthesized for catalyzing hydrogenation of 4-nitrophenol(4-NP).The catalytic activity of the unique I-Cd-MOF without noble metals is detected,which is higher than most reported noble metal catalysts.Remarkably,the reaction rate of I-Cd-MOF(4.28 min^(-1))is about 47.6 times higher than that of the Cd-based neutral MOF(N-Cd-MOF)with the similar crystalline structure.Liquid chromatograph mass spectrometer(LC-MS)and theoretical results demonstrate that 4-NP and five intermediates are stabilized in the channels of I-Cd-MOF,which increases the possibility of contact with H^*and H_(2)g enerated at the Cd sites.The I-Cd-MOF was extended to other nitroaromatic hydrogenation catalysis,which still displays excellent activity.More importantly,the I-MOF@Filter membrane was successfully constructed for continuous hydrogenation catalytic reactions,which maintains a high catalytic performance after 7 cycles of recycling without washing.This work fills in the application of the I-MOFs in hydrogenation catalytic reactions and provides an effective way for the rapid and green degradation of nitroaromatic compounds.
基金supported by the National Natural Science Foundation of China(Nos.22301034,22301033)the Jiangxi Provincial Natural Science Foundation(No.20232ACB213005)。
文摘A dimeric Y(III)-containing antimonotungstate[Y_(4)(H_(2)O)_(8)(mal)_(2)(OAc)O(Sb_(2)W_(2)^(V)W_(19)^(VI)O_(72))_(2)]^(21-)(Y_(4)mal_(2),H_(3)mal=DL-malic acid),resembling a“handshake”configuration,was synthesized and characterized.The polyanion of Y_(4)mal_(2)consists of two Dawson-derived{Y_(2)Sb_(2)W_(21)}moieties that are further linked by two mal ligands and oneμ_(2)-bridging acetate to form an asymmetric polyanion.Notably,the chiral configuration induced by the D-or L-configuration of the mal ligand results in both{Y_(2)Sb_(2)W_(21)}moieties within one polyanion exhibiting identical chirality,leading to the racemate crystallization of Y_(4)mal_(2).Moreover,Y_(4)mal_(2)exhibits excellent Lewis acid catalytic activity for environmentally friendly synthesis of imidazoles.
基金supported by the National Natural Science Foundation of China,No.41471051,41071040,31170195
文摘The upper montane evergreen broad-leaved forest in Yunnan occurs mainly in the zone of persistent cloud and has a discontinuous,island-like,distribution.It is diverse,rich in endemic species,and likely to be sensitive to climate change.Six 1-ha sampling plots were established across the main distribution area of the upper montane evergreen broad-leaved forest in Yunnan.All trees with d.b.h.>1 cm in each plot were identified.Patterns of seed plant distributions were quantified at the specific,generic and family levels.The forests are dominated by the families Fagaceae,Lauraceae,Theaceae and Magnoliaceae,but are very diverse with only a few species shared between sites.Floristic similarities at the family and generic level were high,but they were low at the specific level,with species complementarity between plots.Diversity varied greatly among sites,with greater species richness and more rare species in western Yunnan than central Yunnan.The flora is dominated by tropical biogeographical elements,mainly the pantropic and the tropical Asian distributions at the family and genus levels.In contrast,at the species level,the flora is dominated by the southwest or the southeast China distributions,including Yunnan endemics.This suggests that the flora of the upper montane forest in Yunnan could have a tropical floristic origin,and has adapted to cooler temperatures with the uplift of the Himalayas.Due to great sensitivity to climate,high endemism and species complementarity,as well as the discontinuous,island-like,distribution patterns of the upper montane forest in Yunnan,the regional conservation of the forest is especially needed.
基金financially supported by the National Natural Science Foundation of China (No. 51775137)。
文摘Rotationally symmetric workpieces of Ti_(2)AlNb-based alloys have great potential for high-temperature service condition in aviation industry,while the poor workability limits their application until now.In this study,shear spinning and heat treatment were first conducted to investigate the corresponding microstructure evolution and mechanical properties of Ti_(2)AlNb conical workpieces.The microstructure of the 1^(st) and 2^(nd) pass spun workpieces(SP1 and SP2)mainly consisted of B2+retainedα2phases.After two passes spinning,the B2 phase texture changed from<111>//ND of as-received alloy to be<001>//ND.The ultimate tensile stress(UTS)of SP1 and SP2 was increased to 1163 MPa and 932 MPa,respectively,compared with 782 MPa of as-received alloy at 650℃.Also,the yield stress anomaly(YSA)occurred in SP1 and SP2 because{110}<111>and{112}<111>cross slip systems of B2 phase were difficult to slip at or below room temperature(RT),but they became active at 650℃ and above.As an essential step for increasing the spinnability of multi-pass spinning process of the Ti_(2)AlNb alloy,the H3heat treatment scheme,i.e.960℃/2 h+850℃/12 h,was carried out between two successive passes to increase the hot workability,by which the ductility of the heat treated as-spun workpieces with the microstructure of B2+primary O+acicular secondary O+high amount spheroidizedα2phases reached 72.1%at 900℃.After being subject to the H1 heat treatment scheme,i.e.960℃-2 h,the spun workpieces with the microstructure of B2+primary O+intergranular primaryα2phases achieved an optimized comprehensive mechanical properties both at room temperature and 650℃,which should be chosen as the post-spinning heat treatment process for the service requirement.
基金the financial support from the National Natural Science Foundation of China(Nos.21871026,21971224)Research Found of East China University of Technology(Nos.DHBK2019265,DHBK2019267,DHBK2019264)。
文摘A versatile heteropoly acid(H_(3)PMo_(12)O_(40))-catalyzed coupling of diarylmethanols with epoxides was established for the synthesis of polyaryl-substituted aldehydes.Furthermore,the catalytic system was also suitable for the reaction of diarylmethanols and diols/aldehydes.The application of such an earthabundant,readily accessible,and nontoxic catalyst provides a green approach for the construction of polyaryl-substituted aldehydes.
基金supported by the National Natural Science Foundation of China under grant nos.61772091,61802035,61962006,61962038,U1802271,U2001212,and 62072311the Sichuan Science and Technology Program under grant nos.2021JDJQ0021 and 22ZDYF2680+7 种基金the CCF‐Huawei Database System Innovation Research Plan under grant no.CCF‐HuaweiDBIR2020004ADigital Media Art,Key Laboratory of Sichuan Province,Sichuan Conservatory of Music,Chengdu,China under grant no.21DMAKL02the Chengdu Major Science and Technology Innovation Project under grant no.2021‐YF08‐00156‐GXthe Chengdu Technology Innovation and Research and Development Project under grant no.2021‐YF05‐00491‐SNthe Natural Science Foundation of Guangxi under grant no.2018GXNSFDA138005the Guangdong Basic and Applied Basic Research Foundation under grant no.2020B1515120028the Science and Technology Innovation Seedling Project of Sichuan Province under grant no 2021006the College Student Innovation and Entrepreneurship Training Program of Chengdu University of Information Technology under grant nos.202110621179 and 202110621186.
文摘An excellent cardinality estimation can make the query optimiser produce a good execution plan.Although there are some studies on cardinality estimation,the prediction results of existing cardinality estimators are inaccurate and the query efficiency cannot be guaranteed as well.In particular,they are difficult to accurately obtain the complex relationships between multiple tables in complex database systems.When dealing with complex queries,the existing cardinality estimators cannot achieve good results.In this study,a novel cardinality estimator is proposed.It uses the core techniques with the BiLSTM network structure and adds the attention mechanism.First,the columns involved in the query statements in the training set are sampled and compressed into bitmaps.Then,the Word2vec model is used to embed the word vectors about the query statements.Finally,the BiLSTM network and attention mechanism are employed to deal with word vectors.The proposed model takes into consideration not only the correlation between tables but also the processing of complex predicates.Extensive experiments and the evaluation of BiLSTM-Attention Cardinality Estimator(BACE)on the IMDB datasets are conducted.The results show that the deep learning model can significantly improve the quality of cardinality estimation,which is a vital role in query optimisation for complex databases.
基金supported by the National Natural Science Foundation of China(Nos.22071045 and 22001034)Excellent Youth Science Fund Project of Henan Province(No.202300410042)+1 种基金the Open Fund of the Jiangxi Province Key Laboratory of Synthetic Chemistry(No.JXSC202008)the start-up fund for Distinguished Professor of Henan University。
文摘We present the synthesis,characterization and photoluminescence properties of uranium-containing selenotungstate,[(UO_(2))_(3)(SeO_(3))_(3)Na_(5)(H_(2)O)_(6)(SeW_(6)O_(21))(SeW_(9)O_(33))_(3)]^(21–),which was isolated by a one-pot reaction of uranium nitrate with sodium tungstate and sodium selenite in a pH 5.2 aqueous solution at 90°C.In this study,the effect of the introduction of lone-electron pair containing heteroatoms on the structure is demonstrated,a three-layered heterometallic{Se_(3)U_(3)Na_(5)}cluster is encapsulated by two different anionic building block units:three trivacant Keggin{B-α-Se W_(9)O_(33)}and one Anderson{SeW_(6)O_(21)}.To our knowledge,the{Se_(3)U_(3)Na_(5)}cluster has never been observed in the polyoxometalate chemistry.The solidstate photoluminescence properties and lifetime decay behaviours of the title compound(1)have been measured at room temperature,and the photoluminescence spectrum displays the characteristic emission bands of corresponding uranyl cations.In addition,the photoluminescence quantum yield of 1 is 72%,which is almost three times that of starting material UO_(2)(NO_(3))_(2)·6H_(2)O(27%).By using this strategy,we envision that an increasing number of assemblies with‘open’clusters may be designed and obtained,in which the exposed oxygen atoms show strong affinity towards metal ions,providing new opportunities to generate bigger clusters or to tune existing properties.
基金supported by the National Natural Science Foundation of China(Nos.22071045,22001034)Excellent Youth Science Fund Project of Henan Province(No.202300410042)+1 种基金the Open Fund of the Jiangxi Province Key Laboratory of Synthetic Chemistry(No.JXSC202008)the start-up fund of Henan University。
文摘Two novel uranium-containing selenotungstates Na_(3)[H_(19)(UO_(2))_(2)(μ_(2)-O)(Se_(2)W_(14)O_(52))_(2)]·41 H_(2)O(U_(2))and(NH_(4))_(10)[H_(4)(SeO)_(2)(UO_(2))_(2)(H_(2)O)_(2)(H_(2)Se_(2)W_(14)O_(52))(Se_(2)W_(14)O_(52))]·66 H_(2)O(Se_(2)U_(2))based on the{Se_(2)W_(14)O_(52)}unit were successfully prepared and fully characterized.To our knowledge,the uranium is firstly introduced into the selenotungstates.Moreover,it is notable that U_(2)exhibits excellent Lewis acid-base catalytic activities in the condensation cyclization of sulfonyl hydrazides with diketones to synthesize polysubstituted pyrazoles.All the desired products were obtained in moderate to good yields(up to 99%).
基金supported by the National Natu-ral Science Foundation of China(Nos.21871125,21871026 and 22001034)the Natural Science Foundation of Shandong Province,China(Nos.ZR2019MB043 and ZR2019QB022)the Construction Project of Quality Curriculum for Postgraduate Education of Shandong Province(No.SDYKC19057).
文摘Three imidazole-modified Ag-polyoxovanadates frameworks(APFs)with a controllable molar ratio of Ag+to polyoxovanadates(POVs)[Ag(IM)_(2)]_(2)V_(4)O_(12)·2Ag(IM)_(2)(APF-1),[Ag_(2)(1-eIM)_(4)]_(2)[Ag(1-eIM)_(2)]_(3)·2Ag(1-eIM)_(2)·3(1-HeIM)[V_(10)O_(28)]_(2)(APF-2)and[Ag(1-pIM)_(2)]_(3)[HV_(10)O_(28)]·2Ag(1-pIM)_(2)·2H_(2)O(APF-3)(IM=imida-zole;1-eIM=1-ethylimidazole and 1-pIM=1-propylimidazole)have been successfully achieved by self-assembly of POVs,Ag+cations,and three different imidazole derivatives.Interestingly,the molar ratios of Ag+to POVs vary from 4:1,4.5:1 to 5:1 by changing the vanadium resources and imidazole deriva-tives.Notably,the coordination environment of Ag+cations and the structure of POVs in the APFs are also different.Specifically,for APF-1,the four Ag atoms adopt three-coordinated and four-coordinated geometries,respectively,and Ag-imidazole complexes and[V_(4)O 1_(2)]_(4)−cluster form the one-dimensional polymeric chains.While Ag atoms in APF-2 and APF-3 exhibit two-,four-and five-coordinated geome-tries for APF-2,four-,five-and six-coordinated geometries for APF-3,respectively.These Ag+cations and decavanadate clusters are assembled into the 2D supramolecular structure through the Ag-O bonds and Ag…Ag argentophilic interaction.Remarkably,thus-obtained APF-2 can serve as powerful efficient hetero-geneous catalyst for construction of C–N bond and detoxification of simulant sulfur mustard(yields up to 99%),which enable successful recycling for three cycles with remained catalytic activities and structure stability.
基金financially supported by the National Natural Science Foundation of China (Nos. 22001034 and 21804019)the Open Fund of the Jiangxi Province Key Laboratory of Synthetic Chemistry (No. JXSC202008)the Research Found of East China University of Technology (Nos. DHBK2019264, DHBK2019265 and DHBK2019267)。
文摘A simple and efficient method for the synthesis of pyrazoles through a silicotungstic acid (H_(4)SiW_(12)O_(40))-catalyzed cyclization of epoxides/aldehydes and sulfonyl hydrazides has been developed. Various epoxides/aldehydes were smoothly reacted with sulfonyl hydrazides to furnish regioselectivity 3,4-disubstituted 1H-pyrazoles. The application of such an earth-abundant, readily accessible, and nontoxic catalyst provides a green approach for the construction of 3,4-disubstituted 1H-pyrazoles. A plausible reaction mechanism has been proposed on the basis of control experiments, GC-MS and DFT calculations.
文摘In order to improve the impactor performance, the dynamic performance of gas-liquid united hydraulic hammer should be optimized. Based on the analysis of the operating principle for the hydraulic impactor, one simulation model of gas-liquid united hydraulic impactor was built with AMESim software. By setting different simulation parameters, curves of displacement, velocity, acceleration and cavity pressure were obtained under different working conditions. The key component can be obtained by the analysis of activity index. The whole simulation results provide a reliable basis for component selection and parameter optimization of hydraulic impactor.
文摘The structure and operational principle on a new type reversing valve of hydraulic breaker are introduced. The nonlinear mathematic model and simulation model of the new type reversing valve are built. The dynamic simulation research of the new type reversing valve is conducted. The effects of the system parameters on the working performance are researched systematically and deeply. The regular understanding on the motion of the reversing valve is obtained, which provides theoretical basis for the innovation and manufacturing of a new generation of hydraulic breaker reversing valve.
文摘In order to improve the impact performance, the structure of hydraulic hammer should be optimized. In this paper, the ranges of eight vital structure parameters of piston and reversing valve system of hydraulic hammer were selected firstly;and then found the best value of different parameters under experiments with the method of computer optimization and the parametric analysis method provided by ADAMS software. These methods worked and the best design values of parameters of hydraulic hammer were obtained. At last, the optimal impact energy of virtual prototype of hydraulic breaking hammer was calculated and compared with the original impact performance. The results reveal that impact performance of hydraulic hammer has been improved significantly.
