A comprehensive safety evaluation system taking the most influential factors into account has been developed to evaluate the reliability of hydraulic metal structures. Applying the techniques of AI and DB, the idea of...A comprehensive safety evaluation system taking the most influential factors into account has been developed to evaluate the reliability of hydraulic metal structures. Applying the techniques of AI and DB, the idea of a one-machine and three-base system is proposed. The framework of the three-base system has been designed and the structural framework constructed in turn. A practical example is given to illustrate the process of using this system and it can be used for comparison and analysis purposes. The key technology of the system is its ability to reorganize and improve the expert system＇s knowledge base by establishing the expert system. This system utilizes the computer technology inference process, making safety evaluation conclusions more reasonable and applicable to the actual situation. The system is not only advanced, but also feasible, reliable, artificially intelligent, and has the capacity to constantly grow.展开更多
To compensate for the shortcomings of quasi-static law in anti-fatigue analysis of foundry crane metal structures,the fatigue life evaluation method of foundry crane metal structure considering load dynamic response a...To compensate for the shortcomings of quasi-static law in anti-fatigue analysis of foundry crane metal structures,the fatigue life evaluation method of foundry crane metal structure considering load dynamic response and crack closure effect is proposed.In line with the theory of mechanical vibration,a dynamic model of crane structure during the working cycle is constructed,and dynamic coefficients under diverse actions are analysed.Calculation models of the internal force dynamic change process of dangerous cross-sections and a simulation model of first principal stress-time history are established by using the steel structure design criteria,which is utilised to extract the change of first principal stress of danger points over time.Then,the double-parameter stress spectrum is obtained by the rain flow counting method.The fatigue life calculation formula is corrected by introducing a crack closure parameter that can be calculated by the stress ratio and the effective stress ratio.Under the finite element model imported into Msc.Patran,crack propagation analysis is performed by the growth method in the fatigue integration module Msc.Fatigue.Taking the metal structure of a 100/40t-28.5m foundry crane with track offset as an example,the accuracy of calculation results and the feasibility and applicability of the proposed method are verified by theoretical calculation and finite element simulation,which provide a theoretical basis for improvement of the fatigue resistance design of foundry cranes.展开更多
In conjunction with association rules for data mining, the connections between testing indices and strong and weak association rules were determined, and new derivative rules were obtained by further reasoning. Associ...In conjunction with association rules for data mining, the connections between testing indices and strong and weak association rules were determined, and new derivative rules were obtained by further reasoning. Association rules were used to analyze correlation and check consistency between indices. This study shows that the judgment obtained by weak association rules or non-association rules is more accurate and more credible than that obtained by strong association rules. When the testing grades of two indices in the weak association rules are inconsistent, the testing grades of indices are more likely to be erroneous, and the mistakes are often caused by human factors. Clustering data mining technology was used to analyze the reliability of a diagnosis, or to perform health diagnosis directly. Analysis showed that the clustering results are related to the indices selected, and that if the indices selected are more significant, the characteristics of clustering results are also more significant, and the analysis or diagnosis is more credible. The indices and diagnosis analysis function produced by this study provide a necessary theoretical foundation and new ideas for the development of hydraulic metal structure health diagnosis technology.展开更多
The dynamical process of charge injection from metal electrode to a nondegenerate polymer in a metal/polythiophene （PT）/metal structure has been investigated by using a nonadiabatic dynamic approach. It is found tha...The dynamical process of charge injection from metal electrode to a nondegenerate polymer in a metal/polythiophene （PT）/metal structure has been investigated by using a nonadiabatic dynamic approach. It is found that the injected charges form wave packets due to the strong electron-lattice interaction in PT. We demonstrate that the dynamical formation of the wave packet sensitively depends on the strength of applied voltage, the electric field, and the contact between PT and electrode. At a strength of the electric field more than 3.0 × 10^4 V/cm, the carriers can be ejected from the PT into the right electrode. At an electric field more than 3.0 × 10^5 V/cm, the wave packet cannot form while it moves rapidly to the right PT/metal interface. It is shown that the ejected quantity of charge is noninteger.展开更多
To address the incompatibility between high environmental adaptability and deep subwavelength characteristics in conventional local resonance metamaterials,and overcome the deficiencies in the stability of existing ac...To address the incompatibility between high environmental adaptability and deep subwavelength characteristics in conventional local resonance metamaterials,and overcome the deficiencies in the stability of existing active control techniques for band gaps,this paper proposes a design method of pure metal vibration damping metamaterial with continuously tunable stiffness for wideband elastic wave absorption.We design a dual-helix narrow-slit pure metal metamaterial unit,which possesses the triple advantage of high spatial compactness,low stiffness characteristics,and high structural stability,enabling the opening of elastic flexural band gaps in the low-frequency range.Similar to the principle of a sliding rheostat,the introduction of continuously sliding plug-ins into the helical slits enables the continuous variation of the stiffness of the metamaterial unit,achieving a continuously tunable band gap effect.This successfully extends the effective band gap by more than ten times.The experimental results indicate that this metamaterial unit can be used as an additional vibration absorber to absorb the low-frequency vibration energy effectively.Furthermore,it advances the metamaterial absorbers from a purely passive narrowband design to a wideband tunable one.The pure metal double-helix metamaterials retain the subwavelength properties of metamaterials and are suitable for deployment in harsh environments.Simultaneously,by adjusting its stiffness,it substantially broadens the effective band gap range,presenting promising potential applications in various mechanical equipment operating under adverse conditions.展开更多
Uncertainties in parameters such as materials, loading, and geometry are inevitable in designing metallic structures for cranes. When considering these uncertainty factors, reliability-based design optimization （RBDO...Uncertainties in parameters such as materials, loading, and geometry are inevitable in designing metallic structures for cranes. When considering these uncertainty factors, reliability-based design optimization （RBDO） offers a more reasonable design approach. However, existing RBDO methods for crane metallic structures are prone to low convergence speed and high computational cost. A unilevel RBDO method, combining a discrete imperialist competitive algorithm with an inverse reliabil- ity strategy based on the performance measure approach, is developed. Application of the imperialist competitive algorithm at the optimization level significantly improves the convergence speed of this RBDO method. At the reli- ability analysis level, the inverse reliability strategy is used to determine the feasibility of each probabilistic constraint at each design point by calculating its a-percentile per- formance, thereby avoiding convergence failure, calcula- tion error, and disproportionate computational effort encountered using conventional moment and simulation methods. Application of the RBDO method to an actual crane structure shows that the developed RBDO realizes a design with the best tradeoff between economy and safety together with about one-third of the convergence speed and the computational cost of the existing method. This paper provides a scientific and effective design approach for the design of metallic structures of cranes.展开更多
The molecular structures of metal precursors in the impregnating solution were designed so as to prepare efficient Ni Mo/Al_2O_3 hydrodesulfurization(HDS) catalysts. At first, five typical impregnating solutions were ...The molecular structures of metal precursors in the impregnating solution were designed so as to prepare efficient Ni Mo/Al_2O_3 hydrodesulfurization(HDS) catalysts. At first, five typical impregnating solutions were designed; the existing metal precursors, such as [Mo4(citrate)2O11]^(4-)-like, [P2Mo18O62]^(6-)-like and [P2Mo5O23]^(6-)-like species in the solutions were confirmed by laser Raman spectroscopy(LRS). The UV-Vis spectra results indicated that the solutions containing both phosphoric acid and citric acid could change the existing form of nickel species. Five corresponding Ni Mo/Al_2O_3 catalysts were prepared by the incipient wetness impregnation method. The LRS analysis results of dried catalysts showed that the above metal precursors could be partly retained on alumina support after impregnation and drying, although the interface reaction between different metal precursors and alumina support unavoidably took place. Then the catalysts were sulfided and characterized by N2 physisorption, TEM and XPS analyses. The results showed that different metal precursors in impregnating solution could mainly result in the difference in both the morphology of(Ni)Mo S2 slabs and the promoting effect of Ni species. The catalyst prepared mainly with [P2Mo5O23]^(6-)-like species used as precursors exhibited worse dispersion of(Ni)Mo S2 slabs and lower ratio of Ni–Mo–S active phases than the one with [Mo4(citrate)2O11]^(4-)-like species. Promisingly, the catalyst prepared with co-existing [Mo4(citrate)2O11]^(4-)-like, [P2Mo18O62]^(6-)-like and [P2Mo5O23]^(6-)-like species showed better hydrodesulfurization activity for 4,6-DMDBT thanks to its more well-dispersed Ni–Mo–S active phases.展开更多
Bulk metallic glasses with up to 72 mm critical section thickness have been obtained by conventional casting techniques and the properties of these materials, particularly the mechanical and magnetic properties have b...Bulk metallic glasses with up to 72 mm critical section thickness have been obtained by conventional casting techniques and the properties of these materials, particularly the mechanical and magnetic properties have been studied. These materials have been demonstrated to have novel properties which are fundamentally different from their crystalline counterparts. The recent status of research and development in formation, structure and properties of bulk metallic glasses is reviewed. The techniques to produce such bulk glasses are summarized and the glass forming ability and the critical cooling rate of these materials are discussed. Further consideration of the development and application of this new class of materiaIs will be proposed.展开更多
In this study, we designed and fabricated optical materials consisting of alternating ITO and Ag layers. This approach is considered to be a promising way to obtain a light-weight, ultrathin and transparent shielding ...In this study, we designed and fabricated optical materials consisting of alternating ITO and Ag layers. This approach is considered to be a promising way to obtain a light-weight, ultrathin and transparent shielding medium, which not only transmits visible light but also inhibits the transmission of microwaves, despite the fact that the total thickness of the Ag film is much larger than the skin depth in the visible range and less than that in the microwave region. Theoretical results suggest that a high dielectric/metal thickness ratio can enhance the broadband and improve the transmittance in the optical range. Accordingly, the central wavelength was found to be red-shifted with increasing dielectric/metal thickness ratio. A physical mechanism behind the controlling transmission of visible light is also proposed. Meanwhile, the electromagnetic shielding effectiveness of the prepared structures was found to exceed 40 dB in the range from 0.1 GHz to 18 GHz, even reaching up to 70 dB at 0.1 GHz, which is far higher than that of a single ITO film of the same thickness.展开更多
With transition metal complex, a discrete cuprous iodide compound, namely, [Ni（phen）3]2Cu6I10（1, phen = 1,10-phenanthroline） has been solvothermally synthesized and structurally characterized. Single-crystal X-ray...With transition metal complex, a discrete cuprous iodide compound, namely, [Ni（phen）3]2Cu6I10（1, phen = 1,10-phenanthroline） has been solvothermally synthesized and structurally characterized. Single-crystal X-ray diffraction studies revealed that compound 1 crystallizes in triclinic space group P1（No. 2） with a = 11.2694（2）, b = 12.3699（3）, c = 15.0387（3） ？, α = 102.840（2）, β = 105.215（2）, γ = 96.388（2）°, V = 1940.04（7） ^3, Z = 1, Dc = 2.438 g·cm^-3, F（000） = 1324, R = 0.0256 and w R = 0.0555（I 〉 2σ（I））. Compound 1 features a discrete anionic moiety of [Cu6I10]^4- charge-balanced by two metal complexes of [Ni（phen）3]2＋. The optical absorption edge of compound 1 was estimated to be 2.24 eV. Interestingly, nearly 95% of contaminant（crystal violet aqueous solution（CV）, 50 m L, 1.0 × 10^-5 M） could be decolorized after exposure to visible light within 30 min, illustrating an impressive photocatalytic activity of compound 1. The thermal stability of 1 has also been studied.展开更多
Bulk metallic glass Zr_52.5Ni_14.6Al_10Cu_17.9Ti_5 was prepared by melt injection casting method. Its glass transition and crystallization temperatures were determined by differential scanning calorimetry (DSC) to be ...Bulk metallic glass Zr_52.5Ni_14.6Al_10Cu_17.9Ti_5 was prepared by melt injection casting method. Its glass transition and crystallization temperatures were determined by differential scanning calorimetry (DSC) to be 631 K and 710 K respectively. By analysis of X-ray diffractometry (XRD) and transmission electron microscopy (TEM ), the predominant crystallized phase of Zr_2Ni0.67O0.33 distributed on glass state matrix was detected after annealing at 673 K for 600 s. The transformation to Zr_2Ni_0.67O_0.33 and a small amount of ZrAl and Zr_2Cu took place after annealing for 600 s at temperature from 703 K to 723 K. With increasing annealing temperature from 753 K to 823 K, the amounts of ZrAl and Zr_2Cu increased, but the size of the crystals did not significantly change. The transformation to Zr_2Ni_0.67O_0.33 is interface-controlled, but is diffusion-controlled to Zr_2Cu and ZrAl. With increasing annealing temperature up to 200 K above T_x, the nanometer grains became very fine because of the increase of nucleation rate for Zr_2Cu and ZrAl.展开更多
The crystal structure of the title complex salt has been determined by single-crystal X-ray structure analysis. The crystal data are as follows; Monoclinic, P21/c, a=15.6480(10)A,b=16.7870(10)A, c=10.347(2)A, β=90.79...The crystal structure of the title complex salt has been determined by single-crystal X-ray structure analysis. The crystal data are as follows; Monoclinic, P21/c, a=15.6480(10)A,b=16.7870(10)A, c=10.347(2)A, β=90.790(10), V=2717.7(6)A3, Z=3, and R=0.0333 for 4789 unique reflections. The complex anion has a pseudo-octahedral structure distorted more than the CrⅢand CoⅢ analogs, in which cach iminodiacetato ligand (ida2-) is coordinated in a facial fashion with the two N atoms in a cis configuration, resulting in an unsyin-fac structure.展开更多
Nanometer-sized metal clusters were prepared inside single crystalline MgO films by vacuum co-deposition of metals and MgO. The atomic structure was studied by high-resolution electron microscopy (HREM) and nm-area el...Nanometer-sized metal clusters were prepared inside single crystalline MgO films by vacuum co-deposition of metals and MgO. The atomic structure was studied by high-resolution electron microscopy (HREM) and nm-area electron diffraction. The size of the clusters is ranging from 1 nm to 3 nm without those larger than 5 nm, and most of them have definite epitaxial orientations with the MgO matrix films. The character of the composite films is very much useful for the studies of various kinds of physical properties with anisotroPy. The physical properties such as electric transport, magnetic, optical absorption, sintering and catalytic ones were thus measured on the same samples analyzed by HREM by using high sensitivity apparatus with interest of clarifying the retationship between the atomic structure and physical properties展开更多
The anisotropy of magnetostatic surface wave （MSSW） propagating in finite width YIG /dielectric/metal layered structure is analyzed. This problem is solved by finding the rigorous solution of each layer from Maxwell...The anisotropy of magnetostatic surface wave （MSSW） propagating in finite width YIG /dielectric/metal layered structure is analyzed. This problem is solved by finding the rigorous solution of each layer from Maxwell equation and the appropriate transmission Green＇s function matrix G. From the relationship of Green＇s function matrixes of dielectric layer and ferrite layer, the dispersion equation is obtained. The MSSW filter is designed to verify the dispersion characteristics. The experiment results are in good agreement with the calculating data from the model.展开更多
The activity coefficient of Al in molten Cu decreases with the increasing of electric current applied to the liquid alloy of Cu-0.2wt%Al. To investigate the mechanism, the quenching experimental results of the liquid...The activity coefficient of Al in molten Cu decreases with the increasing of electric current applied to the liquid alloy of Cu-0.2wt%Al. To investigate the mechanism, the quenching experimental results of the liquid Al-Cu alloy show that there is a re- markable change in structure, in which the solute congregates along the current direction especially for DC current. The mechanism of the activity coefficient change of Al in molten Cu-0.2wt%Al alloy treated by electrical field was discussed. Further, the results also provide an evidence for the short-range-ordered liquid metal.展开更多
Due to their rapid power delivery,fast charging,and long cycle life,supercapacitors have become an important energy storage technology recently.However,to meet the continuously increasing demands in the fields of port...Due to their rapid power delivery,fast charging,and long cycle life,supercapacitors have become an important energy storage technology recently.However,to meet the continuously increasing demands in the fields of portable electronics,transportation,and future robotic technologies,supercapacitors with higher energy densities without sacrificing high power densities and cycle stabilities are still challenged.Transition metal compounds(TMCs)possessing high theoretical capacitance are always used as electrode materials to improve the energy densities of supercapacitors.However,the power densities and cycle lives of such TMCs-based electrodes are still inferior due to their low intrinsic conductivity and large volume expansion during the charge/discharge process,which greatly impede their large-scale applications.Most recently,the ideal integrating of TMCs and conductive carbon skeletons is considered as an effective solution to solve the above challenges.Herein,we summarize the recent developments of TMCs/carbon hybrid electrodes which exhibit both high energy/power densities from the aspects of structural design strategies,including conductive carbon skeleton,interface engineering,and electronic structure.Furthermore,the remaining challenges and future perspectives are also highlighted so as to provide strategies for the high energy/power TMCs/carbon-based supercapacitors.展开更多
This review paper aims at analysing the state of the art for partial oxidation and oxidative dehydrogenation（ODH） reactions of lower alkanes C–Cinto olefins and oxygenated products（aldehydes, anhydrides,carboxylic...This review paper aims at analysing the state of the art for partial oxidation and oxidative dehydrogenation（ODH） reactions of lower alkanes C–Cinto olefins and oxygenated products（aldehydes, anhydrides,carboxylic acids） on metal oxide catalysts with cations of variable oxidation state, such as Mo and V in particular. Key parameters to be met by the catalysts, such as their redox properties, their structural aspects, active sites composed of ensembles of atoms isolated one from the others, mechanisms of reactions, are discussed. Main features of the different reactions of C–Calkanes and catalysts are analysed and their generalisation for determining more active and more selective catalysts is attempted. Prospective views for the future of the domain are proposed.展开更多
Atomically dispersed metal-nitrogen sites-anchored carbon materials have been developed as effective catalysts for CO2 electroreduction(CO2 ER),but they still suffer from the imprecisely control of type and coordinati...Atomically dispersed metal-nitrogen sites-anchored carbon materials have been developed as effective catalysts for CO2 electroreduction(CO2 ER),but they still suffer from the imprecisely control of type and coordination number of N atoms bonded with central metal.Herein,we develop a family of single metal atom bonded by N atoms anchored on carbons(SAs-M-N-C,M=Fe,Co,Ni,Cu)for CO2 ER,which composed of accurate pyrrole-type M-N4 structures with isolated metal atom coordinated by four pyrrolic N atoms.Benefitting from atomically coordinated environment and specific selectivity of M-N4 centers,SAs-Ni-N-C exhibits superior CO2 ER performance with onset potential of-0.3 V,CO Faradaic efficiency(F.E.) of 98.5%at-0.7 V,along with low Tafel slope of 115 mV dec-1 and superior stability of 50 h,exceeding all the previously reported M-N-C electrocatalysts for CO2-to-CO conversion.Experimental results manifest that the different intrinsic activities of M-N4 structures in SAs-M-N-C result in the corresponding sequence of Ni> Fe> Cu> Co for CO2 ER performance.An integrated Zn-CO2 battery with Zn foil and SAs-Ni-N-C is constructed to simultaneously achieve CO2-to-CO conversion and electric energy output,which delivers a peak power density of 1.4 mW cm-2 and maximum CO F.E.of 93.3%.展开更多
A novel zinc complex [Zn（BIB）（bdc）]n（1, BIB = 1,3-bis（imidazol-1-yl）benzene, bdc = 1,3-benzenedicarboxylate） has been synthesized in solvothermal conditions. The title complex was characterized by elemental an...A novel zinc complex [Zn（BIB）（bdc）]n（1, BIB = 1,3-bis（imidazol-1-yl）benzene, bdc = 1,3-benzenedicarboxylate） has been synthesized in solvothermal conditions. The title complex was characterized by elemental analysis, IR spectra, thermal analysis, single-crystal and powder X-ray diffraction. The result proved that the alliance of BIB and aromatic carboxylic acids is good for the diversity of getatable structure. Complex 1 crystallizes in the monoclinic system of P2/c space group with a = 11.5591（10）, b = 9.6239（8）, c = 33.727（3）A, β = 103.816（3）°, V = 3643.4（5） A^3, Z = 8, μ = 1.385 mm^-1, F（000） = 1792, Dc = 1.603 g/cm^3 and Mr = 439.72 g/mol. Additionally, luminescent properties of complex 1 are also investigated and it shows good fluorescence.展开更多
The hydrothermal reaction of 5-methoxyisophthalic acid（MeO-H2ip）, 1,3-bis（2-methylimidazol-1-yl）propane（bmip） and Zn（NO3）2·6H2O in the presence of NaOCH3 gave rise to a three-dimensional（3-D） metal-orga...The hydrothermal reaction of 5-methoxyisophthalic acid（MeO-H2ip）, 1,3-bis（2-methylimidazol-1-yl）propane（bmip） and Zn（NO3）2·6H2O in the presence of NaOCH3 gave rise to a three-dimensional（3-D） metal-organic framework containing octanuclear Zn（II） units, [Zn4（MeO-ip）3（OH）2（bmip）]n. Single-crystal X-ray diffraction analysis reveals that the complex crystallizes in the triclinic space group P1 with a = 11.348（3）, b = 14.163（4）, c = 15.088（4） , α = 108.537（2）, β = 106.542（2）, γ = 103.106（1）o, V = 2065.4（9） -3, Z = 2, Mr = 334.62, Dc = 1.740 g·cm-（-3）, μ = 2.375 mm-（-1）, S = 1.015, F（000） = 1096, the final R = 0.0272 and w R = 0.0715 for 8929 observed reflections（I 〉 2σ（I））. The complex is thermally stable up to 370 oC, and exhibits photoluminescent emission at 450 nm on 350 nm excitation.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 50539010)
文摘A comprehensive safety evaluation system taking the most influential factors into account has been developed to evaluate the reliability of hydraulic metal structures. Applying the techniques of AI and DB, the idea of a one-machine and three-base system is proposed. The framework of the three-base system has been designed and the structural framework constructed in turn. A practical example is given to illustrate the process of using this system and it can be used for comparison and analysis purposes. The key technology of the system is its ability to reorganize and improve the expert system＇s knowledge base by establishing the expert system. This system utilizes the computer technology inference process, making safety evaluation conclusions more reasonable and applicable to the actual situation. The system is not only advanced, but also feasible, reliable, artificially intelligent, and has the capacity to constantly grow.
基金the National Science-technology Support Projects for the 13th Five-year Plan(2017YFC0805703-4).
文摘To compensate for the shortcomings of quasi-static law in anti-fatigue analysis of foundry crane metal structures,the fatigue life evaluation method of foundry crane metal structure considering load dynamic response and crack closure effect is proposed.In line with the theory of mechanical vibration,a dynamic model of crane structure during the working cycle is constructed,and dynamic coefficients under diverse actions are analysed.Calculation models of the internal force dynamic change process of dangerous cross-sections and a simulation model of first principal stress-time history are established by using the steel structure design criteria,which is utilised to extract the change of first principal stress of danger points over time.Then,the double-parameter stress spectrum is obtained by the rain flow counting method.The fatigue life calculation formula is corrected by introducing a crack closure parameter that can be calculated by the stress ratio and the effective stress ratio.Under the finite element model imported into Msc.Patran,crack propagation analysis is performed by the growth method in the fatigue integration module Msc.Fatigue.Taking the metal structure of a 100/40t-28.5m foundry crane with track offset as an example,the accuracy of calculation results and the feasibility and applicability of the proposed method are verified by theoretical calculation and finite element simulation,which provide a theoretical basis for improvement of the fatigue resistance design of foundry cranes.
基金supported by the Key Program of the National Natural Science Foundation of China(Grant No.50539010)the Special Fund for Public Welfare Industry of the Ministry of Water Resources of China(Grant No.200801019)
文摘In conjunction with association rules for data mining, the connections between testing indices and strong and weak association rules were determined, and new derivative rules were obtained by further reasoning. Association rules were used to analyze correlation and check consistency between indices. This study shows that the judgment obtained by weak association rules or non-association rules is more accurate and more credible than that obtained by strong association rules. When the testing grades of two indices in the weak association rules are inconsistent, the testing grades of indices are more likely to be erroneous, and the mistakes are often caused by human factors. Clustering data mining technology was used to analyze the reliability of a diagnosis, or to perform health diagnosis directly. Analysis showed that the clustering results are related to the indices selected, and that if the indices selected are more significant, the characteristics of clustering results are also more significant, and the analysis or diagnosis is more credible. The indices and diagnosis analysis function produced by this study provide a necessary theoretical foundation and new ideas for the development of hydraulic metal structure health diagnosis technology.
基金Project supported by the State Key Program of National Natural Science of China (Grant Nos 10474056 and 10574082)the Natural Science Foundation of Shandong Province (Grant No Z2005A01)
文摘The dynamical process of charge injection from metal electrode to a nondegenerate polymer in a metal/polythiophene （PT）/metal structure has been investigated by using a nonadiabatic dynamic approach. It is found that the injected charges form wave packets due to the strong electron-lattice interaction in PT. We demonstrate that the dynamical formation of the wave packet sensitively depends on the strength of applied voltage, the electric field, and the contact between PT and electrode. At a strength of the electric field more than 3.0 × 10^4 V/cm, the carriers can be ejected from the PT into the right electrode. At an electric field more than 3.0 × 10^5 V/cm, the wave packet cannot form while it moves rapidly to the right PT/metal interface. It is shown that the ejected quantity of charge is noninteger.
基金supported by the National Natural Science Foundation of China(No.52250287)the Outstanding Youth Science Fund Project of Shaanxi Province of China(No.2024JC-JCQN-49)。
文摘To address the incompatibility between high environmental adaptability and deep subwavelength characteristics in conventional local resonance metamaterials,and overcome the deficiencies in the stability of existing active control techniques for band gaps,this paper proposes a design method of pure metal vibration damping metamaterial with continuously tunable stiffness for wideband elastic wave absorption.We design a dual-helix narrow-slit pure metal metamaterial unit,which possesses the triple advantage of high spatial compactness,low stiffness characteristics,and high structural stability,enabling the opening of elastic flexural band gaps in the low-frequency range.Similar to the principle of a sliding rheostat,the introduction of continuously sliding plug-ins into the helical slits enables the continuous variation of the stiffness of the metamaterial unit,achieving a continuously tunable band gap effect.This successfully extends the effective band gap by more than ten times.The experimental results indicate that this metamaterial unit can be used as an additional vibration absorber to absorb the low-frequency vibration energy effectively.Furthermore,it advances the metamaterial absorbers from a purely passive narrowband design to a wideband tunable one.The pure metal double-helix metamaterials retain the subwavelength properties of metamaterials and are suitable for deployment in harsh environments.Simultaneously,by adjusting its stiffness,it substantially broadens the effective band gap range,presenting promising potential applications in various mechanical equipment operating under adverse conditions.
基金Supported by National Natural Science Foundation of China(Grant No.51275329)
文摘Uncertainties in parameters such as materials, loading, and geometry are inevitable in designing metallic structures for cranes. When considering these uncertainty factors, reliability-based design optimization （RBDO） offers a more reasonable design approach. However, existing RBDO methods for crane metallic structures are prone to low convergence speed and high computational cost. A unilevel RBDO method, combining a discrete imperialist competitive algorithm with an inverse reliabil- ity strategy based on the performance measure approach, is developed. Application of the imperialist competitive algorithm at the optimization level significantly improves the convergence speed of this RBDO method. At the reli- ability analysis level, the inverse reliability strategy is used to determine the feasibility of each probabilistic constraint at each design point by calculating its a-percentile per- formance, thereby avoiding convergence failure, calcula- tion error, and disproportionate computational effort encountered using conventional moment and simulation methods. Application of the RBDO method to an actual crane structure shows that the developed RBDO realizes a design with the best tradeoff between economy and safety together with about one-third of the convergence speed and the computational cost of the existing method. This paper provides a scientific and effective design approach for the design of metallic structures of cranes.
基金supported by the National Key Basic Research Program of China(973 Program,2012CB224802)the SINOPEC project(No.114013)
文摘The molecular structures of metal precursors in the impregnating solution were designed so as to prepare efficient Ni Mo/Al_2O_3 hydrodesulfurization(HDS) catalysts. At first, five typical impregnating solutions were designed; the existing metal precursors, such as [Mo4(citrate)2O11]^(4-)-like, [P2Mo18O62]^(6-)-like and [P2Mo5O23]^(6-)-like species in the solutions were confirmed by laser Raman spectroscopy(LRS). The UV-Vis spectra results indicated that the solutions containing both phosphoric acid and citric acid could change the existing form of nickel species. Five corresponding Ni Mo/Al_2O_3 catalysts were prepared by the incipient wetness impregnation method. The LRS analysis results of dried catalysts showed that the above metal precursors could be partly retained on alumina support after impregnation and drying, although the interface reaction between different metal precursors and alumina support unavoidably took place. Then the catalysts were sulfided and characterized by N2 physisorption, TEM and XPS analyses. The results showed that different metal precursors in impregnating solution could mainly result in the difference in both the morphology of(Ni)Mo S2 slabs and the promoting effect of Ni species. The catalyst prepared mainly with [P2Mo5O23]^(6-)-like species used as precursors exhibited worse dispersion of(Ni)Mo S2 slabs and lower ratio of Ni–Mo–S active phases than the one with [Mo4(citrate)2O11]^(4-)-like species. Promisingly, the catalyst prepared with co-existing [Mo4(citrate)2O11]^(4-)-like, [P2Mo18O62]^(6-)-like and [P2Mo5O23]^(6-)-like species showed better hydrodesulfurization activity for 4,6-DMDBT thanks to its more well-dispersed Ni–Mo–S active phases.
文摘Bulk metallic glasses with up to 72 mm critical section thickness have been obtained by conventional casting techniques and the properties of these materials, particularly the mechanical and magnetic properties have been studied. These materials have been demonstrated to have novel properties which are fundamentally different from their crystalline counterparts. The recent status of research and development in formation, structure and properties of bulk metallic glasses is reviewed. The techniques to produce such bulk glasses are summarized and the glass forming ability and the critical cooling rate of these materials are discussed. Further consideration of the development and application of this new class of materiaIs will be proposed.
基金Project supported by the International Science&Technology Cooperation Program of China(Grant No.2014DFR10020)the Science Foundation of Shanxi Province,China(Grant Nos.201701D121050 and 201701D121007)
文摘In this study, we designed and fabricated optical materials consisting of alternating ITO and Ag layers. This approach is considered to be a promising way to obtain a light-weight, ultrathin and transparent shielding medium, which not only transmits visible light but also inhibits the transmission of microwaves, despite the fact that the total thickness of the Ag film is much larger than the skin depth in the visible range and less than that in the microwave region. Theoretical results suggest that a high dielectric/metal thickness ratio can enhance the broadband and improve the transmittance in the optical range. Accordingly, the central wavelength was found to be red-shifted with increasing dielectric/metal thickness ratio. A physical mechanism behind the controlling transmission of visible light is also proposed. Meanwhile, the electromagnetic shielding effectiveness of the prepared structures was found to exceed 40 dB in the range from 0.1 GHz to 18 GHz, even reaching up to 70 dB at 0.1 GHz, which is far higher than that of a single ITO film of the same thickness.
基金Supported by the NNSFC(No.21373223)Chunmiao project of Haixi Institute of Chinese Academy of Sciences(CMZX-2014-001)
文摘With transition metal complex, a discrete cuprous iodide compound, namely, [Ni（phen）3]2Cu6I10（1, phen = 1,10-phenanthroline） has been solvothermally synthesized and structurally characterized. Single-crystal X-ray diffraction studies revealed that compound 1 crystallizes in triclinic space group P1（No. 2） with a = 11.2694（2）, b = 12.3699（3）, c = 15.0387（3） ？, α = 102.840（2）, β = 105.215（2）, γ = 96.388（2）°, V = 1940.04（7） ^3, Z = 1, Dc = 2.438 g·cm^-3, F（000） = 1324, R = 0.0256 and w R = 0.0555（I 〉 2σ（I））. Compound 1 features a discrete anionic moiety of [Cu6I10]^4- charge-balanced by two metal complexes of [Ni（phen）3]2＋. The optical absorption edge of compound 1 was estimated to be 2.24 eV. Interestingly, nearly 95% of contaminant（crystal violet aqueous solution（CV）, 50 m L, 1.0 × 10^-5 M） could be decolorized after exposure to visible light within 30 min, illustrating an impressive photocatalytic activity of compound 1. The thermal stability of 1 has also been studied.
文摘Bulk metallic glass Zr_52.5Ni_14.6Al_10Cu_17.9Ti_5 was prepared by melt injection casting method. Its glass transition and crystallization temperatures were determined by differential scanning calorimetry (DSC) to be 631 K and 710 K respectively. By analysis of X-ray diffractometry (XRD) and transmission electron microscopy (TEM ), the predominant crystallized phase of Zr_2Ni0.67O0.33 distributed on glass state matrix was detected after annealing at 673 K for 600 s. The transformation to Zr_2Ni_0.67O_0.33 and a small amount of ZrAl and Zr_2Cu took place after annealing for 600 s at temperature from 703 K to 723 K. With increasing annealing temperature from 753 K to 823 K, the amounts of ZrAl and Zr_2Cu increased, but the size of the crystals did not significantly change. The transformation to Zr_2Ni_0.67O_0.33 is interface-controlled, but is diffusion-controlled to Zr_2Cu and ZrAl. With increasing annealing temperature up to 200 K above T_x, the nanometer grains became very fine because of the increase of nucleation rate for Zr_2Cu and ZrAl.
文摘The crystal structure of the title complex salt has been determined by single-crystal X-ray structure analysis. The crystal data are as follows; Monoclinic, P21/c, a=15.6480(10)A,b=16.7870(10)A, c=10.347(2)A, β=90.790(10), V=2717.7(6)A3, Z=3, and R=0.0333 for 4789 unique reflections. The complex anion has a pseudo-octahedral structure distorted more than the CrⅢand CoⅢ analogs, in which cach iminodiacetato ligand (ida2-) is coordinated in a facial fashion with the two N atoms in a cis configuration, resulting in an unsyin-fac structure.
文摘Nanometer-sized metal clusters were prepared inside single crystalline MgO films by vacuum co-deposition of metals and MgO. The atomic structure was studied by high-resolution electron microscopy (HREM) and nm-area electron diffraction. The size of the clusters is ranging from 1 nm to 3 nm without those larger than 5 nm, and most of them have definite epitaxial orientations with the MgO matrix films. The character of the composite films is very much useful for the studies of various kinds of physical properties with anisotroPy. The physical properties such as electric transport, magnetic, optical absorption, sintering and catalytic ones were thus measured on the same samples analyzed by HREM by using high sensitivity apparatus with interest of clarifying the retationship between the atomic structure and physical properties
基金This work was supported by the National Basic Research Program of China (973) under Grant No. 2007CB31407the International S&T Cooperation Program of China under Grant No. 2006DFA53410.
文摘The anisotropy of magnetostatic surface wave （MSSW） propagating in finite width YIG /dielectric/metal layered structure is analyzed. This problem is solved by finding the rigorous solution of each layer from Maxwell equation and the appropriate transmission Green＇s function matrix G. From the relationship of Green＇s function matrixes of dielectric layer and ferrite layer, the dispersion equation is obtained. The MSSW filter is designed to verify the dispersion characteristics. The experiment results are in good agreement with the calculating data from the model.
基金This work was financially supported by the National Natural Science Foundation of China (No. 30160186)
文摘The activity coefficient of Al in molten Cu decreases with the increasing of electric current applied to the liquid alloy of Cu-0.2wt%Al. To investigate the mechanism, the quenching experimental results of the liquid Al-Cu alloy show that there is a re- markable change in structure, in which the solute congregates along the current direction especially for DC current. The mechanism of the activity coefficient change of Al in molten Cu-0.2wt%Al alloy treated by electrical field was discussed. Further, the results also provide an evidence for the short-range-ordered liquid metal.
基金This work was supported by the National Natural Science Foundation of China(Nos.51972342,and 51872056)Taishan Scholar Project of Shandong Province(ts20190922)+3 种基金Key Basic Research Project of Natural Science Foundation of Shandong Province(ZR2019ZD51)Project funded by China Postdoctoral Science Foundation(2019TQ0353 and 2020M672165)Fundamental Research Funds for the Central Universities(20CX06024A)Shandong Provincial Natural Science Foundation,China(ZR201911040344).
文摘Due to their rapid power delivery,fast charging,and long cycle life,supercapacitors have become an important energy storage technology recently.However,to meet the continuously increasing demands in the fields of portable electronics,transportation,and future robotic technologies,supercapacitors with higher energy densities without sacrificing high power densities and cycle stabilities are still challenged.Transition metal compounds(TMCs)possessing high theoretical capacitance are always used as electrode materials to improve the energy densities of supercapacitors.However,the power densities and cycle lives of such TMCs-based electrodes are still inferior due to their low intrinsic conductivity and large volume expansion during the charge/discharge process,which greatly impede their large-scale applications.Most recently,the ideal integrating of TMCs and conductive carbon skeletons is considered as an effective solution to solve the above challenges.Herein,we summarize the recent developments of TMCs/carbon hybrid electrodes which exhibit both high energy/power densities from the aspects of structural design strategies,including conductive carbon skeleton,interface engineering,and electronic structure.Furthermore,the remaining challenges and future perspectives are also highlighted so as to provide strategies for the high energy/power TMCs/carbon-based supercapacitors.
文摘This review paper aims at analysing the state of the art for partial oxidation and oxidative dehydrogenation（ODH） reactions of lower alkanes C–Cinto olefins and oxygenated products（aldehydes, anhydrides,carboxylic acids） on metal oxide catalysts with cations of variable oxidation state, such as Mo and V in particular. Key parameters to be met by the catalysts, such as their redox properties, their structural aspects, active sites composed of ensembles of atoms isolated one from the others, mechanisms of reactions, are discussed. Main features of the different reactions of C–Calkanes and catalysts are analysed and their generalisation for determining more active and more selective catalysts is attempted. Prospective views for the future of the domain are proposed.
基金financial support from Zhejiang Province Basic Public Welfare Research Project(LGF19B070006)financial supports from National Natural Science Foundation of China(21922811,21878270,51702284,21961160742)+2 种基金Zhejiang Provincial Natural Science Foundation of China(LR19B060002)supported by the Fundamental Research Funds for the Central Universitiesthe Startup Foundation for Hundred-Talent Program of Zhejiang University.
文摘Atomically dispersed metal-nitrogen sites-anchored carbon materials have been developed as effective catalysts for CO2 electroreduction(CO2 ER),but they still suffer from the imprecisely control of type and coordination number of N atoms bonded with central metal.Herein,we develop a family of single metal atom bonded by N atoms anchored on carbons(SAs-M-N-C,M=Fe,Co,Ni,Cu)for CO2 ER,which composed of accurate pyrrole-type M-N4 structures with isolated metal atom coordinated by four pyrrolic N atoms.Benefitting from atomically coordinated environment and specific selectivity of M-N4 centers,SAs-Ni-N-C exhibits superior CO2 ER performance with onset potential of-0.3 V,CO Faradaic efficiency(F.E.) of 98.5%at-0.7 V,along with low Tafel slope of 115 mV dec-1 and superior stability of 50 h,exceeding all the previously reported M-N-C electrocatalysts for CO2-to-CO conversion.Experimental results manifest that the different intrinsic activities of M-N4 structures in SAs-M-N-C result in the corresponding sequence of Ni> Fe> Cu> Co for CO2 ER performance.An integrated Zn-CO2 battery with Zn foil and SAs-Ni-N-C is constructed to simultaneously achieve CO2-to-CO conversion and electric energy output,which delivers a peak power density of 1.4 mW cm-2 and maximum CO F.E.of 93.3%.
基金supported by grants from Provincial Key Projects of Anhui Natural Science Research in Universities(No.KJ2015A203)the Natural Science Foundation of Anhui Province(No.1408085MB40)Projects of Anhui Key Laboratory of Spin Electron and Nanomaterials,Suzhou University(No.2014YKF51)
文摘A novel zinc complex [Zn（BIB）（bdc）]n（1, BIB = 1,3-bis（imidazol-1-yl）benzene, bdc = 1,3-benzenedicarboxylate） has been synthesized in solvothermal conditions. The title complex was characterized by elemental analysis, IR spectra, thermal analysis, single-crystal and powder X-ray diffraction. The result proved that the alliance of BIB and aromatic carboxylic acids is good for the diversity of getatable structure. Complex 1 crystallizes in the monoclinic system of P2/c space group with a = 11.5591（10）, b = 9.6239（8）, c = 33.727（3）A, β = 103.816（3）°, V = 3643.4（5） A^3, Z = 8, μ = 1.385 mm^-1, F（000） = 1792, Dc = 1.603 g/cm^3 and Mr = 439.72 g/mol. Additionally, luminescent properties of complex 1 are also investigated and it shows good fluorescence.
基金supported by the Natural Science Foundation of Fujian Province(2015J01038)Provincial Education Department of Fujian(JA12070)State Key Laboratory of Structural Chemistry(20150015)
文摘The hydrothermal reaction of 5-methoxyisophthalic acid（MeO-H2ip）, 1,3-bis（2-methylimidazol-1-yl）propane（bmip） and Zn（NO3）2·6H2O in the presence of NaOCH3 gave rise to a three-dimensional（3-D） metal-organic framework containing octanuclear Zn（II） units, [Zn4（MeO-ip）3（OH）2（bmip）]n. Single-crystal X-ray diffraction analysis reveals that the complex crystallizes in the triclinic space group P1 with a = 11.348（3）, b = 14.163（4）, c = 15.088（4） , α = 108.537（2）, β = 106.542（2）, γ = 103.106（1）o, V = 2065.4（9） -3, Z = 2, Mr = 334.62, Dc = 1.740 g·cm-（-3）, μ = 2.375 mm-（-1）, S = 1.015, F（000） = 1096, the final R = 0.0272 and w R = 0.0715 for 8929 observed reflections（I 〉 2σ（I））. The complex is thermally stable up to 370 oC, and exhibits photoluminescent emission at 450 nm on 350 nm excitation.
