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Tailoring local structures of atomically dispersed copper sites for highly selective CO_(2) electroreduction
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作者 Kyung‐Jong Noh Byoung Joon Park +5 位作者 Ying Wang Yejung Choi Sang‐Hoon You Yong‐Tae Kim Kug‐Seung Lee Jeong Woo Han 《Carbon Energy》 SCIE EI CAS CSCD 2024年第4期79-90,共12页
Atomically‐dispersed copper sites coordinated with nitrogen‐doped carbon(Cu–N–C)can provide novel possibilities to enable highly selective and active electrochemical CO_(2) reduction reactions.However,the construc... Atomically‐dispersed copper sites coordinated with nitrogen‐doped carbon(Cu–N–C)can provide novel possibilities to enable highly selective and active electrochemical CO_(2) reduction reactions.However,the construction of optimal local electronic structures for nitrogen‐coordinated Cu sites(Cu–N_(4))on carbon remains challenging.Here,we synthesized the Cu–N–C catalysts with atomically‐dispersed edge‐hosted Cu–N_(4) sites(Cu–N_(4)C_(8))located in a micropore between two graphitic sheets via a facile method to control the concentration of metal precursor.Edge‐hosted Cu–N_(4)C_(8) catalysts outperformed the previously reported M–N–C catalysts for CO_(2)‐to‐CO conversion,achieving a maximum CO Faradaic efficiency(FECO)of 96%,a CO current density of–8.97 mA cm^(–2) at–0.8 V versus reversible hydrogen electrode(RHE),and over FECO of 90%from–0.6 to–1.0 V versus RHE.Computational studies revealed that the micropore of the graphitic layer in edge‐hosted Cu–N_(4)C_(8) sites causes the d‐orbital energy level of the Cu atom to shift upward,which in return decreases the occupancy of antibonding states in the*COOH binding.This research suggests new insights into tailoring the locally coordinated structure of the electrocatalyst at the atomic scale to achieve highly selective electrocatalytic reactions. 展开更多
关键词 atomic local structure density functional theory electrochemical CO_(2)reduction metal nitrogen‐doped carbon single‐atom catalyst
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Ultrafast dynamics of femtosecond laser-induced high spatial frequency periodic structures on silicon surfaces 被引量:2
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作者 Ruozhong Han Yuchan Zhang +6 位作者 Qilin Jiang Long Chen Kaiqiang Cao Shian Zhang Donghai Feng Zhenrong Sun Tianqing Jia 《Opto-Electronic Science》 2024年第3期33-46,共14页
Femtosecond laser-induced periodic surface structures(LIPSS)have been extensively studied over the past few decades.In particular,the period and groove width of high-spatial-frequency LIPSS(HSFL)is much smaller than t... Femtosecond laser-induced periodic surface structures(LIPSS)have been extensively studied over the past few decades.In particular,the period and groove width of high-spatial-frequency LIPSS(HSFL)is much smaller than the diffraction limit,making it a useful method for efficient nanomanufacturing.However,compared with the low-spatial-frequency LIPSS(LSFL),the structure size of the HSFL is smaller,and it is more easily submerged.Therefore,the formation mechanism of HSFL is complex and has always been a research hotspot in this field.In this study,regular LSFL with a period of 760 nm was fabricated in advance on a silicon surface with two-beam interference using an 800 nm,50 fs femtosecond laser.The ultrafast dynamics of HSFL formation on the silicon surface of prefabricated LSFL under single femtosecond laser pulse irradiation were observed and analyzed for the first time using collinear pump-probe imaging method.In general,the evolution of the surface structure undergoes five sequential stages:the LSFL begins to split,becomes uniform HSFL,degenerates into an irregular LSFL,undergoes secondary splitting into a weakly uniform HSFL,and evolves into an irregular LSFL or is submerged.The results indicate that the local enhancement of the submerged nanocavity,or the nanoplasma,in the prefabricated LSFL ridge led to the splitting of the LSFL,and the thermodynamic effect drove the homogenization of the splitting LSFL,which evolved into HSFL. 展开更多
关键词 laser-induced periodic surface structures(LIPSS) local field enhancement collinear pump-probe imaging silicon high spatial frequency periodic structures
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Necessary and Sufficient Conditions for Feasible Neighbourhood Solutions in the Local Search of the Job-Shop Scheduling Problem
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作者 Lin Gui Xinyu Li +1 位作者 Liang Gao Cuiyu Wang 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2023年第4期139-154,共16页
The meta-heuristic algorithm with local search is an excellent choice for the job-shop scheduling problem(JSP).However,due to the unique nature of the JSP,local search may generate infeasible neighbourhood solutions.I... The meta-heuristic algorithm with local search is an excellent choice for the job-shop scheduling problem(JSP).However,due to the unique nature of the JSP,local search may generate infeasible neighbourhood solutions.In the existing literature,although some domain knowledge of the JSP can be used to avoid infeasible solutions,the constraint conditions in this domain knowledge are sufficient but not necessary.It may lose many feasible solutions and make the local search inadequate.By analysing the causes of infeasible neighbourhood solutions,this paper further explores the domain knowledge contained in the JSP and proposes the sufficient and necessary constraint conditions to find all feasible neighbourhood solutions,allowing the local search to be carried out thoroughly.With the proposed conditions,a new neighbourhood structure is designed in this paper.Then,a fast calculation method for all feasible neighbourhood solutions is provided,significantly reducing the calculation time compared with ordinary methods.A set of standard benchmark instances is used to evaluate the performance of the proposed neighbourhood structure and calculation method.The experimental results show that the calculation method is effective,and the new neighbourhood structure has more reliability and superiority than the other famous and influential neighbourhood structures,where 90%of the results are the best compared with three other well-known neighbourhood structures.Finally,the result from a tabu search algorithm with the new neighbourhood structure is compared with the current best results,demonstrating the superiority of the proposed neighbourhood structure. 展开更多
关键词 SCHEDULING Job-shop scheduling local search Neighbourhood structure Domain knowledge
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Probing microstructure of solid-state synthesized LiCoO_(2)with MAS NMR spectroscopy
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作者 Suyu Gu Guozhong Lu +4 位作者 Nianrui Guo Juncheng Xu Yu Jiang Ming Shen Bingwen Hu 《Magnetic Resonance Letters》 2023年第4期298-305,共8页
LiCoO_(2)is an important category of active cathode materials in lithium-ion batteries due to its high compacted electrode density,good thermal stability,and stable voltage platform.Recent works on LiCoO_(2)have focus... LiCoO_(2)is an important category of active cathode materials in lithium-ion batteries due to its high compacted electrode density,good thermal stability,and stable voltage platform.Recent works on LiCoO_(2)have focused on the realization of higher charging voltages to fully utilize its high theoretical capacity.However,an unambiguous atomic-level local probe is essential for the understanding of structure-function correlation.Here we employ highresolution solid-state nuclear magnetic resonance(NMR)spectroscopy to study the local atomic environments in LiCoO_(2)synthesized with three common sintering methods.While one-dimensional 7Li NMR shows distinct linewidth and subtle dependence on lithium over-stoichiometry,both 7Li and 59Co relaxation times are highly dependent on the sintering method.We prove that the two-step sintering method favors the elimination of unreacted Co3O4,thereby enabling the best discharge capacity in all-solid-state lithium batteries assembled with LiCoO_(2)/LGPS/LiIn,which is in accordance with its narrowest 7Li linewidth and the longest 7Li/59Co T1. 展开更多
关键词 LiCoO_(2) Solid-state NMR T1 relaxation local structure
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A Study on the Participation of Foreign Students in Local Cultural and Folk Activities in Wenzhou
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作者 Chenjin Hong Xiaofang Ye 《教育技术与创新》 2023年第3期31-39,共9页
The number of foreign students studying in Wenzhou, China has increased dramatically as a result of the Belt and Road Initiative. Learning the motivations and leisure constraints of foreign students' participation... The number of foreign students studying in Wenzhou, China has increased dramatically as a result of the Belt and Road Initiative. Learning the motivations and leisure constraints of foreign students' participation in local cultural and folk activities in Wenzhou is beneficial to promoting cultural adaptation, strengthening Chinese cultural self-confidence, and improving Wenzhou's international image. Based on the hierarchical model of leisure constraints (personal constraints, interpersonal constraints, and structural constraints), this study has tended to focus on the leisure constraints for foreign students participating in local folk and cultural activities in Wenzhou. A total of seven participants were included in the analysis. 展开更多
关键词 Foreign Students local Cultural and Folk Activities Leisure Constraints Personal Constraints Interpersonal Constraints Structural Constraints WENZHOU
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Theoretical Investigations of the Local Structure Distortion and EPR Parameter for Ni2+-doped Perovskite Fluorides
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作者 曹喜民 邝小渝 +1 位作者 李成刚 柴瑞鹏 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2011年第2期167-172,I0003,共7页
By analyzing the optical spectra and electron paramagnetic resonance parameter D, the local structure distortion of (NiF6)4- clusters in AMF3 (A=K, Rb; M=Zn, Cd, Ca) and K2ZnF4 series are studied using the complet... By analyzing the optical spectra and electron paramagnetic resonance parameter D, the local structure distortion of (NiF6)4- clusters in AMF3 (A=K, Rb; M=Zn, Cd, Ca) and K2ZnF4 series are studied using the complete energy matrix based on the double spin-orbit coupling parameter model for configuration ions in a tetragonal ligand field. The results indicate that the contribution of ligand to spin-orbit coupling interaction should be considered for our studied systems. Moreover, the relationships between D and the spin-obit coupling coefficients as well as the average parameter and the divergent parameter are discussed. 展开更多
关键词 Complete energy matrix Double spin-orbit coupling parameter model local structure distortion
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Influence of backfilling rate on the stability of the"backfilling bodyimmediate roof"cooperative bearing structure 被引量:5
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作者 Xianjie Du Guorui Feng +2 位作者 Min Zhang Zehua Wang Wenhao Liu 《International Journal of Mining Science and Technology》 SCIE EI CAS CSCD 2022年第6期1197-1206,共10页
To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.Th... To reduce the cost of backfilling coal mining and utilize the underground space of coal mines,a new backfilling mining method with low backfilling rate called constructional backfilling coal mining(CBCM)is proposed.The "backfilling body-immediate roof" cooperative bearing structure of CBCM is analyzed by establishing the model of the medium thick plate on an elastic foundation.The influence of the backfilling rate on the stability of overlying strata is analyzed by the numerical simulation experiment.The control effect of CBCM is verified by a physic similar simulation test.The economic benefit of CBCM is analyzed.The conclusions are:the deformation characteristics of the immediate roof and critical backfilling spacing in CBCM can be analyzed based on the Hu Haichang’s theory.Exerting the bearing capacity of the immediate roof is beneficial to the stability of the overlying strata.The CBCM has a good control effect on the overburden in Xinyang Mine when the backfilling rate is lower than 25%.The backfilling cost of per ton coal is 37.39 yuan/t when the backfilling rate is 13.7%,with a decrease rate of 56.63%than the full-filling.The research results can provide theoretical support for the application of CBCM in coal mining. 展开更多
关键词 Constructional backfilling coal mining Immediate roof Cooperative bearing structure Medium thick plate on elastic foundation Backfilling rate Overlying strata
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Roof structure theory and support resistance determination of longwall face in shallow seam 被引量:2
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作者 黄庆享 《Journal of Coal Science & Engineering(China)》 2003年第2期21-24,共4页
This paper presents the structure models founded in shallow seam, the roof asymmetry arch with three articulations in roof first weighting and the step voussoir beam in roof periodic weighting. These structure models ... This paper presents the structure models founded in shallow seam, the roof asymmetry arch with three articulations in roof first weighting and the step voussoir beam in roof periodic weighting. These structure models are differ from classic theory, it establishes the new roof control theory of instability structure roof, especially in shallow seam. Based on the new roof structure theory, the support working state of "given sliding load" is put forward, and the factor of load transmitting is introduced to determine the load on roof structure. Therefore, the proper and accurate calculating methods of support resistance are established. Based on this, the dynamic structure theory in shallow seam could be predicted. 展开更多
关键词 shallow seam roof structure support resistance load transmitting
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Effect of a single weak lithological structure on the height of a collapsing roof in a deep soft rock roadway 被引量:2
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作者 YANG Jun 《Mining Science and Technology》 EI CAS 2010年第6期820-824,共5页
Besides the cross sections of roadways and the tendency and obliquity of roadway axes, the major controlling factors affecting the height of a collapsing roof include the weak lithological structure of surrounding roc... Besides the cross sections of roadways and the tendency and obliquity of roadway axes, the major controlling factors affecting the height of a collapsing roof include the weak lithological structure of surrounding rocks. This thesis analyzes the effect of two single and weak lithological structures of both sides and the roof on the height of a collapsing roof in a deep soft rock road- way. Using the two-dimensional UDEC3.1 software, a numerical structures of both sides of a roadway and of two weak lithological simulation was carried out on the models of weak lithological structures of roof of different depths. We reconstruct the overall processes from a break-away layer, bending, subsidence and the cracking of a collapsing roof. We also illustrate the distribution characteristics of displacement fields in the surrounding rock after the roof collapse in a deep soft rock roadway. The results of our numerical simulations indicate that the form of a roof collapse is side-expanding when the roadway is a weak structure at both sides The height of the roof collapse is related to the lithological combination of the roof when the roadway is a weak structure of the roof. 展开更多
关键词 single and weak lithological structure height of roof collapse numerical simulation
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Lessons from the seismic behavior of a steel grid roof structure heavily damaged in Lushan earthquake 被引量:5
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作者 Li Jichao Qu Zhe Wang Tao 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2019年第1期95-111,共17页
The seismic behavior of a school gymnasium, whose steel grid roof was heavily damaged during the Mw6.6 Lushan earthquake in 2013, is simulated through nonlinear dynamic analysis. The simulated damage is compared with ... The seismic behavior of a school gymnasium, whose steel grid roof was heavily damaged during the Mw6.6 Lushan earthquake in 2013, is simulated through nonlinear dynamic analysis. The simulated damage is compared with field observations to validate the numerical model, based on which a parametric study was performed to provide insight into the failure process and damage patterns of steel grids. The results suggest that the grid damage is strongly related to roofsubstructure interactions. These include not only the substructure's amplification of the vibration, but the uncoordinated displacement of the substructure's columns which support the grid also play an equally important role. In particular, the latter effect may significantly alter the internal force distribution in the steel grid and lead to unexpected buckling of members that are proportioned as tension-only members. While such interactions are generally not accounted for in the design practice for grid structures in China, similar seismic damage may be expected for other existing grid roofs in future earthquakes. As is also demonstrated in this study, seismic isolation of the roof is a promising solution to protect grid roof structures by mitigating the detrimental effects of roof-substructure interactions. 展开更多
关键词 Lushan EARTHQUAKE STEEL space structure roof-substructure interaction nonlinear dynamic analysis seismic isolation vertical ground motion
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First-principles study of the local structure and crystal field of Yb^(2+) in sodium and potassium halides
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作者 闻军 段昌奎 +3 位作者 尹民 Yu.V.Orlovskii 夏上达 章永凡 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第3期349-354,共6页
The local coordination structures around the doping Yb2+ ions in sodium and potassium halides were calculated by using the first-principles supercell model. Both the cases with and without the charge compensation vac... The local coordination structures around the doping Yb2+ ions in sodium and potassium halides were calculated by using the first-principles supercell model. Both the cases with and without the charge compensation vacancy in the local environment of the doping Yb2+ were calculated to study the effect of the doping on the local coordination structures of Yb2+. Using the calculated local structures, we obtained the crystal-field parameters for the Yb2+ ions doped in sodium and potassium halides by a method based on the combination of the quantum-chemical calculations and the effective Hamiltonian method. The calculated crystal-field parameters were analyzed and compared with the fitted results. 展开更多
关键词 sodium and potassium halides local coordination structure DISTORTION crystal-field parameters
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Finite symmetry transformation group and localized structures of the (2+1)-dimensional coupled Burgers equation
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作者 雷娅 杨铎 《Chinese Physics B》 SCIE EI CAS CSCD 2013年第4期46-49,共4页
In this paper, the finite symmetry transformation group of the (2+1)-dimensional coupled Burgers equation is studied by the modified direct method, and with the help of the truncated Painleve′ expansion approach, ... In this paper, the finite symmetry transformation group of the (2+1)-dimensional coupled Burgers equation is studied by the modified direct method, and with the help of the truncated Painleve′ expansion approach, some special localized structures for the (2+1)-dimensional coupled Burgers equation are obtained, in particular, the dromion-like and solitoff-like structures. 展开更多
关键词 finite transformation group modified direct method truncated Painleve′ expansion approach localized structure
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Investigations of the electron paramagnetic resonance parameters and the tetragonal local structure for (VCl_6)^(4-) coordination complex in MCl:V^(2+) (M=Na,K,Rb) systems
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作者 祁林 邝小渝 +2 位作者 柴瑞鹏 段美玲 张彩霞 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第4期1586-1593,共8页
By simulating the electron paramagnetic resonance (EPR) and optical spectra on the basis of the 120 × 120 complete energy matrix, this paper determines the local lattice structure parameters R1 and R2 for MCl... By simulating the electron paramagnetic resonance (EPR) and optical spectra on the basis of the 120 × 120 complete energy matrix, this paper determines the local lattice structure parameters R1 and R2 for MCl:V2+ (M=Na, K, Rb) systems at 77K, 195 K and RT (room temperature 295 K or 302 K), respectively. The theoretical results indicate that there exists a compressed distortion in MCl:V2+ systems. Meanwhile, it finds that the structure parameters R1, R2 and |△R|( = R1 - R2) increase with the rising temperature. Subsequently, from the analysis it concludes that the relation of EPR parameter D vs. △R is approximately linear. Finally, the effects of orbital reduction factor k on the g factors for the three systems have been discussed. 展开更多
关键词 complete energy matrix EPR parameters (VCl6)4- coordination complex local structure
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Effect of local structure on electron paramagnetic resonance spectra for trigonal [Cr(H_2O)_6]^(3+) coordination complex in the sulfate alums series:a ligand field theory study
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作者 李艳芳 邝小渝 +2 位作者 高明亮 赵亚儒 王怀谦 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第7期2967-2974,共8页
A simple theoretical method is introduced for studying the interrelation between electronic and molecular structures.By diagonalizing the 120 × 120 complete energy matrices,the relationships between zero-field sp... A simple theoretical method is introduced for studying the interrelation between electronic and molecular structures.By diagonalizing the 120 × 120 complete energy matrices,the relationships between zero-field splitting (ZFS) parameter D and local distortion parameter △θ for Cr^3+ ions doped,separately,in α- and β- alums are investigated.Our results indicate that there exists an approximately linear relationship between D and △θ in a temperature range 4.2-297 K and the signs of D and △θ are opposite to each other.Moreover,in order to understand the contribution of spin-orbit coupling coefficient ζ to ZFS parameter D,the relation between D and ζ is also discussed. 展开更多
关键词 complete energy matrices electron paramagnetic resonance (EPR) spectra local structure
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Influence of Fe in the local Structure of Perovskite Compound La_(2/3)Ca_(1/3)Fe_(1-x)Mn_(x)O_(3)
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作者 WEI Long WANG Yun-Bo +4 位作者 WANG Hui-Yao YUE Yong WANG Tian-Min ZHANG Tian-Bao CAO Guo-Hui 《Chinese Physics Letters》 SCIE CAS CSCD 2000年第6期446-447,共2页
The ceramic samples with nominal composition of La_(2/3)Ca_(1/3)Fe_(1-x)Mn_(x)O_(3)(0.01≤x≤0.20)were prepared by solid state reaction method.The effect of Fe doping on the Mn site was measured by the positron annihi... The ceramic samples with nominal composition of La_(2/3)Ca_(1/3)Fe_(1-x)Mn_(x)O_(3)(0.01≤x≤0.20)were prepared by solid state reaction method.The effect of Fe doping on the Mn site was measured by the positron annihilation technique and M'dssbauer spectroscopy.Upon doping,no appreciable structure change and electronic structure change in Mn-O plane were observed in the series of compounds.The M6ssbauer parameters show that the iron probe has stable 3+valance with the high spin state in all samples.Moreover,by examining the shape of the spectra,the tendency can be found that the isomer shift and quadruploe splitting increase with the increasing Fe+3 content.This phenomenon shows the local lattice distortion and the localization of d-electrons with the increasing Fe-doping content. 展开更多
关键词 local DOPING structure
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Practical Aspects of the Design and Construction of a Small Cable Roof Structure
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作者 Vinicius Fernando Arcaro Luiz Carlos de Almeida 《Open Journal of Civil Engineering》 2017年第3期453-467,共15页
Cable roof structures?have?only become widespread in large span structures in the latter part of the twentieth century. However,?they?still represent a relatively new form of roof construction, especially as in the pr... Cable roof structures?have?only become widespread in large span structures in the latter part of the twentieth century. However,?they?still represent a relatively new form of roof construction, especially as in the present case of a small span innovative structural solution. The contribution of this text to the structural engineering community lies in the increased interest in building simple cable roof structures. Since its completion in September 1996, this small cable roof structure has been recognized as an interesting architectural and structural example. The text describes aspects of the design and construction of a small cable roof that was designed as a roof for an open-air theater stage for the city of Sao Jose do Rio Pardo, Sao Paulo, Brazil. A cable network, in the shape of a hyperbolic paraboloid surface, is anchored in a reinforced concrete edge ring. The projection of the ring’s axis onto the ground plane is an ellipse. Workers with specialized training were employed in the various stages of the construction, which was completed in September 1996. 展开更多
关键词 CABLE roofS Hypar roofS Tension structureS
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LOCALIZED INDO STUDY OF THE ELECTRONIC STRUCTURE OF Sc(Sc_6Cl_(12)Co)
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作者 Song GAO Le Min LI Guang Xian XU (Research Center of Rare Earth Chemistry,Peking University,Beijing 100871,P.R.China) 《Chinese Chemical Letters》 SCIE CAS CSCD 1991年第2期171-174,共4页
Spin-unrestricted localized INDO method was used to calculate the electronic structure of rare earth cluster Sc(Sc_6Cl_(12)Co).Based on the analysis of the composition of the molecular orbitals and bond orders,it was ... Spin-unrestricted localized INDO method was used to calculate the electronic structure of rare earth cluster Sc(Sc_6Cl_(12)Co).Based on the analysis of the composition of the molecular orbitals and bond orders,it was pointed out that the interstitial transition metal atom Co in the octahedral Sc skeleton forms strong covalent bond with six Sc atoms and the bonding of Sc- Cl is mainly ionic in character.There are nine valence molecular orbitals in the cluster. 展开更多
关键词 INDO localIZED INDO STUDY of the ELECTRONIC structure of Sc CO Cl
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Experimental Study on Local Scour in the Downstream Area of Low Drop Structure Types
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作者 Changsung Kim Joongu Kang Hongkoo Yeo 《Engineering(科研)》 2012年第8期459-466,共8页
Although ecologically disadvantageous since a river is interrupted because of drop structure installation, such structure installation is also deemed ecologically advantageous in terms of scour and complex flows in th... Although ecologically disadvantageous since a river is interrupted because of drop structure installation, such structure installation is also deemed ecologically advantageous in terms of scour and complex flows in the direct downstream area. This study started from the premise that scour hole carries value as a habitat and sought to analyze quantitatively the local scour adjustment possibility in the downstream area through drop structure type change and to offer a habitat through scouring. This study provided changes in drop structure types, such as straight line type and V type. For local scour analysis impacting the downstream area by drop structure type, quantitative analysis of scour scope, depth, and length was comparatively performed for a tentative physical habitat through hydraulic experiments. As a result of the experiments, this study found that scour scope increases and various water depth conditions are offered as the angle of the drop structure’s apex becomes smaller. Future studies accompanied by various fish habitation evaluations are considered useful in finding an alternative to upgrade the ecological environment. 展开更多
关键词 LOW DROP structure local SCOUR PHYSICAL HABITAT SCOUR Size
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The influence of upstream slope on the local scour at drop structure
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作者 CHEN Jen-yan HSU Hsi-hsin HONG Yao-ming 《Journal of Mountain Science》 SCIE CSCD 2016年第12期2237-2248,共12页
The drop structure will fail as a result of local scoring downstream.This paper discusses the influence of a drop structures' upstream slope to local scour.Empirical equations of the scour hole were developed by l... The drop structure will fail as a result of local scoring downstream.This paper discusses the influence of a drop structures' upstream slope to local scour.Empirical equations of the scour hole were developed by laboratory experiment,theoretical assumptions,and regression analysis.These equations include the maximum scour depth and length during the scouring period,the maximum equilibrium scour depth and length,and the unit width scour rate.The four channel slopes(0%,2%,4%,and 6%) before the drop structure has been included in the analysis.A series of laboratory experiments were conducted to obtain 48 groups of experiments and 419 scour hole profiles during the scouring period.The material used in the scour section is uniform non-cohesive and with a median diameter of d50 = 0.5 mm.The results have been used to develop empirical equations via regression analysis to determine the coefficients of theoretical equations.The high correlation coefficient indicates that the equations developed in this study are suitable for verifying the characteristics of a scour hole at drop structure in the sloped channel.The semi-empirical equation is more accurate than the empirical equation.Compared to a horizontal channel,a sloped channel tends to cause a greater equilibriummaximum scour length,shorter equilibrium maximum scour depth,and faster unit-wide scour rate. 展开更多
关键词 Drop structure Jet flow Scour hole local scour Steep channel
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Design and Optimization of Steel Car Body Structures via Local Laser-Strengthening
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作者 Markus Wagner Axel Jahn +1 位作者 Eckhard Beyer Daniel Balzani 《Engineering(科研)》 2016年第5期276-286,共11页
Continuously rising demands of legislators require a significant reduction of CO2-emission and thus fuel consumption across all vehicle classes. In this context, lightweight construction materials and designs become a... Continuously rising demands of legislators require a significant reduction of CO2-emission and thus fuel consumption across all vehicle classes. In this context, lightweight construction materials and designs become a single most important factor. The main engineering challenge is to precisely adapt the material and component properties to the specific load situation. However, metallic car body structures using “Tailored blanks” or “Patchwork structures” meet these requirements only insufficiently, especially for complex load situations (like crash). An innovative approach has been developed to use laser beams to locally strengthen steel crash structures used in vehicle bodies. The method tailors the workpiece hardness and thus strength at selected locations to adjust the material properties for the expected load distribution. As a result, free designable 3D-strengthening-patterns surrounded by softer base metal zones can be realized by high power laser beams at high processing speed. The paper gives an overview of the realizable process window for different laser treatment modes using current high brilliant laser types. Furthermore, an efficient calculation model for determining the laser track properties (depth/width and flow curve) is shown. Based on that information, simultaneous FE modelling can be efficiently performed. Chassis components are both statically and cyclically loaded. Especially for these components, a modulation of the fatigue behavior by laser-treated structures has been investigated. Simulation and experimental results of optimized crash and deep drawing components with up to 55% improved level of performance are also illustrated. 展开更多
关键词 Automotive Lightweight structures local Laser Treatment Laser Beam Strengthening Crash Simulation Laser Strengthening Laser Hardening
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