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Buckling optimization of curvilinear fiber-reinforced composite structures using a parametric level set method

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Frontiers of Mechanical Engineering 2024年第1期19卷 149-160页

作者： Ye tian Tielin shi Qi XIA State Key Laboratory of Intelligent Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China

Owing to their excellent performance and large design space,curvilinear fiber-reinforced composite structures have gained considerable attention in engineering fields such as aerospace and *** addition to the stiffness and strength of such structures,their stability also needs to be taken into account in the *** study proposes a level-set-based optimization framework for maximizing the buckling load of curvilinear fiber-reinforced composite *** the proposed method,the contours of the level set function are used to represent fiber *** a composite laminate with a certain number of layers,one level set function is defined by radial basis functions and expansion coefficients for each ***,the fiber angle at an arbitrary point is the tangent orientation of the contour through this *** the finite element of buckling,the stiffness and geometry matrices of an element are related to the fiber angle at the element *** study considers the parallelism constraint for fiber *** the sensitivity calculation of the objective and constraint functions,the method of moving asymptotes is utilized to iteratively update all the expansion coefficients regarded as design *** numerical examples under different boundary conditions are given to validate the proposed *** show that the optimized curved fiber paths tend to be parallel and equidistant regardless of whether the composite laminates contain holes or ***,the buckling resistance of the final design is significantly improved.

关键词： buckling optimization curvilinear fiber composite structure level set method manufacturing constraint

Systematic study of the synthesis of heavy and superheavy nuclei in 48Ca-induced fusion-evaporation reactions

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Nuclear Science and Techniques 2024年第7期35卷 157-172页

作者： shi-Hao Zhu tian-Liang Zhao Xiao-Jun Bao Department of Physics Collaborative Innovation Center for Quantum EffectsKey Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of EducationHunan Normal UniversityChangsha410081China School of Nuclear Science and Technology Lanzhou UniversityLanzhou730000China School of Physics Xi’an Jiaotong UniversityXi’an710049China

We systematically studied the evaporation residue cross sections of ^(48)Ca-induced reactions on lanthanide and actinide target nuclei under the Dinuclear System(DNS)model framework to check the reliability and applicability of the *** produce new proton-rich Fl and Lv isotopes through hot fusion reactions in the superheavy element region with Z≥104,we utilized the reactions ^(48)Ca+^(236,238,239) Pu and ^(48)Ca+^(242,243,244,250) ***,owing to the detection limit of available equipment(0.1 pb),only 283Fl and 287−289Lv,which have the maximum evaporation residue cross section values of 0.149,0.130,9.522,and 0.309 pb,respectively,can be ***,to produce neutron-deficient isotopes of actinides near the proton drip line with Z=93−100,we attempted to generate the new isotopes(224−227Pu,228−232,237Cm)using the reactions ^(48)Ca+180,182,183 W and ^(48)Ca+^(184,186,187,192) *** maximum evaporation residue cross section values are 0.07,0.06,0.26,and 0.30 nb for the former set of reactions,and 1.96 pb,5.73 pb,12.16 pb,19.39 pb,54.79 pb,and 6.45 nb for the latter,*** results are expected to provide new information for the future synthesis of unknown neutron-deficient isotopes.

关键词： Dinuclear system(DNS)model Evaporation residue cross section Neutron-deficient isotopes

Oxygen vacancy boosting Fenton reaction in bone scaffold towards fighting bacterial infection

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International Journal of Extreme Manufacturing 2024年第1期6卷 296-311页

作者： Cijun Shuai Xiaoxin shi Feng Yang Haifeng tian Pei Feng State Key Laboratory of Precision Manufacturing for Extreme Service Performance College of Mechanical and Electrical EngineeringCentral South UniversityChangsha 410083People’s Republic of China Institute of Additive Manufacturing Jiangxi University of Science and TechnologyNanchang 330013People’s Republic of China College of Mechanical Engineering Xinjiang UniversityUrumqi 830017People’s Republic of China

Bacterial infection is a major issue after artificial bone transplantation due to the absence of antibacterial function of bone scaffold,which seriously causes the transplant failure and even amputation in severe *** this study,oxygen vacancy(OV)defects Fe-doped Ti O2(OV-FeTiO2)nanoparticles were synthesized by nano TiO2and Fe3O4via high-energy ball milling,which was then incorporated into polycaprolactone/polyglycolic acid(PCLGA)biodegradable polymer matrix to construct composite bone scaffold with good antibacterial activities by selective laser *** results indicated that OV defects were introduced into the core/shell-structured OV-FeTiO2nanoparticles through multiple welding and breaking during the high-energy ball milling,which facilitated the adsorption of hydrogen peroxide(H2O2)in the bacterial infection microenvironment at the bone transplant *** accumulated H2O2could amplify the Fenton reaction efficiency to induce more hydroxyl radicals(·OH),thereby resulting in more bacterial deaths through·OH-mediated oxidative *** antibacterial strategy had more effective broad-spectrum antibacterial properties against Gram-negative Escherichia coli(***)and Gram-positive Staphylococcus aureus(***).In addition,the PCLGA/OV-FeTiO2scaffold possessed mechanical properties that match those of human cancellous bone and good biocompatibility including cell attachment,proliferation and osteogenic differentiation.

关键词： bacterial infection bone scaffold selective laser sintering Fenton reaction antibacterial properties

The relationship between interannual dry/wet changes and nomadic wars in the Hexi Corridor region of China during the period 241–1912 A.D.

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Science China Earth Sciences 2024年第6期67卷 1922-1931页

作者： Fei TANG Zhilin shi Qinhua tian Xiaogang DU Yong ZHANG Key Laboratory of Land Surface Pattern and Simulation Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China Institute of Dunhuang Studies Lanzhou UniversityLanzhou 730020China National Climate Center China Meteorological AdministrationBeijing 100081China Longchanghe Station Gansu Qilian Mountain National Nature ReserveZhangye 734400China University of Chinese Academy of Sciences Beijing 100049China

The link between climate and war has long been a topic of great scientific and social *** this study,we investigate the influence of climate on warfare in China’s Hexi Corridor region since 241 *** the superposed epoch analysis of tree-ring data and historical war data,we observe a notable correlation between interannual dry-wet variations and wars instigated by nomadic groups in the Hexi ***,this relationship is dynamic and influenced by the region’s relative *** periods in which the Hexi Corridor was ruled by multiple regimes,wars tended to follow dry climatic conditions,which may be due to the fact that unusual drought during these periods likely heightened competition for resources and ***,during times of regional unity,wars were more likely to occur when climatic conditions were wet because the expansion of rangelands and the accumulation of resources helped fuel the nomads’outward *** findings underscore the complexity of the relationship between war and climate *** gain a more comprehensive understanding of this relationship,continuous,high-resolution historical temperature and humidity datasets with broader and more uniform coverage are needed across multiple *** addition,collecting and examining disaggregated historical war data for regions with distinct characteristics is essential.

关键词： Drought Interannual dry and wet variations War The Hexi Corridor Tree ring Nomadic groups

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Deammoniative Condensation of Primary Allylic Amines with Nonallylic Amines

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Chinese Journal of Chemistry 2014年第8期32卷 741-751页

作者： Yong Wang Manbo Li Xiantao Ma Congrong Liu Yonghong Gu shi-kai tian Department of Chemistry University of Science and Technology of ChinaHefeiAnhui 230026China Department of Environmental Engineering Nanjing Institute of TechnologyNanjingJiangsu 211167China

An unprecedented deammoniative condensation reaction of primary allylic amines with nonallylic amines has been developed through C-N bond *** the presence of 5 mol%palladium diacetate,10 mol%1,4-bis(diphenylphosphino)butane(dppb),and 5 mol%p-toluenesulfonic acid(TsOH),a range of α-unbranched primary allylic amines smoothly underwent deammoniative condensation with nonallylic amines in an α-selective fashion to give structurally diverse secondary and tertiary amines in good to excellent yields and E *** dppb with racemic 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl(BINAP)permitted the deammoniative condensation of enantioenriched α-chiral primary allylic amines with nonallylic amines to proceed with complete retention of *** ionization(ESI)mass spectrometric analysis of the reaction mixture permitted the identification of some π-allylpalladium intermediates,and plausible mechanisms have been proposed to account for the regioselectivity and stereospecificity of the deammoniative condensation reaction.

关键词： amines deammoniation palladium substitution stereospecificity

Counteracting effects on ENSO induced by ocean chlorophyll interannual variability and tropical instability wave-scale perturbations in the tropical Pacific

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Science China Earth Sciences 2024年第2期67卷 387-404页

作者： Rong-Hua ZHANG Feng tian Qidong shi Xiujun WANG Tongwen WU School of Marine Sciences Nanjing University of Information Science and TechnologyNanjing210044China Laoshan Laboratory Qingdao266237China Key Laboratory of Ocean Circulation and Waves Institute of OceanologyChinese Academy of SciencesQingdao266071China University of Chinese Academy of Sciences Beijing101408China Faculty of Geographical Sciences Beijing Normal UniversityBeijing100875China Earth System Modeling and Prediction Centre China Meteorological AdministrationBeijing100081China

Large perturbations in chlorophyll(Chl)are observed to coexist at interannual and tropical instability wave(TIW)scales in the tropical Pacific;at present,their combined effects on El Ni?o-Southern Oscillation(ENSO)through ocean biologyinduced heating(OBH)feedbacks are not understood ***,a hybrid coupled model(HCM)for the atmosphere and ocean physics-biogeochemistry(AOPB)in the tropical Pacific is adopted to quantify how ENSO can be modulated by Chl perturbations at interannual and TIW scales,individually or collectively,*** HCM-based sensitivity experiments demonstrate a counteracting effect on ENSO:the bio-climate feedback due to large-scale Chl interannual variability acts to damp ENSO through its impact on upper-ocean stratification and vertical mixing,whereas that due to TIW-scale Chl perturbations tends to amplify *** ENSO simulations are sensitively dependent on the ways Chl effects are represented at these different scales,it is necessary to adequately take into account these related differential Chl effects in climate modeling.A bias source for ENSO simulations is illustrated that is related with the Chl effects in the tropical Pacific,adding in a new insight into interactions between the climate system and ocean ecosystem on different scales in the *** results reveal a level of complexity of ENSO modulations resulting from Chl effects at interannual and TIW scales,which are associated with ocean biogeochemical processes and their interactions with physical processes in the tropical Pacific.

关键词： Ocean chlorophyll Bio-climate feedbacks Interannual variability Tropical instability waves Counteracting effects A hybrid coupled model

Wideband spectrum sensing using step-sampling based on the multipath nyquist folding receiver

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Defence Technology（防务技术） 2024年第1期31卷 523-536页

作者： kai-lun tian kai-li Jiang Sen Cao Jian Gao Ying Xiong Bin Tang Xu-ying Zhang Yan-fei Li University of Electronic Science and Technology of China Chengdu611731China China Electronics Technology Group Corporation 29th Research Institute Chengdu610036China

Wideband spectrum sensing with a high-speed analog-digital converter(ADC) presents a challenge for practical *** Nyquist folding receiver(NYFR) is a promising scheme for achieving cost-effective real-time spectrum sensing,which is subject to the complexity of processing the modulated *** this case,a multipath NYFR architecture with a step-sampling rate for the different paths is *** different numbers of digital channels for each path are designed based on the Chinese remainder theorem(CRT).Then,the detectable frequency range is divided into multiple frequency grids,and the Nyquist zone(NZ) of the input can be obtained by sensing these ***,high-precision parameter estimation is performed by utilizing the NYFR *** with the existing methods,the scheme proposed in this paper overcomes the challenge of NZ estimation,information damage,many computations,low accuracy,and high false alarm *** simulation experiments verify the effectiveness of the proposed architecture in this paper.

关键词： Wideband spectrum sensing Sub-Nyquist sampling Step-sampling Nyquist folding receiver(NYFR) Multisignal processing

Numerical simulation on sand sedimentation and erosion characteristics around HDPE sheet sand barrier under different wind angles

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Journal of Mountain Science 2024年第2期21卷 538-554页

作者： ZHANG kai ZHANG Peili ZHANG Hailong tian Jianjin WANG Zhenghui XIAO Jianhua College of Civil Engineering Lanzhou Jiaotong UniversityLanzhou 730000China Key Laboratory of Desert and Desertification Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China

For the safety of railroad operations,sand barriers are utilized to mitigate wind-sand disaster *** disasters,characterized by multi-directional wind patterns,result in diverse angles among the *** this study,using numerical simulations,we examined the behavior of High Density Polyethylene(HDPE)sheet sand barriers under different wind angles,focusing on flow field distribution,windproof efficiency,and sedimentation erosion *** study discovered that at a steady wind speed,airflow velocity varies as the angle between the airflow and the HDPE barrier ***,a 90°angle results in the widest low-speed airflow area on the barrier’s downwind *** the airflow is not perpendicular to the barrier,it prompts a lateral airflow movement which decreases as the angle *** windproof efficiency correlates directly with this angle but inversely with the wind’s ***,with a wind angle of 90°,wind speed drops by 81%.The minimum wind speed is found at 5.1H(the sand barrier height)on the barrier’s downwind *** the angle grows,the barrier’s windproof efficiency improves,extending its protective *** is most prominent on the barrier’s downwind side,as the wind angle shifts from 30°to 90°,the sand sedimentation area on the barrier’s downwind side enlarges by *** the angle grows,sedimentation intensifies,eventually overtakes the forward erosion and enlarges the sedimentation area.

关键词： Multi-wind direction HDPE sheet sand barrier Numerical simulation Windproof efficiency Sedimentation erosion

Numerical simulation of flow field deposition and erosion characteristics around bridge-road transition section

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Journal of Mountain Science 2024年第5期21卷 1491-1508页

作者： ZHANG kai WANG Zhenghui WANG Tao tian Jianjin ZHANG Hailong LIU Yonghe College of Civil Engineering Lanzhou Jiaotong UniversityLanzhou 730000China Key Laboratory of Desert and Desertification Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China

Wind-sand flow generates erosion and deposition around obstacles such as bridges and roadbeds, resulting in sand damage and endangering railway systems in sandy regions. Previous studies have mainly focused on the flow field around roadbeds, overlooking detailed examinations of sand particle erosion and deposition patterns near bridges and roadbeds. This study employs numerical simulations to analyze the influence of varying heights and wind speeds on sand deposition and erosion characteristics at different locations: the bridge-road transition section(side piers), middle piers, and roadbeds. The results show that the side piers, experience greater accumulation than the middle piers. Similarly, the leeward side of the roadbed witnesses more deposition compared to the windward side. Another finding reveals a reduced sand deposition length as the vertical profile, in alignment with the wind direction, moves further from the bridge abutments at the same clearance height. As wind speeds rise, there’s a decline in sand deposition and a marked increase in erosion around the side piers, middle piers and roadbeds. In conclusion, a bridge clearance that’s too low can cause intense sand damage near the side piers, while an extremely high roadbed may lead to extensive surface sand deposition. Hence, railway bridges in areas prone to sandy winds should strike a balance in clearance height. This research provides valuable guidelines for determining the most suitable bridge and roadbed heights in regions affected by wind and sand.

关键词： Sandstorm Flow field Bridge-road transition section Sedimentation erosion Numerical simulation