检索结果-南通市图书馆

Segmental nature of the Red River fault revealed by seismic anisotropy and geological structures

在线全文

学校读者我要写书评

暂无评论

Science China earth Sciences 2024年第8期67卷 2423-2443页

作者： Ying li Yuan GAO School of earth and Space Sciences University of Science and Technology of ChinaHefei 230026China Key Laboratory of earthquake Prediction Institute of Earthquake ForecastingChina Earthquake AdministrationBeijing 100036China

As the western boundary of the Sichuan-Yunnan block(SYB),the Red River fault(RRF)is a major fault that controls deep crustal movement and deformation in the southeast margin of the Tibetan Plateau and regulates middle-lower crustal *** data suggest that the RRF is segmented and exhibits distinct variations in seismicity,velocity structure and crustal deformation from north to *** anisotropy reveals a complex pattern of lateral spatial and vertical stratified distributions.(1)From the perspective of crustal stratification,in the upper crust,the fast wave polarization in the north segment of the RRF is complex and possibly influenced by the Sanjiang lateral collision zone and adjacent faults with varying *** fast wave polarization in the middle segment is in the NW-Se direction,indicating a localized area of closed down or locked up with consistent *** in the south segment,it presents a disordered pattern,signifying complex deep tectonics and stress conditions at the wedged intersection *** the middle-lower crust in the north and south segments of the RRF,the azimuthal anisotropy is strong and consistent with the spatial strike of the weak zone characterized by low-velocity and *** suggests a connection between the anisotropy and the material migration.(2)In the whole crustal scale,the fast wave directions in two sides of the RRF are consistent with the NW-Se tectonic *** indicates that the RRF,as a large fault potentially cutting through the whole crust,strongly controls the surrounding media.(3)In the lithospheric scale,the fast wave polarizations are oriented nearly e-W and independent of the fault strike,consistent with the low P-and S-wave velocity structures and positive radial anisotropy in the upper *** fast wave directions could be related to lithospheric olivine deformation and asthenospheric *** paper suggests a decoupling of deformation between the crust and the lithospheri

关键词： Red River fault Seismic anisotropy Geological structures lithosphere Fault segmentation

Three-stage niobium mineralization at Bayan Obo, China

在线全文

学校读者我要写书评

暂无评论

National Science Review 2024年第4期11卷 102-110页

作者： Yan Yu Yang li Yu liu Xiao-Xiao ling li-Guang Wu li Yang Lan Yang Bo Yang Yong-Gang Zhao Xian-Hua li State Key Laboratory of lithospheric evolution Institute of Geology and Geophysics Chinese Academy of Sciences College of earth and Planetary Science University of Chinese Academy of Sciences Ministry of education Key Laboratory of Orogenic Belts and Crustal evolution School of Earth and Space SciencesPeking University Mining Research Institute Baotou Iron and Steel(Group) Co.LTD State Key Laboratory of Baiyunobo Rare earth Resource Research and Comprehensive Utilization

The Chinese Bayan Obo deposit is a world-class rare earth element(Ree) deposit with considerable niobium(Nb) and iron(Fe) resources. A complete genetic understanding on all metals is fundamental for establishing genetic models at Bayan Obo. With extensive research being focused on Ree enrichment, the timing and controls of Nb enrichment remain unresolved at Bayan Obo, which is mainly due to the challenges in dating, i.e. multistage thermal events, fine-grained minerals with complex textures and the rare occurrence of uranium-enriched minerals with mature dating methods. Based on robust geological and petrographic frameworks, here we conducted ion probe uranium-lead(U-Pb) dating of ferrocolumbite to unravel the timing, hence the genesis of Nb mineralization. Three types of hydrothermal ferrocolumbites—key Nb-bearing minerals—are identified based on their textures and mineral assemblages. They yield U-Pb ages of 1312 ± 47 Ma(n = 99), 438 ± 7 Ma(n = 93), and 268 ± 5 Ma(n = 19), respectively. In line with deposit geology, we tentatively link the first, second and third stage Nb mineralization to Mesoproterozoic carbonatite magmatism, ubiquitous early Paleozoic hydrothermal activity, and Permian granitic magmatism, respectively. While quantifying the contribution of metal endowment from each stage requires further investigation, our new dates highlight that multi-stage mineralization is critical for Nb enrichment at Bayan Obo, which may also have implications for the enrichment mechanism of Nb in Ree deposits in general.

关键词： niobium mineralization U-Pb dating ferrocolumbite Bayan Obo

Fusion of a rice endogenous N-methylpurine DNA glycosylase to a plant adenine base transition editor ABe8e enables A-toK base editing in rice plants

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

aBIOTeCH 2024年第2期5卷 127-139页

作者： Yucai li Shaoya li Chenfei li Chen Zhang Lei Yan Jingying li Yubing He Yan Guo Lanqin Xia Institute of Crop Sciences(ICS) Chinese Academy of Agricultural Sciences(CAAS)Beijing 100081China State Key Laboratory of Plant Physiology and Biochemistry College of Biological SciencesChina Agricultural UniversityBeijing 100193China Hainan Yazhou Bay Seed Laboratory/National Nanfan Research Institute(Sanya) CAASSanya 572024China

engineering of a new type of plant base editor for simultaneous adenine transition and transversion within the editing window will greatly expand the scope and potential of base editing in directed evolution and crop ***,we isolated a rice endogenous hypoxanthine excision protein,N-methylpurine DNA glycosylase(OsMPG),and engineered two plant A-to-K(K=G or T)base editors,rAKBe01 and rAKBe02,for simultaneous adenine transition and transversion base editing in rice by fusing OsMPG or its mutant mOsMPG to a plant adenine transition base editor,*** further coupled either OsMPG or mOsMPG with a transactivation factor VP64 to generate rAKBe03 and rAKBe04,*** these four rAKBes,at five endogenous loci in rice protoplasts,indicated that rAKBe03 and rAKBe04 enabled higher levels of A-to-G base transitions when compared to ABe8e and ***,whereas rAKBe01 only enabled A-to-C/T editing at one endogenous locus,in comparison with rAKBe02 and rAKBe03,rAKBe04 could significantly improve the A-to-C/T base transversion efficiencies by up to 6.57-and 1.75-fold in the rice protoplasts,***,although no stable lines with A-to-C transversion were induced by rAKBe01 and rAKBe04,rAKBe04 could enable simultaneous A-to-G and A-to-T transition and transversion base editing,at all the five target loci,with the efficiencies of A-to-G transition and A-to-T transversion editing ranging from 70.97 to 92.31%and 1.67 to 4.84%in rice stable lines,***,these rAKBes enable different portfolios of editing products and,thus,now expands the potential of base editing in diverse application scenario for crop improvement.

关键词： Rice(Oryza sativa L) Rice N-methylpurine DNA glycosylase(OsMPG) A-to-K base editor(AKBe) Transactivation module VP64

A Novel Divide and Conquer Solution for Long-term Video Salient Object Detection

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Machine Intelligence Research 2024年第4期21卷 684-703页

作者： Yun-Xiao li Cheng-li-Zhao Chen Shuai li Ai-Min Hao Hong Qin State Key Laboratory of Virtual Reality Technology and Systems Beihang UniversityBeijing 100191China College of Computer Science and Technology China University of Petroleum(East China)Qingdao 266580China Department of Computer Science Stony Brook UniversityNew York 11794USA

Recently,a new research trend in our video salient object detection(VSOD)research community has focused on enhancing the detection results via model self-fine-tuning using sparsely mined high-quality keyframes from the given *** such a learning scheme is generally effective,it has a critical limitation,i.e.,the model learned on sparse frames only possesses weak generalization *** situation could become worse on“long”videos since they tend to have intensive scene ***,in such videos,the keyframe information from a longer time span is less relevant to the previous,which could also cause learning conflict and deteriorate the model ***,the learning scheme is usually incapable of handling complex pattern *** solve this problem,we propose a divide-and-conquer framework,which can convert a complex problem domain into multiple simple ***,we devise a novel background consistency analysis(BCA)which effectively divides the mined frames into disjoint *** for each group,we assign an individual deep model on it to capture its key attribute during the fine-tuning *** the testing phase,we design a model-matching strategy,which could dynamically select the best-matched model from those fine-tuned ones to handle the given testing *** experiments show that our method can adapt severe background appearance variation coupling with object movement and obtain robust saliency detection compared with the previous scheme and the state-of-the-art methods.

关键词： Video salient object detection background consistency analysis weakly supervised learning long-term information background shift.

Constrained docking control for shipborne UAV SideArm recovery

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第5期37卷 39-59页

作者： Zikang SU Zhuolin XING Xuebing li Chuntao li Xinwei WANG Honglun WANG College of Automation engineering Nanjing University of Aeronautics and AstronauticsNanjing 211106China School of engineering and Materials Science Queen Mary University of LondonLondon E14NSUK School of Automation Science and electrical engineering Beihang UniversityBeijing 100191China

In this work,we sought to investigate constrained docking control during shipborne SideArm recovery of an Unmanned Aerial Vehicle(UAV)under preassigned safe docking constraints,rough ocean environments,and different initial *** aim was to solve the UAV tracking-lag problem that manifests when attempting to dock with a rapidly moving SideArm and to improve the accuracy and rapidity of ***,together with the formulations of the shipborne SideArm system and environmental airflows,the affine nonlinear dynamics of the hook was established to reduce tracking ***,echo state network approximators with good approximation capacity and low computational consumption were designed to accurately approximate the UAV’s unknown nonlinear *** feedforward compensation provided by these approximators,a nonlinear-mapping-based constrained docking control law was developed for shipborne SideArm recovery of *** approach to controlling the docking trajectory and the forward docking speed of the UAV can achieve rapid and exact docking with a moving SideArm,without violating the preassigned safe docking-constraint *** under different docking scenarios were used to validate the effectiveness and advantages of the proposed docking-control algorithm.

关键词： SideArm recovery Unmanned aerial vehicle Docking control Nonlinear mapping echo state network

Improved Approximation Schemes for early Work Scheduling on Identical Parallel Machines with a Common Due Date

在线全文

学校读者我要写书评

暂无评论

Journal of the Operations Research Society of China 2024年第2期12卷 341-350页

作者： Wei-Dong li School of Mathematics and Statistics Yunnan UniversityKunming650504YunnanChina

We study the early work scheduling problem on identical parallel machines in order to maximize the total early work,i.e.,the parts of non-preemptive jobs that are executed before a common due *** preprocessing and constructing an auxiliary instance which has several good properties,for any desired accuracy,we propose an efficient polynomial time approximation scheme with running time O(f(1/ε)n),where n is the number of jobs and f(1/ε)is exponential in 1/ε,and a fully polynomial time approximation scheme with running time O(1/ε^(2m+1)+n)when the number of machines is fixed.

关键词： Scheduling early work Polynomial time approximation scheme effcient polynomial time approximation scheme Fully polynomial time approximation scheme

efflcient machining of a complex blisk channel using a disc cutter

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第1期37卷 414-437页

作者： Xiangyu li Zhaoyu li Dong He Junxue ReN Qian FeNG Kai TANG Department of Mechanical and Aerospace engineering Hong Kong University of Science and TechnologyHong Kong 999077China Key Laboratory of High Performance Manufacturing for Aero engine(Northwestern Polytechnical University) Ministry of Industry and Information TechnologyXi’an 710072China Xi’an Sanhang Power Technology Co. LtdXi’an 710000China HKUST Shenzhen-Hong Kong Collaborative Innovation Research Institute FutianShenzhen 518057China HKUST Shenzhen Research Institute Shenzhen 518057China

For rough machining of a complex narrow cavity,e.g.,a complex blisk channel on an aero-engine,the typically used cutting tools are the slender cylindrical cutter and conical ***,as neither of the two is particularly suited for rough machining,wherein the main purpose is to remove a large volume as quickly as possible,the machining efficiency is low,especially when the part materials are of hard-to-cut types(e.g.,Titanium-alloy)for which it often takes days to rough machine a ***,disc machining provides a new and efficient roughing solution,since a disc cutter with a large radius enables a much larger cutting speed and thus a larger material removal ***,due to the large radius of the disc cutter,its potential collision with narrow and twisted channels becomes a serious *** this paper,we propose a novel twophase approach for efficiently machining a complex narrow cavity workpiece using a disc-shaped cutter,i.e.,3+2-axis disc-slotting of the channel by multiple layers(rough machining)+five-axis disc-milling of the freeform channel side surfaces(semi-finish machining).Both simulation and physical cutting experiments are conducted to assess the effectiveness and advantages of the proposed *** experimental results show that,with respect to a same cusp-height threshold on the channel side surfaces,the total machining time of the tested part by the proposed method is about only 36%of that by the conventional approach of plunging-milling(for roughing)plus milling by a slender cylindrical cutter(for semi-finishing).

关键词： Blisk channel CNC machining Disc cutter Roughing efficiency Tool path planning

Predicting torsional capacity of reinforced concrete members by data-driven machine learning models

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil engineering 2024年第3期18卷 444-460页

作者： shenggang CHeN Congcong CHeN shengyuan li Junying GUO Quanquan GUO Chaolai li School of Mechanics and Civil engineering China University of Mining and TechnologyXuzhou 211116China Jiangsu Key Laboratory environmental Impact and Structural Safety in engineering China University of Mining and TechnologyXuzhou 211116China China Nuclear Power Design Co.Ltd. Shenzhen 518031China School of transportation and science engineering Beihang UniversityBeijing 100191China China Construction First Group Corporation limited Beijing 100161China

Due to the complicated three-dimensional behaviors and testing limitations of reinforced concrete(RC)members in torsion,torsional mechanism exploration and torsional performance prediction have always been *** the present paper,several machine learning models were applied to predict the torsional capacity of RC *** results of a total of 287 torsional specimens were collected through an overall literature *** of extreme gradient boosting machine(XGBM),random forest regression,back propagation artificial neural network and support vector machine,were trained and tested by 10-fold cross-validation *** performances of proposed machine learning models were evaluated and compared,both with each other and with the calculated results of existing design codes,i.e.,GB 50010,ACI 318-19,and eurocode *** results demonstrated that better predictive performance was achieved by machine learning models,whereas GB 50010 slightly overestimated the torsional capacity,and ACI 318-19 and eurocode 2 underestimated it,especially in the case of ACI *** XGBM model gave the most favorable predictions with R^(2)=0.999,RMSe=1.386,MAe=0.86,andλ=***,strength of concrete was the most sensitive input parameters affecting the reliability of the predictive model,followed by transverse-to-longitudinal reinforcement ratio and total reinforcement ratio.

关键词： RC members torsional capacity machine learning models design codes

Orbital pacing and secular evolution of lake-level changes reconstructed by sedimentary noise modeling during the early Jurassic icehouses-(super)greenhouses

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China earth Sciences 2024年第1期67卷 252-267页

作者： Meng li Xin li Stephen P.HeSSeLBO Mingjie li Wenjin liU Wei WU Jienan PAN Ruizhen GAO School of Resources and environment Henan Polytechnic UniversityJiaozuo 454000China Camborne School of Mines and environment and Sustainability Institute University of ExeterPenryn TR109FEUnited Kingdom Qinghai No.105 Coal Geological exploration Team Xining 810000China

Lake-level changes can significantly affect paleoenvironmental evolution,resource occurrence,terrestrial carbon budget,and biodiversity in continental *** is one of the most critical factors controlling lake-level *** of the early Jurassic has been evidenced by oscillating icehouses to(super)greenhouses with interrupted intermittent extreme climatic events(hyperthermal and cooling),e.g.,the Toarcian oceanic anoxic event(~183 Ma)and the late Pliensbachian cooling event(~185 Ma).Lake-level evolution and hydrologic cycling on earth’s surface during the early Jurassic icehouses-to-(super)greenhouses are thus far poorly understood due to a lack of continuous high-resolution nonmarine *** we present a super-long nonmarine lake level record for this pivotal interval from the early Pliensbachian to Toarcian by sedimentary noise modeling,and construct a 16.7-Myr-long astronomical time scale(174.2 Ma to 190.9 Ma)based on cyclostratigraphy analysis of rock color datasets(CIe b*)of the Qaidam *** results document lake-level oscillations on a 5-to 10-million-year(Myr)scale which shows a pronounced correlation with long-term climate variation and extreme climatic events,and 1-to 2.5-Myr-scale lake-level changes that are prominently paced by the 2.4-Myr long-eccentricity forcing and the 1.2-Myr obliquity *** the Pliensbachian Stage,the 1.2-Myr-scale lake-level changes are in phase with the coeval sealevel *** forced growth and decay of the ephemeral or permanent ice sheets in polar regions are interpreted to control the synchronous ups-and-downs of continental lake level and global sea ***,during the Toarcian ice-free greenhouses to(super)greenhouses,the 1.2-Myr-scale lake-level variations show an anti-phase relationship with global sea level,indicating a‘seesaw’interaction between continental reservoirs(lakes and groundwater)and global *** 2.4-Myr longeccentricity cycles mainly regulate variation

关键词： Milankovitch cycles Orbital forcing Sedimentary noise model Lake level Continental basins