检索结果-南通市图书馆

Potential Distribution of Seagrass Meadows Based on the MaxEnt Model in Chinese Coastal Waters

在线全文

学校读者我要写书评

暂无评论

Journal of Ocean University of China 2022年第5期21卷 1351-1361页

作者： wang Ming wang Yong LIU Guangliang CHEN Yuhu YU Naijing Center for High Performance Computing and System Simulation Pilot National Laboratory for Marine Science and TechnologyQingdao 266200China Shandong Provincial Key Laboratory of Computer Networks Qilu University of Technology(Shandong Academy of Sciences)Jinan 250101China

Seagrass meadows are generally diverse in China and have become important ecosystem with essential functions.However,the seagrass distribution across the seawaters of China has not been evaluated,and the magnitude and direction of changes in seagrass meadows remain unclear.This study aimed to provide a nationwide seagrass distribution map and explore the dynamic changes in seagrass population under global climate change.Simulation studies were performed using the modeling software MaxEnt with 58961 occurrence records and 27 marine environmental variables to predict the potential distribution of seagrasses and calculate the area.Seven environmental variables were excluded from the modeling processes based on a correlation analysis to ensure predicted suitability.The predicted area was 790.09 km^(2),which is much larger than the known seagrass distribution in China(87.65 km^(2)).By 2100,the suitable habitat of seagrass will shift northwest and increase to 923.62 km2.Models of the sum of the individual family under-pre-dicted the national distribution of seagrasses and consistently showed a downward trend in the future.Out of all environmental vari-ables,physical parameters(e.g.,depth,land distance,and sea surface temperature)contributed the most in predicting seagrass distri-butions,and nutrients(e.g.,nitrate,phosphate)ranked among the key influential predictors for habitat suitability in our study area.This study is the first effort to fill a gap in understanding the distribution of seagrasses in China.Further studies using modeling and biological/ecological approaches are warranted.

关键词： seagrass meadows species distribution modeling global climate change Chinese coastal waters

空间在轨环境下的30cm离子推力器三栅极组件间距变化仿真分析

在线全文

学校读者我要写书评

暂无评论

宇航学报 2019年第11期40卷 1375-1382页

作者：孙明明耿海王亮郑艺兰州空间技术物理研究所真空技术与物理重点实验室

采用有限元仿真(FEM)与地面热平衡试验验证相结合的方法,计算并模拟了30 cm离子推力器处于在轨环境时,有、无主动热控对三栅极相对位移变化造成的影响,并对目前离子推力器设置的工作启动流程可能造成的打火风险进行了预估。结果显示:三... 详细信息

采用有限元仿真(FEM)与地面热平衡试验验证相结合的方法,计算并模拟了30 cm离子推力器处于在轨环境时,有、无主动热控对三栅极相对位移变化造成的影响,并对目前离子推力器设置的工作启动流程可能造成的打火风险进行了预估。结果显示:三栅极组件的热形变方向均为法向方向,且栅极中心区域的间距最小;在-269℃在轨极限环境温度下,推力器在5 kW工作模式下温度平衡后的屏栅与加速栅最大热态间距为0.14 mm,加速栅和减速栅则已发生贴合;在受太阳辐照以及卫星帆板恒温边界的影响下,栅面最低初始温度为-102℃;当推力器主动热控保证温控点为20℃时,栅面最低启动温度为-25℃,且推力器工作8000s后,屏栅与加速栅、加速栅与减速栅的最小间距分别稳定在0.25 mm和0.20 mm;当推力器主动热控保证温控点为50℃时,推力器工作9000s后,屏栅与加速栅、加速栅和减速栅最小间距分别稳定在0.31 mm和0.30 mm,能够满足0.25 mm的栅极安全打火间距要求。

关键词：离子推力器三栅极组件空间在轨环境栅极间距变化

Impact of the Early Stage of the COVID-19 Pandemic on Smoking Cessation in Beijing

在线全文

学校读者我要写书评

暂无评论

Biomedical and Environmental Sciences 2023年第5期36卷 452-457页

作者： wang Yao LI Xing ming School of Public Health Capital Medical UniversityBeijing 100069China

Since the COVID-19 pandemic broke out, both the Chinese national government and the Beijing municipal government issued prevention and control measures to contain the spread of the disease. The Chinese Center for Disease Control and Prevention promptly introduced the Protocol for the Prevention and Control of COVID-19 to regulate the detection of infection and manage the close contact of those infected, while promptly updating the records.

关键词： prompt prevention Impact

Clinical characteristics, pathogenesis, treatment and prognosis of osteomyelitis in children: a retrospective study from a single center

在线全文

学校读者我要写书评

暂无评论

World Journal of Emergency Medicine 2023年第4期14卷 312-316页

作者： Shuang wang ming wang Botao Ning wanglin Zhang Department of Pediatric Intensive Care Unit Shanghai Children's Medical CenterShanghai Jiao Tong University School of MedicineShanghai 200127China Department of Orthopedics Shanghai Children's Medical CenterShanghai Jiao Tong University School of MedicineShanghai 200127China

Osteomyelitis is a common musculoskeletal infection in children,and the acute and chronic osteomyelitis are the two most common type.Acute osteomyelitis affects about 1 in every 5,000 to 10,000 people and is more comm... 详细信息

关键词： myelitis Acute pathogenesis

Slip distribution inversion of seismic sub-fault dip iteration using gradient based optimizer algorithm

在线全文

学校读者我要写书评

暂无评论

Geodesy and Geodynamics 2024年第2期15卷 114-121页

作者： Leyang wang Han Li ming Pang Key Laboratory of Mine Environmental Monitoring and Improving Around Poyang Lake of Ministry of Natural Resources East China University of TechnologyNanchang 330013China School of Surveying and Geoinformation Engineering East China University of TechnologyNanchang 330013China College of Resources and Environment Shandong Agricultural UniversityTaian 271018China

This paper considers setting different dips for different sub-faults to fit the actual rupture situation based on the fault rupture of the 2013 Lushan M_(S)7.0 earthquake.Meanwhile,combined with the coseismic GNSS data of the Lushan earthquake,the source parameters and sliding distribution of the Lushan earthquake fault are inversed.Firstly,we use the gradient based optimizer(GBO)in nonlinear inversion to obtain the source parameters of this seismic fault.The inversion results indicate that the strike of the fault is 206.52°,the dip is 44.10°,the length is 21.92 km,and the depth is 12.79 km.To refine the sliding distribution of the seismic fault,the seismic fault is divided into 3×3 sub-faults.Then,we fix the central sub-fault dip of 44.10°;the dip of other sub-faults is obtained by iteration.After that,the model is further divided into a fault layer model composed of 23×19 sub fault slices,and using the Matlab fitting function is used to fit the dip of the 23×19 sub faults.Finally,the Lushan seismic fault plane is established as a shovel structure with steep upper and gentle lower,steep south and gentle north.The slip distribution inversion results indicate that the depth of the slip peak is 13 km,the corresponding maximum slip momentum is 0.67 m,the seismic moment is 1.10×10^(19)N·m and the corresponding moment magnitude is MW6.66.The results above are consistent with the research results of seismology.

关键词： Gradient basedoptimizer(GBO) Lushan earthquake Non-planefault model Slid distribution

Impact toughness variations of EH36 weld metal treated by CaF_(2)–SiO_(2)–MnO submerged arc welding flux

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research(International) 2023年第9期30卷 1873-1878页

作者： ming Zhong Da-ming Guo Somnath Basu Cong wang Key Laboratory for Ecological Metallurgy of Multimetallic Mineral(Ministry of Education) Northeastern UniversityShenyang 110819LiaoningChina School of Metallurgy Northeastern UniversityShenyang 110819LiaoningChina The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan 430081HubeiChina Department of Metallurgical Engineering and Materials Science Indian Institute of Technology BombayMumbai 400076MaharashtraIndia

Fused ternary CaF_(2)–SiO_(2)–MnO fluxes have been manufactured and applied to join EH36 shipbuilding steel under high heat input submerged arc welding.Five fluxes have been designed to clarify the effect of MnO content in CaF_(2)–SiO_(2)–MnO flux on the impact toughness of the weld metal,with the added amount of MnO from 10 to 50 wt.%at the expense of CaF_(2).With the increase in MnO content,the Charpy impact energy increases first and then decreases,experiencing a maximum value at 30 wt.%MnO.Microstructure of the weld metals has also been studied to account for impact toughness variations.It has been demonstrated that the highest acicular ferrite volume fraction in the weld metal is achieved at 30 wt.%MnO,which is concurrent to the maximum value of Charpy impact energy.It is believed that the Mn and O content variations in the weld metal contribute synergistically to such an interesting phenomenon.

关键词： Submerged arc welding CaF_(2)–SiO_(2)–MnO flux Shipbuilding steel Impact toughness Microstructure

Theoretical study on the pressurization characteristics of disc-seal single screw pump used in high viscosity oily sludge conveying field

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Petroleum Science 2022年第3期19卷 1361-1370页

作者： Zeng-Li wang Hou-Wei Shi Shu-Yu wang Zong-ming wang Mu-ming Hao Jun wang National Engineering Laboratory of Offshore Geophysical and Exploration Equipment China University of Petroleum(East China) College of New Energy China University of Petroleum(East China)

The disc-seal single screw pump(DSSP)used in the field of high viscosity oily sludge transport has a huge advantage.However,there is no research on the pressurization characteristics of the DSSP at present,which makes its application limited.In view of this,the pressurization process mathematical model of the DSSP was established based on the geometric model of the pump.By using this model,the pressurization characteristics of DSSP and the influence of working parameters on the pressurization process were studied combined with the principle of back-flow pressurization.Analysis results show that the instantaneous pressurization process could be realized mainly depending on the reflux pressurization from the outlet chamber to the pressurization chamber when the screw rotor rotating angle is located at-5°to+5°.The pressure in the pressurization chamber will increase with the increase of working parameters which include inlet pressure,outlet pressure,screw rotation velocity and dynamic viscosity of fluid medium in the area of flow-back pressurization.The screw rotation velocity and the viscosity of the conveying medium have significant effects on the peak pressure in the pressurization chamber,and the peak pressure in the pressurization chamber is proportional to the screw rotation velocity and the dynamic viscosity coefficient of the conveying medium.The proportional coefficient between the peak pressure and the screw rotation velocity is 6.29×10~4.The proportional coefficient between the peak pressure and the dynamic viscosity of the conveying medium is 6.28×10~6.

关键词： Disc-seal single screw pump Oily sludge Pressurization characteristics Mathematical model Reflux pressurization

Close relative motion on distant retrograde orbits

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2023年第3期36卷 335-356页

作者： Chihang YANG ming wang Hao ZHANG University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of Space Utilization Technology and Engineering Center for Space UtilizationChinese Academy of SciencesBeijing 100094China

Distant Retrograde Orbits(DROs)in the Earth-Moon system have great potential to support varieties of missions due to the favorable stability and orbital positions.Thus,the close relative motion on DROs should be analyzed to design formations to assist or extend the DRO missions.However,as the reference DROs are obtained through numerical methods,the close relative motions on DROs are non-analytical,which severely limits the design of relative trajectories.In this paper,a novel approach is proposed to construct the analytical solution of bounded close relative motion on DROs.The linear dynamics of relative motion on DRO is established at first.The preliminary forms of the general solutions are obtained based on the Floquet theory.And the general solutions are classified as different modes depending on their periodic components.A new parameterization is applied to each mode,which allows us to explore the geometries of quasi-periodic modes in detail.In each mode,the solutions are integrated as a uniform expression and their periodic components are expanded as truncated Fourier series.In this way,the analytical bounded relative motion on DRO is obtained.Based on the analytical expression,the characteristics of different modes are comprehensively analyzed.The natural periodic mode is always located on the single side of the target spacecraft on DRO and is appropriate to be the parking orbits of the rendezvous and docking.On the basis of quasi-periodic modes,quasi-elliptical fly-around relative trajectories are designed with the assistance of only two impulses per period.The fly-around formation can support observations to targets on DRO from multiple viewing angles.And the fly-around formation is validated in a more practical ephemeris model.

关键词： Distant retrograde orbits Ephemeris model Floquet theory Formation flight Relative motion Spacecraft Three-body problem Transfer singularity

Visible Light-Induced[3+2]Annulation Reaction of Alkenes with Vinyl Azides:Direct Synthesis of Functionalized Pyrroles

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 2024年第2期42卷 151-156页

作者： ming Yang Xin-Yu wang Jie wang Yu-Long Zhao Jilin Province Key Laboratory of Organic Functional Molecular Design&Synthesis Faculty of ChemistryNortheast Normal UniversityChangchunJilin 130024China

A photocatalytic[3+2]annulation of alkenes with vinyl azides was developed under irradiation by visible light in the presence of organic dye photocatalysts.Broad substrate scope and high functional group tolerance were demonstrated by more than 50 examples.The reaction provides a novel and efficient method for the synthesis of polyfunctionalized pyrroles under very mild metal-free conditions without other additives.

关键词： Photocatalysis Vinyl azides Alkenes Pyrroles Annulation Radical reactions