检索结果-南通市图书馆

在线全文

学校读者我要写书评

暂无评论

Fighting Back

China Weekly 2024年第6期 18-21页

作者： liu xiangnan 不详

Zhang Yimou's latest film draws the spotlight on self-defense cases in China,where after decades of conservative rulings,a mix of public outcry and new criminal law guidelines has led to a surge in acquittals fordefen... 详细信息

关键词： seeking conservative law

Ultra Dense Satellite-Enabled 6G Networks:Resource Optimization and Interference Management

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

中国通信:英文版 2023年第10期20卷 262-275页

作者： xiangnan liu Haijun Zhang Min Sheng Wei Li Saba Al-Rubaye Keping Long School of Computer&Communication Engineering University of Science and Technology BeijingBeijing 100083China Beijing Engineering and Technology Research Center for Convergence Networks and Ubiquitous Services University of Science and Technology BeijingBeijing 100083China School of Telecommunications Engineering Xidian UniversityXi’an 710071China State Radio Monitoring Center of China Beijing 100037China School of Aerospace Transport and Manufacturing Cranfield UniversityMK430ALUK

With the evolution of the sixth generation(6G)mobile communication technology,ample attention has gone to the integrated terrestrial-satellite networks.This paper notes that four typical application scenarios of integrated terrestrial-satellite networks are integrated into ultra dense satellite-enabled 6G networks architecture.Then the subchannel and power allocation schemes for the downlink of the ultra dense satellite-enabled 6G heterogeneous networks are introduced.Satellite mobile edge computing(SMEC)with edge caching in three-layer heterogeneous networks serves to reduce the link traffic of networks.Furthermore,a scheme for interference management is presented,involving quality-of-service(QoS)and co-tier/cross-tier interference constraints.The simulation results show that the proposed schemes can significantly increase the total capacity of ultra dense satellite-enabled 6G heterogeneous networks.

关键词： satellite-enabled 6G networks network architecture resource optimization interference management

Ultrasmall Pt_(2)Sr alloy nanoparticles as efficient bifunctional electrocatalysts for oxygen reduction and hydrogen evolution in acidic media

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2022年第1期31卷 315-322,I0009页

作者： xiangnan liu Shaoyun Hao Guokui Zheng Zhiwei Su Yahui Wang Qiqi Wang Lecheng Lei Yi He Xingwang Zhang Key Laboratory of Biomass Chemical Engineering of Ministry of Education College of Chemical and Biological Engineering Zhejiang UniversityHangzhou 310027ZhejiangChina Institute of Zhejiang University-Quzhou Quzhou 324000ZhejiangChina

Electrocatalytic oxygen reduction reaction(ORR)and hydrogen evolution reaction(HER)in acidic media are vital for the applications of renewable energy electrolyzers.However,the low mass activity of noble Pt urgently needs to be improved due to the strong binding energetics of oxygen species(*O)with Pt sites.Here we report fine PtxSr alloy(-2 nm)supported on N-doped carb on(NC)pyrolyzing from ZIF-8 as bifunctional electrocatalysts toward ORR and HER in acidic media.The representative Pt_(2)Sr/NC exhibits an onset potential of 0.94 V vs.RHE and half-wave potential of 0.84 V toward ORR,and a low over-potential of 27 mV(10 mA cm^(-2))toward HER,respectively.Significantly,the mass activities of Pt_(2)Sr/NC are 6.2 and 2.6 times higher than that of Pt/C toward ORR(at 0.9 V)and HER(at-30 mV),respectively.Simultaneously,Pt_(2)Sr/NC possesses a retention rate of 90.97%toward acidic ORR after 35000 s of continuous operation.Through density functional theory(DFT)calculations and X-ray photoelectron spectroscopy analysis,the incorporation of Sr into Pt forming Pt_(2)Sr alloy redistributes the electronic structures of Pt-Pt bonds,changing the rate-determining step for the ORR on Pt sites from the formation of*OH from*O to the generation of*OOH along with decreasing the energy barrier,which is also confirmed by the downshift of d band center.Meanwhile,the downshift of d band center also leads to the optimization of the adsorption energy(H*)with Pt,significantly improving Pt_(2)Sr/NC toward HER.

关键词： Acidic media Alloy Oxygen reduction reaction Hydrogen evolution reaction Density functional theory

An autoencoder-based model for forest disturbance detection using Landsat time series data

在线全文

学校读者我要写书评

暂无评论

International Journal of Digital Earth 2021年第9期14卷 1087-1102页

作者： Gaoxiang Zhou Ming liu xiangnan liu Department of Information and Engineering Engineering University of People’s Armed PoliceXi’anPeople’s Republic of China School of Land Engineering Chang’An UniversityXi’anPeople’s Republic of China School of Information and Engineering China University of GeosciencesBeijingPeople’s Republic of China

Monitoring and classifying disturbed forests can provide information support for not only sustainable forest management but also global carbon sequestration assessments.In this study,we propose an autoencoder-based model for forest disturbance detection,which considers disturbances as anomalous events in forest temporal trajectories.The autoencoder network is established and trained to reconstruct intact forest trajectories.Then,the disturbance detection threshold is derived by Tukey’s method based on the reconstruction error of the intact forest trajectory.The assessment result shows that the model using the NBR time series performs better than the NDVIbased model,with an overall accuracy of 90.3%.The omission and commission errors of disturbed forest are 7%and 12%,respectively.Additionally,the trained NBR-based model is implemented in two test areas,with overall accuracies of 87.2%and 86.1%,indicating the robustness and scalability of the model.Moreover,comparing three common methods,the proposed model performs better,especially for intact forest detection accuracy.This study provides a novel and robust approach with acceptable accuracy for forest disturbance detection,enabling forest disturbance to be identified in regions with limited disturbance reference data.

关键词： Forest disturbance detection Autoencoder network Unsupervised learning Landsat time series

Overview of deep space laser communication

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

Science China(Information Sciences) 2018年第4期61卷 7-18页

作者： Weiren WU Ming CHEN Zhe ZHANG xiangnan liu Yuhui DONG School of Aerospace Engineering Beijing Institute of Technology Beijing Research Institute of Telemetry

The deep space probe is a vital technology for observing and exploring the universe. It is thus intensifying as an aerospace research focus on an international scale. Despite improving the frequency band,the conventional microwave communication technique has difficulty satisfying the increased demand for the enormous volume of scientific data returning to the Earth. With a carrier frequency that is several orders of magnitude higher than the microwave, free-space optical communication is a robust and promising method for achieving both high bit rates and long distances in deep space communication. In this article, the history of this technology is summarized and the objective laws are formulated, while key techniques and development trends are analyzed. Finally, useful concepts and suggestions are proposed for the development of deep space laser communication in China.

关键词： deep space communication deep space observation development process free space communication laser communication

融合遥感时间序列时空谱信息的森林扰动检测与归因研究进展

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

遥感学报 2024年第3期28卷 558-575页

作者：吴伶刘湘南刘美玲张廷伟杨宝文徐宇岐中国地质大学(北京)信息工程学院北京100083

遥感时间序列蕴含自然因素和人类活动等不同驱动因子导致的森林组成、结构、功能变化及其差异信息,能有效提升对森林演替过程、发展态势及其驱动和响应机制的理解能力。本文系统评述了融合遥感时间序列时空谱信息的森林扰动检测与归因... 详细信息

遥感时间序列蕴含自然因素和人类活动等不同驱动因子导致的森林组成、结构、功能变化及其差异信息,能有效提升对森林演替过程、发展态势及其驱动和响应机制的理解能力。本文系统评述了融合遥感时间序列时空谱信息的森林扰动检测与归因研究进展。从数据、特征、算法等多个角度阐述了当前森林扰动检测进展:(1)数据角度。介绍了面向稠密和稀疏时间序列等不同观测频次的变化检测方法;(2)特征角度。归纳了森林扰动光谱响应特征和多光谱特征集成变化检测策略,总结了面向森林扰动检测的时序与空间特征融合方式;(3)算法角度。介绍了并行和串行两种多算法集成策略,描述了面向森林低强度扰动的变化检测算法研究进展。此外,森林扰动归因的本质是面向森林多类型扰动分类问题,本文在分别按照时间顺序和特征维度归纳作为森林扰动归因输入的归因特征的基础上,总结了基于遥感时间序列时空谱和地形特征融合的森林多类型扰动归因方法。最后,本文分析了森林扰动遥感监测目前存在的问题,并对未来研究方向进行了展望,以期为融合遥感时间序列时空谱信息的变化检测和归因研究提供借鉴。

关键词：森林扰动遥感时间序列时空谱信息特征融合扰动检测扰动归因

红花Aux/IAA基因家族鉴定及盐胁迫响应分析

在线全文

学校读者我要写书评

暂无评论

江苏农业科学 2024年第6期52卷 68-76页

作者：刘湘楠胡祥祥乔梦燚周丹宁朱畇昊河南中医药大学药学院河南郑州450046 呼吸疾病诊疗与新药研发河南省协同创新中心河南郑州450046

为了对红花Aux/IAA基因家族进行生物信息学分析,研究该基因在红花生长发育中的调控作用,利用生物信息学方法,在红花全基因组中鉴定出28个Aux/IAA基因。根据其与拟南芥Aux/IAA基因的系统发育关系,使用MEGA 7.0做出系统发育进化树。经理... 详细信息

为了对红花Aux/IAA基因家族进行生物信息学分析,研究该基因在红花生长发育中的调控作用,利用生物信息学方法,在红花全基因组中鉴定出28个Aux/IAA基因。根据其与拟南芥Aux/IAA基因的系统发育关系,使用MEGA 7.0做出系统发育进化树。经理化性质分析,红花Aux/IAA蛋白为亲水性蛋白,且79%位于细胞核中,大多数红花Aux/IAA蛋白表现为偏酸性;经聚类分析,将红花Aux/IAA基因分为5个亚族。基因结构分析表明,所有基因均含有1~9个内含子。这些基因在红花的9条染色体上非均匀地分布,其中9号染色体上分布最多,有7个Aux/IAA基因。红花Aux/IAA基因在不同发育期及不同外源激素处理下表达量各不相同。对保守基序作图分析发现,大部分红花Aux/IAA蛋白具有4个共同的保守基序,分别为motif 1、motif 2、motif 3、motif 4,qRT-PCR结果表明,不同浓度盐胁迫处理24 h后,基因CtAux/IAA1相对表达量呈上调趋势,推测此基因可能与提高红花抗盐胁迫能力有关。本研究结果将有助于了解红花Aux/IAA基因家族在生长发育过程中的功能并筛选优良基因。

关键词：红花 Aux/IAA基因家族生物信息学分析盐胁迫

基于改进波形聚类方法的复合河道砂体沉积微相预测--以渤海A油田为例

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

石油物探 2024年第2期63卷 370-379页

作者：董建华杜昕伊硕周建楠刘向南中海油研究总院有限责任公司北京100020

渤海新近系河湖过渡带复合河道砂体叠置关系复杂、相带变化剧烈,利用传统地震属性划分沉积微相多解性较强。提出了改进振幅谱距离-K中心聚类方法并将其应用于复合河道砂体沉积微相预测。方法包括两个方面:①以测井标定沉积微相对应的典... 详细信息

渤海新近系河湖过渡带复合河道砂体叠置关系复杂、相带变化剧烈,利用传统地震属性划分沉积微相多解性较强。提出了改进振幅谱距离-K中心聚类方法并将其应用于复合河道砂体沉积微相预测。方法包括两个方面:①以测井标定沉积微相对应的典型波形作为初始聚类中心以及聚类中心更新过程中的约束条件;②利用振幅谱距离评价波形之间的差异,进一步提升波形聚类精度。根据渤海新近系A油田地质条件设计复合河道砂体三维模型,模型试验结果证实改进后的方法微相预测准确率达95%,相比传统K均值聚类算法精度提升15%,较好地区分了泥岩、单期河道边部、单期河道主体、河道边部叠置、河道边部与主体叠置、河道主体叠置(或多期叠置)共6种河道不同部位或叠置样式。利用改进后的方法指导A油田10个砂体沉积微相划分,将大型砂体S沉积微相划分为分流河道、河口坝、席状砂、决口河道、分流间湾、天然堤6类,指导开发方案中优先动用分流河道、河口坝等优势微相的地质储量,证明了方法的实用价值。

关键词：波形聚类振幅谱距离复合河道沉积微相河湖过渡带渤海新近系

Effect of porosities of bilayered porous scaffolds on spontaneous osteochondral repair in cartilage tissue engineering

在线全文

学校读者我要写书评

暂无评论

Regenerative Biomaterials 2015年第1期2卷 9-19页

作者： Zhen Pan Pingguo Duan xiangnan liu Huiren Wang Lu Cao Yao He Jian Dong Jiandong Ding State Key Laboratory of Molecular Engineering of Polymers Department of Macromolecular ScienceAdvanced Materials LaboratoryFudan UniversityShanghai 200433China Department of Orthopaedic Surgery The First Affiliated Hospital of Nanchang UniversityNanchang330006China Department of Orthopaedic Surgery Zhongshan HospitalState Key Laboratory of Molecular Engineering of PolymersFudan UniversityShanghai 200032China

Poly(lactide-co-glycolide)-bilayered scaffolds with the same porosity or different ones on the two layers were fabricated,and the porosity effect on in vivo repairing of the osteochondral defect was examined in a comparative way for the first time.The constructs of scaffolds and bone marrow-derived mesenchymal stem cells were implanted into pre-created osteochondral defects in the femoral condyle of New Zealand white rabbits.After 12 weeks,all experimental groups exhibited good cartilage repairing according to macroscopic appearance,cross-section view,haematoxylin and eosin staining,toluidine blue staining,immunohistochemical staining and real-time polymerase chain reaction of characteristic genes.The group of 92%porosity in the cartilage layer and 77%porosity in the bone layer resulted in the best efficacy,which was understood by more biomechanical mimicking of the natural cartilage and subchondral bone.This study illustrates unambiguously that cartilage tissue engineering allows for a wide range of scaffold porosity,yet some porosity group is optimal.It is also revealed that the biomechanical matching with the natural composite tissue should be taken into consideration in the design of practical biomaterials,which is especially important for porosities of a multi-compartment scaffold concerning connected tissues.

关键词： bilayered scaffold porosity mesenchymal stem cell osteochondral defect PLGA cartilage tissue engineering