期刊文献+
共找到590篇文章
< 1 2 30 >
每页显示 20 50 100
北极航道跟航模式下船-船碰撞几何概率计算模型
1
作者 罗佳炫 罗小芳 +1 位作者 昝英飞 ZHANG Ningbo 《船舶工程》 北大核心 2025年第8期70-76,共7页
[目的]随着北极航运业的快速发展,商船编队航行时船-船碰撞事故频发的问题成为各界关注的焦点,其中跟航模式下船-船碰撞事故发生概率是关键问题之一。[方法]考虑船舶、环境和人员等因素,基于跟驰理论构建了考虑碎冰阻力影响的船-船碰撞... [目的]随着北极航运业的快速发展,商船编队航行时船-船碰撞事故频发的问题成为各界关注的焦点,其中跟航模式下船-船碰撞事故发生概率是关键问题之一。[方法]考虑船舶、环境和人员等因素,基于跟驰理论构建了考虑碎冰阻力影响的船-船碰撞几何模型;基于可靠指标理论,将跟航模式下制动后的船-船状态划分为危险、极限与安全状态,推导了跟航安全的极限状态方程,进而建立了跟航模式下船-船碰撞几何概率计算模型。[结果]基于永盛轮北极航行案例数据开展分析,结果表明:所构建的模型能够有效评估船-船碰撞事故发生概率,船-船碰撞概率与海冰密集度、驾驶员反应时长成正比,而与船间安全余量呈反比。[结论]该碰撞概率计算模型可为跟航模式下的安全管理提供坚实的理论支持和决策依据。 展开更多
关键词 碰撞概率 跟航模式 船-船碰撞 几何概率
原文传递
UV-assisted ratiometric fiuorescence sensor for one-pot visual detection of Salmonella 被引量:1
2
作者 Ren Shen Yanmei Fang +4 位作者 Chunxiao Yang Quande Wei Pui-In Mak Rui P.Martins Yanwei Jia 《Chinese Chemical Letters》 2025年第4期593-599,共7页
Rapid diagnosis of Salmonella is crucial for the effective control of food safety incidents, especially in regions with poor hygiene conditions. Polymerase chain reaction(PCR), as a promising tool for Salmonella detec... Rapid diagnosis of Salmonella is crucial for the effective control of food safety incidents, especially in regions with poor hygiene conditions. Polymerase chain reaction(PCR), as a promising tool for Salmonella detection, is facing a lack of simple and fast sensing methods that are compatible with field applications in resource-limited areas. In this work, we developed a sensing approach to identify PCR-amplified Salmonella genomic DNA with the naked eye in a snapshot. Based on the ratiometric fiuorescence signals from SYBR Green Ⅰ and Hydroxyl naphthol blue, positive samples stood out from negative ones with a distinct color pattern under UV exposure. The proposed sensing scheme enabled highly specific identification of Salmonella with a detection limit at the single-copy level. Also, as a supplement to the intuitive naked-eye visualization results, numerical analysis of the colored images was available with a smartphone app to extract RGB values from colored images. This work provides a simple, rapid, and user-friendly solution for PCR identification, which promises great potential in molecular diagnosis of Salmonella and other pathogens in field. 展开更多
关键词 Bacteria detection Polymerase chain reaction Naked-eye visualization Ratiometric fiuorescence Smartphone app
原文传递
基于试验验证下的FRP筋与混凝土粘结滑移界面关系有限元模型的建立方法
3
作者 张羽 傅丰 +1 位作者 郑吉丰 陈宇飞 《建筑结构》 北大核心 2025年第12期56-66,共11页
为得到一种较为准确的纤维增强复合材料筋(FRP筋)与混凝土粘结滑移界面关系有限元模型的建立方法,进行了FRP筋混凝土试件的中心拉拔试验。运用通用有限元软件ABAQUS建立精细化的有限元模型,模拟FRP筋混凝土静力拉拔试验。通过在ABAQUS... 为得到一种较为准确的纤维增强复合材料筋(FRP筋)与混凝土粘结滑移界面关系有限元模型的建立方法,进行了FRP筋混凝土试件的中心拉拔试验。运用通用有限元软件ABAQUS建立精细化的有限元模型,模拟FRP筋混凝土静力拉拔试验。通过在ABAQUS中设置摩擦力、过盈量、粘结力三种作用模块模拟出FRP筋与混凝土界面粘结力中的表面摩擦力、机械咬合力和化学胶结力作用。按照与试验相同的加载条件和试验工况在ABAQUS模型中设置荷载条件后运行模型,并提取出模拟结果后与试验结果相对照。结果表明:模拟结果与试验结果吻合性较好,模拟破坏模态与试验破坏模态亦相近。验证了FRP筋与混凝土粘结滑移界面关系有限元模型建立方法的正确性和FRP筋与混凝土界面关系参数取值的正确性。 展开更多
关键词 FRP筋 粘结滑移性能 拉拔试验 数值模拟 摩擦 过盈量 粘结力
在线阅读 下载PDF
欧洲TTF期货多因子交易策略分析
4
作者 茹毅鹏 《当代石油石化》 2025年第7期24-28,共5页
欧洲天然气价格日益成为全球天然气市场风向标。深入分析欧洲天然气市场的影响因素,采用多因子交易策略研究荷兰产权转让设施(TTF)天然气价格指数的变化趋势,从供需基本面和金融技术面两大视角出发,系统梳理影响TTF天然气价格波动的多... 欧洲天然气价格日益成为全球天然气市场风向标。深入分析欧洲天然气市场的影响因素,采用多因子交易策略研究荷兰产权转让设施(TTF)天然气价格指数的变化趋势,从供需基本面和金融技术面两大视角出发,系统梳理影响TTF天然气价格波动的多种变量,全面把握价格动态。研究发现,库存变化对TTF天然气价格的影响在10天周期内最为显著,煤炭价格与TTF天然气价格的正向替代关系在50天周期内最为明显,而天气和供应变化分别在20天和100天周期内影响显著。在金融技术面因子中,期限结构和基差动量因子在5天周期内影响突出,亚欧价差因子在20天周期内影响显著。基于此剖析了2024年以来TTF天然气价格波动的原因,并为2025年与欧洲的天然气交易提出策略建议。 展开更多
关键词 天然气 多因子 欧洲 天然气价格 交易策略
在线阅读 下载PDF
Multiscale modeling of thermo-hydromechanical behavior of clayey rocks and application to geological disposal of radioactive waste
5
作者 Jianfu Shao Zhan Yu Minh-Ngoc Vu 《Journal of Rock Mechanics and Geotechnical Engineering》 2025年第1期1-19,共19页
This work is devoted to numerical analysis of thermo-hydromechanical problem and cracking process in saturated porous media in the context of deep geological disposal of radioactive waste.The fundamental background of... This work is devoted to numerical analysis of thermo-hydromechanical problem and cracking process in saturated porous media in the context of deep geological disposal of radioactive waste.The fundamental background of thermo-poro-elastoplasticity theory is first summarized.The emphasis is put on the effect of pore fluid pressure on plastic deformation.A micromechanics-based elastoplastic model is then presented for a class of clayey rocks considered as host rock.Based on linear and nonlinear homogenization techniques,the proposed model is able to systematically account for the influences of porosity and mineral composition on macroscopic elastic properties and plastic yield strength.The initial anisotropy and time-dependent deformation are also taken into account.The induced cracking process is described by using a non-local damage model.A specific hybrid formulation is proposed,able to conveniently capture tensile,shear and mixed cracks.In particular,the influences of pore pressure and confining stress on the shear cracking mechanism are taken into account.The proposed model is applied to investigating thermo-hydromechanical responses and induced damage evolution in laboratory tests at the sample scale.In the last part,an in situ heating experiment is analyzed by using the proposed model.Numerical results are compared with experimental data and field measurements in terms of temperature variation,pore fluid pressure change and induced damaged zone. 展开更多
关键词 Radioactive waste Geological disposal Thermo-hydromechanical coupling Clayey rocks Damage and cracking Phase-field modeling
在线阅读 下载PDF
Pivotal role of digital twins in the metaverse:A review
6
作者 Siva Sai Pulkit Sharma +1 位作者 Aanchal Gaur Vinay Chamola 《Digital Communications and Networks》 2025年第5期1343-1355,共13页
The ascent of the metaverse signifies a profound transformation in our digital landscape, ushering in a complex network of interlinked virtual domains and digital spaces. In this burgeoning metaverse, a paradigm shift... The ascent of the metaverse signifies a profound transformation in our digital landscape, ushering in a complex network of interlinked virtual domains and digital spaces. In this burgeoning metaverse, a paradigm shift is seen in how people engage, collaborate, and become immersed in digital environments. An especially intriguing concept taking root within this metaverse landscape is that of digital twins. Initially rooted in industrial and Internet of Things(IoT) contexts, digital twins are now making their mark in the metaverse, presenting opportunities to elevate user experiences, introduce novel dimensions of interaction, and seamlessly bridge the divide between the virtual and physical realms. Digital twins, conceived initially to replicate physical entities in real-time, have transcended their industrial origins in this new metaverse context. They no longer solely replicate physical objects but extend their domain to encompass digital entities, avatars, virtual environments, and users. Despite the vital contributions of digital twins in the metaverse, there has been no research that has explored the applications and scope of digital twins in the metaverse comprehensively. However, there are a few papers focusing on some particular applications. Addressing this research gap, we present an in-depth review of the pivotal role of application digital twins in the metaverse. We present 15 digital twin applications in the metaverse, ranging from simulation and training to emergency preparedness. This study outlines the critical limitations of integrating digital twins and metaverse and several future research directions. 展开更多
关键词 Digital twins Metaverse APPLICATIONS User experience LIMITATIONS
在线阅读 下载PDF
证据图谱的过去、现在与未来
7
作者 李艳飞 李美萱 +11 位作者 魏志鹏 郭丽萍 GHOGOMU Elizabeth KHALIL Hanan CAMPBELL Fiona GAARDER Marie NDUKU Promise M WHITE Howard WELCH Vivian 后亮瑛 杨克虎 李秀霞 《兰州大学学报(医学版)》 2025年第11期22-28,共7页
证据图谱作为揭示研究现状及证据差距的重要方法,为政策制定和科学研究提供了重要参考,受到Campbell协作网、国际影响性评估组织以及兰州大学循证医学中心等国内外学术组织和机构的高度重视。本研究系统梳理并深入分析了证据图谱的最新... 证据图谱作为揭示研究现状及证据差距的重要方法,为政策制定和科学研究提供了重要参考,受到Campbell协作网、国际影响性评估组织以及兰州大学循证医学中心等国内外学术组织和机构的高度重视。本研究系统梳理并深入分析了证据图谱的最新发展动态,重点介绍了证据图谱的起源、术语、定义、制作流程和报告规范等方面的最新进展,并展望了研究者在未来开展体现证据图谱特性的高质量研究、推动证据图谱从研究向实践应用转化、构建高水平国际合作交流平台以及促进证据图谱的智能化发展等方面的前景,以期为中国相关领域研究的开展提供科学依据和有益借鉴。 展开更多
关键词 证据图谱 证据图 证据差距图 方法学 研究优先级
暂未订购
Visual Perception and Adaptive Scene Analysis with Autonomous Panoptic Segmentation
8
作者 Darthy Rabecka V Britto Pari J Man-Fai Leung 《Computers, Materials & Continua》 2025年第10期827-853,共27页
Techniques in deep learning have significantly boosted the accuracy and productivity of computer vision segmentation tasks.This article offers an intriguing architecture for semantic,instance,and panoptic segmentation... Techniques in deep learning have significantly boosted the accuracy and productivity of computer vision segmentation tasks.This article offers an intriguing architecture for semantic,instance,and panoptic segmentation using EfficientNet-B7 and Bidirectional Feature Pyramid Networks(Bi-FPN).When implemented in place of the EfficientNet-B5 backbone,EfficientNet-B7 strengthens the model’s feature extraction capabilities and is far more appropriate for real-world applications.By ensuring superior multi-scale feature fusion,Bi-FPN integration enhances the segmentation of complex objects across various urban environments.The design suggested is examined on rigorous datasets,encompassing Cityscapes,Common Objects in Context,KITTI Karlsruhe Institute of Technology and Toyota Technological Institute,and Indian Driving Dataset,which replicate numerous real-world driving conditions.During extensive training,validation,and testing,the model showcases major gains in segmentation accuracy and surpasses state-of-the-art performance in semantic,instance,and panoptic segmentation tasks.Outperforming present methods,the recommended approach generates noteworthy gains in Panoptic Quality:+0.4%on Cityscapes,+0.2%on COCO,+1.7%on KITTI,and+0.4%on IDD.These changes show just how efficient it is in various driving circumstances and datasets.This study emphasizes the potential of EfficientNet-B7 and Bi-FPN to provide dependable,high-precision segmentation in computer vision applications,primarily autonomous driving.The research results suggest that this framework efficiently tackles the constraints of practical situations while delivering a robust solution for high-performance tasks involving segmentation. 展开更多
关键词 Panoptic segmentation multi-scale features efficient net-B7 Feature Pyramid Network
在线阅读 下载PDF
Transformers for Multi-Modal Image Analysis in Healthcare
9
作者 Sameera V Mohd Sagheer Meghana K H +2 位作者 P M Ameer Muneer Parayangat Mohamed Abbas 《Computers, Materials & Continua》 2025年第9期4259-4297,共39页
Integrating multiple medical imaging techniques,including Magnetic Resonance Imaging(MRI),Computed Tomography,Positron Emission Tomography(PET),and ultrasound,provides a comprehensive view of the patient health status... Integrating multiple medical imaging techniques,including Magnetic Resonance Imaging(MRI),Computed Tomography,Positron Emission Tomography(PET),and ultrasound,provides a comprehensive view of the patient health status.Each of these methods contributes unique diagnostic insights,enhancing the overall assessment of patient condition.Nevertheless,the amalgamation of data from multiple modalities presents difficulties due to disparities in resolution,data collection methods,and noise levels.While traditional models like Convolutional Neural Networks(CNNs)excel in single-modality tasks,they struggle to handle multi-modal complexities,lacking the capacity to model global relationships.This research presents a novel approach for examining multi-modal medical imagery using a transformer-based system.The framework employs self-attention and cross-attention mechanisms to synchronize and integrate features across various modalities.Additionally,it shows resilience to variations in noise and image quality,making it adaptable for real-time clinical use.To address the computational hurdles linked to transformer models,particularly in real-time clinical applications in resource-constrained environments,several optimization techniques have been integrated to boost scalability and efficiency.Initially,a streamlined transformer architecture was adopted to minimize the computational load while maintaining model effectiveness.Methods such as model pruning,quantization,and knowledge distillation have been applied to reduce the parameter count and enhance the inference speed.Furthermore,efficient attention mechanisms such as linear or sparse attention were employed to alleviate the substantial memory and processing requirements of traditional self-attention operations.For further deployment optimization,researchers have implemented hardware-aware acceleration strategies,including the use of TensorRT and ONNX-based model compression,to ensure efficient execution on edge devices.These optimizations allow the approach to function effectively in real-time clinical settings,ensuring viability even in environments with limited resources.Future research directions include integrating non-imaging data to facilitate personalized treatment and enhancing computational efficiency for implementation in resource-limited environments.This study highlights the transformative potential of transformer models in multi-modal medical imaging,offering improvements in diagnostic accuracy and patient care outcomes. 展开更多
关键词 Multi-modal image analysis medical imaging deep learning image segmentation disease detection multi-modal fusion Vision Transformers(ViTs) precision medicine clinical decision support
在线阅读 下载PDF
Innovative Drug Delivery Systems in Bone Regeneration:Benefits and Applications in Tissue Engineering
10
作者 Samira Farjaminejad Rosana Farjaminejad +1 位作者 Melika Hasani Shahrokh Shojaei 《Journal of Bionic Engineering》 2025年第5期2286-2307,共22页
This article reviews recent advancements,innovative strategies,and the key challenges in Drug Delivery Systems(DDS)for bone regeneration,focusing on tissue engineering.It highlights the limitations of current surgical... This article reviews recent advancements,innovative strategies,and the key challenges in Drug Delivery Systems(DDS)for bone regeneration,focusing on tissue engineering.It highlights the limitations of current surgical interventions forbone regeneration,particularly autogenic bone grafts,and discusses the exploration of alternative materials and methods,including allogeneic and xenogeneic bone grafts,synthetic materials,and biodegradable polymers.The objective is to provide a comprehensive understanding of how contemporary DDS can be optimized and integrated with tissue engineering approaches for more effective bone regeneration therapies.The review explained the mechanisms through which DDS enhance bone repair processes,identifies critical factors influencing their efficacy and safety,and offers an overview of current trends and future perspectives in the field.It emphasizes the need for advanced strategies in bone regeneration that focus on precise control of DDS to address bone conditions such as osteoporosis,trauma,and genetic predispositions leading to fractures. 展开更多
关键词 Drug delivery Bone regeneration Bone repair SCAFFOLD
暂未订购
Performance Evaluation of Dynamic Adaptive Routing(DAR)for Unmanned Aerial Vehicle(UAV)Networks
11
作者 Khadija Slimani Samira Khoulji +1 位作者 Hamed Taherdoost Mohamed Larbi Kerkeb 《Computers, Materials & Continua》 2025年第11期4115-4132,共18页
Reliable and efficient communication is essential for Unmanned Aerial Vehicle(UAV)networks,especially in dynamic and resource-constrained environments such as disaster management,surveillance,and environmental monitor... Reliable and efficient communication is essential for Unmanned Aerial Vehicle(UAV)networks,especially in dynamic and resource-constrained environments such as disaster management,surveillance,and environmental monitoring.Frequent topology changes,high mobility,and limited energy availability pose significant challenges to maintaining stable and high-performance routing.Traditional routing protocols,such as Ad hoc On-Demand Distance Vector(AODV),Load-Balanced Optimized Predictive Ad hoc Routing(LB-OPAR),and Destination-Sequenced Distance Vector(DSDV),often experience performance degradation under such conditions.To address these limitations,this study evaluates the effectiveness of Dynamic Adaptive Routing(DAR),a protocol designed to adapt routing decisions in real time based on network dynamics and resource constraints.The research utilizes the Network Simulator 3(NS-3)platform to conduct controlled simulations,measuring key performance indicators such as latency,Packet Delivery Ratio(PDR),energy consumption,and throughput.Comparative analysis reveals that DAR consistently outperforms conventional protocols,achieving a 20%-30% reduction in latency,a 25% decrease in energy consumption,and marked improvements in throughput and PDR.These results highlight DAR’s ability to maintain high communication reliability while optimizing resource usage in challenging operational scenarios.By providing empirical evidence of DAR’s advantages in highly dynamic UAV network environments,this study contributes to advancing adaptive routing strategies.The findings not only validate DAR’s robustness and scalability but also lay the groundwork for integrating artificial intelligence-driven decision-making and real-world UAV deployment.Future work will explore cross-layer optimization,multi-UAV coordination,and experimental validation in field trials,aiming to further enhance communication resilience and energy efficiency in next-generation aerial networks. 展开更多
关键词 Dynamic adaptive routing(DAR) UAV networks NS-3 simulation packet delivery ratio(PDR) energy efficiency
在线阅读 下载PDF
Real-Time and Energy-Aware UAV Routing:A Scalable DAR Approach for Future 6G Systems
12
作者 Khadija Slimani Samira Khoulji +1 位作者 Hamed Taherdoost Mohamed Larbi Kerkeb 《Computers, Materials & Continua》 2025年第12期4667-4686,共20页
The integration of the dynamic adaptive routing(DAR)algorithm in unmanned aerial vehicle(UAV)networks offers a significant advancement in addressing the challenges posed by next-generation communication systems like 6... The integration of the dynamic adaptive routing(DAR)algorithm in unmanned aerial vehicle(UAV)networks offers a significant advancement in addressing the challenges posed by next-generation communication systems like 6G.DAR’s innovative framework incorporates real-time path adjustments,energy-aware routing,and predictive models,optimizing reliability,latency,and energy efficiency in UAV operations.This study demonstrated DAR’s superior performance in dynamic,large-scale environments,proving its adaptability and scalability for real-time applications.As 6G networks evolve,challenges such as bandwidth demands,global spectrum management,security vulnerabilities,and financial feasibility become prominent.DAR aligns with these demands by offering robust solutions that enhance data transmission while ensuring network reliability.However,obstacles like global route optimization and signal interference in urban areas necessitate further refinement.Future directions should explore hybrid approaches,the integration of machine learning,and comprehensive real-world testing to maximize DAR’s capabilities.The findings underscore DAR’s pivotal role in enabling efficient and sustainable UAV communication systems,contributing to the broader landscape of wireless technology and laying a foundation for the seamless transition to 6G networks. 展开更多
关键词 Dynamic adaptive routing(DAR) energy-aware routing scalability and reliability UAV networks 6G communication systems
在线阅读 下载PDF
Variations in Soil Fungal Community Composition Along A Salinity Gradient in Yellow River Delta,China
13
作者 GUAN Bo LU Guanru +7 位作者 HOU Aixin LYU Xiaofei WANG Zhikang YANG Jisong YU Junbao LIANGZhengwei QIAO Hongjin GUAN Fachun 《Chinese Geographical Science》 2025年第6期1473-1486,共14页
The Yellow River Delta(YRD)of China is one of the most active land-sea interaction deltas in the world.However,due to human activities and climate change,it has undergone significant changes,including the degradation ... The Yellow River Delta(YRD)of China is one of the most active land-sea interaction deltas in the world.However,due to human activities and climate change,it has undergone significant changes,including the degradation of natural wetlands and saltwater intrusion.As an integral part of soil microorganisms,fungi play a crucial role in maintaining and stabilizing the function of wetland ecosystems.To better understand the composition and diversity changes of fungal communities along a salinity gradient in the YRD of China and their relationship with environmental factors,fungal diversity,abundance,and composition in the sediments of four typical vegetation communities spanning from the riverbank to the seaside were investigated.The results showed that the electrical conductivity(EC)increased significantly from the riverbank to the coastal area(P<0.05),but the levels of total nitrogen(TN),total carbon(TC),total sulfur(TS),available phosphorous(AP),and ammonium(NH_(4)^(+)-N)increased in Phragmites australis community and then experienced a significant decrease in Tamarix chinensis community and Suaeda salsa community(P<0.05).The alpha diversity(Shannon and Simpson indices)of the soil fungal community exhibited a negative correlation with EC.There was a significant alteration in the structure of the fungal community,primarily influenced by EC and NO_(3)^(-)-N.Ascomycota was found to be the most abundant phylum,and its relative abundance is positively correlated with pH and TS.The relative abundance of Sordariomycetes,the second-largest class of Ascomycota,reached 38.95%.Salinity was identified as the most important factor driving changes in soil fungal community composition.In summary,the fungal community changed significantly along the salinity gradient,and different environmental factors impacted various tiers of fungal populations differently.The findings of this study lay the groundwork for comprehending soil fungal communities and their primary influencing factors in newly formed wetlands. 展开更多
关键词 soil fungal diversity ASCOMYCOTA salt content plant community Yellow River Delta China
在线阅读 下载PDF
Potential of adaptive co-management in restoring socio-ecological functions of degraded community forests in temperate Himalaya, India
14
作者 Kottapalli Sreenivasa RAO Rajeev Lochan SEMWAL +3 位作者 Ajay MALETHA Sunil NAUTIYAL Rakesh Kumar MAIKHURI Krishna Gopal SAXENA 《Journal of Mountain Science》 2025年第3期860-872,共13页
Scarcity of empirical studies turning the concepts into cost-effective practices is a barrier in achieving the desired trajectory and scale of ecosystem restoration.The present study aimed to assess(i)potential of tre... Scarcity of empirical studies turning the concepts into cost-effective practices is a barrier in achieving the desired trajectory and scale of ecosystem restoration.The present study aimed to assess(i)potential of tree-bamboo-medicinal herb mixed plantation founded on the concept of adaptive comanagement in restoration of degraded community forest in a temperate village of Indian Himalaya and(ii)persistence of offer of local people to voluntarily maintain and expand the trial after its economic benefit/cost ratio became>1.0.Biodiversity,carbon stock and economic benefits were assessed in the restored forest 1,3 and 10 years after 7-year-long funding phase(i.e.,8,10 and 20 years after initial planting in 1991),and other land uses in the village landscape.Significant economic loss occurred from gregarious flowering induced mass mortality of bamboo in the 2nd year after funding phase but it was outweighed by the gain from walnut fruiting.People maintained recovery by transplanting Nepalese Alder(Alnus nepalensis)in gaps.The 20-year-old restored forest land had 17%of aboveground and 75%of belowground carbon stocks,and 39%of flowering species present in the intact forest.Restored forest had only four of the eight Near-threatened/Threatened species present in intact forest.Further,intact forest was monetarily the most efficient land use despite absence of payments for its ecosystem services.People did not expand the trial or medicinal plant cultivation in farms induced by it.They abandoned cropping in 39%farm area and leased 24%abandoned area to a company.Flowering plant species richness and carbon stocks changed at the ecosystem scale but not at the village landscape scale.Emission from agricultural abandonment nullified carbon sequestration by forest restoration.Community forest restoration should render both material/monetary and nonmaterial/non-monetary benefits to people.Cultural landscapes should be taken as spatial units for ecosystem restoration planning,monitoring and evaluation. 展开更多
关键词 BAMBOO BIODIVERSITY Carbon sequestration Climate change Medicinal herbs Threatened species
原文传递
Quantifying unseen woody biomass and diversity in understorey trees and shrubs at the extremes of water availability in the Miombo ecoregion
15
作者 Hermane Diesse John L.Godlee +7 位作者 Nichola Knox Jonathan Muledi Leena Naftal David Nkulu Ben Nkomba Gabriel Uusiku Kyle Dexter Vera De Cauwer 《Forest Ecosystems》 2025年第3期482-494,共13页
The Miombo ecoregion covers eastern and southern Africa,with variations in plant species composition,structure,and biomass across a broad precipitation gradient.Most studies of woody plant communities focus exclusivel... The Miombo ecoregion covers eastern and southern Africa,with variations in plant species composition,structure,and biomass across a broad precipitation gradient.Most studies of woody plant communities focus exclusively on larger overstorey trees(≥5 or≥10cm stem diameter),overlooking the contribution of small trees and shrubs in the understorey,which can comprise a significant portion of total biomass and diversity.Here,we evaluate the contribution of both large overstorey and small understorey woody plants to species diversity and above-ground biomass(AGB),with 17 plots(0.5-1ha)across five sites representing both extremes of rainfall gradient spanning the Miombo ecoregion,in northeast Namibia(500-700mm mean annual precipitation,MAP)and southern Democratic Republic of Congo(DRC)(>1,200mm MAP).Mean AGB per site ranged from 21 to 119Mg·ha^(-1),increasing with rainfall,while the proportional AGB contribution of small trees,saplings,and shrubs decreased.In dry Namibia,small trees,saplings,and shrubs(<5cm DBH)contributed up to 28.2%of total AGB(mean±standard deviation:18.3%±3.4%),whereas in wet DRC,they contributed only up to 2.5%(2.3%±1.4%).Namibian sites,on average,contained a large proportion of woody species diversity exclusively in small trees and shrubs(<5cm DBH),with 55 species representing 59.4%of the total diversity.In contrast,DRC sites had higher overall small woody plant diversity(66 species)but fewer species found exclusively as small individuals(25.2%),with many saplings that grow to larger trees.Understorey composition also differed,with saplings of overstorey trees dominating in DRC,while shrubs dominated in Namibia.Our findings show that woody biomass and diversity in dry woodlands are substantially underestimated when studies focus only on larger trees.This highlights the need to consider all woody vegetation to better understand woody plant diversity and biomass variation. 展开更多
关键词 Miombo woodlands Plant diversity Overstorey UNDERSTOREY Biomass SHRUBS Stand structure
在线阅读 下载PDF
Cardiovascular Sound Classification Using Neural Architectures and Deep Learning for Advancing Cardiac Wellness
16
作者 Deepak Mahto Sudhakar Kumar +6 位作者 Sunil KSingh Amit Chhabra Irfan Ahmad Khan Varsha Arya Wadee Alhalabi Brij B.Gupta Bassma Saleh Alsulami 《Computer Modeling in Engineering & Sciences》 2025年第6期3743-3767,共25页
Cardiovascular diseases(CVDs)remain one of the foremost causes of death globally;hence,the need for several must-have,advanced automated diagnostic solutions towards early detection and intervention.Traditional auscul... Cardiovascular diseases(CVDs)remain one of the foremost causes of death globally;hence,the need for several must-have,advanced automated diagnostic solutions towards early detection and intervention.Traditional auscultation of cardiovascular sounds is heavily reliant on clinical expertise and subject to high variability.To counter this limitation,this study proposes an AI-driven classification system for cardiovascular sounds whereby deep learning techniques are engaged to automate the detection of an abnormal heartbeat.We employ FastAI vision-learner-based convolutional neural networks(CNNs)that include ResNet,DenseNet,VGG,ConvNeXt,SqueezeNet,and AlexNet to classify heart sound recordings.Instead of raw waveform analysis,the proposed approach transforms preprocessed cardiovascular audio signals into spectrograms,which are suited for capturing temporal and frequency-wise patterns.The models are trained on the PASCAL Cardiovascular Challenge dataset while taking into consideration the recording variations,noise levels,and acoustic distortions.To demonstrate generalization,external validation using Google’s Audio set Heartbeat Sound dataset was performed using a dataset rich in cardiovascular sounds.Comparative analysis revealed that DenseNet-201,ConvNext Large,and ResNet-152 could deliver superior performance to the other architectures,achieving an accuracy of 81.50%,a precision of 85.50%,and an F1-score of 84.50%.In the process,we performed statistical significance testing,such as the Wilcoxon signed-rank test,to validate performance improvements over traditional classification methods.Beyond the technical contributions,the research underscores clinical integration,outlining a pathway in which the proposed system can augment conventional electronic stethoscopes and telemedicine platforms in the AI-assisted diagnostic workflows.We also discuss in detail issues of computational efficiency,model interpretability,and ethical considerations,particularly concerning algorithmic bias stemming from imbalanced datasets and the need for real-time processing in clinical settings.The study describes a scalable,automated system combining deep learning,feature extraction using spectrograms,and external validation that can assist healthcare providers in the early and accurate detection of cardiovascular disease.AI-driven solutions can be viable in improving access,reducing delays in diagnosis,and ultimately even the continued global burden of heart disease. 展开更多
关键词 Healthy society cardiovascular system SPECTROGRAM FastAI audio signals computer vision neural network
在线阅读 下载PDF
基于混合积累的SAR微弱运动目标检测 被引量:11
17
作者 李刚 许稼 +2 位作者 彭应宁 夏香根 严军 《电子学报》 EI CAS CSCD 北大核心 2007年第3期576-579,共4页
本文指出在合成孔径雷达(SAR)有限的检测时间内,运动目标的徙动轨迹可近似为一条直线.进而提出了一种基于相干-非相干混合积累的微弱运动目标检测新方法:把检测时间分成多个连续的相干处理间隔(CPI),在各CPI内部通过FFT实现同一距离单... 本文指出在合成孔径雷达(SAR)有限的检测时间内,运动目标的徙动轨迹可近似为一条直线.进而提出了一种基于相干-非相干混合积累的微弱运动目标检测新方法:把检测时间分成多个连续的相干处理间隔(CPI),在各CPI内部通过FFT实现同一距离单元内信号的相干积累,在各CPI间通过Hough变换实现跨越距离单元的非相干积累,从而获得大的积累增益.仿真实验证明,新方法可显著改善微弱运动目标的检测性能. 展开更多
关键词 合成孔径雷达 运动目标检测 相干积累 非相干积累
在线阅读 下载PDF
电离层CT数据采集和图像重建 被引量:4
18
作者 吴雄斌 徐继生 +2 位作者 马淑英 田茂 叶公节 《遥感学报》 EI CSCD 北大核心 2001年第1期22-28,共7页
介绍低纬电离层CT实验所使用的数据自动采集系统并提出一种电离层CT算法。在数据采集过程中引入了GPS标准时间 ;重建算法的特点是利用差分多普勒频率数据避免了相位积分常数的计算 ,提高了对较弱的电离层扰动和不规则结构的检测能力。... 介绍低纬电离层CT实验所使用的数据自动采集系统并提出一种电离层CT算法。在数据采集过程中引入了GPS标准时间 ;重建算法的特点是利用差分多普勒频率数据避免了相位积分常数的计算 ,提高了对较弱的电离层扰动和不规则结构的检测能力。数值模拟反演结果表明了该算法对电离层CT重建的有效性 。 展开更多
关键词 电离层 CT 数据采集 差分多普勒 层析成像 相位数据 扰动 图像重建
在线阅读 下载PDF
土壤保持耕作——全球农业可持续发展优先领域 被引量:35
19
作者 王小彬 蔡典雄 +3 位作者 华珞 Hoogmoed W B Oenema O Perdok U D 《中国农业科学》 CAS CSCD 北大核心 2006年第4期741-749,共9页
从农业活动对全球变化以及对农业可持续发展的影响进而导致全球性土壤保持需求的迫切性增加出发,追踪了国外土壤保持耕作领域的研究和发展动态;对中国该领域研究发展现状和研究水平,从时间、深度、方法、生产应用等方面与国外进行了比... 从农业活动对全球变化以及对农业可持续发展的影响进而导致全球性土壤保持需求的迫切性增加出发,追踪了国外土壤保持耕作领域的研究和发展动态;对中国该领域研究发展现状和研究水平,从时间、深度、方法、生产应用等方面与国外进行了比较分析。中国是一个水土流失和耕地退化严重的农业大国,而从全球统计数字来看,中国土壤保持耕作面积目前仅占全球保持耕作面积的0.2%,仅占全国耕地面积的0.1%,其现状与中国耕地资源和环境的继续退化以及对土壤保持耕作需求的增加极不相符。加强中国土壤保持耕作系统研究和土壤保持耕作“节能固碳”长期建设不仅对中国而且对全球变化及农业可持续发展具有重大意义。鉴于中国土壤保持耕作领域研究和发展所存在的不足和所面临的更大挑战,以及该领域研究涉及到复杂的农业系统“耕作管理-生物过程-环境变化”相互作用及其系统能流-碳流循环过程,尤其农业生态系统碳汇/源估量尚存在诸多不确定性因素等科学问题,有必要运用综合的系统性研究分析方法,借助国外长期试验和理论研究经验,以及系统模型模拟研究手段等多学科和交叉学科知识,加速提升中国土壤保持耕作领域的科研实力和水平,为实现碳汇/源科学调控管理、减缓农业对温室效应贡献、促进农业可持续发展提供科学依据。 展开更多
关键词 土壤保持耕作 全球变化 农业可持续发展 能量平衡 碳循环 专论
在线阅读 下载PDF
基于Multi-Agent异步深度强化学习的居民住宅能耗在线优化调度研究 被引量:30
20
作者 张虹 申鑫 +2 位作者 穆昊源 刘艾冬 王鹤 《中国电机工程学报》 EI CSCD 北大核心 2020年第1期117-127,共11页
为促进居民用户柔性负荷高效参与需求响应,帮助用户从被动角色转变为主动角色,实现需求侧最大效益。该文在智能电网环境下,根据用电设备的特性,以概率论的角度对家电设备状态进行描述定义,基于异步深度强化学习(asynchronous deep reinf... 为促进居民用户柔性负荷高效参与需求响应,帮助用户从被动角色转变为主动角色,实现需求侧最大效益。该文在智能电网环境下,根据用电设备的特性,以概率论的角度对家电设备状态进行描述定义,基于异步深度强化学习(asynchronous deep reinforcement learning,ADRL)进行家庭能源管理系统调度的在线优化。学习过程采用异步优势演员–评判家(asynchronous advantage actor-critic,A3C)方法,联合用户历史用电设备运行状态的概率分布,通过多智能体利用CPU多线程功能同时执行多个动作的决策。该方法在包括光伏发电、电动汽车和居民住宅电器设备信息的某高维数据库上进行仿真验证。最后通过不同住宅情境下的优化决策效果对比分析可知,所提在线能耗调度策略可用于向电力用户提供实时反馈,以实现用户用电经济性目标。 展开更多
关键词 异步优势演员-评判家 需求响应 概率分布 在线优化 多智能体 多动作决策
原文传递
上一页 1 2 30 下一页 到第
使用帮助 返回顶部