期刊文献+
共找到852篇文章
< 1 2 43 >
每页显示 20 50 100
卫星边缘网络中基于扩散模型的算力分配策略
1
作者 王兴杰 王侃 +4 位作者 费蓉 王怀军 郭银波 兰大鹏 朱晓杰 《计算机工程》 北大核心 2026年第1期346-355,共10页
通过协同管理地面网络、卫星网络和近地无人机网络等,空天地一体化算力融合网络有望实现全域连接和普适智能,为我国数字经济发展提供有力支撑。而低轨道地球(LEO)卫星具备泛在连接和边缘计算能力,为实现空天地一体化的高效计算体系提供... 通过协同管理地面网络、卫星网络和近地无人机网络等,空天地一体化算力融合网络有望实现全域连接和普适智能,为我国数字经济发展提供有力支撑。而低轨道地球(LEO)卫星具备泛在连接和边缘计算能力,为实现空天地一体化的高效计算体系提供了基础。通过将移动边缘计算(MEC)沉降至LEO卫星网络,形成面向业务的“端-边-云”三级计算架构,可将时延敏感型业务从终端卸载到LEO卫星侧,以提升该业务的任务完成率。然而,为LEO卫星边缘网络制定高效计算卸载和算力分配决策是一个亟待解决的问题。针对高动态性的卫星网络环境和离散-连续的混合动作空间,提出一种基于生成扩散模型的混合近端策略优化(H-PPO)方法。首先,对具有时变特性的无线信道进行建模,并构建不同卸载决策下的服务时延、通信和计算模型。其次,在卸载决策、剩余计算资源和功率控制的多约束条件下,构建最大化平均任务完成率的长期优化问题。然后,建立具有参数化动作的马尔可夫决策过程模型,将生成扩散模型引入为离散动作策略,增强传统深度强化学习(DRL)方法的采样效率和探索能力,并利用所提算法联合优化计算卸载、算力分配和功率控制变量。仿真结果表明,所提算法具有较好收敛性能,并在任务完成率方面优于其他3种对比方法。 展开更多
关键词 空天地一体化网络 低轨道地球卫星 移动边缘计算 深度强化学习 生成扩散模型 计算卸载 资源分配
在线阅读 下载PDF
The 33rd International Geological Congress, Oslo 2008
2
作者 Anders Solheim Arne BjФrlykke 《Episodes》 SCIE 2008年第1期9-12,共4页
The 33rd International Geological Congress is being organised jointly by the Nordic countries and to be held in Oslo, Norway, August 6-14th, 2008. This "Geoscience World Congress 2008" will run up to 40 parallel sci... The 33rd International Geological Congress is being organised jointly by the Nordic countries and to be held in Oslo, Norway, August 6-14th, 2008. This "Geoscience World Congress 2008" will run up to 40 parallel science sessions, poster sessions, an extensive exhibition, short-courses, workshops, and business meet- ings; about 50 exciting preand post-Congress excursions are planned. The excursions include all the Nordic countries, as well as Greenland, Svalbard, the Faeroes, Russia and Ukraine. All major geoscientific themes are being covered by the Congress which has been divided into two parts, Sunday lOth August being without Symposia and dedicated to workshops, short courses, business meetings and excursions. Through a series of "Themes of the Day", seven themes with major societal impact will be covered in plenary sessions with invited lecturers, including a key-note "StatoiIHydro lecture" given each day during the lunch interval. The venue is set up to offer a compact Congress with easy access to all sessions and other events. An extensive social and cultural programme is also being arranged. 展开更多
关键词 第33届国际地质大会 地球科学 挪威 奥斯陆 2008年
在线阅读 下载PDF
面向MBSE的起落架系统模型集成技术 被引量:1
3
作者 张浩轩 梁赞 +5 位作者 王国新 吴绶玄 鲁金直 阎艳 袁永吉 乔佳兴 《图学学报》 北大核心 2025年第3期686-696,共11页
为了解决起落架系统在设计过程中架构建模和仿真建模工具之间的互操作问题,提供对架构建模和仿真建模工具之间跨域信息的双向传递和接口互操作的能力,提出了面向基于模型系统工程(MBSE)的起落架系统模型集成技术。首先,采用多架构建模语... 为了解决起落架系统在设计过程中架构建模和仿真建模工具之间的互操作问题,提供对架构建模和仿真建模工具之间跨域信息的双向传递和接口互操作的能力,提出了面向基于模型系统工程(MBSE)的起落架系统模型集成技术。首先,采用多架构建模语言(KARMA)构建起落架系统架构模型,进而通过架构模型中的仿真方案生成仿真模型。其次构建模型语义映射规则并通过解析仿真模型内容建立仿真模型的集成数据模型,使得异构模型的语义具有一致性,进而构建仿真工具适配器,实现对异构数据的统一编译,以及架构模型和仿真模型的集成。结果表明,该方法实现了设计信息在异构模型间的双向传递以及架构建模和仿真建模工具间的互操作,为起落架系统的架构模型和仿真模型间集成提供了支持。 展开更多
关键词 基于模型的系统工程 模型集成 起落架系统 KARMA SIMULINK
在线阅读 下载PDF
考虑多光学遥感指标的河流流量反演方法
4
作者 何立滢 陈华 +3 位作者 黄煜 盛晟 周聂 许崇育 《地理学报》 北大核心 2025年第11期3041-3057,共17页
径流是水循环过程的重要要素。采用传统水文测验观测流量受站点布设影响大,基于物理过程的径流模拟依赖高质量、长序列的多要素观测资料。利用遥感资料反演流量受自然、社会等因素干预小,为径流模拟提供新的技术手段。目前,遥感指示物... 径流是水循环过程的重要要素。采用传统水文测验观测流量受站点布设影响大,基于物理过程的径流模拟依赖高质量、长序列的多要素观测资料。利用遥感资料反演流量受自然、社会等因素干预小,为径流模拟提供新的技术手段。目前,遥感指示物与流量间的关系有待进一步挖掘。本文基于2017—2023年Sentinel-2号影像的多波段信息构建7个光学遥感指示指标,以建溪流域七里街水文站附近的河道为研究对象,通过对180组像元分别应用传统对照/测量法(C/M法)、多元线性回归方法和随机森林反演流量,并进行精度评价。结果表明:传统C/M法的反演效果显著受M像元选取的影响,需选择对不同量级流量均敏感的像元作为M像元;综合应用CM信号、水体指数(NDWI)、植被指数(NDVI)、裸土指数(BSI)和水体浑浊指数(TWI)能够更全面地捕捉河道水面、植被和水质等特征,相比传统C/M法,考虑多种遥感指数的多元线性回归方法和随机森林算法降低了反演结果对M像元选择的敏感性;在3种方法中,随机森林算法反演流量精度最高,且在高流量处反演效果提升明显。研究成果可为河道径流模拟提供科学参考,为河道智能化监测提供指导建议。 展开更多
关键词 径流反演 水文遥感 C/M方法 遥感指数 随机森林
原文传递
基于模型的系统工程中的架构模型质量综述:概念、框架和技术
5
作者 龚逸辉 王国新 +3 位作者 阎艳 吴绶玄 董梦如 袁永吉 《系统工程与电子技术》 北大核心 2025年第12期3890-3900,共11页
基于模型的系统工程(model-based systems engineering,MBSE)的发展为复杂装备提供一种全新的设计范式。从“以文本为中心”向“以模型为中心”的转变,推动产品交付的数字化进程。因此,模型质量成为MBSE系统模型的开发过程中需要重点衡... 基于模型的系统工程(model-based systems engineering,MBSE)的发展为复杂装备提供一种全新的设计范式。从“以文本为中心”向“以模型为中心”的转变,推动产品交付的数字化进程。因此,模型质量成为MBSE系统模型的开发过程中需要重点衡量的问题。首先,讨论架构模型质量的基本内涵和概念定义;重点分析架构模型质量所涉及的质量特征,提出架构模型质量框架来量化定义什么是“好的模型”。然后,探讨面向复杂装备设计的模型质量保证技术。最后,讨论架构模型质量在设计过程中面临的挑战,展望未来的发展方向,促进无缺陷模型贯穿产品全生命周期,驱动装备数字化设计的高质量发展。 展开更多
关键词 基于模型的系统工程 架构模型 模型质量
在线阅读 下载PDF
基于特定域建模的起落架系统多架构设计方法
6
作者 吴绶玄 王国新 +7 位作者 梁赞 张涛 祁振强 鲁金直 阎艳 龚逸辉 张浩轩 张臻 《机械工程学报》 北大核心 2025年第19期273-289,共17页
针对起落架系统总体设计过程中存在的架构模型多层次粒度不清、多阶段交互复杂、多领域耦合异构问题,提出基于特定域建模的起落架系统多架构设计方法。首先从系统-子系统-单机等多层级、需求-功能-逻辑-物理等多阶段、机-电-液-控等多领... 针对起落架系统总体设计过程中存在的架构模型多层次粒度不清、多阶段交互复杂、多领域耦合异构问题,提出基于特定域建模的起落架系统多架构设计方法。首先从系统-子系统-单机等多层级、需求-功能-逻辑-物理等多阶段、机-电-液-控等多领域3个维度分析起落架系统的架构设计过程,提出起落架系统多架构设计框架。结合特定域建模技术对起落架系统设计要素进行共性抽象,构建需求、功能、行为等认知域元模型以及物理产品方案等物理域元模型,并采用模型驱动技术实现起落架系统静态技术参数和动态系统行为的计算与仿真验证。最后以某型号飞行器起落架系统总体设计为例,通过该方法对起落架设计过程中的需求、功能、逻辑和物理等架构进行建模与仿真分析,验证了该方法能够提高起落架系统架构设计的可拓展性。 展开更多
关键词 基于模型的系统工程 特定域建模 系统架构设计 起落架系统 元模型
原文传递
面向空间智能的基于模型的系统工程方法
7
作者 鲁金直 王国新 +10 位作者 唐锡晋 唐俊杰 温跃杰 唐剑 张旸旸 兰小平 刘奇 李俊霖 马君达 吴绶玄 胡晓度 《系统工程与电子技术》 北大核心 2025年第12期3877-3889,共13页
现有系统工程研制方法在智能化手段方面存在明显不足,难以满足复杂装备研制过程中日益增长的智能设计需求。针对这一问题,提出一种面向空间智能的基于模型的系统工程方法。该方法充分发挥了多架构统一建模语言架构模型规范的组合(kombin... 现有系统工程研制方法在智能化手段方面存在明显不足,难以满足复杂装备研制过程中日益增长的智能设计需求。针对这一问题,提出一种面向空间智能的基于模型的系统工程方法。该方法充分发挥了多架构统一建模语言架构模型规范的组合(kombination of architecture model specification,KARMA)的语义建模优势,融合了大语言模型、计算机视觉、三维场景建模等前沿技术,构建了系统工程领域的空间智能框架,从而实现了面向复杂装备数字化研制及系统工程研发的智能化建模方法。通过3个典型场景的智能化建模案例,系统验证了基于KARMA语言的空间智能框架的可行性和实用性。进一步研究表明,通过将KARMA与大语言模型、计算机视觉及三维模型进行深度整合,所提方法在支持复杂系统智能化设计方面展现出显著优势,为系统工程领域的智能化转型提供了技术路径。 展开更多
关键词 空间智能 基于模型的系统工程 大语言模型 架构模型规范的组合语言 智能设计
在线阅读 下载PDF
Mg/Al合金复合材料成形与制备:优势、挑战与突破方向
8
作者 谢旭峰 周弋凇 +4 位作者 赵健行 王延 钟韬 胡红军 马相 《精密成形工程》 北大核心 2025年第10期1-20,共20页
轻量化技术对推动运输行业节能减排有着重要作用,双金属复合材料在该领域潜力巨大。其中Mg/Al复合材料因镁合金和铝合金的独特优势而备受关注,但存在硬脆相金属间化合物影响结合强度的问题,提升其结合强度成为研究热点。本文综述了国内... 轻量化技术对推动运输行业节能减排有着重要作用,双金属复合材料在该领域潜力巨大。其中Mg/Al复合材料因镁合金和铝合金的独特优势而备受关注,但存在硬脆相金属间化合物影响结合强度的问题,提升其结合强度成为研究热点。本文综述了国内外Mg/Al复合材料制备方法包括焊接、铸造、轧制和挤压等的研究进展,指出不同工艺下扩散层结构和金属间化合物的形成效果有所不同。为提高结合强度,研究主要集中在添加合金元素和工艺优化两方面。在各连接工艺中添加合金元素如Zn、Ni、Ag等能有效改善基体力学性能,但也可能引入新的问题,如硬度降低、引发应力集中和断裂韧性降低等。在工艺优化方面,超声波振动辅助工艺在焊接和铸造中展现出显著优势,能细化晶粒、抑制金属间化合物生长、优化界面结构,提高材料的剪切强度、硬度和韧性,但对挤压工艺的研究较少。此外,本文总结了超声波振动对Mg和Al合金本身的微观组织和力学性能的积极影响,指出了超声波振动辅助技术当前面临的挑战,并对其优化方向和发展前景进行了展望。 展开更多
关键词 Mg/Al复合材料 轻量化技术 超声波振动辅助 挤压剪切工艺 结合强度
在线阅读 下载PDF
井眼成像测井在巴西古火山环境表征中的应用及其对油气勘探的意义
9
作者 FORNERO S A MILLETT J M +4 位作者 DE JESUS C M DE LIMA E F MARINS G M PEREIRA N F BEVILAQUA L A 《石油勘探与开发》 北大核心 2025年第3期618-637,共20页
传统的成像测井解释方法对圆柱展开投影中呈正弦形态的火山岩线性裂缝识别较为成熟有效,然而对非线性火山岩岩石构造及复杂岩相几何形态的解释则比较困难。为表征与南美大陆形成相关的古火山复杂环境,本研究基于成像测井、岩相学和地震... 传统的成像测井解释方法对圆柱展开投影中呈正弦形态的火山岩线性裂缝识别较为成熟有效,然而对非线性火山岩岩石构造及复杂岩相几何形态的解释则比较困难。为表征与南美大陆形成相关的古火山复杂环境,本研究基于成像测井、岩相学和地震资料分析,提出了一种新的表征方法。该方法使用全球范围典型火成岩的地质露头照片来创建伪图像,模拟直径约31 cm(12.25 in)井眼的井壁二维平面图像;在此基础上,根据这些伪图像和标准露头照片来确定火成岩结构和岩相的形态模式,并与地下火山和次火山岩地质单元的电缆井眼成像测井图像进行对比,进而为火山岩相的地质评价提供了“可视化标尺”,提升了复杂地质结构的识别效率与可信度。应用该新方法,重点分析了巴西坎波斯、桑托斯和帕纳伊巴等盆地不同尺度的柱状节理和枕状熔岩,并辅以绳状熔岩、熔结凝灰岩、火山碎屑岩和各种侵入特征等实例分析,结果显示,该方法提高了次火山、陆上和水下沉积体解释的准确度。通过成像测井解释结果与区域地质认识相结合,并把古环境研究纳入冈瓦纳大陆裂解相关的裂谷岩浆作用体系研究,对油气勘探开发具有重要意义。 展开更多
关键词 井眼成像测井 伪图像 火成岩 油气勘探 岩相 测井解释 火山古环境 桑托斯盆地 坎波斯盆地 巴西盆地
在线阅读 下载PDF
Exercise-induced extracellular vesicles delay tumor development by igniting inflammation in an immunologically cold triple-negative breast cancer mouse model
10
作者 Agata Mlynska Neringa Dobrovolskiene +11 位作者 Karolina Suveizde Gabija Lukaseviciute Krizia Sagini Beatriz Martin-Gracia Silvana Romero Alicia Llorente Aija Line Austeja Butkute Beatrice Gudaite Tomas Venckunas Nijole Matuseviciene Vita Pasukoniene 《Journal of Sport and Health Science》 2025年第6期17-32,166,共17页
Background Preclinical studies demonstrate that exercise reduces tumor incidence and growth.Rapid release of extracellular vesicles(EVs)during exercise suggests their potential role as mediators of exercise-induced sy... Background Preclinical studies demonstrate that exercise reduces tumor incidence and growth.Rapid release of extracellular vesicles(EVs)during exercise suggests their potential role as mediators of exercise-induced systemic effects and physiological adaptation.This study investigated the impact of exercise-induced plasma EVs on tumor growth and immune tumor microenvironment in murine models of triple-negative breast cancer(TNBC):EO771(a C57BL/6-derived TNBC cell line)and 4T1(a BALB/c-derived TNBC cell line).Methods Size exclusion chromatography was used to isolate exercise-induced EVs from plasma of healthy female mice(BALB/c and C56BL/6,n=30 per strain)that underwent ten 30-min moderate-intensity treadmill running sessions over 2 weeks.Nanoparticle tracking analysis,Western blot,and electron microscopy confirmed the presence of EVs in the samples.Tumor-bearing mice(n=72 per strain)were administered with exercise-induced EVs before or/and after tumor implantation.Local and systemic immune responses were assessed using flow cytometry,enzyme-linked immunosorbent assay(ELISA),and quantitative polymerase chain reaction(qPCR).Results Administration of exercise-induced EVs,particularly before tumor implantation,significantly suppressed tumor growth and reduced tumor burden in both TNBC models.In EO771,endpoint tumor volumes were 278–330 mm^(3)in treated groups compared to 799 mm^(3)in untreated(p<0.0001),while in 4T1,treated groups showed volumes of 287–564 mm^(3)vs.696 mm^(3)in untreated(p=0.0002).Notable differences in tumor-infiltrating lymphoid and myeloid cell subpopulations indicated immunomodulatory effects of exercise-induced EVs,particularly in the 4T1 model,where their continuous administration significantly increased intratumoral cluster of differentiation 8(CD8)T lymphocyte proportion(5.77%vs.0.90%in untreated,p<0.0001).Similarly,in the EO771 model,exercise-induced EVs administered before tumor implantation led to a marked rise in intratumoral CD8 T lymphocytes(2.24%vs.1.08%in untreated,p=0.0181).Conclusion Our findings indicate that exercise-induced EV treatment elicits a pro-inflammatory antitumor immune response,suggesting a shift of immunologically cold TNBC tumors towards a more inflamed phenotype associated with better outcomes.Our study supports the further investigation of EVs as modulators of antitumor immunity and their potential utility in enhancing the efficacy of immunotherapy. 展开更多
关键词 EXERCISE Extracellular vesicles Triple-negative breast cancer Tumor microenvironment Immune modulation
暂未订购
Application of borehole images in the characterization of volcanic paleoenvironments with implications for the exploration of hydrocarbons in Brazilian basins
11
作者 FORNERO S A MILLETT J M +4 位作者 DE JESUS C M DE LIMA E F MARINS G M PEREIRA N F BEVILAQUA L A 《Petroleum Exploration and Development》 2025年第3期692-714,共23页
Conventional borehole image log interpretation of linear fractures on volcanic rocks,represented as sinusoids on unwrapped cylinder projections,is relatively straight-forward,however,interpreting non-linear rock struc... Conventional borehole image log interpretation of linear fractures on volcanic rocks,represented as sinusoids on unwrapped cylinder projections,is relatively straight-forward,however,interpreting non-linear rock structures and complex facies geometries can be more challenging.To characterize diverse volcanic paleoenvironments related to the formation of the South American continent,this study presents a new methodology based on image logs,petrography,seismic data,and outcrop analogues.The presented methodology used pseudo-boreholes images generated from outcrop photographs with typical igneous rock features worldwide simulating 2D unwrapped cylinder projections of a 31 cm(12.25 in)diameter well.These synthetic images and standard outcrop photographs were used to define morphological patterns of igneous structures and facies for comparison with wireline borehole image logs from subsurface volcanic and subvolcanic units,providing a“visual scale”for geological evaluation of volcanic facies,significantly enhancing the identification efficiency and reliability of complex geological structures.Our analysis focused on various scales of columnar jointing and pillow lava lobes with additional examples including pahoehoe lava,ignimbrite,hyaloclastite,and various intrusive features in Campos,Santos,and Parnaíba basins in Brazil.This approach increases confidence in the interpretation of subvolcanic,subaerial,and subaqueous deposits.The image log interpretation combined with regional geological knowledge has enabled paleoenvironmental insights into the rift magmatism system related to the breakup of Gondwana with associated implications for hydrocarbon exploration. 展开更多
关键词 borehole image log pseudo-image igneous rock hydrocarbon exploration lithofacies log interpretation volcanic paleoenvironment Santos Basin Campos Basin Parnaíba Basin
在线阅读 下载PDF
Exploring the Interpretability of Forecasting Models for Energy Balancing Market
12
作者 Oskar VÅLE Shiliang ZHANG +1 位作者 Sabita MAHARJAN Gro KlÆBOE 《Artificial Intelligence Science and Engineering》 2025年第4期295-306,共12页
The balancing market in the energy sector plays a critical role in physically and financially balancing the supply and demand.Modeling dynamics in the balancing market can provide valuable insights and prognosis for p... The balancing market in the energy sector plays a critical role in physically and financially balancing the supply and demand.Modeling dynamics in the balancing market can provide valuable insights and prognosis for power grid stability and secure energy supply.While complex machine learning models can achieve high accuracy,their“blackbox”nature severely limits the model interpretability.In this paper,we explore the trade-off between model accuracy and interpretability for the energy balancing market.Particularly,we take the example of forecasting manual frequency restoration reserve(mFRR)activation price in the balancing market using real market data from different energy price zones.We explore the interpretability of mFRR forecasting using two models:extreme gradient boosting(XGBoost)machine and explainable boosting machine(EBM).We also integrate the two models,and we benchmark all the models against a baseline naive model.Our results show that EBM provides forecasting accuracy comparable to XGBoost while yielding a considerable level of interpretability.Our analysis also underscores the challenge of accurately predicting the mFRR price for the instances when the activation price deviates significantly from the spot price.Importantly,EBM's interpretability features reveal insights into non-linear mFRR price drivers and regional market dynamics.Our study demonstrates that EBM is a viable and valuable interpretable alternative to complex black-box AI models in the forecast for the balancing market. 展开更多
关键词 explainable AI model interpretability energy balancing market mFRR activation price forecasting
在线阅读 下载PDF
Fault Detection in Wind Turbine Bearings by Coupling Knowledge Graph and Machine Learning Approach
13
作者 Paras Garg Arvind Keprate +2 位作者 Gunjan Soni A.P.S.Rathore O.P.Yadav 《Journal of Dynamics, Monitoring and Diagnostics》 2025年第4期250-263,共14页
Fault sensing in wind turbine(WT)generator bearings is essential for ensuring reliability and holding down maintenance costs.Feeding raw sensor data to machine learning(ML)model often overlooks the enveloping interdep... Fault sensing in wind turbine(WT)generator bearings is essential for ensuring reliability and holding down maintenance costs.Feeding raw sensor data to machine learning(ML)model often overlooks the enveloping interdependencies between system elements.This study proposes a new hybrid method that combines the domain knowledge via knowledge graphs(KGs)and the traditional feature-based data.Incorporation of contextual relationships through construction of graph embedding methods,such as Node2Vec,can capture meaningful information,such as the relationships among key parameters(e.g.wind speed,rotor Revolutions Per Minute(RPM),and temperature)in the enriched feature representations.These node embeddings,when augmented with the original data,can be used to allow the model to learn and generalize better.As shown in results achieved on experimental data,the augmented ML model(with KG)is much better at predicting with the help of accuracy and error measure compared to traditional ML methods.Paired t-test analysis proves the statistical validity of this improvement.Moreover,graph-based feature importance increases the interpretability of the model and helps to uncover the structurally significant variables that are otherwise ignored by the common methods.The approach provides an excellent,knowledge-guided manner through which intelligent fault detection can be executed on WT systems. 展开更多
关键词 anomaly detection knowledge graph embedding machine learning wind turbine fault detection
在线阅读 下载PDF
Numerical investigation of wellbore damage due to drill string lateral vibration
14
作者 Hadi Haghgouei Anders Nermoen Alexandre Lavrov 《Journal of Rock Mechanics and Geotechnical Engineering》 2025年第3期1287-1301,共15页
During drilling operations,cyclic loading is exerted on the wellbore wall by the vibrations of the drill string.This loading could lead to rock fatigue,which in turn might result in wellbore failure.In this study,a nu... During drilling operations,cyclic loading is exerted on the wellbore wall by the vibrations of the drill string.This loading could lead to rock fatigue,which in turn might result in wellbore failure.In this study,a numerical model is developed to simulate the effects of repeated loading on rock fatigue and failure.The simulation is based on an elasto-plastic constitutive model coupled with a damage mechanics approach,which allows us to examine the wellbore instability due to drill string vibrations.The model is verified with the existing data in the literature related to experiments on impact of a steel ball against a curved wall.The findings indicate that cyclic loading increases the development of plastic strain around the wellbore significantly compared to static conditions,promoting rock fatigue.Furthermore,the cyclic loading expands the radius of the yielded zone substantially,a critical factor for maintaining wellbore integrity.The proposed model can be used to evaluate the wellbore stability under repetitive loading caused by the drill string action. 展开更多
关键词 Wellbore stability Damage mechanics Fatigue modeling Drill string vibration
在线阅读 下载PDF
Riverine fluxes of dissolved inorganic nitrogen may be underestimated in gated estuaries:influence of suspended sediments
15
作者 Chenglong HAN Lichun PU +2 位作者 Shiyu WANG Rolf D.VOGT Xueqiang LU 《Journal of Oceanology and Limnology》 2025年第6期1809-1825,共17页
The flux of dissolved inorganic nitrogen(DIN),predominantly nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+)),from land to coastal waters via rivers is commonly estimated simply by multiplying water flux with nitrogen conce... The flux of dissolved inorganic nitrogen(DIN),predominantly nitrate(NO_(3)^(-))and ammonium(NH_(4)^(+)),from land to coastal waters via rivers is commonly estimated simply by multiplying water flux with nitrogen concentration.Understanding DIN fluxes in gated estuaries is critical as these systems often serve as hotspots for nutrient transformations,influencing coastal water quality and ecosystem health.However,the subsequent interactions involving NO_(3)^(-)and NH_(4)^(+)adsorption or desorption on suspended sediments are often overlooked.To better understand the impact of these interactions on the overall NO_(3)^(-)and NH_(4)^(+)sorption or desorption and subsequently,the mobility and transport to the coastal zone,we conducted a series of NO_(3)^(-)and NH_(4)^(+)adsorption and desorption experiments.These experiments involved varying suspended sediment concentrations,particle sizes,salinities,and sea-salt ions to assess their potential effects.Results indicate that desorption of NO_(3)^(-)and NH_(4)^(+)from suspended sediments is more prominent than adsorption,with NH_(4)^(+)desorption being particularly significant.Notably,at low suspended particle concentrations and high salinity,NH_(4)^(+)desorption from sediments increased markedly,which further amplified in polyhaline conditions.This effect could result from ion pairing between NH_(4)^(+)and seawater anions,along with competition from seawater cations for sediment cation exchange sites,enhancing NH_(4)^(+)diffusion from estuarine sediments,and the elevated NH_(4)^(+)release could promote DIN transport to nearshore waters,especially in gated estuaries where sediment resuspension occurs.Given the critical role of NH_(4)^(+)in estuarine nitrogen cycling,ignoring these dynamics could lead to underestimations of DIN transport in river-estuary systems.Therefore,incorporating sediment dynamics into DIN flux estimations is crucial for accurately assessing nitrogen transport in gated estuaries. 展开更多
关键词 seaward nitrogen flux ADSORPTION/DESORPTION suspended sediments SALINITY gated estuary
在线阅读 下载PDF
Multiple surge trigger mechanisms of compound glacier:a case study on recent surges of Aru-4 Glacier,Western Tibetan Plateau
16
作者 GUAN Weijin CAO Bo +4 位作者 SHA Linwei PAN Baotian ZHAO Xuanru JIANG Zongli WU Guangjian 《Journal of Mountain Science》 2025年第11期3931-3943,共13页
Surge-type glaciers are widely developed in mountainous areas around the world.Understanding the trigger mechanism of glacier surge is a prerequisite for addressing their impacts on hydrological assessments,disentangl... Surge-type glaciers are widely developed in mountainous areas around the world.Understanding the trigger mechanism of glacier surge is a prerequisite for addressing their impacts on hydrological assessments,disentangling climate-glacier linkages,and mitigating downstream hazards.Most glacier surges occur in the compound glaciers;however,attention paid to the trigger mechanisms of such surges is minimal.This study confirmed two surges in the northern and southern branches of the Aru-4 glacier,respectively,in the Western Tibetan Plateau,using multisource remote sensing data.The northern branch of the Aru-4 glacier entered the active phase in 1999 and the active phase lasted for 6 years.The southern branch of the Aru-4 glacier entered the active phase in 2007 and the active phase lasted for 9 years.The southern branch of the Aru-4 glacier experienced a long period of retreat before the northern branch surged and their tongues were in a detached state.The northern branch surge carried a large amount of ice to the frontal area,blocking the downward transport of ice from the southern branch and initiated surge.Through the analysis of two surge processes of Aru-4 glacier,we found a new surge mechanism for compound glaciers.It was revealed that surges in such glaciers are not only triggered by the reduction in basal sliding resistance caused by the internal factors.These surges initiated in the upper part of the glacier then propagated to down glacier by intense compression force.Furthermore,surges can also be triggered by external intervention of blocking by other branches.This external trigger initiates the surge in the lower part of the glacier then propagated to the upper part by longitudinal traction force.In addition,comparing with the surge triggered by the internal factors,the surge triggered by the external intervention may have a more dramatic process. 展开更多
关键词 GLACIER Glacier surge Surge trigger mechanisms Aru-4 Glacier
原文传递
Rethinking the role of bisphosphonates after denosumab treatment in locally advanced or unresectable aneurysmal bone cysts:A metaanalysis
17
作者 Gennady N Machak Øyvind S Bruland +1 位作者 Alexey V Kovalev Svetlana S Rodionova 《World Journal of Orthopedics》 2025年第8期116-131,共16页
BACKGROUND Aneurysmal bone cysts(ABCs)are usually treated with curettage or various minimally invasive percutaneous procedures.Patient refractory to these treatments,as well as those with locally advanced or unresecta... BACKGROUND Aneurysmal bone cysts(ABCs)are usually treated with curettage or various minimally invasive percutaneous procedures.Patient refractory to these treatments,as well as those with locally advanced or unresectable tumors,present a challenge for orthopedic surgeons and require new treatment approaches.Antiresorptive drugs inhibit osteoclastic resorption and increase intralesional osteogenesis.Denosumab induces tumor ossification,but this effect may disappear after drug withdrawal due to limited impact on neoplastic cells.Bisphosphonates(BPs)may induce apoptosis of tumor cells and allow for long-term local control.We hypothesized that after denosumab treatment,BPs would better accumulate in the tumor and exert an irreversible antitumor effect.AIM To test the hypothesis that the sequential use of BPs after denosumab induction improves treatment outcomes in surgically unsalvageable ABCs.METHODS Using data from five electronic databases(Scopus,MEDLINE,EMBASE,PubMed,Web of Science),we aimed to identify all patients who received denosumab therapy(DT)for unresectable ABCs.Among published case reports and case series,we identified patients who discontinued denosumab for various reasons and divided them into two groups:Group 1 included 31 patients without further anti-resorptive therapy and Group 2 included 12 patients who received BPs in the context of rebound hypercalcemia.Local control rates in both groups were analyzed.RESULTS As of December 2024,43 patients have been reported in the literature who received DT for locally advanced/unresectable ABCs.There were 27 males and 16 females with a mean age of 15.8 years.At a median follow-up time of 15.5 months,there were 10 confirmed and two pathologically unconfirmed relapses after denosumab discontinuation.All 10 relapses occurred in patients in Group 1 at a median time of 13.5 months.Among patients in Group 2,with a median follow-up time of 12.5 months after completion of therapy,no local relapses were observed.The difference between local recurrence rates(32%vs 0%)is statistically significant(P value=0.02).Kaplan-Meier estimates show the same trend with marginal statistical significance(P value=0.085).Here we put forward a novel treatment algorithm.CONCLUSION BPs used in post-denosumab ossifying ABCs appear to improve treatment outcomes,presumably by targeting residual tumor cells.Prospective clinical studies are warranted to validate this promising two-stage conceptual strategy in difficult-to-treat ABC. 展开更多
关键词 Aneurysmal bone cyst Locally advanced/inoperable DENOSUMAB Rebound hypercalcemia BISPHOSPHONATES
暂未订购
Managing lower extremity loading in distance running by altering sagittal plane trunk leaning
18
作者 Luca Braun Patrick Mai +6 位作者 Markus Hipper Yannick Denis Janina Helwig Bastian Anedda Burkay Utku Dominic Gehring Steffen Willwacher 《Journal of Sport and Health Science》 2025年第2期35-45,共11页
Background:Trunk lean angle is an underrepre sented biomechanical variable for modulating and redistributing lower extremity joint loading and potentially reducing the risk of running-related overuse injuries.The purp... Background:Trunk lean angle is an underrepre sented biomechanical variable for modulating and redistributing lower extremity joint loading and potentially reducing the risk of running-related overuse injuries.The purpose of this study was to systematically alter the trunk lean angle in distance running using an auditory real-time feedback approach and to derive dose-response relationships between sagittal plane trunk lean angle and lower extremity(cumulative)joint loading to guide overuse load management in clinical practice.Methods:Thirty recreational runners(15 males and 15 females)ran at a constant speed of 2.5 m/s at 5 systematically varied trunk lean conditions on a force-instrumented treadmill while kinematic and kinetic data were captured.Results:A change in trunk lean angle from-2°(extension)to 28°(flexion)resulted in a systematic increase in stance phase angular impulse,cumulative impulse,and peak moment at the hip joint in the sagittal and transversal plane.In contrast,a systematic decrease in these parameters at the knee j oint in the sagittal plane and the hip joint in the frontal plane was found(p<0.001).Linear fitting revealed that with every degree of anterior trunk leaning,the cumulative hip joint extension loading increases by 3.26 Nm·s/kg/1000 m,while simultaneously decreasing knee joint extension loading by 1.08 Nm·s/kg/1000 m.Conclusion:Trunk leaning can reduce knee joint loading and hip joint abduction loading,at the cost of hip joint loading in the sagittal and transversal planes during distance running.Modulating lower extremity joint loading by altering trunk lean angle is an effective strategy to redistribute joint load between/within the knee and hip joints.When implementing anterior trunk leaning in clinical practice,the increased demands on the hip musculature,dynamic stability,and the potential trade-off with running economy should be considered. 展开更多
关键词 Cumulative loading Overuse injuries Trunk orientation Locomotion
在线阅读 下载PDF
Environmental Phillips and Kuznets curves in organization for economic cooperation and development states:Fresh insights
19
作者 Muhammad Tahir Umar Burki +3 位作者 Talal HAlsabhan Mohammad Jaboob Usama Najam Maran Marimuthu 《Chinese Journal of Population,Resources and Environment》 2025年第3期301-309,共9页
This research extends the literature on the environmental Phillips curve(EPC)and environmental Kuznets curve(EKC)by focusing on the 38 member economies of the Organization for Economic Co-operation and Development(OEC... This research extends the literature on the environmental Phillips curve(EPC)and environmental Kuznets curve(EKC)by focusing on the 38 member economies of the Organization for Economic Co-operation and Development(OECD).Using panel data from 2000 to 2021,the study employs several econometric techniques,including fixed effects,feasible generalized least squares,two-stage least squares,and the generalized method of moments.Our primary findings reveal that unemployment has a significant negative impact on CO_(2)emissions,thereby supporting the validity of the EPC hypothesis within OECD countries.This suggests a trade-off between unemployment and reductions in CO_(2)emissions.Similarly,the results validate the EKC hypothesis,with further analysis indicating that the EKC exhibits an N-shaped curve-an important contribution to the literature on environmental dynamics in advanced economies.Additionally,the results show that both trade openness and renewable energy usage have significantly improved environmental quality in OECD economies.Finally,extensive causality testing identifies both one-way and two-way causal relationships among the key variables examined.These findings have important policy implications for the management of environmental quality and macroeconomic variables in the OECD context. 展开更多
关键词 Environmental Phillips curve EPC hypothesis ENVIRONMENTAL Kuznets curve EKC hypothesis Organization for Economic Cooperation and Development OECD Panel data
在线阅读 下载PDF
Deciphering Transition Metal Diffusion in Anode Battery Materials:A Study on Nb Diffusion in Nb_(x)Ti_(1−x)O_(2)
20
作者 Ola Kenji Forslund Carmen Cavallo +7 位作者 Johan Cedervall Jun Sugiyama Kazuki Ohishi Akihiro Koda Alessandro Latini Aleksandar Matic Martin Månsson Yasmine Sassa 《Carbon Energy》 2025年第8期69-75,共7页
Demand for fast-charging lithium-ion batteries(LIBs)has escalated incredibly in the past few years.A conventional method to improve the performance is to chemically partly substitute the transition metal with another ... Demand for fast-charging lithium-ion batteries(LIBs)has escalated incredibly in the past few years.A conventional method to improve the performance is to chemically partly substitute the transition metal with another to increase its conductivity.In this study,we have chosen to investigate the lithium diffusion in doped anatase(TiO_(2))anodes for high-rate LIBs.Substitutional doping of TiO_(2)with the pentavalent Nb has previously been shown to increase the high-rate performances of this anode material dramatically.Despite the conventional belief,we explicitly show that Nb is mobile and diffusing at room temperature,and different diffusion mechanisms are discussed.Diffusing Nb in TiO_(2)has staggering implications concerning most chemically substituted LIBs and their performance.While the only mobile ion is typically asserted to be Li,this study clearly shows that the transition metals are also diffusing,together with the Li.This implies that a method that can hinder the diffusion of transition metals will increase the performance of our current LIBs even further. 展开更多
关键词 BATTERIES DIFFUSION ELECTROCATALYSIS energy storage and conversion muon spin relaxation TiO_(2) transition metal
在线阅读 下载PDF
上一页 1 2 43 下一页 到第
使用帮助 返回顶部