期刊文献+
共找到113篇文章
< 1 2 6 >
每页显示 20 50 100
Performance Analysis of Bandwidth Aware Hybrid Powered 5G Cloud Radio Access Network
1
作者 Md.Al-Hasan Mst.Rubina Aktar +3 位作者 Fahmid Al Farid Md.Shamim Anower Abu Saleh Musa Miah Md.Hezerul Abdul Karim 《Computers, Materials & Continua》 2026年第4期2146-2160,共15页
The rapid growth in available network bandwidth has directly contributed to an exponential increase in mobile data traffic,creating significant challenges for network energy consumption.Also,with the extraordinary gro... The rapid growth in available network bandwidth has directly contributed to an exponential increase in mobile data traffic,creating significant challenges for network energy consumption.Also,with the extraordinary growth of mobile communications,the data traffic has dramatically expanded,which has led to massive grid power consumption and incurred high operating expenditure(OPEX).However,the majority of current network designs struggle to efficientlymanage a massive amount of data using little power,which degrades energy efficiency performance.Thereby,it is necessary to have an efficient mechanism to reduce power consumption when processing large amounts of data in network data centers.Utilizing renewable energy sources to power the Cloud Radio Access Network(C-RAN)greatly reduces the need to purchase energy from the utility grid.In this paper,we propose a bandwidth-aware hybrid energypowered C-RAN that focuses on throughput and energy efficiency(EE)by lowering grid usage,aiming to enhance the EE.This paper examines the energy efficiency,spectral efficiency(SE),and average on-grid energy consumption,dealing with the major challenges of the temporal and spatial nature of traffic and renewable energy generation across various network setups.To assess the effectiveness of the suggested network by changing the transmission bandwidth,a comprehensive simulation has been conducted.The numerical findings support the efficacy of the suggested approach. 展开更多
关键词 5G BANDWIDTH renewable energy energy efficiency spectral efficiency C-RAN
在线阅读 下载PDF
Intensity modifies the association between continuous bouts of physical activity and risk of mortality:A prospective UK Biobank cohort analysis
2
作者 Alex V.Rowlands Fabian Schwendinger +7 位作者 Cameron Razieh Joe Henson Jonathan Goldney Andrew P.Kingsnorth Melanie Davies Kamlesh Khunti Francesco Zaccardi Tom Yates 《Journal of Sport and Health Science》 2026年第2期68-76,共9页
Background:Recent evidence suggests continuous bouts of physical activity(PA)are associated with longevity.We hypothesized the risk of mortality would be lower when the most active minutes of the day were in a continu... Background:Recent evidence suggests continuous bouts of physical activity(PA)are associated with longevity.We hypothesized the risk of mortality would be lower when the most active minutes of the day were in a continuous bout.Methods:PA was assessed using accelerometery in UK Biobank participants.The intensity of the most active continuous(MXCONT)and accumulated(MX)X min of the day,and their ratio(MXRATIO=MXCONT/MX),were determined.MXRATIO indicates how the most active minutes of the day are accumulated,ranging from a single continuous bout through to sporadic accumulation spread across the day.Durations(X)considered ranged from 1 to 20 min.The outcome was mortality.Results:In total,94,541 participants(56.5% female)were included.Over a median(interquartile range)follow-up of 6.9(6.3,7.4)years,2649(2.8%)deaths occurred.Intensity moderated the association between how the most active minutes of the day were accumulated and mortality risk,expressed relative to sporadically accumulated moderate PA.If the most active minutes were of moderate intensity,the risk of mortality was halved for continuous compared to sporadic accumulation,irrespective of duration;if the most active minutes were of vigorous intensity,a continuous bout was associated with the lowest risk for durations under 5 min(e.g.,3 min:hazard ratio(HR)=0.27,95% confidence interval(95%CI):0.21-0.34),while sporadic accumulation was associated with the lowest risk for durations beyond 5 min(HR=0.11,95%CI:0.08-0.15 for the most active 20 min).Conclusion:Optimal PA patterns for reducing mortality differ by intensity and duration.For moderate-intensity PA,a lower mortality risk may be optimized by prioritizing continuous PA for up to 20 min.However,for vigorous-intensity PA,multiple short bouts(<5 min)may be optimal.This suggests tailored PA recommendations may enhance longevity benefits. 展开更多
关键词 Sporadic physicalactivity MX MX_(CONT) ACCELEROMETER
在线阅读 下载PDF
上下盘错动作用下穿越地裂缝综合管廊损伤分析
3
作者 熊仲明 张佳斌 +1 位作者 陈轩 梁家伟 《地下空间与工程学报》 北大核心 2025年第6期2180-2191,共12页
针对地裂缝分布较为密集的城市,地下综合管廊等线性工程不可避免要穿越地裂缝,而地裂缝场地上下盘垂直错动会严重威胁地下综合管廊的安全。为此,以西安市幸福路地下综合管廊为研究背景,建立了土与结构共同作用的三维有限元分析模型,研... 针对地裂缝分布较为密集的城市,地下综合管廊等线性工程不可避免要穿越地裂缝,而地裂缝场地上下盘垂直错动会严重威胁地下综合管廊的安全。为此,以西安市幸福路地下综合管廊为研究背景,建立了土与结构共同作用的三维有限元分析模型,研究了上下盘不同错动量下综合管廊的损伤特征和场地土应力应变的变化,引入了损伤指数建立管廊安全评价分类标准(DS0-DS3),以评估结构损伤。结果表明:管廊受拉损伤区集中在下盘上层舱室、地裂缝处墙体、上盘下层舱室,受压损伤区集中在地裂缝处墙体;受拉损伤控制管廊损伤;管廊结构薄弱位置在上盘为下层大舱底板,在地裂缝处为下层大舱侧墙,在下盘为上层大舱顶板;当错动量达到300 mm,上盘管廊上部土体塑性区向上发展贯穿土体,管廊大部分损伤区达到DS3,出现大面积混凝土剥落,结构失效。 展开更多
关键词 综合管廊 地裂缝 垂直错动 结构损伤 评估
原文传递
城市排水系统实时控制方法及应用研究进展
4
作者 卢金锁 孙焦煜子 +2 位作者 王渲 刘志鹏 况诗祥 《环境工程学报》 北大核心 2025年第6期1283-1295,共13页
随着城市化进程的加速,排水系统的规模与复杂性不断增加,对高效、自动化、节能的控制技术需求日益迫切。本研究系统地梳理了城市排水系统实时控制技术的发展历程、策略生成方法及其面临的主要挑战,详细探讨了实时控制系统的核心组成、... 随着城市化进程的加速,排水系统的规模与复杂性不断增加,对高效、自动化、节能的控制技术需求日益迫切。本研究系统地梳理了城市排水系统实时控制技术的发展历程、策略生成方法及其面临的主要挑战,详细探讨了实时控制系统的核心组成、控制目标及启发式控制和模型预测控制等关键控制方法。同时,本研究强调了基础数据与模型参数获取的困难、系统局限性以及技术和社会经济挑战对实时控制策略选择和系统优化的深远影响。尽管实时控制技术的理论研究取得了一定进展,但其长期运行效能和实际应用中的稳定性仍需进一步探讨。未来研究方向应侧重于控制策略的性能评估、系统对环境变化的适应性及优化算法的改进,以推动实时控制技术在更广泛的应用场景中的落地,促进城市排水系统的智能化与可持续发展。 展开更多
关键词 城市排水系统 优化控制 实时控制 控制策略
原文传递
基于环境参数模型的缓坡光伏阵列反阴影策略研究
5
作者 黄斌 赵伟 +3 位作者 廖力达 肖孟 黄佳亮 星可 《发电技术》 2025年第3期579-589,共11页
【目的】反阴影策略在光伏系统规模化应用中发挥着至关重要的作用。为了应对小坡度地区因光伏阵列间阴影遮挡而导致的发电量损失问题,需要对光伏组件的日跟踪策略进行优化。【方法】以宁夏地区某光伏电站为例,结合地形及环境因素建立缓... 【目的】反阴影策略在光伏系统规模化应用中发挥着至关重要的作用。为了应对小坡度地区因光伏阵列间阴影遮挡而导致的发电量损失问题,需要对光伏组件的日跟踪策略进行优化。【方法】以宁夏地区某光伏电站为例,结合地形及环境因素建立缓坡背景下光伏阵列间动态阴影遮挡计算模型和辐照模型,提出了一种反阴影的平单轴太阳跟踪策略,并利用MATLAB软件构建仿真模型,验证该策略的可行性和有效性。最后,选择典型晴天在现场选区进行试验验证。【结果】在缓坡地形条件下,与采用原始跟踪策略的光伏阵列相比,采用所提反阴影和自动跟踪策略的光伏阵列可减少约12%的阴影遮挡,系统整体发电输出效率可提高约10%。【结论】所提策略从地形和环境因素角度进行优化,有效解决了反阴影跟踪系统的适用性问题,拓宽了光伏电站的选址地域,并为其提供了可靠的技术支撑,在光伏系统规模化应用中具有重要意义。 展开更多
关键词 太阳能 光伏电站 缓坡地形 阴影遮挡 跟踪策略 平单轴系统 发电效益
在线阅读 下载PDF
The dynamics of frequency connectedness between technology ETFs and uncertainty indices under extreme market conditions
6
作者 Oguzhan Ozcelebi Ronald McIver Sang Hoon Kang 《Financial Innovation》 2025年第1期2303-2335,共33页
We examine technology ETF and uncertainty index(VIX,GVZ,and OVZ)spillover dynamics and quantile frequency interconnectedness across market states.This study is the first to use quantile-frequency spillover,quadruple w... We examine technology ETF and uncertainty index(VIX,GVZ,and OVZ)spillover dynamics and quantile frequency interconnectedness across market states.This study is the first to use quantile-frequency spillover,quadruple wavelet coherence,and wavelet quantile correlation methodologies to facilitate these analyses.The total connectedness index value is 70%,which is much higher in both the upper and lower quantiles.Under normal market conditions,short-term connectedness significantly exceeds long-term connectedness.Levels of ETF-uncertainty indicator connectedness increase under extreme market conditions;most technology ETFs are net spillover transmitters and uncertainty indices net spillover receivers,indicating the contagion risk of ETF investments.We show that while greater ETF-uncertainty index connectedness may benefit portfolio diversification,large fluctuations in technology EFTs can result in financial instability due to high market volatility.In the long term,the joint effects of uncertainty indices on ETFs are significant,with negative correlations between ETFs and uncertainties at different frequencies,supporting the potential role of uncertainty indices in hedging technology ETF portfolio risks.Dynamic portfolio rebalancing,scenario analysis,and stress testing may help to manage the effects of high connectedness. 展开更多
关键词 ETFS Uncertainty indexes Quantile-frequency connectedness Wavelet quantile correlation Quadruple wavelet coherence Network analysis
在线阅读 下载PDF
A Transparent Polymer‑Composite Film for Window Energy Conservation
7
作者 Xianhu Liu Haoyu Zhang +3 位作者 Yamin Pan Jun Ma Chuntai Liu Changyu Shen 《Nano-Micro Letters》 2025年第7期1-11,共11页
As living standards improve,the energy consumption for regulating indoor temperature keeps increasing.Windows,in particular,enhance indoor brightness but also lead to increased energy loss,especially in sunny weather.... As living standards improve,the energy consumption for regulating indoor temperature keeps increasing.Windows,in particular,enhance indoor brightness but also lead to increased energy loss,especially in sunny weather.Developing a product that can maintain indoor brightness while reducing energy consumption is a challenge.We developed a facile,spectrally selective transparent ultrahigh-molecular-weight polyethylene composite film to address this trade-off.It is based on a blend of antimony-doped tin oxide and then spin-coated hydrophobic fumed silica,achieving a high visible light transmittance(>70%)and high shielding rates for ultraviolet(>90%)and near-infrared(>70%).When applied to the acrylic window of containers and placed outside,this film can cause a 10℃ temperature drop compared to a pure polymer film.Moreover,in building energy simulations,the annual energy savings could be between 14.1%~31.9%per year.The development of energy-efficient and eco-friendly transparent films is crucial for reducing energy consumption and promoting sustainability in the window environment. 展开更多
关键词 Energy conservation POLYMER Transparent films COMPOSITE Radiative cooling
在线阅读 下载PDF
Aflatoxin B1 contamination level detection in almond kernels through short wave infrared hyperspectral image analysis
8
作者 Md.Ahasan Kabir Ivan Lee +3 位作者 Chandra B.Singh Gayatri Mishra Brajesh Kumar Panda Sang-Heon Lee 《Advanced Agrochem》 2025年第4期363-372,共10页
Aflatoxin B1(AFB1)is a toxic fungal metabolite that contaminates almonds from cultivation to harvesting.It leads to chronic health problems and significant economic loss to the producers.Therefore,a fast and non-invas... Aflatoxin B1(AFB1)is a toxic fungal metabolite that contaminates almonds from cultivation to harvesting.It leads to chronic health problems and significant economic loss to the producers.Therefore,a fast and non-invasive detection technique is crucial for safeguarding food safety by swiftly identifying and eliminating contaminated almonds from the supply chain.Hyperspectral imaging has been explored as a potential non-destructive technology for detecting AFB1.However,the diverse geometries of almonds present a significant challenge on acquired images,thereby impacting the accuracy of the developed prediction and classification models.This study investigates the effectiveness of short-wave infrared(SwIR)hyperspectral imaging combined with deep learning for detecting AFB1 in almonds of varying geometries.Initially,partial least squares regression(PLSR)and support vector machine(SvM)regression models were evaluated for quantification,while SVM and quadratic discriminant analysis(QDA)classifiers were applied for classification.The results indicated that spectral responses varied with almond thickness,making quantification models unreliable for industrial applications.The Competitive Adaptive Reweighted Sampling(CARS)algorithm was employed to identify key spectral features for developing multi-spectral AFB1 classification models to evaluate the feasibility of high-speed,accurate in-line detection.The deep learning approach significantly outperformed traditional machine learning models,with the pre-trained Inception V3 network achieving a cross-validation accuracy of 84.82%,an F1-score of 0.8522,and an area under curve of 0.893.These findings highlight the superiority of deep learning-based hyperspectral imaging for accurate and reliable AFB1 detection in almonds with diverse shapes and thicknesses. 展开更多
关键词 Aflatoxin B1 Almond thickness impact SWIR hyperspectral imaging Inline detection Non-destructive testing
在线阅读 下载PDF
Warm continental subduction initiated by back-arc collapse:Evidence from remote south-west Tasmania
9
作者 Dillon A.Brown Martin Hand +2 位作者 Laura J.Morrissey Justin L.Payne Andrew W.McNeill 《Geoscience Frontiers》 2025年第3期95-118,共24页
The Tasmanian microcontinent,situated along the East Gondwana accretionary margin during the late Neoproterozoic and early Palaeozoic,contains an unequivocal high-pressure metamorphic record comprising key information... The Tasmanian microcontinent,situated along the East Gondwana accretionary margin during the late Neoproterozoic and early Palaeozoic,contains an unequivocal high-pressure metamorphic record comprising key information pertaining to the geodynamics of subduction along the margin.Subduction of the Tasmanian microcontinent is interpreted by some as a response to back-arc basin inversion prior to ophiolite obduction and high-pressure metamorphism during the Cambrian Tyennan Orogeny.However,thermobarometric evidence in support of such a model from rocks once positioned on the subducting continental margin is lacking.Despite occurrences of eclogite-facies mineral assemblages in the strongly deformed Tyennan Region of western Tasmania,garnet-bearing quartzofeldspathic assemblages documented in metasedimentary lithologies from the remote south-west coast of Tasmania have been interpreted as an expression of low-to moderate-pressure metamorphism.We report a strongly overprinted chlorite-quartz-garnet-bearing assemblage from the southern Tyennan Region(Nye Bay)which shows evidence for high-pressure metamorphism.Coarse-grained garnet porphyroblasts contain inclusions of kyanite,muscovite,and rutile,and yield in-situ Lu-Hf dates of c.520 Ma.The cm-scale garnet porphyroblasts are zoned in the major and trace elements,preserving core-rim compositional gradients reflecting garnet growth up-pressure.Aided by mineral equilibria forward modelling,the garnet rim compositions and the Zr content of Cambrian rutile constrain peak metamorphic conditions of∼17.5-19 kbar and∼780-820℃,equivalent to warm subduction thermal gradients between 410-470℃/GPa.Garnet core compositions and the Ti content of quartz inclusions in the garnet cores constrain the pressures and temperatures for garnet nucleation to∼6-7 kbar and∼560-580℃,corresponding to relatively high prograde thermal gradients between 800-965℃/GPa.The thermal gradients determined from the south-west Tasmanian metamorphic record provide a direct window into the progressive evolution of the thermal state of the Cambrian subduction system,with the physical conditions of garnet nucleation potentially reflecting those of subduction initiation.The corresponding warm thermal gradients provide evidence for subduction initiation driven by the collapse of a pre-orogenic back-arc.This interpretation is consistent with an existing tectonic model for the Tyennan Orogeny which proposes a back-arc basin origin for the protoliths to the western Tasmanian sub-ophiolitic metamorphic sole. 展开更多
关键词 High-pressure metamorphism SUBDUCTION BACK-ARC Tyennan Orogeny East Gondwana
在线阅读 下载PDF
QSAR Model of Activated Carbon Adsorption Based on Langmuir Adsorption Isotherm
10
作者 TAN Ting WEI Qunshan +5 位作者 LIU Qiong SHEN Zhemin SONG Xinshan WANG Yuhui CHARLES Nzila CHRISTOPHER W.K.Chow 《Journal of Donghua University(English Edition)》 2025年第6期628-638,共11页
From a quantum chemistry standpoint,the impact of the structural properties of the compounds on activated carbon’s adsorption ability was specifically investigated.The compounds whose adsorption behavior followed the... From a quantum chemistry standpoint,the impact of the structural properties of the compounds on activated carbon’s adsorption ability was specifically investigated.The compounds whose adsorption behavior followed the Langmuir isotherm model were selected as the research objects.An optimal quantitative structure-activity relationship(QSAR)model was built by using the multiple linear regression(MLR)method,with the saturation adsorption capacity Q_(m) from the Langmuir adsorption isotherm as the response variable and the structural parameters of 50 organic compounds as independent variables.The results show that the optimal model exhibits good stability,reliability and robustness,with a regression coefficient R^(2)of 0.88,an adjusted regression coefficient R_(adj)^(2) of 0.87,an internal validation coefficient q^(2) of 0.81,and an external validation coefficient Q_(ext)^(2) of 0.68.The variables included in the optimal model indicate that the polarity of the molecule,the molecular potential energy,and the stability and bonding strength of the organic compound are the main factors affecting the adsorption on activated carbon.The results provide key information for predicting the adsorption capacity of organic compounds on activated carbon and offer a theoretical reference for adsorption treatment in water environments. 展开更多
关键词 quantitative structure-activity relationship(QSAR) ADSORPTION activated carbon multiple linear regression(MLR)
在线阅读 下载PDF
Comment on“Development of an accelerometer age-and sex-specific approach based on population-standardized values for physical activity surveillance:A proof of concept”
11
作者 Alex V.Rowlands Richard P.Troiano 《Journal of Sport and Health Science》 2025年第2期79-81,共3页
Device-based measurements are recommended to improve population-based physical activity(PA)surveillance.1,2However,implementation remains challenging due to lack of consensus on analytical methods,and the most widely ... Device-based measurements are recommended to improve population-based physical activity(PA)surveillance.1,2However,implementation remains challenging due to lack of consensus on analytical methods,and the most widely used“generic”(absolute intensity)cut-point approach has limited generalisability to population-level free-living data.Further,current methods generally fail to account for differences in people's physical capacity. 展开更多
关键词 ACCELEROMETER cut point approach physical activity age specific population standardized analytical methodsand analytical methods sex specific
在线阅读 下载PDF
Seismic response and failure mode of a subway station in a ground fissure area
12
作者 Chen Xuan Wu Yawei +3 位作者 Teng Hongquan Xiong Zhongming Sun Qiren Zhuge Yan 《Earthquake Engineering and Engineering Vibration》 2025年第4期1143-1155,共13页
Ground fissure,as a common geo-hazard,impairs the integrity of the site soil and affects the seismic performance of engineering structures.In this paper,a finite element(FE)model for subway stations in a ground fissur... Ground fissure,as a common geo-hazard,impairs the integrity of the site soil and affects the seismic performance of engineering structures.In this paper,a finite element(FE)model for subway stations in a ground fissure area was developed and validated by using experimental results.Numerical analyses were conducted to investigate the seismic response and failure mode of subway stations in a ground fissure area with different locations.Effects of ground fissure on deformations and internal forces of a station,soil pressures and soil plastic strains were discussed.The results showed that the seismic response of the station was significantly amplified by the ground fissure,and stations in the ground fissure area displayed obvious rocking deformation during earthquakes as compared to those in the area without fissures.It also was found that the soil yielding around the station,the dislocation occurring in the ground fissure area,and the dynamic amplification effect were more significant under vertical ground motion,which weakened the station’s ductility and accelerated its destruction process. 展开更多
关键词 subway station soil-structure-interaction ground fissure seismic response failure mode
在线阅读 下载PDF
基于声发射Ib值分析的渗铝321钢损伤特性研究 被引量:3
13
作者 廖力达 向旭宏 +2 位作者 舒王咏 黄斌 罗晓 《仪器仪表学报》 EI CAS CSCD 北大核心 2024年第1期211-220,共10页
太阳能热发电换热管主要材料渗铝321钢的损伤会导致换热管的寿命缩短甚至断裂,因此必须进行损伤检测。采用声发射方法对渗铝321钢的损伤特性进行分析,实现对换热管性能的在线动态监测。通过采用声发射Ib值特征来表征渗铝321钢的损伤程度... 太阳能热发电换热管主要材料渗铝321钢的损伤会导致换热管的寿命缩短甚至断裂,因此必须进行损伤检测。采用声发射方法对渗铝321钢的损伤特性进行分析,实现对换热管性能的在线动态监测。通过采用声发射Ib值特征来表征渗铝321钢的损伤程度,并运用自组织映射(SOM)神经网络算法进行声发射特征参数聚类,以分析材料的损伤模式。结果表明,力学塑性阶段的声发射事件数量剧增,能量和振铃计数的峰值标志着试件的断裂。此外,在试件失效前,Ib值显著降低且密度变密集,表明Ib值的变化特征可以作为材料临界失效的预警信号。通过SOM算法对特征参数进行聚类分析得到4个簇及其对应的特征频率,并使用扫描电子显微镜(SEM)观察试件的断口形貌,得出4个簇分别对应于孔洞生长与汇合、微裂纹成核、宏观裂纹扩展和纤维状断裂4类损伤模式。这项研究旨在探索金属管材的损伤演化行为,并为管材的损伤分析和健康监测提供依据。 展开更多
关键词 渗铝321钢 声发射 Ib值 SOM神经网络 损伤演化
原文传递
Enhancing clinical and public health interpretation of accelerometer-assessed physical activity with age-referenced values based on UK Biobank data
14
作者 Alex V.Rowlands Andrew P.Kingsnorth +10 位作者 Bjørge H.Hansen Stuart J.Fairclough Lynne M.Boddy Benjamin D.Maylor Henrik R.Eckmann Borja del Pozo Cruz Nathan P.Dawkins Cameron Razieh Kamlesh Khunti Francesco Zaccardi Tom Yates 《Journal of Sport and Health Science》 2025年第1期27-37,共11页
Background Higher accelerometer-assessed volume and intensity of physical activity(PA)have been associated with a longer life expectancy but can be difficult to translate into recommended doses of PA.We aimed to:(a)im... Background Higher accelerometer-assessed volume and intensity of physical activity(PA)have been associated with a longer life expectancy but can be difficult to translate into recommended doses of PA.We aimed to:(a)improve interpretability by producing UK Biobank age-referenced centiles for PA volume and intensity;(b)inform public-health messaging by examining how adding recommended quantities of moderate and vigorous PA affect PA volume and intensity.Methods 92,480 UK Biobank participants aged 43-80 years with wrist-worn accelerometer data were included.Average acceleration and intensity gradient were derived as proxies for PA volume and intensity.We generated sex-specific centile curves using Generalized Additive Models for Location Scale and Shape(GAMLSS)and modeled the effect of adding moderate(walking)or vigorous(running)activity on the combined change in the volume and intensity centiles(change in PA profile).Results In men,volume was lower as age increased while intensity was lower after age 55;in women,both volume and intensity were lower as age increased.Adding 150 min of moderate PA weekly(5×30 min walking)increased the PA profile by 4 percentage points.Defining moderate PA as brisk walking approximately doubled the increase(9 percentage points)while 75 min of vigorous PA weekly(5×15 min running)trebled the increase(13 percentage points).Conclusion These UK Biobank reference centiles provide a benchmark for interpretation of accelerometer data.Application of our translational methods demonstrate that meeting PA guidelines through shorter duration vigorous activity is more beneficial to the PA profile(volume and intensity)than longer duration moderate activity. 展开更多
关键词 Physical activity recommendations Average acceleration Intensity gradient MODERATE Vigorous
在线阅读 下载PDF
Comparison of objectively measured and estimated cardiorespiratory fitness to predict all-cause and cardiovascular disease mortality in adults:A systematic review and meta-analysis of 42 studies representing 35 cohorts and 3.8 million observations
15
作者 Ben Singh Cristina Cadenas-Sanchez +12 位作者 Bruno G.G.da Costa JoséCastro-Pinero Jean-Philippe Chaput Magdalena Cuenca-García Carol Maher Nuria Marín-Jim enez Ryan McGrath Pablo Molina-García Jonathan Myers Bethany Gower Francisco B.Ortega Justin J.Lang Grant R.Tomkinson 《Journal of Sport and Health Science》 2025年第2期135-148,共14页
Background:Cardiorespiratory fitness(CRF)is a powerful health marker recommended by the American Heart Association as a clinical vital sign.Comparing the predictive validity of objectively measured CRF(the"gold s... Background:Cardiorespiratory fitness(CRF)is a powerful health marker recommended by the American Heart Association as a clinical vital sign.Comparing the predictive validity of objectively measured CRF(the"gold standara")and estimated CRF is clinically relevant because estimated CRF is more feasible.Our objective was to meta-analyze cohort studies to compare the associations of objectively measured,exerciseestimated,and non-exercise-estimated CRF with all-cause and cardiovascular disease(CVD)mortality in adults.Methods:Systematic searches were conducted in 9 databases(MEDLINE,SPORTDiscus,Embase,Scopus,PsycINFO,Web of Science,PubMed,CINAHL,and the Cochrane Library)up to April 11,2024.We included full-text refereed cohort studies published in English that quantified the association(using risk estimates with 95%confidence intervals(95%CIs))of objectively measured,exercise-estimated,and non-exercise-estimated CRF with all-cause and CVD mortality in adults.CRF was expressed as metabolic equivalents(METs)of task.Pooled relative risks(RR)for all-cause and CVD mortality per 1-MET(3.5 mL/kg/min)higher level of CRF were quantified using random-effects models.Results:Forty-two studies representing 35 cohorts and 3,813,484 observations(81%male)(362,771 all-cause and 56,471 CVD deaths)were included.The pooled RRs for all-cause and CVD mortality per higher MET were 0.86(95%CI:0.83-0.88)and 0.84(95%CI:0.80-0.87),respectively.For both all-cause and CVD mortality,there were no statistically significant differences in RR per higher MET between objectively measured(RR range:0.86-0.90)and maximal exercise-estimated(RR range:0.85-0.86),submaximal exercise-estimated(RR range:0.91-0.94),and non-exercise-estimated CRF(RR range:0.81-0.85).Conclusion:Objectively measured and estimated CRF showed similar dose-response associations for all-cause and CVD mortality in adults.Estimated CRF could provide a practical and robust alternative to objectively measured CRF for assessing mortality risk across diverse populations.Our findings underscore the health-related benefits of higher CRF and advocate for its integration into clinical practice to enhance risk stratification. 展开更多
关键词 Cardiorespiratory fitness Cardiovascular diseases Cohort studies Risk assessment ADULT
在线阅读 下载PDF
带端板连接可更换耗能梁段的钢框筒结构地震易损性分析 被引量:1
16
作者 苏明周 李蕴杰 +1 位作者 张浩 连鸣 《西安建筑科技大学学报(自然科学版)》 北大核心 2022年第4期491-499,共9页
为研究带端板连接可更换耗能梁段高强钢框筒结构(HSS-SFTS)的地震易损性,采用SAP2000软件建立20层、30层、40层HSS-SFTS典型算例模型,从PEER地震数据库中分别选取40条近场含脉冲型和40条普通远场地震波,基于增量动力法(IDA)获得算例在... 为研究带端板连接可更换耗能梁段高强钢框筒结构(HSS-SFTS)的地震易损性,采用SAP2000软件建立20层、30层、40层HSS-SFTS典型算例模型,从PEER地震数据库中分别选取40条近场含脉冲型和40条普通远场地震波,基于增量动力法(IDA)获得算例在远、近场地震作用下的IDA曲线簇.同时,基于四水准抗震设防目标获得不同极限状态下的地震易损性曲线,并对HSS-SFTS进行地震易损性评估.结果表明:HSS-SFTS算例在四个不同设防水准下的超越概率均小于50%,满足“小震不坏、中震轻度损伤、大震可更换、巨震防倒塌”的抗震设防目标,具有良好的抗震性能;各算例对应不同水准下近场脉冲型地震的超越概率均高于普通远场地震至少20%,表明近场脉冲型地震对结构的塑性损伤程度影响更大. 展开更多
关键词 钢框筒 IDA 地震易损性分析 抗震性能评估
在线阅读 下载PDF
不同焊接工况焊接效应对箱板装配式钢结构加劲墙板的影响 被引量:2
17
作者 门进杰 高睿祥 +3 位作者 李然 兰涛 秦广冲 谭鲁怀 《工业建筑》 北大核心 2023年第1期41-49,134,共10页
通过ABAQUS关联DFLUX热源子程序对Q235B与Q345B钢板进行焊接模拟,并利用超声波检测方法对钢板进行焊接残余应力测试。试验发现:在焊缝热影响区上的纵向残余应力以拉应力为主,在整个焊件上横向残余应力既存在拉应力又存在压应力,且试验... 通过ABAQUS关联DFLUX热源子程序对Q235B与Q345B钢板进行焊接模拟,并利用超声波检测方法对钢板进行焊接残余应力测试。试验发现:在焊缝热影响区上的纵向残余应力以拉应力为主,在整个焊件上横向残余应力既存在拉应力又存在压应力,且试验结果与模拟结果基本吻合,验证了ABAQUS模拟钢板焊接的可靠性。采用相同模拟方法对加劲钢板墙焊接过程进行模拟并对其焊接残余应力、焊接变形以及抗剪承载力进行分析。结果表明:加劲钢板墙的焊接残余应力与焊接变形主要发生在加劲肋与墙板焊缝处,沿焊缝方向上的残余应力均呈现上下两端小、中间大的特点;间断焊接对加劲钢板墙的高残余应力以及整体残余变形影响明显低于连续焊接;在所有焊接工况中,最小极限抗剪承载力与最大极限抗剪承载力相比下降了6.8%;对比所有工况后发现间断距离较大的焊接工况效果更好。 展开更多
关键词 加劲钢板墙 残余应力 残余变形 抗剪承载力 焊接工况
原文传递
水稻秸秆拆解工艺参数优化及纤维自交织结构 被引量:1
18
作者 孙恩惠 彭鵾 +5 位作者 曲萍 靳红梅 雍宬 陈玲 刘歆颖 黄红英 《农业工程学报》 EI CAS CSCD 北大核心 2024年第17期103-110,共8页
大尺寸高长径比纤维是影响非织造秸秆纤维生态毯质量的关键。机械揉搓是获得高长径比纤维的最佳处理技术工艺。该研究探究了揉丝机主轴转速和锤齿间隙对不同含水率秸秆纤维拆解揉丝的影响,其工艺参数为主轴转速、锤齿间隙及物料含水率,... 大尺寸高长径比纤维是影响非织造秸秆纤维生态毯质量的关键。机械揉搓是获得高长径比纤维的最佳处理技术工艺。该研究探究了揉丝机主轴转速和锤齿间隙对不同含水率秸秆纤维拆解揉丝的影响,其工艺参数为主轴转速、锤齿间隙及物料含水率,指标输出为秸秆丝化率与标定单位生产率,并对纤维自交织结构特性进行评价。结果表明,采用Box-Behnken响应面法(response surface method,RSM)开发了一个可确定输入和输出参数间的函数,2种评价指标模型均具有较高的可信度,决定系数分别为R^(2)>0.95,R^(2)>0.84。优化数学模型工艺参数:含水率41.2%,主轴转速2498 r/min,锤齿间隙12.84 mm组合下秸秆丝化率达96.93%,标定单位功率生产率为29.33 kg/(kW?h)。大尺寸高长径比秸秆纤维长度>70 mm和长宽比>80比例增幅分别达120.55%和16.01%,有效改善纤维自交织能力,所开发的RSM模型秸秆的实际揉搓拆解丝化率达96.27%,加工成本降低27.50元/t,可广泛应用于生产大尺寸纤维秸秆基高值农用制品。该研究为生物质秸秆的有效循环利用和高值化材料产业的绿色可持续发展提供重要依据和技术支撑。 展开更多
关键词 秸秆 纤维 参数优化 机械揉搓 高长径比 丝化率 响应面法
在线阅读 下载PDF
搜寻与分享:在线社区用户对新冠疫苗的诉求识别和特征分析 被引量:1
19
作者 柯青 季璐 杜佳 《信息资源管理学报》 CSSCI 2023年第6期110-124,共15页
本研究采集百度贴吧平台上新冠疫苗的数据,依据用户参与在线社区的搜寻和分享行为动机,构建诉求分类框架,将该框架结合BERT深度学习模型和LDA模型,识别用户诉求类型和诉求主题,并在此基础上分析用户对新冠疫苗诉求的信息供需特征和传播... 本研究采集百度贴吧平台上新冠疫苗的数据,依据用户参与在线社区的搜寻和分享行为动机,构建诉求分类框架,将该框架结合BERT深度学习模型和LDA模型,识别用户诉求类型和诉求主题,并在此基础上分析用户对新冠疫苗诉求的信息供需特征和传播特征。研究发现,用户主要以搜寻和分享事实型信息方式来表达信息型诉求和心理型诉求,两类诉求类型关注的诉求主题有共性也有差异,但从供需特征来看呈现出较为严重的数量矛盾和认知隔阂,且诉求类型和诉求主题均不同程度地影响信息传播效应。本研究提出的用户诉求分类框架有助于深入挖掘在线社区信息资源价值,研究结果对建立有效的信息供需机制和舆情控制策略具有参考价值。 展开更多
关键词 信息诉求 新冠疫苗 在线社区 供需特征 传播特征
在线阅读 下载PDF
12.9级高强度螺栓连接外伸端板节点滞回性能研究 被引量:1
20
作者 杨俊芬 何琛 +3 位作者 路朋 刘盼盼 曲凯 贾云龙 《建筑钢结构进展》 CSCD 北大核心 2022年第12期30-40,共11页
通过对3个12.9级高强度螺栓连接端板节点和1个10.9级高强度螺栓连接端板节点的拟静力试验,对节点的破坏模式、滞回性能、承载能力和耗能能力等滞回性能进行了对比分析。结果表明:12.9级高强度螺栓连接端板节点试件破坏时倾向于螺纹处发... 通过对3个12.9级高强度螺栓连接端板节点和1个10.9级高强度螺栓连接端板节点的拟静力试验,对节点的破坏模式、滞回性能、承载能力和耗能能力等滞回性能进行了对比分析。结果表明:12.9级高强度螺栓连接端板节点试件破坏时倾向于螺纹处发生脆性断裂,无明显塑性变形,而10.9级高强度螺栓连接端板节点试件在破坏时表现为受拉区螺栓脱扣;12.9级螺栓可以有效地延缓端板节点刚度的退化,同时提高节点的承载能力;使用12.9级高强度螺栓替代10.9级高强度螺栓能够提高节点的耗能能力,设置端板加劲肋能够提高节点在发生较大塑性变形时的耗能能力。通过有限元计算进一步研究了轴压比、端板厚度和螺栓预紧力等参数对12.9级高强度螺栓端板节点在往复荷载作用下受力性能的影响,分析表明:端板厚度为20 mm时,12.9级和10.9级高强度螺栓连接端板节点的滞回曲线接近,抗震性能相当,而端板厚度为24 mm的12.9级高强度螺栓连接端板节点的抗震性能有明显提高。 展开更多
关键词 12.9级高强度螺栓 外伸端板节点 拟静力试验 滞回性能 有限元模拟
原文传递
上一页 1 2 6 下一页 到第
使用帮助 返回顶部