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Grain size characteristics of the carbonate-free fraction of surface sediments from the Southwest Indian Ridge area and its geological significance 被引量:1
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作者 Qi Jia Dejiang Fan +3 位作者 Xiaoxia Sun Ming Liu Wenqiang Zhang Zuosheng Yang 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2019年第2期34-43,共10页
The carbonate-free fraction of 20 surface sediments collected from the ultraslow-spreading Southwest Indian Ridge(SWIR) was studied by grain size analysis and mineralogical analysis with X-ray powder diffraction(XRD),... The carbonate-free fraction of 20 surface sediments collected from the ultraslow-spreading Southwest Indian Ridge(SWIR) was studied by grain size analysis and mineralogical analysis with X-ray powder diffraction(XRD),stereo microscopy and scanning electron microscopy(SEM). The characteristics of the carbonate-free fraction of the sediments were obtained, and related influential factors were discussed. The results show that the mean grain size of this fraction is in 1.96Φ–8.19Φ, with poorly sorting and unimodal, bimodal or irregular bimodal distribution patterns. Four grain size end members of the fraction are derived with the End Member Model method. The finest end member EM1 shows a significant contribution of terrigenous materials of the aeolian input and sediment carried by the bottom current. End member EM2 with medium size mainly reflects sediment of a siliceous bioclast origin. EM3 and EM4 are interpreted as representing the coarser volcanic materials related to bedrock weathering or volcanic activities. Multi-provenance is the dominant factor controlling the grain size pattern of the carbonate-free fraction of the sediments in that area. In addition, sediment transport processes such as the bottom current and wind are the minor factors that influence the grain size distribution of the carbonate-free fraction sediments. 展开更多
关键词 SOUTHWEST Indian Ocean carbonate-free fraction grain size distribution pattern end MEMBER model PROVENANCE
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A geochemical investigation of the free and carbonate-bound organic matter in the clay-sized fraction of argillaceous source rocks and its significance for biogenic interpretation 被引量:1
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作者 Yue Zhao Jin-Gong Cai +1 位作者 Tian-Zhu Lei Yan Yang 《Petroleum Science》 SCIE CAS CSCD 2018年第4期681-694,共14页
The molecular composition and biomarker distribution of various occurrences of organic matter in argillaceous source rocks developed in fresh and saline lacustrine environments were revealed by successive treatments o... The molecular composition and biomarker distribution of various occurrences of organic matter in argillaceous source rocks developed in fresh and saline lacustrine environments were revealed by successive treatments of solvent extraction followed by acid hydrolysis using gas chromatography–mass spectrometry. The free fraction obtained by solvent extraction provided abundant geochemical information concerning the sedimentary environment, thermal maturity and biogenic origin, and obvious differences existed between fresh and saline lacustrine source rock samples. Our research results indicate that the carbonate-mineral-bound(CM-bound) fraction released by successive acid hydrolysis could also serve as a significant biogenic indicator, as the bicyclic sesquiterpenoids, indicative of Botryococcus braunii origin, were specifically detected in quite high abundance in the acid-soluble fraction. In addition, the light end hydrocarbons were much better preserved in the acid-soluble fraction, and elemental sulfur was only detected in the CM-bound fraction, suggesting a relatively confined environment for the CM-bound fraction, which thus could preserve additional geochemical information compared to that of the free fraction. The CM-bound fraction also exhibited discernable differences between fresh and saline lacustrine samples. Therefore, it can be concluded that comprehensive analysis of free and CM-bound fractions in the argillaceous source rocks can provide a more authentic and objective interpretation of geologic conditions. 展开更多
关键词 Argillaceous source rock Occurrence free fraction CM-bound fraction Bicyclic sesquiterpenoids Botryococcus braunii Biogenic significance
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Effects of free iron oxyhydrates and soil organic matter on copper sorption-desorption behavior by size fractions of aggregates from two paddy soils 被引量:14
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作者 WANG Fang, PAN Genxing, LI Lianqing Institute of Resource, Ecosystem and Environment of Agriculture, Nanjing Agricultural University, Nanjing 210095, China. 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2009年第5期618-624,共7页
Effects of free iron oxyhydrates (Fed) and soil organic matter (SOM) on copper (Cu^2+) sorption-desorption behavior by size fractions of aggregates from two typical paddy soils (Ferric-Accumulic Stagnic Anthro... Effects of free iron oxyhydrates (Fed) and soil organic matter (SOM) on copper (Cu^2+) sorption-desorption behavior by size fractions of aggregates from two typical paddy soils (Ferric-Accumulic Stagnic Anthrosol (Soil H) and Gleyic Stagnic Anthrosol (Soil W)) were investigated with and without treatments of dithionite-citrate-bicarbonate and of H2O2. The size fractions of aggregates were obtained from the undisturbed bulk topsoil using a low energy ultrasonic dispersion procedure. Experiments of equilibrium sorption and subsequent desorption were conducted at soil water ratio of 1:20, 25℃. For Soil H, Cu^2+ sorption capacity of the DCB-treated size fractions was decreased by 5.9% for fine sand fraction, by 40.4% for coarse sand fraction, in comparison to 2.9% for the bnlk sample. However, Cu^2+ sorption capacities of the H2O2-treated fractions were decreased by over 80% for the coarse sand fraction and by 15% for the clay-sized fraction in comparison to 88% for bulk soil. For Soil W, Cu^2+ sorption capacity of the DCB-treated size fraction was decreased by 30% for the coarse sand fraction and by over 75% for silt sand fraction in comparison to 44.5% for the bulk sample. Cu^2+ sorption capacities of the H2O2-treated fractions were decreased by only 2.0% for the coarse sand fraction and by 15% for the fine sand fraction in comparison to by 3.4% for bulk soil. However, Cu^2+ desorption rates were increased much in H2O2-treated samples by over 80% except the clay-sized fraction (only 9.5%) for Soil H. While removal of SOM with H2O2 tendend to increase the desorption rate, DCB- and H2O2-treatments caused decrease in Cu^2+ retention capacity of size fractions, Particularly, there hardly remained Cu^2+ retention capacity by size fractions from Soil H after H2O2 treatment except for clay-sized fraction. These findings supported again the dominance of the coarse sand fraction in sorption of metals and the preference of absorbed metals bound to SOM in differently stabilized status among the size fractions. Thus, enrichment and turnover of SOM in paddy soils may have great effects on metal retention and chemical mobility in paddy soils. 展开更多
关键词 paddy soils Cn^2+ sorption-desorption soil organic matter free iron oxyhydrates size fraction of aggregates
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鄂尔多斯盆地石炭系本溪组煤岩解析气甲烷碳同位素特征及其地质意义 被引量:1
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作者 张道锋 孟康 +8 位作者 黄有根 王华 郑小鹏 胡薇薇 刘燕 刘宝宪 何梦卿 王冰 李诚 《天然气地球科学》 北大核心 2025年第9期1728-1740,共13页
针对煤岩气产出过程中游离气和吸附气转化过程不清等问题,以鄂尔多斯盆地纳林河、米脂北和绥德地区18口钻井岩心的石炭系本溪组8^(#)煤岩为研究对象,开展煤岩气解析过程中甲烷碳同位素变化特征分析,揭示煤岩气释放过程中游离气/吸附气... 针对煤岩气产出过程中游离气和吸附气转化过程不清等问题,以鄂尔多斯盆地纳林河、米脂北和绥德地区18口钻井岩心的石炭系本溪组8^(#)煤岩为研究对象,开展煤岩气解析过程中甲烷碳同位素变化特征分析,揭示煤岩气释放过程中游离气/吸附气值的动态变化,并结合煤岩显微组分、成熟度、孔隙度和含气量特征,初步探讨煤岩气中游离气/吸附气值差异成因。结果表明:本溪组8^(#)煤岩解析气δ^(13)C_(1)值随解析时间增加呈逐渐增高趋势,由解析初期-44.3‰~-30.2‰增高至解析末期-25.6‰~-10.7‰,增高程度达12.6‰~22.5‰。根据煤岩解析气δ^(13)C_(1)值在不同解析时间范围内的变化特征差异,将煤岩气δ^(13)C_(1)解析曲线划分为4种类型:(1)Ⅰ型:δ^(13)C_(1)值先保持相对稳定再持续缓慢增高;(2)Ⅱ型:δ^(13)C_(1)值先保持相对稳定,再快速增高至一定程度后继续轻微增高;(3)Ⅲ型:δ^(13)C_(1)持续增高;(4)Ⅳ型:δ^(13)C_(1)快速增高到一定程度后再轻微增高。进一步结合CH_(4)运移过程中碳同位素分馏机理,揭示了煤岩气解析过程包含3个阶段。第一阶段:CH_(4)呈游离态在压差驱动下以达西渗流为主,该阶段δ^(13)C_(1)值保持相对稳定;第二阶段:解析初期CH_(4)同时包括游离态和吸附态,而随着解析过程进行,岩心内压力下降引起吸附/解吸作用增强,吸附态CH_(4)占比持续增加,该阶段δ^(13)C_(1)值持续增大;第三阶段:岩心内残留少量吸附态CH_(4)发生缓慢解吸,并可能伴有浓度差驱动的扩散作用,该阶段δ^(13)C_(1)值轻微增大。其中,δ^(13)C_(1)解析曲线呈Ⅰ型和Ⅱ型的煤岩气因具有解析第一阶段,故具有相对较高的游离气/吸附气值。鄂尔多斯盆地本溪组8^(#)煤岩气中游离气/吸附气值越高,煤岩含气量越大。游离气/吸附气值与煤岩成熟度和孔隙度之间存在正相关性。同时,优质的储盖组合(灰岩—煤岩和泥岩—煤岩)可对煤岩储层形成压力封闭,使煤岩气具有较高的游离气/吸附气值。 展开更多
关键词 煤岩 解析气 甲烷碳同位素 碳同位素分馏 游离气/吸附气值
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Element-free Galerkin (EFG) method for analysis of the time-fractional partial differential equations
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作者 Ge Hon-Xia Liu Yong-Qing Cheng Rong-Jun 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第1期46-51,共6页
The present paper deals with the numerical solution of time-fractional partial differential equations using the element-free Galerkin (EFG) method, which is based on the moving least-square approximation. Compared w... The present paper deals with the numerical solution of time-fractional partial differential equations using the element-free Galerkin (EFG) method, which is based on the moving least-square approximation. Compared with numerical methods based on meshes, the EFG method for time-fractional partial differential equations needs only scattered nodes instead of meshing the domain of the problem. It neither requires element connectivity nor suffers much degradation in accuracy when nodal arrangements are very irregular. In this method, the first-order time derivative is replaced by the Caputo fractional derivative of order α(0 〈 α≤ 1). The Galerkin weak form is used to obtain the discrete equations, and the essential boundary conditions are enforced by the penalty method. Several numerical examples are presented and the results we obtained are in good agreement with the exact solutions. 展开更多
关键词 element-free Galerkin (EFG) method meshless method time fractional partial differential equations
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基于分子模拟的废食用油组分在老化沥青中的扩散特性研究
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作者 陈美祝 马佳萌 +2 位作者 赵月超 贺俊 于静君 《化工新型材料》 北大核心 2025年第11期207-214,223,共9页
采用分子动力学方法构建了老化沥青与废食用油不同组分的分子模型,以及废食用油不同组分在老化沥青中的扩散模型。结合密度泛函理论研究了废食用油不同组分的分子极性和不同探测半径下的自由体积分数,探明了废食用油不同组分在老化沥青... 采用分子动力学方法构建了老化沥青与废食用油不同组分的分子模型,以及废食用油不同组分在老化沥青中的扩散模型。结合密度泛函理论研究了废食用油不同组分的分子极性和不同探测半径下的自由体积分数,探明了废食用油不同组分在老化沥青中扩散特性的差异。结果表明:废食用油组分中轻质油的自由体积分数比重质油大0.0012/ps以上,分子极性也低于重质油,即轻质油分子的孔穴较多,分子间相互作用相对较弱;同时发现轻质油和重质油的扩散系数均随温度升高而增大,二者的增长率分别为9.298×10^(-42)/(ps·K)和5.365×10^(-42)/(ps·K),即轻质油的扩散系数受温度影响更显著,表明低极性和高自由体积分数的废食用油组分在高温施工环境下更容易在老化沥青中扩散。 展开更多
关键词 老化沥青 废食用油组分 分子动力学 自由体积分数 扩散特性
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基于改进分数阶非奇异终端滑模方法的感应电机转速控制 被引量:1
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作者 郑长森 刘旭东 《电气工程学报》 北大核心 2025年第2期140-148,共9页
为了优化感应电机控制系统性能,提出一种基于分数阶非奇异终端滑模控制方法的感应电机转速控制策略。首先,建立了考虑电机参数摄动和外部扰动下的超局部模型;然后基于分数阶理论与滑模控制设计了分数阶非奇异终端滑模控制器,提高了系统... 为了优化感应电机控制系统性能,提出一种基于分数阶非奇异终端滑模控制方法的感应电机转速控制策略。首先,建立了考虑电机参数摄动和外部扰动下的超局部模型;然后基于分数阶理论与滑模控制设计了分数阶非奇异终端滑模控制器,提高了系统动态响应速度且能有效抑制滑模抖振,此外,控制器采用非级联控制结构替代了传统的转速环和电流环控制,简化了控制器结构;进而采用非线性扰动观测器来估计系统未知扰动,并通过Lyapunov定理证明了系统的稳定性;最后与传统控制方法进行了试验对比,结果表明,该控制方法可以有效提高系统动态性能,且具有更好的抗干扰能力和稳态精度。 展开更多
关键词 感应电机 无模型 分数阶 非奇异终端滑模控制 非线性扰动观测器
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深部煤岩气产出过程碳同位素分馏与吸附气/游离气产出规律
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作者 端祥刚 李文镖 +6 位作者 胡志明 王峻 赵群 夏勇辉 马占荣 许莹莹 孙明岩 《石油勘探与开发》 北大核心 2025年第5期1166-1179,共14页
以鄂尔多斯盆地榆林和大吉地区深部煤岩气为研究对象,选取石炭系本溪组不同割理/裂缝发育程度的全直径煤岩样品,开展煤岩气全生命周期衰竭开发物理模拟和同位素监测实验,基于实验结果构建割理/裂缝-基质孔耦合的双重介质同位素分馏模型... 以鄂尔多斯盆地榆林和大吉地区深部煤岩气为研究对象,选取石炭系本溪组不同割理/裂缝发育程度的全直径煤岩样品,开展煤岩气全生命周期衰竭开发物理模拟和同位素监测实验,基于实验结果构建割理/裂缝-基质孔耦合的双重介质同位素分馏模型,并建立游离气产出规律评价方法,揭示深部煤岩气开发过程碳同位素分馏机理及吸附气、游离气产出特征。研究表明:深部煤岩气开发过程中碳同位素存在“稳定(Ⅰ)→变轻(Ⅱ)→变重(Ⅲ)”的3阶段分馏特征,第Ⅲ阶段边界压力的快速降低会导致同位素值出现“快速变轻后继续变重”的波动特征,呈现游离气优先动用、吸附气长期供给的特点;同位素分馏模型能够较好地同时拟合实测气体压力、累产气量和产出气δ^(13)C_(1)值,煤岩样品同位素分馏前两阶段累产气以游离气为主,在压降缓慢的生产中后期通过阶段式逐级控压开采方式能有效提高气体采收程度;吸附气动用主要受控于岩石的吸附能力和次级渗流通道,在生产后期有效提高吸附气的动用程度仍是深部煤岩气保持稳产和提高采收率的关键。 展开更多
关键词 深部煤岩气 同位素分馏 物理模拟实验 吸附气 游离气 气体产出比例
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Exploring properties of hyperbranched polymers in anion exchange membranes for fuel cells and its potential integration for water electrolysis:A review
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作者 Tamilazhagan Palanivel Mohamed Mamlouk +1 位作者 Bruno G.Pollet Rajangam Vinodh 《Journal of Energy Chemistry》 2025年第3期670-702,共33页
Anion-exchange membrane water electrolysers(AEMWEs)and fuel cells(AEMFCs)are critical technologies for converting renewable resources into green hydrogen(H_(2)),where anion-exchange membranes(AEMs)play a vital role in... Anion-exchange membrane water electrolysers(AEMWEs)and fuel cells(AEMFCs)are critical technologies for converting renewable resources into green hydrogen(H_(2)),where anion-exchange membranes(AEMs)play a vital role in efficiently transporting hydroxide ions(OH^(-))and minimizing fuel crossover,thus enhancing overall efficiency.While conventional AEMs with linear,side-chain,and block polymer architectures show promise through functionalization,their long-term performance remains a concern.To address this,hyperbranched polymers offer a promising alternative due to their three-dimensional structure,higher terminal functionality,and ease of functionalization.This unique architecture provides interconnected ion transport pathways,fractional free volume,and enhanced long-term stability in alkaline environments.Recent studies have achieved conductivities as high as 304.5 mS cm^(-1),attributed to their improved fractional free volume and microphase separation in hyperbranched AEMs.This review explores the chemical,mechanical,and ionic properties of hyperbranched AEMs in AEMFCs and assesses their potential for application in AEMWEs.Strategies such as blending and structural functionalisation have significantly improved the properties by promoting microphase separation and increasing the density of cationic groups on the polymer surface.The review provides essential insights for future research,highlighting the challenges and opportunities in developing high-performance hyperbranched AEMs to advance hydrogen energy infrastructure. 展开更多
关键词 HYDROGEN Hyperbranched anion exchange membrane Anion exchange membrane fuel cell Alkaline stability Micropha seseparation fractional free volume Anion exchange membrane water electrolysers
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分数阶黏弹性地基上非贯穿裂纹板的自由振动
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作者 王刚 魏培君 +1 位作者 周小利 张骏 《力学季刊》 北大核心 2025年第1期151-161,共11页
本文研究了分数阶黏弹性地基上非贯穿裂纹板的自由振动问题.首先,引入分数阶导数,建立分数阶黏弹性地基模型.接着针对四边简支板研究含贯穿裂纹情形的自由振动问题,在此基础上将贯穿裂纹推广到非贯穿裂纹.基于能量释放率和应力强度因子... 本文研究了分数阶黏弹性地基上非贯穿裂纹板的自由振动问题.首先,引入分数阶导数,建立分数阶黏弹性地基模型.接着针对四边简支板研究含贯穿裂纹情形的自由振动问题,在此基础上将贯穿裂纹推广到非贯穿裂纹.基于能量释放率和应力强度因子的关系得到两种情况下裂纹引起的附加转角,并进一步导出两种情况下裂纹等效扭转弹簧的柔度系数.最终,根据边界条件得到复固有频率.通过具体算例,讨论了黏弹性地基的分数阶系数、黏性系数以及裂纹位置和裂纹深度等参数对复固有频率和振型的影响规律. 展开更多
关键词 分数阶 黏弹性地基 裂纹板 非贯穿裂纹 自由振动
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孕妇外周血胎儿游离DNA浓度与妊娠期高血压的关联性分析
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作者 邓泽桦 孙有鹏 +4 位作者 温丽娟 钟佳通 胡亮 蒋国治 刘维强 《中国产前诊断杂志(电子版)》 2025年第2期1-6,共6页
目的分析孕妇外周血胎儿游离DNA浓度(fetal fraction,FF)在不同孕周的分布情况,探讨胎儿游离DNA对妊娠期高血压(gestational hypertension,GH)的预测价值。方法收集2018年1月至2022年3月于汕头大学医学院附属深圳妇儿医院接受无创产前筛... 目的分析孕妇外周血胎儿游离DNA浓度(fetal fraction,FF)在不同孕周的分布情况,探讨胎儿游离DNA对妊娠期高血压(gestational hypertension,GH)的预测价值。方法收集2018年1月至2022年3月于汕头大学医学院附属深圳妇儿医院接受无创产前筛查(noninvasive prenatal screening,NIPS)检测的26903例孕妇的临床资料进行回顾性分析。统计分析各个孕周的胎儿游离DNA浓度(fetal fraction),对低胎儿DNA浓度、高胎儿DNA浓度等不同胎儿游离DNA浓度组的妊娠期高血压发病率进行比较。结果FF在孕20周时出现上升趋势,在孕22周开始FF增加显著,相比孕19周及之前FF水平差异具有统计学意义(P<0.05);孕15、16、17、19~20周的低FF组GH发病率显著高于正常FF组,差异具有统计学意义;FF<3.5%组GH发病率显著高于正常FF组,差异具有统计学意义,相对风险(relative risk),RR=4.14(95%CI:2.61-6.57,P<0.001);未发现高FF组与正常FF组的GH发病率存在显著差异。结论低FF对妊娠期高血压有一定的预测价值,FF越低,发生妊娠期高血压的风险可能越大。 展开更多
关键词 胎儿游离DNA 胎儿分数 妊娠期高血压 妊娠并发症
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无创产前筛查中影响胎儿游离DNA浓度的因素研究进展
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作者 魏智芳(综述) 侯东霞 王晓华(审校) 《检验医学与临床》 2025年第6期850-854,859,共6页
胎儿游离DNA浓度(FF)通过结合生物因素和生物信息算法解读无创产前筛查(NIPT)结果,是NIPT的重要质量控制参数。不同个体间FF水平存在差异,任何潜在干扰母体或胎盘中游离DNA浓度的因素,都可能进一步影响NIPT结果的准确性。然而目前对于... 胎儿游离DNA浓度(FF)通过结合生物因素和生物信息算法解读无创产前筛查(NIPT)结果,是NIPT的重要质量控制参数。不同个体间FF水平存在差异,任何潜在干扰母体或胎盘中游离DNA浓度的因素,都可能进一步影响NIPT结果的准确性。然而目前对于已知影响FF的因素仍未形成广泛共识。该文将重点探讨影响NIPT结果的生物因素,涵盖母体及胎儿自身因素,同时对FF的意义进行分析,以期加深对此关键指标的全面理解,进而有助于临床医生通过分析个体差异,为筛查对象定制个性化的采血时机,从而提高NIPT的准确率及临床应用效果。此外,深入研究FF的意义也将是未来的一个热点趋势,有望揭示其在预测不良妊娠结局方面的潜在价值。 展开更多
关键词 无创产前筛查 非整倍体 胎儿游离DNA 胎儿分数 质量控制
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大气中氨基酸的来源及氮同位素分馏机制
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作者 朱仁果 肖化云 《地学前缘》 北大核心 2025年第3期362-374,共13页
近年来气溶胶中包括游离态氨基酸(FAAs)和结合态氨基酸(CAAs)在内的蛋白质类物质已被广泛关注。这是因为氨基酸在全球气候变化、空气污染物的去除效率、大气氮的生物利用性、二次有机气溶胶的形成以及对人体健康的影响等方面发挥着重要... 近年来气溶胶中包括游离态氨基酸(FAAs)和结合态氨基酸(CAAs)在内的蛋白质类物质已被广泛关注。这是因为氨基酸在全球气候变化、空气污染物的去除效率、大气氮的生物利用性、二次有机气溶胶的形成以及对人体健康的影响等方面发挥着重要作用。本文将重点阐述氨基酸单体的稳定氮同位素这一新技术在示踪大气氨基酸来源和转化过程中的应用,综述潜在大气释放源中氨基酸单体的稳定氮同位素特征及其在燃烧和大气过程中的稳定氮同位素分馏机制。在未来的工作中需进一步研究不同粒径大小、不同气象条件下和特殊污染事件中的氨基酸单体的同位素分馏机制,这将有助于阐明氨基酸在云和降水形成、气候变化以及污染事件中所发挥的作用和贡献。 展开更多
关键词 游离态氨基酸 结合态氨基酸 稳定氮同位素 分馏机制
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Sufficient and Necessary Condition of Admissibility for Fractional-order Singular System 被引量:15
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作者 YU Yao JIAO Zhuang SUN Chang-Yin 《自动化学报》 EI CSCD 北大核心 2013年第12期2160-2164,共5页
这份报纸与顺序为部分顺序的单个系统集中于考虑条件吗?(0, 1 ) 。整齐的定义,没有推动并且考虑被给第一,然后,为部分顺序的单个系统的考虑的一个足够、必要的条件被建立。一个数字例子被包括说明建议条件。
关键词 奇异系统 分数阶 充要条件 可容许 充分必要条件
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A multidimensional subdiffusion model:An arbitrage-free market
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作者 李国华 张红 罗懋康 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第12期561-567,共7页
To capture the subdiffusive characteristics of financial markets, the subordinated process, directed by the inverse α-stale subordinator Sα (t) for 0 〈 α〈 1, has been employed as the model of asset prices. In t... To capture the subdiffusive characteristics of financial markets, the subordinated process, directed by the inverse α-stale subordinator Sα (t) for 0 〈 α〈 1, has been employed as the model of asset prices. In this article, we introduce a multidimensional subdiffusion model that has a bond and K correlated stocks. The stock price process is a multidimen- sional subdiffusion process directed by the inverse a-stable subordinator. This model describes the period of stagnation for each stock and the behavior of the dependency between multiple stocks. Moreover, we derive the multidimensional fractional backward Kolmogorov equation for the subordinated process using the Laplace transform technique. Finally, using a martingale approach, we prove that the multidimensional subdiffusion model is arbitrage-free, and also gives an arbitrage-free pricing rule for contingent claims associated with the martingale measure. 展开更多
关键词 SUBORDINATION arbitrage-free contingent claim valuation fractional backward Kol-mogorov equation
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Determination of One Unknown Thermal Coefficient through the One-Phase Fractional Lam&eacute;-Clapeyron-Stefan Problem
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作者 Domingo Alberto Tarzia 《Applied Mathematics》 2015年第13期2182-2191,共10页
We obtain explicit expressions for one unknown thermal coefficient (among the conductivity, mass density, specific heat and latent heat of fusion) of a semi-infinite material through the one-phase fractional Lamé... We obtain explicit expressions for one unknown thermal coefficient (among the conductivity, mass density, specific heat and latent heat of fusion) of a semi-infinite material through the one-phase fractional Lamé-Clapeyron-Stefan problem with an over-specified boundary condition on the fixed face . The partial differential equation and one of the conditions on the free boundary include a time Caputo’s fractional derivative of order . Moreover, we obtain the necessary and sufficient conditions on data in order to have a unique solution by using recent results obtained for the fractional diffusion equation exploiting the properties of the Wright and Mainardi functions, given in: 1) Roscani-Santillan Marcus, Fract. Calc. Appl. Anal., 16 (2013), 802 - 815;2) Roscani-Tarzia, Adv. Math. Sci. Appl., 24 (2014), 237 - 249 and 3) Voller, Int. J. Heat Mass Transfer, 74 (2014), 269 - 277. This work generalizes the method developed for the determination of unknown thermal coefficients for the classical Lamé-Clapeyron-Stefan problem given in Tarzia, Adv. Appl. Math., 3 (1982), 74 - 82, which is recovered by taking the limit when the order . 展开更多
关键词 free BOUNDARY Problems fractionAL Diffusion Lamé-Clapeyron-Stefan Problem UNKNOWN Thermal Coefficients EXPLICIT Solution Over-Specified BOUNDARY Condition
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Accelerated Hyper Fractionated Radiotherapy in Localized Ewing’s Sarcoma with or without Surgery: What’s New? A Phase II Study
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作者 Amal Rayan Ahmed Soliman +2 位作者 Khalid F. Riad Asmaa M. Zahran Hosam A. Hasan 《Journal of Cancer Therapy》 2018年第10期820-826,共7页
Background and aim of work: We aimed from this study to determine the response and local relapse free survival (RFS) of pediatric patients with localized Ewing’s sarcoma treated with accelerated hyper-fractionated RT... Background and aim of work: We aimed from this study to determine the response and local relapse free survival (RFS) of pediatric patients with localized Ewing’s sarcoma treated with accelerated hyper-fractionated RT. Patient and methods: This study was a nonrandomized uncontrolled phase II study and was conducted at clinical oncology department and south Egypt cancer institute;it involved 28 patients with histologically confirmed Ewing’s sarcoma;all of them were subjected to PET/CT whenever possible or MRI with contrast of the primary site, MSCT chest, bone scan, and LDH to ensure absence of metastasis followed by the protocol of accelerated hyper fractionated RT. Results: The overall response rate (ORR) was 92.9% by MRI with significant effect of the type of response on local RFS (P 0.002). The median local RFS of 28 patients with localized Ewing’s sarcoma was 30 ± 8.599 months with 95% CI = 13.147 - 46.853;the 3-year local control was 35%. Conclusion: Accelerated hyper fractionated RT didn’t achieve better results than standard fractionation RT, but it is recommended to be done on a large sample size, and multiple centers, and continued follow up is also recommended to evaluate 5-year LRFS, 5-year OS. 展开更多
关键词 ACCELERATED HYPER fractionated RT Ewing’s SARCOMA RELAPSE free Survival
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Instantaneous wave-free ratio(iFR) to determine hemodynamically significant coronary stenosis: A comprehensive review 被引量:1
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作者 Stefan Baumann Leonard Chandra +4 位作者 Elizaveta Skarga Matthias Renker Martin Borggrefe Ibrahim Akin Dirk Lossnitzer 《World Journal of Cardiology》 2018年第12期267-277,共11页
Coronary angiography is considered to be the gold standard in the morphological evaluation of coronary artery stenosis. The morphological assessment of the severity of a coronary lesion is very subjective. Thus, the i... Coronary angiography is considered to be the gold standard in the morphological evaluation of coronary artery stenosis. The morphological assessment of the severity of a coronary lesion is very subjective. Thus, the invasive fractional flow reserve(FFR) measurement represents the current standard for estimation of the hemodynamic significance of coronary artery stenosis. The FFR-guided revascularization strategy was initially classified as a Class-IA-recommendation in the 2014 European Society of Cardiology/European Association for Cardio-Thoracic Surgery guidelines on myocardial revascularization. Both the Deferral vs Performance of Percutaneous Coronary Intervention of Functionally Non-Significant Coronary Stenosis and Flow Reserve vs Angiography for Multivessel Evaluation studies showed no treatment advantage for hemodynamically insignificant stenoses. With the help of FFR(and targeted interventions), clinical results could be improved; however, the use in clinical practice is still limited due to the need of adenosine administration and a significant prolongation of the length of the procedure. Instantaneous wave-free ratio(iFR~) is a new innovative approach for the determination of the hemodynamic significance of coronary stenosis, which can be obtained at rest without the use of vasodilators. Regarding the periprocedural complications as well as prognosis, iFR~ showed non-inferiority to FFR in the SWEDEHEART and DEFINE-FLAIR trials. Furthermore, iFR~, enhanced by iFR~-pullback, provides the possibility to display the iFR~-change over the course of the vessel to create a hemodynamic map. 展开更多
关键词 CORONARY STENOSIS CORONARY ANGIOGRAPHY fractional flow reserve Instantaneous wave-free RATIO Myocardial ischemia CORONARY REVASCULARIZATION
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聚酰亚胺膜材料分子结构设计强化CO_(2)渗透性研究进展
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作者 张子佳 仇昕月 +4 位作者 孙翔 罗志斌 罗海中 贺高红 阮雪华 《化工学报》 EI CSCD 北大核心 2024年第4期1137-1152,共16页
膜技术基于渗透性差异实现天然气无相变脱碳,节能优势显著,此外膜装置的模块化制造可以灵活应对非常规天然气开采规模的大幅变化。聚酰亚胺(PI)是一种广泛研究的玻璃态聚合物膜材料,脱碳选择性较高、化学稳定性好,近年来在天然气脱碳领... 膜技术基于渗透性差异实现天然气无相变脱碳,节能优势显著,此外膜装置的模块化制造可以灵活应对非常规天然气开采规模的大幅变化。聚酰亚胺(PI)是一种广泛研究的玻璃态聚合物膜材料,脱碳选择性较高、化学稳定性好,近年来在天然气脱碳领域已实现工业应用。尽管如此,通过分子结构设计提升聚酰亚胺膜的渗透性,从而大幅降低膜装置建设成本和占地面积,仍是未来的重要研究方向。从气体在玻璃态聚合物膜中的渗透传质机制出发,归纳总结了芳香族聚酰亚胺在链段构型与柔顺性、大位阻侧基、主链轴节结构等方面的设计进展以及膜材料自由体积分数和气体渗透系数随之发生变化的内在规律,对聚酰亚胺膜材料分子结构设计的未来发展方向进行了展望,兼顾考虑自由体积分数和自由体积空穴尺寸分布范围是同时提高渗透性和选择性的重要途径。 展开更多
关键词 天然气脱碳 膜分离 聚酰亚胺 分子结构 渗透性 自由体积
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非标记定量方法研究糖尿病患者血清差异蛋白
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作者 刘雅雯 冯里茹 +1 位作者 胡绪乔 洪文旭 《中国热带医学》 CAS 北大核心 2024年第3期320-325,共6页
目的应用非标记定量技术研究糖尿病患者血清中差异表达蛋白,筛选特异性蛋白质标志物。方法收集2023年深圳市糖尿病患者和健康对照者的血清各3例,应用免疫亲和层析和纳升液相色谱-四极杆-静电场轨道线性离子阱三合一质谱法,利用分级(frac... 目的应用非标记定量技术研究糖尿病患者血清中差异表达蛋白,筛选特异性蛋白质标志物。方法收集2023年深圳市糖尿病患者和健康对照者的血清各3例,应用免疫亲和层析和纳升液相色谱-四极杆-静电场轨道线性离子阱三合一质谱法,利用分级(fraction,FC)和不分级(no fraction,NF)2种方法对糖尿病患者和健康对照者的血清蛋白质组进行非标记定量分析,质谱数据经MaxQuant1.6.1.0进行检索,对分级方法鉴定的差异蛋白质进行GO(gene oncology)功能聚类分析和KEGG(kyoto encyclopedia of genes and genomes)通路分析。结果未分级方法鉴定可信蛋白251种,筛选差异蛋白17种;分级方法鉴定可信蛋白494种,筛选差异蛋白74种。其中7种蛋白在2种方法中变化趋势完全一致。有5种蛋白下调,分别是妊娠区带蛋白(pregnancy zone protein,PZP)、碳酸酐酶1(carbonic anhydrase 1,CAH1)、甘露糖结合蛋白C(mannose-binding protein C,MBL2)、纤维蛋白原α链(fibrinogen alpha chain,FIBA)和触珠蛋白(haptoglobin,HPT);2种蛋白上调,分别是脂蛋白a[apolipoprotein(a),LPA]和补体因子H相关蛋白4(complement fac‐tor H-related protein 4,CFH4)。GO分析显示差异蛋白的分子功能主要集中在糖胺聚糖结合、肝素结合等过程。KEGG通路分析显示差异蛋白主要集中在补体和级联凝血、细胞黏附、PI3K-Akt信号通路等通路上。结论基于分级的非标记定量蛋白质组学分析技术可有效分析糖尿病患者血清蛋白的差异表达,为筛选大规模队列疾病血清样本的特异性蛋白质标志物提供了有效技术手段。 展开更多
关键词 非标记定量 糖尿病 血清 蛋白组学 分级
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