Hybrid absorbing boundary condition based on transmitting boundary and its application in 3D fractional viscoacoustic modeling

An accurate numerical simulation for wave equations is essential for understanding of wave propagation in the earth's interior as well as full waveform inversion and reverse time migration. However, due to computational cost and hardware capability limitations, numerical simulations are often performed within a finite domain. Thus, an adequate absorbing boundary condition (ABC) is indispensable for obtaining accurate numerical simulation results. In this study, we develop a hybrid ABC based on a transmitting boundary, which is referred to as THABC, to eliminate artificial boundary reflections in 3D second-order fractional viscoacoustic numerical simulations. Furthermore, we propose an adaptive weighted coefficient to reconcile the transmitting and viscoacoustic wavefields in THABC. Through several numerical examples, we determine that the proposed THABC approach is characterized by the following benefits. First, with the same number of absorbing layers, THABC exhibits a better ability in eliminating boundary reflection than traditional ABC schemes. Second, THABC is more effective in computation, since it only requires the wavefields at the current and last time steps to solve the transmitting formula within the absorbing layers. Benefiting from a simple but effective combination between the transmitting equation and the second-order wave equation, our scheme performs well in the 3D fractional Laplacian viscoacoustic numerical simulation.

Construction of voxel-based Portunus haanii phantom and its absorbed fractions and specific absorbed fractions calculation based on Monte Carlo simulations

Objective:To build the database of the absorbed fractions(AFs)and specific absorbed fractions(SAFs),in order to accurately assess the internal radiation dose in non-human biota.Methods:A voxel-based Portunus haanii phantom was established based on the computed tomography(CT)images.A set of AFs and SAFs were calculated with Monte Carlo toolkit Geant4 for the emission of monoenergetic photons and electrons with energies ranging from 10 keV to 5 MeV.Results:The mass of the voxel-based Portunus haanii phantom(392.2 g)was in agreement with the actual mass(389.2 g),indicating the reliability of the phantom.The calculated AFs and SAFs,based on the voxel-based Portunus haanii phantom,provided precise and reliable data for conducting internal radiation dose calculations specifically tailored to the Chinese Red Swimming Crab(Portunus haanii).The results indicated that the self-AFs and self-SAFs were affected by both the radiation energy and the mass of the source/target organ.Moreover,the AFs and SAFs for cross irradiation,were not only dependent on the energy and the mass of the target organ,but also on the relative position of the source and target organs.Conclusion:These results serve as a valuable resource for accurately evaluating the internal radiation exposure of this species.

Characterization of dissolved organic matter fractions from Lake Hongfeng, Southwestern China Plateau

With XAD-series and ion exchange resins, dissolved organic matter （DOM） from Lake Hongfeng in Southwestern China Plateau was isolated into 6 fractions, i.e., humic acid （HA）, fulvic acid （FA）, hydrophobic neutrals （HON）, hydrophilic acids （HIA）, hydrophilic bases （HIB） and hydrophilic neutrals （HIN）. Those fractions were characterized by high performance size exclusion chromatography, fluorescence spectroscopy and UV absorbance. Among the 6 fractions, FA was predominant and accounted for 51% of the total DOM. The weight-average （Mw） and number-averaged （Mn） molecular weight of these fractions ranged from 1688 to 2355 Da and from 1338 to 1928 Da, respectively. A strong correlation was observed between specific UV absorbance at 280 nm, E2/E3 （absorbance at 250 nm to 365 nm）, and the molecular weight for DOM fractions. UV-Vis fulvic-like fluorescence peaks were found in all fractions. Proteinlike fluorescence peaks existed in HON may indicate that microbial activity was severely in Lake Hongfeng. There was a significant relationship between fluorescence intensities and specific UV absorbance at 254 nm for those DOM fractions, suggesting their similar luminescence characteristics. The values of fluorescence index （f450/500） indicated that hydrophobic fractions may derive from terrestrial sources, and the hydrophilic fractions from microbial and terrestrial origins. Those results suggest that there were inter-relationships between molecular weight, fluorescence and absorbance characteristics, and also subtle consistencies between the hydrophilic and hydrophobic properties and the sources for these 6 fractions from Lake Hongfeng.

Purification and Structural Analysis of a Selective Toxin Fraction Produced by the Plant Pathogen Setosphaeria turcica

Thirteen fractions from the pathogenic plant fungus Setosphaeria turcica race 1 were separated and collected using high performance liquid chromatography （HPLC）. Their toxic activities were assayed through leaf puncturing on corn differentials （OH43, OH43Ht1, OH43Ht2, and OH43HtN）, and the results revealed that eight fractions were toxic and fraction 6 was specifically toxic to OH43Ht1, which could be taken as a gene-selective toxin fraction. Fraction 6 was finely purified via HPLC and condensed by freeze desiccation. Its chemical structure was analyzed with EI-MS, IR, HMBC, ^1H-NMR, and two-dimensional NMR. The results suggested that fraction 6 contained an unsaturated double bond, carbonyl and methylene groups with molecular weight of 142.

Designing a green and efficient absorbent for CO_2 capture

Several task-specific ionic liquids（TSILs） with weak alkalinity have been designed based on tetraalkyl-ammonium cation and L-alanine anion([N2222][L-Ala]) for the CO2 absorption.[N2222][L-Ala]has been chosen as a green and efficient activator for methyldiethanolamine（MDEA）.The densities,viscosities and absorption properties of the equimolar[N2222][L-Ala]-MDEA blended absorbents were investigated.Low viscosity and density values support the idea that blended absorbents are preferred in the industrial applications.[N2222][L-Ala]-MDEA behave similarly to the aqueous counterparts but offer more advantages,such as large absorption capacities,fast absorption rate and relatively low damage to the environment.

复合溶剂液化制备乙酰丙酸乙酯的碳同位素分馏

利用单体稳定同位素分析(CSIA)技术研究C3、C4植物源原料液化生成乙酰丙酸乙酯(EL)过程中碳稳定同位素分馏特征。实验结果表明,在反应时间15 min内,C3、C4植物源原料液化生成EL的反应速率为木薯淀粉>玉米淀粉,杨木纤维素(P-C)>玉米秸秆纤维素(CS-C),杨木>玉米秸秆,液化生成EL过程中碳同位素比值的分馏速率为C3植物源原料>C4植物源原料,两者之间存在着直接的线性关系,液化反应速率较大时,δ^(13)C值的变化速率也大。结合瑞利方程量化液化过程中EL的^(13)C碳稳定同位素的富集程度,得到不同原料液化过程中富集因子大小为ε>ε,ε_(CS-C)>ε_(P-C),ε>ε,表明液化过程中碳同位素的富集程度与原料的δ^(13)C值相关,液化程度越大,δ^(13)C值变化程度越大,通过追踪反应过程中的碳稳定同位素分馏变化就可以反映其液化程度。此外,^(13)C同位素富集在中间产物5-羟甲基糠醛(5-HMF)上,而在最终产物EL中相对较少;由于动力学同位素效应的存在,发生化学反应后,^(12)C同位素在EL中逐渐富集,^(13)C同位素富集在5-HMF中,说明在试验过程中5-HMF→EL的路径占优势。由此可知,CSIA可用于C3、C4植物源原料液化过程的研究。

CCTA-AI联合FFR-CT诊断冠状动脉狭窄病变的应用价值研究

目的评估计算机断层扫描血管成像(CCTA)与人工智能(AI)联合心肌灌注分数(FFR-CT)对冠状动脉狭窄病变的诊断价值。方法选择于2022年1月至2023年2月到南阳市中心医院接受诊治的80例疑似冠状动脉狭窄病变患者作为观察对象。所有患者均接受CCTA以及冠状动脉造影(CAG)检查,其检查的间隔时间应在14天内,然后通过AI软件自动对CCTA的图像进行重建和计算,同时计算FFR-CT的数值。计算人工智能辅助的心脏计算机断层扫描(CCTA-AI)联合FFR-CT诊断的敏感度、特异度、准确度、阳性预测值和阴性预测值。结果80例患者经CAG检查确诊,72例患者为冠状动脉狭窄病变,占比为90%;8例患者为非冠状动脉狭窄病变,占比为10%。CCTA-AI联合FFR-CT检查的敏感度、特异度、阳性预测值、阴性预测值、准确度以及AUC值均高于CCTA-AI、FFR-CT单独检查,差异有统计学意义(P<0.05)。结论采用CCTA-AI联合FFR-CT检查诊断冠状动脉狭窄病变具有较高的诊断效能,其敏感度及特异度均得到显著提高。

事故吸入^(241)Am后RBE加权吸收剂量系数计算

当已经发生或即将发生放射性核素急性大量摄入时,对于确定效应(或组织反应)剂量范围,需要一个能够快速估计敏感靶器官或组织在短时间内吸收辐射能量的技术手段或工具,从而能够基于国际原子能机构(IAEA)安全导则GSG-2进行核与辐射应急响应和其他响应行动决策,尽可能地减少受照射人员的急性大剂量照射、保护人员的生命健康。本文在系统研究国际放射防护委员会(ICRP)呼吸道模型、系统模型、消化道模型设计原理和参数建立依据基础上,编写^(241)Am为代表的超铀核素吸入后的滞留排泄份额m(t)计算程序,计算事故吸入^(241)Am后敏感靶器官的短期相对生物效应(RBE)加权吸收剂量AD(30)_(T)系数,并经验证确保计算结果正确。

基于不同模糊度固定产品的PPP-AR定位性能评估

基于CODE、GFZ、CNES、武汉大学PRIDE实验室和内部估计的模糊度固定产品,从收敛时间、首次固定时间及定位精度等方面进行PPP-AR固定性能的研究。实验选用2022年40个IGS测站7 d的观测数据和各模糊度固定产品配套使用的精密产品,结果表明,在置信度为95%的静态解算模式下,5种产品在解算时间为1 h时固定解较浮点解定位精度提升最明显,分别提升46.58%(3.4 cm)、41.10%(3.0 cm)、45.21%(3.3 cm)、34.25%(2.5 cm)和41.10%(3.0 cm)。仿动态解算模式下,5种产品E、N方向的定位精度都能达到mm级,U方向较浮点解精度提升较小,其中使用GBM产品的精度提升最小,E、N、U方向分别提高72.73%(2.4 cm)、47.37%(0.9 cm)、5.41%(0.2 cm);提升效果较好的是WUM和COM产品,分别为81.82%(2.7 cm)、63.16%(1.2 cm)、24.32%(1.1 cm)和81.82%(2.7 cm)、63.16%(1.2 cm)、15.58%(0.8 cm)。

基于超声分层应变成像技术评价苓桂气化方改善射血分数保留心力衰竭早期大鼠心肌功能的研究

目的基于超声分层应变成像技术评价苓桂气化方改善射血分数保留心力衰竭(heart failure with preserved ejection fraction,HFpEF)早期大鼠心肌功能。方法40只SPF级SHR大鼠随机分为HFpEF模型组、恩格列净组、苓桂气化方低剂量组和苓桂气化方高剂量组,10只WKY大鼠为空白组。采用高盐高脂高糖饮食及腹腔注射链脲佐菌素建立HFpEF早期大鼠模型,各组予相应干预9周后测量左室舒张末期内径、左室舒张末期后壁厚度、舒张早期血液速度/舒张早期二尖瓣环间隔侧组织多普勒频谱、左室射血分数以及左室心内膜下心肌整体纵向应变、中层心肌整体纵向应变、心外膜下心肌整体纵向应变、心内膜下心肌整体圆周应变、中层心肌整体圆周应变和心外膜下心肌整体圆周应变。酶联免疫吸附法测定血清B型脑尿钠肽。马松染色观察心肌组织病理变化。结果与模型组比较,恩格列净组心内膜下心肌整体纵向应变、中层心肌整体纵向应变和心内膜下心肌整体圆周应变明显升高(P<0.05),苓桂气化方低剂量组心内膜下心肌整体纵向应变和中层心肌整体纵向应变明显改善(P<0.05),苓桂气化方高剂量组心内膜下心肌整体纵向应变、中层心肌整体纵向应变和中层心肌整体圆周应变明显提升(P<0.05)。苓桂气化方低剂量组和苓桂气化方高剂量组心肌细胞间隙变窄,胶原纤维沉积减少。结论苓桂气化方能提高HFpEF早期模型大鼠心内膜下心肌整体纵向应变、中层心肌整体纵向应变、中层心肌整体圆周应变,改善左室重构和收缩功能。超声分层应变成像技术可以无创、定量、敏感检测HFpEF早期大鼠左室壁心肌改变。

The relationship between organic matter and specific surface area in <2 μm clay size fraction of muddy source rock

The adsorption of organic matter(OM)onto clay minerals has long been considered as a significant way of OM preservation in source rock.Here we analyzed the relationship between OM and the specific surface area(SSA)of <2μm clay size fraction isolated from 13 source rock cores collected from Dongying depression.Rock-Eval pyrolysis and N2 adsorption experiment were employed to probe the characteristics of OM and SSA(denoted SBET)in samples before and after OM extraction using trichloromethane.The results indicate that various kinds of OM occurrence coexist in clay size fraction and their contributions to hydrocarbon are different in each period of OM evolution.The occurrence and amount of OM affect the S BET of clay size fraction,and a nonlinear negative correlation between total organic carbon(TOC)and S BET can be recognized.The soluble OM(chloroform extract "A"),mainly stored in the pore space of clay size fraction,shows a negative correlation in amount with S BET.Our data also indicate that free hydrocarbon(S1)was stored mainly in the pore space and/or the surface of clay size fraction,whereas pyrolysis hydrocarbon(S2)was mingled mainly with clay minerals.Therefore,to understand various OM occurrences and their relationship with SBET in the clay size fraction is significant in the study of generation,accumulation,and migration of hydrocarbon in muddy source rock.

城市群花粉过敏网络关注度及影响因素研究

研究花粉过敏网络关注度时空特征及影响因素有利于掌握相关信息,服务民生。本文结合百度指数、气象、遥感数据,分析8个城市群2017—2021年花粉过敏网络关注度时空特征与影响因素,并采用随机森林、反向传播神经网络模型进行模拟。结果表明:(1)时空特征:关注度每年高峰期在春季(4—5月);人口聚集的城市最高,在空间上聚集,京津冀、山东半岛、长三角、珠三角城市群为热点区。(2)与影响因素关系:有效范围内,温度升高、短时雷暴雨、空气质量差、光合有效辐射吸收分量升高、夜间灯光强,关注度高;高湿、高风速、大雨、久雨,关注度低;夜间灯光相关性最高。(3)城市群方面:北方城市群的温度、沿海城市群的湿度、地形起伏大城市群的风速、南方城市群的降水、珠三角和长三角城市群的空气质量指数、珠三角和京津冀城市群的光合有效辐射吸收分量重要性大,夜间灯光都不可替代。(4)随机森林和反向传播神经网络适用于模拟关注度,各城市群R^(2)均在0.64~0.92之间,RMSE、MAE均在1以下,反向传播神经网络比随机森林模拟效果更好。成渝城市群2个模型拟合度均优,其次是京津冀、珠三角和长江中游城市群。本文的方法和结果可为花粉过敏相关工作提供参考。

Remote estimation of the fraction of absorbed photosynthetically active radiation for a maize canopy in Northeast China

Aims accurate remote estimation of the fraction of absorbed photosynthetically active radiation(fAPAR)is essential for the light use efficiency(LUE)models.Currently,one challenge for the LUE models is lack of knowledge about the relationship between fAPAR and the normalized difference vegetation index(NDVI).Few studies have tested this relationship against field measurements and evaluated the accuracy of the remote estimation method.this study aimed to reveal the empirical relationship between NDVI and fAPAR and to improve algorithms for remote estimation of fAPAR.Methods to investigate the method of remote estimation of fAPAR seasonal dynamics,the CASA(Carnegie-ames-stanford approach)model and spectral vegetation indices(VIs)were used for in situ measure-ments of spectral reflectance and fAPAR during the growing season of a maize canopy in Northeast China.Important Findingsthe results showed that the fAPAR increased rapidly with the day of year during the vegetative stage,it remained relatively stable at the stage of reproduction,and finally decreased slowly during the senescence stage.In addition,fAPAR green[fAPAR_(green)=fAPAR_(green) -fAPAR_(green) LAI_(max))]showed clearer seasonal trends than fAPAR.the NDVI,red-edge NDVI,wide dynamic range vegetation index,red-edge position(REP)and REP with sentinel-2 bands derived from hyperspectral remote sensing data were all significantly positively related to fAPAR green during the entire growing season.In a comparison of the predictive performance of VIs for the whole growing season,REP was the most appropriate spectral index,and can be recommended for monitoring seasonal dynamics of fAPAR in a maize canopy.

铝合金蜂窝吸能结构参数优化设计

基于铝合金蜂窝结构轴向平压试验和数值模拟,对不同结构参数的铝合金蜂窝结构吸能特性展开评估,通过对参数质量比吸能增率的引入,表明吸能增率与质量增率为一次线性关系。归纳得出铝合金蜂窝吸能结构参数优化设计的经验公式,经验证明,计算精度超过90%,可实现铝蜂窝吸能结构参数快速优化设计,为轻量化吸能结构的设计提供理论依据。

超声波对高硅氧玻璃纤维酸处理影响探讨

主要开展了超声波技术在高硅氧玻璃纤维酸处理中的应用研究,通过设计不同的超声强度和超声时间,研究其对酸沥滤、水洗过程中纤维的硅质量分数及比表面积的影响。同时,分析超声波功率和超声时间对高硅氧玻璃纤维酸沥滤进程和水洗效率的影响,评估超声波在酸处理工艺中的应用潜力,结果表明超声处理可以提高高硅氧玻璃纤维酸沥滤和水洗的效率,纤维中SiO_(2)质量分数可达97%以上,为提高产品的品质和生产效率提供参考依据。

基于中国参考人人体数学模型的内照射剂量计算

根据中国人体特征开发的中国参考人人体数学模型,采用Monte Carlo方法模拟γ光子在人体模型内的粒子输运过程,计算得出反映国人特征的各源器官对靶器官的比吸收分数(Φ),建立了我国自己的Φ数据库。并将此结果与美国橡树岭模型(ORNL)推荐值进行了比较,源靶器官相同(自吸收)时结果十分吻合,证明了方法的正确性;源靶器官不同时,由于人体模型的差别和物理过程选择的差别,数据存在一定差异。

围压条件下岩石循环冲击损伤的能量特性研究

在不同围压等级和冲击荷载循环作用下,利用带围压装置的霍普金森压杆设备,对斜长角闪岩、绢云母石英片岩和砂岩的动态力学性能进行试验研究,得到不同循环作用次数下岩样的应力–应变曲线。通过理论分析建立岩石损伤度的判定标准,并定义累积比能量吸收参量来表征围压条件下岩样冲击损伤的能量特性。3种岩石损伤度与围压和累积比能量吸收值的关系研究表明:累积比能量吸收参量能很好的描述围压条件下岩样的冲击损伤程度,岩石循环冲击损伤演化过程存在围压效应,当围压逐渐增大时,岩石损伤度的增加随累积比能量吸收值增加的趋势变缓,其抗冲击损伤的能力增强,即围压越高,试件达到相同损伤度所需要耗散的能量越多。得出围压条件下岩石损伤度与累积比能量吸收值的关系式。随着围压的增加,砂岩达到损伤阈值时的累积比能量吸收值增长率最大,斜长角闪岩次之,绢云母石英片岩最小。

基于单体多维稳定同位素分析的地下水有机污染研究进展

单体多维稳定同位素分析技术(MD-CSIA)能够更加深入地解析地下水有机污染物的衰减过程,为监测目标污染物原位修复效果和探究其微生物降解机制提供技术支持。文中分析了MD-CSIA技术在地下水有机污染研究中的应用动态,讨论了利用该技术进行有机污染物来源辨识及其迁移转化过程示踪的可行性,着重指出该技术可有效判识有机污染物在地下水中的转化途径并量化其转化程度,最后预测了MD-CSIA技术应用研究的发展趋势。

Carbon-Epoxy圆管件的静态吸能特征

Carbon/Epoxy 复合材料可以用作理想的吸能材料。为了考察材料体系对结构吸能性能的影响,对一系列Carbon/Epoxy圆管件进行了静态吸能性能试验。试验结果表明,在基体种类相同的条件下,结构的压溃失效模式有很大的区别。材料的吸能性能不仅同材料性能关系密切,而且也受材料纤维方式影响。

数字图像估测棉花光合有效辐射吸收比例

研究利用数字图像技术估测棉花光合有效辐射吸收比例的方法,以期为棉花生长状况的动态监测提供依据。2013-2014年设置不同株行距配置试验,在棉花关键生育时期通过数码相机、线性光量子传感器分别测定棉花覆盖度和光合有效辐射吸收比例。结果表明,不同配置方式下,fCover和fAPAR的季节变化规律基本一致,生育后期由于非绿色器官的增多致使低估fCover;fCover与fIPAR和fAPAR呈线性的极显著正相关,与LAI和干物质呈指数的极显著正相关;综合分析2a数据,建立图像覆盖度估测fAPAR的模型(R2=0.895,SE=0.076);根据独立试验数据对估测模型进行检验的结果显示,模型的决定系数(R2=0.964)较高且预测误差(RMSE=0.058)较小。因此,图像覆盖度是一种简便、快捷、有效地估测棉花光合有效辐射吸收比例的方法。