Changes in air pollutants during the COVID-19 lockdown in Beijing:Insights from a machine-learning technique and implications for future control policy

基于2015-2020年北京35个环境空气站和20个气象站观测资料,应用机器学习方法(随机森林算法)分离了气象条件和源排放对大气污染物浓度的影响.结果发现,为应对疫情采取的隔离措施使北京2020年春节期间大气污染物浓度降低了35.1％-51.8％;其中,背景站氮氧化物和一氧化碳浓度的降幅最大,超过了以往报道较多的交通站...     

华北汛期降水异常与100hPa高度场异常的关系

利用华北17站1951～2000年的逐月降水资料,与前期的100 hPa高度场(1958～1997年)求相关,找到了100 hPa高度场影响华北地区汛期降水的关键影响区为25°～35°N,85°～105°E,对应的关键影响时段为前一年3～5月.然后用SVD方法证实了前一年春季正是与华北汛期降水相关最显著的时段;而所选关键区正是处于一种范围更大的100 hPa高度场空间分布型的关键部位,而华北地区是关键区影响中国东部降水的最显著的区域之一.     

An East Asian Subtropical Summer Monsoon Index Defined by Moist Potential Vorticity

Based on consideration of both thermodynamic and kinetic features of the subtropical summer monsoon in East Asia,a new index is defined by the moist potential vorticity (MPV) for this monsoon.Variation features of the subtropical summer monsoon over 60 years are analyzed using National Centers for Environmental Prediction/National Center for Atmospheric Research (USA) data from 1948 to 2007.Results show that the new index can well reflect the seasonal,interannual,and interdecadal variations of the East Asian subtropical summer monsoon.Correlation analysis of the new index and precipitation data from 160 stations in China shows that in high-index years,the summer monsoon is strong,and more rain falls in eastern North China,southwestern China,and along the coast of South China and less rain falls in the Yangtze-Huaihe R.basin.In low-index years,the opposite occurs.Lastly,the new index is compared with four established monsoon indices.The new index is found to have an advantage in representing summer rainfall in the Yangtze-Huaihe R.basin.     

新疆北塔山地区埃姆斯期腕足动物群

区内早泥盆世沉积为卓木巴斯套组, 产丰富的古生物化石, 以极为丰富的腕足为主要特征。通过地质路线调查与剖面测量, 采集到大量的腕足、珊瑚、三叶虫、苔藓虫、角石、菊石等动物化石, 其中, 腕足类占90%以上。本次工作鉴定出腕足化石24属48种。根据动物化石组成及面貌将其定为 “东准Spinatrypa khalfini动物群”。主要特征是腕足在动物群中的含量占绝对比例, 而且石燕类、无洞贝类占绝对优势。依据化石组合类型及产出层位将其划分为下部Leptocoelia sinica组合及上部Spinatrypa khalfini组合。将北塔山地区与我国北部其他地区同时代地层中的腕足动物群进行对比发现:北塔山地区的腕足化石的产出层位与内蒙古地区东乌珠穆沁旗敖包亭浑迪组、东北地区金水组、霍龙门组、黑台组、乌努尔组大致相当;并根据个别属种在世界范围的时代意义, 确定了卓木巴斯套组的时代为埃姆斯期。     

隧道开挖对地下管线的影响分析

采用Abaqus有限元分析软件,建立三维模型,模拟隧道开挖对地下管线的影响,充分考虑了不同的埋深、材质、下卧层刚度等条件。结果表明,管线周围土的性状,与双线隧道的相对位置以及管线自身刚度、管径等不同,将对其变形和内力产生较大影响,从而得出一些规律,为今后类似工程施工提供依据。     

锚固体应力分布规律的数值模拟分析

采用非线性有限元法,分析了全长粘结式锚杆在荷载作用下剪应力的分布规律,同时研究了被加固岩土体的性质对锚固体剪应力分布规律的影响。并将数值模拟的结果与理论计算以及试验结果进行了对比分析。分析表明,锚固体剪应力的分布非常不均匀;当荷载不大时,锚杆所受的剪应力分布范围较小,而最大剪应力数值较大;随着荷载的加大,剪应力的分布范围有向下扩展的趋势,但扩展的速度比较慢;锚固体所受的剪应力的大小和分布与岩体性质有密切的关系,岩石越坚硬,剪应力分布越集中,最大剪应力的数值越大;而岩体越松软,剪应力分布就越均匀,最大剪应力的数值就越小。     

太湖和大浦河口风成流、风涌水的数值模拟及其单站验证

介绍了太湖风成流和风涌水的数值摸拟工作。使用两种不同水平分辨率的数值模式,利用中日合作研究组在大浦河口实测的水位、湖流和风的资料对模拟结果进行了验证。结果指出,模式对风涌水及流向有较好的预报能力,流速的预报尚待进一步改进。     

与高岭石固相平衡的酸性天然地表水中铝的缓冲作用的计算机模拟

基于质量守恒以及电中性条件,采用化学平衡计算法,计算模拟研究了高岭石固相平衡的酸性天然地表水中铝的缓冲作用对ｐＨ值,酸中和容量ＡＮＣ和缓冲强度β的影响,讨论了影响酸性地表水ｐＨ估算的各种因素,如溶解硅酸的浓度,溶解总无机碳的浓度,溶解总氟和总有机碳的浓度及温度等。模型被用于实际水样的分析,所得结果与实验值符合较好,用ＭｏｎｔｅＣａｒｌｏ模拟考察了由于平衡常数的选择以及水化学参数测量误差而带来的不确     

Separation of Vanillin and Syringaldehyde from Oxygen Delignification Spent Liquor by Macroporous Resin Adsorption

This paper reports on an approach for separating vanillin and syringaldehyde (VSA) from oxygen delignification spent liquor using non‐polar macroporous resin. The effects of temperature and pH on the adsorption isotherms were studied. The adsorption capacity and adsorption equilibrium constant were obtained using the Langmuir adsorption model at pH<4.5, where the ionization of the VSA to ionic forms was negligible. The standard enthalpy change was calculated using the van't Hoff equation and clearly showed that the adsorption is an exothermic process. The effect of pH on the adsorption isotherm is well‐described by a modified Langmuir model and shows that the adsorption equilibrium constant decreases significantly with the increasing pH. The VSA adsorbed on macroporous resin was eluted by ethyl ether. The separated VSA contained 37.51% vanillin, 31.88% syringaldehyde. The recoveries of VSA were 96.2 and 94.7%, respectively.     

Differential Thermal Regimes of the Tarim and Sichuan Basins in China: Implications for Hydrocarbon Generation and Conservation

The uncertainty surrounding the thermal regimes of the ultra-deep strata in the Tarim and Sichuan basins, China, is unfavorable for further hydrocarbon exploration. This study summarizes and contrasts the present-day and paleo heat flow, geothermal gradient and deep formation temperatures of the Tarim and Sichuan basins. The average heat flow of the Tarim and Sichuan basins are 42.5 ± 7.6 mW/m2 and 53.8 ± 7.6 mW/m2, respectively, reflecting the characteristics of ‘cold’ and ‘warm’ basins. The geothermal gradient with unified depths of 0–5,000 m, 0–6,000 m and 0–7,000 m in the Tarim Basin are 21.6 ± 2.9 °C/km, 20.5 ± 2.8 °C/km and 19.6 ± 2.8 °C/km, respectively, while the geothermal gradient with unified depths of 0–5,000 m, 0–6,000m and 0–7,000 m in the Sichuan Basin are 21.9 ± 2.3 °C/km, 22.1 ± 2.5 °C/km and 23.3 ± 2.4 °C/km, respectively. The differential change of the geothermal gradient between the Tarim and Sichuan basins with depth probably results from the rock thermal conductivity and heat production rate. The formation temperatures at depths of 6,000 m, 7,000 m, 8,000 m, 9,000 m and 10,000 m in the Tarim Basin are 80°C–190°C, 90°C–220°C, 100°C–230°C, 110°C–240°C and 120°C–250°C, respectively, while the formation temperatures at depths of 6,000 m, 7,000 m, 8,000 m and 9,000 m in the Sichuan Basin are 120°C–200°C, 140°C–210°C, 160°C–260°C and 180°C–280°C, respectively. The horizontal distribution pattern of the ultra-deep formation temperatures in the Tarim and Sichuan basins is mainly affected by the basement relief, fault activity and hydrothermal upwelling. The thermal modeling revealed that the paleo-heat flow in the interior of the Tarim Basin decreased since the early Cambrian with an early Permian abrupt peak, while that in the Sichuan Basin experienced three stages of steady state from Cambrian to early Permian, rapidly rising at the end of the early Permian and declining since the late Permian. The thermal regime of the Sichuan Basin was always higher than that of the Tarim Basin, which results in differential oil and gas generation and conservation in the ultra-deep ancient strata. This study not only promotes theoretical development in the exploration of ultra-deep geothermal fields, but also plays an important role in determining the maturation phase of the ultra-deep source rocks and the occurrence state of hydrocarbons in the Tarim and Sichuan basins.