Iceland Plume and its Magmatic Manifestations:LIP-Dornr?schen in the North Atlantic

Plume-lithosphere interactions are key in the coupling of deep Earth and surface processes,impacting deformation and evolution of sedimentary basins and continental topography at different spatial scales(Cloetingh et al.,2022,2023).The North Atlantic region is a prime example of the interaction between plate tectonic movements and thermal instabilities in the Earth's mantle.The opening of the Labrador Sea/Baffin Bay and the North Atlantic,the widespread volcanism and the localized uplift of the topography in Greenland and the North Atlantic are traditionally attributed to the thermal effect of the Iceland mantle plume.

Experimental investigation of the inhibition of deep-sea mining sediment plumes by polyaluminum chloride

Deep-sea sediment disturbance may occur when collecting polymetallic nodules,resulting in the creation of plumes that could have a negative impact on the ecological environment.This study aims to investigate the potential solution of using polyaluminum chloride(PAC)in the water jet.The effects of PAC are examined through a self-designed simulation system for deep-sea polymetallic nodule collection and sediment samples from a potential deep-sea mining area.The experimental results showed that the optimal PAC dose was found to be 0.75 g/L.Compared with the test conditions without the addition of PAC,the presence of PAC leads to a reduction in volume,lower characteristic turbidity,smaller diffusion velocity,and shorter settling time of the plume.This indicates that PAC inhibits the entire development process of the plume.The addition of PAC leads to the flocculation of mm-sized particles,resulting in the formation of cm-sized flocs.The flocculation of particles decreases the rate of erosion on the seabed by around 30%.This reduction in erosion helps to decrease the formation of plumes.Additionally,when the size of suspended particles increases,it reduces the scale at which they diffuse.Furthermore,the settling velocity of flocs(around 10^(-2) m/s)is much higher that of compared to sediment particles(around 10^(-5) m/s),which effectively reduces the amount of time the plume remains in suspension.

U-Net Inspired Deep Neural Network-Based Smoke Plume Detection in Satellite Images

Industrial activities, through the human-induced release of Green House Gas (GHG) emissions, have beenidentified as the primary cause of global warming. Accurate and quantitative monitoring of these emissions isessential for a comprehensive understanding of their impact on the Earth’s climate and for effectively enforcingemission regulations at a large scale. This work examines the feasibility of detecting and quantifying industrialsmoke plumes using freely accessible geo-satellite imagery. The existing systemhas so many lagging factors such aslimitations in accuracy, robustness, and efficiency and these factors hinder the effectiveness in supporting timelyresponse to industrial fires. In this work, the utilization of grayscale images is done instead of traditional colorimages for smoke plume detection. The dataset was trained through a ResNet-50 model for classification and aU-Net model for segmentation. The dataset consists of images gathered by European Space Agency’s Sentinel-2 satellite constellation from a selection of industrial sites. The acquired images predominantly capture scenesof industrial locations, some of which exhibit active smoke plume emissions. The performance of the abovementionedtechniques and models is represented by their accuracy and IOU (Intersection-over-Union) metric.The images are first trained on the basic RGB images where their respective classification using the ResNet-50model results in an accuracy of 94.4% and segmentation using the U-Net Model with an IOU metric of 0.5 andaccuracy of 94% which leads to the detection of exact patches where the smoke plume has occurred. This work hastrained the classification model on grayscale images achieving a good increase in accuracy of 96.4%.

Plume-lithosphere interaction in the Comei Large Igneous Province: Evidence from two types of mafic dykes in Gyangze, south Tibet, China

Two suites of mafic dykes,T1193-A and T1194-A,outcrop in Gyangze area,southeast Tibet.They are in the area of Comei LIP and have indistinguishable field occurrences with two other dykes in Gyangze,T0902 dyke with 137.7±1.3 Ma zircon age and T0907 dyke with 142±1.4 Ma zircon age reported by Wang YY et al.(2016),indicating coeval formation time.Taking all the four diabase dykes into consideration,two different types,OIB-type and weak enriched-type,can be summarized.The“OIB-type”samples,including T1193-A and T0907 dykes,show OIB-like geochemical features and have initial Sr-Nd isotopic values similar with most mafic products in Comei Large Igneous Provinces(LIP),suggesting that they represent melts directly generated from the Kerguelen mantle plume.The“weak enriched-type”samples,including T1194-A and T0902 dykes,have REEs and trace element patterns showing withinplate affinity but have obvious Nb-Ta-Ti negative anomalies.They show uniform lowerεNd(t)values(−6‒−2)and higher 87Sr/86Sr(t)values(0.706‒0.709)independent of their MgO variation,indicating one enriched mantle source.Considering their closely spatial and temporal relationship with the widespread Comei LIP magmatic products in Tethyan Himalaya,these“weak enriched-type”samples are consistent with mixing of melts from mantle plume and the above ancient Tethyan Himalaya subcontinental lithospheric mantle(SCLM)in different proportions.These weak enriched mafic rocks in Comei LIP form one special rock group and most likely suggest large scale hot mantle plume-continental lithosphere interaction.This process may lead to strong modification of the Tethyan Himalaya lithosphere in the Early Cretaceous.

Automatic segmentation of gas plumes from multibeam water column images using a U-shape network

Cold seeps are widely developed on the seabed of continental margins and can form gas plumes due to the upward migration of methane-rich fluids.The detection and automatic segmentation of gas plumes are of great significance in locating and studying the cold seep system that is usually accompanied by hydrate layers in the subsurface.A multibeam echo-sounder system(MBES)can record the complete backscatter intensity of the water column,and it is one of the most effective means for detecting cold seeps.However,the gas plumes recorded in multibeam water column images(WCI)are usually blurred due to the interference of the complicated water environment and the sidelobes of the MBES,making it difficult to obtain the effective segmentation.Therefore,based on the existing UNet semantic segmentation network,this paper proposes an AP-UNet network combining the convolutional block attention module and the pyramid pooling module for the automatic segmentation and extraction of gas plumes.Comparative experiments are conducted among three traditional segmentation methods and two deep learning methods.The results show that the AP-UNet segmentation model can effectively suppress complicated water column noise interference.The segmentation precision,the Dice coefficient,and the recall rate of this model are 92.09%,92.00%,and 92.49%,respectively,which are 1.17%,2.10%,and 2.07%higher than the results of the UNet.

Vestiges of the Kerguelen Mantle Plume in Southern Tibet:Evidence from 123-117 Ma Magmatism in the Dingri Area of the Central Tethys Himalaya

The widely distributed Early Cretaceous magmatism in the Tethys Himalaya(TH)of southern Tibet is related to the Kerguelen mantle plume.Associated magmatic activity products are distributed in the eastern TH,where the active age is earlier than the peak ages of the Kerguelen mantle plume.This study investigated magmatic activity of the Dingri area in the central TH which was coeval with the Kerguelen mantle plume.The intrusion in the Dingri area contains diabases and monzonites.The zircon age of diabase is 123±1 Ma,and that of monzonite is 117±1 Ma.Geochemistry and Sr-Nd isotopic analyses show that the mafic-intermediate dikes were formed in an intraplate extensional environment.The diabase is derived from the enriched lithospheric mantle and monzonite is derived from partial melting of the lower crust,with both magmatic evolutions being contaminated by crustal materials.These characteristics are similar to those of the Rajmahal-Sylhet basalt,a typical Kerguelen mantle plume product.The discovery of the Dingri mafic-intermediate dikes of the central TH suggests that the TH and Rajmahal-Sylhet Traps formed a continuous mantle plume overflow magmatic belt which was a product of the continuous eruption of the Kerguelen mantle plume.

Quaternary Intrusions from the Zhongjiannan Basin,South China Sea:Their Relationship with the Hainan Mantle Plume and Influence on Hydrocarbon Reservoirs

The transportation of magma in sedimentary basins often occurs through extensive dyke-sill networks.The role of sills on the plumbing system in rifted margins and the impact of sills on hydrocarbon reservoirs of prospective sedimentary basins has long been an area of great industrial interest and scientific debate.Based on 2D seismic reflection,we present data on how the sills emplaced to form a magmatic plumbing system of the volcanic system for the Zhongjiannan Basin(ZJNB).The results show that sixty-nine sills and fourteen forced folds have been identified.The distribution and geometry of the sills suggest that magma flowed from west to east and then ascended to near the surface.The onlap relationship of the forced folds indicates that the timing of magmatic activities can be constrained at ca.0.2 Ma.The spatial and temporal occurrences of intrusions imply that the strong post-rift magmatism in ZJNB was associated with the Hainan mantle plume arising from the core-mantle boundary.Furthermore,these forced folds could produce several types of hydrocarbon traps,due to accommodation through bending and uplift of the overlying rock and free surface,but it is critical to evaluate the effect of such emplacement when setting exploration targets.

Quantitative estimation of bubble volume fraction of submarine seep plumes by modeling seismic oceanography data

Submarine seep plumes are a natural phenomenon in which different types of gases migrate through deep or shallow subsurface sediments and leak into seawater in pressure gradient.When detected using acoustic data,the leaked gases frequently exhibit a flame-like structure.We numerically modelled the relationship between the seismic response characteristic and bubble volume fraction to establish the bubble volume fraction in the submarine seep plume.Results show that our models are able to invert and predict the bubble volume fraction from field seismic oceanography data,by which synthetic seismic sections in different dominant frequencies could be numerically simulated,seismic attribute sections(e.g.,instantaneous amplitude,instantaneous frequency,and instantaneous phase)extracted,and the correlation between the seismic attributes and bubble volume fraction be quantitatively determined with functional equations.The instantaneous amplitude is positively correlated with bubble volume fraction,while the instantaneous frequency and bubble volume fraction are negatively correlated.In addition,information entropy is introduced as a proxy to quantify the relationship between the instantaneous phase and bubble volume fraction.As the bubble volume fraction increases,the information entropy of the instantaneous phase increases rapidly at the beginning,followed by a slight upward trend,and finally stabilizes.Therefore,under optimal noise conditions,the bubble volume fraction of submarine seep plumes can be inverted and predicted based on seismic response characteristics in terms of seismic attributes.

热羽流与置换通风作用下油雾颗粒预测模型

高大空间机械厂房采用置换通风系统时,存在竖直方向油雾颗粒浓度分布不均匀的现象。这种现象会影响以降低室内颗粒浓度为目的的需求通风量。为了快速预测竖向油雾颗粒浓度分布,采用区域模型建模方法,考虑壁面流区、热羽流区和主流区等主要区域,基于质量平衡与能量平衡方程,建立了竖向油雾颗粒浓度分布预测模型;同时在实验舱内进行了实验验证,模型计算结果与实验结果趋势相符,最大相对误差不大于20%,表明该模型能够基本满足工程要求;以5种颗粒散发率工况为例进行节能分析,发现引入预测模型后计算得到的置换通风系统需求通风量可比传统变风量系统通风设计方法计算的减少18.83%~44.41%。该预测模型能较为准确地预测高大厂房中置换通风时竖向不同高度的油雾颗粒浓度,可应用于需要快速预测竖向颗粒平均浓度的场景。

真空羽流中相变过程DSMC仿真方法研究

真空燃气羽流快速膨胀过程中,其中的H_(2)O和CO_(2)等组元容易发生凝结相变现象.为了研究真空羽流中水蒸气的相变产物冰晶对羽流红外信号、侵蚀等污染效应的影响,开展羽流中相变过程的数值模拟方法研究.基于稀薄两相羽流双向耦合DSMC方法,采用经典成核理论和液滴生长理论,建立了真空羽流的相变过程的数值仿真方法.对水蒸气在拉法尔喷管中自凝结试验的仿真.通过与试验结果的对比,对经典成核理论进行了修正,对成核率给出了10^(3)的修正因子,可以得到与试验符合的仿真结果,表明对成核理论修正后,可以应用到稀薄流动的数值模拟中.对某发动机真空羽流相变流场的仿真,在核心区得到与CFD相近的结果.仿真结果表明,在羽流流场中,由于相变,存在较多的冰晶颗粒,在计算条件下,羽流核心区冰晶数密度最大达到10^(15) m^(-3)的量级,冰晶直径在约10^(-8) m的量级.在真空环境下,随着羽流向倒流区无限制膨胀,倒流区流场内也会出现一定数量的冰晶颗粒,数密度从10^(7)~10^(10)m^(-3)的量级,直径在5.0×10^(-10)m的量级.颗粒在空间的数密度、尺寸等分布与气相分布存在差异,需要开展相关污染效应的影响研究.

助推段火箭发动机喷焰红外辐射特性数值计算

助推段火箭发动机尾喷焰具有显著的红外辐射特性,成为天基红外预警系统重点关注的对象。以三组元固体发动机为研究对象,建立连续流域和过渡流域的尾喷焰反应流场计算模型,采用两级助推段质心弹道法确定飞行弹道,通过反向寻优法完备发动机型谱参数,基于等效单喷管法简化流场计算,基于窄谱带法和视在光线法计算尾喷焰的红外辐射特性。研究结果表明:复燃效应使得尾喷焰红外辐射光谱强度升高约20倍,谱带积分强度升高约10倍;尾喷焰红外光谱存在2.7μm和4.3μm的特征峰值;低空流域的光谱强度较高,且不同谱带内积分强度随高度的升高呈现出波动规律和暗区现象;助推段尾喷焰辐射强度差值高达3个量级,尤其在4.3μm较为明显。所得成果可为火箭在助推段的探测和识别提供一定的理论参考。

基于遗传-模式搜索算法的微尺度管控区域大气污染物PM2.5溯源

针对微尺度管控区域可能发生的大气污染提出有效的靶向诊断方法-结合高斯烟羽模型和遗传-模式搜索算法的大气污染物分布式溯源方法.将污染源反算模型得到的污染物理论质量浓度与传感器网络观测值的数据对应关系作为目标函数,使用模式搜索算法嵌入遗传算法加快反算模型的搜索过程,反算得到污染源强度和位置.依托杭州市亚运板球场馆大气感知器网络进行实验验证,监测2021年10月PM2.5质量浓度、气象数据,对所提出的混合式大气污染溯源方法进行实验验证.实验结果表明:改进遗传-模式搜索算法对于多维变量的搜索效果较好,能快速精准地反算污染源的位置和强度,可以为微尺度管控区域突发性气体污染防治提供应急决策参考.

平板触头小开距高电流密度下真空电弧特性的实验研究

平板触头被广泛应用于真空触发开关和真空有载分接开关中,为研究其在高电流密度下的真空电弧特性及阳极模式的转变,该文针对直径15、20mm的平板触头,在3、6mm开距下进行触发燃弧实验,并依次对电弧电压特性、电弧能量特性、电弧形貌、触头烧蚀情况进行分析研究。结果表明:峰值电流一定时,随着触头直径与开距的比值的增大,电弧电压和电弧能量减小。触头直径与开距的比值越小,电弧出现阳极模式的阈值电流越小,且触头烧蚀越严重。在开距6mm时,直径15mm触头电弧电压在大部分时间比较稳定,阳极羽流在电弧快熄灭之前出现,而直径20mm触头电弧电压在整个燃弧期间频繁波动,电弧模式不断变化,阳极羽流在整个燃弧期间都有出现。研究结果对于大电流真空开断具有理论指导意义。

基于MTBF的电推进羽流诊断系统可靠性预计与试验

电推进羽流诊断系统(Electric Propulsion Plume Diagnostic System,EPPDS)是由探针组件、移动平台和电控单元组成的用于空间电推进羽流特征参数诊断的自研设备,产品规定的可靠性指标要求平均故障间隔时间(Mean Time Between Failures,MTBF)检验上限θ0≥5000 h。按照系统串并联模型及寿命指数分布模型的MTBF可靠性预计理论,给出了EPPDS的MTBF预计流程,进行了EPPDS各模块MTBF预计,系统MTBF预计值为1.059×10^(4) h。按照GJB 889短时高风险定时方案完成3台EPPDS 1833 h的可靠性验证试验,试验结果表明电控单元输出的法拉第探针、朗缪尔探针和阻滞势分析仪的偏置电压和扫描电压参数均满足合格判据。该方法可用于电子机械产品的MTBF预计和验证。

两次森林火灾的双偏振雷达探测特征分析

通过对2020年3月17日山东烟台、4月23日山东青岛发生的两次森林火灾的双偏振雷达探测资料进行分析,结果表明:(1)森林火灾燃烧产生的灰烬上升到空中,随环境风向下风方飘散,形成烟羽,烟羽的雷达反射率因子在20 dBZ左右,火灾点上空很小范围最大值达36 dBZ。(2)两次山火的灰烬飘浮物随环境风向下游扩散的最远距离分别是65 km和94 km,最高上升高度分别达3.7 km和4.8 km。(3)追踪烟羽的前沿可以估算相应高度上环境风的速度;两次火灾都发生在晴天,环境风速不大,除了烟羽边缘位置速度谱宽值较大外,其余部分速度谱宽都很小,大部分为1~2 m·s^(-1)。(4)相关系数(C_(c))、差分反射率(Z_(DR))和差分相移(ΦDP)探测到的范围与雷达反射率因子的演变形态和面积接近,同样随烟羽的扩散而逐渐增大;C_(c)值非常小,大多数区域小于0.9,少数距离库库元的C_(c)值低于0.5;火灾点上空的Z_(DR)值有相对较小的区域,为2~3 dB,而火灾点下风方,大部分Z_(DR)值都很大,大多超过5 dB。(5)两次森林火灾的双偏振探测特征表明,产生回波的反射物主要是干草、松针等燃烧后的灰烬形成的水平尺度较大的非球形粒子反射物。

高分辨率阻滞势分析仪设计与验证

为提高电推进羽流离子能量分布测量分辨率,设计研制了结构尺寸为Φ19 mm×24 mm的4栅型阻滞势分析仪(RPA)。设计关键参数为栅网网孔直径为0.3 mm,网孔心距为0.5 mm,电子排斥栅和离子阻滞势栅间距2 mm,能量分辨率为9.8%。RPA在LIPS-200离子电推进羽流区验证的结果表明:离子能量分布在955~1 047 eV,离子能量平均值为1 001.0 eV,ΔE_(FWHM)为36.1 eV,能量分辨率为3.6%。在LHT-40霍尔电推进羽流区验证结果表明:离子能量分布在220~279 eV,离子能量平均值为249.6 eV,ΔE_(FWHM)为23.4 eV,能量分辨率为9.4%。该RPA离子能量分辨率指标优于国内外同类产品,具有更小的测量不确定度。

低功率平面型霍尔推力器的工作特性研究

为了解决低功率霍尔推力器存在的寿命问题,本文设计了一种平面型霍尔推力器。该推力器取消了内部放电通道,前壁和阳极在同一平面,电离和加速过程完全发生在推力器外部的开放空间中。推力器在0.6~1.0 mg/s的氙气流量下,实现稳定放电。本文实验研究了不同运行参数下推力器的阳极电流特性、推力特性和羽流束流特性。结果表明,阳极电流的振荡频谱主要集中在20~60 kHz,与常规霍尔推力器的呼吸振荡频率范围相似。在62~245 W的功率下,推力为3.2~10.5 mN,阳极效率为8%~22%。推力水平与同功率等级的传统霍尔推力器相当,而阳极效率偏低。利用法拉第探针获得离子的束流特性,结果表明:较低的羽流发散效率是造成目前推力器阳极效率偏低的主要因素。结合实验结果,分析了平面型霍尔推力器与传统霍尔推力器在离子加速方面的差异。本文设计的平面型霍尔推力器为解决霍尔推力器的壁面侵蚀问题提出了一种可能的方案。

地外天体软着陆过程羽流扬尘特性研究现状及展望

地外天体软着陆过程中,反推发动机羽流作用于天体表面风化层诱发的侵蚀扬尘是影响软着陆安全的最主要因素。首先对羽流扬尘现象的物理过程、侵蚀机制研究现状进行梳理总结,总结出侵蚀机制主要包括粘性剪切侵蚀、扩散气体喷发、承载力破坏和扩散驱动流动4种;其次,对部分探月和探火任务的在轨侵蚀结果、仿真模型和经验公式的研究现状进行研究分析,得出月球表面和火星表面因背景压力和风化层物质特性差异会产生不同的侵蚀机制,而在相同条件下的侵蚀机制也会随发动机个数和总推力的变化而变化,有必要对物理机理和扬尘特性进行进一步细化研究;最后,结合未来地外天体软着陆任务需求,提出了羽流扬尘原位测量、仿真预测模型和羽流扬尘消除3种用于未来探测任务羽流扬尘预测和防护的关键技术,以期对未来软着陆任务顺利执行起到一定的保障作用。

Analysis of high-power disk laser welding stability based on classification of plume and spatter characteristics

Classification of plume and spatter images was studied to evaluate the welding stability. A high-speed camera was used to capture the instantaneous images of plume and spatters during high power disk laser welding. Characteristic parameters such as the area and number of spatters, the average grayscale of a spatter image, the entropy of a spatter grayscale image, the coordinate ratio of the plume centroid and the welding point, the polar coordinates of the plume centroid were defined and extracted. Karhunen-Loeve transform method was used to change the seven characteristics into three primary characteristics to reduce the dimensions. Also, K-nearest neighbor method was used to classify the plume and spatter images into two categories such as good and poor welding quality. The results show that plume and spatter have a close relationship with the welding stability, and two categories could be recognized effectively using K-nearest neighbor method based on Karhunen-Loeve transform.

四川盐源地区晚二叠纪双峰式火山岩的厘定及其地质意义

四川省盐源县柏林山一带广泛分布着一套基性岩、酸性岩的火山岩组合,两类火山岩在时空上紧密伴生,二者之间缺失中性火山岩,构成典型的双峰式火山岩组合。通过对区内双峰式火山岩的空间分布调查,基性岩主要为致密块状玄武岩、斑状玄武岩,酸性火山岩主要为碱流岩,碱流岩位于玄武岩顶部,为晚二叠纪峨眉山大火成岩省的组成部分。在地质背景、岩石学、地球化学等方面研究的基础上,对区内双峰式火山岩的成因和形成环境进行了探讨,表明玄武岩的原始岩浆来自富集型地幔源区,为地幔橄榄岩小程度部分熔融的产物,形成于洋岛构造环境,碱流岩主要为玄武岩浆极度分离结晶后的酸性残余岩浆形成,形成于陆内拉张构造环境。柏林山地区晚二叠纪双峰式火山岩的发现和厘定为峨眉山玄武岩的演化提供了新的线索和依据,为区域成矿研究以及稀有稀土找矿提供了新的启示。