Seismic stratigraphy of the Qiongdongnan deep sea channel system,northwest South China Sea

Based on more than 4000 km 2D seismic data and seismic stratigraphic analysis, we discussed the extent and formation mechanism of the Qiongdongnan deep sea channel. The Qiongdongnan deep sea channel is a large incised channel which extends from the east boundary of the Yinggehai Basin, through the whole Qiongdongnan and the Xisha trough, and terminates in the western part of the northwest subbasin of South China Sea. It is more than 570 km long and 4–8 km wide. The chaotic (or continuous) middle (or high) amplitude, middle (or high) continuity seismic facies of the channel reflect the different lithological distribution of the channel. The channel formed as a complex result of global sea level drop during early Pliocene, large scale of sediment supply to the Yinggehai Basin, inversion event of the Red River strike-slip fault, and tilted direction of the Qiongdongnan Basin. The large scale of sediment supply from Red River caused the shelf break of the Yinggehai Basin to move torwards the S and SE direction and developed large scale of prograding wedge from the Miocene, and the inversion of the Red River strike-slip fault induced the sediment slump which formed the Qiongdongnan deep sea channel.

DETECTION OF PPM ACOUSTIC PULSE IN SHALLOW SEA CHANNELS

Pulse pesition modulated (PPM) acoustic pulses are difficult to detect exacily in shallow sea channels because of strong multipath interference, large signal fluctuation and high noise level.This paper reports results of analysis on the main characteristics of multipath interference and its adverse effects on detection of pulse position information. Feasible methods to overeome multipath interference are pointed out, and an efficient one is proposed to realize reliable and precise detection of PPM information.The results of this study are of reference value for other modes of signal detection.

Sedimentary processes and development of the Zenisu deep-sea channel, Philippine Sea

Zenisu deep-sea channel originated from a volcanic arc region, Izu-Ogasawara Island Arc, and vanished in the Shikoku Basin of the Philippine Sea. According to the swath bathymetry, the deep-sea channel can be divided into three segments. They are Zenisu canyon, E-W fan channel and trough-axis channel. A lot of volcanic detritus were deposited in the Zenisu Trough via the deep-sea channel because it originated from volcanic arc settings. On the basis of the swath bathymetry, submersible and seismic reflection data, the deposits are characterized by turbidite and debrite deposits as those in the other major deep-sea channels. Erosion or few sediments were observed in the Zenisu canyon,whereas a lot of turbidites and debrites occurred in the E-W channel and trough axis channel. Cold seep communities,active fault and fluid flow were discovered along the lower slope of the Zenisu Ridge. Vertical sedimentary sequences in the Zenisu Trough consist of the four post-rift sequence units of the Shikoku Basin, among which Units A and B are two turbidite units. The development of Zenisu canyon is controlled by the N-S shear fault, the E-W fan channel is related to the E-W shear fault, and the trough-axis channel is related to the subsidence of central basin.

Estimating Synechococcus spp. growth rates and grazingpressure by heterotrophic nanoplankton in theEnglish Channel and the Celtic Sea

-Marine chroococcoid phycoerythrin - containing Synechococcus spp. recently have been implicated as a substantial component of the photosynthetic picoplankton in the ocean. Although the importance of Synechococcus as food sources for heterotrophic nanoplankton are now recognized, the information about its cycling of biomass and diel patterns is limited and the methodology used varies according to different authors. A selective metabolic inhibitor method was used to allow simultanous estimation of both growth rates and grazing disappearance rates of Synechococcus. Results obtained in the English Channel show growth rates ranging from 0. 25 to 0. 72 d-1 with an average value of 0. 51 d -1and grazing disappearance rates ranged from 0. 21 to 0. 64 d-1 (mean = 0. 44 d-1). Offshore in the Celtic Sea of the Northeast Atlantic Ocean, both rates were lower than in the channel. The similarity between average growth and grazing rates suggests a rapid recycling of Synechococcus biomass. In diel pattern, Synechococcus grazing mortality rates were higher during the day (mean = 0. 61 d-1) than during the night (mean = 0. 21d-1) in all the experiments. A positive correlation was observed between growth rates and in situ temperature ranged from 9 to 20 ℃. Sire-fractionated experiments demonstrate that up to about 7 0 % of Synechococcus disappearance could be attributed to the grazer smaller than 2 μm in diameter. The variations of Synechococcus cell characteristics such as size and phycoerythin contents in the growth and grazing experiments were determined with a flow cytometer. The methodology recently used on estimating dynamics of Synechococcus population is reviewed.

Provenance of Sediments Filling a Paleo-Channel that Formed on the Western Yellow Sea Continental Shelf During the Last Glacial Period

Several buried paleo-channels are located on the continental shelf of the western Yellow Sea. Research on the paleochannels is significant for both theoretical studies and practical applications. In this paper, we analyse and discuss the mineralogy of sediments in a core(SYS-0803) recovered from a buried paleo-channel on the continental shelf of the western Yellow Sea. The aim is to determine the provenance of sediments that fill the paleo-channel. The heavy mineral assemblage of sediments in the core consists of schistose minerals, common hornblende, epidote, and ilmenite. The light mineral assemblage consists of plagioclase, quartz, lithic fragments, and K-feldspar. Analysis of the compositional maturity of the sand fraction revealed a quartz/feldspar ratio of < 1. A relatively high percentage of smectite is recorded throughout the entire paleo-channel fill, with the greatest percentage in the middle to lower parts. The detrital mineral assemblage and clay mineral content indicate that the paleo-channel sediments were sourced mainly from the Huanghe River during the last glacial period.

Sedimentary characteristics comparison and genesis analysis of the deepwater channel in the hydrate enrichment zones on the north slope of the South China Sea

Natural gas hydrate(NGH) is one of the important clean energy at present and even in the future. The study of its sedimentary environment and minerogenetic condition has long been a hot issue that has received much concern from geologists all over the world. China has successfully obtained the samples of NGH in Shenhu and Dongsha sea areas in 2007, 2013 and 2015, respectively. From this, the continental slope north of the South China Sea becomes an important test site for the study of NGH sedimentary genesis and minerogenetic condition. NGH has been found in Shenhu, Dongsha and Qiongdongnan areas within the continental slope north of South China Sea,at different depths of water, with different sedimentary characteristics, gas genesis, and minerogenetic conditions.Using a seismic sedimentology theory, combining seismic facies results of each facies, sedimentary facies and evolution of each area are documented in turn establishing a sedimentary model by considering palaeogeomorphology, sea level change and tectonic movement. The channel system and MTD(Mass Transport Deposition) system among these three areas were compared focusing on the developing position, appearance and controlling factors. Relative location among three areas is firstly defined that Dongsha area in a nearprovenance steep upper slope, Shenhu area in a normal gentle slope and Qiongdongnan area in an awayprovenance flat plain. Besides, their channel systems are classified into erosional, erosional-aggradational and aggradational channel, and MTD systems into headwall domain, translational domain and toe domain.

Sedimentary Features of Shallow Ancient River Channels on the Northern Shelf of the South China Sea

Quaternary buried ancient river channels are widespread in the shallow-level sediments of the northern shelf of the South China Sea. The sedimentary sequence mainly of fluvial deposits comprise an important component part of the low-stand system tract and transgressive system tract in the study region. The plannar variation and spatial association of the sedimentary features such as incised valley fillings, deltaic foreset wedges and block slides of shelf-marginal fans reflect the palaeogeographic environment during the fall of the regional sea level in the northern part of the South China Sea. Based on the high-resolution seismic reflection data and gelogical data from boreholes, the present paper makes an integrated interpretation of the Quaternary ancient river channels in the shallow sediments of the study area, studies the sedimentary features of the ancient channels such as their spatial distribution, seismic facies reflection indicators, sedimentary facies and sand -body types, and discusses their formational setting and evolutionary model, with the main purpose to render a service to the hydrocarbon resources exploration and development and marine engineering in the northern shelf of the South China Sea.

Detection of nighttime sea fog/stratus over the Huang-hai Sea using MTSAT-1R IR data

A dual channel difference （DCD） method is applied to detect nighttime sea fog/stratus over the Huanghai Sea using the infrared （IR） data of shortwave （3.5-4.0 μm） and longwave （10.3-11.3 μm） channels from the Multi-functional Transport Satellite （MTSAT）-IR, i.e., shortwave minus longwave brightness temperature difference （SLTD）. Twenty-four sea fog events over the Huanghai Sea during March to July of 2006 and 2007 are chosen to determine a suitable value of SLTD for nighttime sea fog/stratus detection, and it is found that the value of-5.5-2.5℃ can be taken as a criterion. Two case examples of sea fog events are especially demonstrated in detail utilizing the criterion, and the results show that the derived sea fog/stratus coverage is quite reasonable. This coverage information is very helpful to analyze the formation and evolution of sea fog/stratus during night and can provide sea fog researchers with observational evidences for model results verification. However, more efforts are needed to further obtain vertical extent information of sea fog/stratus and attempt to discriminate between sea fog and stratus.

Mass transport deposits and processes in the north slope of the Xisha Trough,northern South China Sea

Triple mass-transport deposits （MTDs） with areas of 625, 494 and 902 km^2, respectively, have been identified on the north slope of the Xisha Trough, northern South China Sea margin. Based on high-resolution seismic reflection data and multi-beam bathymetric data, the Quaternary MTDs are characterized by typical geometric shapes and internal structures. Results of slope analysis showed that they are developed in a steep slope ranging from 5° to 35°. The head wall scarps of the MTDs arrived to 50 km in length （from headwall to termination）. Their inner structures include well developed basal shear surface, growth faults, stepping lateral scarps, erosion grooves, and frontal thrust deformation. From seismic images, the central deepwater channel system of the Xisha Trough has been filled by interbedded channel-levee deposits and thick MTDs. Therefore, we inferred that the MTDs in the deepwater channel system could be dominated by far-travelled slope failure deposits even though there are local collapses of the trough walls. And then, we drew the two-dimensional process model and three- dimensional structure model diagram af the MTDs. Combined with the regional geological setting and previous studies, we discussed the trigger mechanisms of the triple MTDs.

面向东北海陆大通道的辽宁港口群协同发展耦合度研究

为推进东北海陆大通道的构建,利用2019—2022年度辽宁省六个港口的数据,运用熵权法和耦合协调模型,对港口群的整体协同度进行评价。评价结果显示,近四年辽宁港口群的耦合协同度一直处于濒临失调的状态,港口间的耦合协调度较低,自身协调度较低。应采取具体业务间的角色协调、统筹,加强港口间的协同,实现港口群的有序合理优化,最终达到整体功能大于局部功能之和的效果。

基于改进暗通道先验的海上低照度图像增强算法

针对基于暗通道先验的低照度图像增强算法在处理极端海上低光环境下图像时会存在光晕效应、色彩失真的问题,提出了1种基于暗通道先验的自适应海上低照度图像增强算法。首先,通过选取图像类型划分指标,将数据集中的图像分类,并通过Otsu方法和图像直方图分布,获取图像的区域划分阈值,将图像进行划分得到局部区域图,分析各类图像的局部区域图之间的关系;最后,通过对不同的局部区域图采用不同的改进暗通道先验算法进行处理,将1个图像中的2个增强后局部区域图合并,得到整张图像的增强结果,并对增强后图像进行主客观的图像质量评价。实验结果表明,该算法解决了现有算法在处理极端海上低照度图像时存在光晕效应和色彩失真的问题,并使不同环境下的海上低照度图像都能达到较好的恢复效果。

Buried channels provide keys to infer Quaternary stratigraphic and paleo-environmental changes:A case study from the west coast of India

High resolution shallow seismic data was acquired from inner continental shelf of Goa,west coast of India to map underlying stratigraphic and buried geomorphic features of shelf strata.Seismic data revealed characteristic channel incisions beneath 4-15 m thick sediment layer and corresponds to multi cycle incisions.Stratigraphic analysis of these incision signatures reveals three prominent subaerial unconformities S6,S7 and S9.These unconformities were exposed during the last glacial,penultimate glacial(MIS-6)and prior to penultimate glacial(MIS-8)periods.On the basis of interpreted age of subaerial unconformities and differences in their morphological features,observed channel incisions have been divided grossly into three phases of incision.Phase-1 incisions are older than^330 kyr BP,whereas,incisions of Phase-2 and Phase-3 correspond to^320-125 kyr BP and^115-10 kyr BP respectively.Plan form of these incisions varied from a straight channel type to ingrown meander and then to anastomosing channel types.These channels meet at the confluence of present-day Mandovi and Zuari rivers.The confluence point has varied in due course of time because of cyclic incision and burial with repeated sea level fluctuations.The preserved main channel width varies from^100 m to 1000 m.and maximum channel depth reaches up to^35 m.Comparison of quantitative and qualitative morphologic results of different phases of incisions suggest that Phase-2 channels had^33%more mean bank full discharge than that of the Phase-3 channels.Phase-2 incisions had been carved in higher hydraulic energy condition as compared to Phase-3 incisions implying that the Indian summer monsoon was better during formative stages of Phase-2 incisions.

西部陆海新通道沿线地区对外开放水平测度、格局及影响因素分析

对外开放度是衡量一个国家或地区竞争力的重要指标,也是经济发展水平的重要体现。通过构建适应西部陆海新通道沿线地区的对外开放水平测度指标体系和分析模型,对通道沿线地区对外开放水平进行测度,并对其开放度的影响因素进行分析。研究发现:西部陆海新通道沿线地区总体对外开放水平呈现着良好的增长趋势,但通道沿线地区对外开放度呈现西南地区显著高于西北地区,并形成以海南、重庆为高度开放区;广西、四川、陕西、云南为中高度开放区;新疆、西藏、内蒙古、宁夏为中度开放区;青海、甘肃、贵州为低度开放区四个等级层次的对外开放格局。实证分析发现西部陆海新通道沿线地区开放格局主要受地区经济发展水平、交通设施水平和国家开放战略的影响。

基于不同海况条件下的空海信道建模

针对不同海况下的空海通信场景,提出一种基于几何的信道模型。该模型在不同海况条件下,将无线电在海平面上的反射分为镜面反射和漫反射,并将海况对接收信号点的影响等效为对接收信号的高度和接收天线倾斜角的影响。所建立的等效散射圆柱体的直径由不同海况下理想镜面反射点之间的距离决定,圆柱体的高度由海浪对接收信号点的影响高度决定。基于所提出的信道模型,推导并仿真分析了时延迟自相关函数、频率自相关函数。结果表明,不同海况条件下不同延迟和不同频率间隔会显著影响信道的统计特性。

宁波舟山港中部海域船舶通过能力适应性分析

宁波舟山港中部海域四面岛屿环抱,船舶只能通过几处航门进出。东侧的灌门和龟山航门船舶通航潮流条件、南侧的金塘大桥和西堠门大桥最大通航船型限定均较严格。通过对灌门和龟山航门水域的潮流观测,设定船舶依次排队通过工况对2处航门的航道通过能力进行分析,并对金塘和西堠门大桥的通航尺度和现行规范进行适应性分析,研究净空尺度起算面、船舶水线以上高度、桥梁坡度和挠度、桥梁净高和过路船舶水线以上最大高度实时测量系统。结果表明,灌门和龟山航门的通过能力与中部海域港口规划发展相适应。宜建立大型船舶过桥动态审批制度,从而起到释放水域岸线发展潜力的效果。

北极冰下水平变化双声道波导声传播特性

针对北极部分海域中的双声道波导现象,研究了冰层覆盖下水平变化双声道波导中的声传播。使用微扰法推导并确定了粗糙下表面的冰层反射系数,结合Bellhop射线模型,计算并分析了实测海域中双声道波导水平变化时的声传播特性,并研究了声源深度、声源入射角以及声源频率对水平变化的双声道波导中声传播的影响规律。结果表明,在北极,深海声道中的声传播大多被限制在深海声道的上、下边缘之间;声源与水平变化的深海声道轴处于同一深度时声传播损失较小,当声源位于深海声道边界以外时,水平变化的声速剖面相比于水平不变时具有更低的声传播损失;入射角对双声道波导中声传播影响较小;随着声源频率的增加,表面声道中声传播损失也随之增大,但是对深海声道影响不明显,在相同频率下水平变化的声速剖面更利于声传播。

深海远程单阵元水声通信的逐多径簇联合均衡方法

利用深海远程水声信道的稀疏多径簇具有簇间长时延、簇内结构简单的特性,提出一种用于深海远程单阵元水声通信的低复杂度逐多径簇联合均衡方法。首先,在数据帧中插入无保护间隔的m序列进行稀疏多径簇的检测和同步;然后,对选择的多径簇信号逐个进行基于比例快速后验误差技术的低复杂度均衡,并逐个对均衡器的输出根据对应多径簇的时延进行对齐;最后,将时延对齐的均衡器输出进行最大比合并,从而以并–串转换方式将逐个多径簇软解调信息合并后输入到译码器。相对于常规均衡方法,所提方法将对整体信道多径的均衡分解为对具有简单结构多径簇的逐个均衡,获得多径簇分集增益的同时结合Polar信道编码进一步改善解调性能。数值仿真和深海实验结果表明,所提方法的输出信噪比和误比特率性能明显优于单阵元及双阵元常规均衡,在30 km的通信距离中实现了通信速率为4000 bit/s的单阵元无误码通信,可有效应用于深海远程单阵元水声通信。

基于YOLOv4的水下海参检测与计数算法

针对智慧水产养殖中海参自动采捕和高效计量应用需求,提出一种基于YOLOv4的水下海参检测与计数算法。该算法利用暗通道先验算法对数据集进行预处理,增强图像数据的可检测性;采用迁移学习方法训练YOLOv4网络,并用Swish函数替换骨干网络中的激活函数,提升自建数据集的海参检测性能;提出基于相近帧目标质心定位偏移的降重计数方法,优化目标计数结果。试验结果表明:该检测算法识别水下海参目标的平均检测精度的平均值mAP达91.0%,分别比原始YOLOv4、YOLOv3、Faster R-CNN和SDD高4.5%、6.9%、5.0%、29.9%;降重计数算法获得海参数量与人工计数结果间的均方根误差RMSE为29.8、平均计数精度ACP为95.8%、决定系数R2为0.998。

淮河入海水道二期工程中河道护坡铺砌工艺的优化

介绍了河道护坡预制块铺砌工艺、特点及施工方法。以入海水道二期工程河道为例,通过对人力抬运铺砌、小型履带式挖掘机吊装、大型吊车铺砌3种铺砌方式的比较,阐明了大型吊车铺砌这种工艺的优点。

碳达峰时点下渤海通道对区际城市群公路物流碳排放及减排潜力的影响

以2030年“碳达峰”为研究时点,通过IPCC(Intergovernmental Panel on Climate Change,联合国政府间气候变化专门委员会)“自下而上”法和社会网络分析法,探究不同通道情境下区际城市群公路物流碳排放及其减排潜力的网络格局,分析渤海通道对其产生的影响。研究表明:①2030年不同通道情境的区际城市群公路物流碳排放网络差异:陆上通道情境下,区际城市群碳交流向经济、交通发达轴带和渤海海峡端点城市集中;陆海通道情境下,区际碳交流向邻近陆上通道的城市集聚;渤海通道改善了区际城市群“渤海海峡端点城市”指向的高耗能局面。②2030年区际城市群公路物流减排潜力网络格局:以大连为减排枢纽,以渤海海峡为中心,强减排城市组对南多北少,并存在零减排城市组对;渤海通道主要通过端点城市向其他城市施以碳减排影响,对距其较远且处在公路物流边缘的部分城市的碳减排影响较为有限。