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Channel Correlation Based User Grouping Algorithm for Nonlinear Precoding Satellite Communication System

China Communications 2024年第1期21卷 200-214页

作者： Ke wang Baorui Feng Jingui Zhao Wenliang Lin Zhongliang Deng dongdong wang Yi Cen Genan Wu School of Information and Communication Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China School of Information Engineering Minzu University of ChinaBeijing 100081China Institute of Spacecraft Application System Engineering China Academy of Space TechnologyBeijing 100094China Academy for Network and Communications of CETC Science and Technology on Communication Networks LaboratoryShijiazhuang 050081China

Low Earth Orbit(LEO)multibeam satellites will be widely used in the next generation of satellite communication systems,whose inter-beam interference will inevitably limit the performance of the whole system.Nonlinear precoding such as Tomlinson-Harashima precoding(THP)algorithm has been proved to be a promising technology to solve this problem,which has smaller noise amplification effect compared with linear precoding.However,the similarity of different user channels(defined as channel correlation)will degrade the performance of THP algorithm.In this paper,we qualitatively analyze the inter-beam interference in the whole process of LEO satellite over a specific coverage area,and the impact of channel correlation on Signal-to-Noise Ratio(SNR)of receivers when THP is applied.One user grouping algorithm is proposed based on the analysis of channel correlation,which could decrease the number of users with high channel correlation in each precoding group,thus improve the performance of THP.Furthermore,our algorithm is designed under the premise of co-frequency deployment and orthogonal frequency division multiplexing(OFDM),which leads to more users under severe inter-beam interference compared to the existing research on geostationary orbit satellites broadcasting systems.Simulation results show that the proposed user grouping algorithm possesses higher channel capacity and better bit error rate(BER)performance in high SNR conditions relative to existing works.

关键词： channel correlation inter-beam interference multibeam satellite Tomlinson-Harashima precoding user grouping

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Inertinite in coal and its geoenvironmental significance:Insights from AI and big data analysis

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Science China Earth Sciences 2024年第6期67卷 1779-1801页

作者： Longyi SHAO Jiamin ZHOU Timothy PJONES Fanghui HUA Xiaotao XU Zhiming YAN Haihai HOU dongdong wang Jing LU State Key Laboratory for Fine Exploration and Intelligent Development of Coal Resources and College of Geoscience and Surveying Engineering China University of Miningand Technology(Beijing)Beijing 100083China School of Earth and Environmental Sciences Cardiff UniversityCardiff CF103YEWalesEngland General Prospecting Institute of China National Administration of Coal Geology Beijing 100039China Institute of Architectural Engineering Weifang UniversityWeifang 261061China College of Mining Liaoning Technical UniversityFuxin 123000China College of Earth Science and Engineering Shandong University of Science and TechnologyQingdao 266590China

Inertinite,as an important and abundant maceral group in coal,is critical for the study of palaeowildfires and their roles in the Earth’s ecosystems.Recently,there has been a significant amount of research on the relationship between palaeowildfire,palaeoclimate change and palaeovegetation evolution based on inertinite data.The reflectance of fusinite and semifusinite has been used to estimate the combustion temperature and type of palaeowildfires,and then to evaluate the combustion characteristics of different types of palaeowildfires.The relative abundance of inertinite can be used to estimate the atmospheric oxygen contents.The rapid development of artificial intelligence(AI)and online tools to search scientific databases has presented an opportunity for us to find,collect,arrange,and analyse data from the earliest to latest publications on inertinite.The data extraction tool Deep Shovel is used to collect and analyse global inertinite data from the Silurian to the Neogene.The software programs such as Gplates,ArcGIS pro and Tableau are then applied to model the relative abundance of inertinite over geological time,which can be correlated with other parameters such as atmospheric oxygen contents,plant evolution and palaeoclimate changes.The distribution of inertinite in coals varied over different geological periods,being typified by the“high inertinite content-high atmospheric oxygen level”period in the Permian and the“low inertinite content-low atmospheric oxygen level”period in the Cenozoic.This study has proposed a possible model of the positive and negative feedbacks between inertinite characteristics and palaeoenvironmental factors,and has revealed the exceptional role of inertinite in palaeoenvironmental studies.Future research on inertinite will be focused on the integrated study of organic petrology and organic geochemistry of inertinite,the big data-driven research on the temporal and spatial distribution of the global inertinite,the exploration of the functions of palaeowildfires in the Earth system

关键词： Inertinite Palaeowildfires Atmospheric oxygen Palaeoclimates Palaeoecosystems

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Genetic relationship between formation,accumulation and migration and dispersion of peat materials in Paleogene——Take the Qiongdongnan Basin as an example

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Acta Oceanologica Sinica 2024年第4期43卷 80-91页

作者： Xiaojing Li Zengxue Li dongdong wang Guangzeng Song Pingli wang Haiyan Liu Key Laboratory of Sedimentary Mineralization and Sedimentary Minerals in Shandong Province Qingdao 266590China Shandong University of Science and Technology Qingdao 266590China School of Water Conservancy and Environment University of JinanJinan 250022China

Coal-type source rocks include both coal and terrigenous marine source rocks.By studying the distribution of secondary depressions,uplifts,as well as the characteristics of peat formation and accumulation in the northern marginal sea basin of the South China Sea,and combining them with coal formation characteristics observed in other basins,five genetic theories on the relationship between peat accumulation and dispersed organic matter accumulation are proposed.The northern marginal sea basin of the South China Sea is characterized by“disadvantageous coals formation and favorable terrigenous marine source rocks formation.”This paper provides a distribution map of coal seams and terrigenous marine source rocks in the Qiongdongnan Basin and determines their distribution patterns.Research shows that the migration of sedimentary facies in the basins and inner depressions led to the formation and migration of the peat accumulation centers.In addition,the vertical migration of the peat accumulation centers led to planar migration,which is actually a type of coupling relationship.Previous research results have revealed that the formation of coal-type source rock is multi-phased.The marginal sea basin is composed of several fault-depression basins,with each basin developing a second order of depression and uplift.There is no unified basin center or depositional center to be found.As a result,the concentration centers of coal-forming materials also vary greatly.Based on the distribution characteristics of coal-type source rocks in different basins within the marginal sea basins of the South China Sea,the research results have practical significance and provide guidance for exploring coal-type oil and gas reservoirs in this area.

关键词： Coal-type source rock marginal sea basins migration of peat aggregation centers terrigenous marine source rock Qiongdongnan Basin

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Plant resources and diversity analysis of Sejila Mountain in southeast Tibet

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Asian Journal of Traditional Medicines 2024年第3期19卷 152-158页

作者： Lianyu Tang dongdong wang Jingming Jia Anhua wang School of Traditional Chinese Materia Medica Shenyang Pharmaceutical UniversityShenyang 110016China

Sejila Mountain is located in Linzhi City,southeast Tibet.The terrain is high,and the climate is cold and dry.The special ecological environment determines the richness and diversity of plant resources.In this study,the plant resources and diversity of Sejila Mountain were studied through field investigation,literature review and specimen identification.282 plant species belonging to 199 genera and 81 families were collected from July to August in 2021.The dominant families are Asteraceae,Ranunculaceae and Rosaceae.In terms of life form,perennial herbs are the main form,accounting for 58.16%of the total.178 species of medicinal plants were collected,including 33 species of Tibetan medicine.In terms of medicinal parts,the whole grass is mainly used as medicine,followed by roots and rhizomes.In conclusion,our study has updated the plant resources and diversity of Sejila Mountain.Based on the investigation and research,some suggestions were put forward to strengthen the protection and utilization of the plant resources in Sejila Mountain.

关键词： plant resources diversity Tibetan medicine Sejila Mountain

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Astronomical influence of the development of Paleogene thin coal seam groups in offshore Lacustrine basins:A case study of the ZhuⅠDepression's Enping Formation located in the northern South China Sea

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Acta Oceanologica Sinica 2024年第4期43卷 136-150页

作者： Yan Liu Shengbing Huang dongdong wang Nan Li Yuting Yin Ying Chen Zengxue Li College of Earth Science and Engineering Shandong University of Science and TechnologyQingdao 266590China CNOOC Research Institute Co. Ltd.Beijing 100028China School of Geography Earth and Environmental SciencesUniversity of BirminghamBirmingham B152TTUK

The development of the Paleogene coal seams in China's offshore basin areas generally had the characteristics of coal measures with large thicknesses,large numbers of coal seams,thin single coal seams,poor stability,scattered vertical distribution,and a wide distribution range.This study selected the Enping Formation of the ZhuⅠDepression in the northern section of the South China Sea as an example to determine the macro-control factors of the development of the Paleogene coal seam groups.An analysis was carried out on the influencing effects and patterns of the astronomical cycles related to the development of the thin coal seam groups in the region.A floating astronomical time scale of the Enping Formation was established,and the sedimentary time limit of the Enping Formation was determined to be approximately 6.15 Ma±.In addition,the cyclostratigraphy analysis results of the natural gamma-ray data of Well XJ in the Enping Formation of the Xijiang Sag revealed that the development of the thin coal seams had probably been affected by short eccentricity and precession factors.The formation process of coal seams was determined to have been affected by high seasonal contrast,precipitation,and insolation.During the periods with high values of short eccentricity,the seasonal contrasts tended to be high.During those periods,fluctuations in the precession controls resulted in periodic volume changes in precipitation and insolation of the region,resulting in the development of thin coal seams.It was also found that the periods with low precession were the most conducive to coal seam development.On that basis,combined with such factors as sedimentary environmental conditions conducive to the development of thin coal seam groups,this study established a theoretical model of the comprehensive influences of short eccentricity and precession on the development and distribution of Paleogene thin coal seam groups in offshore lacustrine basins.The patterns of the Paleogene astronomical periods and paleoclimate evolution,along w

关键词： Paleogene Pearl(Zhujiang)River Mouth Basin coal seam development astronomical cycles

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Formation environment and hydrocarbon potential of the Paleogene Enping Formation coal measures in the ZhuⅠDepression of northern South China Sea

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Acta Oceanologica Sinica 2024年第4期43卷 119-135页

作者： Yuting Yin Lei Lan dongdong wang Ying Chen Yan Liu Youchuan Li Zengxue Li Jiamin Liu College of Earth Science and Engineering Shandong University of Science and TechnologyQingdaoShandong 266590China China National Offshore Oil Corporation Research Institute Co. Ltd.Beijing 100028China School of Geography Earth and Environmental SciencesUniversity of BirminghamBirminghamB152TTUK

The coal-measure source rock in the Chinese sea area plays a significant role as a hydrocarbon source rock,with its genetic environment,development and distribution,and hydrocarbon generation potential serving as essential factors for the exploration of coal-type oil and gas fields.This study focuses on the coal-measure source rock of the Paleogene Enping Formation in the ZhuⅠDepression,located in the northern South China Sea.The main geological insights obtained are as follows.The coal measures of the Enping Formation are developed in a warm and wet tropical-subtropical climate.The development environment of the coal-measure source rock in the Enping Formation includes the braided river delta upper plain peat swamp,characterized by dry forest swamp coal facies with relatively thick coal seams and a small number of layers.The braided river delta lower plain swamp-interdistributary bay of braided river delta front represents a forest edge-wetland herbaceous swamp coal facies with numerous layers of thin coal seams and poor stability.The shore swamp corresponds to an open water swamp coal facies with multiple layers of thin coal seams and poor stability.The organic matter abundance in the braided river delta upper plain is the highest,followed by the braided river delta lower plain-braided river delta front,and the shore-shallow lake.The organic matter type is predominantly typeⅡ1.Thermal evolution analysis suggests that the organic matter has progressed into a substantial oil generation stage.The hydrocarbon generation potential of the coal-measure source rock in the Enping Formation is the highest in the braided river delta upper plain,followed by the braided river delta lower plain-braided river delta front and the shore-shallow lake.Overall,this study proposes three organic facies in the coal-measure source rock of the Enping Formation:upper-plain swamp-dry forest swamp facies,lower plain-interdistributary bay-forest-herbaceous swamp facies,and lake swamp-herbaceous swamp facies.

关键词： coal-measure source rock Paleogene genetic environment hydrocarbon generation characteristic ZhuⅠDepression

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Numerical study on the cavity dynamics for vertical water entries of twin spheres

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Defence Technology（防务技术） 2024年第2期32卷 459-472页

作者： Xu wang Xujian Lyu Ruisheng Sun dongdong Tang School of Energy and Power Engineering Nanjing University of Science and TechnologyNanjing210094China Shanghai Institute of Spacecraft Equipment Shanghai200240China

In this study, a three dimensional(3D) numerical model of six-degrees-of-freedom(6DOF) is applied to simulate the water entries of twin spheres side-by-side at different lateral distances and time intervals.The turbulence structure is described using the shear-stress transport k-ω(SST k-ω) model, and the volume of fluid(VOF) method is used to track the complex air-liquid interface. The motion of spheres during water entry is simulated using an independent overset grid. The numerical model is verified by comparing the cavity evolution results from simulations and experiments. Numerical results reveal that the time interval between the twin water entries evidently affects cavity expansion and contraction behaviors in the radial direction. However, this influence is significantly weakened by increasing the lateral distance between the two spheres. In synchronous water entries, pressure is reduced on the midline of two cavities during surface closure, which is directly related to the cavity volume. The evolution of vortexes inside the two cavities is analyzed using a velocity vector field, which is affected by the lateral distance and time interval of water entries.

关键词： Twin water entries Side-by-side Cavity Numerical simulation

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Complex granular flows of sticky-wet material on flip-flow screens:Calibration of discrete element simulations

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Particuology 2024年第1期84卷 290-308页

作者： Ningning Xu Sen Tang dongdong Lin Runhui Geng Xinwen wang Xihui Liang School of Chemical and Environmental Engineering China University of Mining and Technology(Beijing)Beijing100083China Department of Mechanical Engineering University of ManitobaWinnipegManitobaR3T 5V6Canada

Discrete element method(DEM)is an effective approach for studying the screening process of flip-flow screens.However,there have been few studies focusing on the thick layer of sticky-wet particles on flip-flow screens.To achieve accurate simulations of the thick layer of sticky-wet particles on a flip-flow screen,firstly,the movement law of particle flow was studied,and a multi-regime combination cali-bration method based on characteristics of particle flow regimes was proposed.Based on the Plackett-Burman experiment,the curse of dimensionality caused by multi-state and multi-contact parameters was overcome.Subsequently,the lifting cylinder,rotating drum,and trampoline tests were carried out to obtain macroscopic reference values under various granular flow regimes.The calibration results were then determined using the response surface method and climbing algorithm.Finally,the calibration results were tested at both macroscopic and mesoscopic scales and compared with a commonly used calibration method.The results demonstrate that the calibration method,which considers the multi-state characteristics,improves simulation accuracy by 2%-10%and reduces the simulation error to less than 10%,thus meeting the requirements for engineering optimization of flip-flow screens.

关键词： DEM Complex granular flow Parameter calibration Flip-flow screen Sticky-wet particles Thick layer

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Flow characteristics of radial inflow in impeller rear cavity with baffle plate

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Chinese Journal of Aeronautics 2024年第2期37卷 270-282页

作者： Yang BAI Xiang LUO dongdong LIU Zeyu WU Xiaoqiang ZHANG Sipeng wang Research Institute of Aero-Engine Beihang UniversityBeijing 100191China National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics Beihang UniversityBeijing 100191China School of Energy and Power Engineering Beihang UniversityBeijing 100191China

The research purpose of this paper is to explore the influence of the baffle plate on the airflow in the rear cavity of the centrifugal impeller and optimize the performance of the secondary air system’s air bleed section.In this paper,a comprehensive experimental study was carried out on the flow characteristics in the impeller rear cavity with baffle plate.The windage torque,flow structure and pressure drop between inlet and outlet were measured respectively.The experiment was carried out with the condition that the range of rotational Reynolds number was from 8.33×10^(5)to 22.2×10^(5)and the range of mass flow rate coefficient was from 0.92×10^(4)to 2.92×10^(4).The results show that the static cavity and the narrow stator-rotor cavity formed by the baffle plate effectively suppress the overall swirl coefficient in the cavity.Thus,the static pressure and total pressure drop in the rotor-stator cavity were reduced.The influence of the baffle plate on the windage torque of the rotary disk is related to the turbulence parameters.Under large turbulence parameters,the windage torque would be reduced with baffle plate,while under small turbulence parameters,the baffle plate would increase with baffle plate.In general,the baffle plate can improve the flow capacity and optimize the bleed air performance with proper structure and operation conditions.

关键词： Impeller rear cavity Baffle plate Flow structure Windage torque Pressure drop

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Preparation of CIP@TiO_(2) composite with broadband electromagnetic wave absorption properties

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International Journal of Minerals,Metallurgy and Materials 2024年第1期31卷 197-205页

作者： Qiang Su Hanqun wang Yunfei He dongdong Liu Xiaoxiao Huang Bo Zhong School of Materials Science and Engineering Harbin Institute of TechnologyWeihaiWeihai 264209China School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China

Scholars aim for the improved impedance matching (Z) of materials while maintaining their excellent wave absorption properties. Based on the hydrolysis characteristics of isopropyl titanate, a simple preparation process for the coating of carbonyl iron powder(CIP) with TiO_(2) was designed. Given the TiO2coating, the Z of the CIP@TiO_(2) composite was adjusted well by decreasing the dielectric constant. Moreover, the interfacial polarization of CIP@TiO_(2) was enhanced. Ultimately, the electromagnetic-wave (EMW) absorption property of the CIP@TiO_(2)composite was improved substantially, the minimum reflection loss reached-46.07 dB, and the effective absorption bandwidth can reach 8 GHz at the composite thickness of 1.5 mm. Moreover, compared with CIP, the oxidation resistance of CIP@TiO_(2)showed remarkable improvement. The results revealed that the oxidation starting temperature of CIP@TiO_(2) as about 400℃,whereas the uncoated CIP had an oxidation starting temperature of approximately 250℃. Moreover, the largest oxidation rate temperature of CIP@TiO_(2) increased to around 550℃. This work opens up a novel strategy for the production of high-performance EMW absorbers via structural design.

关键词： carbonyl iron@titanium dioxide electromagnetic-wave absorption impedance matching oxidation resistance

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