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Configurable Virtual MIMO via UAV Swarm:Channel Modeling and Spatial Correlation Analysis

China Communications 2022年第9期19卷 133-145页

作者： jiachen Qian Jue Wang Shi Jin National Mobile Communications Research Laboratory Southeast UniversityNanjing 210096China School of Information Science and Technology Nantong UniversityNantong 226109China Nantong Research Institute for Advanced Communication Technologies Nantong 226109China

Air-to-ground wireless channel modeling for unmanned aerial vehicle(UAV)communications has been widely studied.However,channel modeling for UAV swarm-enabled cooperative communication still needs investigation,where the impact of UAV positions on the spatial channel characteristics is of particular importance.In this paper,we consider a UAV swarm-enabled virtual multiple input multiple output(MIMO)system,where multiple single-antenna UAVs cooperatively transmit to multiple ground users(GUs).We establish a common coordinate system,as well as a UAV swarm-oriented coordinate system,to describe the relative positions of the GUs and the UAV elements,respectively.Based on the established coordinate systems,geometric ray superposition method is applied to describe the spatial channel matrix.The proposed modeling framework can be directly used to describe the line-of-sight and two-ray propagations,and can be extended for including more practical spatial features such as multipath scattering,inter-UAV blockage,and random UAV jittering,etc.Based on the proposed model,we further analyze the spatial correlation among the virtual MIMO links of GUs located at different positions.Via extensive simulations,we show that thanks to the flexible deployment of UAVs,the virtual MIMO array structure can be conveniently configured to get desired channel properties,such as the channel capacity,eigenvalue and condition number distribution,and spatial correlation distribution.This shows the possibility and importance of exploiting a new design dimension,i.e.,the UAV swarm pattern,in such cooperative virtual MIMO systems.

关键词： UAV communications MIMO channel model spatical correlation

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Functional aspects of the brain lymphatic drainage system in aging and neurodegenerative diseases

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Journal of Biomedical Research 2024年第3期38卷 206-221页

作者： Yan Chen Xiaoxin He jiachen Cai qian Li Jiangsu Key Laboratory of Neurodegeneration Nanjing Medical UniversityNanjingJiangsu 211166China Shandong Institute of Brain Science and Brain-inspired Research Shandong First Medical University&Shandong Academy of Medical SciencesJinanShandong 250117China Center for Global Health Nanjing Medical UniversityNanjingJiangsu 211166China

The phenomenon of an aging population is advancing at a precipitous rate.Alzheimer's disease(AD)and Parkinson's disease(PD)are two of the most common age-associated neurodegenerative diseases,both of which are primarily characterized by the accumulation of toxic proteins and the progressive demise of neuronal structures.Recent discoveries about the brain lymphatic drainage system have precipitated a growing body of investigations substantiating its novel roles,including the clearance of macromolecular waste and the trafficking of immune cells.Notably,aquaporin 4-mediated glymphatic transport,crucial for maintaining neural homeostasis,becomes disrupted during the aging process and is further compromised in the pathogenesis of AD and PD.Functional meningeal lymphatic vessels,which facilitate the drainage of cerebrospinal fluid into the deep cervical lymph nodes,are integral in bridging the central nervous system with peripheral immune responses.Dysfunction in these meningeal lymphatic vessels exacerbates pathological trajectory of the age-related neurodegenerative disease.This review explores modulatory influence of the glymphatic system and meningeal lymphatic vessels on the aging brain and its associated neurodegenerative disorders.It also encapsulates the insights of potential mechanisms and prospects of the targeted non-pharmacological interventions.

关键词： glymphatic system meningeal lymphatic vessels aging neurodegenerative diseases nonpharmacological therapies

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Cybertwin-Assisted Mode Selection in Ultra-Dense LEO Integrated Satellite-Terrestrial Network

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Journal of Communications and Information Networks 2022年第4期7卷 360-374页

作者： Xin Zhang Bo qian Xiaohan Qin Ting Ma jiachen Chen Haibo Zhou Xuemin(Sherman)Shen School of Electronic Science and Engineering Nanjing UniversityNanjing 210023China Laboratory Shenzhen 518000China Department of Electrical and Computer Engineering University of WaterlooWaterlooON N2L 3G1Canada

Ultra-dense low earth orbit(LEO)integrated satellite-terrestrial network(ULISTN)has become an emerging paradigm to support massive access of Internet of things(IoT)in beyond fifth generation mobile networks(B5G).In ULISTN,there are two communication modes:cellular mode and satellite mode,where IoT users assessing terrestrial small base stations(TSBSs)and terrestrial-satellite terminals(TSTs)respectively.However,how to optimize the network performance and guarantee self-interests of the operator and IoT users in ULISTN is a challenging issue.In this paper,we propose a cybertwin-assisted joint mode selection and dynamic pricing(JMSDP)scheme for effective network management in ULISTN,where cybertwin serves as the intelligent agent.In JMSDP,the operator determines optimal access prices of TSBSs and TSTs,while each user selects the access mode according to access prices.Specifically,the operator conducts the Stackelberg game aiming at maximizing average throughput depending on the mode selection results of IoT users.Meanwhile,IoT users as followers adopt the evolutionary game to choose an access mode based on the access prices provided by the operator.Simulation results show that the proposed JMSDP can improve the average throughput and reduce the delay effectively,comparing with random access(RA)and maximum rate access.

关键词： ULISTN massive IoT cybertwin mode selection dynamic pricing game theory

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Epigenetic regulation of hematopoietic stem cell homeostasis

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Blood Science 2019年第1期1卷 19-28页

作者： Penglei Jiang Hui Wang jiachen Zheng Yingli Han He Huang Pengxu qian Center of Stem Cell and Regenerative Medicine and Bone Marrow Transplantation Center of the First Affiliated HospitalZhejiang University School of MedicineHangzhouP.R.China Institute of Hematology Zhejiang Engineering Laboratory for Stem Cell and ImmunotherapyZhejiang UniversityHangzhouP.R.China

As one of the best characterized adult stem cells,hematopoietic stem cell(HSC)homeostasis is of great importance to hematopoiesis and immunity due to HSC’s abilities of self-renewal and multi-lineage differentiation into functional blood cells.However,excessive self-renewal of HSCs can lead to severe hematopoietic malignancies like leukemia,whereas deficient selfrenewal of HSCs may result in HSC exhaustion and eventually apoptosis of specialized cells,giving rise to abnormalities such as immunodeficiency or anemia.How HSC homeostasis is maintained has been studied for decades and regulatory factors can be generally categorized into two classes:genetic factors and epigenetic factors.Although genetic factors such as signaling pathways or transcription factors have been well explored,recent studies have emerged the indispensable roles of epigenetic factors.In this review,we have summarized regulatory mechanisms of HSC homeostasis by epigenetic factors,including DNA methylation,histone modification,chromatin remodeling,non-coding RNAs,and RNA modification,which will facilitate applications such as HSC ex vivo expansion and exploration of novel therapeutic approaches for many hematological diseases.

关键词： Epigenetics Hematopoietic stem cells Homeostasis

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Chemical tools for E3 ubiquitin ligase study

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Chinese Chemical Letters 2023年第4期34卷 67-74页

作者： Yangwode Jing Chong Zuo Yun-Xiang Du Junxiong Mao Ruichao Ding jiachen Zhang Lu-Jun Liang qian Qu Institute of Translational Medicine Shanghai Jiao Tong UniversityShanghai 200240China Tsinghua-Peking Center for Life Sciences Ministry of Education Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical BiologyCenter for Synthetic and Systems BiologyDepartment of ChemistryTsinghua UniversityBeijing 100084China

E3 ubiquitin ligases catalyze the final step of ubiquitylation,a crucial post-translational modification involved in almost every process in eukaryotic cells.E3 ubiquitin ligases are key regulators of cellular events,and the investigation into their functions and functioning mechanisms are research areas with great importance.Synthetic or semi-synthetic tools have greatly facilitated the research about the enzyme activity,distribution in different physiological events,and catalytic mechanism of E3 ubiquitin ligase.In this review,we summarize the development of chemical tools for E3 ubiquitin ligases with an emphasis on the synthetic routes.We show the utility of these chemical tools by briefly discussing their applications in biological research.

关键词： Chemical tools Protein chemical synthesis Ubiquitylation E3 ligase Enzymatic mechanism

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再论煤炭的科学开采

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煤炭学报 2018年第1期43卷 1-13页

作者：钱鸣高许家林王家臣中国矿业大学(北京) 北京100083 中国矿业大学江苏徐州221116 煤炭资源与安全开采国家重点实验室江苏徐州221116

科学采矿是指在保证安全的前提下、在环境容量的允许范围内,经济、高效、高采出率地采出煤炭。从人与自然相处的三大学问"获取—使用—回归"出发,再次明确了科学采矿的内涵与框架。综述了科学采矿理念指导下我国煤炭行业所取得的各项进... 详细信息

科学采矿是指在保证安全的前提下、在环境容量的允许范围内,经济、高效、高采出率地采出煤炭。从人与自然相处的三大学问"获取—使用—回归"出发,再次明确了科学采矿的内涵与框架。综述了科学采矿理念指导下我国煤炭行业所取得的各项进展,分析了新形势下科学采矿面临的若干问题,并再次阐明了发展科学采矿的必要性。在此基础上,提出了全面实现科学采矿的条件,重点应从制定新建矿井准入标准、制定落后产能退出标准、分步实现科学产能以及加强行业协调和政策法规完善等方面做好煤炭科学开采的顶层设计,同时还要加强煤炭资源经济规律研究、加大科技投入和技术攻关以及改革人才培养模式。对煤炭的科学开采和煤炭行业的健康发展提出了方向性的意见。

关键词：科学采矿安全高效绿色开采资源经济科学产能

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带惩罚的相同容量k-均值问题的局部搜索算法

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运筹学学报 2022年第1期26卷 113-124页

作者：剧嘉琛刘茜张昭周洋北京工业大学数学学院运筹学与信息工程系山东师范大学数学与统计学院浙江师范大学数学与计算机科学学院

经典k-均值问题是一类应用广泛的聚类问题,它是指给定R^(d)中观测点集合D和整数k,目的是在空间中寻找k个点作为中心集合S,使得集合D中的每个观测点到S中离它最近的中心的距离平方求和最小。这是个NP-难问题。经典k-均值问题有很多推广,... 详细信息

经典k-均值问题是一类应用广泛的聚类问题,它是指给定R^(d)中观测点集合D和整数k,目的是在空间中寻找k个点作为中心集合S,使得集合D中的每个观测点到S中离它最近的中心的距离平方求和最小。这是个NP-难问题。经典k-均值问题有很多推广,本文研究的带惩罚的相同容量k-均值问题就是其中之一。与经典k-均值问题相比,惩罚性质是指每个观测点都给定惩罚费用,当某个观测点到最近中心的距离大于惩罚费用时,其对目标函数的贡献就用该观测点的惩罚费用来代替最近的距离的平方,相同容量约束要求每个中心至多连接U个观测点。针对这种问题,我们设计了局部搜索算法,该算法在至多选取(3+α)k个中心的情况下,可以达到β-近似,其中,参数α>34,β>α+34/α-34。

关键词： k-均值问题惩罚相同容量双准则局部搜索近似算法

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“Towards Re-Inventing Psychohistory”:Predicting the Popularity of Tomorrow’s News from Yesterday’s Twitter and News Feeds

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Journal of Systems Science and Systems Engineering 2021年第1期30卷 85-104页

作者： jiachen Sun Peter Gloor MIT Center for Collective Intelligence 245 First StreetCambridgeMA02142USA School of Electronics and Information Technology Sun Yat-Sen UniversityGuangzhou510275China

Rapid advances in machine learning combined with wide availability of online social media have created considerable research activity in predicting what might be the news of tomorrow based on an analysis of the past.In this work,we present a deep learning forecasting framework which is capable to predict tomorrow’s news topics on Twitter and news feeds based on yesterday’s content and topic-interaction features.The proposed framework starts by generating topics from words using word embeddings and K-means clustering.Then temporal topic-networks are constructed where two topics are linked if the same user has worked on both topics.Structural and dynamic metrics calculated from networks along with content features and past activity,are used as input of a long short-term memory(LSTM)model,which predicts the number of mentions of a specific topic on the subsequent day.Utilizing dependencies among topics,our experiments on two Twitter datasets and the HuffPost news dataset demonstrate that selecting a topic’s historical local neighbors in the topic-network as extra features greatly improves the prediction accuracy and outperforms existing baselines.

关键词： Topic’s popularity trend forecasting social media

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一种改进YOLOv5的多尺度像素林火识别算法

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林业工程学报 2023年第2期8卷 159-165页

作者：王寅凯曹磊钱佳晨林海峰南京林业大学信息科学技术学院南京210037

林火破坏程度大、蔓延速度快的特点给森林生态环境和人类带来极大的危害。深度学习技术可以学习和自适应提取林火特征,捕获的林火图像中火焰的像素尺寸不同,林火提取的特征也不同。为了能够识别复杂背景下不同像素尺度的火灾,笔者提出... 详细信息

林火破坏程度大、蔓延速度快的特点给森林生态环境和人类带来极大的危害。深度学习技术可以学习和自适应提取林火特征,捕获的林火图像中火焰的像素尺寸不同,林火提取的特征也不同。为了能够识别复杂背景下不同像素尺度的火灾,笔者提出了一种改进的YOLOv5林火识别方法,通过在YOLOv5的检测网络加入解耦头,解决林火图像输出变量时分类和回归的冲突问题,加快网络收敛速度提高识别精度;在网络中引进CBAM注意力机制,更关注林火信息同时提升识别精度;在Neck网络引入加权双向特征金字塔网络(BiFPN),替换原有的路径聚合网络(PANet),对不同维度的林火特征进行融合,进行特征筛选,增强特征表示能力。实验结果表明,该林火识别算法在自制的林火数据集上进行训练和验证模型,检测性能上均优于YOLOv5算法,在准确率、召回率、平均精度分别提升了5.2%,3.0%,3.4%,mAP@.5:.95提升了4.6%,并且在不同尺寸林火目标的识别精度上均有提升。研究结果对林火识别性能提升有着积极意义。

关键词：林火识别改进YOLOv5 解耦头深度学习

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Single-source precursor derived high-entropy metal–carbide nanowires:Microstructure and growth evolution

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Journal of Advanced Ceramics 2023年第11期12卷 2041-2052页

作者： Junhao Zhao Yulei Zhang Hui Chen Yanqin Fu Qing Miao jiachen Meng jiachen Li Shaanxi Key Laboratory of Fiber Reinforced Light Composite Materials Northwestern Polytechnical UniversityXi’an 710072China Henan Key Laboratory of High Performance Carbon Fiber Reinforced Composites Institute of Carbon Matrix CompositesHenan Academy of SciencesZhengzhou 450046China

In recent years,high-entropy metal carbides(HECs)have attracted significant attention due to their exceptional physical and chemical properties.The combination of excellent performance exhibited by bulk HEC ceramics and distinctive geometric characteristics has paved the way for the emergence of one-dimensional(1D)HECs as novel materials with unique development potential.Herein,we successfully fabricated novel(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C nanowires derived via Fe-assisted single-sourced precursor pyrolysis.Prior to the synthesis of the nanowires,the composition and microstructure of(Ti,Zr,Hf,Nb,Ta)-containing precursor(PHECs)were analyzed,and divinylbenzene(DVB)was used to accelerate the conversion process of the precursor and contribute to the formation of HECs,which also provided a partial carbon source for the nanowire growth.Additionally,multi-branched,single-branched,and single-branched bending nanowires were synthesized by adjusting the ratio of PHECs to DVB.The obtained single-branched(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C nanowires possessed smooth surfaces with an average diameter of 130–150 nm and a length of several tens of micrometers,which were a single-crystal structure and typically grew along the[11¯1]direction.Also,the growth of the(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C nanowires was in agreement with top-type vapor–liquid–solid mechanism.This work not only successfully achieved the fabrication of HEC nanowires by a catalyst-assisted polymer pyrolysis,but also provided a comprehensive analysis of the factors affecting their yield and morphology,highlighting the potential application of these attractive nano-materials.

关键词： (Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C nanowires high-entropy metal carbides(HECs) (Ti,Zr,Hf,Nb,Ta)-containing precursors vapor–liquid–solid(VLS)mechanism

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