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Near-field wideband beam training for ELAA with uniform circular array

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Science China(Information Sciences) 2024年第6期67卷 370-383页

作者： Yuhao CHEN linglong DAI Department of Electronic Engineering Tsinghua UniversityBeijing National Research Center for Information Science and Technology (BNRist)

Extremely large-scale antenna array(ELAA) at millimeter wave(mmWave) and Terahertz(THz)band has been considered a key technology for combating high attenuation in high-frequency bands in future6G communications. Uniform circular arrays(UCAs) have attracted much attention because of their ability to provide flat beamforming gain at all angles. To realize efficient beamforming, beam training is widely used to acquire channel state information. However, with a large antenna number, the beam training overhead in ELAA systems becomes overwhelming. Moreover, with a large bandwidth, the beam defocus effect severely degrades beam training accuracy. To address these issues, this paper proposes a frequency-dependent focusing(FDF)-based beam training scheme to realize effective beam training in near-field wideband ELAA systems with UCA. Specifically, we first analyze the FDF property of UCA, where signals at different subcarriers can simultaneously focus on different distances. Then, by exploiting the FDF property to search different distances using different subcarriers simultaneously, we design a hierarchical codebook and propose an FDFbased beam training scheme. To reveal the effectiveness of the proposed scheme, we compare its necessary beam training overhead with that of existing schemes. Finally, the simulation results demonstrate that the proposed scheme can achieve accurate beam training in near-field wideband UCA systems with a low beam training overhead.

关键词： extremely large-scale antenna array (ELAA) uniform circular array (UCA) near-field wideband beam training

Activity of Brucea javanica oil emulsion against gastric ulcers in rodents

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Asian Journal of Pharmaceutical Sciences 2018年第3期13卷 279-288页

作者： Qian Li linglong yang Linlin Fan Chen Liang Qiujv Wang Huimin Wen Jinwei Dai Xin Li Yuyang Zhang School of Life Science and Biopharmaceutics Shenyang Pharmaceutical University

The present study aims to investigate the gastroprotective effect of Brucea javanica oil emulsion(BJOE) in animals. Gastroprotective potential of BJOE was studied on absolute ethanol,aspirin, reserpine and restraint plus water immersion-induced gastric ulcers in mice as well as glacial acetic acid(GAA) and pyloric ligation(PL)-induced gastric ulcers in rats. Except for ulcer scores, total acidity as well as pepsin activity as for the PL-induced gastric ulcer model and ulcer incidence as for the GAA-induced gastric ulcer model were also determined. Histopathological evaluation as for aspirin, reserpine, PL-induced models was conducted. Results showed that BJOE significantly(P < 0.05) reduced ulcer index in the mouse and rat models in a dose-dependent manner. It had significant(P < 0.05) suppressive effect on total activity of gastric juice as well in PL-induced model. Histopathological examination for the stomach samples confirmed the findings in the aspirin, reserpine or PLinduced gastric lesion models, which showed relatively complete mucosa structure and less inflammation. It is concluded that BJOE could be effective on gastric ulcer in rodents and its gastroprotective activity might be related to antioxidant, anti-inflammatory ability and promote gastric mucus secreted. The results may provide beneficial basis for increasing BJOE's clinical indication in future.

关键词： Gastric ulcer Brucea javanica oil emulsion Gastric mucosa Ulcer scores Glacial acetic acid Pepsin activity

复合型非致命动能弹冲击能量耗散特性数值模拟

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火力与指挥控制 2024年第2期49卷 26-32页

作者：孙映斌汪送乔玲龙武警工程大学研究生大队西安710086 武警工程大学装备管理与保障学院西安710086 武警工程大学军事基础教育学院西安710086

非致命动能弹药应用广泛,传统型非致命动能弹常常发生过度伤害的问题,研发新一代兼具安全性和有效性的复合型非致命动能弹很有必要。为了揭示复合型非致命动能弹致伤机理,评估其对人体的冲击损伤,通过数值模拟的方法,比较传统型非致命... 详细信息

非致命动能弹药应用广泛,传统型非致命动能弹常常发生过度伤害的问题,研发新一代兼具安全性和有效性的复合型非致命动能弹很有必要。为了揭示复合型非致命动能弹致伤机理,评估其对人体的冲击损伤,通过数值模拟的方法,比较传统型非致命动能弹与复合型非致命动能弹以相同速度冲击靶标以及复合型非致命动能弹以不同速度冲击靶标所获得的数据,深入分析复合型非致命动能弹冲击能量耗散特性,为我国自主研发新一代非致命动能弹药提供一定参考。

关键词：非致命动能弹复合型能量耗散数值模拟

昭通巧家烂泥箐滑坡滑带土特征及滑坡发生机制研究

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自然灾害学报 2024年第2期33卷 87-97页

作者：陈云英徐宗恒张宇查玲珑云南师范大学地理学部云南昆明650500 云南省高原地理过程与环境变化重点实验室云南昆明650500

滑带土是滑坡发展过程的产物,对滑坡的孕育和演化过程具有良好的记录作用。以昭通巧家小河镇烂泥箐滑坡为研究对象,用野外地质调查及室内试验的方法,详细阐述了该滑坡滑带土的物理-水理-力学特征,同时结合XRD衍射分析矿物成分和SEM微结... 详细信息

滑带土是滑坡发展过程的产物,对滑坡的孕育和演化过程具有良好的记录作用。以昭通巧家小河镇烂泥箐滑坡为研究对象,用野外地质调查及室内试验的方法,详细阐述了该滑坡滑带土的物理-水理-力学特征,同时结合XRD衍射分析矿物成分和SEM微结构观察的手段,从多角度分析了烂泥箐滑坡滑带土的特征,揭示了烂泥箐滑坡的形成演变过程及驱动机制。结果表明:烂泥箐滑坡滑带土含有较多黏土矿物,具有黏粒含量多、质地细的特点,呈现出明显的黏性土特性。烂泥箐滑坡滑带土的细粒含量明显比受滑动扰动小的滑床土多,表明在滑坡孕育过程中滑带内发生了多次滑移剪切错动。不同含水率条件下滑带土快剪试验表明,滑带土具有明显的应变硬化特征,随着含水率增加,抗剪强度逐渐降低,特别是含水率为40%时,滑带土强度损失很大,软化明显;低含水率时,黏聚力和内摩擦角均较高,随着含水率增加,黏聚力和内摩擦角均逐渐减小。试验结果表明降雨条件下滑带土随着含水率增加表现出明显“软黏土”特征。由于斜坡受后缘Y093乡道的改扩建、后缘行车荷载的长期作用及斜坡中部烂泥箐村庄小路的改扩建工程的长期扰动,坡体内部逐渐发生变形,发展孕育了潜在滑面及该滑动面上的多期蠕动变形,多次的剪切滑动使滑带土内黏粒含量增多,质地更细。而受其黏性土材料特性的影响,低渗透率的滑动带在降雨作用下易形成隔水屏障。加之降雨条件下滑带土强度快速软化降低,剪切带内形成的静水压力和局部隔水屏障形成的超孔隙水压力直接触发了烂泥箐滑坡的发生。利用烂泥箐滑坡的发生机制可以探讨其孕育-激发过程的3个阶段:滑带区初步形成阶段、滑带演化阶段、滑带土软化以及滞水层-滑坡形成阶段。研究成果可为山区降雨型滑坡的系统研究提供一定的借鉴价值。

关键词：烂泥箐滑坡滑带土物理力学特征发生机制演化过程

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基于PLC的井下制氮装置集中监控系统设计

煤矿机电 2024年第1期45卷 37-41页

作者：王灵龙中煤科工集团沈阳研究院有限公司辽宁抚顺113122 煤矿安全技术国家重点实验室辽宁抚顺113122

井下制氮装置是煤矿防灭火的重要设备,在煤矿智能化快速建设下,多台井下制氮装置面临着无法集中监控、查询记录、查看报表等困难,设计了一种基于PLC的井下制氮装置集中监控系统,对井下制氮装置结构组成、控制原理进行阐述,逐步进行了集... 详细信息

井下制氮装置是煤矿防灭火的重要设备,在煤矿智能化快速建设下,多台井下制氮装置面临着无法集中监控、查询记录、查看报表等困难,设计了一种基于PLC的井下制氮装置集中监控系统,对井下制氮装置结构组成、控制原理进行阐述,逐步进行了集中监控系统的总体方案设计、硬件设计、软件设计。现场试验表明,系统实现了操作台集中监控井下多台制氮装置,有效降低现场监管设备人员成本,减少误操作导致的事故发生,同时提高自动化管控水平。

关键词：制氮装置 PLC控制器集中监控操作台 Modbus通信

农文旅融合发展模式推动农民精神生活共同富裕的路径探析

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武汉纺织大学学报 2024年第1期37卷 107-112页

作者：常沛吴玲龙武汉纺织大学马克思主义学院湖北武汉430073

党的二十大报告指出,中国式现代化的本质要求之一是“丰富人民精神世界”。农文旅融合发展模式不仅是推动乡村振兴的重要引擎,更是实现农民精神生活共同富裕的基本途径。马克思主义人学理论从物质前提、现实需求、价值旨归等方面丰富了... 详细信息

党的二十大报告指出,中国式现代化的本质要求之一是“丰富人民精神世界”。农文旅融合发展模式不仅是推动乡村振兴的重要引擎,更是实现农民精神生活共同富裕的基本途径。马克思主义人学理论从物质前提、现实需求、价值旨归等方面丰富了农文旅融合发展模式下推动农民精神生活共同富裕的理论意涵。农文旅融合发展模式不仅可以协调物质富裕与精神富有的关系,而且能够激发农民精神生活共同富裕的内生动力。在实践路径上,可以通过夯实物质基础,促进乡村新产业新业态发展;坚持党建引领,共建共享美好精神家园;加强文旅融合,创造性转化创新性发展乡村文化;坚持价值引领,铸就乡村精神文明高地等来实现。

关键词：农民精神生活共同富裕农文旅

Near-field wideband channel estimation for extremely large-scale MIMO

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Science China(Information Sciences) 2023年第7期66卷 283-296页

作者： Mingyao CUI linglong DAI Department of Electronic Engineering Tsinghua University Beijing National Research Center for Information Science and Technology(BNRist)

Extremely large-scale multiple-input-multiple-output(XL-MIMO) at millimeter-wave(mm Wave)and terahertz(THz) bands plays an important role in supporting extreme high beamforming gain as well as ultra-wideband spectrum resources. Unfortunately, accurate wideband XL-MIMO channel estimation suffers from a new challenge called the near-field beam split effect. Prior studies either neglect the accurate nearfield channel model or fail to exploit the beam split effect, resulting in poor channel estimation accuracy for wideband XL-MIMO. To tackle this problem, this paper proposes a bilinear pattern detection(BPD)-based approach to accurately recover the wideband XL-MIMO channel. Specifically, by analyzing the characteristics of near-field wideband channels, we first reveal the bilinear pattern of the near-field beam split effect, which implies that the sparse support set of near-field channels in both the angle and the distance domains can be regarded as a linear function against frequency. Then, inspired by the classical simultaneously orthogonal matching pursuit technique, we use the bilinear pattern to estimate the angle-of-arrival(Ao A) and distance parameters of each near-field path component at all frequencies. In this way, the entire wideband XL-MIMO channel can be recovered by compressed sensing algorithms. Moreover, we provide the computational complexity of the proposed algorithm compared with existing algorithms. Finally, simulation results demonstrate that our scheme can achieve the accurate estimation of the near-field wideband XL-MIMO channel in the presence of near-field beam split effect.

关键词： XL-MIMO wideband near-field beam split channel estimation

Reconfigurable Intelligent Surfaces for 6G:Nine Fundamental Issues and One Critical Problem

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Tsinghua Science and Technology 2023年第5期28卷 929-939页

作者： Zijian Zhang linglong Dai Department of Electronic Engineering Tsinghua Universityand also with Beijing National Research Center for Information Science and Technology(BNRist)Beijing 100084China

Thanks to the recent advances in metamaterials,Reconfigurable Intelligent Surface(RIS)has emergedas a promising technology for future 6G wireless communications.Benefiting from its high array gain,low cost,and low power consumption,RISs are expected to greatly enlarge signal coverage,improve system capacity,andincrease energy efficiency.In this article,we systematically overview the emerging RIS technology with the focuson its key basics,nine fundamental issues,and one critical problem.Specifically,we first explain the RIS basics,including its working principles,hardware structures,and potential benefits for communications.Based on thesebasics,nine fundamental issues of RISs,such as“What’s the differences between RISs and massive MIMO?”and“Is RIS really intelligent?”,are explicitly addressed to elaborate its technical features,distinguish it from existingtechnologies,and clarify some misunderstandings in the literature.Then,one critical problem of RISs is revealedthat,due to the“multiplicative fading”effect,existing passive RISs can hardly achieve visible performance gains inmany communication scenarios with strong direct links.To address this critical problem,a potential solution calledactive RISs is introduced,and its effectiveness is demonstrated by numerical simulations.

关键词： Reconfigurable Intelligent Surface(RIS) sixth generation mobile system(6G) wireless communications

展开式变体垂直起降飞行器气动布局与控制策略设计及飞行验证

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航空学报 2024年第6期45卷 149-166页

作者：陈其昌史志伟张维源姚灵珑童晟翔南京航空航天大学航空学院南京210016

垂直起降飞行器具有固定翼飞行器飞行航程远、飞行速度快的性能优势,又同旋翼飞行器一样机动灵活,具有垂直起降的功能,近年来成为飞行器研究领域的研究热点之一。尤其是尾座式垂直起降飞行器由于其结构简单、重量利用率高等优点,受到了... 详细信息

垂直起降飞行器具有固定翼飞行器飞行航程远、飞行速度快的性能优势,又同旋翼飞行器一样机动灵活,具有垂直起降的功能,近年来成为飞行器研究领域的研究热点之一。尤其是尾座式垂直起降飞行器由于其结构简单、重量利用率高等优点,受到了较多关注。本文提出了一种机翼可展开的尾座式变体垂直起降飞行器总体布局方案,为该布局设计了一种具有自锁功能的机翼变体驱动机构。利用风洞测力实验对飞行器固定翼巡航模态、四旋翼悬停模态及变体过渡过程的气动力进行研究,给出了飞行器在固定翼巡航模态下的配平能力与飞行性能,及前倾加速及变体过渡过程中的气动特性。并提出了一种升降副翼-旋翼协调航向增强控制策略,有效提升飞行器悬停模态的航向控制力矩。通过对飞行器变体转换过程的受力情况研究,为该构型飞行器设计了一种基于空速与俯仰姿态角的变体过渡控制策略。对该构型飞行器进行了飞行试验验证,结果表明飞行器在四旋翼悬停和固定翼巡航模态下表现出良好的操纵性和抗风能力,成功实现了平稳的无高度损失模态转换,验证了控制策略的有效性。

关键词：变体机翼展开尾座式垂直起降风洞实验控制策略飞行验证