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Flexible and densified graphene/waterborne polyurethane composite film with thermal conducting property for high performance electromagnetic interference shielding

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Nano Research 2022年第11期15卷 9926-9935页

作者： Wang Yang Hengxuan Bai Bo Jiang Chaonan Wang Weimin Ye Zhengxuan Li Chong Xu Xiaobai Wang Yongfeng li State Key Laboratory of Heavy Oil Processing China University of PetroleumBeijing 102249China Department of Materials Application Research AVIC Manufacturing Technology InstituteBeijing 100024China

High-performance electromagnetic interference(EMI)shielding materials with flexibility,excellent mechanical property,and thermal conductivity are highly desired for fifth-generation communications devices.Graphene exhibits tremendous potential due to its high electrical conductivity and unique lamellar structure.However,the construction of densified graphene structure in polymer matrix is still challenging.Herein,we develop a graphene/waterborne polyurethane(G/WPU)flexible film with densified and ordered layer-structure for using as an EMI shielding material.By virtue of the polyvinylpyrrolidone modified strategy and facile liquid phase ball-milling treatment,the graphene nanosheets can be efficiently dispersed into the WPU substrate and tightly connected between each other via internal interactions.Benefiting from the relatively low defects and densified structure of graphene,the resultant G/WPU film yields a high electrical conductivity of 1,004.5 S/m,and a tensile strength of around 48.5 MPa.As a consequence,it achieves an average EMI shielding effectiveness of over 30 dB in the X-band with a thickness of merely 0.15 mm and the value is further enhanced to 73.4 dB at 0.9 mm with a low density of 1.4 g/cm^(3),offering over 99.99999%shielding of incident electromagnetic waves.More importantly,this G/WPU film also exhibits a high cross-plane thermal conductivity of about 1.13 W/(m·K).Thus,this work develops a high-performance EMI shielding material with both good capacity of heat transmission,but also provides a facile strategy for designing next-generation advanced,lightweight,flexible,and multifunction shielding materials.

关键词： electromagnetic interference shielding graphene densification flexible thermal conductivity

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Magnetic coupling engineered porous dielectric carbon within ultralow filler loading toward tunable and high-performance microwave absorption

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Journal of Materials Science & Technology 2021年第11期70卷 214-223页

作者： Wang Yang Bo Jiang Zhihui liu Rui li liqiang Hou Zhengxuan Li Yongli Duan Xingru Yan Fan Yang Yongfeng li State Key Laboratory of Heavy Oil Processing China University of Petroleum(Beijing)Changping 102249China

Developing microwave absorption(MA)materials with satisfied comprehensive performance is a great challenge for tackling severe electromagnetic pollution.In particular,the magnetic component/carbon hybrids absorbers always suffer from high filler loading.Herein,we propose a feasible strategy to construct hierarchical porous carbon with tightly embedded Ni nanoparticles(Ni@NPC).These highly dispersed Ni nanoparticles produce strong magnetic coupling networks to enhance magnetic loss abilities.Moreover,the interconnected hierarchical dielectric carbon network affords favorable dipolar/interfacial polarization,conduction loss,multiple reflection and scattering.Impressively,with an ultralow filler loading of 5 wt.%,the resultant Ni@NPC/paraffin composite achieves an excellent MA performance with a minimum reflection loss of as high as-72.4 dB and a broad absorption bandwidth of 5.0 GHz.This capability outperforms most current magnetic-dielectric hybrids counterparts.Furthermore,the MA capacity can be easily tuned with adjustments in thickness,content and type of magnetic material.Thus,this work opens up new avenues for the development of high-performance and lightweight MA materials.

关键词： Hierarchical porous carbon Magnetic nanoparticles Magnetic coupling Ultralow filler loading High-performance microwave absorption

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A CSI Acquisition Approach for mm Wave Massive MIMO

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China Communications 2019年第9期16卷 1-14页

作者： Shanzhi Chen Qiubin Gao Runhua Chen Hui li Shaohui Sun Zhengxuan Liu State Key Lab of Wireless Mobile Communication China Academy of Telecommunication Technology

Massive Multiple-Input Multiple-Output(MIMO)is considered as a key technology for 4G and 5G wireless communication systems to improve spectrum efficiency by supporting large number of concurrent users.In addition,for the target frequency band of 5G system,mmWave band,massive MIMO is pivotal in compensating the high pathloss.In this paper,we investigate the channel state information(CSI)acquisition problem for mmWave massive MIMO.With hybrid analog-digital antenna architecture,how to derive the analog beamforming and digital beamforming is studied.An iterative analog beam acquisition approach is proposed to save system overhead and reduce beam searching complexity.Regarding the digital beamforming,a grouping based codebook is proposed to facilitate CSI feedback.The codebook is then extended to incorporate also analog beam acquisition.Furthermore,channel reciprocity is exploited to save CSI reporting overhead and a two-stage approach is proposed to fully utilize the channel reciprocity at both mobile station and base station side and accelerate the CSI acquisition procedure.

关键词： codebook CSI acquisition hybridbeamforming

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Key technologies and system proposals of TWDM-PON

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Frontiers of Optoelectronics 2013年第1期6卷 46-56页

作者： Zhengxuan Li lilin YI Weisheng HU The State Key Lab of Advanced Optical Communication Systems and Networks Department of Electronic Engineering Shanghai Jiao Tong University Shanghai 200240 China

In this paper, key technologies, system proposals and future directions of next generation passive optical networks stage 2 (NG-PON2) are reviewed. We first discuss the potential solutions for NG-PON2 standardization. Then we focus on time and wavelength division multiplexed PON (TWDM-PON), which is the primary solution selected by Full Service Access Network (FSAN). The key technologies in TWDM-PON configuration are analyzed, including how to improve the bandwidth capacity and power budget of the system, and choose upstream tunable transceiver, etc. Several system proposals are illustrated as candidates for NG-PON2 configuration.

关键词： next generation passive optical networks stage 2 (NG-PON2) time and wavelength division multiplexed PON (TWDM-PON) tunable transmitter tunable receiver power budget

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网络越轨行为治理困境与对策研究

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网络空间安全 2023年第5期14卷 104-110页

作者：李政轩中国人民公安大学

[目的/意义]随着经济社会持续发展，网络技术极大地丰富了人们的日常生活。但是，由于精神世界的空虚和制度规范的滞后等因素，导致文化堕距形成，并由此不断诱发出网络越轨行为，成为当下网络空间治理无法回避的问题。[方法/过程]通过... 详细信息

[目的/意义]随着经济社会持续发展，网络技术极大地丰富了人们的日常生活。但是，由于精神世界的空虚和制度规范的滞后等因素，导致文化堕距形成，并由此不断诱发出网络越轨行为，成为当下网络空间治理无法回避的问题。[方法/过程]通过对网络越轨行为进行分析，网络越轨行为包括悖德行为、网络一般违法行为和网络犯罪行为。根据文化堕距理论，目前仍存在“网络空间的治理规范不足”“物质文化的发展引发结构性紧张”“信息技术使用能力有待提升”的治理困境。[结果/结论]需要从“加快网络空间法治化”“回归社会源头治理”和“深化公安技术治网水平”方面缩小文化堕距，实现网络越轨行为的治理。

关键词：文化堕距网络空间越轨治理犯罪预防

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How social stress and oxytocin influence the way people update their belief?

How social stress and oxytocin influence the way people upda...

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第二十一届全国心理学学术会议

作者： Wenying Yuan Xinyuan Yan Ingrid Huang Di Wu Zhengxuan Li Yina Ma State Key Laboratory of Cognitive Neuroscience and Learning IDG/McGovern Institute for Brain Research Beijing Normal University

Stress, a common experience in daily life, has both health risks and benefits. While prolonged stress has been linked with impaired immunity and higher risk for depression and anxiety disorders, stress has been recognized as potentially adaptive in the regulation of our immunity and cognitive performance. Social evaluation can serve as social support to protect individuals from stress but can also intensify stress. However, it remains unknown how acute social stress influences the processing of social feedback. Here, combining a two-stage belief update paradigm and a social evaluative stress paradigm, we examine whether and how acute social stress and intranasal administration of oxytocin influence individual’s belief update upon desirable and undesirable social feedback. We found that participants’ heart rate and cortisol level were significantly increased after experiencing stress. Moreover, oxytocin decreased participants’ cortisol response to social stress. We further showed that oxytocin administration under stress led to the most optimistic-oriented belief updating pattern, suggesting an interactive effect of social stress and oxytocin on optimistic beliefs. Moreover, this interactive effect was mainly found for belief updating selectively upon desirable feedback but not upon undesirable feedback. Social stress and oxytocin treatment facilitate optimistic belief updating. Supporting the protective hypothesis, individuals experiencing and given oxytocin treatment exhibit the highest level of optimism.

关键词： Oxytocin Social stress Belief update optimism

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Local path planning of autonomous vehicles based on A* algorithm with equal-step sampling

Local path planning of autonomous vehicles based on A* algor...

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第37届中国控制会议

作者： WANG Yijing liU zhengxuan ZUO Zhiqiang li Zheng Tianjin Key Laboratory of Process Measurement and Control School of Electrical and Information Engineering Tianjin University

Path planning is an important component in the study of autonomous vehicles. And local path planning is a pivotal issue, which will greatly influence the safety and comfort of the vehicle. On the premise of security, this paper proposes a novel A* algorithm with equal-step sampling based on vehicle kinematics model to improve the comfort of the path as much as possible. The algorithm is based on vehicle kinematics and introduces an enhanced cost function. The simulation results illustrate the feasibility of this approach on lane-keep and obstacle avoidance in different scenarios. In addition, the real vehicle test results of "Smart Driving" autonomous vehicle of Tianjin University demonstrate the capability of real-time implementation.

关键词： Autonomous vehicles Local path planning Vehicle kinematics model Equal-step sampling

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基于WDM-PON架构的5G前传系统中的FWM效应

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应用科学学报 2022年第5期40卷 749-757页

作者：于培华李正璇许岩宋英雄上海大学通信与信息工程学院上海200444 上海大学特种光纤与光接入网重点实验室上海200444

为了应对快速增长的带宽需求,解决非线性效应限制波分复用无源光网络(wavelength-division multiplexing passive optical network,WDM-PON)系统的传输距离和信道容量,尤其是四波混频(four-wave mixing,FWM)效应的问题。通过实验与仿真... 详细信息

为了应对快速增长的带宽需求,解决非线性效应限制波分复用无源光网络(wavelength-division multiplexing passive optical network,WDM-PON)系统的传输距离和信道容量,尤其是四波混频(four-wave mixing,FWM)效应的问题。通过实验与仿真研究了25 Gb·s·λ非归零码(non-return-to-zero,NRZ)信号经过25 km标准单模光纤(standard single-mode fiber,SSMF)传输时,FWM效应对系统所产生的影响。仿真结果表明,在信道间隔为200 GHz的12个波长传输系统中,除了第一个和最后一个信道之外,其他信道误码率(bit error rate,BER)都不能达到前向纠错码(forward error correction,FEC)的门限1.0×10。因此,在制定5G前传系统波长分布和信道间隔时,应充分考虑FWM串扰。

关键词： 5G前传波分复用无源光网络非线性效应四波混频

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锻压条件对高强建筑Al-11.5Si-2Cu-0.5Fe铝合金显微组织的影响

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锻压技术 2024年第5期49卷 13-16+83页

作者：郭正烜李子亮山西工程科技职业大学建筑设计学院河北科技大学材料科学与工程学院

为研究不同锻压条件对近共晶Al-Si合金Al-11.5Si-2Cu-0.5Fe显微组织的影响，在300、400和500℃锻压温度以及1.5和2.0锻压比下，通过收敛模具对Al-11.5Si-2Cu-0.5Fe铝合金进行锻压，并采用光学显微镜和X射线衍射仪对铝合金的显微组织及... 详细信息

为研究不同锻压条件对近共晶Al-Si合金Al-11.5Si-2Cu-0.5Fe显微组织的影响，在300、400和500℃锻压温度以及1.5和2.0锻压比下，通过收敛模具对Al-11.5Si-2Cu-0.5Fe铝合金进行锻压，并采用光学显微镜和X射线衍射仪对铝合金的显微组织及析出相进行观察。实验结果表明：铸造态的Al-11.5Si-2Cu-0.5Fe铝合金形成了多种复杂的金属间化合物相，如β-Al4.5FeSi相和Al2Cu相。在锻压过程中Al-11.5Si-2Cu-0.5Fe铝合金的显微组织显著细化，同时，粗大颗粒发生破裂和碎片化。随着锻压温度的升高，Si颗粒长大，晶粒细化减弱；随着锻压比的增加，Si颗粒破碎加剧，晶粒细化更明显。300℃锻压温度、2.0锻压比下可以获得最佳细化效果。可为Al-11.5Si-2Cu-0.5Fe铝合金实际锻造生产过程中显微组织的变化提供理论基础。

关键词： Al-11.5Si-2Cu-0.5Fe铝合金锻压温度锻压比显微组织 Si颗粒尺寸

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枳实改善功能性消化不良大鼠胃动力障碍的机制研究

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陕西中医 2018年第8期39卷 998-1000页

作者：张正选李鲜河南省职工医院消化内科郑州450003 河南省中医院消化科郑州450000

目的:探讨枳实改善功能性消化不良大鼠胃动力障碍的机制。方法:取小鼠80只,随机分成观察组(枳实组)和对照组,每组各40例,观察组按1.07g/(kg·d)给药,对照组给予等体积的生理盐水,采用酶联免疫分析方法测定胃动素(MTL)及血管活性肠肽(VI... 详细信息

目的:探讨枳实改善功能性消化不良大鼠胃动力障碍的机制。方法:取小鼠80只,随机分成观察组(枳实组)和对照组,每组各40例,观察组按1.07g/(kg·d)给药,对照组给予等体积的生理盐水,采用酶联免疫分析方法测定胃动素(MTL)及血管活性肠肽(VIP),测定两组大鼠胃排空率、小肠推进比、胃残留率。结果:观察组大鼠血浆MTL含量明显高于正常对照组,差异有统计学意义(P<0.05);观察组大鼠血浆VIP含量明显低于正常对照组,差异有统计学意义(P<0.05)。观察组大鼠胃排空率、小肠推进比明显高于对照组大鼠,差异有统计学意义(P<0.05);观察组大鼠胃残留率明显少于对照组大鼠,差异有统计学意义(P<0.05)。结论:胃肠激素的改变可能是导致功能性消化不良大鼠胃动力障碍的主要发病机制之一,早期应用枳实对改善功能性消化不良大鼠胃动力障碍具有一定的积极作用。

关键词：消化不良/中医药疗法枳实/治疗应用动物实验小鼠血管活性肠肽

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