检索结果-南通市图书馆

Combination of diketone and PAO to achieve macroscale oil-based superlubricity at relative high contact pressures

在线全文

学校读者我要写书评

暂无评论

Friction 2024年第5期12卷 869-883页

作者： Shaonan DU Chenhui ZHANG Zhi LUO State key laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing100084China Beijing national laboratory of Molecular Sciences CAS Key Laboratory of Engineering PlasticsInstitute of ChemistryChinese Academy of SciencesBeijing100190China

1-(4-ethylphenyl)-nonane-1,3-dione(0206)is an oil-soluble liquid molecule with rod-like *** this study,the chelate(0206-Fe)with octahedral structure was prepared by the reaction of ferric chloride and 1,*** experimental results show that when using 0206 and a mixed solution containing 60%0206-Fe and 40%0206(0206-Fe(60%))as lubricants of the steel friction pairs,superlubricity can be achieved(0.007,0.006).But their wear scar diameters(WSD)were very large(532µm,370µm),which resulted in the pressure of only 44.3 and 61.8 MPa in the contact areas of the friction *** 0206-Fe(60%)was mixed with PAO6,it was found that the friction coefficient(COF)decreased with increase of 0206-Fe(60%)in the *** the ratio of 0206-Fe(60%)to PAO6 was 8:2(PAO6(20%)),it exhibited better comprehensive tribological properties(232.3 MPa).Subsequent studies have shown that reducing the viscosity of the base oil in the mixed solution helped to reduce COF and increased *** the COF,contact pressure,and running-in time,it was found that the mixed lubricant(Oil3(20%))prepared by the base oil with a viscosity of 19.7 mPa·s(Oil3)and 0206-Fe(60%)exhibited the best tribological properties(0.007,161.4 MPa,3,100 s).

关键词： diketone oil-based lubricants chelate superlubricity

Study on the tribological properties of metal rolling bearing under lubrication with diketone lubricants

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2024年第7期67卷 2003-2017页

作者： DU ShaoNan ZHANG ChenHui LUO Zhi State key laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing 100084China Beijing national laboratory of Molecular Sciences CAS Key Laboratory of Engineering PlasticsInstitute of ChemistryChinese Academy of SciencesBeijing 100190China

In this article, 1-(4-ethylphenyl)-nonane-1,3-dione(0206) was prepared by Claisen condensation. By mixing 0206, chelate, and base oil in a ratio of 3.2:4.8:2, a diketone lubricant(PAO=14(20%)) that can achieve superlubricity was prepared and applied to bearing lubrication experiments. The experimental results show that when the bearing was lubricated by base oil, the friction coefficient(COF) and temperature rise decreased with the decrease of the viscosity of PAO. When PAO=14(20%) was used as the lubricant, the COF of the bearing was the lowest(0.001), and the wear morphology was comparable to that of the bearing lubricated with commercial lubricant. Compared with the base oil with the same viscosity, it is found that the COF and temperature rise of the bearing lubricated by PAO=14(20%) were lower under any experimental conditions. And when the amount of lubricant added was 10 μL, the COF of the bearing lubricated by PAO=14(20%) reached a very low value(0.0004).Bearing ball surface analysis identified the formation of diketone adsorption films. Combined with the previous PAO=14(20%)superlubricity mechanism, it was considered that the occurrence of tribochemical reaction and the bearing effect of chelates were the main reasons for the existence of ultra-low friction coefficient and low wear. In addition, when there were polar molecules in the lubricant, they were adsorbed on the metal surface through tribochemical reactions, resulting in many irregular pits on the surface.

关键词： superlubricity diketone chelate tribochemical recations bearing lubrication

For LEO Satellite Networks: Intelligent Interference Sensing and Signal Reconstruction Based on Blind Separation Technology

在线全文

学校读者我要写书评

暂无评论

China communications 2024年第2期21卷 85-95页

作者： Chengjie Li Lidong Zhu Zhen Zhang The key laboratory for Computer Systems of State Ethnic Affairs Commission School of Computer Science and Technology(Southwest Minzu University)Chengdu 610000China national key laboratory of Science and Technology on communications(University of Electronic Science and Technology of China) Chengdu 610000China College of Computer Science(Sichuan University) Chengdu 610000China

In LEO satellite communication networks,the number of satellites has increased sharply, the relative velocity of satellites is very fast, then electronic signal aliasing occurs from time to time. Those aliasing signals make the receiving ability of the signal receiver worse, the signal processing ability weaker,and the anti-interference ability of the communication system lower. Aiming at the above problems, to save communication resources and improve communication efficiency, and considering the irregularity of interference signals, the underdetermined blind separation technology can effectively deal with the problem of interference sensing and signal reconstruction in this scenario. In order to improve the stability of source signal separation and the security of information transmission, a greedy optimization algorithm can be executed. At the same time, to improve network information transmission efficiency and prevent algorithms from getting trapped in local optima, delete low-energy points during each iteration process. Ultimately, simulation experiments validate that the algorithm presented in this paper enhances both the transmission efficiency of the network transmission system and the security of the communication system, achieving the process of interference sensing and signal reconstruction in the LEO satellite communication system.

关键词： blind source separation greedy optimization algorithm interference sensing LEO satellite communication networks signal reconstruction

The genetic basis and process of inbreeding depression in an elite hybrid rice

在线全文

学校读者我要写书评

暂无评论

Science China(Life Sciences) 2024年第8期67卷 1727-1738页

作者： Xiaodong Xu Yawen Xu Jian Che Xu Han Zhengji Wang Xianmeng Wang Qinghua Zhang Xu Li Qinglu Zhang Jinghua Xiao Xianghua Li Qifa Zhang Yidan Ouyang national key laboratory of Crop Genetic Improvement and national Centre of Plant Gene Research(Wuhan) Hubei Hongshan LaboratoryHuazhong Agricultural UniversityWuhan 430070China

Inbreeding depression refers to the reduced performance arising from increased homozygosity,a phenomenon that is the reverse of heterosis and exists among plants and *** a natural self-pollinated crop with strong heterosis,the mechanism of inbreeding depression in rice is largely *** understand the genetic basis of inbreeding depression,we constructed a successive inbreeding population from the F_(2)to F_(4)generation and observed inbreeding depression of all heterotic traits in the progeny along with the decay of heterozygosity in each *** expected depression effect was largely explained by 13 QTLs showing dominant effects for spikelets per panicle,11 for primary branches,and 12 for secondary branches,and these loci constitute the main correlation between heterosis and inbreeding ***,the genetic basis of inbreeding depression is also distinct from that of heterosis,such that a biased transmission ratio of alleles for QTLs with either dominant or additive effects in four segregation distortion regions would result in minor effects in expected ***,two-locus interactions may change the extent and direction of the depression effects of the target loci,and overall interactions would promote inbreeding depression among *** an F_(2:3)variation population,the actual performance of the loci showing expected depression was evaluated considering the heterozygosity decay in the background after *** found inconsistent or various degrees of background depression from the F_(2)to F_(3)generation assuming different genotypes of the target locus,which may affect the actual depression effect of the locus due to *** results suggest that the genetic architecture of inbreeding depression and heterosis is closely linked but also differs in their intrinsic mechanisms,which expand our understanding of the whole-genome architecture of inbreeding depression.

关键词： rice inbreeding depression spikelet development dominance segregation distortion epistasis

Surface integrity evolution during creep feed profile grinding ofγ-TiAl blade tenon

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第8期37卷 496-512页

作者： Tao CHEN Xiaowei WANG Biao ZHAO Wenfeng DING Jiuhua XU national key laboratory of Science and Technology on Helicopter Transmission Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Gamma titanium-aluminum(γ-TiAl)intermetallic compounds are increasingly used in manufacturing key hot-end components(e.g.,blade tenon)in aero engines due to their high specific strength and lightweight *** feed profile grinding(CFPG)as a crucial precision process that is applied to produce the final profile of the blade ***,sudden surface burns and microcracks of machined c-TiAl blade tenon often occur because of its low plasticity and high strength during grinding processes,leading to poor surface *** this work,CFPG experiments based on the profile characteristics ofγ-TiAl blade tenon were performed and an associated undeformed chip thickness model considering grain–workpiece contact condition was established to explore the evolution of the surface ***,the surface integrity was analyzed at different positions of the blade tenon in terms of surface roughness and morphology,metallographic structure,microhardness,and residual *** show that the profile characteristics of blade tenon have a significant influence on machined surface integrity because of the thermomechanical effect at various detecting *** residual stress was established based on the undeformed chip thickness model considering the profile structure,with a prediction error of 10%–15%.The thermomechanical effect is more obvious at the bottom area,where the surface roughness,work hardening degree,and subsurface plastic deformation range are the largest,while the values at the bevel area are the *** on the undeformed chip thickness model,a residual stress finite element simulation was conducted by employing thermomechanical coupled *** addition,the error between the simulation and the experiment was between 10%–15%.Strain and strain rate equations were established through the relationship between material displacement and *** average strain and strain rate of the ground surface when ap is 1.0 mm are 18.8%and 33.2%l

关键词： Gamma titanium-aluminum intermetallic compounds Blade tenon Creep feed profile grinding Surface integrity Thermomechanical effect

A Dual-Cluster-Head Based Medium Access Control for Large-Scale UAV Ad-Hoc Networks

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

China communications 2024年第5期21卷 123-136页

作者： Zhao Xinru Wei Zhiqing Zou Yingying Ma Hao Cui Yanpeng Feng Zhiyong key laboratory of Universal Wireless communications Ministry of EducationSchool of Information and Communication EngineeringBeijing University of Posts and TelecommunicationsBeijing100876China

Unmanned Aerial Vehicle(UAV)ad hoc network has achieved significant growth for its flexibility,extensibility,and high deployability in recent *** application of clustering scheme for UAV ad hoc network is imperative to enhance the performance of throughput and energy *** conventional clustering scheme,a single cluster head(CH)is always assigned in each ***,this method has some weaknesses such as overload and premature death of CH when the number of UAVs *** order to solve this problem,we propose a dual-cluster-head based medium access control(DCHMAC)scheme for large-scale UAV *** DCHMAC,two CHs are elected to manage resource allocation and data forwarding ***,two CHs work on different *** of CH is used for intra-cluster communication and the other one is for inter-cluster communication.A Markov chain model is developed to analyse the throughput of the *** result shows that compared with FM-MAC(flying ad hoc networks multi-channel MAC,FM-MAC),DCHMAC improves the throughput by approximately 20%~50%and prolongs the network lifetime by approximately 40%.

关键词： dual cluster head medium access control UAV swarm

Engineering the future cereal crops with big biological data:toward intelligence-driven breeding by design

在线全文

学校读者我要写书评

暂无评论

Journal of Genetics and Genomics 2024年第8期51卷 781-789页

作者： Lei Liu Jimin Zhan Jianbing Yan national key laboratory of Crop Genetic Improvement Hubei Hongshan LaboratoryHuazhong Agricultural UniversityWuhanHubei 430070China

How to feed 10 billion human populations is one of the challenges that need to be addressed in the following decades,especially under an unpredicted climate *** breeding,initiating from the phenotype-based selection by local farmers and developing into current biotechnology-based breeding,has played a critical role in securing the global food ***,regarding the changing environment and ever-increasing human population,can we breed outstanding crop varieties fast enough to achieve high productivity,good quality,and widespread adaptability?This review outlines the recent achievements in understanding cereal crop breeding,including the current knowledge about crop agronomic traits,newly developed techniques,crop big biological data research,and the possibility of integrating them for intelligence-driven breeding by design,which ushers in a new era of crop breeding practice and shapes the novel architecture of future *** review focuses on the major cereal crops,including rice,maize,and wheat,to explain how intelligence-driven breeding by design is becoming a reality.

关键词： Crop Big biological data Multi-omic Artificial intelligence Crop design breeding

Chiral electron transporting material for circularly polarized organic light-emitting diode

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China Chemistry 2024年第11期67卷 3777-3784页

作者： Peihao Huo Tianyu Yang Peiyu Fang Yujia Li Nanlong Zheng Min Gong Zuqiang Bian Zhiwei Liu Beijing national laboratory for Molecular Sciences State Key Laboratory of Rare Earth Materials Chemistry and ApplicationsCollege of Chemistry and Molecular Engineering Peking University

Circularly polarized organic light-emitting diode(CP-OLED) has attracted increasing interest for its efficient ability to generate circularly polarized light directly. So far, many CP-OLEDs were successfully fabricated with chiral emitters or chiral hosts. In this study, a new strategy based on chiral electron transporting layer is proposed to construct CP-OLEDs. A pair of chiral electron transporting materials, 1,3,5-tris((R/S)-4-isopropyl-4,5-dihydrooxazol-2-yl)benzene((R/S)-TOxiPr), are firstly designed and synthesized. The crystalline films of(R/S)-TOxiPr show circularly polarized photoluminescence with photoluminescence dissymmetry factors of-0.067 and +0.041, respectively. The CP-OLEDs based on(R/S)-TOxiPr and three types of achiral emitters all exhibit circularly polarized electroluminescence, showing feasibility and strong versatility of this new strategy. The mechanism is attributed to in-situ electrical excitation instead of simply light filtering of non-circularly polarized light. This work demonstrates a new approach for realizing circularly polarized electroluminescence which may provide a valuable strategy to develop CP-OLEDs.

关键词： circularly polarized organic light-emitting diodes chiral electron transporting layer trisoxazolinylbenzene circularly polarized electroluminescence

GS-orthogonalization OMP method for space target detection via bistatic space-based radar

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第7期37卷 333-351页

作者： Shuyu ZHENG Libing JIANG Qingwei YANG Yingjian ZHAO Zhuang WANG national key laboratory of Science and Technology on Automatic Target Recognition College of Electronic Science and TechnologyNational University of Defense TechnologyChangsha 410073China

A space-based bistatic radar system composed of two space-based radars as the transmitter and the receiver respectively has a wider surveillance region and a better early warning capability for high-speed targets,and it can detect focused space targets more flexibly than the monostatic radar system or the ground-based radar ***,the target echo signal is more difficult to process due to the high-speed motion of both space-based radars and space *** be specific,it will encounter the problems of Range Cell Migration(RCM)and Doppler Frequency Migration(DFM),which degrade the long-time coherent integration performance for target detection and localization *** solve this problem,a novel target detection method based on an improved Gram Schmidt(GS)-orthogonalization Orthogonal Matching Pursuit(OMP)algorithm is proposed in this ***,the echo model for bistatic space-based radar is constructed and the conditions for RCM and DFM are ***,the proposed GS-orthogonalization OMP method is applied to estimate the equivalent motion parameters of space ***,the RCM and DFM are corrected by the compensation function correlated with the estimated motion ***,coherent integration can be achieved by performing the Fast Fourier Transform(FFT)operation along the slow time direction on compensated echo *** simulations and real raw data results validate that the proposed GS-orthogonalization OMP algorithm achieves better motion parameter estimation performance and higher detection probability for space targets detection.

关键词： Bistatic space-based radar High-speed maneuvering space targets detection Range Cell Migration(RCM) Doppler Frequency Migration(DFM) Gram Schmidt(GS)-orthogonalization Orthogonal Matching Pursuit(OMP)algorithm