检索结果-南通市图书馆

Sub-Nyquist sampling-based wideband spectrum sensing:a compressed power spectrum estimation approach

在线全文

学校读者我要写书评

暂无评论

Frontiers of Computer Science 2024年第2期18卷 139-145页

作者： Jilin WANG Yinsen huang Bin WANG National Key Laboratory of Science and Technology on Communications University of Electronic Science and Technology of ChinaChengdu 611731China

In this paper,we introduce a sub-Nyquist sampling-based receiver architecture and method for wideband spectrum *** of recovering the original wideband analog signal,the proposed method aims to directly reconstruct the power spectrum of the wideband analog signal from sub-Nyquist *** that power spectrum alone is sufficient for wideband spectrum *** only the covariance matrix of the wideband signal is needed,the proposed method,unlike compressed sensing-based methods,does not need to impose any sparsity requirement on the frequency *** proposed method is based on a multi-coset sampling *** exploiting the inherent sampling structure,a fast compressed power spectrum estimation method whose primary computational task consists of fast Fourier transform(FFT)is *** results are presented to show the effectiveness of the proposed method.

关键词： wideband spectrum sensing sub-Nyquist multicoset sampling FCPSE

Tactile-sensing-based robotic grasping stability analysis

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6期67卷 1817-1828页

作者： huang YanJiang WANG HaoNan ZHANG XianMin Guangdong Provincial Key Laboratory of Precision Equipment and Manufacturing Technology South China University of TechnologyGuangzhou510640China

Tactile signals play a crucial role in enabling robots to successfully manipulate unfamiliar *** robots to grasp unknown objects securely and without causing damage,it is essential that they can analyze grasping stability in real time through tactile signals and respond *** study introduces a novel method for analyzing the stability of robotic hand grasping,utilizing the Wilcoxon signed rank *** efficacy of this method is demonstrated through its static and dynamic performance,and evaluated across a series of *** findings of this research highlight the method’s ability to accurately detect when an object begins to slip from the robot’s *** this method allows the gripper to maintain a secure hold on objects by applying the minimal necessary *** also enables the gripper to dynamically adjust the force it applies in real time,thus preventing the object from slipping during the movement of the robotic ***,the gripper demonstrates the ability to stably grasp objects of varied weights and with unknown characteristics,showcasing the versatility and effectiveness of the proposed method.

关键词： grasping stability manipulation tactile sensors

Ecological network analysis reveals complex responses of tree species life stage interactions to stand variables

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2024年第1期35卷 29-43页

作者： Hengchao Zou Huayong Zhang Tousheng huang Research Center for Engineering Ecology and Nonlinear Science North China Electric Power UniversityBeijing 102206People’s Republic of China

Tree interactions are essential for the structure,dynamics,and function of forest ecosystems,but variations in the architecture of life-stage interaction networks(LSINs)across forests is ***,we constructed 16 LSINs in the mountainous forests of northwest Hebei,China based on crown overlap from four mixed forests with two dominant tree *** results show that LSINs decrease the complexity of stand densities and basal areas due to the interaction cluster *** addition,we found that mature trees and saplings play different roles,the first acting as“hub”life stages with high connectivity and the second,as“bridges”controlling information flow with high *** the forests,life stages with higher importance showed better parameter stability within *** results reveal that the structure of tree interactions among life stages is highly related to stand *** efforts contribute to the understanding of LSIN complexity and provide a basis for further research on tree interactions in complex forest communities.

关键词： Tree interactions Life stages Interaction networks Ecological complexity

Spray characteristics of different regions downstream of a swirl cup

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 124-143页

作者： Donghui WANG Yong huang Hongzhou ZHANG Collaborative Innovation Center of Advanced Aero-Engine School of Energy and Power EngineeringBeihang UniversityBeijing 102206China National Key Laboratory of Science and Technology School of Energy and Power EngineeringBeihang UniversityBeijing 102206China

The spray characteristics of different regions downstream of swirl cups play a critical role in cold start and re-ignition of gas *** spray measurements were performed at the fuel pressures of 0.5,0.8,1.0,1.5,and 2.0 MPa and the fuel temperatures of-23,-13,-3,7,17 and 27℃,*** droplet size,droplet velocity,droplet number,and instantaneous spatial spray image of sprays from an aviation kerosene Jet-A were measured using a two-component phase Doppler particle analyzer and a digital off-axis holography *** the fuel pressure and temperature increase,the Sauter Mean Diameter(SMD)and spray non-uniformity of the Spray Shear Layer(SSL)gradually *** the fuel pressure increases,the SMD and spray non-uniformity of the Central Toroidal Recirculation Zone(CTRZ)gradually decrease,and the slopes of these curves both *** the fuel pressure increases,the SMD and spray nonuniformity of the CTRZ rapidly decrease at the fuel temperature of23℃,while slightly decrease at the fuel temperature of 27℃.The droplets in the CTRZ come from 3 different sources:simplex nozzle,venturi,and outside the *** the fuel pressure increases,the proportion of droplets recirculated from outside the CTRZ *** study proposed the concept of the“pressure critical point”for the swirl *** the fuel temperature decreases,the proportion of droplets recirculated from outside the CTRZ increases below the critical pressure,while decreases above the critical *** addition,through the models of liquid film formation and breakup on the curved cylindrical wall,a semi-theoretical model was established to predict the SMD of SSL for swirl *** prediction uncertainty of this model is less than 6%for all 14 conditions in this paper.

关键词： Swirl cup Sauter Mean Diameter(SMD) Spray non-uniformity Atomizing regions Semi-theoretical prediction Spray nozzles

Access to High-Molecular-Weight Polyethylenes through High Temperature Ethylene Polymerization Catalysed by Ethylene-Bridged ansa-(3-R-Cyclopentadienyl)(Fluorenyl) Zirconocene Complexes

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2024年第1期42卷 42-51,I0007页

作者： Bo Li Haiyan Ma Jiling huang Shanghai Key Laboratory of Functional Materials Chemistry and Laboratory of Organometallic Chemistry School of Chemistry and Molecular EngineeringEast China University of Science and TechnologyShanghai 200237China

A series of C1-symmetric ethylene-bridged ansa-(3-R-cyclopentadienyl)(fluorenyl) metallocene complexes(Zr: 1-5;Hf: 6) have been synthesized, characterized and investigated as catalyst precursors for the high temperature ethylene polymerization. Using methylaluminoxane(MAO) as the cocatalyst, zirconium complexes 1-5 bearing a bulky substituent on the 3-position of the cyclopendienyl ring showed high catalytic activities up to 1.48×10^(7) g PE·mol_(Zr)^(-1)·h^(-1) toward the polymerization of ethylene and afforded polyethylenes with high molecular weights(1.49×10^(5)-6.31×10^(5) g/mol), meanwhile exhibting great thermal stability at high temperatures up to 120 ℃ together with a long catalytic life time up to 2 h. By adopting low Al/Zr ratios, such as 125, polyethylenes with ultra high molecular weights up to 2.86×106 g/mol were obtained. It is worthy of noting that zirconium complexes 1-4 bearing a substituent with an aryl pendant showed temperature-dependent activities, which increased rapidly with the increase of polymerization temperature, thus weak interaction of the pendent aryl group with the cationic active center is proposed to account for the very low activities displayed at low temperatures. In contrast to zirconocene complexes 1-5, hafnocene complex 6 only displayed very low catalytic activities toward the polymerization of ethylene and afforded polyethylenes with molecular weights ten times smaller than those obtained by zirconocene complexes 1-5. Zirconocene complexes 1-5 were also able to catalyse the polymerization of propylene at high temperatures, but only afforded waxes with low molecular weights.

关键词： ansa-Metallocene Ethylene Propylene Polymerization High temperature

Improvements in properties of NdFeB magnets obtained via magnetron sputtering and thermal diffusion

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2024年第9期42卷 1710-1716,I0003页

作者： Jin Tang Weichao huang Dan Li School of Electronic Engineering Guangxi University of Science and TechnologyLiuzhou545006China China Rare Earth(Guangxi)Jinyuan Rare Earth New Materials Co. Ltd.Hezhou542603China China Rare Earth Group Co. Ltd.Ganzhou341000China Center of Experimental Teaching for Common Courses Panzhihua UniversityPanzhihua617000China

The grain boundary diffusion process(GBDP) of Dy and DyAl on sintered NdFeB magnets was conducted via magnetron-sputtering deposition of Dy and DyAl films to enhance coercivity(H_(cj)),The magnetic properties,microstructure and anti-corrosion properties of Dy-surface-alloying NdFeB magnets obtained via magnetron sputtering and thermal diffusion were *** H_(cj) of the Dy_(95)Al_(5)-NdFeB magnet increases by 32.68%,while the remanence declines ***,X-ray diffraction and microstructural analysis confirm the formation of Dy-rich shells,the higher-magnetic-anisotropy field of hard(Nd_(x)Dy_(1-x))2(FeAl)_(14)B magnetic phases and an optimised grain boundary structu re,contributing to the H_(cj)enhancement of the *** elemental distribution and diffusion mechanism of the magnets are also ***,the corrosion resistance of the Dy_(95)Al_(5)-NdFeB magnet is substantially improved by enhancing the electrochemical stability and optimising the distribution and morphology of the intergranular *** findings of this study are of substantial importance in the development of low-heavy rare-earth sintered NdFeB magnets.

关键词： Magnetron sputtering NdFeB Rare earths Microstructure Magnetic property Corrosion resistance

Scientific and technological innovations of wastewater treatment in China

在线全文

学校读者我要写书评

暂无评论

Frontiers of Environmental Science & Engineering 2024年第6期18卷 43-48页

作者： Hui huang Rui Ma Hongqiang Ren State Key Laboratory of Pollution Control and Resource Reuse School of the EnvironmentNanjing UniversityNanjing 210023China

The“dual-carbon”strategy promotes the development of the wastewater treatment sector and is an important tool for leading science and technology *** on the global climate change and the new policies introduced by China,this paper described the new needs for the development of wastewater treatment science and *** offered a retrospective analysis of the historical trajectory of scientific and technological advancements in this *** bibliometrics,it delineated the research hotspots within wastewater treatment,notably highlighting materials genomics,artificial intelligence,and synthetic ***,it posited that,in the future,the field of wastewater treatment should follow the paths of technological innovations with multi-dimensional needs,such as carbon reduction,pollution reduction,health,standardisation,and *** purpose of this paper was to provide references and suggestions for scientific and technological innovations in the field of wastewater treatment,and to contribute to the common endeavor of moving toward a Pollution-Free Planet.

关键词： Wastewater treatment Dual-carbon strategy Technological innovation Carbon reduction

Time-of-flight resolved stimulated Raman scattering microscopy using counter-propagating ultraslow Bessel light bullets generation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Light(Science & Applications) 2024年第7期13卷 1427-1440页

作者： Shulang Lin Li Gong Zhiwei huang Optical Bioimaging Laboratory Department of Biomedical EngineeringCollege of Design and EngineeringNational University of SingaporeSingapore 117576Singapore

We present a novel time-of-flight resolved Bessel light bullet-enabled stimulated Raman scattering(B2-SRS)microscopy for deeper tissue 3D chemical imaging with high resolution without a need for mechanical *** accomplish the tasks,we conceive a unique method to enable optical sectioning by generating the counterpropagating pump and Stokes Bessel light bullets in the sample,in which the group velocities of the Bessel light bullets are made ultraslow(e.g.,vg≈0.1c)and tunable by introducing programmable angular dispersions with a spatial light *** theoretically analyze the working principle of the collinear multicolor Bessel light bullet generations and velocity controls with the relative time-of-flight resolved detection for SRS 3D deep tissue *** have also built the B2-SRS imaging system and present the first demonstration of B2-SRS microscopy with Bessel light bullets for 3D chemical imaging in a variety of samples(e.g.,polymer bead phantoms,biological samples such as spring onion tissue and porcine brain)with high *** B2-SRS technique provides a>2-fold improvement in imaging depth in porcine brain tissue compared to conventional SRS *** method of optical sectioning in tissue using counter-propagating ultraslow Bessel light bullets developed in B2-SRS is generic and easy to perform and can be readily extended to other nonlinear optical imaging modalities to advance 3D microscopic imaging in biological and biomedical systems and beyond.

关键词： Bessel resolved propagating

Research Progress on Bio‑inspired Flapping‑Wing Rotor Micro Aerial Vehicle Development

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2024年第4期21卷 1621-1643页

作者： Yingjun Pan Shijun Guo Xun huang Centre for Aeronautics School of AerospaceTransport and ManufacturingCranfield UniversityBedford MK430ALUK

Flapping-wing rotor(FWR)is an innovative bio-inspired micro aerial vehicle capable of vertical take-off and *** unique design combines active flapping motion and passive wing rotation around a vertical central shaft to enhance aerodynamic *** research on FWR,though relatively new,has contributed to 6%of core journal publications in the micro aerial vehicle field over the past two *** paper presents the first comprehensive review of FWR,analysing the current state of the art,key advances,challenges,and future research *** review highlights FWR’s distinctive kinematics and aerodynamic superiority compared to traditional flapping wings,fixed wings,and rotary wings,discussing recent breakthroughs in efficient,passive wing pitching and asymmetric stroke amplitude for lift *** experiments and remote-controlled take-off and hovering tests of single and dual-motor FWR models have showcased their *** review compares FWR flight performance with well-developed insect-like flapping-wing micro aerial vehicles as the technology readiness level progresses from laboratory to outdoor flight testing,advancing from the initial flight of a 2.6 g prototype to the current free flight of a 60-gram *** review also presents ongoing research in bionic flexible wing structures,flight stability and control,and transitioning between hovering and cruise flight modes for an FWR,setting the stage for potential applications.

关键词： Flapping-wing rotor Micro aerial vehicle Bio-inspiration Flight