检索结果-南通市图书馆

Far-Field Noise Induced by Bubble near Free Surface

在线全文

学校读者我要写书评

暂无评论

China Ocean Engineering 2018年第1期32卷 26-31页

作者： YE xi LIJiang-tao LIUJian-hua CHENHai-long Marine Design & Research Institute of China Shanghai 200011China Harbin Engineering University Harbin 150001China

The motion of a bubble near the free surface is solved by the boundary element method based on the linear wave equation, and the influence of fluid compressibility on bubble dynamics is analyzed. Based on the solution of the bubble motion, the far-field radiation noise induced by the bubble is calculated using Kirchhoff moving boundary integral equation, and the influence of free surface on far-field noise is researched. As the results, the oscillation amplitude of the bubble is weakened in compressible fluid compared with that in incompressible fluid, and the free surface amplifies the effect of fluid compressibility. When the distance between the bubble and an observer is much larger than that between the bubble and free surface, the sharp wave trough of the sound pressure at the observer occurs. With the increment of the distance between the bubble and free surface, the time of the wave trough appearing is delayed and the value of the wave trough increase. When the distance between the observer and the bubble is reduced, the sharp wave trough at the observer disappears.

关键词： bubble free surface compressibility far-field noise

Essentially Commuting Truncated Toeplitz Operators

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2024年第10期40卷 2453-2480页

作者： xi ZHAO Tao yu School of Mathematics and Science Hebei GEO University Shijiazhuang 050031P.R.China School of Mathematical Sciences Dalian University of Technology Dalian 116024P.R.China

A model space is a subspace of the Hardy space which is invariant under the backward shift,and a truncated Toeplitz operator is the compression of a Toeplitz operator on some model *** this paper we prove a necessary ... 详细信息

关键词： Truncated Toeplitz operator model space commutator maximal ideal space compact operator

Controlled moderative sulfidation-fabricated hierarchical heterogeneous nickel sulfides-based electrocatalyst with tripartite Mo doping for efficient oxygen evolution

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2022年第5期31卷 780-788页

作者： xing yu Qingyun Lv Lulu She long Hou Yves Fautrelle Zhongming Ren Guanghui Cao xionggang Lu xi Li State Key Laboratory of Advanced Special Steels School of Materials Science and EngineeringShanghai UniversityShanghai 200072China Shanghai Key Lab of Advanced High-temperature Materials and Precision Forming Shanghai Jiao Tong UniversityShanghai 200240China SIMAP-EPM-Madylam/G-INP/CNRS PHELMABP 7538402 St Martin d’HeresCedexFrance

An electrocatalyst with heterogeneous nanostructure, especially the hierarchical one, generally shows a more competitive activity than that of its single-component counterparts for oxygen evolution reaction(OER), due to the synergistically enhanced kinetics on enriched active sites and reconfigured electronic band structure. Here this work introduces hierarchical heterostructures into a NiMo@NiS/MoS_(2)@Ni_(2)S_(2)/MoO_(x)(NiMoS) composite by one-pot controlled moderative sulfidation. The optimal solvent composition and addition of NaOH enable NiMoS to own loose and porous structures, smaller nanoparticle sizes, optimal phase composition and chemical states of elements, improving the OER activity of NiMoS. To achieve current densities of 50 and 100 mA cm^(-1), small overpotentials of 275 and 306 mV are required respectively, together with a minor Tafel slope of 58 mV dec^(-1), which outperforms most reported sulfide catalysts and IrO_(2). The synergistic effects in the hierarchical heterostructures expose more active sites,adjust the electronic band structure, and enable the fast charge transfer kinetics, which construct an optimized local coordination environment for high OER electrocatalytic activity. Furthermore, the hierarchical heterostructures suppress the distinct lowering of electrical conductivity and collapse of pristine structures resulted from the metal oxidation and synchronous S leaching during OER, yielding competitive catalytic stability.

关键词： OER electrocatalysts Controlled moderative sulfidation Hierarchical heterostructures Nickel sulfides Tripartite Mo doping

Routing the asteroid surface vehicle with detailed mechanics

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2014年第3期30卷 301-309页

作者： Yang yu He-xi Baoyin School of Aerospace N931 Mengminwei Research BuildingTsinghua University

The motion of a surface vehicle on/above an irregular object is *** for a potential interest in the insitu explorations to asteroids of the solar system. A global valid numeric method, including detailed gravity and geo- morphology, is developed to mimic the behaviors of the test particles governed by the orbital equations and surface cou- pling effects. A general discussion on the surface mechanical environment of a specified asteroid, 1620 Geographos, is presented to make a global evaluation of the surface vehicle＇s working conditions. We show the connections between the natural trajectories near the ground and differential features of the asteroid surface, which describes both the good and bad of typical terrains from the viewpoint of vehicles＇ dynamic performances. Monte Carlo simulations are performed to take a further look at the trajectories of particles initializing near the surface. The simulations reveal consistent conclusions with the analysis, i.e., the open- field flat ground and slightly concave basins/valleys are the best choices for the vehicles＇ dynamical security. The dependence of decending trajectories on the releasing height is studied as an application; the results show that the pole direction （where the centrifugal force is zero） is the most stable direction in which the shift of a natural trajectory will be well limited after landing. We present this work as an example for pre-analysis that provides guidance to engineering design of the exploration site and routing the surface vehicles.

关键词： Asteroid exploration Numeric model Morphodynamics 1620 Geographos Path planning

A novel noise reduction technique for underwater acoustic signals based on complete ensemble empirical mode decomposition with adaptive noise,minimum mean square variance criterion and least mean square adaptive filter

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2020年第3期16卷 543-554页

作者： yu-xing Li long Wang Faculty of Information Technology and Equipment Engineering Xi'an University of TechnologyXi'an 710048ShaanxiChina School of Marine Science and Technology Northwestern Polytechnical UniversityXi'an 710072ShaanxiChina

Underwater acoustic signal processing is one of the research hotspots in underwater *** reduction of underwater acoustic signals is the key to underwater acoustic signal *** to the complexity of marine environment and the particularity of underwater acoustic channel,noise reduction of underwater acoustic signals has always been a difficult challenge in the field of underwater acoustic signal *** order to solve the dilemma,we proposed a novel noise reduction technique for underwater acoustic signals based on complete ensemble empirical mode decomposition with adaptive noise(CEEMDAN),minimum mean square variance criterion(MMSVC) and least mean square adaptive filter(LMSAF).This noise reduction technique,named CEEMDAN-MMSVC-LMSAF,has three main advantages:(i) as an improved algorithm of empirical mode decomposition(EMD) and ensemble EMD(EEMD),CEEMDAN can better suppress mode mixing,and can avoid selecting the number of decomposition in variational mode decomposition(VMD);(ii) MMSVC can identify noisy intrinsic mode function(IMF),and can avoid selecting thresholds of different permutation entropies;(iii) for noise reduction of noisy IMFs,LMSAF overcomes the selection of deco mposition number and basis function for wavelet noise ***,CEEMDAN decomposes the original signal into IMFs,which can be divided into noisy IMFs and real ***,MMSVC and LMSAF are used to detect identify noisy IMFs and remove noise components from noisy ***,both denoised noisy IMFs and real IMFs are reconstructed and the final denoised signal is *** with other noise reduction techniques,the validity of CEEMDAN-MMSVC-LMSAF can be proved by the analysis of simulation signals and real underwater acoustic signals,which has the better noise reduction effect and has practical application ***-MMSVC-LMSAF also provides a reliable basis for the detection,feature extraction,classification and recognition of underwater acousti

关键词： Underwater acoustic signal Noise reduction Empirical mode decomposition(EMD) Ensemble EMD(EEMD) Complete EEMD with adaptive noise(CEEMDAN) Minimum mean square variance criterion(MMSVC) Least mean square adaptive filter(LMSAF) Ship-radiated noise

Cooperative Target Tracking of Multiple Autonomous Surface Vehicles Under Switching Interaction Topologies

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2023年第3期10卷 673-684页

作者： Lang Ma yu-long Wang Qing-long Han Shanghai Key Laboratory of Power Station Automation Technology and the School of Mechatronic Engineering and AutomationShanghai UniversityShanghai 200444China School of Science Computing and Engineering TechnologiesSwinburne University of TechnologyMelbourne VIC 3122Australia IEEE

This paper is concerned with the cooperative target tracking of multiple autonomous surface vehicles(ASVs)under switching interaction *** the target to be tracked,only its position can be measured/received by some of the ASVs,and its velocity is unavailable to all the ASVs.A distributed extended state observer taking into consideration switching topologies is designed to integrally estimate unknown target dynamics and neighboring ASVs'***,a novel kinematic controller is designed,which takes full advantage of known information and avoids the approximation of some virtual control ***,a disturbance observer is presented to estimate unknown time-varying environmental ***,a distributed dynamic controller is designed to regulate the involved ASVs to cooperatively track the *** enables each ASV to adjust its forces and moments according to the received information from its *** effectiveness of the derived results is demonstrated through cooperative target tracking performance analysis for a tracking system composed of five interacting ASVs.

关键词： Autonomous surface vehicles(ASVs) cooperative target tracking distributed extended state observer switching topologies

Mechanistic insight into the synergy between nickel single atoms and nanoparticles on N-doped carbon for electroreduction of CO2

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2025年第01期 327-336页

作者： Mingdong Sun Wenwen Guan Cailing Chen Chao Wu xiaoling Liu Biao Meng Tao Chen yu Han Jun Wang Shibo xi yu Zhou State Key Laboratory of Materials-Oriented Chemical Engineering College of Chemical Engineering Nanjing Tech University Advanced Membranes and Porous Materials Center Physical Sciences and Engineering Division King Abdullah University of Science and Technology Institute of Sustainability for Chemicals Energy and Environment A*STAR (Agency for Science Technology and Research) College of Materials Science and Engineering Sichuan University

The synergy of single atoms （SAs） and nanoparticles （NPs） has demonstrated great potential in promoting the electrocatalytic carbon dioxide reduction reaction （CO2RR）;however,the rationalization of the SAs/NPs proportion remains one challenge for the catalyst ***,a Ni2+-loaded porous poly（ionic liquids）(PIL) precursor synthesized through the free radical self-polymerization of the ionic liquid monomer,1-allyl-3-vinylimidazolium chloride,was pyrolyzed to prepare the Ni,N co-doped carbon materials,in which the proportion of Ni SAs and NPs could be facilely modulated by controlling the annealing *** catalyst Ni-NC-1000 with a moderate proportion of Ni SAs and NPs exhibited high efficiency in the electrocatalytic conversion of CO2into *** Ni K-edge X-ray absorption near-edge structure （XANES） spectra and theoretical calculations were conducted to gain insight into the synergy of Ni SAs and *** charge transfer from Ni NPs to the surrounding carbon layer and then to the Ni SAs resulted in the electron-enriched Ni SAs active *** the electroreduction of CO2,the coexistence of Ni SAs and NPs strengthened the CO2activation and the affinity towards the key intermediate of*COOH,lowering the free energy for the potential-determining*CO2→*COOH step,and therefore promoted the catalysis efficiency.

关键词：

Fuzzy Zorn’s lemma with applications

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Applied Mathematics(A Journal of Chinese Universities) 2021年第4期36卷 521-536页

作者： xiN xiao-long FU yu-long School of Science Xi’an Polytechnic UniversityXi’an 710048China School of Mathematics Northwest UniversityXi’an 710127China School of Cyber Engineering Xidian UniversityXi’an 710071China

We introduced the fuzzy axioms of choice,fuzzy Zorn’s lemma and fuzzy well-ordering principle,which are the fuzzy versions of the axioms of choice,Zorn’s lemma and well-ordering principle,and discussed the relations among *** an application of fuzzy Zorn’s lemma,we got the following results:(1)Every proper fuzzy ideal of a ring was contained in a maximal fuzzy ideal.(2)Every nonzero ring contained a fuzzy maximal ideal.(3)Introduced the notion of fuzzy nilpotent elements in a ring R,and proved that the intersection of all fuzzy prime ideals in a commutative ring R is the union of all fuzzy nilpotent elements in R.(4)Proposed the fuzzy version of Tychonoff Theorem and by use of fuzzy Zorn’s lemma,we proved the fuzzy Tychonoff Theorem.

关键词： fuzzy axioms of choice fuzzy Zorn’s lemma fuzzy well-ordering principle fuzzy ideal of a ring fuzzy Tychonoff Theorem

Complex Wave Excitations in Generalized Broer-Kaup System

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2007年第4X期48卷 657-661页

作者： ZHENG Chun-long FEI Jin-xi College of Mathematics and Physics Lishui University Lishui 323000 China Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China

Starting from an improved projective method and a linear variable separation approach, new families of variable separation solutions （including solltary wave solutlons, periodic wave solutions and rational function solutions） with arbitrary functions [or the （2＋ 1）-dimensional general/zed Broer-Kaup （GBK） system are derived. Usually, in terms of solitary wave solutions and/or rational function solutions, one can find abundant important localized excitations. However, based on the derived periodic wave solution in this paper, we reveal some complex wave excitations in the （2＋1）-dimensional GBK system, which describe solitons moving on a periodic wave background. Some interesting evolutional properties for these solitary waves propagating on the periodic wave bactground are also briefly discussed.

关键词： improved projective method GBK system exact solution complex wave excitation