检索结果-南通市图书馆

Observation of gapless corner modes of photonic crystal slabs in synthetic translation dimensions

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Photonics Research 2024年第3期12卷 444-455页

作者： WEN-JiN ZHANG HAO-CHANG MO WEN-JiE CHEN XiAO-dong CHEN JiAN-WEN dong School of Physics&State Key Laboratory of Optoelectronic Materials and Technologies Sun Yat-sen UniversityGuangzhou 510275China

Second-order topological photonic crystals support localized corner modes that deviate from the conventional bulk-edge ***,the frequency shift of corner modes spanning the photonic band gap has not been experimentally ***,we observe the gapless corner modes of photonic crystal slabs within a parameter space by considering translation as an additional synthetic *** corner modes,protected by topological pumping in synthetic translation dimensions,are found to exist independently of the specific corner *** gapless corner modes are experimentally imaged via the near-field scanning measurement and validated numerically by full-wave *** propose a topological rainbow with gradient translation,demonstrating the ability to extract and separate specific frequency components of light into different spatial *** work contributes to the advancement of topological photonics and provides valuable insights into the exploration of gapless corner modes in synthetic dimensions.

关键词： translation dimensions corner

Recent Advances in Pd-Catalyzed Reactions involving the “On-Water” Mechanism

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 2024年第5期42卷 533-542页

作者： dong Wei Guo-Qiang Lin State Key Laboratory of Systems Medicine for Cancer Shanghai Cancer InstituteShanghai Key Laboratory of Systems Regulation and Clinical Translation for CancerRen Ji HospitalShanghai Jiao Tong University School of MedicineShanghai200127 China State Key Laboratory of Chemical biology Shanghai Institute of Organic ChemistryUniversity of Chinese Academy of SciencesChinese Academy of SciencesShanghai200032 China

As the chemical industry grapples with the need for more eco-friendly practices,the use of water as a reaction medium is gaining attraction in organic *** mini-review delves into Pd-catalyzed reactions that utilize the "on-water" mechanism,spanning from 2019 to late *** reactions are neatly categorized into several types: (A) Catalytic C—H activations,(b) Mizoroki- Heck-type reactions,(C) Suzuki-Miyaura reactions,and (D) Cyclization *** showcasing the potential of water as a sustainable reaction medium for organic transformations,these reactions leave no doubt about the importance of embracing eco-friendly practices in the chemical *** Scientists in 1980,a seminal work by breslow et *** an acceleration of reaction rate in the Diels-Alder *** and co-workers noted a significant increase in the rate of the [2σ+2σ+2π] cycloaddition of quadricyclane and dimethyl azodicarboxylate (DMAD) when the reaction was conducted in water,as opposed to when it was carried out in organic *** term "on-water" was then coined to describe this *** strategy was further expanded to transition-metal catalyzed transformations by Ackermann in ***,Varma and Leazer disclosed a Pd-catalyzed Mizoroki-Heck type arylation of alkenes with diaryliodonium salts “on-water”.The enantioselective version of "on-water" process was not realized until 2014 by the Zhou *** on,the Schaub group described a Pd-catalyzed Suzuki–Miyaura coupling reaction of electron-poor aryl chlorides with water,using only 50 ppm of catalyst *** recently,Liu and Lin extended the "on-water" strategy to Pd-catalyzed double Mizoroki-Heck *** mini-review has focused on Pd-catalyzed reactions involving the “on-water” mechanism.

关键词： Pd-catalyzed “On-water” Green chemistry Aqueous reactions Mechanism Methodology and reactions Mizoroki-Heck reaction Cross-coupling

Local search yields a PTAS for fixed-dimensional k-means problem with penalties

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 the Operations Research Society of China 2024年第2期12卷 351-362页

作者： Fan Yuan Da-Chuan Xu dong-Lei Du dong-Mei Zhang b.ijing institute for Scientific and Engineering Computing Beijing University of TechnologyBeijing 100124China Faculty of Management University of New BrunswickFrederictonNB E3B 9Y2Canada School of Computer Science and Technology Shandong Jianzhu UniversityJinan 250101ShandongChina

We study a problem called the k-means problem with penalties(k-MPWP),which is a natural generalization of the typical k-means *** this problem,we have a set D of client points in R^(d),a set F of possible centers in R^(d),and a penalty cost Pj>O for each point j∈*** are also given an integer k which is the size of the center point *** want to find a center point set S■F with size k,choose a penalized subset of clients P■D,and assign every client in D\P to its open *** goal is to minimize the sum of the squared distances between every point in D\P to its assigned centre point and the sum of the penalty costs for all clients in *** using the multi-swap local search technique and under the fixed-dimensional Euclidean space setting,we present a polynomial-time approximation scheme(PTAS)for the k-MPWP.

关键词： Approximation algorithm k-means Local search Penalty

Multi-modal visual tracking:Review and experimental comparison

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Computational Visual Media 2024年第2期10卷 193-214页

作者： Pengyu Zhang dong Wang Huchuan Lu Faculty of Electronic information and Electrical Engineering Dalian University of TechnologyDalian 116024Chin

Visual object tracking has been drawing increasing attention in recent years,as a fundamental task in computer *** extend the range of tracking applications,researchers have been introducing information from multiple modalities to handle specific scenes,with promising research prospects for emerging methods and *** provide a thorough review of multi-modal tracking,different aspects of multi-modal tracking algorithms are summarized under a unified taxonomy,with specific focus on visibledepth(RGb-D)and visible-thermal(RGb-T)***,a detailed description of the related benchmarks and challenges is *** experiments were conducted to analyze the effectiveness of trackers on five datasets:PTb,VOT19-RGbD,GTOT,RGbT234,and ***,various future directions,including model design and dataset construction,are discussed from different perspectives for further research.

关键词： visual tracking object tracking multi-modal fusion RGb-T tracking RGb-D trackin

Comprehension-driven design of advanced multi-block single-ion conducting polymer electrolytes for high-performance lithium-metal batteries

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 Energy Chemistry 2024年第7期94卷 357-359页

作者： Xu dong Dominic bresser Helmholtz institute Ulm(HiU) Helmholtzstrasse 1189081 UlmGermany Karlsruhe institute of Technology(KiT) P.O.Box 364076021 KarlsruheGermany

The continuously growing importance of batteries for powering(hyb.id)electric vehicles and storing renewable energy has prompted a renewed focus on lithium-metal batteries(LMbs)in recent years,as its high theoretical specific capacity of about 3860 mA h g^(-1) and very low redox potential(-3.04 V *** standard hydrogen electrode)promise substantially higher energy densities compared to current lithium-ion batteries(Libs)[1].However,lithium metal electrodes face severe challenges associated with the risk of dendritic lithium deposition and the high reactivity with traditional organic liquid electrolytes,resulting in a continuous loss of electrochemically active lithium and a relatively low Coulombic efficiency[2].To address these challenges,solid inorganic and polymer electrolytes have emerged as a potentially saferalternative.

关键词： lithium polymer prompt

High-Efficiency Wideband Transmitarray Antenna Using Polarization-Rotating Elements with Parasitic Stubs

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Electronics 2024年第2期33卷 496-503页

作者： Xi WANG Yuandan dong University of Electronic Science and Technology of China

A high-efficiency polarization-rotating transmitarray antenna(TA) using wideband elements is proposed for millimeter-wave applications. The polarization-rotating element consists of three metallic layers and two substrates. Orthogonal polarizers are employed on the top and bottom of the element. And the split ring with a parasitic stub on the middle layer is symmetric about the diagonal, performing the polarization rotation and phase compensation simultaneously. A parasitic stub.is designed to decrease transmission loss and broaden the bandwidth. The periodicity of the element is only 1/4 wavelength at 30 GHz. A prototype TA with 28 × 28 elements is designed, fab.icated, and measured. The measured peak gain reaches 27.5 d bi at 37.8 GHz. The 1-d b gain drop bandwidth is 30.8–40 GHz(26.0%).The aperture efficiency reaches as high as 71% at 31.5 GHz. Within the bandwidth of 26.5–38.8 GHz(37.7%), the aperture efficiency is higher than 50%. The proposed polarization-rotating TA features wide bandwidth and high efficiency, demonstrating great application potential for 5G millimeter-wave communication.

关键词： Wavelength measurement Transmitting antennas Prototypes Apertures Gain measurement Propagation losses broadband antennas

A Degree Condition for Graphs Having All(a,b)-parity Factors

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mathematicae Applicatae Sinica 2024年第3期40卷 656-664页

作者： Hao-dong LiU Hong-liang LU School of Mathematics and Statistics Xi'an Jiaotong UniversityXi'an 710049China

Let a and b be positive integers such that a≤b and a≡b(mod 2).We say that G has all(a,b)-parity factors if G has an h-factor for every function h:V(G)→{a,a+2,…,b-2,b} with b|V(G)| even and h(v)≡b(mod 2) for all v∈V(G).in this paper,we prove that every graph G with n≥2(b+1)(a+b) vertices has all(a,b)-parity factors if δ(G)≥(b^(2)-b)/a,and for any two nonadjacent vertices u,v ∈V(G),max{d_(G)(u),d_(G)(v)}≥bn/a+***,we show that this result is best possible in some sense.

关键词： degree condition all(a,b)-factors

Density functional theory study of b- and Si-doped carbons and their adsorption interactions with sulfur compounds

在线全文

学校读者我要写书评

暂无评论

Carbon Energy 2024年第2期6卷 195-208页

作者： Peng Guo Hong Zhang Shuliang dong Libao An College of Mechanical Engineering North China University of Science and TechnologyTangshanHebeiChina College of Life Sciences North China University of Science and TechnologyTangshanHebeiChina

Understanding the adsorption interactions between carbon materials and sulfur compounds has far-reaching impacts,in addition to their well-known important role in energy storage and conversion,such as lithium-ion *** this paper,properties of intrinsic b or Si single-atom doped,and b-Si codoped graphene(GR)and graphdiyne(GDY)were investigated by using density functional theory-based calculations,in which the optimal doping configurations were explored for potential applications in adsorbing sulfur *** showed that both b or Si single-atom doping and b-Si codoping could substantially enhance the electron transport properties of GR and GDY,improving their surface ***,b and Si atoms displayed synergistic effects for the codoped configurations,where b-Si codoped GR/GDY exhibited much better performance in the adsorption of sulfurcontaining chemicals than single-atom doped *** addition,results demonstrated that,after b-Si codoping,the adsorption energy and charge transfer amounts of GDY with sulfur compounds were much larger than those of GR,indicating that b-Si codoped GDY might be a favorable material for more effectively interacting with sulfur reagents.

关键词： adsorption density functional theory doping graphdiyne graphene sulfur compounds

investigation of high rate mechanical flow followed by ignition for high-energy propellant under dynamic extrusion loading

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2024年第2期32卷 336-347页

作者： Liying dong Yanqing Wu Kun Yang Xiao Hou State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China

investigating the ignition response of nitrate ester plasticized polyether(NEPE) propellant under dynamic extrusion loading is of great significant at least for two cases. Firstly, it helps to understand the mechanism and conditions of unwanted ignition inside charged propellant under accident ***, evaluates the risk of a shell crevice in a solid rocket motor(SRM) under a falling or overturning scene. in the present study, an innovative visual crevice extrusion experiment is designed using a dropweight apparatus. The dynamic responses of NEPE propellant during extrusion loading, including compaction and compression, rapid shear flow into the crevice, stress concentration, and ignition reaction, have been firstly observed using a high-performance high-speed camera. The ignition reaction is observed in the triangular region of the NEPE propellant sample above the crevice when the drop weight velocity was 1.90 m/s. based on the user material subroutine interface UMAT provided by finite element software LS-DYNA, a viscoelastic-plastic model and dual ignition criterion related to plastic shear dissipation are developed and applied to the local ignition response analysis under crevice extrusion conditions. The stress concentration occurs in the crevice location of the propellant sample, the shear stress is relatively large, the effective plastic work is relatively large, and the ignition reaction is easy to occur. When the sample thickness decreases from 5 mm to 2.5 mm, the shear stress increases from 22.3 MPa to 28.6 MPa, the critical value of effective plastic work required for ignition is shortened from 1280 μs to 730 μs, and the triangular area is easily triggering an ignition reaction. The propellant sample with a small thickness is more likely to stress concentration, resulting in large shear stress and effective work, triggering an ignition reaction.

关键词： NEPE propellant Crevice extrusion Shear flow Sample thickness ignition reaction