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Some Properties of an Operator on L~∞(△)and Its Applications

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Acta Mathematica Sinica,English Series 2007年第10期23卷 1909-1914页

作者： na SUN LMAM and School of Mathematical Sciences Peking University Beijing 100871 P. R. China

In this paper, we introduce an operator Hμ（z） on L^∞（△） and obtain some of its properties. Some applications of this operator to the extremal problem of quasiconformal mappings are given. In particular, a suffi... 详细信息

关键词： norm Hamilton sequence extremal Beltrami coefficient Strebel point

Fluorescence resonance energy transfer-based nanomaterials for the sensing in biological systems

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Chinese Chemical Letters 2022年第10期33卷 4505-4516页

作者： Xiaotong Shen Wei Xu Jin Ouyang na na School of Life Science Beijing Institute of TechnologyBeijing 100081China Key Laboratory of Radiopharmaceuticals Ministry of EducationCollege of ChemistryBeijing Normal UniversityBeijing 100875China

The applications of fluorescence resonance energy transfer(FRET)are coming to be one of the simplest and most accessible strategy with super-resolved optical ***,nanomaterials have become ideal for constructing FRET-based system,due to their unique advantages of tunable emission,broad absorption,and long fluorescence(FL)*** limitations of traditional FRET-based detections,such as the intrinsic FL,auto-FL,as well as the short FL lifetime,could be overcome with ***,numbers of FRET-based nanomaterials have been constructed for precise,sensitive and selective detections in biological *** could act as both energy donors and/or acceptors in the optical energy transfer process for biological *** other nanomaterials would not participate in the energy transfer process,but act as the excellent matrix for *** review will be roughly classified into nanomaterial-involved and uninvolved *** detection targets,such as nucleic acids,pathogenic microorganisms,proteins,heavy metal ions,and other applications will be ***,the other biological applications,including environmental evaluation and mechanism studies would also be summarized.

关键词： nanomaterials Fluorescence resonance energy transfer nano-sensors Detection Biochemical processes

Nonlinear Study on the Mechanical Performance of Built-Up Cold-Formed Steel Concrete-Filled Columns under Compression

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Computer Modeling in Engineering & Sciences 2024年第6期139卷 3435-3465页

作者： Oulfa Harrat Yazid Hadidane S.M.Anas nadhim Hamah sor Ahmed Farouk Deifalla Paul O.Awoyera nadia Gouider Civil Engineering Laboratory Faculty of TechnologyDepartment of Civil EngineeringBadji Mokhtar-Annaba UniversityP.O.Box 12Annaba23000Algeria Department of Civil Engineering Faculty of Engineering and TechnologyJamia Millia Islamia(A Central University)New Delhi110025India Civil Engineering Department University of GarmianKalar46021Iraq Department of Civil Engineering Harran UniversitySanliurfa63510Turkey Structural Engineering and Construction Management Department Future University in EgyptNew Cairo11835Egypt Department of Civil Engineering Covenant UniversityOta112233Nigeria

Given their numerous functional and architectural benefits,such as improved bearing capacity and increased resistance to elastic instability modes,cold-formed steel(CFS)built-up sections have become increasingly developed and used in recent years,particularly in the construction *** paper presents an analytical and numerical study of assembled CFS two single channel-shaped columns with different slenderness and configurations(backto-back,face-to-face,and box).These columns were joined by double-row rivets for the back-to-back and box configurations,whereas they were welded together for the face-to-face *** built-up columns were filled with ordinary concrete of good *** element models were applied,using ABAQUS software,to assess mechanical performance and study the influence of assembly techniques on the behavior of cold-formed columns under axial *** approaches based on Eurocode 3 and Eurocode 4 recommendations for un-filled and concrete-filled columns respectively were followed for the numerical analysis,and concrete confinement effects were also considered per American Concrete Institute(ACI)standards for face-to-face and box *** obtained results indicated a good correlation between the numerical results and the proposed analytical methodology which did not exceed 8%.The failure modes showed that the columns failed due to instabilities such as local and global buckling.

关键词： Cold-formed steel built-up sections slenderness rivets welded axial compression analytical approaches confinement buckling

Aqueous electrocatalytic N2 reduction under ambient conditions

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nano Research 2018年第6期11卷 2992-3008页

作者： na Cao Gengfeng Zheng Laboratory of Advanced Materials Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials Collaborative Innovation Center of Chemistry for Energy Materials Fudan University Shanghai200438 China

Recently, the electrochemical N2 reduction reaction （NRR） in aqueous electrolytes at ambient temperature and pressure has demonstrated its unique advantages and potentials. The reactants are directly derived from gaseous N2 and water, which are naturally abundant, and NH3 production is important for fertilizers and other industrial applications. To improve the conversion yield and selectivity （mainly competing with water reduction）, electrocatalysts must be rationally designed to optimize the mass transport, chemisorption, and transduction pathways of protons and electrons. In this review, we summarize recent progress in the electrochemical NRR. Studies of electrocatalyst designs are summarized for different categories, including metal-based catalysts, metal oxide-derived catalysts, and hybrid catalysts. Strategies for enhancing the NRR performance based on the facet orientation, metal oxide interface, crystallinity, and nitrogen vacancies are presented. Additional system designs, such as lithium-nitrogen batteries, and the solvent effect are introduced. Finally, existing challenges and prospects are discussed.

关键词： N2 reduction electrocatalyst aqueous electrolyte faradaic efficiency

One Step Positive Approach for Sheet Metal Forming Simulation Based on Quasi-conjugate-gradient Method

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Chinese Journal of Mechanical Engineering 2013年第4期26卷 730-736页

作者： na Jingxin CHEN Wei State Key Laboratory of Automotive Simulation and Control Jilin University

In one step inverse finite element approach, an initial blank shape is normally predicted from the final deformed shape. The final deformed shape needs to be trimmed into a final part after stamping, the trimmed area, therefore, needs to be compensated manually before using one step inverse approach, which causes low efficiency and in consistency with the real situation. To solve this problem, one step positive approach is proposed to simulate the sheet metal stamping process. Firstly the spatial initial solution of one step positive method is preliminarily obtained by using the mapping relationship and area coordinates, then based on the deformation theory the iterative solving is carried out in three-dimensional coordinate system by using quasi-conjugate-gradient method. During iterative process the contact judgment method is introduced to ensure that the nodes on the spatial initial solution are not separated from die surface. The predicted results of sheet metal forming process that include the shape and thickness of the stamped part can be obtained after the iterative solving process. The validity of the proposed approach is verified by comparing the predicted results obtained through the proposed approach with those obtained through the module of one step inverse approach in Autoform and the real stamped part. In one step positive method, the stamped shape of regular sheet can be calculated fast and effectively. During the iterative solution, the quasi-conjugate-gradient method is proposed to take the place of solving system of equations, and it can improve the stability and precision of the algorithm.

关键词： positive approach deformation theory quasi-conjugate-gradient method

Improved scheme with cooperative diversity based on distributed space-time block coding

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Journal of Systems Engineering and Electronics 2009年第3期20卷 463-469页

作者： Du na Xu Dazhuan Coll. of Information Science & Technology Nanjing Univ. of Aeronautics and Astronautics Nanjing 210016 P. R. China

An improved scheme with cooperative diversity based on distributed space-time block coding （WCD- DSTBC） is proposed, which effectively achieves diversity gains and improves the performance of the system by sharing some single-antenna users＇ antennas to form a virtual antenna array and combining with distributed spacetime block coding （DSTBC） mode. Then the relation between the system BER and the interuser BER for WCDDSTBC scheme is theoretically derived and the closed-form expression of BER for WCD-DSTBC system is obtained. The simulation results show that the proposed WCD-DSTBC scheme achieves distinct gains over the non-cooperative multi-carrier CDMA （MC-CDMA） system. When system BER is le-3 and interuser BER is le-3, about 2.5 dB gain can be gotten. When interuser channel state information （CSI） outgoes the users＇ individual CSI, about 3 dB gain is also achieved.

关键词： multiple input multiple output cooperative diversity distributed space-time block coding multicarrier CDMA.

Automatic image enhancement by learning adaptive patch selection

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Frontiers of Information Technology & Electronic Engineering 2019年第2期20卷 206-221页

作者： na LI Jian ZHANG School of Science and Technology Zhejiang International Studies University

Today, digital cameras are widely used in taking photos. However, some photos lack detail and need enhancement. Many existing image enhancement algorithms are patch based and the patch size is always fixed throughout the image. Users must tune the patch size to obtain the appropriate enhancement. In this study,we propose an automatic image enhancement method based on adaptive patch selection using both dark and bright channels. The double channels enhance images with various exposure problems. The patch size used for channel extraction is selected automatically by thresholding a contrast feature, which is learned systematically from a set of natural images crawled from the web. Our proposed method can automatically enhance foggy or under-exposed/backlit images without any user interaction. Experimental results demonstrate that our method can provide a significant improvement in existing patch-based image enhancement algorithms.

关键词： Image enhancement Contrast enhancement Dark channel Bright channel Adaptive patch based processing

Analytical Criteria for Local Activity of CNN with Two-port and Application to Biochemical Model

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International Journal of Minerals,Metallurgy and Materials 2000年第4期14卷 305-314页

作者： Lequan Min na Yu Applied Science School University of Science and Technology BeijingBeijing 100083China

The analytic criteria are presented for the local activity theory in two-port Cellular Neural Network (CNN) cells with three local state variables, and the application to a Biochemical Model CNN (BMCNN) is given for coupling in series of two enzymes whose prototype was studied by Decroly and Goldbeter. The bifurcation diagrams of the BMCNN's show that there does not exist a locally passive domain, and the computer simulation exhibited that convergent patterns, oscillatory patterns or chaotic patterns may emerge if the selected cell parameters are located in locally active unstable domains but nearby the edge of chaos domain. In particular, the coexistence of multiple oscillations was observed in the corresponding triple cell couples of the BMCNN's with the same initial conditions.

关键词： Cellular neural networks

Lateral Flight Stability of Two Hovering Model Insects

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Journal of Bionic Engineering 2014年第3期11卷 439-448页

作者： na Xu Mao Sun Ministry-of-Education Key Laboratory of Fluid Mechanics Beihang University Beijing 100191 P. R. China

The longitudinal disturbance motion of different insects at hovering flight has the same modal structure. Here, we consider the case of lateral motion. The lateral dynamic flight stability of two model insects, hoverfly and honeybee, at hovering flight is studied. The method of computational fluid dynamics is applied to compute the stability derivatives. The techniques of eigenvalue and eigenvector analysis are used to solve the equations of motion. Results show that the lateral disturbance motion of the hoverfly has three natural modes of motion： an unstable divergence mode, a stable oscillatory mode and a stable subsidence mode, and the flight is unstable; while the honeybee has a different modal structure （a stable slow subsidence mode, a stable fast subsidence mode, and a nearly neutrally stable oscillatory mode） and the flight is nearly neutrally stable. The change in modal structure between the two insects is due to their roll-moment/side-velocity derivative having different sign, and the sign difference is because that the hoverfly has a relatively small, but the honeybee has a relatively large, distance between the wing roots and the center of mass. Thus, unlike the case of longitudinal motion, for lateral motion, some insects have different modal structures and stability properties from others.

关键词： insect hovering flight dynamic flight stability modal structure