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Photonic generation of triangular and rectangular waveforms based on four-wave mixing effect

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Optoelectronics Letters 2022年第1期18卷 6-12页

作者： YUAN Jin WANG Yujie ZHANG Hui ZHANG Mengsi LI Zengrui State Key Laboratory of Media Convergence and Communication Communication University of ChinaBeijing 100044China

A photonic approach that can generate triangular and rectangular waveforms is proposed.A dual-electrode Mach-Zehnder modulator(De-MZM)is used to fulfill the external optical carrier suppression(OCS)modulation of a continuous wave(CW).The follow-up four-wave mixing(FWM)in a semiconductor optical amplifier(SOA)makes four primary sidebands exist in the spectrum.Then filtering and optical carrier recovery techniques are used to construct the spectrum aligning with that of a triangular/rectangular waveform.In this work,we also elaborate the influence of errors of key device parameters,by which the feasibility and stability of the system have been verified.Based on this photonic approach,a 10 GHz full-duty-cycle triangular waveform and a 50%-duty-cycle rectangular waveform are successfully obtained.This approach provides a feasible method to generate multiple waveforms.

关键词： spectrum. triangular rectangular

Research on wavelength conversion of triangular pulses with variable symmetry based on SPM effect

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Optoelectronics Letters 2023年第8期19卷 449-454页

作者： YUAN Jin LIU Qisong MEI Ying XU Xiuxiu WANG Yujie BA Xinran State Key Laboratory of Media Convergence and Communication Communication University of ChinaBeijing 100044China

The generation of periodic triangular waveform with variable symmetrical coefficient based on a dual-parallel Mach-Zehnder modulator(DP-MZM) is demonstrated in this work.By properly setting the modulation index and bias points of DP-MZM,desired symmetric/asymmetric triangular waveforms can be generated.Then applying the generated triangular waveform into an amplitude modulator(AM),a single-period signal can be extracted to explore the optical wavelength conversion induced by the self-phase modulation(SPM) effect in a high nonlinear fiber(HNLF).Wavelength shifts of triangular waveforms with different coefficients(10%,20%,30%,40% and 50%) are calculated.In addition,the influence of key parameters of HNLF on the wavelength conversion is analyzed in detail.

关键词： modulator triangular effect

Performance study of optical triangular-shaped pulse generation with full duty cycle

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Chinese Optics Letters 2017年第11期15卷 10-14页

作者：郝泽李晶王创业袁瑾 Key Lab of All Optical Network & Advanced Telecommunication Network of EMC Beijing giaotong University Beijing 100044 China

A scheme of triangular-shaped pulses with full duty cycle generation is proposed and analyzed.Benefiting from the feature of orthogonal polarization,two approximate sinusoidal signals on different polarization states can be combined without inducing coherent interference.By tuning the time mismatching between the two signals,an approximately triangular-shaped profile can be obtained in the optical intensity.It is found that the modulation index β is no longer a fixed one,but it can be aligned within a proper range of 0.92 to 1.57.To evaluate the proposal,impacts of radio frequency voltage fluctuation,bias voltage drift,and time mismatching are discussed.Within the defined fitting error（η≤ 3%）,the tolerable range of the modulation index,time mismatching,and voltage have been found,which insures a simple operation in practice.

关键词： triangular shaped fitting aligned coherent fluctuation drift tuning cycle proposal

Phonon Focusing Effect in an Atomic Level triangular Structure

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Chinese Physics Letters 2023年第9期40卷 61-65页

作者：姜剑辉鲁爽陈杰 Center for Phononics and Thermal Energy Science China–EU Joint Lab for NanophononicsMOE Key Laboratory of Advanced Micro-structured MaterialsSchool of Physics Science and EngineeringTongji UniversityShanghai 200092China

The rise of artificial microstructures has made it possible to modulate propagation of various kinds of waves,such as light,sound and heat.Among them,the focusing effect is a modulation function of particular interest.We propose an atomic level triangular structure to realize the phonon focusing effect in single-layer graphene.In the positive incident direction,our phonon wave packet simulation results confirm that multiple features related to the phonon focusing effect can be controlled by adjusting the height of the triangular structure.More interestingly,a completed different focusing pattern and an enhanced energy transmission coefficient are found in the reverse incident direction.The detailed mode conversion physics is discussed based on the Fourier transform analysis on the spatial distribution of the phonon wave packet.Our study provides physical insights to achieving phonon focusing effect by designing atomic level microstructures.

关键词： structure phonon triangular

Azimuthal vector beam exciting silver triangular nanoprisms for increasing the performance of surface-enhanced Raman spectroscopy

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Photonics Research 2019年第12期7卷 1447-1453页

作者： LU ZHANG WENDING ZHANG FANFAN LU ZHIQIANG YANG TIANYANG XUE MIN LIU CHAO MENG PENG LI DONG MAO TING MEI JIANLIN ZHAO MOE Key Laboratory of Material Physics and Chemistry under Extraordinary Conditions and Shaanxi Key Laboratory of Optical Information Technology School of Science Northwestern Polytechnical University

Surface-enhanced Raman spectroscopy(SERS)with high-sensitivity performance is a very necessary detection technology.Here,we present a method for increasing the performance of SERS based on silver triangular nanoprism arrays(ATNAs)vertically excited via a focused azimuthal vector beam(AVB).The ATNA substrates with different structural parameters are prepared based on the traditional self-assembled and modified film lift-off technique.Based on a theoretical model established adopting the structural parameters of the ATNA substrates,theoretical simulation results show that AVB excitation can achieve greater electric-field enhancement than linearly polarized beam(LPB)excitation.Experimental result indicates that SERS sensitivity obtained via AVB excitation is 10^-13M(1 M=1 mol/L)using rhodamine 6 G(R6 G)as the target analyte,which is 2 orders of magnitude lower than that of LPB excitation(10^-11M).Meanwhile,the uniformity and reproducibility of the ATNA substrates are examined using Raman mapping and batch-to-batch measurement,respectively,and the Raman enhancement factor is calculated to be^3.3×10^7.This method of vector light field excitation may be used to improve the SERS performance of the substrates in fields of ultra-sensitive Raman detection.

关键词： excitation silver triangular

The closures of (U+K)-orbits of essentially normal triangular operator models

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Science China Mathematics 2010年第11期53卷 1045-1066页

作者： ZHAI FaHui 1,& GUO XianZhou 2 1 Department of Mathematics,Qingdao University of Science and Technology,Qingdao 266061,China 2 School of Sciences,Hebei University of Technology,Tianjin 300401,China Department of Mathematics Qingdao University of Science and Technology Qingdao China School of Sciences Hebei University of Technology Tianjin China

The (U + K)-orbit of a bounded linear operator T acting on a Hilbert space H is defined as (U + K)(T)={R-1 T R:R is invertible of the form unitary plus compact on H}.In this paper,we first characterize the closure of the (U + K)-orbit of an essentially normal triangular operator T satisfying H={ker(T-λI):λ∈ρ F (T)} and σ p (T*)=ф.After that,we establish certain essentially normal triangular operator models with the form of the direct sums of triangular operators,adjoint of triangular operators and normal operators,show that such operator models generate the same closed (U + K)-orbit if they have the same spectral picture,and describe the closures of the (U + K)-orbits of these operator models.These generalize some known results on the closures of (U + K)-orbits of essentially normal operators,and provide more positive cases to an open conjecture raised by Marcoux as Question 2 in his article "A survey of (U + K)-orbits".

关键词： (U+K)-orbit essentially normal operator triangular operator

Characterization of Obtuse triangular Defects on 4H-SiC 4° off-Axis Epitaxial Wafers

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Chinese Physics Letters 2013年第9期30卷 109-111页

作者：董林孙国胜俞军郑柳刘兴昉张峰闫果果李锡光王占国杨霏 Key Laboratory of Semiconductor Materials Science Institute of SemiconductorsChinese Academy of SciencesBeijing 100083 Dongguan Tianyu Semiconductor Inc.Dongguan 523000 State Grid Smart Grid Research Institute Beijing 100192

We investigate the triangular defects with different structural features on 4H-SiC epilayers by a Nomarski micro-scope,a Candela optical surface analyzer and ultraviolet photoluminescence(UV-PL)imaging.Both the foreign particles and the substrate scratches can cause the formation of the obtuse triangular defects.The central area of some obtuse triangular defects can have the spatially confined core,in which the in-grown stacking faults can be observed under the UV-PL imaging.In contrast,the obtuse triangular defects induced by the scratches appear in the form of band-like defects,of which the width depends on the scratch direction and reaches the maximum when the scratch direction is parallel to the step flow direction.The formation mechanisms of these obtuse triangular defects are discussed.

关键词： triangular Epitaxial ultraviolet

Preparation, Structures and Magnetic Properties of Two Co-based Clusters with triangular Core and Cuboidal Core Geometries

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Chinese Journal of Structural Chemistry 2019年第11期38卷 1934-1939页

作者：李启彭沈燕琼钱金杰 Science and Technology Department Zhaotong UniversityZhaotong 657000China Agricultural Product Quality and Safety Center of Zhaotong Zhaotong 657000China College of Chemistry and Materials Engineering Wenzhou UniversityWenzhou 325035China

Two novel Co-based clusters with the 2-(hydroxylmethyl)pyridine(hmpH)ligand,formulated as[Co3(hmp)6(hmpH)]×2NO3×3H2O(ZTU-3)and[Co4(hmp)4(CH3CO2)2(H2O)4]×2NO3(ZTU-4),have been successfully synthesized and structurally characterized.ZTU-3 features a triangular core geometry,while ZTU-4 exhibits a cuboidal core geometry.In addition,the magnetic properties of ZTU-3 and ZTU-4 are also all investigated.

关键词： Co-based clusters triangular core cuboidal magnetic property

Development and Application of a High-Performance triangular Shell Element and an Explicit Algorithm in OpenSees for Strongly Nonlinear Analysis

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Computer Modeling in Engineering & Sciences 2019年第9期120卷 561-582页

作者： Xinzheng Lu Yuan Tian Chujin Sun Shuhao Zhang Key Laboratory of Civil Engineering Safety and Durability of China Education Ministry Department of Civil EngineeringTsinghua UniversityBeijing100084China Beijing Engineering Research Center of Steel and Concrete Composite Structures Tsinghua UniversityBeijing100084China.

The open-source finite element software,OpenSees,is widely used in the earthquake engineering community.However,the shell elements and explicit algorithm in OpenSees still require further improvements.Therefore,in this work,a triangular shell element,NLDKGT,and an explicit algorithm are proposed and implemented in OpenSees.Specifically,based on the generalized conforming theory and the updated Lagrangian formulation,the proposed NLDKGT element is suitable for problems with complicated boundary conditions and strong nonlinearity.The accuracy and reliability of the NLDKGT element are validated through typical cases.Furthermore,by adopting the leapfrog integration method,an explicit algorithm in OpenSees and a modal damping model are developed.Finally,the stability and efficiency of the proposed shell element and explicit algorithm are validated through the nonlinear time-history analysis of a highrise building.

关键词： triangular shell element explicit algorithm OpenSees strong nonlinearity