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Creation of multi-frequency terahertz waves by optimized cascaded difference frequency generation

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Chinese Physics B 2022年第4期31卷 356-360页

作者： Zhong-Yang Li Jia Zhao Sheng Yuan Bin-Zhe Jiao Pi-Bin Bing Hong-Tao Zhang Zhi-Liang Chen Lian Tan jian-quan yao College of Electric Power North China University of Water Resources and Electric PowerZhengzhou 450045China College of Precision Instrument and Opto-electronics Engineering Institute of Laser and Opto-electronicsTianjin UniversityTianjin 300072China

A new scheme which generates multi-frequency terahertz(THz)waves from planar waveguide by the optimized cascaded difference frequency generation(OCDFG)is proposed.A THz wave with frequencyω_(T1)is generated by the OCDFG with two infrared pump waves,and simultaneously a series of cascaded optical waves with a frequency intervalω_(T1)is *** THz wave with a frequency of M-timesω_(T1)is generated by mixing the m-th-order and the(m+M)-th-order cascaded optical *** phase mismatch distributions of cascaded difference frequency generation(CDFG)are modulated by changing the thickness of planar waveguide step by step,thereby satisfying the phase-matching condition from first-order to high-order cascaded Stokes process step by *** a result,the intensity of THz wave can be enhanced and modulated by controlling the cascading order of OCDFG.

关键词： multi-frequency terahertz wave optimized cascaded difference frequency generation planar waveguide

Synergistic silver-mediated and palladium-catalyzed nondirected olefination of aryl C–H bond: quick access to multi-substituted aryl olefins

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Science China Chemistry 2024年第3期67卷 882-889页

作者： jian yao Lili Shao Xiaohong Huo Xiaoming Wang Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs Frontiers Science Center for Transformative MoleculesSchool of Chemistry and Chemical EngineeringShanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Organometallic Chemistry Center for Excellence in Molecular SynthesisShanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 20032China School of Chemistry and Materials Science Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of SciencesHangzhou 310024China

Transition metal-catalyzed olefination of aryl C-H bond is a powerful tool for the synthesis of alkenes. While the Pd-catalyzed oxidative C-H olefination of arenes, also known as Fujiwara-Moritani reaction, has been established as one of the most efficient methods, the substrates are largely limited to terminal olefins with electron-withdrawing group(s). Herein, we report a synergistic silver-mediated and palladium-catalyzed non-directed C-H olefination of arenes with vinyl(pseudo)halides, which offers a complementary strategy to the typical Fujiwara-Moritani reaction. The reactions proceeded well for a variety of halogenated arenes, heteroarenes, and olefin substrates, providing an efficient access to various multi-substituted aryl olefins, including trisubstituted/tetrasubstituted olefins and several complex olefins derived from medicines or natural products. Mechanistic studies indicated a bimetallic Pd/Ag cooperation is operative in the catalysis, i.e., the reaction is initiated by aryl C-H bond cleavage via ligation with phosphine/Ag species, followed by transferring of the aryl moiety to a vinyl palladium intermediate,which is in turn formed by oxidative addition of vinyl(pseudo)halide to a Pd complex. This method enables the synthesis of a wide range of challenging multi-substituted vinyl products from simple arenes(directing-group free) in a streamlined and controllable fashion.

关键词： direct C–H olefination multi-substituted aryl alkenes bimetallic Pd/Ag cooperation C–H functionalization

A continuous-wave Nd:YVO_(4)-KGW intracavity Raman laser with over 34% diode-to-Stokes optical efficiency

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High Power Laser Science and Engineering 2024年第2期12卷 62-68页

作者： quan Sheng Jingni Geng Tianchang Liu Shijie Fu Wei Shi jianquan yao Institute of Laser and Optoelectronics School of Precision Instrument and Optoelectronics EngineeringTianjin UniversityTianjinChina Key Laboratory of Optoelectronic Information Technology(Ministry of Education) Tianjin UniversityTianjinChina

We demonstrate a continuous-wave(CW)Nd:YVO_(4)-potassium gadolinium tungstate(KGW)intracavity Raman laser with a diode-to-Stokes optical efficiency of 34.2%.By optimizing the cavity arrangement and reducing the cavity losses,8.47 W Stokes output at 1177 nm was obtained under an incident 878.6 nm diode pump power of 24.8 *** influence of cavity losses on the power and efficiency of the CW Raman laser,as well as the potential for further optimization,was investigated based on the numerical *** observation of thermally-induced output rollover was well explained by the calculation of the thermal lensing and cavity stability,indicating that the end-face curvature played an important role when the end-face of the crystal was highly reflective coated to make the cavity.A 10.9 W Stokes output under 40.9 W incident pump was also demonstrated with a cavity arrangement less sensitive to the end-face curvature,which is the highest output power of CW intracavity Raman lasers reported.

关键词： continuous wave intracavity Raman laser KGW crystal thermal lens

Temperature-Dependent Dielectric Characterization of Magneto-Optical Tb_3Sc_2Al_3O_(12) Crystal Investigated by Terahertz Time-Domain Spectroscopy

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Chinese Physics Letters 2019年第4期36卷 31-34页

作者： Ju-Geng Li Sen-Miao Yang Xin Chen Nai-Feng Zhuang Qi-Biao Zhu An-Hua Wu Xian Lin Guo-Hong Ma Zuan-Ming Jin jian-quan yao Department of Physics College of Sciences Shanghai University College of Chemistry and Chemical Engineering Fuzhou University Shanghai Institute of Ceramics Chinese Academy of Science STU & SIOM Joint Laboratory for Superintense Lasers and the Applications College of Precision Instrument and Opto-electronics Engineering Institute of Laser and OptoelectronicsTianjin University

Terbium scandium aluminum garnet(TSAG) crystals have been widely used in magneto-optical systems. We investigate the complex refractive index of the TSAG crystal in the terahertz frequency range using terahertz(THz) time-domain spectroscopy in the temperature range 100–300 K. It is observed that the refractive index and the absorption coefficient increase with the THz frequency. The refractive index increases with the *** measure the temperature coefficient of the refractive index of the TSAG crystal in the frequency range 0.4–1.4 THz. Furthermore, the loss tangent, i.e., the ratio of experimental values of the imaginary and real part of the dielectric permittivity, is found to be almost independent of frequency. TSAG is very promising for applications in THz optoelectronics because it has a high dielectric constant, low loss, and low thermal coefficient of the dielectric constant.

关键词： Dielectric Characterization Crystal

Ligation-assisted endoscopic submucosal resection following unroofing technique for small esophageal subepithelial lesions originating from the muscularis propria

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World Journal of Gastroenterology 2024年第32期30卷 3748-3754页

作者： quan Lu quan-Zhou Peng Jun yao Li-Sheng Wang De-Feng Li Department of Gastroenterology Shenzhen People’s HospitalShenzhen 518020Guangdong ProvinceChina Department of Pathology Shenzhen People’s HospitalShenzhen 518020Guangdong ProvinceChina Department of Gastroenterology Shenzhen People’s HospitalThe Second Clinical Medical CollegeJinan UniversityShenzhen 518020Guangdong ProvinceChina The First Affiliated Hospital Southern University of Science and TechnologyShenzhen 518020Guangdong ProvinceChina

BACKGROUND The majority of esophageal subepithelial lesions originating from the muscularis propria(SEL-MPs)are benign in nature,although a subset may exhibit malignant *** endoscopic resection techniques are time-consuming and lack efficacy for small *** To evaluate the efficacy and safety of ligation-assisted endoscopic submucosal resection(ESMR-L)following unroofing technique for small esophageal *** From January 2021 to September 2023,17 patients diagnosed with esophageal SEL-MPs underwent ESMR-L following unroofing technique at the endoscopy center of Shenzhen People’s *** of clinicopathological characteristics and clinical outcomes were collected and *** The mean age of the patients was 50.12±12.65 *** mean size of the tumors was 7.47±2.83 mm and all cases achieved en bloc resection *** average operation time was 12.2 minutes without any *** identified 2 Lesions(11.8%)as gastrointestinal stromal tumors at very low risk,12 Lesions(70.6%)as leiomyoma and 3 Lesions(17.6%)as smooth muscle *** recurrence was found during the mean follow-up duration of 14.18±9.62 *** ESMR-L following roofing technique is an effective and safe technique for management of esophageal SEL-MPs smaller than 20 mm,but it cannot ensure en bloc resection and may require further treatment.

关键词： Subepithelial lesions Muscularis propria Esophagus Ligation Endoscopic submucosal resection

An 8-Node Plane Hybrid Element for StructuralMechanics Problems Based on the Hellinger-Reissner Variational Principle

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Computer Modeling in Engineering & Sciences 2024年第2期138卷 1277-1299页

作者： Haonan Li WeiWang quan Shen Linquan yao School of Rail Transportation Soochow UniversitySuzhou215131China Soochow College Soochow UniversitySuzhou215006China

The finite element method (FEM) plays a valuable role in computer modeling and is beneficial to the mechanicaldesign of various structural parts. However, the elements produced by conventional FEM are easily inaccurate andunstable when applied. Therefore, developing new elements within the framework of the generalized variationalprinciple is of great significance. In this paper, an 8-node plane hybrid finite element with 15 parameters (PHQ8-15β) is developed for structural mechanics problems based on the Hellinger-Reissner variational *** to the design principle of Pian, 15 unknown parameters are adopted in the selection of stress modes toavoid the zero energy ***, the stress functions within each element satisfy both the equilibrium andthe compatibility relations of plane stress problems. Subsequently, numerical examples are presented to illustrate theeffectiveness and robustness of the proposed finite element. Numerical results show that various common lockingbehaviors of plane elements can be overcome. The PH-Q8-15β element has excellent performance in all benchmarkproblems, especially for structures with varying cross sections. Furthermore, in bending problems, the reasonablemesh shape of the new element for curved edge structures is analyzed in detail, which can be a useful means toimprove numerical accuracy.

关键词： 8-node plane hybrid element Hellinger-Reissner variational principle locking behaviors structural mechanics problems

Contact detumbling toward a nutating target through deformable effectors and prescribed performance controller

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Journal of Systems Engineering and Electronics 2024年第3期35卷 753-768页

作者： ZANG Yue ZHANG yao HU quan LI Mou CHEN Yujun School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China China Academy of Space Technology Beijing 100029China

Detumbling operation toward a rotating target with nutation is meaningful for debris removal but challenging. In this study, a deformable end-effector is first designed based on the requirements for contacting the nutating target. A dual-arm robotic system installed with the deformable end-effectors is modeled and the movement of the end-tips is analyzed. The complex operation of the contact toward a nutating target places strict requirements on control accuracy and controller robustness. Thus, an improvement of the tracking error transformation is proposed and an adaptive sliding mode controller with prescribed performance is designed to guarantee the fast and precise motion of the effector during the contact ***, by employing the proposed effector and the controller,numerical simulations are carried out to verify the effectiveness and efficiency of the contact detumbling toward a nutating target.

关键词： nutating target contact detumbling dual-arm space robot deformable end-effector prescribed performance controller

Experimental and numerical study on protective effect of RC blast wall against air shock wave

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Defence Technology（防务技术） 2024年第1期31卷 567-579页

作者： Xin-zhe Nian quan-min Xie Xin-li Kong Ying-kang yao Kui Huang State Key Laboratory of Precision Blasting Jianghan UniversityWuhan430056China Hubei Key Laboratory of Blasting Engineering Jianghan UniversityWuhan430056China Hubei(Wuhan)Institute of Explosion and Blasting Technology Jianghan UniversityWuhan430056China College of Defense Engineering Army Engineering University of PLANanjing210007China Institute of Defense Engineering AMSPLALuoyang471023China

Prototype experiments were carried out on the explosion-proof performance of the RC blast *** mass of TNT detonated in the experiments is 5 kg and 20 kg *** shock wave overpressure was tested in different *** above experiments were numerically simulated,and the simulated shock wave overpressure waveforms were compared with that tested and given by CONWEP *** results show that the numerically simulated waveform is slightly different from the test waveform,but similar to CONWEP *** dimensional analysis and numerical simulation under different working conditions,the equation for the attenuation rate of the diffraction overpressure behind the blast wall was *** to the corresponding standards,the degree of casualties and the damage degree of the brick concrete building at a certain distance behind the wall can be determined when parameters are *** above results can provide a reference for the design and construction of the reinforced concrete blast wall.

关键词： Blast wall Shock wave Diffraction Overpressure Protection

Analysis of mechanical strengths of extreme line casing joint considering geometric, material, and contact nonlinearities

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Petroleum Science 2024年第3期21卷 1992-2004页

作者： Ji-Yun Zhang Chi Peng jian-Hong Fu quan Cao Yu Su jian-Yun Pang Zi-Qiang Yu Petroleum Engineering School Southwest Petroleum UniversityChengdu610500SichuanChina Engineering Technology Research Institute of CNPC Southwest Oil and Gas Field Company Chengdu610017SichuanChina

To address the challenges associated with difficult casing running,limited annular space,and poor cementing quality in the completion of ultra-deep wells,the extreme line casing offers an effective solution over conventional ***,due to its smaller size,the joint strength of extreme line casing is reduced,which may cause failure when running in the *** address this issue,this study focuses on the CST-ZTΦ139.7 mm×7.72 mm extreme line casing and employs the elastic-plastic mechanics to establish a comprehensive analysis of the casing joint,taking into account the influence of geometric and material nonlinearities.A finite element model is developed to analyze the forces and deformations of the extreme line casing joint under axial tension and external collapse *** model investigates the stress distribution of each thread tooth subjected to various tensile forces and external ***,the tensile strength and crushing strength of the extreme line casing joint are determined through both analytical and experimental *** findings reveal that,under axial tensile load,the bearing surface of each thread tooth experiences uneven stress,with relatively high equivalent stress at the root of each thread *** end thread teeth are valuable spots for *** is observed that the critical fracture axial load of thread decreases linearly with the increase of thread tooth *** external pressure,the circumferential stress is highest at the small end of the external thread,leading to yield *** tensile strength of the joint obtained from the finite element model exhibits a relative error of less than 7%compared to the analytical and experimental values,proving the reliability of the finite element *** tensile strength of the joint is 3091.9 k ***,in terms of anti-collapse capability,the joints demonstrate higher resistance to collapse compared to the casing body,which is consistent with the test resul

关键词： Extreme line casing Elastic-plastic mechanics Finite element analysis Tensile strength Collapse strength