检索结果-南通市图书馆

Porous polymer microsphere functionalized with benzimidazolium based ionic liquids as effective solid catalysts for esterification

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2019年第10期27卷 2455-2466页

作者： Xiaomei Ling yiwei xie Xiaocheng Lin Ling Li Ting Qiu School of Chemical Engineering Fuzhou UniversityFuzhou 350116FujianChina

To prepare polymer supported ionic liquids(PSILs)as effective catalysts for esterification,the free radical suspension copolymerization of vinylbenzyl chloride(VBC,monomer),styrene(St,monomer)and divinylbenzene(DVB,crosslinker)with the addition of n-heptane(porogen)was carried out for the fabrication of the porous polymer(PVD)microsphere as support,followed by the immobilization of sulfonic acid-functionalized ionic liquids by the successive treatment of benzimidazole(BIm),1,3-propane sultone and sulfuric acid(H2SO4)or trifluoromethanesulfonic acid(CF3SO3H).The effects of the compositions of DVB and n-heptane on the internal structure of the polymer supports were investigated,and it was found that the support with 40 wt%DVB and 60 wt%n-heptane(with relative to the monomer)could endow the final PSILs with the relatively optimal catalytic performance.The preliminary experiment in the batch reactor indicated that PSILs herein exhibited higher catalytic activities than commercial Amberlyst 46 resin for the esterification of propanoic acid(PROAc)with n-propanol(PROOH).Consequently,the optimal PSILs catalyst,PVD-[Bim-SO3H]HSO4,was selected for further study in the batch reactive distillation column because of low cost and its ease of preparation.The yield of propyl ropionate(PROPRO)could reach up to 97.78%at the optimized conditions of PROOH/PROAc molar ratio(2:1)and catalyst dosage(2.0 wt%).The investigation of the reaction kinetic manifested that the calculated results of second order pseudo-homogeneous kinetic model were in good agreement with experimental values.The pre-exponential factor and activation energy were 4.12×107 L·mol-1·min-1 and 60.57 k J·mol-1,respectively.It is worth noting that the PSILs catalyst could be simply recovered and reused with relatively satisfactory decrease in the catalytic activity,which made it an environmental friendly and promising catalyst in the industrial application.

关键词： Supported ionic liquids Porous polymer microsphere Copolymerization Esterification Reactive distillation

Low-loss chip-scale programmable silicon photonic processor

在线全文

学校读者我要写书评

暂无评论

Opto-Electronic Advances 2023年第3期6卷 25-41页

作者： yiwei xie Shihan Hong Hao Yan Changping Zhang Long Zhang Leimeng Zhuang Daoxin Dai Centre for Optical and Electromagnetic Research State Key Laboratory for Modern Optical InstrumentationZhejiang Provincial Key Laboratory for Sensing TechnologiesZhejiang UniversityZijingang CampusHangzhou 310058China Imec USA Nanoelectronics Design CenterInc.194 Neocity WayKissimmeeFL34744USA Ningbo Research Institute Zhejiang UniversityNingbo 315100China

Chip-scale programmable optical signal processors are often used to flexibly manipulate the optical signals for satisfying the demands in various applications,such as lidar,radar,and artificial intelligence.Silicon photonics has unique advantages of ultra-high integration density as well as CMOS compatibility,and thus makes it possible to develop large-scale programmable optical signal processors.The challenge is the high silicon waveguides propagation losses and the high calibration complexity for all tuning elements due to the random phase errors.In this paper,we propose and demonstrate a programmable silicon photonic processor for the first time by introducing low-loss multimode photonic waveguide spirals and low-random-phase-error Mach-Zehnder switches.The present chip-scale programmable silicon photonic processor comprises a 1×4 variable power splitter based on cascaded Mach-Zehnder couplers(MZCs),four Ge/Si photodetectors,four channels of thermally-tunable optical delaylines.Each channel consists of a continuously-tuning phase shifter based on a waveguide spiral with a micro-heater and a digitally-tuning delayline realized with cascaded waveguide-spiral delaylines and MZSs for 5.68 ps time-delay step.Particularly,these waveguide spirals used here are designed to be as wide as 2μm,enabling an ultralow propagation loss of 0.28 dB/cm.Meanwhile,these MZCs and MZSs are designed with 2-μm-wide arm waveguides,and thus the random phase errors in the MZC/MZS arms are negligible,in which case the calibration for these MZSs/MZCs becomes easy and furthermore the power consumption for compensating the phase errors can be reduced greatly.Finally,this programmable silicon photonic processor is demonstrated successfully to verify a number of distinctively different functionalities,including tunable time-delay,microwave photonic beamforming,arbitrary optical signal filtering,and arbitrary waveform generation.

关键词： silicon photonics programmable photonic integrated circuit waveguide delay lines Mach-Zehnder interferometer

双链RNA依赖的蛋白激酶与阿尔茨海默病相关性研究进展

在线全文

学校读者我要写书评

暂无评论

中国医学科学院学报 2024年第3期46卷 425-434页

作者：龚奕肖星洋胡有生谢义炜伍知辉南昌大学抚州医学院江西抚州344000 南昌大学抚州医学院慢病研究重点实验室江西抚州344000 井冈山大学医学部江西吉安343009

阿尔茨海默病(AD)是一种严重威胁人类健康的疾病,也是引起人类死亡的三大因素之一。双链RNA依赖的蛋白激酶(PKR)又称为前炎症细胞因子,是人类先天免疫干扰素刺激因子之一。在AD发生和发展中,PKR表达上调并持续激活,一方面引发脑组织细... 详细信息

阿尔茨海默病(AD)是一种严重威胁人类健康的疾病,也是引起人类死亡的三大因素之一。双链RNA依赖的蛋白激酶(PKR)又称为前炎症细胞因子,是人类先天免疫干扰素刺激因子之一。在AD发生和发展中,PKR表达上调并持续激活,一方面引发脑组织细胞发生整合应激反应,另一方面间接上调β位淀粉样前体蛋白裂解酶1的表达,促进β淀粉样蛋白(Aβ)的积累,而Aβ的积累又可以激活PKR,进一步促进Aβ的积累,形成一个Aβ持续积累的循环。PKR还可以促进Tau蛋白磷酸化,降低神经细胞微管稳定性。脑组织炎症反应、Aβ的积累所引起神经毒性和微管稳定性的破坏会导致AD发生发展,引起患者记忆和认知的下降,因此PKR是AD发生发展中的关键分子。有效进行PKR检测可以预测AD进展,为临床治疗AD提供先机。目前PKR已成为研发治疗AD药物的靶点,因此靶向PKR的抑制剂有望控制PKR的活性,从而有效控制AD发生发展。

关键词：阿尔茨海默病双链RNA依赖的蛋白激酶 β淀粉样蛋白 Tau蛋白

Ultrahigh-Q silicon racetrack resonators

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

Photonics Research 2020年第5期8卷 684-689页

作者： LONG ZHANG LANLAN JIE MING ZHANG YI WANG yiwei xie YAOCHENG SHI DAOXIN DAI State Key Laboratory for Modern Optical Instrumentation Center for Optical&Electromagnetic ResearchCollege of Optical Science and EngineeringInternational Research Center for Advanced PhotonicsZhejiang UniversityHangzhou 310058China Ningbo Research Institute Zhejiang UniversityNingbo 315100China

An ultrahigh-Q silicon racetrack resonator is proposed and demonstrated with uniform multimode silicon photonic waveguides.It consists of two multimode straight waveguides connected by two multimode waveguide bends(MWBs).In particular,the MWBs are based on modified Euler curves,and a bent directional coupler is used to achieve the selective mode coupling for the fundamental mode and not exciting the higher-order mode in the racetrack.In this way,the fundamental mode is excited and propagates in the multimode racetrack resonator with ultralow loss and low intermode coupling.Meanwhile,it helps achieve a compact 180°bend to make a compact resonator with a maximized free spectral range(FSR).In this paper,for the chosen 1.6μm wide silicon photonic waveguide,the effective radius Reffof the designed 180°bend is as small as 29μm.The corresponding FSR is about 0.9 nm when choosing 260μm long straight waveguides in the racetrack.The present high-Q resonator is realized with a simple standard single-etching process provided by a multiproject wafer foundry.The fabricated device,which has a measured intrinsic Q-factor as high as 2.3×10~6,is the smallest silicon resonator with a>106Q-factor.

关键词： resonator waveguide mode

Wavelength-selective 2 × 2 optical switch based on a Ge2Sb2Te5-assisted microring

在线全文

学校读者我要写书评

暂无评论

Photonics Research 2020年第7期8卷 1171-1176页

作者： Changping Zhang Ming Zhang yiwei xie Yaocheng Shi Rajesh Kumar Roberto R.Panepucci Daoxin Dai State Key Laboratory for Modern Optical Instrumentation Center for Optical&Electromagnetic ResearchCollege of Optical Science and EngineeringInternational Research Center for Advanced PhotonicsZhejiang UniversityHangzhou 310058China Ningbo Research Institute Zhejiang UniversityNingbo 315100China Department of Physics Indian Institute of Technology RoorkeeRoorkee-247667 UttarakhandIndia Centro de Tecnologia da Informação Renato Archer-CTI Rodovia Dom Pedro Ikm 1436Campinas 13069-901São PauloBrazi

A novel wavelength-selective 2×2 optical switch based on a Ge2Sb2Te5(GST)-assisted microring-resonator(MRR)is proposed.The present GST-assisted MRR consists of two access optical waveguides and an MRR coupled with a bent GST-loaded silicon photonic waveguide.The 2×2 optical switch is switched ON or OFF by modifying the GST state to be crystalline or amorphous.In particular,the microring waveguide and the bent GST-loaded waveguide are designed to satisfy the phase-matching condition when the GST is crystalline.As a result,the MRR becomes highly lossy and the resonance peak is depressed significantly.On the other hand,when it is off,there is little coupling due to the significant phase mismatching.Consequently,one has a low-loss transmission at the drop port for the resonance wavelength.In this paper,the simulation using the three-dimensional finite-difference method shows that the extinction ratio of the designed photonic switch is^20 d B at the resonance wavelength,while the excess losses at the through port and drop port are 0.9 d B and 2 d B.In particular,the resonance wavelength changes little between the ON and OFF states,which makes it suitable for multichannel wavelength-division-multiplexing systems.

关键词： crystalline optical loaded

Silicon nonlinear switch as a conditional circulator for monostatic LiDAR systems

在线全文

学校读者我要写书评

暂无评论

Photonics Research 2022年第2期10卷 426-432页

作者： Mingfei Ding yiwei xie Hao Yan Abu Naim R.Ahmed Reza Safian Swapnajit Chakravarty Leimeng Zhuang Pengcheng Jiao Huan Li Liu Liu Daoxin Dai Centre for Optical and Electromagnetic Research State Key Laboratory for Modern Optical InstrumentationZhejiang Provincial Key Laboratory for Sensing TechnologiesZhejiang UniversityZijingang CampusHangzhou 310058China Ningbo Research Institute Zhejiang UniversityNingbo 315100China imec USA Nanoelectronics Design CenterInc.KissimmeeFlorida 34744USA Ocean College Zhejiang UniversityZhoushan 316021China

All-optical silicon-photonics-based LiDAR systems allow for desirable features in scanning resolution and speed,as well as leverage other advantages such as size, weight, and cost. Implementing optical circulators in silicon photonics enables bidirectional use of the light path for both transmitters and receivers, which simplifies the system configuration and thereby promises low system cost. In this work, to the best of our knowledge, we present the first experimental verification of all-passive silicon photonics conditional circulators for monostatic LiDAR systems using a nonlinear switch. The proposed silicon nonlinear interferometer is realized by controlling signal power distribution with power-splitting circuits, allowing the LiDAR transmitter and receiver to share the same optical path. Unlike the traditional concept requiring a permanent magnet, the present device is implemented by using common silicon photonic waveguides and a standard foundry-compatible fabrication process. With several additional phase shifters, the demonstrated device exhibits considerable flexibility using a single chip, which can be more attractive for integration with photodetector arrays in LiDAR systems.

关键词： interferometer LiDAR nonlinear

在线全文

学校读者我要写书评

暂无评论

暗河发育区岩溶隧道突涌水洪峰流量估计

中国水利水电科学研究院学报（中英文） 2024年第3期22卷 307-317,323页

作者：谢艺伟李开军张鹏郭子昊张翾中交一公局厦门工程有限公司厦门361000 南京工业大学交通运输工程学院南京211816 交通部公路科学研究所北京100088

地下暗河是岩溶隧道建设与运营重大的安全风险,暗河发育区岩溶隧道突涌水洪峰估计是岩溶隧道施工抢险与后期处治方案制定的重要基础数据。地下暗河洪峰流量不仅由岩溶区水文地质条件控制,而且还受到暴雨期地表径流补给的影响。本文结合... 详细信息

地下暗河是岩溶隧道建设与运营重大的安全风险,暗河发育区岩溶隧道突涌水洪峰估计是岩溶隧道施工抢险与后期处治方案制定的重要基础数据。地下暗河洪峰流量不仅由岩溶区水文地质条件控制,而且还受到暴雨期地表径流补给的影响。本文结合实测数据和统计数据,围绕小流域暴雨资料推求出地表汇流洪峰和地下暗河汇泄流洪峰,提出了一种考虑地表径流补给的暗河发育区岩溶隧道突涌水洪峰估计方法,并结合翠屏隧道的地形地貌、水文地质与实测涌水资料,开展了案例分析计算并比较实测涌水量。表明传统涌水预测方法无法考虑暗河与地表水补给的影响,与实测结果差距很大,本方法能够较好预测岩溶区因地表汇水补给暗河发育区隧道突涌水洪峰,为隧道防洪护堤高度、涵管过水容量设计、洪峰避险时间提供重要支撑,保障隧道施工与运营安全。

关键词：岩溶隧道地下暗河径流补给突涌水洪峰流量

维普期刊数据库博看期刊

Sub-nanosecond-speed frequency-reconfigurable photonic radio frequency switch using a silicon modulator

在线全文

学校读者我要写书评

暂无评论

Photonics Research 2020年第6期8卷 852-857页

作者： yiwei xie LEIMENG ZHUANG PENGCHENG JIAO DAOXIN DAI Centre for Optical and Electromagnetic Research State Key Laboratory for Modern Optical InstrumentationZhejiang Provincial Key Laboratory for Sensing TechnologiesZhejiang UniversityHangzhou 310058China Institute of Port Coastal and Offshore EngineeringOcean CollegeZhejiang UniversityZhoushan 316021China Engineering Research Center of Oceanic Sensing Technology and Equipment Ministry of EducationZhejiang UniversityHangzhou 310000China

Radio frequency(RF)switches are essential for implementing routing of RF signals.However,the increasing demand for RF signal frequency and bandwidth is posing a challenge of switching speed to the conventional solutions,i.e,the capability of operating at a sub-.nanosecond speed or faster.In addition,signal frequency reconfigurability is also a desirable feature to facilitate new innovations of flexible system functions.Utilizing microwave photonics as an alter-native path,we present here a photonic implementation of an RF switch providing not only the capability of switching at a sub-nanosecond speed but also options of frequency doubling of the input RF signals,allowing for flexible output waveforms.The core device is a traveling wave silicon modulator with a device size of0.2 mm × 1.8 mm and a modu-lation bandwidth of 10 GHz.Using microwave frequencies,i.e.,15 GHz and 20 GHz,as two simultaneous RF input signals,we experimentally demonstrated their amplitude and frequency switching as well as that of the doubled frequencies,ie,30 GHz and 40 GHz,at a switching frequency of 5 GHz.The results of this work point to a solution for creating high speed RF switches with high compactness and flexibility.

关键词： modulator microwave doubling

Tunable and programmable fiber ring laser based on digital-controlled chirped fiber Bragg grating

在线全文

学校读者我要写书评

暂无评论

Frontiers of Optoelectronics 2013年第4期6卷 468-471页

作者： Huiqi LIAO Ming TANG Hailiang ZHANG yiwei xie National Engineering Laboratory of Next Generation lntemet Access Networks (NGIA) School of Optical and Electronic Information Huazhong University of Science and Technology Wuhan 430074 China

This paper proposed and experimentally demonstrated an all-fiber tunable and programmable bandpass filter using a linearly chirped fiber Bragg grating （CFBG）. The center wavelength and spacing of the transmission peaks could be independently tuned via computer. The tunable range is about 18 rim. With this filter we demonstrated a tunable fiber ring laser which has an output power of about -7 dBm, full-width at half- maximum linewidth of-0.017 nm which is limited by the resolution of the optical spectrum analyzer （OSA）. Furthermore, a spacing tunable dual-wavelength fiber laser was achieved with the same setup. This all-fiber laser features advantages like simple structure, low cost, flexible and digital tuning capability.

关键词： chirped fiber Bragg grating （CFBG） tunablefilter fiber ring laser phase shift