检索结果-南通市图书馆

Application of local polynomial estimation in suppressing strong chaotic noise

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2012年第2期21卷 181-186页

作者： Su Li-Yun Ma Yan-Ju Li Jiao-Jun school of Mathematics and Statistics Chongqing University of TechnologyChongqing 400054China school of Electronic Information and Automation Chongqing University of TechnologyChongqing 400054China

In this paper, we propose a new method that combines chaotic series phase space reconstruction and local polynomial estimation to solve the problem of suppressing strong chaotic noise. First, chaotic noise time series are reconstructed to obtain multivariate time series according to Takens delay embedding theorem. Then the chaotic noise is estimated accurately using local polynomial estimation method. After chaotic noise is separated from observation signal, we can get the estimation of the useful signal. This local polynomial estimation method can combine the advantages of local and global law. Finally, it makes the estimation more exactly and we can calculate the formula of mean square error theoretically. The simulation results show that the method is effective for the suppression of strong chaotic noise when the signal to interference ratio is low.

关键词： strong chaotic noise local polynomial estimation weak signal detection

Comparison between two autorefractor performances in large scale vision screening in Chinese school age children

在线全文

学校读者我要写书评

暂无评论

International Journal of Ophthalmology(English edition) 2020年第10期13卷 1660-1666页

作者： Di Wang Nan Jin Ru-Xia Pei Li-Qiong Zhao Bei Du Gui-Hua Liu Xi-Lian Wang Rui-Hua Wei Xiao-Rong Li tianjin International Joint Research and Development Centre of Ophthalmology and Vision Science Eye Institute and School of OptometryTianjin Medical University Eye HospitalTianjin 300384China tianjin Beichen District Hospital of Traditional Chinese Medicine Tianjin 300400China

AIM:To evaluate the effectiveness of Grand Seiko Ref/Keratometer WAM-5500 compared to Topcon KR800 autorefractor in detecting refractive error in large scale vision screening for Chinese school age children with the WHO ***:A total of 886 participants were enrolled with mean age of 9.49±1.88 y from tianjin,*** equivalent(SE)was obtained from un-cycloplegic autorefraction and cycloplegic *** KR 800(Topcon)and Grand Seiko WAM-5500(WAM)autorefractors were ***-Altman Plot and regression were generated to compare their *** overall effectiveness of detecting early stage refractive error was analyzed with receiver operating characteristic(ROC)***:The mean SE was-0.98±1.81 diopter(D)and the prevalence of myopia was 48.9%defined by WHO criteria according to the result of cycloplegic *** mean SE of un-cycloplegic autorefraction with Topcon and WAM were-1.21±1.65 and-1.20±1.68 D *** was a strong linear agreement between result obtained from WAM and cycloplegic autorefraction with an R2 of ***-Altman plot indicated a moderate agreement of cylinder values between the two *** sensitivity and specificity for detecting hyperopia were 90.52%and 83.51%;for detecting myopia were 95.60%and 90.24%;for detecting astigmatism were 79.40%and 90.21%;for detecting high myopia were 98.16%and 98.91%***:These findings suggest that both Grand Seiko and Topcon autorefractor can be used in large-scale vision screening for detecting refractive error in Chinese *** Seiko gives relatively better performance in detecting myopia,hyperopia,and high myopia for school age children.

关键词： myopia vision screening autorefraction spherical equivalent Grand Seiko WAM-5500

Technological Optimization of the Preparation of Imidacloprid

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2003年第5期11卷 604-607页

作者：闻建平王长林 school of Chemical Engineering and technology tianjin university Tianjin 300072 China

In order to reduce the production cost of imidacloprid, the preparation technology for the direct com-bination of 2-chloro-5-chloromethylpyridine and 2-nitryliminoglyoxaline has been optimized in a 10 L stirred tank reactor with a new solvent, butanone, and a new catalyst, benzyl triethyl-ammonium chloride (BTEAC), which was proved to be more profitable for the production of imidacloprid. Three main affecting factors (the reaction temper-ature, the molar ratio of BTEAC to 2-nitryliminoglyoxaline and the concentration of 2-nitryuminoglyoxaline) for the production of imidacloprid were investigated and the optimum operating conditions were found. Based on the above technological optimization, an industrial process for imidacloprid with a production capacity of 50 tons per year was put in operation using a 2500 L stirred tank reactor under the same operating conditions. Good yield and purity of imidacloprid was also obtained in the industrial production.

关键词： imidacloprid 2-chloro-5-chloromethylpyridine 2-nitryliminoglyoxaline technological optimization

Tapered photonic crystal fiber for supercontinuum generation in telecommunication windows

在线全文

学校读者我要写书评

暂无评论

Frontiers of Optoelectronics 2009年第3期2卷 293-298页

作者： Yongzhao XU Zhixin CHEN Hongtao LI Yanfen WEI Department of Electronic Engineering Dongguan University of Technology school of Information Central University of Finance and Economics tianjin Mobile Communications Corporation

We numerically studied supercontinuum generation in a tapered photonic crystal fiber with flattened dispersion properties. The fiber was weakly tapered to have normal dispersion at wavelengths around 1.55 μm after a certain distance. We pumped 4 ps pulses with low peak power and found that flatly broadened, wideband supercontinuum was generated in telecommunication ***, we also demonstrated the effects of tapered length and pulse width of the pump pulse on supercontinuum generation.

关键词： fiber optics photonic crystal fiber dispersion supercontinuum

在高应变率拉伸/压缩-扭转载荷下TC17钛合金的屈服和塑性流动行为

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 Mechanica Sinica 2024年第4期40卷 185-198页

作者：杨学赵敬凡杜冰郭亚洲李玉龙 school of Aeronautics Northwestern Polytechnical University(NPU)Xi’an710072China Yangtze River Delta Research Institute of NPU Taicang215400China Shaanxi Key Laboratory of Impact Dynamics and Engineering Application(IDEA) Northwestern Polytechnical UniversityXi’an710072China

金属材料经常暴露在高应变率和复杂的应力条件下.研究这些材料的动态力学行为对工程设计和工业应用至关重要.本文研究了TC17钛合金在压缩/拉伸-扭转作用下的动态塑性流动行为.研究了TC17钛合金在准静态和动态载荷下的初始屈服行为,并采... 详细信息

金属材料经常暴露在高应变率和复杂的应力条件下.研究这些材料的动态力学行为对工程设计和工业应用至关重要.本文研究了TC17钛合金在压缩/拉伸-扭转作用下的动态塑性流动行为.研究了TC17钛合金在准静态和动态载荷下的初始屈服行为,并采用杨、郭和李提出的动态不对称屈服准则(DAYC)来表征动态初始屈服行为.根据不同应力状态下的硬化特性,提出了一种修正的动态硬化规律(MDHL)来拟合加载面.研究了TC17钛合金在准静态和动态载荷作用下的塑性流动方向.结果表明,塑性势函数基本符合相关联流动法则.总之,本文系统性的研究了TC17钛合金的屈服性能,应变硬化规律和塑性流动规律,并利用DAYC和MDHL对其进行了表征.

关键词： TC17钛合金金属材料塑性流动高应变率扭转载荷动态力学行为应变硬化屈服准则

Nonlinear optical properties of graphene-based materials

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2012年第23期57卷 2971-2982页

作者： LIU ZhiBo ZHANG XiaoLiang YAN XiaoQing CHEN YongSheng TIAN JianGuo Key Laboratory of Weak Light Nonlinear Photonics Ministry of Education Teda Applied Physics school and school of Physics Nankai University Tianjin 300071 China College of Physics and Optoelectronics Taiyuan University of Technology Taiyuan 030024 China Key Laboratory of Functlonal Polymer Materials and Center for Nanoscale Science & technology Institute of Polymer Chemistry College of Chemistry Nankai University Tianjin 300071 China

Graphene,a two-dimensional carbon atom sheet,has attracted tremendous attention and research interest because of its exceptional physical *** has high mobility and optical transparency,in addition to flexibility,robustness and environmental *** main focus so far has been on fundamental physics and electronic ***,because the linear dispersion of the Dirac electrons enables ultrawideband tunability,we believe its true potential lies in photonics and *** this review,we introduce recent advances in the nonlinear optical properties of graphene-based *** rise of graphene in nonlinear optics is shown by several recent results,ranging from saturable absorbers and the four-wave mixing effect to giant two-photon absorption,reverse saturable absorption and optical *** relevant forms of the graphene-based materials include pure graphene,graphene oxide and graphene hybrids.

关键词： graphene nonlinear optical properties optical limiting saturable absorber graphene oxide

Electrochemical Deposition of Ni-W Gradient Deposit and Its Structural Characterization

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2003年第3期11卷 348-351页

作者：王宏智姚素薇张卫国 school of Chemical Engineering and technology Tianjin UniversityTianjin 300072China

The Ni-W gradient deposit with nano-structure was prepared by an electrochemical deposition method.X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDXA) indicate that the crystallite size of the deposit decreases from 10.3nm to 1.5nm and the crystal grating aberrance increases with the increase of W content in the growing direction of the deposit. The structure of deposit changes from crystalline to amorphous stepwise with associated increase of crystal grating aberrance, and presents gradient distribution. These show that the deposit isgradient with nano-structure.

关键词： electrochemical deposition Ni-W alloy FGM amorphous

A review of helical carbon materials structure,synthesis and applications

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2021年第1期40卷 3-19页

作者： Ding-Chuan Wang Yu Lei Wei Jiao Yi-Fan Liu Chun-Hong Mu Xian Jian school of Materials and Energy University of Electronic Science and Technology of ChinaChengdu 611731China school of Public Affairs and law Southwest Jiaotong UniversityChengdu 610031China National Engineering Research Center of Electromagnetic Radiation Control Materials State Key Laboratory of Electronic Thin Films and Integrated DevicesUniversity of Electronic Science and Technology of ChinaChengdu 610054China

The helical structures possess unique physical and chemical properties,such as superelasticity,high specific strength,chirality,and electromagnetic cross-polarization *** the development of nanoscience and nanotechnology,helical structures with various scales have been discovered or synthesized *** them,the helical carbon materials receive much attention around the ***,we present a brief review of the development of helical carbon materials in terms of structures,synthesis techniques and mechanisms,and *** controllable designing of catalysts,carbon sources and reaction parameters plays a key role to optimize the properties of the helical carbon *** the same time,the applications in microwave absorption devices,sensors,catalysts,energy conversions and storage devices,and solar cell are also *** the good chemical and physical properties,helical carbon materials have a good application prospect in many *** potential issues and future opportunities of the helical carbon materials are also proposed.

关键词： Helical carbon materials Coil Synthesis mechanisms Applications

Multi-interface collaboration of graphene cross-linked NiS-NiS_(2)-Ni_(3)S_(4) polymorph foam towards robust hydrogen evolution in alkaline electrolyte

在线全文

学校读者我要写书评

暂无评论

Nano Research 2021年第12期14卷 4857-4864页

作者： Haiqing Wang Wenjing Zhang Xiaowei Zhang Shuxian Hu Zhicheng Zhang Weijia Zhou Hong Liu Collaborative Innovation Center of technology and Equipment for Biological Diagnosis and Therapy in Universities of Shandong Institute for Advanced Interdisciplinary Research(iAIR)University of JinanJinan250022China Beijing Computational Science Research Center Beijing100193China tianjin Key Laboratory of Molecular Optoelectronic Sciences Department of ChemistrySchool of ScienceTianjin UniversityTianjin300072China State Key Laboratory of Crystal Materials Shandong UniversityJinan250100China

Electrocatalytic hydrogen production in alkaline media is extensively adopted in industry. Unfortunately, further performance improvement is severely impeded by the retarded kinetics, which requires the fine regulation of water dissociation, hydrogen recombination, and hydroxyl desorption. Herein, we develop a multi-interface engineering strategy to make an elaborate balance for the alkaline hydrogen evolution reaction (HER) kinetics. The graphene cross-linked three-phase nickel sulfide (NiS-NiS_(2)-Ni_(3)S_(4)) polymorph foam (G-NNNF) was constructed through hydrothermal sulfidation of graphene wrapped nickel foam as a three-dimensional (3D) scaffold template. The G-NNNF exhibits superior catalytic activity toward HER in alkaline electrolyte, which only requires an overpotential of 68 mV to drive 10 mA·cm^(−2) and is better than most of the recently reported metal sulfides catalysts. Density functional theory (DFT) calculations verify the interfaces between nickel sulfides (NiS/NiS_(2)-Ni_(3)S_(4)) and cross-linked graphene can endow the electrocatalyst with preferable hydrogen adsorption as well as metallic nature. In addition, the electron transfer from Ni_(3)S_(4)/NiS_(2) to NiS results in the electron accumulation on NiS and the hole accumulation on Ni_(3)S_(4)/NiS_(2), respectively. The electron accumulation on NiS favors the optimization of the H* adsorption, whereas the hole accumulation on Ni_(3)S_(4) is beneficial for the adsorption of H_(2)O. The work about multi-interface collaboration pushes forward the frontier of excellent polymorph catalysts design.

关键词： hydrogen evolution reaction nickel sulfide interface engineering polymorph heterointerface