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shift sampling theory of Fourier transform computation

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Science China(Technological Sciences) 1997年第1期40卷 21-27页

作者：柴玉璞 Bureau of Geophysical Prospecting China Oil Corporation Gucheng 072659 China

The DFT transform us extended to DFTξη transform and the relationship between FT and DFTξη is given by the Fourier transform discretization theorem. Based on the theorem, the DFTξη algorithm-error equation (DFTξη A-E equation) is established, and the minimization property of discrete effect and the oscillation property of truncation effect are demonstrated. All these construct the shift sampling theory——a new theory about Fourier transform computation.

关键词： Fourier transform shift sampling theory DFTξη A-E equation discrete effect minimization truncation effect oscillation.

Structure-activity relationship in water-gas shift reaction over gold catalysts supported on Y-doped ceria

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Journal of Rare Earths 2019年第4期37卷 383-392页

作者： Tatyana Tabakova Lyuba Ilieva Ivan Ivanov Maela Manzoli Rodolfo Zanella Petya Petrova Zbigniew Kaszkur Institute of Catalysis Bulgarian Academy of Sciences Department of Drug Science and Technology & Centre for Nanostructured Interfaces and Surfaces University of Turin Centro de Ciencias Aplicadas y Desarrollo Tecnologico Universidad Nacional Autonoma de Mexico Institute of Physical Chemistry PAS

The utilization of pure hydrogen as an energy source in fuel cells gave rise to renewed interest in developing active and stable water-gas shift catalysts. Gold catalysts have proven to be very efficient for water-gas shift reaction at low temperature. The aim of the present study was to investigate the effect of:(i) different preparation methods(impregnation and coprecipitation) to obtain a modified ceria support,and(ii) the amount of Y_2 O_3(1.0 wt%, 2.5 wt%, 5.0 wt% and 7.5 wt%) as dopant on the water-gas shift activity of Au/CeO_2 catalysts. An extended characterization by means of S_(BET), XRD, HRTEM/HAADF, FTIR,H_2-TPR and CO-TPR measurements in combination with careful evaluation of the catalyst behavior allowed to shed light on the parameters governing the water-gas shift activity. The catalysts show very high activity(>90% CO conversion) in the temperature range 180-220 ℃,with a slightly better performance of the gold catalysts on supports prepared by impregnation. The decreased activity with increasing Y_2 O_3 concentration is related to the hindering of oxygen mobility due to ordering of surface oxygen vacancies in vicinity of segregated Y^(3+). The effect of catalyst pre-treatments and the stability of the best performing samples were examined as well.

关键词： Gold catalyst Water gas shift reaction Doped ceria Yttrium Hydrogen production Rare earths

Closed-Loop Iterative Learning Control for Discrete Singular Systems with Fixed Initial shift

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Journal of Systems Science & Complexity 2019年第2期32卷 577-587页

作者： GU Panpan TIAN Senping LIU Qian School of Automation Science and Engineering South China University of Technology

This paper deals with the problem of iterative learning control for a class of discrete singular systems with fixed initial shift. According to the characteristics of the discrete singular systems, a closed-loop learning algorithm is proposed and the corresponding state limiting trajectory is *** is shown that the algorithm can guarantee that the system state converges uniformly to the state limiting trajectory on the whole time interval. Then the initial rectifying strategy is introduced to the discrete singular systems for eliminating the effect of the fixed initial shift. Under the action of the initial rectifying strategy, the system state can converge to the desired state trajectory within the pre-specified finite time interval no matter what value the fixed initial shift takes. Finally, a numerical example is given to illustrate the effectiveness of the proposed approach.

关键词： Closed-loop learning algorithm discrete singular systems, fixed initial shift iterative learning control

Evaluation of polarization field in InGaN/GaN multiple quantum well structures by using electroluminescence spectra shift

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Chinese Physics B 2020年第3期29卷 221-224页

作者： Ping Chen De-Gang Zhao De-Sheng Jiang Jing Yang Jian-Jun Zhu Zong-Shun Liu Wei Liu Feng Liang Shuang-Tao Liu Yao Xing Li-Qun Zhang State Key Laboratory of Integrated Optoelectronics Institute of SemiconductorsChinese Academy of Sciences(CAS)Beijing 100083China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China Key Laboratory of Nano-devices and Applications of CAS Suzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of SciencesSuzhou 215123China

In order to investigate the inherent polarization intensity in InGaN/GaN multiple quantum well(MQW) structures,the electroluminescence(EL) spectra of three samples with different GaN barrier thicknesses of 21.3 nm, 11.4 nm, and 6.5 nm are experimentally studied. All of the EL spectra present a similar blue-shift under the low-level current injection,and then turns to a red-shift tendency when the current increases to a specific value, which is defined as the turning *** value of this turning point differs from one another for the three InGaN/GaN MQW samples. Sample A, which has the GaN barrier thickness of 21.3 nm, shows the highest current injection level at the turning point as well as the largest value of blue-shift. It indicates that sample A has the maximum intensity of the polarization field. The red-shift of the EL spectra results from the vertical electron leakage in InGaN/GaN MQWs and the corresponding self-heating effect under the high-level current injection. As a result, it is an effective approach to evaluate the polarization field in the InGaN/GaN MQW structures by using the injection current level at the turning point and the blue-shift of the EL spectra profiles.

关键词： InGaN/GaN multiple quantum well(MQW) polarization field electroluminescence spectra shift electron leakage current

Effect of external magnetic field on the shift of resonant frequency in photoassociation of ultracold Cs atoms

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Chinese Physics B 2019年第1期28卷 367-371页

作者： Pengwei Li Yuqing Li Guosheng Feng Jizhou Wu Jie Ma Liantuan Xiao Suotang Jia State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Laser SpectroscopyCollege of Physics and Electronics Engineering Shanxi University Collaborative Innovation Center of Extreme Optics Shanxi University

We study the influence of external magnetic field on the shift of the resonant frequency in the photoassociation of ultracold Cs atoms, which are captured in a magnetically levitated optical crossed dipole trap. With the increase of the photoassociation laser intensity, the linear variation of the frequency shift is measured by recording the photoassociation spectra of the long-range 0_u^+ state of Cs molecule below the 6S_(1/2)+ 6P_(1/2) dissociation limit at different magnetic *** slope of the frequency shift to the intensity of the photoassociation laser exhibits a strong dependence on the external magnetic field. The experimental data is simulated with an analytic theory model, in which a single channel rectangular potential with the tunable well depth is introduced to acquire the influence of the magnetic field on the atomic behavior in the effective range where photoassociation occurs.

关键词： ultracold molecule photoassociation frequency shift

Relations between Mass Change and Frequency shift of a QCM Sensor in Contact with Viscoelastic Medium

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Chinese Physics Letters 2013年第5期30卷 22-24页

作者： TAN Feng HUANG Xian-He School of Automation Engineering University of Electronic Science and Technology of ChinaChengdu 611731

We investigate frequency shift of a quartz crystal microbalance(QCM)sensor introduced by mass effect,and properties of material of its coated viscoelastic film are *** validity of the Sauerbrey relation cannot be held if the viscoelastic properties of the contacting medium are *** the QCM sensor with a viscoelastic film works in the gas phase,the viscoelastic properties will introduce an extra mass *** in the liquid phase,the missing mass effect can be *** experimental results demonstrate that the QCM sensor is sensitive to the viscoelastic properties of the coating *** of the viscoelastic contacting medium should be considered.

关键词： shift QCM viscoelastic

Phase-shift Extraction and Wavefront Reconstruction in Generalized Phase-shifting Interferometry with a Standard Phase Object

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Chinese Physics Letters 2013年第9期30卷 72-75页

作者： LI Jie WANG Yu-Rong MENG Xiang-Feng YANG Xiu-Lun WANG Qing-Pu School of Information Science and Engineering and Shandong Provincial Key Laboratory of Laser Technology and Application Shandong UniversityJinan 250100

A method to extract phase shifts and reconstruct the object wave in generalized phase-shifting interferometry(GPSI)is *** phase distribution of a standard phase object and the least-square method are used to extract phase shifts over a wide range from 0 to𝜌π.Consequently,the tested object wave can be further reconstructed with the extracted phase *** is accurate and applicable for GPSI of any frame number𝑂(N𝑂≥2).Computer simulation has verified its feasibility and validity.

关键词： shift Wavefront Phase

Abnormal shift of Center Wavelength in Annealing Long-Period Gratings

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Chinese Physics Letters 2000年第1期17卷 28-30页

作者： QIN Li WEI Zhan-Xiong WANG Qing-Ya LI Hui-Ping ZHANG Yu-Shu GAO Ding-San Department of Electronics Engineering Jilin UniversityChangchun 130023

During annealing process of long-period gratings,the center wavelengths of some inodes shift to red wavelength while those of others shift to blue compared with their original written ones,and the magnitudes of the shifts are related to the decay of the grating *** red shifts of center wavelength are more evident in lower-order inodes of the *** suggest that part of the photodissociated-H2 combines continuously with Ge-defect centers within 2 h after UV-exposure,and with which the observed abnormal shifts can be explained successfully.

关键词： center shift annealing

A Special Sampling Structure with an Arbitrary Equivalent-Phase-shift for Semiconductor Lasers and Multiwavelength Laser Arrays

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Chinese Physics Letters 2011年第7期28卷 140-143页

作者： ZHOU Ya-Ting SHI Yue-Chun LI Si-Min LIU Sheng-Chun CHEN Xiang-Fei Microwave-Photonics Technology Laboratory Nanjing National Laboratory of MicrostructuresSchool of Engineering and Applied SciencesNanjing UniversityNanjing 210093 Changzhou Institute of Technology Changzhou 213002

A method used to introduce an arbitrary equivalent-phase-shift(EPS)into an asymmetric sampled Bragg grating(SBG)is *** the same structural parameters except for the sampling pattern,the asymmetric SBG offers better performance than that of a normal SBG structure for keeping single-longitudinal-mode(SLM)*** is because the proposed sampling pattern can suppress the 0th-order light resonance due to the mismatch between the two different grating sections along the whole *** method can be used to design and fabricate semiconductor lasers and multiwavelength laser arrays(MLAs)with the required EPS at high yield and low cost.

关键词： asymmetric pattern shift