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Low-cost and fluoride-free synthesis of MFI zeolite nanosheets with enhanced stability for benzene alkylation with ethanol

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Journal of Energy Chemistry 2025年第1期100卷 458-468页

作者： Peng Zhu Cun Liu Yiren Yu Guoshu Gao Yumeng Zhao Xiongfu Zhang Guodong Liu Guohui Yang State key laboratory of Fine Chemicals School of Chemical Engineering Dalian University of Technology State key laboratory of Catalysis Dalian Institute of Chemical Physics Chinese Academy of Sciences

Zeolite nanosheets with a short b-axis thickness are highly desirable in lots of catalytic reactions due to their reduced diffusion resistance. Nevertheless, conventional synthesis methods usually require expensive structure-directing agents(SDAs), pricey raw materials, and eco-unfriendly fluorine-containing additives. Here, we contributed a cost-effective and fluoride-free synthesis method for synthesizing high-quality MFI zeolite nanosheets through a Silicalite-1(Sil-1) seed suspension and urea cooperative strategy, only with inexpensive colloidal silica as the Si source. Our approach was effective for synthesizing both Sil-1 and aluminum-containing ZSM-5 nanosheets. By optimizing key synthesis parameters,including seed aging time, seed quantity, and urea concentration, we achieved precise control over the crystal face aspect ratio and b-axis thickness. We also revealed a non-classical oriented nanosheet growth mechanism, where Sil-1 seeds induced the formation of quasi-ordered precursor particles, and the(010)crystal planes of these particles facilitated urea adsorption, thereby promoting c-axis-oriented *** obtained ZSM-5 nanosheets exhibited exceptional catalytic performance in the benzene alkylation with ethanol, maintaining stability for over 500 h, which is 5 times longer than traditional ZSM-5 catalysts. Furthermore, large-scale production of ZSM-5 nanosheets was successfully carried out in a 3 L highpressure autoclave, yielding samples consistent with those from laboratory-scale synthesis. This work marks a significant step forward in the sustainable and efficient production of MFI nanosheets using inexpensive and environmentally friendly raw materials, offering the broad applicability in catalysis.

关键词： MFI zeolite ZSM-5 Nanosheets Scale-up synthesis Aromatic alkylation

Residual Phase Noise and time Jitters of Single-Chip Digital frequency Dividers

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Journal of Electronic Science and Technology 2015年第3期13卷 264-268页

作者： Lu-Lu Yan Sen Meng Wen-Yu Zhao Wen-Ge Guo Hai-Feng Jiang Shou-Gang Zhang the key laboratory of time and frequency standards National Time Service Center (NTSC) Chinese Academy of Sciences the School of Science Xi’an Shiyou University the key laboratory of time and frequency standards National Time Service Center Chinese Academy of Sciences

In this paper, we demonstrate the residual phase noise of a few microwave frequency dividers which usually limit the performance of frequency synthesizers. In order to compare these dividers under different operation frequencies, we calculate additional time jitters of these dividers by using the measured phase noise. The time jitters are various from -0.1 fs to 43 fs in a bandwidth from 1 Hz to 100 Hz in dependent of models and operation frequencies. The HMC series frequency dividers exhibit outstanding performance for high operation frequencies, and the time jitters can be sub-fs. The time jitters of SP8401, MC10EP139, and MC100LVEL34 are comparable or even below that of HMC series for low operation frequencies.

关键词： frequency divider phase noise spectra analysis time jitter

Momentum-space crystal in narrow-line cooling of ^(87)Sr

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Chinese Physics B 2019年第1期28卷 360-366页

作者： Jian-Xin Han Ben-Quan Lu Mo-Juan Yin Ye-Bing Wang Qin-Fang Xu Xiao-Tong Lu Hong Chang key laboratory of time and frequency Primary standards National time Service Center Chinese Academy of Sciences University of Chinese Academy of Sciences

The discovery of the momentum space crystal based on the alkaline-earth atom ^(88)Sr in narrow-line cooling has paved the way to explore this novel physical phenomenon in other cold atom systems. In this paper, a momentum space crystal based on the fermions ^(87)Sr in narrow-line cooling of transition^1S_0–~3P_1 is demonstrated. We theoretically analyze and compare the formation principle of the narrow-line with that of broad-line cooling, and achieve the momentum space crystal in experiment. Beyond that we present a series of numerical calculations of those important parameters which influence the distribution and size of the momentum space crystal. Correspondingly, we vary the values of these parameters in experiment to observe the momentum space crystal evolution and distribution. The experimental results are in conformity with the results of the theoretically numerical calculations. These results and analyses provide a detailed supplementary study on the formation and evolution of momentum space crystal. In addition, this work could also give a guideline on atomic manipulation by narrow-line cooling.

关键词： momentum space crystal narrow-line cooling strontium

A long-term frequency-stabilized erbium-fiber-laser-based optical frequency comb with an intra-cavity electro-optic modulator

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Chinese Physics B 2015年第6期24卷 366-370页

作者：张颜艳闫露露赵文宇孟森樊松涛张龙郭文阁张首刚姜海峰 key laboratory of time and frequency standards National Time Service Center University of the Chinese Academy of Sciences School of Science Xi'an Shiyou University

We demonstrate an optical frequency comb based on an erbium-doped-fiber femtosecond laser with the nonlinear polarization evolution scheme. The repetition rate of the laser is about 209 MHz. By controlling an intra-cavity electro- optic modulator and a piezo-transducer, the repetition rate can be stabilized with a high-bandwidth servo in a frequency range of 3 kHz, enabling long-term repetition rate phase-locking. The in-loop frequency stability of repetition rate is about 1.6× 10-13 in an integration time of 1 s, limited by the measurement system; and it is inversely proportional to integration time in the short term. Furthermore, using a common path f-2f interferometer, the carrier envelope offset frequency of the comb is obtained with a signal-to-noise ratio of 40 dB in a 3-MHz resolution bandwidth. Stabilized cartier envelope offset frequency exhibits a deviation of 0.6 mHz in an integration time of 1 s.

关键词： optical frequency comb fiber laser frequency stabilization frequency instability

Coherent Transfer of Optical frequency over 112 km with Instability at the 10^(-20) Level

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Chinese Physics Letters 2016年第11期33卷 47-49页

作者：邓雪刘杰焦东东高静臧琦许冠军董瑞芳刘涛张首刚 National time Service Centre Chinese Academy of Sciences key laboratory of time and frequency standards Chinese Academy of Sciences University of Chinese Academy of Sciences

We demonstrate optical-carrier transfer over a 112-km single-span urban fiber link, By actively compensating the phase noise induced along the fiber link, a noise suppression of 55 dB at 1 Hz is obtained. A fractional frequency instability of 2.5× 10^-16 at i s is achieved, and reaching 7.5× 10^-20 at 10000 s. The system is stable and able to run for a long time. This work will contribute to optical frequency distribution and remote comparison among atomic clocks.

关键词： of is as link Coherent Transfer of Optical frequency over 112 km with Instability at the 10 Level with over

Simulation and Design of Fluorescence Collector

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Chinese Physics Letters 2016年第9期33卷 56-59页

作者：石浩马杰李孝峰刘杰张首刚 National time Server Center Chinese Academy of Sciences University of Chinese Academy of Science key laboratory of time and frequency standards Chinese Academy of Sciences

Fluorescence collector is a critical component in optically pumped Cs beam frequency standards. We design a new fluorescence collector by means of a new method. By means of two simulation methods, a smaller fluorescence collector with the same collection efficiency is achieved. It can be applied to almost all fluorescence detection systems in atom-light interaction experiments. We select the practical fluorescence collector studied by comparing three designing schemes. Its structure is very plain. Moreover, its fluorescence collection efficiency is very high. The collection efficiency of the practical fluorescence collector we designed is over 33% by means of two different ways.

关键词： of be as by Simulation and Design of Fluorescence Collector in is

Strontium optical lattice clock at the National time Service Center

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Chinese Physics B 2018年第2期27卷 204-209页

作者：王叶兵尹默娟任洁徐琴芳卢本全韩建新郭阳常宏 CAS key laboratory of time and frequency Primary standards National Time Service Center Xi' an 710600 China University of Chinese Academy of Sciences (CAS) Beijing 100049 China

We report the 87Sr optical lattice clock developed at the National time Service Center. We achieved a closed-loop operation of the optical lattice clock based on 87Sr atoms. The linewidth of the spin-polarized clock peak is 3.9 Hz with a clock laser pulse length of 300 ms, which corresponds to a Fourier-limited linewidth of 3 Hz. The fitting of the in-loop error signal data shows that the instability is approximately 5 × 10 15τ-1/2, affected primarily by the white noise. The fractional frequency difference averages down to 5.7 × 10 ^-17 for an averaging time of 3000 s.

关键词： optical clock optical lattice strontium atoms stability

Pulsar timing residuals due to individual non-evolving gravitational wave sources

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Research in Astronomy and Astrophysics 2014年第4期14卷 390-400页

作者： Ming-Lei Tong Cheng-Shi Zhao Bao-Rong Yan Ting-Gao Yang Yu-Ping Gao National time Service Center Chinese Academy of Sciences key laboratory of time and frequency Primary standards Chinese Academy of Sciences key laboratory of Precision Navigation and Timing Technology Chinese Academy of Sciences

The pulsar timing residuals induced by gravitational waves from non- evolving single binary sources are affected by many parameters related to the relative positions of the pulsar and the gravitational wave sources. We will analyze the various effects due to different parameters. The standard deviations of the timing residuals will be calculated with a variable parameter fixing a set of other parameters. The or- bits of the binary sources will be generally assumed to be elliptical. The influences of different eccentricities on the pulsar timing residuals will also be studied in detail. We find that the effects of the related parameters are quite different, and some of them display certain regularities.

关键词： gravitational waves: general -- pulsars: general -- binaries: general

Interrogation of optical Ramsey spectrum and stability study of an ^(87)Sr optical lattice clock

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Chinese Physics B 2022年第3期31卷 306-310页

作者： Jing-Jing Xia Xiao-Tong Lu Hong Chang CAS key laboratory of time and frequency Primary standards National Time Service CenterXi'an 710600China University of Chinese Academy of Sciences(CAS) Beijing 100049China

The optical Ramsey spectrum is experimentally realized in an ^(87)Sr optical lattice clock, and the measured linewidth agrees well with theoretical expectation. The coherence time between the clock laser and the atoms, which indicates the maximum free evolution period of using Ramsey detection to measure the atom-laser phase information, is determined as 340(23) ms by measuring the fringe contrasts of the Ramsey spectrum as a function of the free evolution period. Furthermore, with the same clock duty cycle of about 0.1, the clock stability is measured by using the Ramsey and Rabi spectra,respectively. The experimental and theoretical results show approximately the same stability as the two detection methods, which indicates that Ramsey detection cannot obviously improve the clock stability until the clock duty cycle is large enough. Thus, it is of great significance to choose the detection method of a specific clock.

关键词： optical Ramsey spectrum optical lattice clock stability coherence time