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Modification of Metal Complex on the StereoselectiveHydrogenation of 2,3-Butanedione

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Chinese Chemical Letters 2001年第2期12卷 127-128页

作者： yan LI han Fan LIU PCLCC Center for Molecular ScienceInstitute of ChemistryChinese Academy of SciencesBeijing 100080

The modification of some metal complexes on Pt/Al2O3 clusters leads to remarkable increases in both the activity and the selectivity for meso-2,3-butanediol in the stereoselectivity hydrogenation of 2,3-butanedione.

关键词： stereoselective hydrogenation 2,3-butanedione metal complex platinum cluster

Historical Dataset Reconstruction and a Prediction Method of Solar 10.7cm Radio Flux

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Chinese Journal of Astronomy and Astrophysics 2008年第4期8卷 472-476页

作者： Juan Zhao yan-Ben han department of Astronomy Beijing Normal University Beijing 100875 China National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

We reconstruct the developing history of solar 10.7 cm radio flux （F10.7） since 1848, based on the yearly sunspot number and the variations. A relationship between the maximum and the linear regression slope of the first 3 years starting from minimum of the solar cycle is considered. We put forward a method of predicting the maximum of F10.7 by means of the slope-maximum relationship. Running tests for cycles 19 to 23 indicate that the method can properly predict the peak of F10.7.

关键词： Sun activity -- Sun radio radiation - Sun sunspots

Multi-blade rubbing characteristics of the shaft-disk-blade-casing system with large rotation

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Applied Mathematics and Mechanics(English Edition) 2024年第1期45卷 111-136页

作者： Zhiyuan WU Linchuan ZHAO han yan Ge yan Ao CHEN Wenming ZhanG State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong UniversityShanghai 200240China Shanghai Institute of Aerospace Systems Engineering Shanghai 201108China

Blade rubbing faults cause detrimental impact on the operation of aeroengines. Most of the existing studies on blade rubbing in the shaft-disk-blade-casing(SDBC) system have overlooked the elastic deformation of the blade, while some only consider the whirl of the rotor, neglecting its spin. To address these limitations, this paper proposes a dynamic model with large rotation for the SDBC system. The model incorporates the spin and whirl of the rotor, enabling the realistic reproduction of multiblade rubbing faults. To verify the accuracy of the SDBC model with large rotation and demonstrate its capability to effectively consider the rotational effects such as the centrifugal stiffening and gyroscopic effects, the natural characteristics and dynamic responses of the proposed model are compared with those obtained from reported research and experimental results. Furthermore, the effects of the rotating speed, contact stiffness,and blade number on the dynamic characteristics of the SDBC system with multi-blade rubbing are investigated. The results indicate that the phase angle between the rotor deflection and the unbalance excitation force increases with the increasing rotating speed,which significantly influences the rubbing penetration of each blade. The natural frequency of the SDBC system with rubbing constrain can be observed in the acceleration response of the casing and the torsional response of the shaft, and the frequency is related to the contact stiffness. Moreover, the vibration amplitude increases significantly with the product of the blade number under rubbing, and the rotating frequency approaches the natural frequency of the SDBC system. The proposed model can provide valuable insight for the fault diagnosis of rubbing in bladed rotating machinery.

关键词： shaft-disk-blade-casing(SDBC) large rotation spin and whirl multi-blade rubbing rotational effect

Comparison of Two MicroRNA Quantification Methods for Assaying MicroRNA Expression Profiles in Wheat(Triticum aestivum L.)

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Journal of Integrative Agriculture 2014年第4期13卷 733-740页

作者： han Ran yan yan ZHOU Peng ZHAO Hui-xian State Key Laboratory of Crop Stress Biology for Arid Areas/College of Life Sciences Northwest A&F University

Two microRNA （miRNA） quantification methods, namely, poly（A） reverse transcription （RT）-quantitative real-time polymerase chain reaction （qPCR） and stem-loop RT-qPCR, have been developed for quantifying miRNA expression. In the present study, five miRNAs, including miR166, miR167, miR168, miR159, and miR396, with different sequence frequencies, were selected as targets to compare their expression profiles in five wheat tissues by applying the two methods and deep sequencing. The study aimed to determine a simple, reliable and high-throughput method for detecting miRNA expressions in wheat tissues. Results showed that the miRNA expression profiles determined by poly（A） RT-qPCR were more consistent with those obtained by deep sequencing. Further analysis indicated that the correlation coefficients of the data obtained by poly（A） RT-qPCR and deep sequencing （0.739, P≤0.01） were higher than those obtained by stem-loop RT-qPCR and deep sequencing （0.535, P≤0.01）. The protocol used for poly（A） RT-qPCR is simpler than that for stem-loop RT-qPCR. Thus, poly（A） RT-qPCR was a more suitable high-throughput assay for detecting miRNA expression profiles. To the best of our knowledge, this study was the first to compare these two miRNA quantification methods. We also provided useful information for quantifying miRNA in wheat or other plant species.

关键词： Triticum aestivum L. microRNA deep sequencing poly(A) RT-qPCR stem-loop RT-qPCR

Investigation of three different cooling treatments on dynamic mechanical properties and fragmentation characteristics of granite subjected to thermal cycling

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Underground Space 2022年第5期7卷 847-861页

作者： Lifeng Fan han Li yan Xi Beijing University of Technology Beijing 100124China

Underground thermal engineering such as geothermal exploitation usually involves the response of impact loads due to the drilling operation and blasting *** study investigated the dynamic mechanical properties and fragmentation characteristics of granite subjected to thermal cycling under natural cooling,water cooling,and liquid nitrogen ***,split Hopkinson pressure bar tests were performed on granite under three different cooling methods to study the dynamic mechanical parameters with thermal ***,the damage factors were calculated to evaluate the damage on granite and the relationship between damage and ***,the granite fragments after impact were sieved,and the fractal dimension and average fragment size were introduced to analyze the fragmentation *** results demonstrate that the degradation of dynamic mechanical properties mainly occurs in the first four thermal cycles;with the increase of damage factor,the stress decreases linearly under the three cooling methods,and the damage caused by liquid nitrogen cooling to granite is the most significant,followed by water *** of granite change from axial splitting failure to a more complex composite failure *** addition,with the decrease of the average fragment size,the fractal dimension of the granite gradually increases,resulting in the higher fragmentation degree and the better uniformity of fragmentation.

关键词： Split Hopkinson pressure bar Dynamic mechanical properties Fragmentation characteristics Cooling treatment

Long-term system load forecasting based on data-driven linear clustering method

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Journal of Modern Power Systems and Clean Energy 2018年第2期6卷 306-316页

作者： Yiyan LI Dong han Zheng yan Key Laboratory of Control of Power Transmission andConversion Ministry of Education Department of Electrical Engineering Shanghai Jiao Tong University

In this paper, a data-driven linear clustering(DLC) method is proposed to solve the long-term system load forecasting problem caused by load fluctuation in some developed cities. A large substation load dataset with annual interval is utilized and firstly preprocessed by the proposed linear clustering method to prepare for *** optimal autoregressive integrated moving average(ARIMA) models are constructed for the sum series of each obtained cluster to forecast their respective future load. Finally, the system load forecasting result is obtained by summing up all the ARIMA forecasts. From error analysis and application results, it is both theoretically and practically proved that the proposed DLC method can reduce random forecasting errors while guaranteeing modelling accuracy, so that a more stable and precise system load forecasting result can be obtained.

关键词： Long-term system load forecasting Datadriven Linear clustering Autoregressive integrated moving average(ARIMA) Error analysis

Driving as well as on a Sunny Day? Predicting Driver’s Fixation in Rainy Weather Conditions via a Dual-Branch Visual Model

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IEEE/CAA Journal of Automatica Sinica 2022年第7期9卷 1335-1338页

作者： han Tian Tao deng Hongmei yan MOE Key Laboratory for Neuroinformation the School of Life Science and TechnologyUniversity of Electronic Science and Technology of ChinaChengdu 610054China School of Information Science and Technology Southwest Jiaotong UniversityChengdu 611756China IEEE

dear Editor,Traffic driving is a dynamic and complicated task in which drivers are required to pay close attention to the important targets or regions to maintain safe *** weather conditions make it more challenging with factors such as low visibility,raindrops,pedestrian with umbrellas,wipers,*** showed that rainy condition affects driving safety significantly[1],[2].It is reported that,in raining weather condition,the odds for a fatal accident are 3.340 times higher on highways than on streets[3].An investigation of the relationship between rainfall and fatal crashes in Texas from 1994 to 2018 on fatality analysis reporting system(FARS)database illustrated that rain-related fatal crashes represented about 6.8%of the total fatal crashes on average,moreover,the proportion showed high variability at the annual,monthly,and hourly time scales[4].Therefore,raining is a complex and critical factor for road safety planning and *** fact,the traffic environment is a dynamic scene with multiple sources of information,including important targets that are highly relevant to the current driving task as well as irrelevant targets that may distract the driving task[5].

关键词： driving Driver visibility

Inter-harmonics in multi-terminal VSC-based HVDC systems

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Journal of Modern Power Systems and Clean Energy 2016年第2期4卷 282-291页

作者： Minxiao han Phuchuy NGUYEN Wenli yan School of Electrical Engineering North China Electric Power UniversityBeijing 102206China School of Mathematical&Physical Science School North China Electric Power UniversityBeijing 102206China

Multi-terminal voltage sourced converter(VSC)-based high voltage direct current (HVDC) system composes of a number of VSCs connected to an HVDC grid (or dc grid).The dc grid is often configured by cable interconnections between converter stations,thus imposing resonance issues affecting harmonic interaction in the *** on the harmonic transfer characteristics of VSC and HVDC systems,the appearance and the interaction of inter-harmonics in the multi-terminal VSC-based HVDC system are *** models are built and implemented using SimPowerSystems in *** simulation results show that,a series of inter-harmonics are produced and tend to be dominant in low-frequency *** in the dc grid,the inter-harmonic transfer can be magnified due to inter-harmonic *** complex resonance issues in the dc grid are investigated in combination with interaction through the VSC,it is beneficial to harmonic filter designs as well as other harmonic mitigation methods.

关键词： Voltage sourced converter Inter-harmonic VSC-based HVDC Multi-terminal VSC-based HVDC DC-resonance

Strong Approximation of Locally Square-Integrable Martingales

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Acta Mathematica Sinica,English Series 2012年第6期28卷 1221-1232页

作者： Zheng yan LIN han Chao WANG department of Mathematics Zhejiang University

In this paper, we consider the strong approximation for locally square-integrable martingales. In our results, the limit process may be a process with jumps. This is an extension of the former results.

关键词： Locally square-integrable martingales strong approximation jumps