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Chinese Journal of Aeronautics 2024年第8期37卷 404-420页

作者： Yuqing QIU Yan LI Jinxi LANG yuxian liu Zhong WANG School of Automation Northwestern Polytechnical UniversityXi’an 710129China

As the elevator and rudder can be used actively for control,in addition to the rotors,Coaxial High-speed Helicopters(CHHs)have the problems of control redundancy and changing control authority in the transition *** paper presents a robust-augmentation transitioning flight control design for a CHH under the adverse conditions of parametric uncertainties and external ***,based on control characteristic analysis,an Adaptive Filtered Nonlinear Dynamic Inversion(AFNDI)controller is proposed for the angular rate to handle the effect of unknown unstructured uncertainties and external *** analysis proves that the presented angular rate controller can guarantee steady-state and transient ***,the attitude angle and velocity controllers are also ***,an Incremental-based Nonlinear Prioritizing Control Allocation(INPCA)method is designed to take into account control surface transition and changing control authority,which efficiently distributes the required moments between coaxial rotors and aero-surfaces,and avoids the control reversal problem of the yaw *** the proposed control architecture,the low-pass filter is introduced to alleviate the adverse influence of time delay and measurement ***,the effectiveness of the proposed controller is demonstrated through nonlinear numerical simulations,and is compared with existing *** results show that the proposed control law can improve both capabilities of disturbance rejection and fast response,and works satisfactorily for the CHH transitioning control characteristic.

关键词： Coaxial high-speed helicopter Transition mode Attitude control Control allocation Robust adaptive control

Collection and Judgment of Electronic Data Evidence in Criminal Cases:From the Perspective of Investigation and Evidence Collection by Public Security Organs

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Journal of Forensic Science and Medicine 2019年第4期5卷 187-194页

作者： Bo Wang yuxian liu Department of Hunan Public Security The Comprehensive Case Handling CenterThe Network Technology TeamHunanChina Department of Hunan Provincial Public Security Police of The Legal CorpsHunanChina

With the continuous progress ofscience and technology,the Internet has gradually entered every field of daily *** addition to the information generated by the Internet in the form of digitization,it has become the main media for people to store *** the field of criminal offenses,the network is likely to be used to perpetrate criminal schemes,implement crimes,or help hinder investigations *** acts will leave an electronic data trail,such as WeChat information,emails,or *** a crime occurs,an evidence investigator should accurately,timely,and comprehensively obtain all electronic data related to the case by collecting,extracting,and transferring this data according to the law,and examining the authenticity,legality,and relevance of the *** a comprehensive review,the investigator should clarify the relationship between the electronic data and the facts to be proved and make full use of the obtained electronic evidence in criminal proceedings.

关键词： Authenticity collection electronic data extraction

Closed loop control design for the sense mode of micromachined vibratory gyroscopes

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Science China(Technological Sciences) 2013年第5期56卷 1112-1118页

作者： HE ChunHua ZHAO QianCheng liu yuxian YANG ZhenChuan YAN GuiZhen National Key Laboratory of Science and Technology on Micro/Nano Fabrication Institute of MicroelectronicsPeking University

This paper presents a novel design method of force rebalance control for the sense mode of micromachined vibratory *** theoretical deductions are performed to identify a precise linear model of the open loop system of the sense mode,which is crucial for the PI controller *** frequency responses obtained by experimental tests agree well with those calculated with the theoretical model,indicating the accuracy of the theoretical *** results demonstrate that the bandwidth of the closed loop is extended to 94.8 Hz from 2.3 Hz in the open loop and the quadrature signal is suppressed by about 64 dBV in the closed loop *** overshoot and stable time in the step response of the closed loop system are measured to be about 15% and 35 ms,*** mode-splitting gyroscope with the closed loop controlled sense mode achieves a scale factor of 41.0 mV/deg/s with nonlinearity of 0.09% and asymmetry of 1%,and a bias instability of 4.0 °/h with angle random walk of 0.171 deg/h1/2.

关键词： MEMS vibratory gyroscope sense mode closed loop control linear model

Can Automatic Classification Help to Increase Accuracy in Data Collection?

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Journal of Data and Information Science 2016年第3期1卷 42-58页

作者： Frederique Lang Diego Chavarro yuxian liu Science Policy Research Unit (SPRU) School of Business Management and Economics University of Sussex Tongji University Library Tongji University

Purpose： The authors aim at testing the performance of a set of machine learning algorithms that could improve the process of data cleaning when building datasets. Design/methodology/approach： The paper is centered on cleaning datasets gathered from publishers and online resources by the use of specific keywords. In this case, we analyzed data from the Web of Science. The accuracy of various forms of automatic classification was tested here in comparison with manual coding in order to determine their usefulness for data collection and cleaning. We assessed the performance of seven supervised classification algorithms （Support Vector Machine （SVM）, Scaled Linear Discriminant Analysis, Lasso and elastic-net regularized generalized linear models, Maximum Entropy, Regression Tree, Boosting, and Random Forest） and analyzed two properties： accuracy and recall. We assessed not only each algorithm individually, but also their combinations through a voting scheme. We also tested the performance of these algorithms with different sizes of training data. When assessing the performance of different combinations, we used an indicator of coverage to account for the agreement and disagreement on classification between algorithms. Findings： We found that the performance of the algorithms used vary with the size of the sample for training. However, for the classification exercise in this paper the best performing algorithms were SVM and Boosting. The combination of these two algorithms achieved a high agreement on coverage and was highly accurate. This combination performs well with a small training dataset （10%）, which may reduce the manual work needed for classification tasks. Research limitations： The dataset gathered has significantly more records related to the topic of interest compared to unrelated topics. This may affect the performance of some algorithms, especially in their identification of unrelated papers. Practical implications： Although the classification achieved by

关键词： Disambiguation Machine leaming Data cleaning Classification Accuracy Recall Coverage

Microstructures of metallic film and diamond growth from Fe-Ni-C system

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Chinese Science Bulletin 2002年第15期47卷 1258-1262页

作者： XU Bin LI Musen YIN Longwei CUI Jianjun liu yuxian GONG Jianhong College of Materials Science and Engineering Shandong UniversityJi’nan 250061China Department of Materials Science and Engineering Shandong Institute of Architecture and Engineering

The microstructures of metallic film surrounding diamond have been systemically studied using the transmission electron microscopy (TEM) and the atom force microscopy (AFM). The film can be divided into three layers (inner layer near diamond, external layer near graphite and middle layer). The graphite cannot be directly transformed into diamond in the film at HTHP: there exists a parallelrelationship between (111) of γ-(Fe,Ni) and (110) of Fe3C in the inner layer; the sawtooth-like step morphology found by AFM on the film is similar to that of corresponding diamond surface. A new model for diamond growth at HPHT is proposed from the parallel relationship and sawtooth-like step morphology. It is believed that Fe3C may be a transitional phase in the course of diamond growth, γ-(Fe,Ni) in the inner layer can absorb carbon atom groups with lamella structure from Fe3C, and then the carbon groups stack on growing diamond.

关键词： synthetic diamond high temperature and high pressure metallic film TEM AFM.

Ultrasound-Assisted Low-Density Solvent Dispersive Liquid-Liquid Extraction for the Determination of Amphetamines in Biological Samples Using Gas Chromatography-Mass Spectrometry

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Journal of Forensic Science and Medicine 2015年第2期1卷 114-118页

作者： Liang Meng Wenwen Zhang Pinjia Meng yuxian liu Department of Forensic Science Fujian Police CollegeFuzhou 350007 Traffic Management Bureau Beijing Municipal Public Security BureauBeijing 100037 College of Forensic Science People's Public Security University of ChinaBeijing 100038 Legal Affairs Section Hunan Provincial Public Security DepartmentChangsha 410001PR China

In order to control drug crime effectively,it is necessary to develop selective analytical methods suitable for unambiguous identification and determination of drugs in illicit samples and biological matrices.A novel microextraction technique based on ultrasound-assisted low-density solvent dispersive liquid-liquid microextraction,(UA-LDS-DLLME)has been applied to the determination of four amphetamines(methamphetamine,amphetamine,3,4-methylenedioxymethamphetamine,and 3,4-methylenedioxyamphetamine)in urine samples by gas chromatography-mass *** parameters affecting extraction efficiency have been investigated and ***-LDS-DLLME used ultrasound energy to assist in the emulsification process without any disperser *** the optimized conditions,linearity was observed for all analytes in the 0.15-10 p,g/mL range with correlation coefficients(R)ranging from 0.9886 to *** recoveries of75.6-91.4%with relative standard deviations of 2.5-4.0%were *** limits of detection(S/N=3)were estimated to be in the 5-10 ng/mL *** UA-LDS-DLLME technique had the advantages of shorter extraction time,suitability for simultaneous pretreatments of batches of samples,and the higher extraction *** was successfully applied to the analysis of amphetamines in real human urine samples.

关键词： Amphetamines biological samples dispersive liquid-liquid microextraction gas chromatography-mass spectrometry ultrasonication

Entrapment of Inclusions in Diamond Crystals Grown from Fe-Ni-C System

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Journal of Materials Science & Technology 2002年第2期18卷 171-172页

作者： yuxian liu, Limei XIAO and Longwei YINCollege of Materials Science and Engineering, Shandong University, Jinan 250061, China [ Manuscript received June 28, 2001, in revised form October 18, 2001] Coll. of Mat. Sci. and Eng. Shandong Univ. Jinan 250061 China

Diamond single crystals grown from Fe-Ni-C system at high temperature-high pressure (HPHT) usually contain inclusions related to the metallic catalyst. During the diamond growth, the metallic inclusions are trapped by the growth front or are formed through reaction between the contaminants trapped in the diamond. In the present paper, the metallic inclusions related to the catalyst were systematically examined by transmission electron microscopy (TEM). The chemical composition and crystal structure of the metallic inclusions were for the first time determined by selected area electron diffraction pattern (SADP) combined with energy dispersive X-ray spectrometry (EDS). It is shown that the inclusions are mainly composed of orthorhombic FeSi2, fcc (FeNi)23C6, and orthorhombic Fe3C, hexagonal Ni3C.

关键词： Synthetic diamond Fe-Ni-C system Inclusion Transmission electron microscopy

Analytic model of acoustic streaming in thermoacoustic waveguides with slowly varying cross-section

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Chinese Journal of Acoustics 2012年第4期31卷 439-454页

作者： FAN yuxian liu Ke YANG Jun Key Laboratory of Noise and Vibration Research Institute of Acoustics Chinese Academy of Sciences Beijing 100190

An analytic model of acoustic streaming generated in two-dimensional thermoa- coustic waveguides with slowly varying cross-section was developed for more general applica- tions. The analytical solutions of acoustic streaming characteristics in the closed straight tube and the annular tube are given based on the model. The solution for the closed straight tube can be applied to the case with any transverse scale. The solution for the annular tube is obtained under the assumption that the width of the varying cross-section part is much larger than the viscous and thermal penetration depths. The effects of cross-section variation, time-averaged temperature distribution and components of sound field are reflected in the analytic solutions. The magnitude and distribution of acoustic streaming velocity vary with the characteristic scale of the waveguides. The analytic model of acoustic streaming can be applied in research under thermoacoustic and other physical backgrounds.

关键词：声波导声流模型截面分析慢变穿透深度温度分布时间平均

Investigation on influencing factors of acoustic streaming in thermoacoustic waveguides with slowly varying cross-section

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Chinese Journal of Acoustics 2012年第3期31卷 295-309页

作者： FAN yuxian liu Ke YANG Jun Key Laboratory of Noise and Vibration Research Institute of Acoustics Chinese Academy of Sciences Beijing 100190

The influencing factors of acoustic streaming in thermoacoustic waveguides with slowly varying cross-section are analyzed based on theoretical analysis and numerical simulation. The distribution curves of acoustic streaming velocity in waveguides with different characteristic scales are presented in several specific cases. The results show that appropriate forms of varying cross-section can strengthen or weaken acoustic streaming for specific acoustic fields and the thermophysical parameters have no effect on this part. In addition, the influence of time-average temperature distribution on acoustic streaming is substantial in tubes with a width of the order of the thermal penetration depth. Without time-average temperature distribution, the effect of heat conduction on acoustic streaming is great in tubes whose width is an order of about 10 to 20 times the viscous penetration depth.

关键词：影响因素声波导变截面声流时间平均温度分布穿透深度热物性参数

Dynamics and interactions of blog-based science communication:A case study of blogging activities in China related to 2011 Japanese seismic and nuclear power crisis

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Chinese Journal of Library and Information Science 2013年第1期6卷 33-51页

作者： yuxian liu Li liu Ronald ROUSSEAU Yang YANG Tongji University Library Institute of Science Technology and SocietySchool of Social SciencesTsinghuaUniversity Faculty of Engineering Technology KHBO (Association KU Leuven) Information and Library Science Universiteit Antwerpen School of Economics and Management Tongji University

Purpose: This paper tries to understand the dynamics of scientific communication systems during crises by investigating as a case study the blogging activities that took place during the period of the 2011 earthquake and related events in Japan. Interactions between bloggers and registered users are studied quantitatively and qualitatively at ***, an influential science-related blogosphere in ***/methodology/approach: The editors of *** compiled a special issue of science blog articles under the title Analysis of the Japanese Earthquake. We developed a spider program and downloaded from this special issue the metadata about title, content,publishing time, total read count, reply count and recommendation count, and further collected information about bloggers and recommenders. We then sent a short message to the bloggers who wrote articles on these emergencies, asking for their educational and professional ***: We found that knowledge reflected in the blog articles is strongly related to the educational and professional background of bloggers. Knowledge diffusion is facilitated by interactions, such as recommendations, comments and answers. Interactions via comments and recommendations are of an assortative nature: A blog article is more likelyto be commented on and recommended by those bloggers who write on the same or similar topics than by those writing on a different one. Registered users tend to give comments on articles dealing with the topic that they recommend, and vice *** in the intersection of two or three topics is more intense than that within one topic. The impact of blog articles is also influenced by other factors, such as the reputation of the blogger and the type of information they *** and limitations: It is confirmed that studying blogs is a valid approach within informetric studies. Yet, we only studied one triple(earthquake, tsunami, nuclear disaster) event based on data

关键词： Chinese blogosphere Informetrics Temporal characteristics Knowledge diffusion Assortativity