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Constrained minimum power combination for broadband beamformer design in the STFT domain

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Frontiers of Computer Science 2017年第3期11卷 408-418页

作者： Zhong-hua fu School of Computer Science Northwestern Polytechnical University Xi'an 710072 China

Beamforming using sensor array is widely used in spatial signal processing since it offers better spatial focusing capability than single sensor. However, in practical appli- cations for broadband signal, there always exists a trade-off issue between the directivity capability of an array and its robustness on system errors. In this paper, in order to combine merits of different beamformers instead of trade-off their per- formances, we propose a constrained minimum-power com- bination method. We firstly analyze two optimal beamform- ers that maximize Directivity Factor （DF） and White Noise Gain （WNG） respectively. Then we propose a non-linear combination method, which automatically selects the best beamformer that has the minimum output power, so as to control the unwanted white noise amplification and keep the maximum DF if possible. Two solutions to the proposed com- bination strategy are given. They do not need to determine the correct trade-off factor used in linear combination method, and avoid challenge ~stimations on noise and target statistics required in adaptive beamforming. The performance of the proposed beamformer is evaluated in ideal noise fields and complicated noise fields respectively. It is shown that the proposed beamformer integrates merits of different beamform- ers. It always achieves the best speech quality and biggest noise reduction compared to other popular beamformers.

关键词： robust beamforming directivity index white noise gain broadband STFT domain speech enhancement

Summed volume region selection based three-dimensional automatic target recognition for airborne LIDAR

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Defence Technology（防务技术） 2020年第3期16卷 535-542页

作者： qi-shu qian Yi-hua Hu Nan-xiang Zhao Min-le Li fu-cai Shao State Key Laboratory of Pulsed Power Laser Technology National University of Defense TechnologyHefei230037China Anhui Province Key Laboratory of Electronic Restriction National University of Defense TechnologyHefei230037China The Military Representative Bureau of the Ministry of Equipment Development of the Central Military Commission in Beijing Beijing100191China

Airborne LIDAR can flexibly obtain point cloud data with three-dimensional structural information,which can improve its effectiveness of automatic target recognition in the complex *** with 2D information,3D information performs better in separating objects and ***,an aircraft platform can have a negative influence on LIDAR obtained data because of various flight attitudes,flight heights and atmospheric disturbances.A structure of global feature based 3D automatic target recognition method for airborne LIDAR is proposed,which is composed of offline phase and online *** performance of four global feature descriptors is *** the summed volume region(SVR) discrepancy in real objects,SVR selection is added into the pre-processing operations to eliminate mismatching clusters compared with the interested *** reliable simulated data are obtained under various sensor’s altitudes,detection distances and atmospheric *** final experiments results show that the added step increases the recognition rate by above 2.4% and decreases the execution time by about 33%.

关键词： 3D automatic target recognition Point cloud LIDAR Airborne Global feature descriptor

Structures and Properties of Polyimide with Different Pre-imidization Degrees

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Chinese Journal of Polymer Science 2020年第8期38卷 840-846,I0006页

作者： fu-Yao Hao Jian-hua Wang Sheng-Li qi Guo-Feng Tian De-Zhen Wu State Key Laboratory of Chemical Resource Engineering Beijing University of Chemical TechnologyBeijing 100029China

A series of polyimide(PI)films derived from pyromellitic dianhydride(PMDA)and 4,4'-oxydianiline(ODA)were prepared with the employment of chemical pre-imidization,and the pre-imidization degree(pre-ID)was found influential on structures and properties of the films ***,a certain degree of chemical imidization could promote the in-plane orientation of molecular chains inside the film,which then enhanced the mechanical strength and reduced the coefficient of thermal expansion(CTE)of the ***,such pre-imidization process could expand the internal space gap inside the films,thereby lowering their dielectric constant and glass transition *** study provides a new approach for preparing high-performance PI films through chemical imidization.

关键词： Polyimide Pre-imidization Stacking model In-plane orientation

CATALYTIC ACTIVITY OF TRANSITION METAL SUBSTITUTED POLYOXOMETALATES FOR ALKENE EPOXIDATION

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Chinese Chemical Letters 1995年第2期6卷 155-158页

作者： Jing fu LIU qi hua YANG Ming Xiu LI Dgpartment of Chemistry Northeast Normal UniversityChangchun130024

The alkene cpoxidation by iodosylbenzene can be catalyzed by transition metal substituted polyoxometalates. Among the polyoxomctalates examined β-SiW9M3 and ZnW11Ti was found to be the most cfficient catalyst. The ox... 详细信息

关键词： ?

Contact Model of Revolute Joint with Clearance Based on Fractal Theory

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Chinese Journal of Mechanical Engineering 2018年第6期31卷 34-44页

作者： Shi-hua Li Xue-Yan Han Jun-qi Wang Jing Sun fu-Juan Li Parallel Robot and Mechatronic System Laboratory of Hebei Province Yanshan University

The contact sti ness of a mechanical bonding surface is an important parameter in determining the normal and radial contact force. To improve the calculation accuracy of the contact force model, the surface roughness of the bonding surface and the energy loss that necessarily occurs during the impact process should be considered com?prehensively. To study the normal contact force of a revolute joint with clearance more accurately in the case of dry friction, a nonlinear sti ness coe cient model considering the surface roughness was established based on fractal theory, which considers the elastic, elastic?plastic, and plastic deformations of the asperities of the contact surface during the contact process. On this basis, a modified nonlinear spring damping model was established based on the Lankarani–Nikravesh contact force model. The laws influencing the surface roughness, recovery coe cient, initial velocity, and clearance size on the impact force were revealed, and were compared with the Lankarani–Nikravesh model and a hybrid model using MATLAB. The maximum impact force was obtained using a modified contact force model under di erent initial velocities, di erent clearances, and di erent degrees of surface roughness, and the calculated results were then compared with the experiment results. This study indicates that the modified model can be used more widely than other models, and is suitable for both large and small clearances. In particular, the modified model is more accurate when calculating the contact force of a revolute joint with a small clearance.

关键词： Fractal theory Modified contact model Surface roughness Lankarani–Nikravesh model

Estimating the largest Lyapunov exponent in a multibody system with dry friction by using chaos synchronization

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Acta Mechanica Sinica 2006年第3期22卷 277-283页

作者： Shihui fu qi Wang School of Science Beijing University of Aeronautics and Astronautics Beijing 100083 China

Using the properties of chaos synchronization, the method for estimating the largest Lyapunov exponent in a multibody system with dry friction is presented in this paper. The Lagrange equations with multipliers of the systems are given in matrix form, which is adequate for numerical calculation. The approach for calculating the generalized velocity and acceleration of the slider is given to determine slipping or sticking of the slider in the systems. For slip-slip and stick-slip multibody systems, their largest Lyapunov exponents are calculated to characterize their dynamics.

关键词： Multibody system Dry friction Lyapunov exponent Chaos synchronization

Research on Water-Exit and Take-off Process for Morphing Unmanned Submersible Aerial Vehicle

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China Ocean Engineering 2017年第2期31卷 202-209页

作者： HU Jun-hua XU Bao-wei FENG Jin-fu qi Duo YANG Jian WANG Cong Engineering College of Aeronautics and Astronautics Air Force Engineering University Flying Instructor Training Base Air Force Aviation University

This paper presents a theoretic implementation method of Morphing Unmanned Submersible Aerial Vehicle （MUSAV）, which can both submerge in the water and fly in the air. Two different shapes are put forward so that the vehicle can suit both submergence and flight, considering the tremendous differences between hydrodynamic configuration and aerodynamic configuration of a vehicle. The transition of the two shapes can be achieved by using morphing technology. The water-to-air process, including water-exit, morphing, take-off and steady flight, is analyzed. The hydrodynamic and aerodynamic model of the vehicle exiting the water surface obliquely and then taking off into the air has been founded. The control strategy after morphing is analyzed and the control method is given. Numerical method is used to validate the motion model of the water-exit process. Results of simulations show the validity of the proposed model and the feasibility of MUSAV in theory.

关键词： Morphing Unmanned Submersible Aerial Vehicle (MUSAV) water-to-air process dynamic model flight control

Study on the Evolution of a Northeast China Cold Vortex during the Spring of 2010

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Atmospheric and Oceanic Science Letters 2014年第2期7卷 149-156页

作者： fu Shen-Ming SUN Jian-hua qi Lin-Lin International Center for Climate and Environment Sciences (ICCES) Institute of Atmospheric Physics Chinese Academy of Sciences Laboratory of Cloud-Precipitation Physics and Severe Storms (LACS) Institute of Atmospheric Physics Chinese Academy of Sciences Institute of Aeronautical Meteorology and Chemical Defense Equipment Academy of Air Force

Based on the final analysis data with horizontal resolution of 1°× 1°(four times a day) from the National Centers for Environmental Prediction(NCEP), a typical Northeast China cold vortex(NCCV) during the spring of 2010 was examined with the quasi-Lagrange- form eddy flux circulation(EFC) budget equation. Results indicated that the mechanisms that account for the development, maintenance, and attenuation of the cyclone varied with levels and stages. Displacement of the cyclone and transports by background environmental circulations dominated the variation of the cyclone in the middle and upper levels, whereas displacement and divergence associated with the cyclone dominated the evolution of the NCCV in the middle and lower levels. Moreover, interactions between the NCCV and other subsynoptic weather systems were important for the development of the cyclone, and the pattern of background environmental circulations was also important for the evolution of the NCCV, since the cyclone enhanced(weakened) as it moved from areas of low(high) vorticity to high(low) ones.

关键词： Northeast China cold vortex quasi-Lagrange-form eddy flux circulation budget

Metal peroxides for cancer treatment

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Bioactive Materials 2021年第9期6卷 2698-2710页

作者： Jin He Lian-hua fu Chao qi Jing Lin Peng huang Marshall Laboratory of Biomedical Engineering International Cancer CenterLaboratory of Evolutionary Theranostics(LET)School of Biomedical EngineeringHealth Science CenterShenzhen UniversityShenzhen518060China Key Laboratory of Biorheological Science and Technology Ministry of EducationCollege of BioengineeringChongqing UniversityChongqing400044China

In recent years,metal peroxide(MO_(2))such as CaO_(2) has received more and more attention in cancer ***_(2) is readily decompose to release metal ions and hydrogen peroxide in the acidic tumor microenvironment(TME),resulting metal ions overloading,decreased acidity and elevated oxidative stress in *** of these changes making MO_(2) an excellent tumor therapeutic ***,by combining MO_(2) with photosensitizers,enzymes or Fenton reagents,MO_(2) can assist and promote various tumor therapies such as photodynamic therapy and chemodynamic *** this review,the synthesis and modification methods of MO_(2) are introduced,and the representative studies of MO_(2)-based tumor monotherapy and combination therapy are discussed in ***,the current challenges and prospects of MO_(2) in the field of tumor therapy are emphasized to promote the development of MO_(2)-based cancer treatment.

关键词： Metal peroxide Metal ions overloading Oxidative stress Combination therapy Cancer treatment