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On Mean Values of Character Sums

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Acta Mathematica Sinica,English Series 2006年第2期22卷 561-570页

作者： Zai zhao meng School of Mathematical Sciences Peking University

We use the resultant of two polynomials to discuss the roots of congruences, and then we improve the result of Burgess on the mean values of character sums in the case r = 3. Finally, we give a new estimate for the me... 详细信息

关键词： Resultant Polynomials Character

An Angle Structure Descriptor for Image Retrieval

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China Communications 2016年第8期13卷 222-230页

作者： meng zhao Huaxiang Zhang Lili meng School of Information Science and Engineering Shandong Normal University Institute of Data Science and Technology Shandong Normal University

This paper presents an efficient image feature representation method, namely angle structure descriptor(ASD), which is built based on the angle structures of images. According to the diversity in directions, angle structures are defined in local blocks. Combining color information in HSV color space, we use angle structures to detect images. The internal correlations between neighboring pixels in angle structures are explored to form a feature vector. With angle structures as bridges, ASD extracts image features by integrating multiple information as a whole, such as color, texture, shape and spatial layout information. In addition, the proposed algorithm is efficient for image retrieval without any clustering implementation or model training. Experimental results demonstrate that ASD outperforms the other related algorithms.

关键词： image retrieval angle structure descriptor HSV color space local descriptor

A COMBINED DATA PROCESSING METHOD ON WATER IMPACT FORCE MEASUREMENT

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Journal of Hydrodynamics 2012年第5期24卷 692-701页

作者： zhao meng-hua CHEN Xiao-peng School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi'an 710072China

A combined method is proposed to determine the water entry acceleration at a low impact velocity through image processing. The procedure includes：（1） a sequence of images for water impact are recorded by a high speed camera, （2） the sub-pixel image processing method is employed to calculate the displacement with an accuracy on the ＂sub-pixel＂ level, （3） the acceleration of the object is acquired by differentiating the displacement twice and with results being further filtered by a carefully designed low-pass Butterworth filter. A theoretically based analysis is conducted for designing the parameters of the low-pass filters. It is shown that the water entry can be regarded as a procedure with a slowly changing velocity. The method is validated with the standard sinusoidal motion and the water entry of a sphere. This approach could be considered as an auxiliary method during the early-stage study of the water entry, and it could be further applied to some complicated circumstances, like the water entry of spinning spheres.

关键词： water impact force measurement image processing low-pass filter sub-pixel edge detection

Metal-organic framework-based CO2 capture: from precise material design to high-efficiency membranes

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Frontiers of Chemical Science and Engineering 2020年第2期14卷 188-215,F0004页

作者： Yujie Ban meng zhao Weishen Yang State Key Laboratory of Catalysis Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023China University of Chinese Academy of Sciences Beijing 100049China

A low-carbon economy calls for CO capture *** separations represent an energy-efficient and environment-friendly process compared with distillations and solvent ***-organic frameworks(MOFs),as a novel type of porous materials,are being generated at a rapid and growing pace,which provide more opportunities for high-efficiency CO *** this review,we illustrate a conceptional framework from material design and membrane separation application for CO capture,and emphasize two importance themes,namely(i)design and modification of CO-philic MOF materials that targets secondary building units,pore structure,topology and hybridization and(ii)construction of crack-free membranes through chemical epitaxy growth of active building blocks,interfacial assembly,ultrathin two-dimensional nanosheet assembly and mixed-matrix integration strategies,which would give rise to the most promising membrane performances for CO capture,and be expected to overcome the bottleneck of permeability-selectivity limitations.

关键词： CO2 capture CO2-philic MOFs crack-free membranes

Regulation of hematopoietic stem cells in the niche

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Science China(Life Sciences) 2015年第12期58卷 1209-1215页

作者： zhao meng LI LinHeng Stowers Institute for Medical Research Department of Pathology & Laboratory Medicine University of Kansas Medical Center

Hematopoiesis provides a suitable model for understanding adult stem cells and their niche. Hematopoietic stem cells(HSCs) continuously produce blood cells through orchestrated proliferation, self-renewal, and differentiation in the bone marrow(BM). Within the BM exists a highly organized microenvironment termed "niche" where stem cells reside and are maintained. HSC niche is the first evidence that a microenvironment contributes to protecting stem cell integrity and functionality in mammals. Although multiple models exist, recent progress has principally elucidated the cellular complexity of the HSC niche that maintains and regulates HSCs in BM. Here we introduce the development and summarize the achievements of HSC niche studies.

关键词： hematopoietic stem cells niche regeneration

CO_(2)geological sequestration potential of the low-rank coals in the southern margin of the Junggar Basin

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Frontiers of Earth Science 2023年第3期17卷 727-738页

作者： Qun zhao Ze DENG meng zhao Dexun LIU Research Institute of Petroleum Exploration&Development PetroChinaBeijing 100083China PetroChina Southwest Oil&Gasfield Company Chengdu 610051China

Carbon capture,utilization,and storage(CCUS)is considered one of the most effective measures to achieve net-zero carbon emissions by 2050,and low-rank coal reservoirs are commonly recognized as potential CO_(2)storage sites for carbon *** evaluate the geological CO_(2)sequestration potential of the low-rank coal reservoirs in the southern margin of the Junggar Basin,multiple experiments were performed on coal samples from that area,including high-pressure mercury porosimetry,low-temperature N2 adsorption,overburden porosity and permeability measurements,and high-pressure CH4 and CO_(2)isothermal adsorption *** with the geological properties of the potential reservoir,including coal seam development and hydrodynamic characteristics,the areas between Santun River and Sigong River in the Junggar Basin were found to be suitable for CO_(2)***,the coal-bearing strata from Santun River to Sigong River can be defined as“potentially favorable areas for CO_(2)eequetfraiion”To better guide the future field test of CO_(2)storage in these areas,three CO_(2)sequestration modes were defined:1)the broad syncline and faulted anticline mode;2)the monoclinic mode;3)the syncline and strike-slip fault mode.

关键词： CO_(2)geological sequestration coalbed methane low-rank coal coal reservoir Junggar Basin

A Contractive Sliding-mode MPC Algorithm for Nonlinear Discrete-time Systems

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International Journal of Automation and computing 2013年第2期10卷 167-172页

作者： meng zhao Bao-Cang Ding College of Automation Chongqing University

This paper investigates a sliding-mode model predictive control （MPC） algorithm with auxiliary contractive sliding vector constraint for constrained nonlinear discrete-time systems. By adding contractive constraint into the optimization problem in regular sliding-mode MPC algorithm, the value of the sliding vector is decreased to zero asymptotically, which means that the system state is driven into a vicinity of sliding surface with a certain width. Then, the system state moves along the sliding surface to the equilibrium point within the vicinity. By applying the proposed algorithm, the stability of the closed-loop system is guaranteed. A numerical example of a continuous stirred tank reactor （CSTR） system is given to verify the feasibility and effectiveness of the proposed method.

关键词： Model predictive control (MPC) sliding mode contractive constraint discrete-time systems nonlinear systems

Reservoir Characteristics and Controlling Factors of the Metamorphic Buried Hill of Bozhong Sag, Bohai Bay Basin

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Journal of Earth Science 2021年第4期32卷 919-926页

作者： Yong’an Xue meng zhao Xiaojian Liu China National Offshore Oil Corporation Tianjin BranchTianjin 300459China

The burial depth of the metamorphic buried hill of the Bozhong sag is more than 4500 m,however,the controlling factors of the reservoirs are not *** on cores and sidewall cores obtained from 15 wells,this paper describes the reservoir characteristics and discussed their controlling *** metamorphic basement of the Bozhong sag consists of metamorphic granite,migmatitic granite and *** felsic rocks are more likely to develop fractures,thereby improving the reservoir *** Indosinian,Yanshanian and Himalayan tectonic events greatly reformed the Bozhong 19-6 metamorphic buried hill,forming a large scale fracture *** and deep thermal fluid contributed to the development of dissolved pores of the *** general,controlled by lithology,tectonics,weathering and deep thermal fluid,the reservoir pattern of the metamorphic buried hill of the Bozhong 19-6 structure was established.

关键词： metamorphic rocks buried hill Bozhong sag Bohai Bay Basin

Empirical Likelihood Inference for Functional Coefficient ARCH-M Model

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Acta Mathematica Sinica,English Series 2019年第2期35卷 270-296页

作者： Hai Qing zhao Yuan LI Yan meng zhao School of Mathematics and Information Science Guangzhou University School of Mathematics and Statistics Lingnan Normal University School of Economics and Statistics Guangzhou University School of Mathematics and Statistics Shenzhen University

Empirical likelihood inference for parametric and nonparametric parts in functional coefficient ARCH-M models is investigated in this paper. Firstly, the kernel smoothing technique is used to estimate coefficient function δ(x). In this way we obtain an estimated function with parameter β.Secondly, the empirical likelihood method is developed to estimate the parameter β. An estimated empirical log-likelohood ratio is proved to be asymptotically standard chi-squred, and the maximum empirical likelihood estimation(MELE) for β is shown to be asymptotically normal. Finally, based on the MELE of β, the empirical likelihood approach is again applied to reestimate the nonparametric part δ(x). The empirical log-likelohood ratio for δ(x) is proved to be also asymptotically standard chi-squred. Simulation study shows that the proposed method works better than the normal approximation method in terms of average areas of confidence regions for β, and the empirical likelihood confidence belt for δ(x) performs well.

关键词： ARCH-M model empirical likelihood relative risk aversion